Investigation of acceptable breakdown voltage variation for parallel-connected SiC MOSFETs during unclamped inductive switching test

Abstract

Current flowing through parallel-connected SiC MOSFETs are imbalanced during unclamped inductive switching (UIS) test, which can be imaged as the emergency interruption of solid-state circuit breakers, due to variations of breakdown voltage. The imbalanced current can drive devices into thermal destruction. This study evaluated acceptable breakdown voltage variations of two parallel-connected SiC MOSFETs under different total current, load inductances, and breakdown voltage temperature coefficient conditions during UIS mode operation by numerical simulation. The acceptable variation at 298 K was found to decrease with increasing total current and be influenced by the change of total current greater with larger inductances. SiC MOSFETs with larger breakdown voltage temperature coefficients allowing larger variations were also clarified.