Comparison of Three Methods [Gate Bias Reduction, Series Ballast Resistor, and BaSIC(EMM)] to Improve Short Circuit Capability of 1.2 kV SiC Power MOSFETs

Abstract:
Silicon Carbide Power MOSFETs have been commercialized to replace Silicon IGBTs in power conversion applications such as PV inverters. However, the short-circuit (SC) ruggedness of SiC Power MOSFETs must be enhanced to match that of Si IGBTs for application in motor drives. Three methods to improve the SC capability are compared in this paper. The user-programmable method, BaSIC(EMM), with a series-connected, Si Enhancement Mode MOSFET (EMM), is demonstrated in this paper to be superior to the reduction of SiC power MOSFET gate drive voltage or the addition of a series ballast resistance. The SC withstand time (tSC) of 1.2 kV SiC power MOSFETs was improved from 3.5 mus to 6.5 mus (1.86x) with only 4% increase in on-resistance (RON) by using BaSIC(EMM). In contrast, the series ballast resistance (SBR) produced a 1.94x improvement in tSC with 37% increase in RON and the gate bias reduction (GBR) from 20 to 15 V produced a 1.8x improvement in tSC with 31% increase in RON. In addition, the drain electrode of the EMM in the BaSIC topology can be used as a sensing node to monitor on-state current level and to detect short circuit events.