Over-Voltage and Oscillation Suppression Circuit with Switching Losses Optimization and Clamping Energy Feedback for SiC MOSFET

The normal snubber circuit decoupling the power loop inductance is a cost-effective method to solve the severe turn-off oscillation problem of SiC MOSFETs. However, this will also significantly increase the turn-on loss and decrease the performance of SiC MOSFET. This paper proposes a SiC MOSFET turn-off oscillation reduction circuit and the proposed circuit shows good switching losses reduction characteristics. By using the clamping capacitors, the oscillation is greatly reduced and the oscillation energy is stored in these capacitors. At the same time, the clamping capacitors will only work until the drain-source voltage is larger than the DC-bus voltage, and this feature is the benefit to the switching losses reduction during the turn-on transient. Once the SiC MOSFET circuit turned into the static state, the over-voltage and oscillation energy storage in the clamping capacitors can be feedback which helps further increase the efficiency of the whole system. Experimental and comparison studies were made to verify the effectiveness of the proposed turn-off oscillation reduction circuit. Experimental and comparison results show that turn-off oscillation reduction circuit has excellent turn-off over-voltage and oscillation suppression performance, and can greatly reduce total switching losses.