Zero Inductor-Voltage Multilevel Bus Converter

Abstract

A novel topology to achieve 4:1 voltage step down, aimed at 48 V to 12 V conversion in data center applications, is presented. The so-called dc-transformer topologies have become a very active area of research to improve the overall efficiency of data centers in response to a shift from a 12 Vdc bus architecture to a 48 Vdc bus architecture. In particular, switched-capacitor topologies have been investigated due to their high power density, efficiency, and low reliance on magnetics. However, switched-capacitor topologies have challenges associated with the hard-charging of capacitors and are often forced to make design compromises that reduce their overall performance. The proposed topology maintains many of the advantages of a switched capacitor topology, such as reduced component stresses, and very low reliance on magnetics, while also inherently avoiding any hard-charging of the flying capacitors. This allows the converter to operate at a very low frequency, such as 60 kHz, with a small inductor, such as 100 nH, and use low voltage stress devices to achieve a peak efficiency of more than 99% for 48 V to 12 V conversion and a power density of 800 W/in <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sup> .