Quasi-Flying Gate Concept Used for Short-Circuit Detection on SiC Power MOSFETs Based on a Dual-Port Gate Driver

The proposed dual-port gate driver architecture relies on a quasi-flying gate concept to protect SiC power mosfets against short-circuit events. Hard switching faults (HSFs) extract charges from the gate by causing a leakage current toward the source, while faults under load (FUL) lead to charge injection into the gate through the reverse transfer capacitance (C-GD). Such phenomena lead to perturbations of the gate-source voltage (V-GS), which are amplified by the gate resistor, acting as an enhancer of short-circuit signatures. Thus, a small gate resistance is used to ensure high switching dynamics, while a larger one is switched on during pulsewidth modulation on-state operation to identify possible faults. A dual-port gate driver is then proposed to ensure fast switching with HSF and FUL monitoring. The fault detection scheme relies on comparing two thresholds to V-GS relative changes to the nominal gate voltage. Experimental results using TO-247 package 1.2-kV/36-A SiC mosfets exhibit promising inverter leg short-circuit detection and protection against faults in less than 300 ns.