Fully Integrated Overcurrent Protection Method During SiC MOSFET Conduction

A gate driver IC with fully integrated overcurrent protection functions developed for IGBTs is successfully applied to overcurrent protection for SiC MOSFETs. In the gate driver IC, while the SiC MOSFETs are ON, constant gate charge is periodically discharged and charged, and when gate-to-source voltage dropped by each discharge is less than the reference voltage, it is detected as the overcurrent and the SiC MOSFETs are immediately turned off to protect from the overcurrent. Overcurrent protection can be achieved at low cost, since external components such as high-voltage diodes are not required. While the overcurrent detection threshold is constant and cannot be changed for IGBTs, it is found for the first time in SiC MOSFETs that the overcurrent detection threshold can be varied by changing the gate charge to be discharged. In a single-pulse test of an inductive load at 300 V for an SiC MOSFET with DC rating of 134 A and pulse rating of 240 A, the gate driver IC successfully protected the overcurrent with the protection delay of 226 ns or less, while the overcurrent detection threshold is variable in the range of 104 A to 306 A.