Welcome to a Special Issue of Electronic Design focused on power. Why? For starters, power is a universal topic for all electronic design. Beyond that, on a global scale, power is at the top of environmental and political agendas due to growing demand in the developing world. Concerns about energy consumption, global warming, and greenhouse emissions are spotlighting energy efficiency, alternative energy sources, and smart power management. Efficient public transportation and hybrid vehicles are in demand. So are "green" buildings that manage energy efficiently via "smart" lighting and HVAC systems that employ computing and communications to calculate optimal energy use.
While alternative power sources draw ever closer, improved power design in today's electronics can have immediate global impact—one watt at a time. According to the EPA, over 3 billion power-supply units are in use in the U.S., with more than 10 billion globally. Their efficiency, according to the EPA, has plenty of room for improvement. On average, they're only about 50% to 70% efficient and waste up to half the electricity that flows into them.
To address this problem, the EPA is promoting a new Energy Star external power supply (EPS) specification. The Energy Star program ties to worldwide regulatory standards for power supplies. In fact, because so many power supplies are manufactured in China, the EPA worked with the China Certification Center for Energy Conservation Products (CECP) to develop the specs.
WATT YOU CAN DO
Efficient power supplies enable you readers to make a substantial impact on our global energy situation. The EPA estimates total electricity flowing through power supplies in the U.S. at 207 billion kWh/year, equal to about $17 billion/year or 6% of the nation's electric bill. Implementing the Energy Star efficiency guidelines could save about 3% of U.S. electricity. (The Energy Star efficiency rating varies based on a product's output power. In the table, PNO stands for nameplate output power, and Ln refers to the natural logarithm.)
The second half of the Energy Star specification is the No-Load power requirement (standby power standards). For products with outputs of less than 10 W, the no-load consumption goal is 0.5 W or less. Products outputting 10 to 250 W have a standby goal of 0.75 W or less. (My Dec. 8, 2004 column on standby power generated some interesting comments from readers. Check out ED Online 9258.)
Once the voluntary product specifications and labeling are in place, the EPA will launch a campaign to boost consumer demand for the efficient power supplies. The Energy Star program will recognize the most efficient models on the market. OEMs will mark their products with an efficiency level (levels 3 to 6 will qualify as energy efficient) based on the Energy Star Test methods, factoring in both Active and No-Load requirements.
The energy efficiency in most electronic devices today starts with the choice of power semiconductors. Updating you on some of the latest choices, Don Tuite looks at the importance of power factor correction and efficiency mandates as influences on developments in power discretes (page 59).
MEMS FUEL CELLS
In designing portable electronics, the quest for greater power efficiency takes on a true make-or-break dimension. Longer battery life is at the top of consumer considerations in devices like cell phones and music players. Portable fuel cells promise to revolutionize portable power. Roger Allan examines the introduction of MEMS microstructures in the burgeoning area of miniature fuel cells and in miniaturized MEMS-based power generators using permanent-magnet motors (page 43).
But power management runs even deeper in today's advanced electronics. As process geometries move to 65 nm and beyond, thermal management is increasingly seen as a design limiter. Indeed, in response to a Quick Poll question on our Web site about the importance of power integrity as an SoC design constraint, 18% of you said that power integrity was on par with speed and area, while 41% characterized power integrity as a "growing concern." Intel CTO Pat Gelsinger has presented a trajectory of power density that shows current chips at about the level of a hot plate—on track to ramp up to a rocket nozzle, followed by a nuclear reactor, and finally to the surface of the sun!
While that trajectory is sure to change course before melting down, today's blistering power densities still require efficient thermal management. On that note, Sam Davis presents cutting-edge products that help create a smart thermal-management system to cool down those power-packed systems (page 49).
I hope you find the issue a hot one!
|ENERGY-EFFICIENCY CRITERIA FOR ACTIVE MODE|
|Nameplate output power (PNO)||Minimum average efficiency in active mode (expressed as a decimal)|
|0 to ¾1 W||>=0.49 * PNO|
|>1 to ¾49 W||>=\[0.09 * Ln (PNO)\] + 49|