Quasi-square wave converters-modeling and performance benefits of GaN over Silicon

This paper presents an accurate loss model of a Quasi-Square Wave (QSW) buck converter and analyzes the efficiency benefits of GaN FETs over Silicon super-junction FETs. A design methodology and optimization strategy is presented while accounting for the FET Figures-of-Merit (FoM). The model uses computational techniques to account for non-linear device capacitances and precisely predicts the FET on times, resonant intervals and switching frequency required for ZVS operation. Analyses show the FET R
_DS
,
_ON
-QOss FoM has the maximum impact in the efficiency affecting both FET and inductor losses and a FoM dependent optimal R
_DS
,
_ON
exists for which the FET conduction losses balance the inductor losses. The loss model is validated by two QSW buck converters designs operating at 36W using GaN and Silicon FETs, each optimized to maximize their end-to-end efficiencies.