Modeling SiC MOSFET and Switching Speed Limitation

Next-generation power electronic systems use SiC MOSFETs instead of IGBTs to improve power density by increasing switching frequency. However, the extremely high dv/dt and di/dt of SiC devices introduces new issues that were not of concern in Si power devices. This paper focuses on understanding the switching speed limitation of SiC devices and improve switching frequency. Firstly, a simple behavioral model of SiC MOSFETs is developed, with particular attention given to nonlinear capacitance characteristics and channel current characteristics. Secondly, based on the model, the factors that limit the influence of the switching speed of SiC devices are analyzed, including stray inductance, gate-source voltage (vgs) overshoot, and drain-source voltage (vds) overshoot. Finally, a method for designing the maximum switching speed of SiC MOSFET devices is proposed and verified by double pulse test (DPT).