Design Optimization of RC Snubber Circuit for A SiC Power Module

Silicon carbide (SiC) power modules have a wide range of applications due to their excellent electrical and thermal properties, such as high switching speed, low on-resistance, and high operating temperature. However, device reliability may suffer from overvoltage and current/voltage oscillation mainly caused by circuit parasitic inductance and capacitance. This phenomenon becomes more profound, especially at high-switching speed with high dv/dt and di/dt. It is therefore necessary to suppress the turn-off overvoltage and increase the damping ratio. This paper proposes a methodology to select the optimal resistance and capacitance values for the RC snubber circuit for SiC power modules. The methodology is verified through LTspice simulation. Based on the theoretical calculation and spice simulation, the optimal RC snubber capacitance and resistance are identified. In addition, results indicate that RC snubber capacitance can only suppress ringing, but not suppress surge voltage. The snubber resistance can mitigate the overvoltage.