DC-DC High Step-Down Split Converters with Low Inductor Current and Low Voltage Stress - Results for GaN-based Design

Abstract

This paper presents a concept of a DC-DC dual split buck converter with divided input voltage and a structure using two DC-DC switch-mode converters that supply the output capacitor in parallel. All components in the converter have reduced voltage stress and the average current value of their inductors is reduced by about twofold compared to that of a buck converter. In the demonstrated implementation with GaN transistors, the converter achieved an efficiency higher than that of the buck converter, and its power range is also larger. The paper also proposes a solution where, at the output of the converter, there is a stack of capacitors with various configurations of connection with the converter modules and load. Depending on the configuration, we achieve an output current ripple cancelation, a further reduction by half in the average value of the inductor current, and a larger voltage control range. In addition, the converter operates with low voltage stress and has more than one output. An integral part of the converter in this configuration is an output balancing circuit. In the proposed implementation, this is a resonant switched-capacitor (SC) ladder converter based on low-voltage transistors of low resistance. This article contains results of experimental research on both types of converters based on GaN transistors with 400 kHz output current ripple and balancing circuit operation.