T22.3 - A Temperature-Tolerant, Ultrafast Fault Protection Scheme for GaN HEMTs with PCB-Integrated Rogowski Coil Current Sensors

A key challenge in the reliable design of power converters with GaN HEMTs is their low short circuit withstand time (SCWT) compared to SiC MOSFETs. Conventional desaturation protection schemes exhibit longer response times and are based on device output characteristics, whose variation with junction temperature shifts the fault-triggering instant. Fault protection schemes based on high-bandwidth current sensors can facilitate protection times much lower than the SCWT of the device. This work presents the design of a temperature-tolerant, ultrafast fault protection scheme for GaN HEMTs based on device current sensing with PCB-integrated Rogowski coils. The fault threshold level is set online, upon evaluating the mutual coupling between the coil and the DC power trace. Experimental results are presented at a DC bus voltage of 400 V in a half-bridge test setup. Reliable protection of the GaN HEMT subjected to hard switched fault is demonstrated for various device junction temperatures. Owing to an online scheme of high-bandwidth current sensing, the protection response time is reported to be under 40 ns across all operating conditions, independent of elevated junction temperatures.