GaN HEMTs are superior for cryogenically cooled solid-state circuit breakers (SSCBs) in future aircraft applications owing to their low on-resistance and high saturation current. However, during the high current turn-off, a potential ringing issue could happen to damage the device. In this digest, GaN HEMTs are tested to fail at ~480 A turn-off current in a SSCB. The reason for the high current turn-off failure is analyzed, which could be the instability of paralleled switching cells in one GaN bare die. A solution is proposed to use the RC snubber to reduce the overlap of vds and id during the turn-off to avoid the unstable region where the hard-switching trajectory goes through. The experiment is conducted to verify the effectiveness of the proposed solution. With the reduced overlap between vds and id, the GaN HEMT successfully turns off the 550 A objective current.
