High-Conversion Ratio Multi-Phase VRM Realized with Stacking of Generic Series-Capacitor-Buck Converter Cells

Abstract

This paper introduces a new design approach for multiphase nonisolated DC-DC topology. The design approach is based on a new generic hybrid cell that consists of both capacitor and inductor. Using a stand-alone cell, the approach contributes to a high modularity of the resulting converters and enables high conversion ratios at higher efficiencies. The unique interaction between the capacitor and the inductor result in a soft charging operation, which curbs the losses of the converter, and contributes to higher efficiency. The method was used to create a multiphase voltage regulator module VRM. The new converter significantly extends the effective duty ratio and lowers the voltage stress of the transistors, while delivering high current to the output and has inherent current sharing to balance the load between the phases. Experimental results of a modular interleaved three phase prototype demonstrate an excellent proof of design methodology concept and agree well with the simulations and theoretical analyses developed in this study. Typical applications are point-of-load (PoL) and voltage regulator modules (VRM).