Analyzing false turn-on events with varying gate drive parameters in high voltage GaN devices

Abstract

In this paper, we address the problem of false turn-on effects in a half-bridge GaN power converter in terms of circuit and device parameters. The model shows that the inherent false turn-on problem is caused by slew rates dvdsdt and dvgsdtduring the switching transients occurring at the turn-on and off phases. A higher slew rate propagates the gate driver voltage to overshoot beyond the threshold voltage causing it to accidentally turn on This study shows that dvdsdt is dependent on the internal device parameters such as gfs (transconductance) and Coss(output capacitance). From the CV characteristics, it is pretty much evident that the internal capacitances Cossand Crss (reverse transfer capacitance) are reduced with higher drain voltage enabling higher slew rates which increases the probability of false turn-on problems. Experimental results at numerous operating points at 400 V with the variation in different gate drive parameters support the analysis.