Simultaneous Mitigation of Switching Overvoltage and Oscillation for SiC MOSFET via Gate Charge Injection Concept

Due to the inherent parasitic inductance and high switching speed, the SiC <sc>mosfet</sc> generally experience significant overvoltage and oscillation, reducing the voltage margin and causing substantial electromagnetic interference. To mitigate these challenges, a novel auxiliary circuit using the gate charge injection (GCI) concept is proposed in this article. The GCI circuit, assembled across the drain-gate of the SiC <sc>mosfet</sc>, injects charges into the gate during the overvoltage stage of the turn-<sc>off</sc> process, effectively reducing overvoltage and oscillation without affecting the turn-<sc>off</sc> speed. The mechanism of the proposed GCI circuit is meticulously analyzed interval by interval based on the cell structure of the SiC <sc>mosfet</sc>, and its parameters are designed and validated through the circuit simulation. Additionally, the proposed GCI circuit, comprising Si-RC and PiN diode die, is integrated into the SiC power module and assessed by the double pulse test and power cycling test. Experimental results show a 70% reduction in the transient overvoltage at 600 V/30 A and complete the oscillation elimination, with only a 3.4% increase in the switching loss. The GCI circuit does not affect the turn-<sc>on</sc> process, making it an effective and cost-competitive solution for suppressing the overvoltage and oscillation in the SiC power module.