A short circuit protection circuit for SiC MOSFET with self-adjustive blanking time

Abstract

This paper proposed a desaturation (DESAT) short circuit (SC) protection circuit for SiC MOSFET, where a blanking time setting module and an SC detection module are designed. The fall time of the drain-source voltage (V_DS) for each switching period of SiC MOSFET is recorded and set as the blanking time for the hard switching fault (HSF) detection in the next switching period. Consequently, the detection delay for HSF is self-adjustive and can respond quickly to the operating state of SiC MOSFET. FPGA and discrete components are used to implement the proposed circuit. The function of the proposed circuit is verified using the double pulse test. The experiment results show that the blanking time automatically increases with the increase of load current. The default detection delay of the proposed protection circuit is set 240ns for HSF and can be adjusted during the subsequent switching period. So in the test under a 400V bus voltage, the detection delay is 240ns for HSF at the first switching period. And for HSF occurs at the second switching period, the detection delay is 200ns adjusted according to the operating state of the first switching period. Meanwhile, the detection delay for fault under load (FUL) is 72ns.