Short-circuit protection of 1200V SiC MOSFET T-type module in PV inverter application

A de-sat based short-circuit protection scheme using commercial driver for SiC MOSFETs is presented and experimentally verified on 1200V 3-level T-type SiC MOSFET module in this paper. Response time is very critical for the short-circuit protection of SiC MOSFETs due to the limited short-circuit withstand time (SCWT). Soft turn-off is required to avoid high voltage spike during the turn-off of the fault current. With the presented circuit, 600 ns response time is realized, and a two-stage soft turn-off circuit with gate voltage clamping is implemented. A gate voltage stabilizing circuit without affecting the switching loss is also proposed to prevent false trigger. Since de-sat protection scheme is not applicable for the neutral branch of T-type module due to polarity changes of branch voltage, the short-circuit protection of neutral branch is realized with the half-bridge device protection. Detail circuit design for the 1200 V T-type SiC module in 1 kV PV application is described, and experimental results demonstrate the effectiveness of the circuit.