February 2015
Powering the Green Energy Revolution Designing Low-power Embedded Systems
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record and substantive history to back them up. Although optical and magnetic encoders are long established, and employ what may seem like “more-tangible” physical concepts, the capacitive encoder also uses fully-tested principles, as proven through many successful years in the field. This alternate approach to motion sensing, being digitally based, opens up a range of benefits and delivers a new level of intelligence for designers utilizing rotary commutation encoders.
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CONTENTS
NEW APPROACH OPENS NEW OPPORTUNITIES
Rotary encoders are critical to nearly all motioncontrol applications, and the need for them is expanding further due to the increased use of brushless DC (BLDC) motors, which brings benefits in control, precision, and efficiency. The encoder’s task is simple, in principle: to indicate the position of the motor shaft to the system controller, Figure 1. Using this information, the controller can accurately and efficiency commutate the motor windings as well as determine speed, direction and acceleration – parameters that a motion-control loop needs to maintain desired motor performance.
CONTENTS
TECH REPORT Designing Intelligence into Commutations Encoders Figure 1. Rotary encoders provide motor shaft direction, position, speed, and acceleration information
Encoders can be based on a variety of technologies, all of which provide the standard digital outputs of A and B quadrature signals, plus an index output in some models, Figure 2a. Commutation encoders (described more fully on the following pages) also provide U, V and W commutation-phase channel outputs, Figure 2b.
TECH SERIES
The “Smart Grid” – Vision for the Future
A network of integrated microgrids that can manage demand, monitor and heal itself Building Automatio n
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Design Considerations for Low-power Embedded Systems: Part 1
Grid Monitoring /Managemen t
EEWEB FEATURE Solar Farms
Semitech’s Bright Future Powering the Green Energy Revolution
Distributed Power Management
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Smart Meters
INDUSTRY INTERVIEW In-Grid Machine-to-Machine Communication is Key to Smart Grid Success Semitech Semiconductor
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Transmission Line & Distribution Monitoring
Active Lighting
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PRODUCT WATCH ROHM Supercap Cell Balancer IC
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The energy savings that are enabled by our products can actually pay for the cost of those power electronics...pg. 28
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Designing
Designing Inte Commutation By: Jeff Smoot, CUI Inc
INTELLIGENCE into
COMMUTATION ENCODERS C
UI
For larger uses
By Jeff Smoot, CUI Inc.
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IN C
elligence into n Encoders
TECH REPORT
E
ncoder users traditionally have been reluctant to change—with good reason. Motor control on the factory floor or in an industrial installation is not the place for innovations that make performance and reliability claims but lack a track record and substantive history to back them up. Although optical and magnetic encoders are long established, and employ what may seem like “more-tangible� physical concepts, the capacitive encoder also uses fully-tested principles, as proven through many successful years in the field. This alternate approach to motion sensing, being digitally based, opens up a range of benefits and delivers a new level of intelligence for designers utilizing rotary commutation encoders.
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ns up a range of benefits and delivers izing rotary commutation encoders.
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New Approach Opens New Opportunities Rotary encoders are critical to nearly all motion-control applications, and the need for them is expanding further due to the increased use of brushless DC (BLDC) motors, which brings benefits in control, precision, and efficiency. The encoder’s task is simple, in principle: to indicate the position of the motor shaft to the system controller, Figure 1. Using this information, the controller can accurately and efficiency commutate the motor windings as well as determine speed, direction and acceleration-parameters that a motion-control loop needs to maintain desired motor performance.
igure 1. Rotary encoders provide motor shaft direction, posion, speed, and acceleration Figureinformation 1: Rotary encoders provide motor shaft direction, position speed, and acceleration information.
ch provide the standard digital outputs of A and B ure 2a. Commutation encoders (described more fully -phase channel outputs, Figure 2b.
Encoders can be based on a variety of technologies, all of which provide the standard digital outputs of A and B quadrature signals, plus an index output in some models, as seen in Figure 2a.
Designing Intelligence into Commutation Encoders
LEDs Channel I Channel A
Channel B
Light Detectors
+5V 0V +5V 0V
+5V 0V
Figure 2a. Standard A and B quadrature signals plus an index signal, shown here for an optical encoder
Figure 2a. Standard A and B quadrature signals plus an index signal, shown here for an optical encoder
U
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TECH REPORT Commutation encoders (described more fully on the following pages) also provide U, V, and W commutation-phase channel outputs, as seen in Figure 2b.
The magnetic encoder’s construction is similar to the optical encoder, except that it uses a magnetic field rather than beam of light. In place of the slotted optical wheel, it has a magnetized disk, which spins over an array of magneto-resistive sensors. Any rotation of the wheel produces a response in these sensors, which goes to a signal-conditioning front-end circuit to determine shaft position. While it offers a high level of durability, the magnetic encoder is not as accurate and is susceptible to magnetic interference produced by electric motors.
Encoder Technologies The three best-known encoder approaches use optical, magnetic, or capacitive techniques. In brief, the optical approach uses a slotted disk, with an LED on one side and DesigningonIntelligence phototransistors the opposite side. intorotates, Commutation As the disk the lightEncoders path is interrupted, and the resultant pulses indicate shaft rotation and direction. Although low cost and effective, the LEDs reliability of an optical encoder is Channel degraded by twoI factors: contaminants such as dirt, dust, Channel A and oil can interfere with the light path, and the LEDs have a limited lifetime, typically losing half their brightness in a few years and eventually burning out. Channel B
A third approach, capacitive encoding, offers all the benefits of optical and Light Detectors +5V magnetic encoder designs, but without 0V their weaknesses. This technique uses the same principle as the wellestablished, low-cost yet +5V precise digital 0V vernier caliper. It has two patterns of bars or lines, with one set on the fixed element and the other set on the moving element, +5V 0V
Figure 2a. Standard A and B quadrature signals plus an index signal, shown here for an optical encoder
U
V
W
S1
S2
S3
S4
S5
S6
180 MECH-DEG
30 MECH-DEG
One absolute mechanical revolution (360 MECH-DEG) Figure 2b. The U, V and W waveforms produced by a commutation encoder
Figure 2b. The U, V, and W waveforms produced by a commutation encoder
ENCODER TECHNOLOGIES The three best-known encoder approaches use
reliability of an optical encoder is degraded by two factors: contaminants such as dirt, dust, and oil can interfere with the light path, and the LEDs have a limited lifetime, typically losing half their brightness
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is not as accurate and is susceptible to magnetic interference produced by electric motors.
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A third approach, capacitive encoding, offers all the benefits of optical and magnetic encoder designs, but without their weaknesses. This technique uses the same principle as the well-established, lowcost yet precise digital vernier caliper. It has two patterns of bars or lines, with one set on the fixed LEDs Light Detectors element and the other set on the moving CUI’s new AMT31 series is element, an together forming a variable capacitor configured example of a state-of-the-art as a transmitter/receiver pairing, Figure 3. As the encoder rotates, an encoder, integral ASICproviding counts these line capacitive changes and also interpolates to find the position A and B quadrature signals, an of the shaft and direction of rotation to create theindex standard quadrature outputs, the signal, as well asand U, also V, and commutation outputs that other encoders provide to W commutation-phase signals. control brushless DC (BLDC) motors.
advantages derived from their digital control features – this includes the ability to adjust the encoder’s resolution (the pulses per revolution count) without the need to change to a higher, or lower, resolution encoder. together forming a variable capacitor THE BEST OF ALL WORLDS configured as a transmitter/receiver
as seenseries in Figure As the encoder CUI’spairing, new AMT31 is an3. example of a staterotates, an integral ASIC counts these of-the-art capacitive encoder, providing A and line changes and also interpolates to find B quadrature signals, an index signal, as well as the position of the shaft and direction of U, V, and W commutation-phase signals. Twenty rotation to create the standard quadrature selectable incremental resolutions between 48 outputs, and also the commutation to 4096 pulses per revolution (PPR) and seven outputs that other encoders provide to motor pole-pairs from to 20 are available. The control brushless DC2(BLDC) motors. AMT31 series also features a locking hub for ease of installation, from a 5 V rail and requires The beauty operates of this capacitive technology just is16that mAthere of supply current. is nothing to wear out and it is immune to contaminants such as
Transmitter
Receiver
However, the benefits of the capacitive dust, dirt, and oil, which are common encoder go far beyond superior performance, flexibility, and in industrial environments, making it shortand long-term reliability. Unlike optical and inherently more reliable than optical devices. Capacitive also offer magnetic encoders, itsencoders digital-output side takes performance advantages derived from system design into the 21st century, offering many their digital benefits control features – this of encoder use unique system in all phases ability to adjust the encoder’s fromincludes productthe development, to installation, and even resolution (the pulses per revolution maintenance.
count) without the need to change to a lower, encoder. Whyhigher, is thisor so? The resolution output of the optical or magneti
Figure 3. A capacitive encoder counts the received pulses resulting from the modulation of the transmitted Figure 3. A capacitive encoder counts the received pulses signal by the rotor that is attached to the motor shaft. resulting from the modulation of the transmitted signal by the rotor that is attached to the motor shaft
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encoder is functional but “dumb”, and offers users The Best of All Worlds no flexibility, insight, or operational advantages. In contrast, the capacitive encoder is digitally based an CUI’s new AMT31 series is an example usesofaabuilt-in ASIC and capacitive microcontroller to provide state-of-the-art encoder, providing A and B quadrature signals, additional features and enhanced performance. This an output index signal, as well U, V, andperformance W smart changes theas user and commutation-phase signals. Twenty scenario in many ways, while still being 100% selectable incremental resolutions compatible with standard encoder outputs. between 48 to 4096 pulses per revolution (PPR) and seven motor pole-pairs from 2 to 20 are available. The AMT31 series also features a locking hub for ease of installation, operates from a 5V rail and requires just 16mA of supply current.
s
y e, n
ic
nd
s
TECH REPORT However, the benefits of the capacitive encoder go far beyond superior performance, flexibility, and short- and long-term reliability. Unlike optical and magnetic encoders, its digitaloutput side takes system design into the 21st century, offering many unique system benefits in all phases of encoder use, from product development, to installation, and even maintenance. Why is this so? The output of the optical or magnetic encoder is functional but “dumb”, and offers users no flexibility, insight, or operational advantages. In contrast, the capacitive encoder is digitally based and uses a built-in ASIC and microcontroller to provide additional features and enhanced performance. This smart output changes the user and performance scenario in many ways, while still being 100% compatible with standard encoder outputs.
Substantial, Beneficial Change is in Place Let’s look in more detail at the enhancements made possible by the ASIC and microcontroller which are part of a capacitive encoder such as the CUI AMT31 series: è The digital nature of the CUI capacitive encoder enables simple and quick “One Touch” zeroing. The process is straightforward: lock the shaft to the desired position by energizing the proper motor phases, and command the encoder to “zero” at this position; the total time is just one to two minutes and no special instruments are needed.
In contrast, zeroing to mechanically align the commutation signals with the motor windings using an optical or magnetic encoder is a multistep, complex, and often frustrating process. It requires locking the rotor, physical alignment, and then backdriving the motor while using an oscilloscope to observe the back EMF and encoder waveforms for proper zero cross alignment. This is often an iterative process with the steps usually needing to be repeated for fine-tuning and verification, so the entire cycle can take 15 to 20 minutes. è The digital features of the AMT series also greatly enhance the system design process, providing flexibility, diagnostics, and enabling assessment of the motor and motorcontroller performance. In particular, since a single capacitive encoder can support a wide range of resolution and pole-pair values, designers can use this programmable- resolution capability to dynamically adjust the response and performance of the PID control loop during controller and algorithm development without having to purchase and install an entirely new encoder. è The intelligence built into the AMT series also allows for on board diagnostics for quicker field-failure analysis, an industry first. The encoder can be queried to indicate if it is operating properly or if there is some sort of failure due to mechanical misalignment on the shaft or other issues. Therefore, the designer can
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Power Developer quickly determine if the encoder is at fault and if not, look for the source of the problem elsewhere, thus ruling out the encoder itself as possible problem. Furthermore, engineers can use this feature for preventative measures - for example, executing an “encoder good” test sequence before running the application. These capabilities, not available in optical or mechanical encoders, allow designers to keep downtime to a minimum while anticipating issues that might occur with units in the field. è Finally the digital interface also simplifies the bill of materials (BOM). Since the encoder can be tailored in software to the specific variation (PPR, pole pairs, and commutation direction) needed, there’s no need to list and stock the different versions needed in a multi-motor product, or for multiple products, or in the installed location.
Intelligent Encoder Plus GUI: A Powerful Pairing The Windows PC-based AMT Viewpoint™ software for CUI capacitive encoders speeds development, and also turns time-consuming mundane tasks, such as
identifying model number and version, into simple operations. It requires just a USB cable to interface to the encoder, and implements a simple serial-data format. The GUI shown in Figure 4, allows the user to tailor and customize the encoder to the application’s needs. A settings screen in the GUI lets users see key encoder waveforms and timing, with automatic adjustments as the encoder options are changed. Programming an encoder through the GUI takes just a few keystrokes and about 30 seconds for the cycle to complete. Most dramatic, the aligning and zeroing of an encoder for either A, B, index or commutation mode takes only seconds, a sharp contrast to completing this task with a non-programmable encoder. In demo mode, users can go through the GUI and also perform encoder-related operations as if an actual encoder is attached, a convenient way to become familiar with the encoders and tools prior to any purchase or hands-on use. Finally, the GUI also supports creating orderable part numbers for specific encoder versions, which include options in output format, sleeve (bore) adapter, and mounting base, among others.
The digital features of the AMT series greatly enhances the system design process, providing flexibility, diagnostics, and enabling assessment of the motor and motor-controller performance.
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to any purchase or hands-on use. Finally, the GUI also supports creating orderable part numbers for specific encoder versions, which include options in output format, sleeve (bore) adapter, and mounting base, among others.
TECH REPORT
Summary The benefits of encoders based on capacitive technology offer much more than just improved performance and reliability. A device like CUI’s AMT31, with its built in ASIC/microcontroller, provides intelligent functionality supporting programmable set-up and installation features, enabling operating insight and simplifying inventory management. When these features are coupled with the PC-based GUI, it can provide an easy-to-use yet sophisticated capability, which greatly simplifies all aspects of encoder use from prototype design-in, evaluation, and debug through installation and configuration, to diagnostics and inventory minimization. And all of this is at comparable cost to other encoders, maintaining compatibility with standard outputs types and formats, while also achieving lower power consumption. The AMT31 with its easy-to-fit adapters for different shaft sizes (Figure 5) represents the logical next step in leveraging the power of an intelligent interface to provide wideranging benefits that are not available with other encoder technologies. For more information visit cui.com/amt-modular-encoders. cui.com/amt-modular-encoders
Figure 5. CUI’s AMT31 Encoder provides a unique combination of durability, flexibility, and intelligence.
Figure Figure4. 4.CUI’s CUI’sAMT AMTViewpoint Viewpointsoftware software provides an provides an easy-to-use development easy-to-use development interface interface.
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Power Developer
Design Considerations for Low-Power Embedded Systems: Part 1 By Rahul Raj Sharma and Tushar Rastogi Our lives are filled with an increasing number of tiny, batterypowered devices and systems. These embedded systems must sustain themselves from the same power source for a long time to reduce recurring maintenance costs or to free end-users from having to replace the power source frequently.
This article deals with the various considerations in designing a low-power system and the tradeoffs involved. Early planning can reduce the need for re-working or re-coding while optimizing the system for low power. Such considerations include: 1.
Designing for low power at the application level
2. Understanding the trade-offs between power and performance 3. Employing hardware and firmware techniques that optimize power consumption.
Power Consumption Factors in Embedded Applications The power consumed by any given system can be classified into two broad categories:
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i. Static Power: Static power comprises the power consumed by the device when it is not running code and waiting for a specific event to trigger the system to wake into active mode. The major contributors to static power consumption include the leakage current flowing in the system, analog biasing, blocks which run independent of code like the RTC, watchdog timers, interrupt controllers, and more. This current is directly proportional to the operating voltage of the device. The higher the operating voltage, the higher the leakage current. ii. Dynamic Power: The power consumed when the system is active and the CPU is executing
TECH SERIES program code is known as dynamic power. The dynamic current of a system depends on the operating frequency, voltage, and the parasitic capacitor on the bus and circuit design.
This is given as:
P= V^2*f*C V: Voltage f = Operating frequency C = Parasitic capacitance on the output
Graphical Representation of Static and Dynamic Power:
For any given transistor, its static power is almost constant for a given power supply voltage. The static power comes from leakage current (CMOS circuits) or biasing current (active analog circuits), depending upon the type of system.
Dynamic power consumption in a transistor happens during the voltage transitions. During these transitions, the CMOS pair attains a state in which both of the devices of the CMOS pair are partially switched ON and act as a resistor, hence
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Power Developer forming a potential divider circuit. This virtual potential divider circuit consumes much higher power compared to the leakage current during a defined logic level. This is why dynamic power is directly proportional to the frequency of switching in a circuit. As such, it is one of the most fundamental considerations while defining a low-power embedded system; i.e., to keep the system switching events as low as possible.
Design Considerations for Low-power Battery Operated Embedded Applications Hardware Considerations Type of battery: There are mainly three types of batteries found in embedded applications: standard alkaline cells, rechargeable alkaline and lithium-ion cells, and coin cells. For a wide range of low-power embedded applications, recharging the system is not a reasonable use-case model. This eliminates the use of rechargeable cells for these applications. Let’s compare the other two cells useful in low power applications and considerations required while selecting them for the design. Standard Alkaline Cells: A standard AA cell has a typical capacity of around 1500mAh. It can easily provide a peak current in the range of hundreds of mA and can be drained at a constant rate of 50mA. An alkaline battery can provide high peak currents to an application, meaning
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the system can run at its highest clock frequency while using all its dedicated peripherals in parallel (timers, communication blocks, etc.) to complete tasks as quickly as possible and then drop into a low power operating mode. Coin Cell Battery: A coin cell battery has a very high internal resistance and therefore can’t withstand high peak currents. Their effective voltage drops considerably when peak currents of more than 20mA are applied, even for very short durations. Hence, for coin cell-operated designs it is highly advisable to design with components, which can reliably work at a voltage of 2V or below. The brown-out voltage of the microcontroller should be low enough to avoid unintentional resets in the system during times of high peak current supply by a coin cell. We also need to take precautions to reduce the peak currents required by the system. Ways to reduce the peak currents include: •
Reducing the CPU clock frequency
•
Avoiding enabling all the internal blocks at once by distributing the load over time
•
Cutting the power to the external components and internal blocks when they are not in use.
Selecting the right microcontroller: To keep both static and dynamic power consumption to a minimum in a low
TECH SERIES power application, it is very important to choose a microcontroller with the required set of peripherals capable of working at the desired power mode. Depending on the requirement the system designer can choose the right microcontroller which supports the right set of peripherals required in his application, at low power mode. Consider an application that requires an LCD to operate for extended period of times. By choosing a microcontroller that can run the LCD in a low power mode, developers can minimize power consumption. An example of such a microcontroller is the PSoC 4 from Cypress that can retain an LCD display at a current consumption of only 3uA in deepsleep mode. Similarly for complex applications, we need to make tradeoffs and decide upon the suitable microcontroller which can complete every task in the least average power.
them. However, at the same time it increases the RC time constant and hence degrades the responsiveness of the system for high frequency signals. For example, using a high value pull up for I2C lines will decrease the speed of I2C communication due to the increased slew rate of the I2C lines. Therefore, these resister values determine the tradeoff between the various factors which affect the final design.
“...when it comes to selecting a capacitor for the design, electrolytic capacitors should be avoided because they have very high leakage current.�
Selecting the right passive components: Pull up and pull down resistors are commonly used components with interface switches, I2C devices, etc. Sometimes in a low power design, these pull up and pull down resistors consume more power compared to the rest of the system. To reduce the power consumed by them, higher values of resistance should be used. This decreases the amount of current passing through
Similarly, when it comes to selecting a capacitor for the design, electrolytic capacitors should be avoided because they have very high leakage current. Film capacitors and ceramic capacitors offer ultra low leakage current at a reasonable cost and can be considered for a low power system design. Using I/Os judiciously: Avoid distributing controller I/O pins randomly in a system. If pins are randomly distributed across different ports, then each port needs to be handled separately, which increases the number of register writes to control them. To overcome this issue, input and output pins can be grouped in the least number of ports, thus resulting in reading and writing with the least number of register writes.
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Power Developer Open-Drain drive mode for pins should be utilized where pin is driving LEDs and other similar load whose one end is fixed to either VDD or ground. This drive mode reduces leakage current through I/O pins and hence improves power consumption. Selecting the right external peripherals: Peripheral components which support low power modes and have low power consumption when active should be used in the system design to reduce overall consumption of the design. Utilize system clocks: Defining the behavior of the system clock can help in reducing the power consumption of a system. Following general system clock related design practices can help in achieving low power consumption in nearly every system. 1.
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Use a low frequency clock to reduce dynamic power consumption in the system.
2. Ramp up the system clock when it is executing computational extensive tasks to reduce average power consumption by completing the task in less time. 3. Prefer to use the system clock instead of an external clock 4. When the CPU is waiting for completion of a communication transfer, it should be shut down while keeping the clock ON for the communication block. After completion of the task, it can be given an interrupt to resume code execution. Gating currents: Normally, passive sensors like thermistors work in a potential divider mode and therefore always consume current in a system. To reduce power consumption in these scenarios, we can provide the power to the sensor network just before
TECH SERIES sampling them for data and remove power once data sampling is completed. This is useful in cases when sensors need to be read at regular intervals. Alternatively, when a sensor has to remain active to detect anomalies in the environment, the CPU can remain in low power mode during the whole sensing duration. The CPU can come back to active mode once it receives an interrupt/ data from the sensor. Similar logic can be used for reading switches to determine whether it is in ON or OFF condition.
consumption, can be reduced when one of these inputs are encountered. This can be demonstrated easily in applications wherein we need to find the values after doing some calculations like the sine and cosine of angles in motor applications. In such application,
Firmware Considerations Reduce function calls: Each function call is associated with multiple redundant operations like push and pop operations on the stack to reload the program counter and registers. Each of these operations consumes multiple clock cycles and should be avoided if possible. For short functions, function calls can be replaced by macros that place code inline. This helps reduce CPU loading and hence will reduce the power required for the same operation. However, everything has its own pros and cons. Macros require more memory, which can be an issue when writing tightly packed firmware as it may increase system cost. Use lookup tables for frequently repeating input values: Often there are inputs values that come more frequently than others. By creating a lookup table corresponding to these input values, computing time, and therefore power
there is a range of values which are encountered frequently compared to values that are out of this range. As it takes a long time to calculate sine or cosine values, pre-calculated values of the sine and cosine for the frequently repeated angles can be stored in a lookup table. Whenever one of those angles is encountered, the processor can look
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Power Developer into the table and substitute the value found there instead of calculating it.
Adaptive clock gating and power gating: A typical system uses multiple blocks of a microcontroller and at any given point of time, not all the blocks are used simultaneously. Thus, clock to these blocks can be gated to reduce the dynamic power consumed by these blocks and thereby conserve power. This also helps in reducing the peak current requirement, a critical consideration for coin cell operated designs. PSoC family of devices allows individually disable the blocks which are not in use.
“Most of the SoCs available today provide hardware blocks that can perform most of their tasks without intervention by CPU.� Use interrupts instead of polling: In a complex embedded system, the CPU spends most of its time waiting for something to complete before proceeding to the next step. Most of the SoCs available today provide hardware blocks that can perform most of their tasks without intervention by CPU. When they need CPU intervention, they can signal this with an interrupt that wakes the CPU. For example, normally ADCs gives an interrupt when they are ready with sampled data. This eliminates the need to poll for the data from the ADC. Thus the CPU can drop into a low power mode and wake only once the data is ready to be processed.
In this part, we covered general design considerations for creating a low power embedded system. In part II, we will cover examples of low-power applications, trade-offs between low power consumption and system performance, and offer an example of a low power system design utilizing the techniques discussed above.
About the Authors: Rahul Raj Sharma is an Application Engineer working in Cypress Semiconductors on USB devices. He has worked on PSoC applications and loves to do analog and mixed signal designs. He can be reached at rrsh@cypress.com rrsh@cypress.com. Tushar Rastogi worked as Applications Engineer in Cypress Semiconductors. He has worked on PSoC based applications since 2012. His responsibilities include PSoC firmware programming, application development, technical support to customers with programming, and boundary scan related issues tusr@cypress.com and technical writing. He can be reached at tusr@cypress.com.
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SEMITECH’S Bright Future Smart Grid Applications Target Alternative Energy Revolution It seems as if each day there is a gloomy new report on the state of the global environment. With greenhouse gas emissions and sea level readings at an all-time high, there is still a heavy dependence on traditional and environmentally hazardous resources. While alternative energy technologies like solar and wind have been developed in recent years, they have yet to gain the traction needed to make an impact on the dire state of Earth’s environment—until now.
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TECH REPORT
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Power Developer
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here is a new wave of smart grid technologies that aim to enable alternative energy technology in a way that makes them not only more efficient, but will totally revolutionize the power grid as we know it. At the head of this revolution is Semitech, an Australian-based semiconductor company that specializes in power line communication (PLC) devices. The company recently developed a line of PLC platform devices that dramatically increase the efficiency of solar arrays, lighting systems, and smart meters. EEWeb recently spoke with Zeev Collin, CEO of Semitech, about the company’s bright vision for the future of the power grid and their new line of devices that will jumpstart the smart grid revolution.
The Move to Micro The vision for smart grids has been around for a while now, but what exactly does a smart grid entail? For one thing, it means going from grid to grids—microgrids, that is. Through a network of integrated microgrids, a smart grid of the future would be able to manage power demands while simultaneously monitoring and healing itself. In order to achieve this, in-grid, machine-to-machine communication needs to take place. “This is where
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Semitech comes in,” Collin assured. “Through our platform devices, we can create a single platform that integrates all of the major computations and signal management components in inverter applications in the smart grid.”
The “
A netw
Managing Smart Grids The premise behind Semitech’s new line of PLC devices—the SM2400, SM2480, and SM2200—is to create a highly programmable grid that will in turn make it very flexible while maintaining cost and power efficiency. One of the areas of the smart grid that has gained the most attention in recent years has been solar. In the traditional solar panel array, there is a single power conversion box sitting at the back of the panels that converts all of the incoming solar energy from DC to AC, which is a requirement in feeding energy back into the grid. Inverters are implemented to perform this conversion, but the big problem is that there is a single point of failure for the entire array; in other words, if one panel of the array fails, then the rest fails with it. Higher efficiency can be achieved through management of microinverters on each panel of the array, meaning that each panel will become an independent generator of power that can all be injected to the grid.
In-Gr
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TECH REPORT
Through a network of integrated microgrids, a smart grid
of the future would be able to manage power demands “Smart Grid” – Vision for the Future while simultaneously monitoring and healing itself.
work of integrated microgrids that can manage demand, monitor and heal itself Building Automatio n
Grid Monitoring /Managemen t
Transmission Line & Distribution Monitoring
Active Lighting
Solar Farms
Distributed Power Management
Smart Meters EV Charging Station
Water Meter
Gas Meter
rid Machine-to-Machine Communication is Key to Smart Grid Success Semitech’s SM2480 eliminates traditional components, Semitech Semiconductor
meaning aConfidential simplified design and©2014 size reduction.
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Power Developer While this makes micro-inverters an obvious choice for future solar array development, there is one major setback: cost. “Despite all of the advancements,” Collin explained, “micro-inverters— and solar technology in general—are struggling to reach cost parity with traditional energy generation.” With Semitech’s SM2480 architecture comes a significant cost reduction for micro-inverters. The device eliminates traditional components, meaning a simplified design and size reduction. The PLC modem also allows for network connectivity, which is an inherent part of the micro-inverter. As Collin explained, “One of the biggest benefits of a
connected grid is remote management.” He went on to detail a potentially huge benefit in the case of a residential house fires; if there were a solar array on the roof of the house, the owner would be able to shut down the power coming from the grid without endangering the firefighters. This vision of the smart grid seamlessly integrates with remote management trends such as the Internet of Things, which is gaining significant momentum in the industry today.
Meeting Demands There will be a projected 30% increase in energy demands over the next 15 years. Alternative energy technology is not
Micro-Inverter Demo Setup Micro-Inverter Demo Setup
Feed to grid Feed to grid Two Micro Inverters are controlled by a Two Micro Inverters Gateway nodeby over are controlled a power linenode over Gateway power line
Controls Controls Micro-inverters are Micro-inverters are via remotely controlled remotely controlled GUI – each inverter via GUI each inverter has a– panel has a panel Page 11 Page 11
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Instantaneous measurements Instantaneous measurementsConfidential Semitech Semiconductor Semitech Semiconductor
Confidential
Time plot for voltages / currents Time plot for voltages / currents ©2014 ©2014
TECH REPORT Higher efficiency can be achieved through management of micro-inverters on each panel of the array, meaning that each panel will become an independent generator of power that can all be injected to the grid. only ready to supply the demand where traditional energy resources can not, but it will offer a unique way of managing the power needs in these smart grids of the future. Semitech is poised and ready to be at the forefront of smart grid implementation with its new line of PLC solutions. The goal: to be the
universal platform of the smart grid. This goal has been gaining its own traction— just recently, the Australian government awarded Semitech the single largest grant in the country’s history to help develop the SM24xx platform. With this monumental support, the smart grid revolution begins, one micro-inverter at a time.
SM2480 – Highest System Integration Traditional SM2480 Based Micro-Inverter SM2480 Micro-Inverter – Highest System Integration Traditional Micro-Inverter
SM2480 Based Micro-Inverter
Less components Simple design Less components Rich MPPT and control capabilities
•
Simple design SM2480 provides higher level of integration and control functions, thereby making the design simpler and dramatically reducing the cost of implementation Rich MPPT and control capabilities
• • SM2480 control functions specificallyand for control micro-inverter application, makingthe it uniquely SM2480 provides higherdesigned level of integration functions, thereby making design capable platform for MPPT and other control algorithms simpler and dramatically reducing the cost of implementation • • SM2480 based micro-inverter is capable of communicating with the application, grid using any one of a SM2480 control functions designed specifically for micro-inverter making it uniquely number of worldwide PLC standards, while performing control and monitoring functions, making capable platform for MPPT and other control algorithms it a truly universal micro-inverter platform • SM2480 based micro-inverter is capable of communicating with the grid using any one of a Semitech Semiconductor Confidential ©2014 Page 10 number of worldwide PLC standards, while performing control and monitoring functions, making it a truly universal micro-inverter platform Page 10
Semitech Semiconductor
Confidential
©2014
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Fully Integrated
Power
Maxim’s Power Products Enable the Most Demanding Applications Interview with Anthony Stratakos VP of Advanced R&D at Maxim Integrated
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INDUSTRY INTERVIEW
M
oore’s Law states that technology must improve on itself with every generation. In today’s industry, the rate of Moore’s Law seems to be increasing exponentially, with companies developing new and improved products every 24 to 36 months. However, Maxim Integrated—an industry-leading power management IC company— takes a different approach to product development. The
company’s Advanced Research and Development team develops fiveyear roadmaps for their power ICs, ensuring that the products they develop anticipate the needs of a rapidly changing industry. This is no easy task, and Anthony Stratakos, VP of Advanced R&D at Maxim, knows exactly what it takes. EEWeb spoke with Stratakos about anticipating the future, and some of the high level of integration that went into their new line of ICs.
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Power Developer Could you explain what “Advanced R&D” is? I have two primary responsibilities as the Vice President of Advanced R&D. The first is to enable a rolling five-year roadmap for our technologies. For power, this means our process technology, package technology, external components like magnetics, and the power topologies and architectures of our chips. My group is looking up to five years ahead to plan what our products are going to look like in the future. The business units design products using those technologies. Secondly, I am responsible for incubating new initiatives at Maxim, which are new businesses or vertical markets that are focused on integration of power into semiconductor devices.
What are some of the challenges of integrating power electronics and how is that enabling new technologies and applications? Power is very important to Maxim. Power electronics comprise a good percentage of our revenue; it touches nearly every group that we have. Maxim has a strong focus on power for automotive, industrial, mobile, and communications and data center applications. Integrating power
into these areas is the most challenging integration problem that exists in our industry. A decade or so ago, the semiconductor companies that were considered real technology leaders were those who were pioneering mixedsignal semiconductors. The reason they were considered at the cutting edge of integration is not just because they were integrating so many functions on a single chip, but because it was believed that monolithic integration of sensitive analog and noisy digital circuits was the most severe design challenge. The integration of power together with the digital and sensitive analog functions is orders of magnitude more complex than this early mixed-signal design challenge because the power circuits create a switching noise problem that is so much more severe.
Now that you have been able to integrate analog and digital with power electronics, what have you and your customers been able to do with them? What are some of the new technologies and applications that have opened up? There are two types of power integration that are most important to Maxim. The first is high power: fully-integrated, highcurrent regulators that are used in the most demanding high-power applications such as CPUs, memory, and other system-on-
“The integration of power together with the digital and sensitive analog functions is orders of magnitude more complex than early mixed-signal design challenges.”
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INDUSTRY INTERVIEW “Maxim has integrated as many as 50 power management functions on a single chip, which helps to enable smaller form factors [in devices].�
chip devices. This integration of highcurrent power provides the smallest and most efficient form of power electronics available today and has enabled a host of new applications and form factors, particularly in the data center and communications spaces. There has been a large and growing demand for high current power supplies in surprisingly small spaces in enterprise equipment. The power density challenge has also been increased by the proliferation of smaller form factors, from tower servers to 1U racks and blades, and the need for higher port densities in switches and routers. These factors, combined with the fact that power electronics is typically one of the biggest consumers of motherboard area in these systems, has driven the need for increasingly more efficient power supplies with higher power densities. We have answered these challenges by investing in our technology roadmap and have decreased the power losses in our chips by a factor of four, while increasing the current density of our solutions by a factor of nearly twenty. This, in turn, has helped to drive the density of communication, datacenter, and enterprise equipment.
The second type of integration that Maxim specializes in is multi-function power management ICs (PMICs). On these PMICs, Maxim has integrated as many as 50 power management functions on a single chip, which helps to enable smaller form factors in everything from handheld mobile applications, like phones and tablets, to equipment as large as enterprise-class routers and switches.
What functionality are you integrating into the PMIC and what does that do to component count and board space requirement? Our PMICs integrate the vast majority of the power management components that are required in the application and include functions like buck converters, boost converters, linear regulators, and battery management. The PMIC offers a very dramatic savings in board area compared to solutions that are fully discrete; it’s typically a factor of two or more smaller.
How does the high level of integration affect efficiency? High integration results in a very large savings in energy consumption. This comes primarily from the fact that
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Power Developer the power components are so much more tightly coupled. The resulting reduction in parasitics allow either higher efficiency or the retention of efficiency at higher switching frequencies.
“High integration results in a very large savings in energy consumption. This comes primarily from the fact that the power components are so much more tightly coupled.”
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The applications where this has had the most surprising impact have been in the enterprise space. For example, it typically costs more to operate a data center than it does to build it. The energy savings that are enabled by our integrated power electronics in data centers, in many cases, can actually pay for the cost of those power electronics. In other words, based on just the energy cost savings, the power electronics are virtually free.
Typically, most companies are looking ahead 24 or 36 months down the road as opposed to your team’s five-year roadmaps. How do you predict the problems you might encounter that far down the road? When we look five years in the future, we still see the primary challenges of power management being the need for increased power density, increased efficiency, and lower cost. We are going to address these challenges through integration and by advancing an aggressive five-year technology roadmap that continues to drive large generational improvements of our products. Moore’s Law taught us long ago that technology needs to improve with every generation. This is true for power, so we are driving these aggressive roadmaps to anticipate our customers’ needs.
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ROHM
BD14000EFV-C Cell Balancer IC The BD14000EFV-C supercapacitor cell balancer IC from ROHM directly addresses regenerative power demands such as increased battery life, miniaturization, and stability. With over 20 discrete components on a single IC, the BD14000EFV-C is the industry’s first monolithic supercapacitor cell balancer. The monolithic design enables a 38% mounting area reduction, leading to smaller and more robust regenerative power sources.
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PRODUCT WATCH
ROHM BD14000EFV-C Cell Balancer IC
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Power Developer Hardware
3 1
Demo Capacitor Mounting Points
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2
Capacitor Balance Status LEDs
BD14000EFV-C TSSOP Package
PRODUCT WATCH
Specs Supercaps have many advantages for applications like hybrid vehicles and industrial equipment; they can handle literally hundreds of thousands of charge cycles, they can charge and discharge orders of magnitude faster than electrochemical batteries, and they have very low internal resistance. The BD14000EFV-C eliminates the time and complexity involved with these custom designed circuits while providing protection against cell imbalances that affect current load. This small device comes in a 10mm by 7.6mm TSSOP package and can easily integrate into control circuitry with minimal impact on footprint. The BD14000EFV-C is ideal for the automotive industry, but it can also be integrated into any scenario that uses supercaps, such as with production machinery, building machinery, uninterruptible power supplies or any other devices that stabilize power supplies.
Watch Video To watch an overview of BD14000EFV-C, click the image below:
click here
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