Ultrafast Protection of SiC MOSFETs With PCB Coil Based Current Sensors

<div>Silicon Carbide (SiC) MOSFETs offer significant advantages in terms of improved efficiency and reduced size of power electronic converters. However, they possess lesser short circuit withstand time (SCWT) than silicon devices. Consequently, protection circuits for SiC MOSFETs should have a sub-microsecond response time for ensuring device safety. An ultrafast short-circuit protection scheme for TO 247 packaged SiC MOSFETs is presented in this article. The protection scheme utilizes PCB coils to sense the rate of change of current through SiC MOSFETs in a half-bridge circuit. The PCB coil output is integrated to produce a voltage that is proportional to the MOSFET current. The protection circuit compares this voltage with a fault current reference and protects the device when a fault is detected. The design of the protection circuit along with the PCB coil embedded half-bridge circuit board is discussed. Experimental results for a SiC MOSFET subjected to a hard switched fault (HSF) and a fault under load (FUL) are presented, which validates the ultrafast response capability of the protection scheme.</div>