Investigation for Influence of Parasitic Inductances of Damping Resistors on Suppressing SiC MOSFET Switching Oscillation

With excellent performance, SiC MOSFET provides tremendous advantages for the power converters applications. However, the interaction of its parasitic parameters with the power circuit's stray inductance may lead to severe oscillations, which can result in a range of hazards like voltage overshoot, current overshoot and high-frequency electromagnetic interference. Therefore, it is particularly important to suppress switching oscillation. It is generally considered that adding a snubber circuit is one of the best choices to solve this problem. Nevertheless, how to select an appropriate snubber circuit considering the parasitic inductance of snubber resistors corresponding to snubber loss has not been comprehensively researched. In this paper, the influence of snubber resistors parasitic inductances on the damping effect is investigated. First, the two-port equivalent networks of half-bridge circuit with different snubbers are used to obtain the exact characteristic equations that characterize the stability of the system, and then the snubber region parameters of the system are acquired by zero-pole assignment of the characteristic equations. The interpolation algorithm is applied to obtain the loss distribution of snubber region, and the corresponding damping resistors parasitic inductances is approximately estimated. And then the effects of damping resistors parasitic inductances on oscillation suppression are experimentally investigated. Based on the above results, practical pieces of advice on snubber circuit selection for practical application scenarios are made to converter designers.