Design and optimization of a wide dynamic range programmable power supply for data center applications

Abstract

A point-of-load (PoL) voltage regulator module (VRM) with high efficiency, conversion ratio and power density can enable dense integration of CPUs in data centers, and subsequently increase the overall data center energy efficiency. State-of-the-art VRMs are already quite small and achieve high peak efficiencies. However, given the variable nominal load currents of these VRMs in response to changing computational loads of the data centers, a flat high-efficiency response is more desirable. This paper presents a programmable VRM with a flat < 90 % efficiency response over a wide load dynamic range. The proposed programmable VRM is based on multiphase interleaved synchronous buck topology with phase shedding. An extensive exploration of different power switch technologies has been performed in order to obtain the most suitable MOSFET technology for this topology. Our design space exploration also included sweeping the voltage conversion ratio, passive components and switching frequency. The finalized programmable VRM, using discrete Si-MOSFETs, performs a 12-1 V DC-DC conversion with an operating load range of 10 - 200 A and a switching frequency of 200 kHz. Experimental characterization of the VRM demonstrates an efficiency of 92.2 % across the wide load range of 10 - 200 A, confirming design simulations with a maximum relative error of 0.7 %.