Active Temperature Balance Control of Parallel-Connected SiC Power MOSFETs

SiC MOSFETs are rapidly replacing Si-based devices in high-power applications due to their superior electrical and thermal characteristics. Nevertheless, due to fabrication constraints, commercial SiC dies have lower current ratings compared to their silicon counterparts. As a result, multiple SiC MOSFETs must be connected in parallel for high-current applications. This inevitably results in current and thermal imbalances among the devices due to asymmetric layouts and parameter variations. To address this issue, this work proposes an active thermal balance control strategy that monitors the case temperatures of parallel-connected SiC MOSFETs and individually adjusts the duty cycle of each switch in a closed-loop manner to ensure the thermal balance among all devices. The proposed approach allows full exploitation of each device without the need to introduce current derating, typically required in parallel-operating switching converters. Experimental results are presented, validating the proposed technique.