Analysis and Simulation of Transformer Isolated High Current 48 V DC Power Supply with DC-UPS Capability Based on SCALDO Technique for Google's New Open Rack Power Architecture

摘要

Energy efficiency of power converters used in computer server farms is a major issue today since these facilities consume huge amounts of energy on a continuous basis. In 2016, Google introduced a 48 V rack power architecture at the Open Computing Project (OCP) summit to replace 12 V, and announced their plans to shift towards 48 V DC rails with DC-UPS. This was with the main target of reducing ohmic losses in the DC-distribution by 16 times and transformer losses by 30%. Compared to well-developed switching converter techniques, a new linear high efficiency RFI/EMI free DC-DC converter technique, namely SCALDO, has the potential to be used for these 48 V DC server power supplies. This paper presents analytical and simulation details of an electrically isolated, 48 V DC, 20 A extended-SCALDO based design. Experimental validation of this technique has been established by developing a proof of concept prototype, a scaled down 30-to-6-V DC converter. The paper highlights the advantages of combining the fly-back and forward modes similar to a switching converter, for charging a supercapacitor bank which acts as energy reservoir, where the final 48 V DC rail is regulated by a simple SCALDO converter extended to supply 20 A, and achieving DC UPS capability by over-sizing the supercapacitor.