New power semiconductors cut data center energy

Steven Sapp, Ritu Sodhi, and Sampat Shekhawat of Fairchild Semiconductor

March 3, 2010

Steven Sapp, Ritu Sodhi, and Sampat Shekhawat of Fairchild Semiconductor

The vast arrays of computers around the world consume huge amounts of power. The Data centers that enable the internet exemplify this power usage. As much as 1.2% of the power consumed in the entire U.S. alone is consumed by servers. Worldwide in 2005 more than $7 B dollars was spent on powering servers and the infrastructure supporting them - requiring the equivalent capacity of fourteen 1,000 MW power generating facilities.

Compounding the energy use problem is the waste associated with power conversion and conditioning, distribution, and environmental control including air conditioning. In a typical data center less than half of the power consumption goes into the computing function. Data center operators are looking at every opportunity to increase power conversion and distribution efficiency including eliminating the number of conversion stages through the distribution of high voltage direct-current sources.

In the U.S. the electric grid distributes AC power to local communities at around 13,800 vac. That is eventually stepped-down to 480 vac using transformers that do not contribute significantly to energy loss. The data centers almost always have an Uninterruptible Power Supply, commonly a double-conversion on-line UPS that continuously generates a new clean sine wave output from the rectified AC mains or a battery, so there is no switch over interruption. This stage of the power conditioning may be only 70% efficient.

At the server rack the 208 vac power is converted to 12 or 48 vdc and stepped down to the bus voltages required for the processor, disk drives, and memory. Both the double-conversion UPS and switched-mode AC/DC converter benefit from high performance semiconductor components like, IGBTs, and super-junction power MOSFETs for rectification, battery charging, and DC/AC inverting.

Power Conversion Stages in a typical data center Click on image to enlarge.