Investigation and evaluation of high power SiC MOSFETs switching performance and overshoot voltage

Silicon Carbide (SiC) MOSFETs, which are wide-bandgap semiconductor devices, have the capability to switch at much higher frequency in comparison with their silicon (Si) counterparts. High di/dt during fast switching transients will lead to semiconductor device failure due to overshoot voltage. It is a common belief that a snubber circuit is necessary for implementing the SiC MOSFETs into designs. However, this study shows that if stray inductance in the current commutation loop (CCL) is minimized with the combination of DC film capacitors and a two-layer laminated bus bar, there is not a need for snubber capacitors to suppress voltage overshoots. A 1200V 800A complete SiC MOSFETs based power structure is built for study. Theoretical model and SPICE model are built. The switching performances with DC electrolytic capacitors, film capacitors and snubber capacitors are evaluated with both SPICE based simulation and experiments, which proves that the snubber circuit can be removed.