Short-Circuit Fault Adaptive Analysis and Protection for SiC MOSFETs

Aiming at the short-circuit (SC) capability for silicon carbide (SiC) MOSFETs due to the limitation of the gate oxide process, that is, the ability of MOSFET to withstand large current and high voltage when the channel is turned on, this article summarizes and analyses various SC fault types for SiC MOSFETs, which are further simulated through a designed SC test platform with strict timing of control signals. Aiming at the well-explored hard switching fault (HSF) and fault under loading (FUL), the connection between these two and other SC faults is derived, which brings about the proposed improved SC fault adaptive detection and protection in the driving scheme. Because the shorter SC withstand time of SiC MOSFETs puts forward a higher requirement for the response speed, which contradicts the risk of false-triggering, namely, the poor noise immunity caused by merely reducing blanking time. Therefore, the improved SC detection scheme combining drain–source and gate voltage signals proposed in this article enhances the self-adaptation to different SC fault types of SiC MOSFETs through variable blanking time setting, thereby effectively accelerating the detection speed as well as suppressing the SC current, on the premise of ensuring reliable, compatible SC protection.

I. Introduction

Thanks to the superior properties of silicon carbide (SiC) as the wide bandgap semiconductor material, compared with traditional silicon (Si)-based devices, SiC power devices effectively improve the conversion efficiency and power density of power electronic converters, thus existing higher advantages in widely applied fields, e.g., rail transportation, renewable energy, and electric vehicles [1], [2]. Meanwhile, due to the ideal characteristics, power MOSFETs have achieved a mature and widespread application in Si-based devices. As a result, when it comes to the new generation of SiC power devices, the combination of SiC and MOSFET is still the most attractive switching device. However, we cannot ignore that the reliability of SiC MOSFETs under abnormal operating conditions, especially the short-circuit (SC) operation, has become a critical obstacle in long-term operations [3], under which the device comes across unexpected turn-on or negligible load inductance. Therefore, the SC operation has achieved extensive attention since the device bears both a huge current and a large voltage at the same time, which may lead to serious consequences if left untreated [4].