Eliminating deadtime mismatch due to inserting storage capacitor of a GaN-based two-phase series-capacitor buck DC-DC converter

Abstract

Due to the series capacitor charging period miscalculation, the applicability of the current sharing mechanism (CSM) of two-phase series-capacitor buck switching topology (2-pscB) for high-power electronic applications is still very limited. For traditional half-bridge gate driving circuits, inserting a series capacitor between power switches of phase A increases loop parasitic inductance, introduces a time delay mismatch between the gate voltages of the two switches, and causes interference with the synchronization of the deadtime between both phases of 2-pscB converters since phase B has no series capacitor. Using traditional half-bridge gate driving circuits in 2-pscB, the turn-off delay of phase A switches caused by its CDS discharging period appears amplified by parasitic effects and the phases' sinking path mismatch. This will eventually result in almost no deadtime conduction. To tackle this problem, this paper proposes a novel isolated eGaN gate driver circuit to accommodate an energy storage capacitor with an overall efficiency of 94%.