Surge Current Robustness of 1.2 kV SiC JFETs for Active Short Circuit Events in Automotive Applications

Abstract:
A mixed 1.2 kV SiC JFET/MOSFET half bridge (HB) represents a novel approach in comparison to a uniform 1.2 kV SiC MOSFET HB. In automotive inverters in an event of a control failure, a safe state must be initiated, which is referred to as active short circuit (ASC). With the normally-on JFET the mixed JFET/MOSFET HB is capable of initiating this safe state at a gate supply voltage outage by itself. To estimate the robustness in case of ASC events usually surge current measurements are done. Therefore, this paper deals with the surge current robustness of SiC JFETs in comparison to state of the art SiC MOSFETs. Bidirectional, half-sinusoidal surge current tests under different pulse length and starting case temperatures are performed. The worst case conduction direction is determined, a failure analysis is done and a safe operating area is defined. Finally a evaluation of the surge current robustness relative to an automotive nominal inverter current is discussed.