Power Developer: Micrel

December 2013

Mansour Izadinia Senior Vice President of Micrel

Bridging

the Gap:

How Micrel fuses its resources to achieve power innovation.

Curiosity Rover Power Source

Low Power Converters

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CONTENTS

TECH COLUMN

How to GaN: eGaN FETs for High Frequency Switching

TECH ARTICLE

Using Nuclear Energy to Power the Mars Curiosity Rover

COVER INTERVIEW

Mansour Izadinia - Senior Vice President of Micrel

TECH COLUMN

Perfection in Power: Mini Power Supplies Lower Consumption

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Power Developer

Ho

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TECH COLUMN

ow To GaN: eGaN FETs for High Frequency Switching Alex Lidow

CEO of Efficient Power Conversion (EPC)

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Power Developer The previous columns in this series discussed the advantages of eGaN FETs in high frequency resonant and soft-switching designs were presented. In this installment a return to hard-switching converters is made, but with a push to higher frequencies – beyond the practical limits of silicon technology. One such particular application is envelope tracking. The aim of this article is to show what power and efficiency levels are readily realizable using current eGaN FETs and the LM5113 eGaN FET half-bridge driver and present some new devices to extend their high frequency switching range capabilities.

Concept of Envelope Tracking The idea behind envelope tracking (ET) or sometimes called envelope elimination and restoration (EER) for linear power amplifiers (PA) are not new, but only in recent years has new technology emerged to make ET viable. The technology development is driven by the need for continuous improvements in cell phone battery life and base station energy efficiency as data rates keep rising exponentially [1]. The key to envelope tracking’s ability to improve efficiency lies in the amplifier’s peak to average power (PAPR) requirements [2]. As shown in the conceptual drawing (Figure 1) it is possible to achieve peak PA efficiencies as high as 65% with a fixed supply, but given PAPRs as high as 10:1, the average efficiency is likely to be lower than 25%. Through modulation of the PA supply voltage, this can be improved to over 50% - essentially doubling the efficiency and reducing PA losses by two thirds. This will not only reduce power consumption, but also lower the cost of operation, cooling requirements, size etc. [3].

High Frequency Switchers

The best method for implementing envelope tracking is still under debate. However, to achieve the efficiency requirements, some form of high frequency switcher is required,

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while realizing the required bandwidth likely will require some series or parallel linear element [4]. One practical solution to implementing an ET supply is through multi-phase buck converters (with or without linear element to improve bandwidth). The realizable bandwidth for these buck converters are typically limited to ~1/5th the effective switching frequency, but can be increased through non-linear control techniques [5].

Experimental High Frequency Buck Converters The high PAPR that make ET possible also means that average output voltage is typically between 30% - 50% of the buck converter supply voltage with excursions below and above this average in the multi megahertz range. For device performance demonstration purposes a single phase steady state buck converter running at a similar duty cycle can be used to determine the efficiency and thermal requirements of a multi-phase ET buck converter. Based on the active area of the EPC2000 series eGaN FETs, the most representative ET application would be Digital Video Broadcasting (DVB) transmitters, such as that implemented by ET specialist Nujira. The experimental setup specifications are listed in Table 1. To show the impact of active area reduction, two demonstrators using different sized devices were constructed.

TECH COLUMN

Figure 1: Conceptual PA efficiency vs. output power for fixed supply and ET operation

Table 1: Specifications for experimental high frequency buck converter for envelope tracking

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Power Developer

Table 2: A new family of reduced active area high frequency eGaN FETs

Figure 2: Efficiency and loss results for EPC2001 and EPC2007 based buck demonstrators operating both at 45 VIN, 22 VOUT.

Figure 3: Loss breakdown for EPC2001 and EPC2007 based buck demonstrators operating at full load, 45 VIN, 22 VOUT. (IOUT = 15 A and 6 A respectively)

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TECH ARTICLES The demonstrator switching frequencies were pushed as high as practically possible, given their respective die sizes. The respective efficiency results and loss breakdown are shown in Figures 2 and 3 respectively.

Experimental Result Implications Figure 3 clearly shows how the devices losses are concentrated in the hard-switch control FET and that switching losses are limiting further frequency increases. The smaller devices (higher on-resistance) were capable of a proportional four times increase in switching frequency, although at a significant reduction in output power of roughly 40%, thus requiring 2.5 times more phases to achieve the same total output power. Furthermore, a four times increase in switching frequency resulted in almost doubling the overall converter losses when the increase in number of phases required are taken into account.

Although these results are suitable for high power applications, a large market for envelope tracking in cellular base stations require lower power and higher bandwidth.

Thus smaller, higher on-resistance devices are required to address these higher switching frequency applications, such as the new family of high frequency GaN power transistors listed in Table 2. Through their reduced size and structural and device improvements, they offer switching transition speeds in the sub nano-second range, making them capable of hard switching applications beyond 10 MHz. As an example, a 10 MHz, 42 V to 20 V buck converter’s efficiency results using one of these devices are shown in Figure 4.

Summary Envelope tracking is an emerging application that can significantly improve the performance of PA’s ubiquitous in modern and future technologies. To enable envelope tracking, higher speed devices are required. In this column high frequency hard-switching eGaN FET based buck converters suitable for high power envelope tracking were presented.

The results showed over 97% and over 94% efficiency at 1 MHz and 4MHz operation respectively. To further increase switching frequency, reductions in die active area and output power per phase are required. A new family of eGaN FETs was presented, with initial results showing peak efficiency of 89% at 10

Figure 4: Efficiency and loss results for an EPC8005 based demonstrators operating at 42 VIN, 20 VOUT.

MHz operation. eGaN FETs continue to enable exciting new applications not possible with the aging Si MOSFET. eGaN is a registered trademark of Efficient Power Conversion Corporation.

References [1] Cisco white paper, “Cisco Visual Networking Index: Global Mobile Data Traffic Forecast Update, 2012–2017”, February 2013.

[2] OpenET alliance, Introduction to envelope tracking, http://www.open-et.org/Intro-to-ETpa-712.php [3] J. Hendy, Transmitter power efficiency, http:// broadcastengineering.com/infrastructure/ transmitter-power-efficiency-1109/ [4] O. Garćıa, et al., “Overview of fast DC– DC converters for envelope amplifier in RF transmitters,” IEEE transactions on Power Electronics, vol. 28, no. 10, Oct. 2013, pp.

4712-4722 [5] M. Norris, D. Maksimovic, “10 MHz Large Signal Bandwidth, 95% Efficient Power Supply for 3G-4G Cell Phone Base Stations,” Applied Power Electronics Conference (APEC) 2012, Feb. 2012, Orlando, Florida. ■

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Power Developer

Nuclear Using

Energy to Power the Present and Future of Mars Rovers

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r

TECH ARTICLES In November of 2011, a spaceship was launched from Cape Canaveral Air Force Station in Florida. With the lower budget that the United States government has applied to the space program, it’s rare to hear about a big event related to space exploration. But, as the spaceship traveled into space leaving a trail of fuel exhaust, a new age of exploration had begun. This spacecraft was carrying the rover Curiosity. It was headed to Mars in order to study the red planet using state of the art instruments. NASA states that Curiosity is the most complex robotic explorer that has been sent to the red planet; these advanced instruments will measure different components and chemicals in the soil and air to determine what artifacts Mars contains in relation to the development of life. This mission will serve as a basis for a more advanced study of Mars launching in 2020.

Rover Image Courtesy NASA/JPL-Caltech

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Power Developer Powering Curiosity With all of the new technology being developed for a process to be performed in 2020, it is unusual to consider that not all of the technology involved is brand new. Curiosity uses a radioisotope thermoelectric generator (RTG) in order to generate all the power it needs. This technology was developed in the late 1950s and first used as an energy source in spacecraft in the early 1960s. The technology is a finite energy source that has scalable energy production. The process is based on the decay of plutonium in order produce energy in a nuclear fashion. After the heat energy is produced by the RTG, it is then converted to electrical energy through a thermocouple. The RTG that is used by this Mars rover has been developed by Boeing and Idaho National Laboratory and is called the “MultiMission Radioisotope Thermoelectric Generator” or MMRTG. The thermocouple that was designed for the MMRTG is a PbTE/TAGS thermocouple designed by Teledyne Energy Systems. A conclusive design is shown to the right.

The MMRTG is slightly different than a RTG as they are designed to be lighter, much safer, with a prolonged lifetime. In the case of Curiosity the minimum lifetime has increased to 14 years.

With the amount of fuel installed into Curiosity at launch, it was intended that the rover would have a two year mission duration. Everything that needs to be accomplished by Curiosity should be completed within this two year span, as it is unrealistic in terms of resources and cost to send and install more fuel into the rover. But, as the Mars rovers Viking 1 and Opportunity have shown, these power generation systems can provide energy much longer than their expected timespan. Viking 1 roamed Mars and collected data for about six years using a RTG. Opportunity landed on Mars at the beginning of 2004 and is still collecting data to this day. With a planned mission of around 90 days, this has exceeded its designed lifespan by a factor of 38. Choosing an RTG based fuel system was the logical choice for a mission of Curiosity’s caliber.

The way a RTG produces energy is a spectacular process and a testament to how far we have come with continual energy generation.

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The RTG uses the decay of radioactive isotopes to produce electricity. The radioactive isotope used in the Curiosity rover is plutonium-238.

Plutonium-238 is used versus other radioactive isotopes because it does not produce harmful radiation that can damage much of Curiosity’s other equipment. In light of this, plutonium does produce heat as it decays. The heat given off by the decay is converted to electricity using thermocouples.

Thermocouples produce electricity by sensing temperature differences between two dissimilar conductors. These conductors touch each other at a predetermined number of spots. When these two contacting spots differ in temperature, voltage is produced. The voltage that is created is then stored in two rechargeable lithium-ion batteries. This process, combining the plutonium decay with the thermocouples, produces enough

TECH ARTICLES electricity to power Curiosity consistently. This means that this rover will be continually powered through day, night and all seasons until its Plutonium runs out. But, how much fuel is needed to power such an advanced piece of technology?

How Much Power is that?

To complete all of the missions that Curiosity was tasked with, the fuel system must support all apparatuses for a minimum length of two years. All of the advanced microsystems actually have been efficiently crafted. All of the sensors, cameras, communications, and tools on Curiosity have very low power requirements. Actually, to help curb energy usage, one design specification that was built into Curiosity was warming pipes, these transfer heat waste to other parts of the system to help components keep a constant temperature. To help get an idea of how much power that is generated in order to efficiently power all components, it is necessary to look at the amount of plutonium-238 supply that was sent to Mars with Curiosity. The Mars rover took 10.6 pounds (4.8 Kilograms) of plutonium-238 packed into 32 cubes. Plutonium-238 generates 0.5 watts of power per gram, it is possible to calculate the how much energy per day that

"The RTG uses the decay of radioactive isotopes to produce electricity."

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Power Developer Curiosity can realistically use. With one kilogram of plutonium-238, the output power would be 500 watts. With the total 4.8 kilograms available to Curiosity the system has a total of 2.4 kW of thermal power. From this amount of power, the PbTe /TAGS thermocouple was designed to output around 125 watts of electrical power from this 2.4 kW of thermal energy during the first 14 years of production. After 14 years, the system is designed to reduce electrical power output to around 100 Watts. Using 125 watts per day roughly translate to around 2.5 kWhs per day. Considering a laptop at full load uses around 65-75 watts, all 11 of the specialized high tech instruments use much less power in order to sustain 125 watts per day.

It is amazing at what humankind has been able to do with the technology that is available to us today. Using state of the art power

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generation, a rover can be sent to Mars and gather data for 10 years and beyond. Considering that there are several rovers on Mars that are continuing to collect data, power generation on remote sources while stationed on an extraterrestrial planet, has been extremely successful. Although production of plutonium is expensive and very slow, the technology used to power Curiosity and several older rovers will be used in future Mars exploration missions. The power source for the 2020 Mars rover mission is already set to use the same exact power source as Curiosity. This is possible as a backup MMRTG was designed for Curiosity but didn’t make it into the final design. This goes to show that even by 2020, a power source technology developed in the 1950s will be more than enough to enable the rover to gather data.

TECH ARTICLES

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Power Developer

Innovation Through Collaboration

Micrel Inc. is a global manufacturer of integrated circuits with a fo management ICs. The company's diversified product offering has excellent record of revenue growth and sustained profitability. T due in part to the company's unique collaborative environment, w and design engineers work together to develop innovative power m

Power Developer spoke with Mansour Izadinia, Senior Vice Presid Solutions at Micrel, about why this collaborative environment is c success, the company's emphasis on working with customers eve what the future holds for the company.

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COVER INTERVIEW

Mansour Izadinia

Senior Vice President of Micrel

n

ocus on linear and power s endowed them with an This financial stability is where process engineers management products.

dent of Analog & Power crucial to the company's ery step of the way, and

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Power Developer

“

Micrel Inc. is a global manufacturer of integrated circuits with a focus on linear and power management ICs. The company's diversified product offering has endowed them with an excellent record of revenue growth and sustained profitability. This financial stability is due in part to the company's unique collaborative environment, where process engineers and design engineers work together to develop innovative power management products.

Senio

“

Our view of Micrel and where we can compete is in product lines Innovation where gross margin and Through profitability of product Collaboration lines is important to us.

Power You Developer with Mansour Senior Vice PresidentWhen of Analog & Power are spoke responsible for Izadinia, these major you are working on new Solutions at Micrel, about why this collaborative environment is crucial to the company's divisions that have really technical products, how success, the company's emphasis on working with customers every step of the way, and much of it is feedback products.

How are you deciding from your customers versus finding what the future holds for the company.

what products to develop within these divisions?

opportunities and creating a product that will compete with other products?

That’s a very good question. We have an overall strategy for the company, in terms of gross margins and the business aspects. There is a roadmap that we have developed that is consistent with those business objectives. Our view of Micrel and where we can compete is in product lines where gross margin and profitability of product lines is important to us.

That narrows down certain product lines and the products that we do quite significantly. We certainly don’t want to be the jack-of-all-trades, but we do want to be the best at what we do and we tend to go after markets that reward us for what we do and give us the gross margin dollars for what we do. Those markets tend to be more industrial markets—industrial and communication are the two types of markets that generally afford us the gross margins necessary for our long term success. We also have a metric for profitability, and development time that we spend on a product.

Historically, Micrel tends to be a commodity power management supplier. What we have done in the last three years is we have become a lot more application specific.

Our marketing guys are always talking to customers and we create not customized products, but application specific products for a given application set. The products tend to be the best at a given application, not necessarily for one given customer. We are listening to our customers and we do try to listen to the broad requirements of the customers, and address those requirements with really innovative approaches to the development.

Innovation Through Collaboration 18

Most of the time that we talk to a customer, they tell us the problems they have today, but that might not be the problems they have when we’re putting a product out on the market.

Micrel Inc. is a global manufacturer of integrated circuits with a focus on linear and power management ICs. The company's diversified product offering has endowed them with an excellent record of revenue growth and sustained profitability. This financial stability is due in part to the company's unique collaborative environment, where process engineers and design engineers work together to develop innovative power management products.

Senio

COVER INTERVIEW This is because it generally takes about a year or more to develop an Integrated Circuit.

We always have to bridge that gap, and that might be a year or sometimes even two years down the road. We have to anticipate what the customer’s problems will be two years down the road when they actually have a product in hand. That sometimes is the difficulty in trying to figure out where the market is headed.

The other reason we like to develop application specific products is that typically, if you have a commodity product, you get engaged with the customer at the end of their design cycle time. The more application specific products you have, you engage with the customer earlier in their design cycle and the product is higher value-add. Consequently, you are more important to your customer.

In bringing these new power products to market, what’s the biggest challenge you encounter?

Now, my process engineers are not only process engineers—I like to think of them as circuit design engineers as well. In fact, I

Buck Regulator from Micrel

“

Our marketing guys are always talking to customers and we create not customized products, but application specific products for a given application set.

“

I would say the challenge is that the power market is very crowded and commoditized.

The suppliers who bring the most innovation to market are the ones that are actually going to grab market share. If you look at semiconductor processing or circuit design, each one of those pushes the envelope quite a bit, but what hasn’t happened so much is people have not been able to bridge the gap between different disciplines that are required to bring innovative products to the market. For example, one of the things I did with Micrel is that I literally asked our process engineers to sit together with our design engineers and that created a lot of important dialogue. As a result, we were able to define process technologies that designers needed to have. This was very important and actually led us to quite significant, innovative process technologies. With other companies, the process technology engineers sit in one building and the design engineers sit in another, which is not conducive to innovation.

We need to create a forum for dialog between different disciplines. I am always trying to breakdown the barriers for communication.

That is what drives innovation.

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Power Developer

Innovation Through Collaboration

Sen

“

“

One of the things I did with Micrel is that I literally asked our process engineers to sit together with our design engineers and that created a lot of important dialogue. As a result, we were able to define process technologies that designers needed to have.

Micrel Inc. is a global manufacturer of integrated circuits with a focus on linear and power management ICs. The company's diversified product offering has endowed them with an excellent record of revenue growth and sustained profitability. This financial stability is In terms the global market for was our people that if I could get due in part to telling the company's unique collaborative environment, where processof engineers and design engineers develop power management products. away withwork it, I together would towipe offinnovative the title power products, are you seeing more

from your business cards. You can create

companies entering the market with

that have developed many innovative packaging technologies that solve the thermal issues. These guys sit down together with the process and design engineers and that’s how we can bring innovation to the marketplace.

I think in certain segments there is a lot of consolidation. Within the last 5 years, the lack of venture capital has caused a lot of power management companies to run dry, and as a result be acquired or go out of business.

With that said, the companies that do tend to be surviving are the companies that choose their end markets very carefully. If you look at the industry right after the crash of 2000, a lot of the telecom industry got wiped out and many companies’ revenue dropped. Many companies rushed into the consumer markets to revive their revenues. That actually proved to be futile because there was no profit margins, especially for companies that are listed on the United States stock exchanges profitability is extremely important. A lot them are realizing that they cannot run a company on very low gross margin product lines. Now, they are shedding some of those product lines. Many companies may be getting acquired as a result, or they are shedding some of their divisions to improve their bottom line profitability.

Power Developer spoke with Mansour Izadinia, Senior Vice President of Analog & Power innovation when you are able to combine newtoproducts, or is there a consolidation Solutions at Micrel, about why this collaborative environment is crucial the company's from these on different disciplines. success,elements the company's emphasis working with customers every step of theexisting way, and companies? between Today, we for have packaging engineers what the future holds the company.

What kind of internationalization is occurring with Micrel?

I would say that we are totally spread across the globe. We are an around-theclock company and all the work gets done in a seamless fashion. For example, for our Mobile products, product design, and customer interaction—almost all of it is driven from our Asian design centers. All of our server power management products are driven from our San Jose office. We basically go where we can find talent. And we have put in place the systems to make sure people across the globe feel they are sitting in the next door office.

Innovation Through Collaboration 20

Micrel Inc. is a global manufacturer of integrated circuits with a focus on linear and power management ICs. The company's diversified product offering has endowed them with an excellent record of revenue growth and sustained profitability. This financial stability is due in part to the company's unique collaborative environment, where process engineers and design engineers work together to develop innovative power management products.

Sen

COVER INTERVIEW What do you see that is happening in the industry that is driving a lot excitement in your product lines?

I think data centers and video processing is going to drive the Internet infrastructure. As a result of that, data centers are becoming extremely important and people are going to distribute the systems and make sure that the power that they use is optimized.

A lot of power management companies are realizing what kind of a challenge that is. We started realizing these challenges three or four years ago and some of the power management products we have coming out are state-of-the-art in terms of power efficiency. That is going to drive a lot of high margin business for us in the next few years.

What’s the company culture like at Micrel?

“

People are not graded based on their business titles, but on contributions and working together to get a product out.

We work hard, play hard, and we are more friends than we are co-workers.

“

What I like to describe to our people is that this is a large company with a small company environment. A lot of people who work at Micrel have also worked for me before in other places. It’s a very tight team of people who have worked together for some time. I would say the relationship between management and them is one where there is no boundary. I don’t feel that I’m a manager and I feel that people that report to me know the kind of collaborative environment that I promote. People are not graded based on their business titles, but on contributions and working together to get a product out. We work hard, play hard, and we are more friends than we are coworkers. I know I am not an easy manager and many engineers say my expectations are too high, but they like the challenge I provide them and I tend to help them out when I see necessary. They like that. I also tend to be blunt and address issues headon. But also in a way that if compassionate and harmonious. That is important. ■

21

Power Developer

Perfection in P

Mini Power Supplies Low

While the initial enthusiasm for renewable energies might have somewhat energy saving is still a major concern for manufacturers and consumers alike. A to the EU Commission, suitable technical measures as regards the standby and o power consumption of office and home electronics can reduce energy consum 75% by 2020. January 2013, the second phase of the EcoDesign Directive came in reducing the existing limit values by another 50%. This article outlines the contri specially developed mini power supplies to achieve this feat.

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TECH COLUMN

Power

wer Standby Consumption

receded, According off-mode mption by nto effect, ibution of

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Power Developer

O

nly days after the Fukushima disaster, Germany decided to exit nuclear power.

The frightening pictures from Japan were just too horrible, and the alternatives looked promising.

People envisaged gigantic off-shore wind parks along the cost, and solar power plants in the Sahara desert. These solutions would do away with the problems of nuclear waste disposal and the risk of a Maximum Credible Accident.

In reality, things are obviously more complex.

While the sun shines 365 days a year over the Sahara desert, it does not shine at night. To provide electricity during night-time, we need huge storage capacities or other power sources.

Other problems arise in connection with the distribution of the power. While electricity is traditionally generated close to the consumer, off-shore wind parks and solar plants in far-flung countries require huge power pipelines. Where such lines are to be installed near residential areas, the planning process is likely to take years.

It is already obvious today that the move towards renewable energy will take much longer than

24

was initially envisaged. More immediate measures are necessary to prevent blackouts as are already happening in the USA and India. Energy-saving measures offer the best alternative. According to the EU Commission, the power that can be saved by reducing the standby and off-mode consumption of the millions of electronic devices that are found in every office and household is estimated to correspond to the annual power consumption of Denmark.

Standby and off-mode losses are underestimated Your average consumer with limited technical knowledge probably still believes that switching a device to standby mode is basically the same as switching it off altogether. He or she does not expect standby consumption to show up on the electricity bill. But your average consumer is wrong. In the old days when the garage door was controlled with a key and the OFF switch of the stereo system was actually a mains switch, off meant off. Today, most home and office

TECH COLUMN According to the EU Commission, the power that can be saved by reducing the standby and off-mode consumption of the millions of electronic devices that are found in every office and household is estimated to correspond to the annual power consumption of Denmark. electronics come with a “soft off� button, which puts them into standby or off-mode.

This means that a power supply designed for normal operation remains powered in noload mode, consuming power with terribly low efficiency. This also applies to the many external plug-in adapters that can be found in every house and office. Adapters enable manufacturers to save development and certification costs. Products can be shipped at low cost with different adapters to the various countries to match the power and plug standards. The only loser here is the consumer who pays for this through his electricity bill. Power supplies remain connected to the grid around the clock and consume considerable amounts of power even when not in use, depending on their circuitry. This can easily be verified, particularly with older, linear controlled power supplies as they become warm.

The same applies to stereo systems, which, due to the low interference, are generally equipped with linear controlled power supplies. In older devices, the standby electronics are powered directly from the mains power supply, so that they consume between 10 and 20W even in standby mode, which is about half the power consumed in operating mode at normal room volume.

Assuming that the stereo system is in standby mode for 20 hours a day, 70% of its overall consumption occurs during the standby time.

Comfort thus comes at a high price. Remotecontrolled blinds and garage doors show even less favourable figures. They are normally operated for a few minutes a day, so that they are idle and in standby mode for 99% of the time. The worst offenders are, however, old fax machines. If only a single fax is received per week, which is probably quite realistic for private fax machines, the device is in standby mode for 99.99% of the time, consuming up to 20W just waiting for a message.

Fig. 1: Applications for separate standby power supplies are extremely versatile and not limited to mass market products, as this functional diagram of a remote pump station shows.

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Power Developer Apart from the generally high power consumption in standby mode, it was the unreasonable ratio between actual operating time and standby time that caught the attention of the EU Commission. In many homes, up to 50 electronic devices with standby function or external adapter are plugged in day and night. Most of these are only used for around 10% of the time. In a well-equipped household of four, the standby and off-mode consumption can easily amount to 200W, costing the family around $500 per year.

Fig. 2: The RAC03-24SC offers excellent efficiency, especially in the medium to low load range.

The situation in offices is not much better. Legions of adapters power PC peripherals, communication devices and modems around the clock, even when there is nobody in the office. For older devices, details regarding power consumption in standby or offmode are rarely included in the data sheets.

standby circuits with display, such as those of hard disk recorders, must not consume more than 1W. For simpler systems and plug-in adapters, the maximum standby consumption is limited to 0.5W.

Automated systems are found everywhere in our homes, offices and factories, from sensorcontrolled blinds to remote-controlled garage doors. For a few minutes of action, these systems remain powered around the clock. This also applies to remote access equipment for data loggers, weather stations, pump systems and similar equipment with SMS or GPRS modems.

While such applications are generally not included in the EuP Directive, due to the low number of devices, they are nevertheless taken into account by people who take energy saving seriously. Low standby consumption has already become an important USP for manufacturers, as the marginally higher production costs are no longer an issue.

To achieve these limits, RECOM has already launched the RAC04 and the RAC06, two lowcost mini power supply series. The modules with a rated power of 4W and 6W, respectively, consume only 200 to 300mW at a mains power of 230V, which is clearly below the new EU limits. As standby consumption and energysaving ratings are now a common feature in promotional material, mini power supplies with low no-load power have become extremely popular. As a leading manufacturer of such devices, RECOM is no longer guided by the EuP Directive but by what is technically feasible.

The new 3W ultra-low power supplies show that there is still ample scope for improvement.

Stricter limits expand the market for mini power supplies

New low-power modules with no-load consumption of 0.03W

The EU Framework Directive on energy-using products, known as the EuP Directive, came into force in 2010 and put a stop to the low-cost practice of feeding the standby electronics from a mains power supply. Manufacturers had to resort to technically more demanding solutions where the standby circuit is supplied through a separate mini power supply and the main power supply is fully disconnected from the grid by means of a relay.

Switched-mode power supplies are designed in such a way that their optimum efficiency is close to the rated power. The efficiency drops in line with the load, until it is near zero when the device is in no-load mode.

This drop, however, is not linear, and many data sheets contain only the peak values.

This is often misleading, as has been shown in recent comparison tests of a number of products from different manufacturers, carried out by RECOM. In these tests, the efficiency, especially in the lower and medium load range, was compared. This efficiency is relevant as power supplies are normally not

In January 2013, the above EU policy enters its second phase, where limit values are halved again. According to these regulations, complex

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TECH ARTICLES exactly matched to the rated power and must cater for a certain safety reserve. The results were quite surprising. Despite comparable peak values around 80%, the RECOM mini power supplies were considerably more efficient in the medium and lower load ranges. At 50% load, the efficiency was still near the peak value. At a load of 15%, the measured efficiency of the mini power supplies was still between 60 and 70%, an excellent result. Manufacturers are thus advised to choose their power supplies with great care and to perform their own tests.

As regards efficiency, the need to operate the power supply at near-full load level is less important today than before. The RAC03 (3W) could therefore be used without any problems for applications that require only 1W or 2W. RECOM nevertheless decided to develop separate mini power supplies for 1W and 2W, respectively, namely the RAC01 and RAC02.

This was done for a good reason: lower noload consumption! As outlined above, no-load consumption contributes heavily to standby consumption. With our new 1W and 2W modules, the consumption is typically reduced to 30mW rather than just to the limit value of 0.5W as laid down in the EuP Directive. This means that the standby power consumption is reduced by up to 94%. With these new modules, the issue of standby consumption has thus been put to rest for the foreseeable future. These products are designed to help achieve the energy saving targets of the EU for 2020, when 75% power should be saved despite an increase in the number of electronic devices.

Other advanced technical features Apart from energy efficiency, electromagnetic compatibility is a major concern, as nobody wishes to get entangled in controversies about electro-smog and electromagnetic interference. In addition to emitted interference, low line-bound interference is an issue here.

Power supplies of the RECOM RAC series conform to EN 55022, class B, and EN 55024 that apply to household applications. This is achieved without additional external components but by means of harmonised electronic scanning of the mains frequency. Interference is thus eliminated at the source, so that small filter components can be used, especially when compared with external solutions. This has a positive effect on the power consumption, contributing to the extremely low noload rating.

RAC mini power supplies are available for a wide input voltage range from 90 to 305VAC (except 1W version) and can thus be used in conjunction with micro controllers, sensors and similar equipment in both Europe and the USA with its 227VAC mains system. The modules come with a softstart function limiting the inrush current to 10A/ <0.5ms (RAC01/02/03), or 30A/<0.2ms (RAC06), respectively. All modules are short-circuit-proof and protected against overload. The outlet voltage can be set to any value between 3.3 and 24VDC. The 3W module is also available with a 3.8VDC output for chargers and GSM modems. For features, see the list to the right.

Designed for years of continuous operation As a European manufacturer operating in the global market, RECOM uses only selected components that have extensively been tested in its own environmental lab in Austria. The prototypes of new power supplies undergo HALT tests, so that any problems are detected early during the development phase.

The products of the RAC series are UL/EN and CE certified, and designed for continuous operation over many years. â&#x2013;

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Fig. 3: Overview of RAC Modules (1W to 6W)

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