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FEBRUARY 2013 LEDsmagazine.com

Light engines Modular SSL approach P.49

Color science Optimizing color rendering P.57 TECHNOLOGY AND APPLICATIONS OF LIGHT EMITTING DIODES

Manufacturing Large LED substrates P.63

LED LAMPS Lighting manufacturers take myriad approaches P.33

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ISSUE 58

february

Cover Story

2013

While incandescent lamps maintained the same basic look over more than a century, SSL retrofit lamp manufacturers have adopted vastly different architectures in an attempt to get the LED point light sources to deliver an omnidirectional beam (see page 33).

features 33 RETROFIT LAMPS Maury Wright

Varying approaches to LED retrofit lamps show no limit

40 LUMINAIRE DESIGN Tim Whitaker

MHA Lighting takes unique approach to LED fixture design with Rods with Holes technology

columns/departments 4

45 STANDARDS Jianzhong Jiao, Osram Opto Semiconductors

ANSI works to standardize LED datasheet for white LEDs

49 FOCUS ON Skyler Frink & Maury Wright SSL modules

57 COLOR SCIENCE George Kelly, Avnet

Understand color science to maximize success with LEDs – part 4

COMMENTARY Maury Wright Complex color science underlies good SSL products NEWS +ANALYSIS Lynk Labs LED light engine dims to warm Toshiba announces GaNon-Si LED production start Konica Minolta buys Instrument Systems Philips Lumileds announces workhorse Luxeon T family Siemens plans Osram spinoff

MANUFACTURING Marcus Weddle, ARC Energy Manufacturing LEDs on large diameter substrates: What’s the holdup?

69 FINANCING Darren Riva, EEF

Energy Efficiency Financing scheme lights up the path to green savings

72 DESIGN FORUM Fred Sawyer & Mladen Ivankovic, Infineon Fixed-frequency and quasi-resonant flyback controllers drive large LED strings

76 LAST WORD Menno Treffers, Zhaga Consortium

Zhaga helps SSL luminaire makers reduce costs and supply-chain risks

LEDsmagazine.com

Cree announces LEDs for directional applications Philips introduces LED linear and spotlight module

25 FUNDING+PROGRAMS

Digital Lumens closes $10 million round of investment to support continued expansion Rubicon Technology closes $25 million secured revolving credit facility SEMI publishes HB-LED standard relating to sapphire substrates DOE publishes new Caliper reports and year in review for the program

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commentary

Complex color science underlies good SSL products

EDITOR Maury Wright

mauryw@pennwell.com ASSOCIATE EDITOR Nicole Pelletier

nicolep@pennwell.com ASSISTANT EDITOR Skyler Frink

skylerf@pennwell.com CONTRIBUTING Tim Whitaker EDITOR twhitaker@pennwell.com MARKETING MANAGER Jennifer Landry PRESENTATION MANAGER Kelli Mylchreest PRODUCTION DIRECTOR Mari Rodriguez

olor science is an incredibly complex topic. I must say that I underestimated the importance of color science in terms of the ability of LED manufacturers and solid-state lighting (SSL) lamp and luminaire manufacturers to deliver high-quality products. I’m nearing the end of three years covering the LED and lighting space, but still learning something new every day. And I’d highly recommend that you peruse the fourth installment in our color science series in this issue (p. 57). Indeed, if you haven’t been following the series, you might go back and read the entire series even if you started a prior one and decided the topic was just too complex. The article in this issue includes web links to each of the prior articles. George Kelly, who manages Avnet’s Light Lab, has done an excellent job on the series. I’ll concede that I found the first couple of articles very technical and difficult to understand. And many of us will never use the math described. But the end of the third article and the one in this issue brought the theory into the light of real product design. It turns out that it’s really important to understand why two light sources that are metamers of one another — they have the same effect on the eye even though the spectral power distribution may be vastly different — won’t necessarily render colors equally well. The light reflected from an object that’s illuminated by the two different sources will not be metamers of one another. It’s that ref lected light and the eye response that matters. And in the SSL industry we face confl icting goals of delivering high efficacy, excellent color rendering, and warm color temperature. The article in this issue covers approaches to that task.

SENIOR VICE PRESIDENT Christine Shaw & PUBLISHING DIRECTOR cshaw@pennwell.com

FEBRUARY 2013

I sure hope to convince George to write one more article in the series, bringing even more practical examples to light. Meanwhile, he has agreed to do a Webcast on February 21 on the topic. You can register at www.ledsmagazine.com/webcasts or view the archive if you read this column after the live event. The rest of this issue covers topics ranging from LED manufacturing to new packaged LEDs to driver design to standards to retrofit lamps. The News+Views section (p. 9) includes a number of items related to the latest in LEDs, including the move by Toshiba to a gallium-nitride-on-silicon (GaN-on-Si) manufacturing process. We also have new components from Cree, Philips Lumileds, and Bridgelux. Retrofit lamps are among the most popular topics that we cover with you the reader. That fact led to our choice of cover photo, and to the feature article on the topic (p. 33). Modular light engines are becoming increasingly popular in SSL product design, whether the module is a proprietary design or based on an industry standard such as Zhaga. You will fi nd modular coverage in News+Views, in the Focus On feature (p. 49), and in the Last Word column (p. 76) that was written by Zhaga General Secretary Menno Treffers. Treffers will also have presented a Webcast on Zhaga’s progress by the time you read this, but you can view the archive at the prior Webcast link if you have missed it. Please enjoy the issue. And I look forward to seeing you at Strategies in Light. Come by our booth and say hello.

Maury Wright, EDITOR

mauryw@pennwell.com

SENIOR ILLUSTRATOR Christopher Hipp AUDIENCE DEVELOPMENT Debbie Bouley

EDITORIAL OFFICES PennWell Corporation,

LEDs Magazine 98 Spit Brook Road, LL-1 Nashua, NH 03062-5737 Tel: +1 603 891-0123 Fax: +1 603 891-0574 www.ledsmagazine.com SALES OFFICES SALES MANAGER Bob Collopy (US EAST COAST) bobc@pennwell.com

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Tel: +82 2 2273 4818 CORPORATE OFFICERS CHAIRMAN Frank T. Lauinger PRESIDENT AND CEO Robert F. Biolchini CHIEF FINANCIAL OFFICER Mark C. Wilmoth TECHNOLOGY GROUP SENIOR VICE PRESIDENT Christine A. Shaw & PUBLISHING DIRECTOR SUBSCRIPTIONS: For subscription inquiries:

Tel: +1 847 559-7330; Fax: +1 847 291-4816; e-mail: led@omeda.com; ledsmagazine.com/subscribe We make portions of our subscriber list available to carefully screened companies that offer products and services that may be important for your work. If you do not want to receive those offers and/or information via direct mail, please let us know by contacting us at List Services LEDs, 98 Spit Brook Road LL-1, Nashua, NH 03062. Copyright © 2013 PennWell Corp (ISSN 2156-633X). All rights reserved. Contents of this publication may not be reproduced in any form without prior written consent of Publishers.

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FEATURED

| online Webcast

event

LED China March 1-4, 2013 Guangzhou, China

LRC 25th Anniversary

Understanding how Zhaga Books enable a modular approach to SSL product design http://ledsmagazine.com/features/9/12/10

The Nector S Power System - The Intelligence in Luminaire Design

March 20, 2013 Troy, NY

Lightfair International April 23-25, 2013 Philadelphia, PA

China Lighting Expo April 25-27, 2013 Beijing, China

http://ledsmagazine.com/features/10/1/1

Singapore International LED/OLED Technology Show

Whitepaper

May 7-9, 2013 Singapore

Power LED Electrical, Thermal and Optical Characterization http://ledsmagazine.com/whitepapers/28/

LED Expo Thailand May 23-25, 2013 Bangkok, Thailand

SPARC International Lighting

Thermal Simulation Simplifies LED Luminaire Development http://ledsmagazine.com/whitepapers/27/

June 3-5, 2013 Sydney, Australia

The LED Show August 13-15, 2013 Las Vegas, NV

Thermal Simulation and Characterization Optimizes LEDs for Automotive Applications

LED Japan Conference & Expo/ Strategies in Light

http://ledsmagazine.com/whitepapers/26/

October 16-18, 2013 Yokohama, Japan

MORE: www.ledsmagazine.com/events

ADVERTISERS

index

Alpha ..................................................... 47 American Bright Optoelectronics............. 14 Bayer Material Science, LLC ................... 53 Cirrus Logic ............................................ 24 Cree Inc. .............................................. CV4 CSA International ................................... 13 EBM-Papst Inc. ........................................ 7 Edison Opto Corporation ........................ 23 Epistar ..................................................... 1 ERG ....................................................... 70 Future Electronics Inc. ............................ 32 GKN Sinter Metals ................................. 70 Global Lighting Technologies .................. 37 Hangzhou Najing Technology Co. Ltd. ..... 12 Indice Ecotech ....................................... 61 Indium Corporation of America ............... 21 Instruments Systems GmbH................... 11

FEBRUARY 2013

Inventronics (Hangzhou) Inc.................... 15 Konica Minolta Sensing Americas........... 71 Lambda Research Corporation ............... 16 Lauren Manufacturing ............................ 38 Ledlink Optics Inc................................... 19 Lightfair International ............................. 48 Matrix Lighting Limited, Hong Kong....... CV2 MBN GmbH............................................ 17 Metal Coaters ............................ 27, 29, 31 NMB Technologies Corporation............... 55 Optronic Laboratories Inc. ...................... 46 Orb Optronix........................................... 52 Philips Lumileds ....................................... 2 Proto Labs Inc. ....................................... 39 Recom Power Inc. ............................ 73, 75 Roal Electronics USA Inc. ....................... 71 Seoul Semiconductor ............................. 30

Shanxi Guangyu LED ............................. 18 Lighting Co. Ltd. Shat-R-Shields ....................................... 42 Shenzhen Baikang Optical Co. Ltd. ............. 5 Shenzhen Refond ............................ 28 Optoelectronics Co. Ltd. Sichuan Jiuzhou Electric ........................ 43 Group Co. Ltd. Signcomplex Limited .............................. 67 TE Connectivity ...................................... 44 The Bergquist Company ........................... 8 Thomas Research Products.................... 68 Topco Green Synergy Group ................... 51 Underwriters Laboratories ...................... 35 Unilumin Group Co. Ltd........................... 20 Verde Designs........................................ 71

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the spotlight shines on efﬁciency

Thermal management is a key factor that limits the lumen output and efficiency of an LED lightsource. While as much as 80 percent more energy efficient than traditional incandescent lighting, the LED components still create a considerable amount of heat. If this heat is not dissipated properly, the quality of light and life expectancy of the LED lightsource decreases dramatically. In order to reach the desired lumen values in a small form factor, active cooling may be required to effectively dissipate the heat produced by the LED components. Active cooling technology offers thermal capabilities that are superior to passive heat sinks and can raise performance while reducing the size of the lighting fixture. With inaudible noise performance and industry-leading German engineered reliability, ebm-papst can provide the perfect solution for your LED cooling problems

info.ebmpapst.us/ActiveCooling To ﬁnd out more about custom Active Cooling Solutions, visit ________________________ or speak with an application engineer at (860) 674-1515

the engineer’s choice

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NEW T-CLAD PA STICKS IT TO HEAT. ®

Peel and place thermal solution withstands the heat of solder reflow. Easier assembly, cooler LEDs. Bergquist’s T-Clad with pre-applied Bond-Ply ®450 allows you to adhere your mounted LEDs to a variety of heatsinks and surfaces while thermally optimizing your application.This version of peel and place T-Clad can withstand the high temperatures of solder reflow during

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Thermal Materials

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Thermal Substrates

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Fans and Blowers

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news

views LED MODULE

Lynk Labs LED light engine dims to warm Lynk Labs has announced a new chip-on-board (COB) module in its SnapBrite family of products that for the first time relies on mid-power LEDs combined with AC-driver circuitry. The 114-mm-diameter SR114 solid-state lighting (SSL) module accepts 120-VAC input direct from the power line and delivers 2000 lm at an operating temperature of 65°C. The new module achieves 100-lm/W efficacy based on the mid-power LEDs used and the efficiency of AC-drive technology that eliminates a power conversion stage relative to more typical DC-driven LEDs. “The 100 lm/w result includes all the required drive and protection circuitry to run the module direct from the mains,” said Chick Huber, vice president of business development at Lynk Labs. The SR114 is the fi rst of a number of products that will use the general design captured in the new module. Th is first product features a 3800K CCT and CRI of 83, and when dimmed, using a legacy triac or phase-cut dimmer, delivers a warmer color temperature mimicking an incandescent lamp. CEO Mike Miskin said that the company has a number of options in how to implement the dim-to-warm technology including using some amber or red LEDs. This first design, however utilizes two channels. One channel uses 4000K LEDs and the second uses very warm 2200K LEDs.

At full brightness, the 4000K LEDs deliver the bulk of the light and the enhanced efficacy that’s common in highercolor-temperature LEDs. As the product is dimmed to lower drive currents, energy usage is generally decreased and the warm-CCT LEDs contribute more of the light mix. The module delivers a 120° beam pattern that enables its use in applications such as downlights, flush-mount fixtures, and ceiling fans. Miskin said, “Now that we have reached 100lm/w plug top efficiency with incandescent quality dimming, AC LEDs can fill the need for cost-sensitive, form-factor-challenged lighting applications with high system efficiency.” The initially available SR114 uses Epistar mid-power LEDs. At press time the LEDs had not been fully LM-80 qualified. Miskin said, however, that such tests are ongoing and that the qualification should be in place around mid-February. He also added that based on customer requirements, Lynk Labs can utilize a variety of LED types to meet specific application needs. ◀ MORE: www.ledsmagazine.com/news/10/1/10

SILICON LEDS

Toshiba announces GaN-on-Si LED production start Toshiba announced in December that it began producing white LEDs on 200-mm (8-in) silicon substrates. The TL1F1 1W gallium-onsilicon (GaN-on-Si) LED is the fi rst product and will deliver a maximum of 112 lm at 350mA drive current. The combination of larger wafers and access to automated back-end manufacturing tools in depreciated IC fabs has the potential of lowering the cost of LEDs and accelerating SSL deployment, although obstacles remain in reaching the optical efficiency of sapphire-based LEDs. Subsequent to the announcement of production start, Toshiba posted data sheets that reveal that the GaN-on-Si LEDs will initially come in a choice of 3000K, 4000K, 5000K CCTs (www.leds_______

LEDsmagazine.com

magazine.com/news/10/1/3.) The 5000K coolwhite LED comes in 70 and 80 CRI, and the 70-CRI TL1F1-NW0 offers the top efficacy spec mentioned previously. Both the 4000K TL1F1WH1,L and 3000K TL1F1-LW1,L deliver 84 lm/W. And both offer a CRI of 80. The efficacy figures don’t match the latest sapphire-based LEDs. For comparison, Cree announced the new XM-L2 LED family recently that is similar in size (p. 12). The Cree LED measures 5×5 mm while the Toshiba LED measures 6.4×5 mm. Cree said the XM-L2 LED can deliver 186 lm/W in cool white at 350-mA drive current. But if the Toshiba LEDs deliver the anticipated reduction » page 10 in costs, the products could do very well.

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news+views Toshiba from page 9

We’ve been expecting more news from the GaN-on-Si players throughout the fall. Azzurro Semiconductors has been attacking the problem building template wafers that have the base GaN layer applied, upon which LED companies can then build their own LED structures. That company has been linked to both Osram Opto Semiconductors (www.leds_______ magazine.com/news/9/1/19) and Epistar _________________ (www.ledsmagazine.com/news/9/10/9). Partners Lattice Power from China and Plessey Semiconductors from the UK are also working on the technology (www. ____ ledsmagazine.com/news/9/6/12). Lattice had claimed that it was in production of such devices back in the summer, but SSL products using such LEDs haven’t been in evidence. ◀ MORE: www.ledsmagazine.com/news/9/12/18

BUSINESS

Konica Minolta buys Instrument Systems Instrument Systems GmbH, one of the LED industry’s best-known light-measurement companies, has been acquired by Konica Minolta Optics, Inc., effective December 1. Instrument Systems was founded in 1986 by its president, Richard Distl, and is based in Munich, Germany. The company supplies a comprehensive range of light measuring products for industrial and research applications. Key applications are LED and display measurement, as well as spectroradiometry and photometry. The subsidiary company Optronik Berlin GmbH is also included in the sale. Instrument Systems has posted very strong growth in recent years, and its 2011/12 financial year, which closed in June 2012, produced the best results since the company was founded. Combined sales with the Optronik Berlin subsidiary rose by 27% to EUR 30.3 million ($39.6 million), up from EUR 23.9 million in the year ended June 2011. Konica Minolta Optics was interested in Instrument Systems reputation in the LED field. Toshihiko Karasaki, president of Konica Minolta Optics, said: “Our goal is to have a leading global position in all our corporate

FEBRUARY 2013

divisions and to integrate international talent within our group. Instrument Systems is the best company in LED lighting measurement to consistently implement this strategy.” The acquisition of Instrument Systems came several weeks after CSA Group acquired LED testing company Orb Optronix (www.ledsmagazine.com/news/9/11/12). ◀ MORE: www.ledsmagazine.com/news/9/12/6

PACKAGED LEDS

Philips Lumileds announces workhorse Luxeon T family Philips Lumileds has introduced the new Luxeon T series of high-power LEDs that target SSL applications with directional-beam requirements including downlights, and MR16 and PAR retrofit lamps. The LEDs set new efficacy milestones for Lumileds achieving 140 lm/W at 350 mA of drive current. Lumileds CEO Pierre Yves Lesaicherre emphasized that Lumileds considers the Luxeon T much more than an evolution of the Lumileds family saying, “The Luxeon T is going to be the workhorse in terms of high efficacy.” Clearly Lumileds expects Luxeon T to be the product of choice for applications in which the LED is expected to produce maximum forward light. Lumileds claims several breakthroughs for the new series beyond efficacy, including what it says is an industry-lowest 2.7V forward voltage and 3°C/W thermal resistance. Product line director Kathleen Hartnett said that only one other LED maker has reached 2.8V and that most are at 3V or above. The lower forward voltage simplifies the thermal design – especially critical in space-constrained directional lamps such as MR16 retrofits. Lumileds will offer the LEDs in 3-step MacAdam ellipse bins, tested at 85°C. Lesaicherre said that the company is not matching phosphor tiles with emitters the way it did in the original Rebel Lumiramicbased LEDs to reach the tight binning, but instead controlling the epitaxial (epi) process more tightly. “We’ve narrowed the epi distribution to 1 to 2 bins,” said Lesaicherre . Indeed, better process control is behind both the binning and the lower forward voltage. Lesaicherre said, “The conversion to 6-in substrates has really helped because we have

more modern equipment.” Specifically, he said they have tighter control of temperature and gas distribution in the epi process. The LED package measures 3.7×3.7 mm. The prior Luxeon A product targeted similar applications but features a rectangular package. The new LEDs offer a minimum CRI of 80, and optionally a CRI of 95, across the full range of CCTs, including 2700K, 3000K, 3500K, 4000K, and 5000K.

Lime-green LED Lesaicherre also commented on the mysterious lime-green LED that is presumably very important to the function of the Philips Lighting color-changing Hue lamp (www.ledsmagazine.com/news/9/10/25). Lesaicherre was guarded with details but said that Lumileds had advanced the efficacy of green LEDs that in general has trailed other colored LEDs industry wide. The Hue lamp uses five of the lime-green LEDs, four red LEDs, and 2 blue LEDs. That means that the green LED is approaching the efficacy of the red ones. The limegreen color itself was not the source of the efficacy gain. Instead, that lime-green LED better enables the mixture to deliver the full color-tunable range according to Lumileds’ Hartnett. Lumileds does plan to offer a limegreen LED commercially, but is still mulling over plans as to which Luxeon family in which it will launch the product. ◀ MORE: www.ledsmagazine.com/news/9/12/7

BUSINESS

Siemens plans Osram spinoff After shelving its plans for an initial public offering (IPO) of Osram, its lighting subsidiary, Siemens has confi rmed that it will conduct a spinoff of 80.5% of Osram’s shares (www.ledsmagazine.com/news/9/11/22). A plan to conduct the IPO of Osram shares was LEDsmagazine.com

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We bring quality to light.

Putting LEDs in the right light. SSL solutions from the world leader in LED measurement Instrument Systems set the benchmark in LED testing with high-performance spectroradiometers for photometric and colorimetric measurements. Now we present another breakthrough in SolidState Lighting with our new goniophotometers and integrating spheres. NEW: LGS 250 Goniophotometer

Find out more about our innovations for SSL : www.instrumentsystems.com/ssl

light measurement Instrument Systems Germany · Phone: +49 89 45 49 43 0 · ssl@instrumentsystems.com · www.instrumentsystems.com

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news+views finally shelved in July of 2012. The transaction will result in Siemens’ shareholders receiving one Osram share for every ten Siemens shares. However, Siemens still intends to retain a minority stake in Osram, in which it wants to remain “a longterm anchor shareholder.” To this end, Siemens AG will retain a 17% stake in Osram following the spinoff, with the Siemens Pension Trust holding the remaining 2.5%. Implementation of the spinoff plans will require the approval of at least three-quarters of existing shareholders. The decision will be made at the Annual Shareholders’ Meeting scheduled for January 23, 2013, after we went to press. The Osram IPO (www. ____ ledsmagazine.com/news/8/3/30) was fi rst announced in March 2011, and scheduled for fall 2011. But, as we reported in August 2011, Siemens delayed its Osram IPO plan (www.ledsmagazine.com/news/8/8/28) due to adverse market conditions. Subsequent to the announcement of the spinoff. Osram offered some insight on its

plans to both cut cost and invest in SSL. The SSL segment is seen as a key one. At Strategies in Light Europe 2012, Osram’s Christian Schraft said that the company’s revenue for fiscal 2011 (ended September 30, 2011) was around EUR 5 billion, of which around 25% was from SSL. Osram will invest in production facilities such as an LED assembly plant in China, while at the same time selling other plants that make products using older lighting technologies. Meanwhile the corporate reorganization program will result in the loss of an additional 4700 Osram jobs by 2014 on top of the 1900 jobs cut worldwide in fiscal 2012. Most of the cuts that will be implemented both in Germany and internationally are aimed at production facilities with products at the end of their product life cycle, or the closure of smaller plants with lower sales. The company plans to invest “a low threedigit million euro figure” over the coming years in the assembly plant located in the Chinese province of Jiangsu. Th is plant is

in its fi nal completion stage, and its 1700 employees will manufacture products for key segments of the Chinese market and the entire Asia region. In five years’ time, Osram expects this region to account for around half of the global general-lighting market. Wolfgang Dehen, CEO of Osram Licht AG, pointed out that the reduction in staff is a natural consequence of switching to newer lighting technologies, particularly LEDs. “Compared to traditional products, the depth of our added value in LED-based products will be significantly reduced. Consequently, the personnel increase in the future fields will only partially compensate for the change in the traditional business,” he said. ◀ MORE: www.ledsmagazine.com/news/9/12/2

PACKAGED LEDS

Cree announces LEDs for directional applications Cree recently announced the XLamp MK-R packaged LED that integrates four die, and

_________

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' ! & # (

! ( ) * (

!" ® # ! $ #% & Third-party certification and verification are now ENERGY STAR requirements. CSA Group has earned EPA recognition as an ENERGY STAR Testing Facility and Certification Body. That means today we can meet all of your lighting product safety and energy efficiency testing needs with a single, seamlessly efficient testing program that saves you time and money. Look to CSA Group to meet ENERGY STAR requirements for lighting products including:

If you prefer to perform testing using your own testing laboratory, we can qualify your lab facilities under our Testing Laboratory program, then verify your test results and submit them to the EPA. Contact us today and learn how much time and money a combined safety and energy efﬁciency testing program with CSA Group can save you.

1-866-463-1785 cert.sales@csagroup.org

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news+views the XM-L2 single-die LED – both for directional applications. The MK-R measures 7×7 mm and fits between the 5×5-mm XM-L family and the 9×9-mm MT-G family. The 5×5-mm XM-L2 is a follow on of the original single-die XM-L LEDs and Cree says that it’s the brightest single-die packaged LED on the market The new MK-R LEDs deliver as much as 1600 lm at 15W in a 5000K CCT – matching the light output of many larger chipon-board (COB) LED arrays for SSL retrofit lamps and luminaires (www.ledsmagazine. com/news/9/12/22). “The light output is more in line with what you see from a COB array,” said Cree product marketing manager Paul Scheidt. In terms of efficacy, Cree is touting the MK-R for reaching the 200 lm/W level. Cree says that the product is the follow-on commercial product to the laboratory 200lm/W efficacy achievement announced in February of 2010 (www.ledsmagazine.com/ news/7/2/7). “It’s amazing that Cree is able _______

to achieve a 200 lm/W LED so quickly,” said Nicola Vendrame, CEO of Linea Light group. “The high efficacy of the MK-R LED means

that we can drive the LED harder for more light output without creating heat issues.” Realistically, however, the LEDs will be applied at much lower efficacy levels due to higher drive current and in many instances warmer CCTs. For example, at

3000K CCT, 80 CRI, 700-mA drive current, and 85°C junction temperature, the MK-R delivers 865 lm at 106 lm/W. And many designs may drive the LEDs even harder. The sing le-d ie XM-L2 LED, meanwhile, maxes out at 1198 lm at 3A of drive current, and can deliver 186 lm/W efficacy at a lower drive current. The second-generation design targets directional SSL applications ranging from retrofits for directional halogen lamps to street lights. A number of Cree LEDs share the XM-L moniker that is representative of the package itself. The company offers both high-voltage and multi-emitter LEDs in the overall XM-L family. The new XM-L2 is a follow on to

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LEDsmagazine.com

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news+views the single die XM-L announced in late 2010 (www.ledsmagazine.com/news/7/11/12). Cree has announced several such second-generation LEDs this year that all offer SSL product developers the option to redesign a product using fewer LEDs, or boost the performance of a product using the same number of LEDs. Moreover, second-generation LEDs only require 3000 hours of LM-80 testing for SSL products that use the components to become Energy Star recognized. The second generation XM-L2 offers 10% greater lumen output at a 5700K CCT and 17% better lumen output at 3000K. The products are binned at 85°C and 700-mA drive current, and at 3000K deliver 224 lm and 112 lm/W. Cree emphasized that it’s both the singledie design and the performance that enables SSL designers to break new ground. Cree’s Scheidt said “You can do a 50W MR16 with just a single LED.” Scheidt compared such a theoretical MR16 with what he characterized as the best performing MR16 SSL lamps on the market for replacing 50W halogen

lamps. The comparison lamps delivered 390525 lm using 7-10W of power. The theoretical Cree design would deliver 369 lm at 5W. While the lumen output is lower for the theoretical lamp, the beam angle is a tight 9° whereas the other lamps range from 15-25°. The Cree lamp would deliver CBCP of 7800 cd – more than double the other lamps on the market. Scheidt said, “Because it’s a single die, it’s much more efficient at turning lumens to candela.” The system efficacy on the theoretical lamp is 75 lm/W. ◀ MORE: www.ledsmagazine.com/news/9/12/14

LIGHT ENGINES

Philips introduces LED linear and spotlight modules Philips Lighting has launched a third-generation LED-based Fortimo Linear Light Module (LLM) that targets applications such as outdoor lighting including roadway applications. Philips also announced a new generation of the Fortimo Spotlight Module (SLM) utilizing

COB LED technology. The new LED LLM Gen 3 family is available in a choice of four lumen-output packages – 1100, 1800, 3000, and 4500 lm. Philips also offers a choice of 3000K or 4000K CCT, and a CRI greater than 70. The LED SLM Gen 3 includes 2000- and 3000-lm versions with a CRI of 90 and high R9 value for applications such as retail. Philips, is stressing the vertical illuminance of the LLM products. Increasingly vertical illuminance is proving more important than horizontal illuminance in outdoor applications – especially where detection of pedestrians is important. There is a discussion of that issue in an article on the Street & Area Lighting Conference that was in the Fall

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issue of our sister publication Illumination in Focus (www. illuminationinfocus.com/features/3/11/4). “The Fortimo LED LLM provides excellent vertical illumination for optimal facial recognition, enhancing that feeling of safety,” said Marina Kishkovich, product manager outdoor LED lighting for Philips OEM EMEA. “Municipalities understand that today’s LED lighting technology not only delivers fantastic energy savings but also dramatically improves the quality of life for residents. LEDs provide clear white light, which has been proven to improve both perceived and actual safety and comfort in residential and urban lighting.” Moreover, SSL product developers can now combine an LLM with a Xitanium driver and achieve Constant Light Output

(CLO) functionality to combat lumen depreciation over time and save energy. Invariably lighting designers and specifiers choose a product with a lumen-output specification that will meet the required light level years in the future – accounting in the specification process for expected lumen depreciation. The Philips Gen 3 product simply drives the LEDs at lower current levels early in the product life and over time driver gradually increases drive current. ◀ PACKAGED LEDS

Bridgelux introduces Vero LED array Livermore, CA-based Bridgelux has unveiled the Vero LED array family, which offers “new advancements in design flexibility, ease of use, and energy efficiency,” says the company. Vero is also intended to be a platform that will enable future integration opportunities for smart sensors and wireless communication technology.

Compared with existing Bridgelux LED arrays, the Vero family offers an increase in efficacy by up to 20%, a higher flux density, and a simplified assembly process that streamlines manufacturing and improves overall system reliability. The Vero platform will be available in four form factors with performance ranging from 800 lm in warm white (3000K) up to 20,000 lm in cool white (5000K). There will be multiple CCT and CRI options, including the 97 CRI Decor product option. The Vero platform is currently being evaluated by Bridgelux customers and will be broadly commercially available in the first quarter of 2013. The company says that with the new Vero platform, more of the manufacturing process – building the COB arrays and combining them with the molded-plastic component – is automated. The array-body configuration also makes it easier to add functionality in the future, for example smart sensors or wireless-communication chips. “The Vero product is manufactured using highly automated processes to reduce cost,

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news+views and can be easily upgraded for the smart applications of the future,” said Jim Miller, chief sales and marketing officer of Bridgelux. “The Vero array offers our customers the manufacturing and design capabilities they need to open up new design possibilities, while ultimately driving faster adoption of LED lighting.” ◀ MORE: www.ledsmagazine.com/news/9/12/8

DISTRIBUTION

Future Electronics and Philips Lumileds restructure agreement The long-standing distribution agreement between Future Lighting Solutions (FLS) and Philips Lumileds, which kept Philips exclusive to FLS and had FLS sell Philips’ LEDs exclusively, has been restructured, enabling Philips to sell its LED products through other partners, and FLS to distribute other suppliers’ SSL products. Unlike other LED manufacturers, such as Osram Opto Semiconductors and Cree, Phil-

ips has always sold exclusively through FLS. The other supplier that sticks out from the crowd is Nichia, the largest manufacturer of packaged LEDs according to Strategies Unlimited, who only sells directly through their own network and does not use any distributors. The exclusive distribution agreement was intended to last for another four years, with a new five-year exclusive agreement being signed in 2011 (www.ledsmagazine.com/ press/31644). However, the companies have ________ decided to expand into new markets, and have determined the best way to do that is to restructure the deal. “Our restructured agreement allows us to continue our collaboration with a long-term, trusted and successful partner. With the new agreement, we are able to serve the needs of our growing customer base and carry on our widespread expansion into new target markets,” said Pierre-Yves Lesaicherre, CEO Philips Lumileds. FLS, meanwhile wasted little time in add-

ing another LED manufacturer to its line card. The distributor and LG Innotek have signed a worldwide distribution agreement through which FLS will sell LG Innotek’s entire portfolio of LED lighting products, ranging from packaged LEDs to integrated solutions. “We are excited about LG Innotek’s exceptionally strong portfolio of LED products, aggressive technology road map, and unparalleled quality manufacturing capabilities for the general illumination market,” said Gerry Duggan, executive vice president of Future Electronics. “Th is will further strengthen our proficiency in serving our customers’ growing demand for bestin-class LED lighting solutions.” ◀ MORE: www.ledsmagazine.com/press/37244

LICENSING

Solais Lighting licenses ByteLight technology ByteLight has signed a partnership agreement with Solais Lighting as its inaugural

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news+views licensed lighting partner. This means Solais Lighting is now licensed to manufacture and sell ByteLight-enabled LED lamps. ByteLight-enabled lamps from Solais Lighting will serve as lights and positioning beacons by transmitting proprietary signals that can be picked up by camera-equipped mobile devices carried by customers, visitors, and workers within venues (www.leds______ magazine.com/news/9/10/12). When signals are detected, each mobile device can calculate its position without the need for an active network connection. This enables venue owners to deliver local content, interactive maps, and indoor navigation features to users based on their location inside the venue. ◀ MORE: www.ledsmagazine.com/press/37248

BUSINESS

GE Lighting acquires Albeo Technology GE Lighting has signed an agreement to acquire Albeo Technologies, an LED fi xture

manufacturer based in Boulder, Colorado. GE Lighting officials say the acquisition will help GE serve as an advisor to enterprise customers, as well as offer a more complete and integrated family of LED-based SSL products. Albeo Technologies was founded in 2004. “Some of our biggest customers told us they wanted a GE-quality solution for high bay,” notes Maryrose Sylvester, president and CEO of GE Lighting. “Th is acquisition accelerates our development of cuttingedge technologies that brings customers the energy-efficient solutions they need. That’s what customers get at the end of the day — a refi ned, highly modular and scalable platform that delivers the GE quality they’ve come to expect.” Albeo’s range of products includes high bay and low bay lighting fi xtures as well as linear, surface-mounted and under cabinet lighting. Albeo’s products have been recognized with 16 independently judged awards, including six from the US Department of

Energy (DOE). ◀ MORE: www.ledsmagazine.com/news/9/11/18

FINANCIALS

SemiLEDs reports first quarter results SemiLEDs, a manufacturer of LED chips and components, has announced its fi nancial results for the first quarter of fiscal year 2013. Revenue for the quarter was $6.2 million, an 8% decrease when compared to the $6.7 million of revenue in first quarter of fiscal 2012. “As more of our customers have qualified our EV products, the demand of our LED chips and LED components has increased,” said Trung Doan, Chairman and CEO of SemiLEDs. “We are seeing pockets of demand while the overall LED market is still weak; we continue to manage cost, inventory and spending with a focus on profitable LED sectors to achieve our positive cash flow goal.”

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news+views The company also announced improvements in its EV-LED family with efficacy hitting more than 130 lm/W for some products. The company said epi and chip process advances resulted in a 10% gain in luminous flux and an 8% decrease in forward voltage. ◀ MORE: www.ledsmagazine.com/press/37387

folio, Sensor Switch occupancy sensors and Lighting Control & Design system management software will allow for the creation of intelligent lighting systems that are simple to use while generating greater energy savings for our customers.,” said Vernon J. Nagel, chairman, president and chief executive officer of Acuity Brands. ◀

DRIVERS

MORE: www.ledsmagazine.com/press/37388

Cree announces compatibility program

EXECUTIVE MANAGEMENT

Cree has instituted a new Driver Compatibility Program (DCP) for its LEDbased modular light engines that allows luminaire designers freedom of a larger choice of drivers and Cree warranty coverage on the light engine. The DCP is initially applicable to the LMH2 SSL modules. Participating companies include AC Electronics, Code Mercenaries, Harvard Engineering, Inventronics, Lutron, NMB Technologies, Opulent Solutions, Phihong, Roal Electronics, Thomas Research Products, and Xenergi Limted. Cree plans to extend the program both to other modular products and more driver companies. The biggest benefit of the DCP is warranty centric. Previously, Cree limited its warranty coverage on modular products to luminaire designs that also utilized Cree drivers. The new program does include Cree drivers in the approved list. But the warranty coverage now applies equally to luminaires that use other drivers in the program. ◀ MORE: www.ledsmagazine.com/news/10/1/6

BUSINESS

Acuity acquires Adura Technologies Acuity Brands has acquired the assets of Adura Technologies, a developer of wireless controls and energy management tools. Terms of the acquisition were not disclosed, and the acquisition is not expected to materially impact Acuity Brands’ fi scal 2013 consolidated fi nancial performance. Adura, which was founded in 2005, has developed radio frequency mesh networking technology that enables light fi xtures to communicate with sensors, switches, and management software. The technology is based on the ZigBee wireless standard. “Adura’s simple to use wireless technology coupled with our broad luminaire portLEDsmagazine.com

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Lighting Science Group and Nualight appoint execs Lighting Science Group (LSG), an LED lighting manufacturer based in Satellite Beach, Florida, has appointed Jeremy Cage as CEO, effective January 2, 2013. Irelandbased LED lighting company Nualight, meanwhile, has appointed Per Langholz as its non-executive chairman. New LSG CEO Cage is a former senior executive with PepsiCo, Inc. Cage said that he intends to accelerate growth at LSG by “building on the company’s core competencies of excellence in innovation and strong and differentiated brand development.” Cage added that LSG will “focus on unleashing the science of light and sustainable technologies to markets ranging from major cities, commercial centers, factories and retailers in developed markets to entire cities and villages in developing and emerging markets. There is much to do, and I am eager to get started.” Nualight’s new chairman Langholz is the former president of Sylvania Lighting International, where he led the company to profitable operation and annual turnover of over EUR400 million. He has over 25 years of experience in the lighting industry. Langholz succeeds Eamonn Quinn of the Quinn family that founded the Superquinn grocery chain. Quinn will remain on the Nualight Group board. Quinn welcomed the new appointment, saying, “As we continue to grow globally and drive expansion into new market segments, Per Langholz’s experience will make a tremendous contribution.” The Nualight Group is a LED lighting technology specialist with a core focus on retail, and has pioneered LED lighting in the refrigerated cabinets of many leading grocery retail chains. The company has gone from startup status 5 years ago to

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news+views employing over 200 people in three locations worldwide. Nualight is funded by Climate Change Capital, ESB Novus Modus, 4th Level Ventures and the Quinn retail family. ◀ LIFE SCIENCE

Adaptive LED lighting improves aircraft cabin environment Chronobiologically-adaptive SSL scenarios in which the color and brightness of lighting is varied during long-distance overnight flights results in passengers that sleep better and are more alert upon arrival. Partners Osram, Bergische Universität Wuppertal, the Fraunhofer Institute for Building Physics, Airbus, and Diehl Aerospace reached the conclusion of improved wellbeing attributed to adaptive LED lighting after tests in a model aircraft cabin over a period of six days. The team found that at the start of an overnight flight that warm-white light helps

to stimulate melatonin production and increases passenger relaxation. Indeed, the warm lighting was noted to reduce the heart rate in the test subjects and yield “medically measureable improvement” in sleep patterns. The study further revealed that blue-rich cold light in the morning increased alertness. In part, the cooler light suppresses mel-

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atonin production. The result for passengers is better productivity or more enjoyment over the course of the arrival day after a long trip. Both psychological and physiological reactions were analyzed in the test subjects. The team used medical instruments to capture data such as heart rate and ECG measurements. That data was analyzed alongside assessments completed by the test subjects and by observers of the tests. The team believes that the work can be applied using intelligent SSL systems in aircraft to help minimize passenger jet lag by maintaining normal circadian rhythms. MORE: www.ledsmagazine.com/news/10/1/1

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funding programs Rubicon Technology closes $25 million secured revolving credit facility Rubicon Technology, Inc. (NASDAQ: RBCN), a leading provider of sapphire substrates and products to the LED, semiconductor,

William Weissman, chief financial officer of Rubicon Technology. “We believe it is prudent to establish this additional fi nancial

and optical industries, has closed a three year $25 million secured revolving credit facility with Silicon Valley Bank. “This undrawn credit facility bolsters Rubicon’s strong liquidity position,” said

flexibility for the future,” he concluded. Rubicon currently has no debt. The terms and conditions of the credit facility will be described in the company’s fi lings with the Securities and Exchange Commission. ◀

SEMI publishes HB-LED standard relating to sapphire substrates The HB-LED Standards Committee of SEMI, the global semiconductor industry association, has approved its first LED-related standard, entitled “SEMI HB1: Specifications for Sapphire Wafers Intended for Use for Manufacturing High Brightness-Light Emitting Diode Devices.” LEDsmagazine.com

Developed by the HB-LED Wafer Task Force, SEMI HB1 defi nes and specifies the physical geometry of 150-mm-diameter sapphire wafers used in HB-LED manufacturing. HB1 covers dimensional, wafer preparation, and crystallographic orientation » page 26 characteristics, as well as the

Digital Lumens closes $10 million round of investment to support continued expansion Digital Lumens rung in the New Year with 150% growth in its customer base and a further commitment from investors to support the company’s success in LED lighting. The company had more than 500 large-scale installations of its Intelligent LED Lighting System last year. Accord i ng to estimates by Canaccord Genuity in the "Third Cycle V2.2" the overall LED lighting market grew 94% from 2011 to 2012. Digital Lumens grew much faster than the overall market as customers deployed the Digital Lumens solution – oftentimes with multi-site roll-outs – based on the company’s growing reputation and demonstrated energy savings. As it prepared itself for more growth in 2013, the company has closed a $10 million round of funding from existing investors including Black Coral Capital, Flybridge Capital Partners, and Stata Venture Partners. “These impressive numbers are proof that the lighting market is moving rapidly to LED, and that Digital Lumens continues to set the standard for performance, efficiency, and value with our customers,” said Tom Pincince, President and CEO of Digital Lumens. “While we have established a leadership position in the industrial vertical, our integrated intelligence is applicable to the entire lighting market. We will use this latest investment to accelerate our expansion into new segments and international markets, and to further develop our product and service offerings.” ◀

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DOE Caliper report evaluates LED PAR38 lamps A recent Caliper report from the US Department of Energy (DOE), which is number 20 in the series, evaluates the independently-tested photometric performance of 38 LED PAR38 lamps. The Caliper program supports testing of a wide array of solid-state lighting (SSL) products available for general illumination. A summary of the series 20 results is available for download from the DOE SSL website. The series 20 results show significant improvement versus earlier Caliper testing of similar products. All of the LED PAR38 lamps tested offer substantial energy savings compared to halogen PAR38 lamps. Some of the LED lamps had higher efficacy than compact-fluorescent (CFL) or ceramic-metal-halide (CMH) versions. The lumen output of many of the products was equivalent to 40W to 90W halogen PAR38 lamps, and all emitted between 388 and 1363 lm. Efficacy of the LED lamps ranged from 26 to 79 lm/W, although all except one of the products was between 44 and 79 lm/W. Further, LED products are available that cover the full range of conventional PAR38 beam angles, and that have appropriate color quality, lumen output, and center beam intensity. The LED PAR38 lamps had luminous intensity distributions ranging from narrow (8° beam angle) to very wide (64° beam angle); the suitability of these distributions depends on the application, but the availability of narrow distributions is an important finding. In an improvement compared to earlier testing, 37 of the 38 products had a power factor higher than 0.70. However, more options within specific product families would be beneficial, and LED lamps with higher lumen output may be necessary for specialty applications. And, as usual, lower prices would also be beneficial to enhance the penetration of LED lamps into the market. Beginning in 2012, each Caliper summary report focuses on a single product type or application. Products are selected with the intent of capturing the current state of the market—a cross section ranging from expected low- to high-performing products—with the bulk characterizing the average of the range. ◀

FEBRUARY 2013

SEMI from page 25

appropriate measurement methods. The document was approved by the HBLED Committee during the North America Fall 2012 meetings, recently completed procedural review and was to be published in January 2013. Improving manufacturing efficiency and reducing cost are critical to enabling high-volume LED manufacturing, and 150-mm sapphire wafers represent a key inflection point. Five categories of single-crystal, singleside polished sapphire wafers are covered in HB1, including: flatted 100-mm diameter, 650-μm thick, polished c-axis sapphire wafers; flatted 150-mm diameter, 1000-μm thick, polished c-axis sapphire wafers; flatted 150-mm diameter, 1300-μm thick, polished c-axis sapphire wafers; notched 150mm diameter, 1000-μm thick, polished c-axis sapphire wafers; and notched 150-mm diameter, 1300-μm thick, polished c-axis sapphire wafers. SEMI believes that in order to reach the full potential of LEDs, there is a need for the global LED manufacturing supply chain to collaborate on industry standards to eliminate unnecessary costs, and better enable equipment and process innovation. With this in mind, key industry stakeholders created the SEMI HB-LED Standards Committee in late 2010. The Committee and Task Forces are comprised of industry leaders in HB-LED devices, sapphire wafers, MOCVD wafer processing, and key equipment and materials suppliers to the LED industry. Since formation, the HB-LED Committee has initiated Task Forces on wafers, carriers, assembly and automation. Committee co-chairs are: Iain Black (Philips Lumileds), Chris Moore (Semilab), David Reid (Silian), and Bill Quinn (WEQ). Ongoing activities include the following:

HB-LED Wafer Task Force (TF) The HB-LED Wafer TF is already developing a revision proposal for further refinements to the HB1 standard including: • patterned sapphire substrate (PSS)-ready specification for 100-mm and 150-mm wafers • double sided polished wafer specifications • definitions and specifications of impurities and defects (wafer and bulk)

• laser marking and identification specification • bow, warp measurements.

HB-LED Equipment Automation Task Force The Equipment Automation TF has developed draft document 5420A entitled “Specification for Cassettes for 150 mm Sapphire Wafers Used in HB-LED Manufacturing.” To minimize impact to the industry, the TF is leveraging existing 150-mm silicon cassette standards with minor revisions. Th is will allow interoperability with existing 150-mm equipment and any other 150mm compatible products. Considerations were taken around the cassette’s pocket size and spacing so that the sapphire wafers can be successfully transferred between cassettes with automated handling equipment. A cassette standard will also enable standardization of load ports and transport systems.

HB-LED Impurities & Defects Task Force The Impurities & Defects TF will begin experiments and test methods based on responses to a survey aimed at identifying sapphire wafer defects that are relevant or important to HB-LED manufacturing, as well as inspection techniques that can be applied to identify, measure, or prevent such defects.

Upcoming Meetings The HB-LED Wafer TF, Equipment Automation TF, and Impurities & Defects TF will be meeting in conjunction with the Strategies in Light conference (February 12-14, 2013) in Santa Clara, California.

Taiwan LED Safety Task Force The LED Safety Task Force was chartered in late 2011 under the Taiwan EHS (Environmental, Health, and Safety) Committee to develop specifications and guidelines related to LED manufacturing equipment. The activities of the task force will result in the development of an EHS industry standard for equipment suppliers, raw material suppliers, module makers and other involved parties. ◀ LEDsmagazine.com

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funding programs Next Generation Streetlights guide covers LED technology to financing The Bay Area Climate Collaborative, Energy Solutions, the California Lighting Technology Center, and Public Financial Management have partnered to produce a guidebook for municipalities considering a transition to SSL roadway lighting. "Next generation streetlights: LED technology and strategies for action" is a new guidebook intended to help municipalities

president at Energy Solutions. "Furthermore, advanced controls networks that tune light levels, communicate status and provide other features can generate additional energy and maintenance savings through smarter management of street-light systems." A number of SSL manufacturers and the Pacific Gas and Electric utility are also partners in the BACC-led Next Generation Street-

that are considering installation of LEDbased street lights. The Bay Area Climate Collaborative (BACC) and Energ y Solutions co-authored the solid-state lighting (SSL) guide with assistance from the California Lighting Technology Center (CLTC) at the University of California at Davis and support from Public Financial Management. The guide was written primarily to assist San Francisco Bay area municipalities that are considering SSL installations. But the guide would be informative to any municipality considering LED-based roadway lighting. The document covers topics ranging from the basics of LED lighting technology to the use of adaptive controls in roadway applications to financing options for SSL projects. The BACC and Energy Solutions have identified more than 240,000 municipally-owned fi xtures in the Bay area that are ripe for conversion. "Upgrading these street lights to LEDs would yield annual energy savings of 60 million kWh, enough to power 10,000 singlefamily California homes,” said Ted Pope, vice

light Initiative that's focused on catalyzing the conversion of more than 200,000 lights. The partners announced the new guide at the recent Next Generation Streetlight Workshop held in Hayward, CA. Hayward is in the process of upgrading 8000 street lights to SSL. "We know how beneficial the upgrade to advanced street lights is to a city’s budget, to the environment, and to public safety," says Morad Fakhrai, director of public works for the City of Hayward. "We also know that a successful transition can be complex. This guide is a great resource and will be of great benefit to all forward-thinking cities." "A city such as Hayward with 8000 lights could save $450,000 per year or more in power and maintenance costs, improve lighting quality, and reduce its climate impacts," said Rafael Reyes, BACC executive director. "This is a good time for cities to act given the currently substantial incentives available, low cost of financing and very attractive payback times." The new guidebook is available in PDF form on the BACC website. The BACC is a publicprivate initiative of the Silicon Valley Leadership Group with backing from Bank of America, Pacific Gas & Electric, and more than 70% of the municipalities in the Bay area. Previously GE Lighting announced a partnership with the BACC. "LED lighting has been identified as a top opportunity for excellent financial, community and environmental

LEDsmagazine.com

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funding programs benefits, and GE has tremendous expertise on efficient lighting solutions," said Rafael Reyes, executive director of the Bay Area Climate Collaborative. "Through our collaboration, we will help local governments save millions of dollars that can be reinvested to strengthen the regional economy." GE Lighting will support the program

with outreach programs and sharing of the expertise that it has gained through many SSL street-light projects such as the ongoing Las Vegas project that covers 50,000 fi xtures. While we regularly write about impressive numbers of LED street lights being installed in the US and around the world, the transition is in its infancy. ◀

DOE compares LED pendants The DOE has also completed a Caliper report covering LED pendant lighting, testing 11 linear products available in both an LED and fluorescent versions. Fluorescent products typically offer more different configurations, whereas LED are typically only available in one or two lumen packages. The report suggests that, moving forward, LED products

would benefit from a wider range of lumen packages. The luminous efficacy of LED linear pendants is often higher than the efficacy of their fluorescent counterparts. The specified efficacy for the surveyed LED luminaires reached 85 lm/W, with measured efficacy for the products going as high as 79 lm/W. ◀

EPA progresses on Energy Star luminaires and lamps specifications The US Environmental Protection Agency (EPA) has published version 1.2 of the Energy Star luminaires specification and released the third draft of version 1.0 of the Energy Star lamps specification – both of which are being driven by the SSL transition. The EPA continues to tune its Energy Star specifications for lamps and luminaires, and manufacturers of LED-based lighting products that want to seek Energy Star status have new targets. Version 1.2 of the Energy Star luminaires specification guides the design of directional and nondirectional SSL fi xtures while the Energy Star lamps specification that is in draft form targets retrofit lamps. The lamps and luminaires specifications aren't specific to SSL products, but LEDbased products are driving much of the work in the specifications, because of the efficacy and light output advancements in SSL. Still, the EPA has backed off a bit in the planned efficacy ramp. Version 1.2 of the luminaires specification is available on the EPA website. One major change is the elimination of the previously announced plans to mandate efficacy of 70 lm/W by September 1, 2013.

LEDsmagazine.com

The EPA has left the requirement at 65 lm/W until it considers version 2.0 of the specification. The new version also eases light output requirements of some directional luminaires such as ceiling-fan lights with multiple heads and chandeliers. In such non-directional products, the specification calls for measuring the performance of the light source, whereas in directional products the performance of the integral luminaire is measured. The agency noted that in the excepted applications, the prior 800-lm minimum requirement isn't appropriate. The third draft of Energy Star lamps version 1.0 test methods has been released as well. These test methods include the elevated temperature life test, ambient temperature life test, elevated temperature light output ratio, start time, and run up time. The new draft has language that clarifies the products that are and are not eligible for Energy Star recognition. The Elevated Temperature Life Test has been modified. Moreover, there are changes in luminous intensity distribution requirements and in uniformity of color over angle requirements. ◀

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funding programs DOE updates the latest L Prize lamp test results, rebate offers The DOE has released another update of its testing of the Philips Lighting LED 60W-equivalent retrofit lamp that won the L Prize. The tests have reached what the agency considers the equivalent of 18 years of household use with no failures. The DOE also released a summary of rebates available for the SSL product that range as high as $20 per lamp. After 20,000 hours of operation, the full lot of 200 sample lamps are all still operating. Moreover, the DOE said that average lumen maintenance remains above 100% of their initial output. The tests are being conducted in an environment where the ambient temperature is maintained at 45°C. Based on typical household lamp use that averages three hours per day, the DOE says that the 20,000 hours is equivalent to 18 years of residential usage.

Such a lifetime makes the lamp price more palatable with Home Depot currently selling the product for $30. Of course the price is even more attractive for consumers that can snare one of the rebates being offered by certain utilities around the US. Efficiency Vermont is offering a $20 rebate through Home Depot stores in the state. The Southern Minnesota Municipal Power Agency is offering businesses a $20 rebate and consumers a $15 rebate. Puget Sound Energ y in Washington State is offering consumers a $10 rebate plus a $5 discount coupon usable at Home Depot stores, as well as a $20 rebate for business customers. The L Prize website includes a complete list with other offers in Illinois, Colorado, and Massachusetts. ◀

Caliper 2012 year in review The DOE has released a year-in-review of its Caliper program, and suggests that LED products are becoming more efficient, less costly, and producing more light than ever before. In 2012, Caliper reports focused on a single product type, rather than using a number of different lamps and luminaires in a single summary report. By doing this Caliper could provide more in-depth analysis of the performance baseline of conventional products and the expectations for LED products. The LED products that were examined in 2012 included floodlights, AR111/PAR36 lamps, downright retrofits, BR30/R30 lamps, linear pendants, wallwashers, and PAR38 lamps. The DOE has reviewed years of Caliper data and highlighted some trends, although the agency warns that some of the points may not be statistically meaningful. Still the comparison shows where the SSL segment is trending. One trend the DOE has noticed include the rise of luminous efficacy over the years, though 2012 saw a drop of 3 lm/W (from LEDsmagazine.com

55 lm/W) that may have been caused by the inclusion of recessed downlight wallwashers, which generally have a lower efficacy regardless of their light source. Other trends include a steady rise in CRI, with the average rising 2 points this year to 82, increased availability of appropriate CCTs, and an increase in input power from a mean of 7.7W (lamps only) in 2011 to 14.2W (lamps only) in 2012. Caliper has also identified some of the possible limitations current LED offerings have. These limitations include LED products lacking the modularity of conventional products, a lack of lumen package options, the initial cost of LEDs, and inaccurate manufacturer claims. When compared to other years, the 2012 Caliper reports suggest that price is being reduced, and the lumen output of LED lamps is increasing. The Caliper data shows that, while LED products have gotten much more competitive since 2006, there is still constant improvement in quality, cost effectiveness, efficacy, and control features.

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Marietta, GA 800-669-0624 Middletown, OH 877-669-3602

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lighting | RETROFIT LAMPS

Varying approaches to LED retrofit lamps show no limit After the incandescent lamp changed little in more than a hundred years, emerging SSL lamps show remarkably diverse approaches in attempts to replace the incumbent, reports MAURY WRIGHT.

ED-based retrofit lamps remain the most popular topic in the solid-state lighting (SSL) industry, despite the fact that a form factor such as the A-lamp does little to support the inherent advantages of LED sources. Still, the huge number of retrofit-lamp sockets installed around the globe make the retrofit lamp important to both lamp manufacturers and users looking to proliferate SSL technology and save energy. And while the basic size and type of socket may be fixed, manufacturers are taking vastly different approaches to try and win in what could be a short-lived market. Many of the lampdesign topics we will discuss here could be examined relative to many different types of retrofit lamps. The potential list includes LED-based tubes designed for linear fluorescent sockets and directional and reflector products such as PAR, MR, and BR lamps. In this article, however, we will focus on omnidirectional A-lamps that are the most prevalent lamp in use. You need look no further than at a list of the most popular articles on the LEDs Magazine website for 2012 (www.ledsmagazine. com/news/9/12/21) for proof of the appeal of the topic at hand. More than 25% of the top 20 list had a retrofit lamp focus.

MAURY WRIGHT is the Editor of LEDs

Magazine. LEDsmagazine.com

But ironically, the opportunity for companies to sell retrofit lamps is inherently limited. Socket saturation will occur fairly quickly. As we’ve reported previously, outspoken Tempo Industries CEO Terry Walsh predicted saturation within five years at The LED Show last summer (www.ledsmaga__________ zine.com/features/9/10/8). ________________ Saturation will happen for two reasons.

all of those retrofit-lamp startups out there burning through venture money, the message had better be get to market quickly. And for companies such as Philips Lighting, that may have invested more than anyone in retrofit lamp development, good job but get your money back in a hurry. In actuality, there is still a huge opportunity. In a report issued in April 2012, Strategies Unlimited repor ted that there were $2.2 billion in LED-based retrofit lamps sold in 2011. The report projects 30% annual growth through 2016. But saturation could happen shortly after the 2016 timeframe.

Lamp design

FIG. 1. Philips Lighting has taken different

design approaches on the L Prize-winning lamp, the EnduraLED family, and the new Energy Saving LED A19 lamp (left to right). First, demand will drop as long-lasting LED lamps become predominant and don’t need to be replaced often. Second, purpose-built SSL luminaires will make much better use of LED sources and will become increasingly popular even in residential applications. For

Having covered the market a bit, let’s transition to a discussion of the products and design approaches. We will start with Philips because of the noted success the company has had including with the US Department of Energy (DOE) L Prize winning lamp and the latest change to their design approach. Philips has built retrofit lamps using a number of approaches, but is probably best known for the remote-phosphorbased designs that have a yellow or orange tint when powered off. As we covered in a recent contributed article, remote-phosphor designs that combine very efficient blue LEDs with phosphor on a secondary optic, provide an efficacy advantage over designs that use phosphor-converted white LEDs (www.ledsmagazine.com/features/9/7/6). Moreover, remote phosphor can provide FEBRUARY 2013

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lighting | RETROFIT LAMPS more consistent color mainapproach (Fig. 1 on right). Philips is still using remote phosphor on tenance because the phosCompetitors had cer- the 2700K lamp, but the phosphor is applied phor is not subject to tainly questioned the look on an inner dome that isn’t readily visible. the heat generated by of the remote-phosphor The 5000K Daylight version of the lamp simthe LED, and therefore lamps. And some speci- ply uses phosphor-converted LEDs. Manedoesn’t shift in color fiers would be unlikely gold said that the company would be updatover time. to use the lamps in fi x- ing its 75W- and 100W-equivalent lamps The Philips remotetures where the lamps to use the new design down the road, phosphor design was first are exposed. The Home although the company just began shipping revealed several years back Depot retailer even installed the 100W-equivalent EnduraLED product in when the company announced signs near EnduraLED lamps December as we will discuss a bit later. their entry into the L Prize comexplaining to customers that petition for a 60W-equivalent the yellow or orange lamps emit- Best Buy Insignia lamp retrofit lamp. The company first ted white light when powered While Philips moved to a planar mounting commercialized the technolon. Philips insisted all along that scheme for its LEDs, another new lamp on ogy in the lamps sold under the performance was more impor- the market, the Insignia lamp from retailer EnduraLED and Ambient LED tant than the off-state appearance Best Buy, took yet another approach to verbrands in different parts of the of the remote-phosphor lamps. But tically mounting LEDs for good light distriglobe. Later, the company comthe new design could mean that the bution. Insignia is retailer Best Buy’s house mercialized the L Prize winner that company felt pressure to offer lamps brand for many types of consumer electronics including TVs. In November the company had to meet higher standards than with more of a legacy look. the Energy Star-compliant FIG. 2. The Insignia lamp Todd Manegold, director announced the SSL lamp along with Cree EnduraLED products. from Best Buy mounts Cree of LED lamps marketing at who is supplying the LEDs for the lamp. The design looks white and somewhat like Fig. 1 shows the L Prize LEDs inside the vertical Philips Lighting, said, “We lamp on the left and the cooling surfaces directed at have been focused on repli- a traditional lamp, although you can clearly EnduraLED lamp in the the globe on the opposite cating traditional sources.” see the lamp is broken into three globe segcenter. The products share side of the lamp. He said the company fi rst ments separated by what are apparently the same shape and both attacked the problem of cooling surfaces (Fig. 2). What isn’t apparent are based on three illumination chambers delivering equivalent performance and is that the LEDs are mounted on the inside of those surfaces shining at the with air-flow channels between the seg- the warm CCT of incandesglobe segment on the oppoments for cooling. The LEDs are mounted cent lamps, and now is site side of the lamp. There near the center axis of the lamp in each addressing aesthetics. is nothing in the center of segment on a vertical circuit board that’s Despite the similar the globe. The result is approximately perpendicular to the center shape of the lamps, a well performing 13W axis. The LEDs are directed outward and w h ich Ma negold lamp with a good omnislightly upwards and downwards to deliver referred to as iconic directional beam and a an omnidirectional beam. and easily recogprice of $16.99 for a 800There are, however, significant differ- nized as a Philips LED lm 60W equivalent. Best ences in the designs. The L Prize lamp uses lamp, the new Philips Buy also offers a 9W, 450a different phosphor composition, and adds Energy Saving LED A19 lm 40W-equivalent lamp. some red LEDs to deliver the combination lamps are much differReviews have been generof the high 90 CRI required by the L Prize ent internally. The LEDs ally positive for the dimming rules along with efficacy over 90 lm/W. The are mounted on a plane perperformance as well. The design lower-cost EnduraLED product uses a phos- pendicular to the center axis team behind the product remains phor that absorbs more of the blue LED light, of the lamp, projecting light unknown at this point. While Cree still delivers the warm 2700K CCT, but offers upwards into the light chamber. participated in the announcement, less lumen output and lower efficacy. The optic itself must ensure that the company said it did not design the lamps still deliver an omnidiPhilips new architecture the lamp. The company did perrectional distribution. And clearly Interestingly, Philips just announced a new the design works, because the form its Thermal, Electri60W-equivalent lamp family at the end of 2700K version that Philips calls FIG. 3. Rambus has used cal, Mechanical, Photomet2012 that maintains the general shape of the Soft White has already gained a cylindrical MicroLens ric and Optical (TEMPO) prior lamps, but that is white in the off state Energy Star status and Energy light guide implemented test suite on the design (www.ledsmagazine.com/news/9/12/10). The Star requires an omnidirec- in three segments in an (www.ledsmagazine.com/ SSL A-lamp design. new design also eliminates the segmented tional beam distribution. news/8/9/32). _________ And Best

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lighting | RETROFIT LAMPS Buy said it is designed to meet Energy Star requirements and that certification is under way. Like most of the Insignia products, the lamp is being made by an unnamed contract manufacturer.

Rambus MicroLens Another new approach to retrofit lamps comes courtesy of Rambus. The company is an intellectual property (IP) specialist that doesn’t manufacture products but rather licenses technology to other manufacturers. Its play in the lighting segment is a light guide technology called MicroLens that carries rays from the LED sources and includes small optical elements embedded within the layers of the guide to deflect some rays and provide a naturally diff use light. MicroLens has primarily been used thus far to develop flat planar lighting. GE Lighting is one licensee and recently announced a pendant luminaire based on the technology (www.ledsmagazine.com/news/9/11/17). Cooper Lighting and Fern-Howard have also

FIG. 4. Materials specialist 3M was first to use a light guide in a retrofit lamp, mounting the LEDs in the base.

licensed the technology. In the case of the A-lamp that Rambus introduced at the Consumer Electronics Show in Las Vegas, Rambus has manufactured a pilot run of an end product but will still look to partners to ultimately bring the product to market. Elite Group will be the initial source for a 60W-equivalent A19 lamp due in the second quarter. The retrofit lamp uses three cylindrically shaped MicroLens segments that essentially form a cylindrical lamp (Fig. 3). The LEDs are mounted in a circular fashion around the

base of the lamp shining upwards into the light guide. Rambus believes that it has an approach that will be cheaper to manufacture compared to other LED lamps. “Our unique design has all the benefits of the best LED technology available and offers a significant bill of materials cost savings,” said Jeffery Parker, president of the Rambus Lighting and Display Technology division. That claim of course depends on the cost of making the light guide. Moreover, it’s not clear that the design could meet Energy Star requirements that require uniform luminous intensity over a range of 0° to 135° with 0° being the top of the lamp. The lamp should deliver an even beam around the circumference of the cylinder. But it’s not clear that it could generate uniform light upwards and downwards.

3M LED Advanced Light The Rambus lamp is the second product announced in the second half of 2012 to use light guide technology – the first being from another surprise market entrant 3M (www. ____ ledsmagazine.com/news/9/8/21). The giant ____________________ company is a materials specialist, and evidently saw a good chance to use a number of its materials technologies in a fast-growing market segment despite the fact that it hasn’t previously sold lighting products. The approach depicted in Fig. 4 greatly simplifies the driver design, as the driver is

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lighting | RETROFIT LAMPS

FIG. 5. Osram won the race to deliver a

100W-equivalent lamp in the Sylvania Ultra LED 20W A21 product. located in the relatively spacious globe. Most other SSL retrofit lamps cram the driver into the base and/or neck of the lamp. The 3M design allows air to flow into the lamp just above the base and exit through slots in the upper half of the globe – cooling both the LEDs and the driver. The LEDs are mounted facing upwards around the circumference of the neck of the lamp shining upwards into the light guide. A number of 3M materials are used in the lamp including optically clear adhesives used on the globe. The design also uses 3M’s Enhanced Specular Reflector material in the light engine. And the design uses 3M electrical connectors. The result is an 800-lm lamp that is being sold at many Walmart stores for $25. 3M is offering both 3000K and 5000K versions. The warm-white version requires ten LEDs to deliver the specified flux, while the coolwhite version uses nine LEDs.

and handling the associated thermal issues – drawing heat away from the LEDs to ensure reliable operation. The industry has eagerly sought an LED-based alternative. Back at Lightfair International last May, we witnessed dueling 100W-equivalent news releases from the likes of GE Lighting, Switch Lighting, Philips Lighting, Lighting Science Group and Osram Sylvania (www.ledsmag_________ azine.com/news/9/5/4). Most pledged to be ______________ first to market, but commercial delivery was far from certain in 2012. It turns out that Osram Sylvania won the race by a nose over Philips Lighting (www. ___ ledsmagazine.com/news/9/11/6). In mid _____________________ November some Lowes retail stores had the Sylvania Ultra LED 20W A21 lamps on shelves. Philips EnduraLED lamps shipped to Home Depot starting December 1. The other contenders have yet to ship products.

Sylvania Ultra LED The Sylvania product (Fig. 5) outputs 1600 lm with efficacy of 80 lm/W. It has a CRI of 80, color temperature of 2700K and is dimmable to 10%. The company said that based on the 25,000-hr rated life, the lamp would save consumers $220 over its life relative to an incandescent lamp. “Today’s announcement from Osram Sylvania shows a commitment to providing high quality, energy saving products,” said

100W-equivalent race Perhaps the most exciting news over the course of 2012 in the retrofit lamp area was the race to offer the LED equivalent of a 100W lamp. Government regulatory guidelines around the globe are forcing 100W incandescent lamps from the market. Ironically, such regulatory agencies targeted 100W lamps first because they use more energy than lower-wattage lamps. But those higher-output lamps are also harder to design with LEDs because of the requirement of delivering on the order of 1600 lm LEDsmagazine.com

_______________

FIG. 6. GE Lighting will use a SynJet

active cooler in its 100W-equivalent A19 lamp due on the market soon. FEBRUARY 2013

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lighting | RETROFIT LAMPS Phil Rioux, Osram vice president of lamps and general lighting. “We have a deep understanding of the challenges facing businesses and consumers, such as saving energy and reducing electricity bills without sacrificing quality of light.” The Sylvania design, like many other SSL retrofit lamps, uses a segmented architecture that mixes cooling channels and the optic globe. It is white in the off state and could probably pass for a legacy frosted light bulb. You may note in the product name that the Sylvania lamp is in the A21 form factor as opposed to the A19 form factor that is most common in residential incandescent lamps. A21 lamps can have slightly longer necks than A19 lamps. The slight size difference matters little in many applications because they both use the same Edison socket base. But A21 lamps won’t FIG. 7. Switch Lighting uses a silicone-based liquid inside the

globe of its retrofit lamps to cool the LEDs drawing heat to the surface of the globe.

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fit in every application. The Philips 100W-equivalent is also an A21 lamp. It delivers 1780 lm consuming 22W. Sylvania also wins the efficacy race by a nose. GE Lighting, for its part in the race, said all along that it would be sometime in 2013 before it delivered the 1600-lm Energy Smart LED lamp (Fig. 6). But the company has steadfastly promised an A19 size. Ironically, the company will add components to the design to reach the smaller size. GE has invested in Nuventix and licensed the company’s SynJet technology that includes active cooling devices that create pulses of air. GE will use a SynJet in its 1600-lm lamp and that active cooling will allow the company to minimize the size of the heat sinks used and hit the A19 form factor. The architecture comes at a price both in bill of materials and efficacy. GE hasn’t said what the lamp will cost, but the SynJet cooler will increase the components costs over passive heat sinks. Moreover, the 1600-lm design will use 27W because the SynJet does use a small amount of energy.

The startup dilemma Returning to a theme we struck early on, new players in the retrofit lamp space face the challenge of trying to get to market quickly with an innovative design, and capturing share prior to saturation. No company is more instructive in the process than Switch Lighting. We featured Switch Lighting on the cover of LEDs Magazine back in June of 2011 after their lamp design debuted in April of 2011. The design story was very compelling. The company would fi ll the globe of its lamp with liquid to draw heat away from the LEDs. At The LED Show last summer, CEO Tracy Bilbrough revealed the liquid to be silicone based (www.illuminationinfocus.com/news/3/8/3). The company has introduced 40W-, 60W-, 75W-, and 100W-equivalent lamps as well as a novel LED 3-way lamp. Indeed, the company was the first of the retrofit lamp players to tout a 100W-equivalent lamp. But only in the fall of 2012 did Switch began to sell lamps commercially. The Switch40 sells for $42.99, the Switch60 sells for $49.99, and the Switch75 sells for $58.99. The Switch100 is priced at $65.99 but still isn’t readily available. The reason for the delays in shipping are basically unknown to anyone outside the company. Surely the design is complex, and the pricing supports that fact. Seeing sample lamps over the course of 20 months, it’s apparent that the design went through a number of changes. The LEDs that are mounted facing outward around the center of the globe were once installed on aluminum fingers. Some type of printed-circuit board has replaced those fingers. Fortunately for Switch, the company had an early start in the retrofit lamp race. They still have an opportunity to make money assuming the lamps deliver on the promised specs. A startup entering the market today facing a two year development cycle would have a tough time recouping the R&D expense with socket saturation looming. LEDsmagazine.com

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luminaire design | WAVEGUIDES

MHA Lighting takes unique approach to LED fixture design with Rods with Holes technology A UK-based LED lighting manufacturer is using a unique light-waveguide approach in which LED light is shone sideways into acrylic rods. In turn, these light-emitting rods provide a uniform light distribution, explains TIM WHITAKER.

HA Lighting has developed a unique LED approach that opens up the use of solid-state lighting (SSL) in new areas and applications which competitors are failing to address with the same level of efficiency. Using patented intellectual property (IP), MHA Lighting is the only known LED lighting manufacturer to shine light sideways into an encapsulation, rather than directly outwards. Th is avoids direct eye-contact of the light source, and provides a safe and efficient light output. The flexibility of its patented technology allows MHA Lighting to replace fluorescent fittings and other conventional lighting technologies, in both indoor and outdoor applications, while meeting all relevant standards. MHA uses a light-waveguide technology in which the LED light is emitted sideways into acrylic rods. This is achieved using specially-designed, linear, printed circuit boards in which the sections containing the LEDs are bent at 90˚ from the main sections. The PCBs can be interlocked so that two LEDs on vertical sections can sit back to back (Fig. 1). The LED-containing extensions of the PCBs are then inserted into matching holes in an acrylic rod (Fig. 2). For obvious reasons, MHA describes its technology as “Rods with Holes.” The LEDs emit sideways into the rod. Emission from the rod is controlled by a reflective coating which is designed according to the desired light distribution. In this way, light is emitted from the length of the rod in a uniform manner.

The technology overcomes the problem of directionality, and achieves a light distribution of such high uniformity that it is better than traditional fittings. Luminaires create a wide, rugby-ball shape of light to provide exceptional uniformity which for most applications, both internal and external, is crucially important. The light-waveguide technology used by MHA fits in with a growing industry trend of maximizing “useful lumens,” where light is directed efficiently to specific locations. This is in contrast to traditional light sources, which are typically omnidirectional and wasteful.

Unique approach MH A’s lig ht-waveg uide technolog y approach differs from technologies used by other LED luminaire manufacturers, which usually shine light directly out of the fi xture or scatter the light through an optical diff user. Direct emission: In this approach the LEDs are usually arranged in a cluster or matrix to shine their light directly out of the fitting. The earliest forms of LED-based halogen-replacement downlights and fluorescent-tube replacements utilized this approach with mixed results. The light

TIM WHITAKER is an Editorial Consultant with

LEDs Magazine.

FEBRUARY 2013

LEDsmagazine.com

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output was limited and in many cases the LEDs would overheat, or the individual light sources were too bright, leaving an uncomfortable after-image for the viewer. LEDs obscured by a diffuser: In this approach, the LEDs are located behind a diffuser so that the light source is masked from the observer. In principle this approach produces the least amount of glare, as the LEDs are hidden. However, the diff user introduces losses to the system (reducing the efficiency by 20-30% or more). It also inhibits control of the beam direction, which tends to be dominated by the characteristics and design of the diff user. The MHA approach to luminaires differs significantly from either of the above methods. The technology relies on reflecting the light internally and using the optical properties of the acrylic rod before the light is emitted in a uniform manner. The LEDs are arranged to shine their light sideways within the optic so that only a small proportion of the light is emitted directly from the fitting. The remaining light waves are guided and then subsequently reflected out. Th is approach optimizes the utilization of light from the LED source and also allows for an exceptionally good degree of beam control and uniformity of light. Th is minimizes light wastage and light pollution.

FIG. 2. In MHA’s

“Rod with Holes” technology, LED light shines sideways into acrylic rods and is emitted uniformly along the length of the rod.

The reflector plays a crucial role in MHA’s technology as it is Lambertian in its reflectance, meaning it is diff usely reflective like a matte object, as opposed to a mirror-like reflector that exhibits specular reflection. The optical waveguide efficiency of MHA’s Rod with Holes technology is very high and has been evaluated extensively at the UK National Physical Laboratory in Teddington, London. Optical efficiency was found to be in a range of 75-85% depending on the specific system confi guration and the

required degree of directional beam control. Th is efficiency factor includes all the loss factors associated with the light path from the LED to the task plane. By comparison, conventional diff user-based systems may have efficiencies as low as 50-60%, greatly reducing the overall light output from the fitting. Light diff users also tend to inhibit any kind of directional beam control, and this may be an important consideration for effective overall light deployment. The design flexibility inherent in this tech-

FIG. 1. LEDs are mounted on PCBs on sections that are bent at 90° to the main board. Pairs of LEDs are inserted into matching holes in acrylic rods. FIG. 3. MHA Lighting’s TiLite luminaires, with 80 CRI and 4000K color temperature, replaced T5 fluorescent fittings in Scott Safety’s UK factory (www.ledsmagazine. com/press/37007). LEDsmagazine.com

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LED manufacturing | LARGE SUBSTRATES

FIG. 4. LED light fittings consuming 67W from MHA Lighting have replaced 170W SON

fittings at Bournemouth Airport in the UK (www.ledsmagazine.com/products/37283). nology facilitates secondary benefits when used in specific tasks. For example, in street lighting, it is possible to use lower mounting heights, to reduce light pollution, reduce glare and focus light on the task area. The technology offers a high degree of light uniformity of which the beam angle can be adjusted by a simple modification of the reflector. Th is has the additional benefit in internal applications, where it is possible to direct light away from windows and concentrate it in required areas or in

external applications, such as garage forecourts, where light can be reflected inwards to avoid light pollution.

Visual appearance In tandem with the beam-control characteristics, the Rod with Holes approach creates a luminaire where light output is perceived as emanating from a light strip or bar, rather than from each individual LED. When individual LEDs can be seen directly, very powerful after-images can be produced along with

eye discomfort and glare. The MHA approach yields optimum lighting in an aestheticallypleasing manner, with fittings that are just as pleasant to look at as a fluorescent. The high optical efficiency of the MHA waveguide system results in comparatively high luminous efficacies (i.e. luminaire lumen output per circuit watt), and thereby a very good energy-saving performance overall. Th is is true even against very efficient fluorescent lighting systems, such as T5s. In addition to the energy savings there is an accompanying saving in maintenance costs as there is no need for maintenance for a lighting system that is predicted to last as long as 10-15 years. The Rod with Holes technology encourages a luminaire design in which thermal management can be achieved via a simple passive heat-sinking method. The surface area of the aluminum fitting acts as the heat-sink, and there is no need for active thermal control or an excessively heavy fi nned heat-sink, for example. The MHA approach is unique in this respect and can facilitate distinctive designs with aesthetic appeal. Essentially, MHA has a light engine that can be adapted to suit any footprint, depending on the application. The company rarely has to carry out any new product development, as the product range essentially uses variants of the same light engine.

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EASY. FAST. COMPACT. (All this, and brains too.) Welcome to a new era in smart connectivity – NECTOR power systems from TE Connectivity. NECTOR interconnects give you the power to connect every ﬂoor of your intelligent building in smarter ways than ever before. Their compact shape and smart design allow you to seamlessly integrate lighting, power and data throughout any retail, commercial or ofﬁ ce environment. With the TE NECTOR product family, the possibilities are endless. Watch the NECTOR video to see the future of power and luminaire design at NectorPower.com

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standards | LED DATASHEETS

ANSI works to standardize LED datasheet for white LEDs JIANZHONG JIAO reports that the ANSI standards body hopes to facilitate the communications of

pertinent component characteristics between LED manufacturers and SSL product developers.

he American National Standard Institute (ANSI) is currently developing a standard datasheet for white LEDs used for general illumination, that can in turn help the solid-state lighting (SSL) industry overcome obstacles to broader deployment. Datasheets are an important format for LED manufacturers to present product information and characteristics to users. Over the years, more and more LED manufacturers have entered the general lighting market, and in almost all cases they use datasheets to communicate with users and assist them in selecting and implementing LEDs in lamps, light engines or luminaires. In the past, the information LEDs manufacturers have provided in these datasheets has not been consistent, and as such, users have expressed concern over lack of fair comparisons when selecting LEDs. In the general lighting industry, most of the components used in lighting products have been standardized by ANSI such as bulb shape, base, etc. Moreover ANSI has defi ned all major characteristics, such as voltage, wattage, etc. LEDs for lighting applications, on the other hand, are still rapidly evolving. At least for now, ANSI has decided not to standardize LED package shape, footprint or other physical parameters, which might restrict further technology and product development. Instead, the proposed ANSI

LED datasheet standard seeks to standardize the information being communicated between LED manufacturers and the rest of the industry to ensure that fair and consistent comparisons can be made by LED users. In developing the ANSI LED datasheet standard, the ANSI Working Group proposed: “The purpose is to specify the standardized white LED package datasheet, or data reporting format, as the means of communication between LED package producers and users. The defi ned contents and format of the datasheet shall be followed.” There are some who argue the necessity of such standardization. One concern is that a standardized datasheet may bury some liabilities for the claims made by LED manufacturers. Another concern is whether there are sufficient standards to be referenced when obtaining or measuring the characteristics and properties listed in the datasheet. After extensive discussions, however, the experts from participating LED manufacturers principally agreed that an ANSI standard datasheet can be a practical approach which will benefit the SSL industry. In addition, the establishment of some critical

DR. JIANZHONG JIAO, Director of Regulations and Emerging Technologies at OSRAM Opto Semiconductors, Inc., is an internationally recognized lighting expert. He has been actively involved in LED and SSL standard development activities. He serves as the past Chairman of the SAE Lighting Committee, past Chairman of NGLIA, past Chairman of the NEMA SSL Technical Committee, active member of IESNA Testing Procedure Committee, Roadway Lighting Committee, and Computer Committee, ANSI SSL Working Groups, Standard Technical Panel of UL8750, standard committees in IEEE, CIE USA, SEMI, JEDEC and other organizations. He can be reached at jianzhong.jiao@osram-os.com LEDsmagazine.com

standards for testing LEDs will be largely helpful for LED manufacturers in consistently obtaining the LED characteristics to be listed in the datasheets. Based on a broad view of datasheets currently published by major LED manufacturers and a general consensus from LED industry experts, the contents of the proposed ANSI LED standard datasheet are defined and grouped into three areas: performance and operational characteristics; physical and electrical connection characteristics; and usage recommendations. The standard also recommends that the performance characteristics be obtained by the established (or to be established) industry standards. For example, the photometric and colorimetric characteristics should be measured by IES LM-85 (to be published); thermal characteristics should be measured by JEDS51-51; and lumen and color maintenance should be measured by IES LM-80. The standard datasheet will also list optional characteristics that LED manufacturers may want to, but do not necessarily need to disclose. In the performance characteristics area, the standard datasheet fi rst addresses photometric performance. LED manufacturers are required to provide information for correlated color temperature (CCT) versus luminous f lux, color binning, luminous intensity distribution, luminous flux changes versus forward current and versus temperature, color changes versus forward current or versus temperature, and luminous efficacy versus forward current FEBRUARY 2013

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standards | LED DATASHEET (as optional). Some information is to be presented in a table format, and other in a graphic format. For example, for each listed CCT, whether it is within, or in addition to ANSI C78.377 specifications, LEDs luminous flux, CRI values and corresponding product codes are listed in a table format. Another example is that the LED spectral power distribution (SPD) is provided in a graphic format. Even though SPD may not be directly used to design LED lamps or luminaires, it has been widely acknowledged that LED users, including lighting designers, fi nd value in reviewing SPD information. The luminous intensity in angular or spatial distribution is also presented in the graphic format. It is widely expected that LED lumen and color maintenance information is needed for designing SSL products. However, this information can take over eight months of LM-80 testing to become available. As such, when new LEDs are launched for production and the corresponding datasheets are published, lumen maintenance test data is typically not yet available. Thus, the ANSI standard does not require lumen maintenance information to be provided on the datasheet. LED manufacturers have the option of providing this information if the previous LM-80 data and TM-21 projection for lumen maintenance of a similar LED product may be used as a reference.

Because LEDs are temperature dependent devices, thermal degrading is a critical design element. As such, all temperature related characteristic changes will be listed in the datasheet, often in a graphic format. For the operational characteristics, the datasheet will list operating limits, thermal and electrical characteristics, forward voltage versus forward current, forward voltage binning, forward current versus temperature, and forward voltage versus temperature. Next, the datasheet covers the physical and electrical connection characteristics including mechanical characteristics and electrical diagram. It is required that the LED’s physical properties, such as dimensions, tolerances, locations of optical center, anode and cathode, thermal pad, and electrical connections, be shown in a graphic format, so users can visualize the LED’s physical appearance. The electrical diagram that indicates external electrical connection points is also required and a diagram of the internal diode is recommended. This information helps users properly connect LEDs to the overall electronic systems used in LED lamps, light engines or luminaires. The datasheet also describes the usage recommendation. As the LED assembly process can have an impact on overall performance, a soldering temperature profi le must be provided with the acceptable tem-

perature variation versus time for the LED during the soldering process. Exceeding the allowed temperature during soldering can induce short term damage or a long term impact on LED lumen maintenance. LED packing information is also needed for users to purchase LEDs. Th is information may include mechanical diagrams that show dimensions, number of LEDs per package and packing format – if LEDs are packed as tape and reel, tray, tube, or another format. Optionally, the standard also recommends LED manufacturers provide information for how the LEDs should be handled, including equipment, ESD, etc., as well as what the environmental conditions should be for storage. The intent of the ANSI LED standard datasheet is to ensure LED manufacturers provide accurate, consistent and reliable product information, including the order or sequence of that information. It is not ANSI’s desire to put additional burdens on LED manufacturers when establishing standard datasheets and the ANSI Working Group is diligently working to achieve the balance between benefits and burdens of such standardization. All parties involved hope that consistent communication – the ANSI LED standard datasheet – between LED manufacturers and users will be a valuable tool to further assist the growth of the SSL industry.

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alpha led tec hnologies

THE WORLD’S NEWSSTAND®

Alpha’s LED materials technology brings value to the LED Market by: • Increasing efficiency and brightness • Increasing reliability and lifetime • Reducing cost/lumen The applications we address include: • LED die attach and chip-on-board (Level 1) • Package-on-board assembly (Level 2) • Luminaire board assembly and interconnect (Level 3) • Power driver and control system board assembly (Levels 4 and 5) Alpha offers the following products for LED applications: • ALPHA® Lumet™ Solder Paste with SAC and MAXREL™ alloys • ALPHA® Cored Solder Wire • ALPHA® Exactalloy® MAXREL™ Solder Preforms • ALPHA® SACX Plus® Low Silver Bar Solder Alloy • ALPHA® Argomax™ Sintered Silver Products • ALPHA® Atrox™ Conductive Adhesives. For more information go to www.alpha.alent.com/Markets/LED Or, send an email to alphaledtechnologies@alent.com.

Worldwide/Americas Headquarters • 109 Corporate Boulevard • South Plainfield, NJ 07080 • USA • +1-814-946-1611 – Dial 0 • www.alpha.alent.com European Headquarters • Forsyth Road • Sheerwater • Woking GU215RZ • United Kingdom • +44-1483-758-400 Asia-Pacific Headquarters • 8/F, Paul Y. Centre • 51 Hung To Road • Kwun Tong • Kowloon, Hong Kong • +852-3190-3100 © 2013 Alpha

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2013 THE FUTURE. ILLUMINATED. We see the future clearly. And so will you. Philadelphia, PA USA Pennsylvania Convention Center 4.21.13 – 4.25.13

www.lightfair.com

In collaboration with The Illuminating Engineering Society

In collaboration with The International Association of Lighting Designers

Produced & Managed by AMC, Inc.

PHOTO CREDITS (1) BANNER MD ANDERSON CANCER CENTER LANTERN OF HOPE, GILBERT, AZ USA | LIGHTING DESIGN BY CANNON DESIGN | © BILL TIMMERMAN / © MARK SKALNY (2) UNITED STATES INSTITUTE OF PEACE, WASHINGTON, DC USA | LIGHTING DESIGN BY LAM PARTNERS | © GLENN HEINMILLER, IALD, LAM PARTNERS, © BILL FITZ-PATRICK, UNITED STATES INSTITUTE OF PEACE (3) CHANDLER CITY HALL EXTERIOR LIGHTING, CHANDLER, AZ USA | LIGHTING DESIGN BY SMITHGROUP JJR | © TIMMERMAN PHOTOGRAPHY

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focus on

SSL modules A modular approach to LED-based luminaire design offers a number of benefits to product manufacturers including fast time to market, lower upfront engineering costs, and the ability to offer luminaires that can be serviced or upgraded in the field. Modular solid-state lighting (SSL) components enable custom luminaire design based on combinations of off-the-shelf LED light engines, module holders/brackets, drivers, optics, and other elements. The downside of modules can be less flexibility in absolutely matching a luminaire design to an application and slightly higher bill-of-materials cost relative to full custom designs. Still, modules offer benefits that will clearly make the technology a lasting part of the ongoing transition of the lighting market to SSL technology. The benefits of modular luminaire design (www.ledsmagazine.com/features/8/11/11) apply in the product development process whether the components at hand are proprietary designs or based on an evolving industry standard such as one of the Zhaga Books (www.ledsmagazine.com/features/9/7/15). This compilation includes both proprietary modular products and ones built to the new Zhaga standards that allow for interoperability of light engines, drivers, optics, and other components from multiple vendors.

Fortimo LED TDLM family by Philips The Fortimo LED Twistable downlight module (TDLM) is a simple to install and easy to maintain modular LED light. Th is module is available in two color temperatures, 3000K and 4000K, includes a choice of two holders, and has a CRI of 80.The family also includes a number of different lumen-output options, such as a 1100-lm product that’s compliant with Zhaga Book 2: Socketable downlight engine. The term socketable, or twistable in the Philips product name, implies that you can mount the light engine into a bracket without the use of tools. Philips also offers a 2000-lm version that at present isn’t Zhaga compliant.

LMH2 LED modules by Cree The proprietary Cree LMH2 LED module family delivers 95 lm/W, has a CRI of 90, and comes in color temperatures

of 2700K, 3000K, 3500K, and 4000K. The module comes in either a flat lens or dome lens. Since the light source and power supply are separate, the LMH2 can be mounted and wired in a variety of different configurations. Cree recently established a Driver Compatibility Program that established approved drivers for CREE SSL modules and the LMH2 module family is initially the basis for the program (p. 21).

PrevaLED Core family by Osram The PrevaLED Core family of light engines are compliant with Zhaga Book 3: Round light emitting surface 9mm – 23mm that is targeted at spot light applications and requires separate control gear. PrevaLED modules offer a CRI of 93. The modules feature chip-on-board (COB) technology to deliver uniform light emission across the surface. The family features a number of products with a variety of wattages from 10W to 31W, and color temperatures that include 2700K, 3000K, 3500K, and 4000K. The highest efficacy in the family is 108 lm/W.

LED P3LED Recessed Series by Cooper The Iris P3LED LED Recessed Series by Cooper is a Zhaga book 3 compliant series of luminaires that feature interchangeable optics -- the first luminaire that was certified to LEDsmagazine.com

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color quality. The spot-light series features LED lighting with a color temperature range of 2700K, 3000K, 3500K, and 4000K, and a CRI of 80. The efficacy for each module is above 67 lm/W, with the highest being 96 lm/W.

TECOH CFx by Megaman a Zhaga Book. Because Zha ga speci f ications include thermal, electrical, mechanical, and optical interfaces, luminaires must meet the specifications just as light engines must. The series features a minimum CRI of 80, a color temperature of 3000K, and are designed to last 50,000 hours. The series includes a variety of recessed luminaires, including downlights, accents, wall wash and lens products.

The TECOH CFx twist-lock LED modules are designed in compliance with the Zhaga Book 2 specification. These modules use a multi-

Infusion LED modules by GE Lighting GE Lighting’s Infusion LED modules offer a large range of lumen packages, which range from 850 lm to 4,500 lm. The modules are

chip white LED array and feature a lambertian output. Because of the twist-lock design, the light engines enable luminaires that can be retained and upgraded as opposed to being replaced in the field. The modules feature a CRI of 80, and come in color temperatures of 2800K or 4000K.

7100/d1/d2-GR light engine holders by A.A.G. Stucchi designed for compatibility with Zhaga Book 5: Socketable engine with separate gear, although the modules aren’t yet on Zhaga’s list of certified products. The series includes six modules, and uses a twist-fit installation/replacement method, allowing the entire module to be removed in seconds. The series includes color temperature options of 2700K, 3000K, and 4000K, with a CRI of 90.

These Zhaga Book 2 compliant holders by A.A.G. Stucchi are designed to hold a Book 2-compliant modular light engine – a socketable LED light engine with integrated electronic control gear. The holder enables light engines to be installed and swapped out if needed.

XSM 80 series LED modules by Xiacto The proprietary XSM 80 series of LED modules by Xiacto rely on remote- or cold-phosphor technology to provide white light. The round modules combine blue LEDs with secondary optics coated in phosphor and Xicato says that technology delivers superior

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focus on | SSL MODULES

Z020C2 by Lustrous The Z020C2 is a Zhaga Book 3 compliant spotlight module designed for commercial lighting. These modules have a CRI of 90, and are meant to showcase products on the retail floor. The company was the fi rst in the Asian region to win Zhaga certification based on testing by UL.

PHJ65d-1/d-2 light engine holders by BJB GmbH The Zhaga Book 2-compliant holders work with LED light engines with 100-VAC through 120-VAC power requirements. This holder features a closed form to reduce the penetration of dust and dirt into the luminaire.

Reflex Easy by iGuzzini The Reflex Easy family of LED luminaires are modular recessed fi xtures that are designed to serve several different applications. The

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New Market Reviews and Forecasts Available Now! NEW! Order today Strategies Unlimited has been researching the LED market since 1994. Find out more about our complete market reports on the overall LED market, LEDs for lighting, and LED lighting fixtures and more! Market analysis and forecast reports include: 𰁴𰀁𰀸𰁐𰁓𰁍𰁅𰁘𰁊𰁅𰁆𰀁𰀮𰁂𰁓𰁌𰁆𰁕𰀁𰁇𰁐𰁓𰀁𰀭𰁂𰁔𰁆𰁓𰁔𰁴𰀁𰀱𰁉𰁐𰁕𰁐𰁗𰁐𰁍𰁕𰁂𰁊𰁄𰁔𰁴𰀁𰀭𰀦𰀥𰀁𰀥𰁐𰁘𰁏𰁍𰁊𰁈𰁉𰁕𰁔𰁴𰀁𰀭𰀦𰀥𰀁𰀭𰁖𰁎𰁊𰁏𰁂𰁊𰁓𰁆𰁔𰁴𰀁𰀸𰁐𰁓𰁍𰁅𰁘𰁊𰁅𰁆𰀁𰀮𰁂𰁓𰁌𰁆𰁕𰀁𰁇𰁐𰁓𰀁𰀭𰀦𰀥𰁔 ...and more!

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Reflex Easy family, which is Zhaga Book 2 compliant, includes a wall washer luminaire, a circular spotlight, and a square design. The luminaires come with a variety of wattages for applications as well, from 14W to 44W.

Helieon by Molex Description: The proprietary Helieon family of LED modules from Molex (developed in partnership with Bridgelux) features a wide vari-

Light up your creative vision with Makrolon® Lumen XT Expand your LED fixture design freedom with Makrolon Lumen XT diffuser sheet. Developed for LED fixture lenses, this new polycarbonate technology delivers different levels of light diffusion and high light transmission in a range of grades. The result: versatility to achieve your vision for LED fixture design and performance.

Makrolon® Lumen XT beneﬁts

ety of products, with varying beam angles, base types, lumen outputs, CRI’s that are all 80 or above, and color temperatures of 2700K, 3000K, 3500K, and 4100K. The versatile family is designed to serve across a wide variety of applications.

𰁏𰀃𰀃𰀃Leading edge technology for uniform LED diffusion 𰁏𰀃𰀃𰀃Versatile range of diffusion and light transmission levels 𰁏𰀃𰀃𰀃Higher impact strength than glass or acrylic

for damage prone areas

LMR2 LED modules by Cree The proprietary Cree LMR2 LED module family features a CRI of 90, color temperatures of 2700K, 3000K, 3500K, and 4000K, and comes with integrated driver electronics, optics, and core thermals. The modules also include an optional heat sink and support dimming down to 5%. The modules are designed for

𰁏𰀃𰀃𰀃High temperature resistance allows more design ﬂexibility 𰁏𰀃𰀃𰀃UL listed ﬂammability rating

For more information: 800.457.3553 or www.shefﬁeldplastics.com Bayer MaterialScience LLC 119 Salisbury Road Shefﬁeld, MA 01257

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focus on | SSL MODULES applications in non-directional lighting, directional lighting, downlighting, or exterior area lighting.

SynJet ZFlow 87 Spot LED Cooler by Nuventix Zhaga Books defi ne a thermal interface to a light engine as well as electrical, optical, and mechanical interfaces, and Nuventix has designed a number of its SynJet-based, active-cooling devices for Zhaga-based luminaire designs. The ZFlow 87 Spotlight LED cooler is 87-mm in diameter and designed for use with Book 3 light engines.

lm and range in color temperature from 3000K to 4000K. The mainstream products have a CRI of 80, although the specialty Artist series comes with a CRI of 90.

S-Class street lighting module by Carclo

The 47W thermal-load version is pictured. Moreover the ZFlow 75 34W version is used in the Cooper Lighting P3LED luminaire.

FORTIMO LED SLM 3000 family by Philips The Fortimo LED Spotlight Module (SLM) 3000 family is designed to illuminate merchandise and attract customers in a retail environment. The family features lamps and drivers with a high CRI

Modular light engines comes in many form factors – driven in part by application – and this new S-Class module from Carclo is designed specifically for streetlighting applications. Carclo is an optics specialists and this is the company's first complete light-engine offering. The S-Class is a proprietary design but still includes the thermal, optical, and electronic elements that can accelerate the luminaire development cycle. Carclo views the entry into the light-engine business in part as a way to provide customers easier access to its optics.

SynJet ZFlow 65 Cooler and CoolTwist Heatsink by Nuventix

and tight color consistency. The products include COB LED technology, which helps the system offer performance of more than 100 lm/W. The family is compliant with Zhaga Book 3 for spotlight applications.

The SynJet ZFlow 65 Cooler and CoolTwist Heatsink is designed for Book 2 applications and light engines such as the Philips Lighting Fortimo TDLM module targeting downlights. Nuventix offers the product in a range of sizes with the capability of handling thermal loads as high as 48W. The 40W unit pictured is 95-mm in diameter and generates less than 28 dBA in acoustic noise.

XLM 80 Series LED modules by Xiacto

EdiLex Spot Light Module by Edison-Opto

The XLM 80 series of linear rectangular modules by Xiacto target linear lighting applications. Like the XSM 80 series, the products use remote-phosphor technology. Family members deliver 3000-4000

With the EdiLex Spot Light Module (SLM) Edison-Opto turned to a COB LED array that it says provides a uniform plane of light across the light emitting surface. The design uses the company’s

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focus on | SSL MODULES E EdiPower II components that come i versions ranging from 8-25W. That in e enables Edison-Opto to offer light e engines that output 800, 2000, and 3000 lm The company says that the product lm. sup supports spot- and flood-light applications via reflectors that if offers in 25°, 35°, and 60° beam widths.

Linear TALEXXengine Stark LLE by Tridonic Tridonic offers light engines in a variety of form factors including the TALEXXengine Stark Linear Light Engine (LLE) family that

comes in rectangular and even square configurations (the QLE). The modules offer efficacy as high as 118 lm/W – 108 lm/W including a Tridonic driver. The newest linear module measures 24 mm (0.95 in) by 280 mm (11 in) for applications such as ceiling troffers. Tridonic offers the products in 3000K, 4000K, and 5000K CCTs.

Cetero SLM by Bridgelux Bridgelux took advantage of its ES series of LED arrays to design the Cetero Spot Light Module (SLM) that is compatible with Zhaga Book 3. The company is offering the light engine in 800-, 1100-, and 2000lm packages. The module comes in a choice of 2700K, 3000K, 3500K, and 4000K color temperatures and a CRI of 80. Moreover, Bridgelux specif ies color consistency within a 3-step MacAdam ellipse.

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19-21 November 2013 M.O.C. Event Centre, Munich, Germany www.sileurope.com

DEVELOPING THE NEW ECOSYSTEM OF LIGHTING CALL FOR PAPERS! DEADLINE: 22 FEBRUARY 2013

The Advisory Board for Strategies in Light Europe is now accepting abstracts for the 2013 Conference. We invite you to submit an abstract and share your knowledge, experience and solutions with industry colleagues from around the world.

For any questions regarding the call for papers please contact: CONFERENCE MANAGEMENT Emily Pryor International Conference Manager T: +44 (0) 1992 656 614 E: emilyp@pennwell.com

Owned and Produced by:

Presented by:

Strategies in Light Europe is in its 4th year of providing Europe’s most comprehensive conference and exhibition for the rapidly-growing LED lighting industry. The event offers a platform for the best networking opportunities and a forum for the sharing of ideas and experiences in the latest technologies and market developments. The 2013 program will include: Keynote and Plenary Sessions, Market Track, Technology Track, workshops, and the Investor Forum. Visit www.sileurope.com for more information on subject areas and how you can submit your abstract.

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technology | COLOR SCIENCE

Understand color science to maximize success with LEDs – part 4 Color rendering, or how color appears when illuminated by a light source, is crucial in the performance of SSL systems, explains GEORGE KELLY, and in the fourth part of our series on color science we will cover how LED and SSL architecture impacts lit objects.

uch of the technical focus on LEDs ticular type of white light sources known as We are aware of the change in colors of and solid-state lighting (SSL) to blackbody radiators. In the third article in objects outdoors from noon to sunset on a date has been on component and the series we built upon this knowledge to sunny day. You may have even had the expesystem efficacy and the potential for saving show how to design LED-based illumina- rience of choosing a paint color at the store energy, but lighting quality matters as well. tion devices which mix the light from differ- under natural or fluorescent lighting and In this part of our color-science series, we ent color temperature white LEDs and from then being disappointed in the color of that will see how high efficacy and paint as it appears on your good color rendering are conwalls at home under incanflicting goals. Moreover, we descent lighting. Both of will address how the industry these examples of color renis attacking the problem of dering are within our comdeveloping efficient and highmon experience, are to be quality light sources. expected, and in part can be In the first article of this explained by different CCTs of series we established three the light sources. foundational principles of What is less apparent, color vision: 1) The relative though, is that the color of response of the three types an illuminated object can of cone cells in the retina is change significantly when sufficient to explain color shifting from one illuminavision; 2) metamerism which tion source to another, even is a direct result of the first when both sources have the principle; and 3) color can be exact same CCT and even characterized by numerous when they have the exact sets of color-matching funcsame chromaticity coorditions, all of which are linear FIG. 1. The SPD of the light emitted by the bulb is modified by the nates. To understand how transformations of each other spectral reflectance of the pigment of the light blue balloon forming this can happen, let’s review (w w w.ledsmagazine.com/ a new SPD that enters the eye. and apply our fi rst two prinfeatures/9/5/4). ciples of color vision. _________ In the second article we used these prin- colored LEDs to achieve results not possiOur fi rst principle of color vision states ciples to explain the origins and uses of ble with white LEDs of the same color tem- that the colors we see are directly related the CIE Color Diagram including predict- perature alone (www.ledsmagazine.com/ to the relative response of the three types ing the color coordinates in the CIE Color features/9/10/15). of cone cells in the retina to the spectral __________ Diagram for mixtures of colors (www.ledsIn this article we will look at color ren- power distribution (SPD) of the light falling ______ magazine.com/features/9/7/14). dering properties of white LEDs. Color ren- on the cone cells. Th is means that two light __________________ We also discussed the origins of the Planckian locus, a dering refers to how the color appearance of sources with widely divergent SPDs can curve through the center of the CIE Diagram illuminated objects can change when illu- nonetheless still result in the same relative which plots the color coordinates of a par- minated by different light sources. Natu- response of the three types of cone cells and rally we expect colors to shift somewhat hence look like the exact same color. Th is is GEORGE KELLY is an LED Technical Specialist when illuminated by light sources with dif- also why a mixture of the light from a red, at Avnet Electronics Marketing. ferent correlated color temperatures (CCT). a green and a blue LED can have the same LEDsmagazine.com

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technology | COLOR SCIENCE tance for indoor LED lighting. The SPD of a The importance of CRI in SSL typical white LED is very different from that CRI is primarily important for indoor lightof typical indoor lights whether incandes- ing and is less important for outdoor lightcent or fluorescent (Fig. 2). Consumers may ing. High-pressure sodium (HPS) street be disappointed to fi nd that the colors of lights for instance, have a very low CRI, in familiar objects in their home or office will some cases as low as 20. Th is poor color renchange significantly when they install new dering is off set by exceptional luminous efficacy, which can be as high as 150 lm/W. LED light bulbs. The lighting industry has faced this prob- Color rendering in this application is genlem in the past and developed the color render0.9 TCS01 Reflected light ing index (CRI) metric to 0.8 TSC02 The situation changes when we view quantify the color render0.7 TCS03 reflected light from two or more metameric ing properties of a partic0.6 TCS04 light sources. In this case, the spectral con- ular light source compared 0.5 TCS05 tent of the light coming from each source is to that of an incandescent 0.4 TCS06 modified by the spectral reflectance prop- source for low color tem0.3 TCS07 erties of the object the light is reflecting off peratures (< 5000K) and to 0.2 TCS08 of before it enters our eyes. A blue object for daylight for high color tem0.1 TCS09 instance reflects at the blue end of the spec- peratures (> 5000K). If the 0 trum, roughly 400-500 nm, and absorbs the match is perfect, meaning 400 450 500 550 600 650 700 750 Wavelength (nm) medium to long wavelengths. Consequently, that colors appear or renthe SPD of the reflected light now is a func- der the same under the FIG. 3. The spectral reflectance of the eight color tion of both the SPD of the source and the light source in question as swatches used in the calculation of CRI plus the strong spectral reflectance properties of the illu- they do under daylight or red used to calculate R9. minated object (Fig. 1). an incandescent source, This complex interaction means that then the index will be an the color of an object can shift dramati- even 100. CRI is not perfect as a predictor of erally considered unimportant when comcally when illuminated in succession by the color rendering performance of a light pared to energy efficiency. Some HPS lamps do have slightly higher CRIs, but at the sactwo metameric light sources. Even though source, but it does do a reasonable job. the two light sources have the exact same CRI is calculated by comparing the chro- rifice of lower luminous efficacy. The only outdoor lighting application chromaticity coordinates, if their SPDs maticity coordinates of a set of standard differ then the SPDs of the reflected light patches or color swatches when illuminated where high CRI is important is architectural will also differ. Moreover, the SPDs of by the light source you are testing and by a lighting, such as wall washers and floodlights reference light source. These used to illuminate façades and landscapes. A 1.0 standard patches have spe- low CRI in an architectural application can 0.9 cific spectral ref lectance significantly detract from the aesthetics of an Incandescent 0.8 distributions, meaning the illuminated building or landscape. 0.7 In indoor lighting, CRI is particularly percent reflectance at each 0.6 LED important in residential, retail, and restauwavelength for each patch 0.5 is specified. Specifying the rant lighting. Color rendering in office envi0.4 chromaticity coordinates ronments is of less importance, because Fluorescent 0.3 of the patch is meaning- office lighting is designed to provide the best 0.2 less without specifying a lighting for performing tasks and less so for 0.1 0 light source illuminating aesthetics. 500 550 600 650 700 750 400 450 LED-based retrofit lamps and to a lesser the patch or more precisely Wavelength (nm) specifying the source’s SPD. extent SSL fi xtures are starting to make FIG. 2. SPDs of 3000K fluorescent and Incandescent CRI uses fourteen patches inroads into the residential lighting market. lights compared with a white LED. in all. Eight are used to For this market penetration to continue, the derive the actual CRI value cost of the LED lamps and fi xtures must the reflected light will most likely not be (see sidebar – Calculating CRI) and the continue to come down, while the quality metamers of each other and consequently additional six provide individual measures remains high. The higher cost of LED lightwill appear to shift in color at least slightly for specific colors of interest. The patches ing products compared to CFLs and incanif not dramatically. were chosen to be representative of com- descent bulbs can be offset to some degree Color rendering is of particular impor- mon materials (Fig. 3). by the long lifetime of LEDs and by the concolor as a 3000K incandescent lamp, even though the SPDs of the lamp and the LED mixture are vastly different. As long as the cone responses to the two SPDs are identical, then the two sources will look identical in color. Th is phenomenon is called metamerism, and is our second principle of color vision. Any two or more SPDs that have the same chromaticity coordinates are metamers of each other.

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technology | COLOR SCIENCE tinuing increases in LED energy effi1 Photopic ciency. The quality of LED products 0.9 curve Phosphor though involves more than just reli- 0.8 Blue LED ability. The quality of the light pro- 0.7 duced by an SSL lamp or fi xture is 0.6 also important, especially to resi- 0.5 dential customers. The quality of 0.4 light in SSL is essentially the color 0.3 0.2 rendering quality of the LEDs them0.1 selves. Since CRI is our only objec0 360 410 460 510 560 610 660 710 760 tive standard to quantify color renWavelength (nm) dering, it becomes an important product specification along with FIG. 4. SPDs of the blue light and phosphor of a typical reliability and luminous efficacy. 4500K white LED with a CRI of 80, overlaid on the

electrical power in watts. For a typical blue InGaN LED, the efficiency is 30-35%. Despite this high efficiency, blue LEDs have very poor luminous efficacy because the eye is not very sensitive at blue wavelengths. Indeed eye sensitivity is what drives the use of efficacy measured in lumens per watt as the primary figure of merit rather than efficiency. The emission spectrum of the phosphor, however, lines up well with the eye spectral response curve, V(λ) and consequently most of the luminous efficacy of a white Photopic Curve. Achieving high CRI with LEDs LED is due to the yellow light emit1 LED manufacturers often face comted by the phosphor and very little peting goals, such as cost and per- 0.9 due to the blue light passing through formance. Manufacturing high CRI 0.8 the phosphor (Fig. 4). Photopic curve LEDs with high luminous efficacy 0.7 In fact if we weren’t concerned especially for warm color tempera- 0.6 with color rendering or having the tures is one such challenge. The rea- 0.5 chromaticity coordinates of the LED son for this has to do with how white 0.4 fall close to the Planckian curve, we 0.3 LEDs actually create white light. could make a super high luminous 0.2 White LEDs are actually blue efficacy LED by using a phosphor 0.1 LEDs coated with a phosphor matewhose emission spectra matches the 0 400 450 500 550 600 650 700 750 rial. The phosphor absorbs a portion V(λ) curve as closely as possible and Wavelength (nm) of the blue light from the LED with then making the phosphor layer thick the rest passing through the phos- FIG. 5. SPD of Osram's Brilliant Mix delivering a CCT of enough so that all of the blue light phor. Some of this light absorbed by 2700K and CRI of 92 overlaid on the Photopic Curve. from the blue LED was absorbed by the phosphor excites electrons in the phosphor. the phosphor molecules to a higher While matching the SPD of an 1 energy level. As these electrons fall 0.9 LED to the V(λ) curve as closely as back to lower energy states they emit 0.8 possible will make a very efficient Photopic curve photons. The spectrum of the light 0.7 and therefore bright light, it will not emitted by the phosphor is broad- 0.6 make white light. For that, we need band in nature ranging from 500- 0.5 some light on the blue and red ends 700 nm with a peak typically around 0.4 of the spectrum even if the light at 0.3 550 nm. those wavelengths contribute little 0.2 If the phosphor were to absorb all 0.1 to brightness perceived by the eye. of the blue light it would glow yellow. For cool white LEDs this is rather 0 400 450 500 550 600 650 700 750 800 Since it doesn’t absorb all of the light easy to do, by simply letting enough Wavelength (nm) from the blue LED, the transmitted of the blue light from the LED leak blue light and the yellow light emit- FIG. 6. SPD of a dual-phosphor White LED delivering a through the phosphor. ted by the phosphor combine to cre- CCT of 2700K and CRI of 94 overlaid on the Photopic For warm white LEDs, the phosate what appears to be white light. Curve. phor must have enough power at the If the mixture has more blue light red end of the spectrum to create the than white, it will be a cool white warm white CCT. For a 2700K LED, with a high CCT. If the mixture has more yel- architecture is rather efficient for two rea- phosphors with a broad emission spectrum low light from the phosphor than blue light sons. First, blue InGaN LEDs are very effi- are chosen that have a peak emission in the from the LED, it will be warm white with a cient at turning the electrical power sup- 590-630-nm range. Unfortunately these plied to them into optical power. The phosphors also generate a great deal of light lower CCT. luminous efficiency of an LED is defined as beyond 650 nm where the eye has very litEfficiency and efficacy the optical power in radiant watts of the tle response, contributing little to the lumiThe optical performance of this LED light exiting the LED divided by the input nous efficacy of the LED. Th is is why LEDs LEDsmagazine.com

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technology | COLOR SCIENCE with a lower CCT also have a lower luminous efficacy than the cooler color temperature LEDs in the same family.

High CRI, warm CCT The situation is worse when we want to have a high CRI, low color temperature LED – a combination desirable in residential applications. In this case we need even more long wavelength light (600–700 nm) relative to medium and short wavelengths. To accomplish this, the peak of the phosphor has to shift farther towards the red end of the spectrum, further lowering the luminous efficacy of the LED. SSL manufacturers have offered two solutions to this problem. One solution is to add a red LED to a white LED to boost the red content of the spectrum without compromising the efficacy of the white LED. Brilliant Mix by Osram is one example of this. Brilliant Mix actually improves the total system efficacy by using a greenish-white LED with a phosphor that matches the V(λ) curve closely, consequently maximizing luminous efficacy (Fig. 5). The second approach uses a two phosphor system. The main phosphor is shifted towards the blue end of the spectrum and then a second phosphor with a narrower bandwidth and a peak around 610-620 nm is added to boost the red end of the spectrum. Th is second phosphor adds the required power at the red end of the spectrum without wasting too much power at wavelengths above 650 nm (Fig. 6). The first approach can produce CRIs above 90 for 2700-3000K LEDs and still maintain high luminous efficacy. The second approach can achieve CRIs above 95, but with lower luminous efficacy than lower CRI white LEDs.

Beyond CRI CRI as a color rendering metric has several known deficiencies. The most obvious is that it uses only eight spectral reflectance distributions (swatches) to represent the infi nite number of possible spectral reflectance distributions of real objects that can be encountered in real applications. Several replacements for CRI have been proposed such as the color quality scale (CQS) by Davis and Ohno at NIST (www.ledsmaga__________ zine.com/news/7/5/29). Until CQS or another metric becomes the new ______________ color rendering standard, we are left with CRI. The six additional swatches included in the CRI standard can be used to some degree to make up for the small number of spectral reflectance distributions used in the standard. The R9 value which is a saturated red is often of interest for white LEDs since white LEDs often do not render deep reds well due to a shortage of light at long wavelengths. Comparing the R9 values of two LEDs in addition to comparing their CRI values can be instructive, especially for applications where the color rendering of red is important. There are also applications where a CRI approaching 100 may not be desirable. Th is may even be the case in residential, retail and restaurant lighting where high CRI is assumed to be essential. For instance, in some situations you may want LED lighting that increases the saturation of colors. CRI does not discriminate between color rendering shifts that make colors appear more desaturated or more saturated. All color differences between the test and reference sources are treated equally. It is well known that in digital photography we prefer photos with more saturated colors. It is rather standard practice today to increase the color saturation of digital photos using image processing software.

FEBRUARY 2013

Calculating CRI The CRI of a light source is calculated by comparing the chromaticity coordinates of eight standard patches or color swatches when illuminated by the light source in question (the test source) and by a reference light source. The test patches are not actually illuminated by either the test or the reference source. Instead the chromaticity coordinates of the light that would be reflected off of each patch by each sources is calculated by multiplying the SPDs of each source by the spectral reflectance distributions of each patch. The spectral reflectance distributions of the eight patches were chosen to be representative of common materials. The metric used to quantify the color differences under the test and reference light sources is the Euclidean distance in the CIE 1964 color space,ΔΕCIEUVW , with chromaticity coordinates, U′, V′, and W′. An additional six patches are also tested individually and reported separately, providing supplemental color rendering information for those colors. The steps in calculating the CRI of a source from its SPD are as follows: • Determine the CCT of the test source. • Generate the SPD of the reference source. • If the CCT of the test source is less than 5000K then use the SPD of a blackbody radiator with the same CCT as the test source. • If the CCT of the test source is greater than 5000K, use the SPD standard illuminant D with the same CCT as the test source. • Calculate the SPD of the reflected light for each of the eight spectral reflectance distributions of the color swatches for both the test and reference sources. This is done by multiplying the SPD of each source by the spectral reflectance of each swatch on a wavelength by wavelength basis. • Find the x, y chromaticity coordinates of the reflected light and then convert to U′, V′, and W′ chromaticity coordinates of the CIE 1964 color standard. • Apply a “von Kriess transform” to the U′, V′, and W′ values to account for chromatic adaptation by the human visual system. • Calculate the ΔΕі= ΔΕCIEUVW color differences between the test and reference sources for each color patch. • Calculate the specific color rendering index for each patch by, Rі = 100 - 4.6ΔΕі • Average the eight Ri values to arrive at Ra, which is the CRI value for the test source. ◀

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technology | COLOR SCIENCE Increasing color saturation

1 Similarly, it may be possible to alter Photopic Th is fact suggests that we may pre- 0.9 the SPD of LED lights in such a way curve fer lighting that increases color sat- 0.8 to enhance the appearance of specific uration. By enhancing the amount 0.7 items such as food in restaurants and of light at key wavelengths in the 0.6 in grocery stores. LED technology sources’ SPDs, we could increase the 0.5 gives us the tools for the first time to color saturation or chroma of spe- 0.4 tailor the SPD of light sources at least 0.3 cific colors and in the process reduce to some degree. How this flexibility is 0.2 the CRI. With LEDs, this is easy to used in new applications over the next 0.1 imagine. If we wanted to enhance few years will be exciting to watch. 0 400 450 500 550 600 650 700 750 the primary colors we could mix in The tradeoff between CRI and Wavelength (nm) additional red, green and blue light luminous efficacy is currently a major from red, green and blue LEDs along FIG. 7. Adding a red LED (640 nm), a green LED (525 focus in the industry. As LED lumiwith a typical white LED (Fig. 7). nous efficacies continue to improve, nm) and a blue LED (460 nm) to the white LED shown In the example in Fig. 7, red, green in Fig. 6 results in a 5500K light with a CRI of 81. Reds LEDs will enjoy an even greater comand blue LEDs are added to the and greens and purples will appear more saturated petitive advantage over competing warm white LED depicted in Fig. 6, under this light than under the light in Fig 6. technologies such as CFLs. At that resulting in a 5500K CCT with a CRI point the marginal return of further of 81. Although the CRI drops significantly unchanged. These results only apply to the increasing LED luminous efficacy will make it does so because the saturation of the color particular swatches use in the CRI calcu- trading some of that efficiency off for higher swatches in the CRI calculation increases lations. It is practically impossible to pre- CRI a more attractive option. Phosphor techwith the exception of swatches TCS02 (yel- dict how swatches with different spectral- nology should also continue to improve, low) and TCS06 (light blue). The saturation reflectance characteristics would render reducing the need to tradeoff luminous effiof both of these swatches remains largely when illuminated by such a light. cacy for higher CRI.

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LED manufacturing | LARGE SUBSTRATES

Manufacturing LEDs on large diameter substrates: What’s the holdup? A transition to 6- or 8-in wafers will ultimately deliver lower-cost LEDs, although as MARCUS WEDDLE discusses, the industry must overcome technical and logistical challenges.

n the search to cut the costs of manufacturing LEDs, switching to large diameter (6-8-in, 150-200-mm) substrates is often brought up as a key solution. In fact, it is mentioned so often that one might assume a mass transition to large diameter has already occurred. Such a transition has been slow to happen due to both technical and logistical challenges. But as we will discuss, the advantages will ultimately be significant enough that the LED manufacturers will move to larger substrates, reduce component costs, and further accelerate the adoption of solid-state lighting (SSL). Analysts are predicting that for 2013, less than 20% of production will be on 6-in wafers, with 8-in not even showing up in significant numbers this year. Even three years from now, large diameter is only predicted to be breaking the halfway point of all substrate sizes. This may come as a surprise because the demand for large diameter should be very high – it has often been cited as a fundamental cost saver to drive down LED chip prices. With the industry-wide search to drive down cost significantly, and large diameter seen as a key way to accomplish this, why aren’t more chip producers making this switch? To answer this question, we will look at three areas. First, what are the true benefits of large diameter? Second, if the benefits are truly great, then why aren’t more manufacturers switching? Finally, we’ll look at some of the potential disruptions that might bring quicker large diameter adoption, such as c-axis CHES (controlled heat extraction system) technology – along with the prospect of 8-inch substrates.

More LED chips We’ll begin by looking at the main advantage of moving to larger wafers – more LED chips. Yes, this is the biggest advantage, but it’s also unfortunately often overstated in this way: a large diameter 6-in wafer has nine times more surface area than a 2-in wafer on which to form LED chips (Fig. 1). While the prior statement is certainly true in regards to the simple surface area of the wafers, the suggestion that you get 9× more

zone, LED chip shape and size, and MOCVD reactor layout. We’ll explain these one at a time, then feed them into a true comparison simulator that will give us a much more reasonable look at the number of LED chips supported by various wafer sizes.

Exclusion zone

We will first look at what’s called the exclusion zone on a wafer. During epitaxy, LED material is not properly formed in this area, meaning these chips shouldn’t be counted because they will not result in good LEDs. For our LED chip calculator, we 6 in are using an industry standard 3-mm exclusion zone, which is shown as red chips in Fig. 2. Note that the chips 8 in 4 in on the extreme edge of the wafer – that are actually hang2 in ing off the wafer if they were full rectangles – are not going to be counted at all for our simulation. One important characterisFIG. 1. Small- and large-diameter sapphire cores. tic of the exclusion zone is that chip throughput by simply using 6-in wafers it is 3-mm from the edge regardless of wafer sounds too good to be true – and it is. What’s diameter. This fact means that the large the real story? In order to answer that, we diameter wafers have larger exclusion zone need to look closely at the layout of LED chips, areas. However, as a percentage of the total both on the wafer and as a group of wafers in wafer surface area, the large wafers have a the MOCVD (metal organic chemical vapor smaller proportion of their area in excludeposition) reactor where LEDs are formed. sion zones. In addition to 6- or 8-in wafers simply So you can see how a 6-in wafer that has being larger, we have to consider several other 9× more gross surface area actually has more factors to get a true picture of the benefit of than 9× more net area (gross area minus “more LED chips.” These factors are exclusion exclusion zone). The advantage results in 6-in wafers having 10.3× more net area, and MARCUS WEDDLE is Marketing Manager for ARC Energy, based in Nashua, New Hampshire. The 8-in wafers having 18.8× more, both as comcompany manufacturers CHES sapphire crystal growth furnaces and processing systems for the pared to a 2-in wafer. LED, SOS, and optical/commercial industrial markets. We also have to account for the rectanguLEDsmagazine.com

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LED manufacturing | LARGE SUBSTRATES lar footprint of LEDs. They don’t perfectly fit in the round shape of the wafer – some LEDs will be lost by partially crossing into the exclusion zone. In a similar way to the exclusion zone, these losses are a higher percentage of the total for the smaller wafers. The final advantage is shown in the chart in Fig. 3 that is based on 45x45mil (thousandths of an inch) LEDs, including the spaces between chips. The result is slightly higher gains in chip count compared with area – 10.9× for the 6-in and 19.8× for the 8-in wafers.

rectangle, the advantage for 6-in wafers increases to 58%. Exclusion zone So fa r we have (Black ring) focused on comparing 2-in to 6-in wafers, but Gross surface area we should discuss other 4× 9× 16× advantage over 50 mm sizes as well. Today’s Net surface area LEDs are also made on 4.4× 10.3× 18.8× advantage over 50 mm 3- and 4-in wafers in Net LED chip count 4.6× 10.9× 19.8× large numbers. What advantage over 50 mm is the relationship with FIG. 3. Larger wafers greatly increase the number of LED these other sizes? Movchips produced per wafer. ing from 2-in to 4-in MOCVD reactor layout only gives 14.7% advanAt this point, we’ve seen that a 6-in-diameter reactor configuration, 56 2-in wafers can be tage, using a standard layout of 14 4-in wafer actually holds slightly more than the loaded. In the same reactor only eight 6-in wafers in the reactor. The gain from 4-in to often-quoted 9× more LED chips compared wafers will fit. That’s a ratio of 7:1 in favor of 6-in is much more significant at 35.2%. to a 2-in wafer. But now we have to consider small diameter. For 8-in substrates, the advantage is a that LEDs are grown in groups of wafers in So to simply break even in the final count, very large – 77% more LED chips over 2-in – an MOCVD reactor. each 6-in wafer would need to hold 7× more and that is only from the five 8-in wafers that The LED epitaxy process is one of the most LED chips than a single 2-in wafer. How- can fit in a typical MOCVD reactor. Comparexpensive and time consuming of all the ever, we’ve already seen that a 6-in wafer ing a move from 6-inch to 8-in directly, there has almost 11× more is a 14% gain. LED chips. Put in other We now have an accurate view of the terms, the 6-in config- advantage large diameter brings to the LED Chips not counted uration results in 55% chip count: 55% more for 6-in and 77% for more LED chips (1.55×). 8-in. While these are impressive numbers, This is the final true one factor we haven’t taken into account in Chips counted in exclusion zone advantage we’ve been our LED chip simulation is LED chip yield. looking for. While this We will look at this important factor next. is much less than the 9× (900%) figure that Higher yield 3-mm exclusion zone edge we started with, it is Each step in the manufacturing process of still a very significant an LED chip has a yield loss, from the prepaimprovement in the ration of substrates through chip packaging. number of LED chips The yield losses at each step add up and conFIG. 2. LED chips in the exclusion zones along the edge of you get for the same tribute to a significant portion of the fi nal wafers are not usable. cost of time and money chip cost. There is therefore a great deal of for an MOCVD run. You focus currently on improving yield in all of steps that go into the final delivery of an SSL can compare a typical MOCVD layout for these areas. product. The input is a group of wafers, and small and large diameter wafers and their Switching to large-diameter LED manuthe output is thousands of LEDs on those respective chip counts in Fig. 4. facturing has been linked to yield improvewafers. What we are seeking to answer is ment in a number of stages of the manufachow switching to large diameter will change LED chip size turing process. The potential benefits come that LED count after the epitaxy process. Of We do need to consider another factor, and both directly as the larger wafer size is a course, yield – a measure of chips that func- that is LED chip size. For our calculations more uniform surface for epitaxy and indition correctly – matters too, but we will look we’ve used 45×45-mil rectangles, includ- rectly through the use of better manufacturing the street width, or spaces between the ing equipment and techniques. While yield at that later. We’ve already said that you shouldn’t chips. Th is size – around one square mil- can be a complex subject, we will briefly look expect the chip count you get after epitaxy limeter – is typical for high-brightness at some highlights of the possible benefits. to jump by a factor of nine, and now we’ll LEDs and is therefore a good comparison. One of direct yield benefits of larger see why. The primary reason is the fact that However, as chip sizes increase the advan- wafers comes during epitaxy. In the MOCVD so many more small-diameter wafers can fit tage for large diameter wafers also increases chamber, any physical disturbances, such in the reactor chamber. In a typical MOCVD slightly. For example, if you use a 60×60-mil as wafer edges, can disturb the gas flow and

FEBRUARY 2013

2 in

4 in

6 in

8 in

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LED manufacturing | LARGE SUBSTRATES Small diameter Large diameter reduce yield. Larger wafers nies moved ahead despite these conditions can help here because there Overlay of 150 mm and are today prepared for a rapid increase 150 mm 200 mm 8 pockets 5 pockets showing surface are fewer edges and more in production as demand grows. area advantage undisturbed surface area. Technology barriers The resulting higher yield 50 mm The second barrier to the adoption of large during this expensive step 56 pockets diameter substrates is a group of technois an important advantage. logical hurdles. It begins with challenges in The second component of sapphire crystal growth – the fi rst step in improved yield comes from 56×50 mm (2") 8×150 mm (6") 5×200 mm (8") creating substrates. As you can see in Fig. access to modern process 5, today’s sapphire for HB-LEDs is typically control and automation 130,288 mm2 147,796 mm2 Net surface area 88,274 mm2 grown on the a-axis, even though HB-LEDs tools, which are designed require c-axis wafers. To get c-axis wafers around large-diameter Surface area gain 48% 67% from a-axis sapphire boules, a core must be wafers and have been per- vs. 50 mm taken sideways – wasting a large part of the fected in IC manufactur- Count of 45×45 mil 62,944 97,600 111,280 sapphire. ing. Today’s commonly LED chips Today’s a-axis sapphire growth techused small-diameter man- LED chip count gain 55% 77% vs. 50 mm nologies also result in defects that cannot ufacturing techniques use be avoided when coring for large diameter manual processes, requir- FIG. 4. The number of wafers that fit in an MOCVD reactor applications. The volume of a 6- or 8-in core ing many human interac- ultimately gates the advantage of larger wafers. is so large that the defects become unavoidtions, and lack sophisticated tracking that could spot yield issues. through large-diameter wafer production, able and the cores must be shortened or Many experts have pointed to a general see the article “LED wafer and automation scrapped. The total losses from sideways corneed to move from a research-style produc- standards are on the fast track, ready for ing and defects waste over 80% of the material. For 8-in applications, the waste is over tion environment to a true mass production more industry feedback” (www.ledsmaga__________ 90% and the production costs double. environment. Let’s look in a little more detail ________________ zine.com/features/8/10/9). Another barrier caused by a-axis growth at what this means. is that the resulting wafers have a variaAutomation primarily refers to the use of Market conditions machines to handle and transport wafers – At this point, we’ve seen how switching to tion in stress and strain across their surremoving the human element. Wafers can be large diameter wafers can create more chips face. Because the wafer is from a sideways moved faster and with less damage through per MOCVD run and improve yield in sev- core of the boule, and the boule is grown automated machines instead of being hand eral areas. Yet the industry Coring with defects cannot carried. The benefit is a combination of fewer this year is still predicted to be avoided with large diameter skilled operators required, less loss of wafers produce over 80% of the LED a-axis growth due to mishandling, and quicker movement capacity using small-diameDefects in the core result lost wafers (red area) ter substrates. Why? The reathrough the manufacturing steps. In addition to more automation, the use sons come from two factors: of more modern tools brings better process difficult market conditions control. Process control is the use of data and technological challenges c-axis 150 mm cores coring analysis to detect and predict problems in supplying large diameter that cause yield losses in any area of the substrates at a competitive production process. Th is involves a track- cost. The price of 2-, 3-, and 4-in ing and analysis of the substrate throughout the process, extending back to the crys- wafers has dropped dramatOlder technology tal growth stage. Process control also takes ically in the past two years a-axis boule into account the analysis data recorded by due to an oversupply condiDefect losses reduce utilization tion and lower-than-expected the various production tools. to less than 20% The use of process control is often cited demand. At the same time, a as a necessary step in advancing the LED step in the manufacturing FIG. 5. Taking large sapphire cores from a-axis boules industry. As with automation, the tools process called PSS (patterned results in significant material losses and more defects. needed for implementing process control are sapphire substrate) has designed around large-diameter substrates, increased the performance of LEDs. These along the a-axis, the wafer itself has a long so the benefit to switching goes beyond just two factors made staying with small diam- growth time signature across its surface. more LED chips. For additional informa- eter an attractive option while waiting for Th is becomes significant during epitaxial tion on the industry’s move to improve yield higher demand. However, some large compa- growth when the wafer is heated. LEDsmagazine.com

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LED manufacturing | LARGE SUBSTRATES As you can see in the Fig. 6, the wafer will bow in an uneven pattern or a warp. Th is warping is very difficult to counteract by the MOCVD engineer and has caused several attempted workarounds, including a move to thicker wafers and the use of stress-relieving layers. These techniques add to the production cost and complexity. Without counteracting the warp, the result during epitaxy is lower LED chip yield. The last technology barrier is in the slicing and polishing of the wafer and application of PSS techniques. Slicing and polishing are difficult processes and must be done well to generate good yield during epitaxy. Because the large wafers are 9-16× larger, the difficulty increases significantly. PSS application faces a similar challenge, with the additional obstacle that the pattern can only be seamlessly applied to a limited size area smaller than 6 in. In order to get PSS on a 6-in wafer, a stepper (a semiconductor manufacturing tool) must apply multiple patterns, which is common in the silicon industry. However, for HB-LEDs the edges of the multiple pattern applications must be closely matched or LED yield will drop. This accuracy requirement is proving to be very challenging. These barriers of market conditions and technology challenges have created multiple limitations for the mass adoption of largediameter substrates. In the future, the market demand will require the throughput and yield only available using larger substrates, and as a result the technology challenges will be overcome. As proof of the possibility of overcoming the challenges, several tier-1 manufacturers have already made the switch and are positioned with an advantage over the majority of the industry.

Potential substrate disruptions It is certain that HB-LED manufacturing will ultimately move to large-diameter substrates. The question is how quickly, and what material will be used for the substrates? In this last section we’ll briefly look at potential answers to these questions. As we said at the beginning, adoption of large-diameter is currently low and predicted to take years to complete. However, advances in alternative substrates to traditional sapphire may accelerate this adoption or carve out niche channels for some compa-

FEBRUARY 2013

A small number of LED manufacturers are even in production on each of Variation in stress these substrates, yet not and strain as a cost-effective alterduring growth native to sapphire. Each of these alternatives has certain advantages over sapOlder technology phire, yet multiple breaka-axis boule throughs are needed for one of them to significantly displace sapphire. Of the alternative subWafer heated during epitaxy: strates, current predic2D cross-section tions give silicon the best side view chance for success. Because LEDs have such a broad potential 3D view market, there will be room for these alternative FIG. 6. Wafers from a-axis boules are subject to warp substrates along with sapduring the MOCVD process. phire remaining predominant. For example, an nies. But fi rst we’ll focus on sapphire. advantage GaN substrate brings is higher The main challenges we noted were the performance per chip – albeit at very high low material utilization due to a-axis growth cost. This substrate may find a niche where a and the high level of defects that make larger single bright LED chip is desired or required. wafers expensive. There are alternative The next diameter past 6-in is the 8-in growth technologies that can grow directly wafer. These wafers give another dramatic on the c-axis for much lower waste. In addi- gain in LED chip count and further opportution, growth technologies that avoid signif- nities for yield improvement. Yet the barriers icant defects are also available. we examined earlier are the same, with the Sapphire grown with these characteristics addition of the sapphire substrate costs douof c-axis growth (also called on-axis growth bling over 6-in using a-axis growth methods. for LED applications) and low defect levels Therefore the prediction is that one of these are very well optimized for large-diameter applications. As you can see in Fig. 7 depicting c-axis CHES technology, the problems of low material utilization and high defect levels are both solved at once, with the addi75+% material utilization tional benefit of a near net shape boule. The result is over 75% utilization for both 6- and 8-in applications. In addition, the problems of warp during epitaxy that we saw from a-axis-grown sapphire are reduced as the c-axis CHES wafers are grown with a single time signature across CHES c-axis growth direction their surface (Fig. 8). Because of these advanand coring tages, it is expected that as more manufacturers move to large-diameter applications, the growth technologies will also transition CHES to c-axis, low-defect-level growth. c-axis boule Alternative substrates to sapphire, such as silicon, silicon carbide, and gallium FIG. 7. C-axis sapphire boules improve nitride (GaN) are also being researched. material utilization and minimize defects. Wafers cored using older technologies have a long growth time signature and variations in stress and strain

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LED manufacturing | LARGE SUBSTRATES

No stress and strain due to a single time signature of growth

CHES c-axis growth and coring CHES c-axis wafer

Older technology a-axis wafer

2D cross-section side view 3D view With c-axis growth, wafers exhibit less bow and warp during epitaxy

FIG. 8. C-axis wafers exhibit less strain and warping during epitaxy.

alternative technologies (sapphire grown on c-axis, silicon, or another substrate) will become dominant for 8-in wafers and beyond.

Obstacles and benefits In summary, we found a move to large-diameter-based LED manufacturing provides a 55% increase in LED chips per MOCVD

run using 6-in wafers, and a 77% using 8-in wafers. In addition to more chips, the yield would increase throughout the manufacturing process due to better epitaxy yield, automation, and process control. The reason these advantages haven’t become common except with the largest LED manufacturers are several market and

technology barriers. These include a-axis sapphire growth technology, a depressed market, and the use of PSS. But new c-axisgrowth technology provides an optimized path to supplying large-diameter sapphire substrates. Other substrate materials, such as silicon, will likely fi nd niche uses with some manufacturers. The advances of larger wafers will continue to the next step of 8-in. Large diameter has already been proven by large tier-1 manufacturers as an important component in reducing costs and increasing performance of HB-LEDs. See “Philips Lumileds announces workhorse Luxeon T LED family” (www.ledsmagazine. com/news/9/12/7) for an example. Yet many companies are staying with small diameter wafers until the next demand wave comes. However, companies that are planning ahead to gain a competitive edge – as is possible with large-diameter LED manufacturing – will be more efficient, more flexible to meet demand, and find success in the future.

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Thomas Research Products SSL Solutions Faster Than The Speed Of Light

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financing | SSL PROJECTS

Energy Efficiency Financing scheme lights up the path to green savings A UK-based financing scheme provides funds to cover the upfront cost of lighting equipment, with repayments aligned with energy-bill savings, as DARREN RIVA explains.

ighting can represent a significant proportion of energy consumed in non-domestic buildings, typically accounting for 20% to 55% of the total electricity consumption on a commercial site. Each year in the UK, non-domestic lighting is responsible for around 24 million tonnes of CO2 emissions according to the Carbon Trust. Improving the energy efficiency of lighting can therefore yield significant cost savings, while reducing the environmental impact. By deploying efficient lamp technologies such as LEDs, CFLs and energysaving halogen lighting, cost reductions of up to 80% are possible compared with traditional lamp technology. Intelligent lighting controls can be used to further reduce energy consumption, usually between 30% and 50% in a typical office environment. Clearly, there is a compelling case for moving to more energy-efficient lighting systems both from the fi nancial and environmental perspectives. Nevertheless, many companies are hesitant to take the first step, largely because they are reluctant to spend their capital reserves or simply lack access to affordable funding. According to the Bank of England, the annual rate of growth in the stock of lending to UK businesses was negative in the three months to August. The stock of lending to small and medium enterprises (SMEs) and large businesses also contracted over this period.

Efficiency Financing scheme (EEF). The scheme is designed to provide financing for organizations acquiring energy-efficient equipment, with affordable monthly payments designed to match – and to be offset by – the average monthly savings on energy bills. In some cases, the value of the energy savings can be greater than the monthly fi nance payments, allowing the end customer to be cash-flow positive from day one. Suppliers of energy-efficient equipment can also apply to become a recognized supplier of the scheme, which in turn will allow them to integrate the financing offer into their overall sales propositions. Th is removes the obstacle of large up-front capital investment for customers, and helps suppliers to close more deals as efforts can be focused on providing the best solution, rather than being constrained by businesses facing capital budget restrictions. In addition, fast payment of invoices for the energy-efficient equipment are made by SFS to recognized suppliers directly – usually within a day of receipt of correctly completed documentation – meaning improved cash flow for the suppliers.

Boosting green investment appetite

How the EEF scheme works

To help businesses make green investments in a tight credit environment, the Carbon Trust and Siemens Financial Services Limited (SFS) have initiated the Energy

Financing can start from as little as GBP1000 and go up to as much as hundreds of thousands of pounds, even millions. Each application (which must be from companies with at least three years of trading history) is assessed on its own merits and monthly payments are adjusted to match or be less

DARREN RIVA is the Head of Financing for the Energy Efficiency Financing (EEF) scheme. LEDsmagazine.com

than a customer’s anticipated energy cost savings. This is usually arranged over terms between one and seven years, although in selected cases this can be for longer periods. Where possible, the scheme wraps everything into a single financing package under a loan, lease or hire-purchase arrangement. This includes the cost of an energy-efficiency assessment, the equipment itself and installation. Customers can also include other aspects, such as service into their monthly payments, as well as negotiating upgrades and addons in the future as their needs change. Financing can be arranged directly by the customer with SFS or through the scheme’s recognized suppliers. Prior to fi nancing being approved, normal checks for credit acceptance will be conducted and an energysaving assessment will be undertaken by experienced specialists at the Carbon Trust, giving businesses the assurance that the expected carbon reduction, and fi nancial savings over time, will match or exceed the finance payments.

Reaping financial gains with EEF The EEF scheme has already helped many organizations reap financial savings and reduce their carbon footprint. Nailcote Hall, a hotel situated in Solihull, Warwickshire, has leveraged this specialist financing to work on a re-lamping project, converting 670 regular halogen light fittings (which use between 35-100W) into LED light fittings using only 7W of power. The GBP30,000 ($ 48,000) investment should bring a saving of approximately FEBRUARY 2013

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financing | SSL PROJECTS GBP12,000-14,000 a year, with a return on investment (ROI) of around two and a half years. As the monthly payments are less than the monthly energy savings achieved from the new lighting, the hotel is cash-flow positive from the very start of the project. The North East Convenience Stores, a company with 18 outlets located from Blyth in Northumberland to Eston in Middlesbrough, has invested approximately GBP50,000 to upgrade one of its premises with financing from the EEF scheme. By replacing all refrig-

eration units and chillers with an energy-efficient, remote open-deck refrigeration system, and at the same time replacing the existing lighting with LEDs, the electricity bill has been cut by 40% and payback is expected in less than two and a half years.

Paving the way for the green journey With the establishment of the EEF scheme, a large capital outlay is no longer a pre-requisite for green investments by businesses. Organizations can now easily afford to

upgrade their lighting as well as other equipment to more energy-efficient alternatives, thereby cutting unnecessary overhead and strengthening their competitive position. For equipment suppliers – such as lighting manufacturers – who can offer technical expertise as well as a financing option such as the EEF scheme in their sales proposition, the commercial advantage they have over their peers will no doubt benefit their business and help make the green journey a much smoother experience for their customers.

LINKS

Next Generation Streetlights guide covers LED technology to financing www.ledsmagazine.com/news/9/12/13 Europe provides funds and updates legislation to stimulate growth in SSL www.ledsmagazine.com/features/9/9/3 DOE Consortium introduces financial tool for LED street lights www.ledsmagazine.com/news/9/2/12 Bridgelux and Chevron partner on LED street lights, announce California installations www.ledsmagazine.com/news/9/3/1 European Commission initiates public consultation on LED lighting www.ledsmagazine.com/features/9/2/2 Appalachian launches smart LED street light and SSL Energy Solutions financing www.ledsmagazine.com/news/8/10/6

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design forum | DRIVING STRINGS

Fixed-frequency and quasi-resonant flyback controllers drive large LED strings FRED SAWYER and MLADEN IVANKOVIC explain how to drive large LED strings, including RGB

implementations, for high-lumen-output applications.

hile several IC suppliers today off er dedicated switching ICs designed specifically for LED applications, the majority of these devices do not support DC-bus output voltage levels greater than 45V, with a few devices using advanced process technology that support up to 60V. The output-voltage limits the number of LEDs that can be driven in a series confi guration where current is shared equally among each LED in the string. The limit to LEDs in a string can both limit the total lumen output of a solidstate lighting (SSL) design or the ability to implement a color mixing scheme – especially given that white LEDs have larger forward voltage (Vf) values than red LEDs. Driver developers, however, can use fi xedfrequency and quasi-resonant (QR) flyback controllers to implement the DC-DC conversion stage and support higher DC voltages and more LEDs. Color mixing is one of several cases when the need to support output voltage in excess of 60V may be desirable. For example, a 72V output can accommodate a string of 19 white/blue/green LEDs or 24 red LEDs. Alternatively, a manufacturer may need to accommodate a wider range of DC bus voltages derived from the converted AC line. For example, consider the need to accommodate universal AC input voltages (85V270V) for use in a product sold globally. Let’s examine power-stage designs that can accommodate comparatively high DC FRED SAWYER is a Senior Staff Field

Applications Engineer, and MLADEN IVANKOVIC is a Senior Application Engineer

at Infineon Technologies.

FEBRUARY 2012

85 – 270 VAC

CBulk

Snubber

Converter DC output

CVCC HV

VCC

Startup cell

PWM controller current mode Precise low tolerance peak current limitation

Power management

Gate CS RSense

Control unit Active burst mode Latch off mode Auto restart mode

FB GND

ICE3BS03LJ (Latch & jitter)

FIG. 1. Fixed-frequency flyback controller.

bus voltage values. We will discuss a QR controller with minimal turn on losses and subsequent low electromagnetic interference (EMI). And we will discuss both fi xedfrequency and QR controller designs with an added transistor to support dimming. SPICE (Simulated Program with Integrated Circuit Emphasis) simulation results will demonstrate each concept and extract the basic features of the QR controller, including valley switching and current limit, to prove the concept. Typical applications for f lyback controllers are in transformer-isolated AC-DC applications. These devices also possess features that allow them to be utilized effectively in DC-DC buck, or step-down, applications where supply voltages for accommodating larger strings of LED’s (50V and higher) are necessary. Additionally these controllers can be configured to support other useful features including dimming and programmable current capability.

Fixed-frequency and QR controllers Both the fi xed frequency and QR controllers (Figs. 1 and 2) contain an embedded power cell or start-up cell capable of working with high input-voltage values. Before the AC line voltage is fully applied and has stabilized, these internal cells provide a stable supply voltage to the IC so it can perform the necessary regulation. This is achieved by an internal switch that charges up the capacitor on the VCC terminals before the stabilization of the line voltage. Once the line voltage stabilizes, the startup cell becomes inactive unless power is interrupted. Under normal AC line conditions the IC derives its VCC power from a rectified AC source voltage. For either controller, voltages in excess of 270V can be supported at the IC input. Th is supported input voltage value is far greater than that supported by the typical DC-DC, fi xed-frequency switching regulators that exist today for LEDs. As previously noted, most are only capable of handling maximum supply voltLEDsmagazine.com

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ages of 60V (and more typically 45V). A simple buck converter uses a fi xed frequency controller that supports a DC input. The driver acts as a constant current source, so that regardless of the number of LEDs connected each diode will see the same current value. The transistor provides the reference voltage for the feedback and is matched with the current-sense resistor in order to achieve the desired output regulation. Using the fi xed frequency device is a quick and easy way to implement the DC-DC buck converter concept. Its drawback is that as a fi xed switching frequency device it exhibits greater EMI than other available alternatives. Moreover the maximum supported duty cycle for these controller devices is between 80-85%. Th is means that the output voltage for the LED supply can only be 80-85% of the input voltage. As an example a 60V DC input bus would be limited to supporting a 48V DC output and 12-15 LED’s.

losses, making this a very efficient switching solution for a DC-DC buck converter application. We shall see in a subsequent example how this solution also accommodates dimming applications. Zero-voltage-switching operation occurs when there is a resonant condition resulting from inductor L1 and the FET output capacitance in the fully off state. Under this condition, capacitor voltage eventually begins to fall and the inductor current goes to zero. We simulated this circuit concept using National Instruments Multisim SPICE software package. Th e inductor current and FET drain waveforms are shown in Fig 3. In this example the input voltage is 100V. The output voltage and Inductor L1 control the rise and fall time of the current. The turn on of the FET is initiated at the valley point once the FET drain to source voltage has been detected to reach its maximum value (100V). During this condition the FET is deemed off and is subsequently switched on by the QR controller. During this phase the inductor current rises and once the peak is reached the FET is fully on. At this point the FET is turned off and the inductor current discharges. The FET is fully off once the inductor current reaches zero and the drain to source reaches 100V.

Quasi resonant advantages For designs having stricter EMI standards and needing tighter differentials between the input and output voltage bus values, a QR device should be employed. The example in Fig. 2 uses Infineon’s ICE2QS03, which contains an integrated start up cell along with a digital frequency-reduction feature. QR operation minimizes EMI by turning on the field-effect transistor (FET) at the output during the zero crossing phase – a technique commonly known as valley switching. Another effect of turning on the FET at the zero crossing phase is reduced turn on CBus 85 – 265 VAC

RVCC

Circuit performance Fig. 4 illustrates the total average power (voltage×current) across the switching cycle and demonstrates how the QR controller concept minimizes losses during turn on.

CVCC

RZC2

Dr1 ~Dr4 HV

VCC

Snubber

DVCC

RZC1

CZC

Do Ws

Lf Cf

Power cell

GND

Control unit

CFB FB

Zero crossing detection Power management Digital process block Active burst mode Protection block Current mode control

Gate driver

Q1 Gate

Rb1 CDS

Rb2 Rovs1

Optocoupler Current limitation ICE2QS03

Rc1

CS RCS TL431

Cc1 Cc2 Rovs2

FIG. 2. Quasi resonant controller. LEDsmagazine.com

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design forum | DRIVING STRINGS Transient analysis

125

Dimming and current programming

In our circuit design, dimming can be implemented by applying a pulse-width modulation (PWM) input to the feedback 75 (FB) pin and replacing the FB resistor with Voltage (V) 50 a photo bipolar junction transistor (BJT) Current (A) placed in parallel with a current mirror 25 transistor such as the BC846. When the paralleled configuration of the transistors 0 is turned on, the FB pin is grounded and -25 there is zero current. 30 40 10 20 0 Turning the transistors off sets the maxiTime (μs) mum current condition for the LED string. FIG. 3. The waveforms depict the QR-switching or valley-switching concept. The yellow Thus by applying a PWM input, the resistrace is the inductor current and the red trace represents the FET drain voltage. tance seen by the FB pin can be changed, Transient analysis 600 We performed average power simulations which adjusts the on this circuit design to determine the efficurrent f low and 500 ciency characteristics of this QR concept. establishes the dimWhile simulation represents only a theming properties. 400 oretical result of what is to be expected Voltage × current As previously men300 it nonetheless provides a good starting tioned, the ICE2QS03 point for evaluating this concept. The QR controller has a 200 Turn on losses analysis was conducted assuming ideal d ig ita l-f requenc yare minimized components (capacitors and inductors), reduction property. 100 so the designer can view the losses that Once lighter load 0 are strictly attributed to the application cond it ion s e x i st , 0 5 15 25 30 10 20 of the QR topology. such as during the Time (μs) K e y f i g u re s f rom t he a na ly si s dimming of the LED FIG. 4. A Multisim analysis shows the average power include an average output power of light engine, the con(voltage×current) over the switching cycle. (96.4579+96.4551)/2= 96.45W and an avertroller subsequently age input power of (99.5510+97.3866)/2= reduces its switch98.46. If you divide the output by the input take into account the effect from non-ideal ing frequency in accordance with the load. we calculate converter efficiency of approx- components and or imperfections in the This positively impacts – reduces – the imately 98%. As noted, this fi gure does not circuit-board layout. switching losses that are associated with the FET and the inductor under light load. Thus the controller operates at optimal efficiency QR switching in the ICE2QS03 for any load condition. A review of the functions performed by the the FET. The controller ultimately uses the Likewise the photo BJT, when ICE2QS03 and each of the IC pins help illustrate CS function and the voltage present at the connected in parallel with the the overall operational concepts discussed in feedback (FB) pin to determine when to switch BC846, can be used to program the main article. the FET off. the current characteristics for The zero current (ZC) pin takes in the The circuit operates by looking at the the driver via PWM control. voltage resulting from the oscillation dictated sensed voltage across the shunt resistor (CS) The PWM scheme provides an by the inductor and FET parasitic capacitance. and the voltage is applied to an internal current effective bias mechanism to Internally, this pin is connected to the zeromeasurement unit integrated inside the IC. The the transistors giving them the crossing detector for to determine the switch-on output voltage from the CS pin is compared properties of a variable resistor time of the FET for resonant operation. with the regulation voltage that is represented which in turn can control the The current sense (CS) pin is connected to by the FB input. Once this current sense current levels. the shunt resistor for primary current sensing voltage exceeds the FB voltage, the output flipAdded safety features externally, and to the PWM signal generator flop inside the IC is reset. As a result, the FET is A further modification to the to in part determine the switch-off time for switched off. ◀ 100

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LEDsmagazine.com

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design forum | DRIVING STRINGS _______________________

R2 R1

C1 0F GND

ZC FB

ICE2QSO3

VCC

Gate

LED1

L1 Q1 BC846

Out

MOSFET

LED2

LED3 LED6 LED4 LED5

TLE4305

Current sense input

Overvoltage protection

FIG. 5. The addition of circuit-protection features can allow the controller to survive a

fault in the LED string. QR design introduces detection and protection circuitry, so that a break in the LED string does not create an overvoltage condition. Th is is illustrated in the block diagram in Fig. 5. Th is design adds the TLE4305, which is a combination voltage and current regulator for switch-mode power supplies. Th is device is used in conjunction with the QR controller to provide the internal reference voltage needed for the current sense. It is an extremely low internal reference voltage (200 mV) thereby facilitating the use of smaller current sense resistors in the application. The QR controller has a zero-crossingdetection (ZC) pin which performs multiplefunctions. First in addition to performing the switch on of the MOSFET, once a valley condition has been detected, it also serves as the output overvoltage detector. In this case, when the output voltage exceeds a specified limit due to a broken LED string the QR controller will undergo a shutdown for protection purposes. The condition is triggered by the TLE4305 which detects the overvoltage condition via sense resistors and an internal reference voltage.

Flyback controller suits LEDs We’ve seen that a fl yback controller can serve efficiently in DC-DC applications where LED lighting is involved. Controllers that contain a high-voltage start-up cell can handle larger DC input voltages than

LEDsmagazine.com

switching ICs specifically designed for LED applications. Th is allows the designer to accommodate more LEDs in a series configuration, ensuring that current is shared equally by all LEDs in a string. The QR controller achieves maximum switching performance due to minimal turn on losses which adds the benefit of reduced EMI. However both the fi xed-frequency and QR controller designs can accommodate dimming requirements by simply adding a transistor to adjust and control the loop’s feedback resistance. The transistor controls the amount of current supplied to the LED string to produce the desired dimming effect. Likewise the driver designer has the option to program the desired current based on the use of PWM to defi ne an operating point that establishes the desired LED current. The designer should also bear in mind that a QR controller enables full use of the available bus voltage because it is not bound to duty-cycle limitations typical in fi xed frequency devices. A significant feature of the QR controller scheme described here is that it also affords the designer optimal efficiency under dimming conditions compared to that offered by a fi xed-frequency controller approach. Under light load conditions, the reduction of the QR controller’s switching frequency minimizes associated losses in the FET and inductor.

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last word

Zhaga helps SSL luminaire makers reduce costs and supply-chain risks ZHAGA CONSORTIUM General Secretary MENNO TREFFERS explains that vendor-interoperable light

engines will allow companies to support broader LED-lighting portfolios with more features.

any companies in the lighting industry are struggling with profitability in the transition to LED-based lighting. Luminaire manufacturers are seeing their R&D costs and stock levels increasing. They are writing off increasing quantities of obsolete stock, and are facing increasing risk of quality problems in the field. Zhaga standards can help with these issues and accelerate the adoption of solid-state lighting (SSL). I spoke with a number of lighting manufacturers who had increased their R&D spending from around 3% of sales in 2006, when they were designing luminaires with conventional light sources only, to 6% of sales last year, when 80% of the total went on developing LED luminaires. Such a high level of R&D spending does not look sustainable for luminaire manufacturers. Costs will have to go down - not just R&D costs, but also the cost of stock, stock obsolescence, and the cost of quality. Why has the R&D cost increased so much? Partly because LEDs change faster than luminaires, and partly because it is challenging to make reliable luminaires that deliver the expected long lifetime. Modular design helps. In a modular luminaire architecture, the LED technology is separated from the optical and mechanical parts of the luminaire. The R&D effort can then be focused on maintaining the LED module, a term that is used here loosely to defi ne the part of the luminaire that contains the LED technology. Most luminaire companies already use modular architectures – this is the only way to develop and maintain a broad portfolio of

FEBRUARY 2013

luminaires. While it may be obvious to separate the LED technology, the choice of make vs buy is less straightforward. Making your own PCB with LEDs is attractive, and the cost is lower than buying the equivalent off-the-shelf module. This will get you luminaires with minimum bill-of-materials (BOM) cost. On the other hand, proprietary LED modules are a burden for the R&D department, and the design and maintenance of the modules will increase your R&D cost. Designing your own LED modules has other pitfalls. It is easy to get started, but soon you will need variants for other color temperatures, light levels and CRI values. Before you know it the R&D department has doubled its number of engineers. Are you better off buying LED modules? Not necessarily. They are more expensive, and their integration into the luminaire still needs careful engineering to make the luminaire reliable. Furthermore, a module that is competitive today may be outdated, or even unavailable, a year from now. The dilemma seems to be whether you should reduce the R&D cost or the BOM cost. And what is the effect on your stock levels, the risk of obsolete stock, and the diversity of your luminaire product portfolio? Zhaga offers a way out of this dilemma. By specifying the interfaces of a series of different LED modules, which Zhaga terms “LED light engines,” Zhaga makes it possible for module manufacturers to supply interchangeable LED

light sources. In the context of Zhaga, two LED light engines are said to be interchangeable when the luminaire manufacturer can use either LED light engine without making any change in the design (mechanical, optical, thermal, or electrical) of the luminaire. Luminaire manufacturers benefit from interchangeability because they can more easily switch from one supplier to another. The availability of a second-source supplier reduces risk. Not only will interchangeable LED light engines be more competitive, they are less vulnerable to supply issues, and that helps reduce stock levels and the risk of obsolescence. A subtle benefit is that interchangeable LED light engines will offer more choice in terms of CRI, CCT, lumen levels, lifetime, color stability, etc. This offers luminaire manufacturers the possibility to play with different performance/ price levels in their luminaire portfolio without increasing their R&D costs. The impact of Zhaga is already visible. For example, suppliers of linear indoor modules have started to offer products with the mechanical dimensions and fi xation specified in Zhaga Book 7, even though that specification has not been published yet. Even if you choose to design and manufacture your own linear modules, it now makes sense to make them compatible with Zhaga Book 7. You may want to purchase these modules later from an external supplier. MORE: www.zhagastandard.org LEDsmagazine.com

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Exhibition & Conference: August 14-15, 2013 Pre-Conference Workshops: August 13, 2013 RIO ALL SUITES HOTEL & CASINO www.theledshow.com

CALL FOR PAPERS The LED Show will feature a comprehensive, in-depth conference program focused on industry hot topics, business solutions, and new technologies. Abstracts are now being accepted for the 2013 conference. We invite you to submit an abstract and share your knowledge, experience and solutions with industry colleagues from around the world. Abstracts for the main conference program of The LED Show 2013 will describe or demonstrate: ! " Visit www.theledshow.com to submit your abstract!

DEADLINE FEBRUARY 15th 2013

For more information on participating at the conference please contact: Karen Gallagher - Conference Manager T: +1 603 891 9304 F: +1 603 579 9030 E: kareng@pennwell.com

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