Design Article
Green power to the people everywhere
Tony Armstrong, Linear Technology Corporation
7/31/2012 10:22 AM EDT
Green power opportunities
Any products targeted toward green energy or energy harvesting will see growth opportunities in 2012 and beyond. Energy costs and environmental concerns, as well as the need to extend battery life for mobile devices, has resulted in a focus on power optimization for a broad range of applications. Our energy-efficient products enable customers to convert power more efficiently, consume less power and extend battery life.
The market for portable solar-powered electronic devices continues to grow as consumers look for ways to reduce energy consumption and spend more time outdoors. Because solar power is variable and unreliable, nearly all solar-powered devices feature rechargeable batteries. Clearly, the goal is to extract as much solar power as possible to charge these batteries quickly and to maintain their state of charge.
However, solar cells are inherently inefficient devices, but they do have a point of maximum output power, so operating at this point is an obvious design goal. The problem is that the IV characteristic of maximum output power changes with illumination. A mono-crystalline solar cell’s output current is proportional to light intensity, while its voltage at maximum power output is relatively constant. Maximum power output for a given light intensity occurs at the knee of each curve, where the cell transitions from a constant-voltage device to a constant-current device. Therefore, a charger design that efficiently extracts power from a solar panel must be able to steer the panel’s output voltage to the point of maximum power when illumination levels cannot meet the charger’s full power requirements.
Green power is not only limited to the generation of energy via energy scavenging, it is also symbiotic to using less energy to do the same function. One area where this is already having a significant impact is digital system power management. When digital power is done correctly, it can reduce data center power consumption, shorten time to market, have excellent stability and transient response and increase overall system reliability, in networking equipment for example.
System architects of networking equipment are being pushed to increase the data throughput and performance of their systems as well as add functionality and features. At the same time, pressure is being applied to decrease the systems overall power consumption. In data centers, the challenge is to reduce overall power consumption by rescheduling the work flow and moving jobs to underutilized servers, thereby enabling shutdown of other servers. To meet these demands, it is essential to know the power consumption of the end-user equipment. A properly designed digital power management system can provide the user with power consumption data, allowing for smart energy management decisions to be made.
Furthermore, a principal benefit of digital power system management is reduced design cost and faster time to market. Complex multi-rail systems can be efficiently developed using a comprehensive development environment with intuitive graphical user interface (GUI). Such systems also simplify in-circuit testing (ICT) and board debug by enabling changes via the GUI instead of soldering in “white wire” fixes. Another benefit is the potential to predict power system failures and enable preventive measures, thanks to the availability of real-time telemetry data. Perhaps most significantly, DC/DC converters with digital management functionality allow designers to develop “green” power systems that meet target performance (compute speed, data rate, etc.) with minimum energy usage at the point of load, board, rack and even installation levels, reducing infrastructure costs and the total cost of ownership over the life of the product.
Linear Technology’s LTC3880 is a dual output synchronous step-down DC/DC current mode controller with integrated power FET gate drivers and comprehensive power management features accessed via the I2C-based PMBus. The product’s precision reference and temperature-compensated analog current-mode control loop offer ±0.5 percent DC accuracy, easy compensation that is calibrated to be independent of operating conditions, cycle-by-cycle current limit, and fast and accurate current sharing and response to line and load transients without any of the ADC quantization-related errors found in products utilizing “digital” control. The LTC3880 incorporates a 16-bit data acquisition system that provides digital read back of input and output voltages and currents, duty cycle and temperature. The part also includes a fault logging capability via an interrupt flag along with a “black box” recorder that stores the state of the converter operating conditions just prior to a fault. Multi-rail system development is facilitated though LTC’s LTpowerPlay™ development software and GUI interface.
Next: How much power is there?
Any products targeted toward green energy or energy harvesting will see growth opportunities in 2012 and beyond. Energy costs and environmental concerns, as well as the need to extend battery life for mobile devices, has resulted in a focus on power optimization for a broad range of applications. Our energy-efficient products enable customers to convert power more efficiently, consume less power and extend battery life.
The market for portable solar-powered electronic devices continues to grow as consumers look for ways to reduce energy consumption and spend more time outdoors. Because solar power is variable and unreliable, nearly all solar-powered devices feature rechargeable batteries. Clearly, the goal is to extract as much solar power as possible to charge these batteries quickly and to maintain their state of charge.
However, solar cells are inherently inefficient devices, but they do have a point of maximum output power, so operating at this point is an obvious design goal. The problem is that the IV characteristic of maximum output power changes with illumination. A mono-crystalline solar cell’s output current is proportional to light intensity, while its voltage at maximum power output is relatively constant. Maximum power output for a given light intensity occurs at the knee of each curve, where the cell transitions from a constant-voltage device to a constant-current device. Therefore, a charger design that efficiently extracts power from a solar panel must be able to steer the panel’s output voltage to the point of maximum power when illumination levels cannot meet the charger’s full power requirements.
Green power is not only limited to the generation of energy via energy scavenging, it is also symbiotic to using less energy to do the same function. One area where this is already having a significant impact is digital system power management. When digital power is done correctly, it can reduce data center power consumption, shorten time to market, have excellent stability and transient response and increase overall system reliability, in networking equipment for example.
System architects of networking equipment are being pushed to increase the data throughput and performance of their systems as well as add functionality and features. At the same time, pressure is being applied to decrease the systems overall power consumption. In data centers, the challenge is to reduce overall power consumption by rescheduling the work flow and moving jobs to underutilized servers, thereby enabling shutdown of other servers. To meet these demands, it is essential to know the power consumption of the end-user equipment. A properly designed digital power management system can provide the user with power consumption data, allowing for smart energy management decisions to be made.
Furthermore, a principal benefit of digital power system management is reduced design cost and faster time to market. Complex multi-rail systems can be efficiently developed using a comprehensive development environment with intuitive graphical user interface (GUI). Such systems also simplify in-circuit testing (ICT) and board debug by enabling changes via the GUI instead of soldering in “white wire” fixes. Another benefit is the potential to predict power system failures and enable preventive measures, thanks to the availability of real-time telemetry data. Perhaps most significantly, DC/DC converters with digital management functionality allow designers to develop “green” power systems that meet target performance (compute speed, data rate, etc.) with minimum energy usage at the point of load, board, rack and even installation levels, reducing infrastructure costs and the total cost of ownership over the life of the product.
Linear Technology’s LTC3880 is a dual output synchronous step-down DC/DC current mode controller with integrated power FET gate drivers and comprehensive power management features accessed via the I2C-based PMBus. The product’s precision reference and temperature-compensated analog current-mode control loop offer ±0.5 percent DC accuracy, easy compensation that is calibrated to be independent of operating conditions, cycle-by-cycle current limit, and fast and accurate current sharing and response to line and load transients without any of the ADC quantization-related errors found in products utilizing “digital” control. The LTC3880 incorporates a 16-bit data acquisition system that provides digital read back of input and output voltages and currents, duty cycle and temperature. The part also includes a fault logging capability via an interrupt flag along with a “black box” recorder that stores the state of the converter operating conditions just prior to a fault. Multi-rail system development is facilitated though LTC’s LTpowerPlay™ development software and GUI interface.
Next: How much power is there?
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docdivakar
8/1/2012 6:07 PM EDT
The numbers in the Table for solar panel don't look right to me. With solar constant at ~1400W/m^2 and accounting for atmospheric attenuation, albedo, etc., let us say an insolation of 800W/m^2 which works out to 0.08W/cm^2. With solar panel efficiencies at 10 to 20%, this is few 10's of mW/cm^2, NOT few 100's claimed in the table.
The article otherwise a smorgasboard of Linear's solutions!
MP Divakar
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I_B_GREEN
8/3/2012 6:56 PM EDT
efficiency is always important.
Your available usable power is the product of efficiency and non usable (without tranformation) available power.
zero times anything is still zero
10% times anything only allows 10% of the energy use...
But I do understand why this is being framed in this way. If you are going to convert these types of power sources you cannot expect to get to conventional efficiencies considered norms in normal power suppl design.
Thus the lowered expectations framing of the issue.
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