Design and performance evaluation of overcurrent protection schemes for silicon carbide (SiC) power MOSFETs

Overcurrent protection of silicon carbide (SiC) MOSFETs remains a challenge due to lack of practical knowledge. This paper presents two overcurrent protection methods to improve the reliability and overall cost of the SiC MOSFET based converter. First, a solid state circuit breaker (SSCB) composed primarily by a Si IGBT and a commercial gate driver IC is connected in series with the DC bus to detect and clear overcurrent faults. Second, the desaturation technique using a sensing diode to detect the drain-source voltage under overcurrent faults is implemented as well. The design considerations and potential issues of the protection methods are described and analyzed in detail. A phase-leg configuration based step-down converter is built to evaluate the performance of the proposed protection schemes under various conditions, considering variation of fault type, decoupling capacitance, protection circuit parameters, etc. Finally, a comparison is made in terms of fault response time, temperature dependent characteristics, and applications to help designers select a proper protection method.