Design and Performance Evaluation of a Short-circuit Protection Scheme for SiC MOSFETs

Abstract

Compared to other silicon-based devices, silicon carbide (SiC) MOSFETs suffer from a shorter short-circuit withstand time and degradation after repeated short-circuiting, which challenges the short-circuit protection circuit design for SiC MOSFETs. In this paper, a short-circuit test platform for SiC MOSFETs is designed and built. Based on the test platform, the relationship between gate voltage, short-circuit withstand time and the short-circuit peak current overshoot is measured and discussed. Based on the test results, a lower gate voltage can significant increase the short circuit withstand time and decrease the short-circuit current. And a short-circuit protection scheme with a soft turn off circuit is proposed and designed, which can achieve fast short-circuit protection response with reduced fault peak current under hard switching fault condition. The soft turn-off circuit can also effectively suppress the voltage overshoot caused by the power loop stray inductance. Compared to the hard turn-off condition, the voltage overshoot can be reduced from 124V to 40V at the same condition using soft-turn off.