An Improved Equivalent Circuit Model of SiC MOSFET and Its Switching Behavior Predicting Method

Wide-bandgap (WBG) power devices have better dynamic characteristics and higher working temperatures compared to traditional Si devices and are more suitable for high-frequency and high-voltage applications because of fast turn- on and turn- off speeds. The main obstacle for the use of WBG devices is the high-frequency oscillation (HF-Osc) in voltage and current during the switching process. In this article, a new method of predicting the SiC mosfet switching behavior (including HF-Osc and slow switching) is proposed. First, the models of nonlinear capacitances are improved and parasitic elements are taken into account for improving the RLC equivalent circuit of the mosfet switching transient. On this basis, the LC equivalent frequency is obtained. Then, a new method is proposed to obtain the SiC mosfet instantaneous frequency. The comparison between them in the time domain makes it possible to analyze the SiC mosfet switching behavior. The prediction method is verified using a CREE SiC mosfet via a double pulse test. Experimental and simulation results show that the prediction method is effective in describing the HF-Osc characteristics. The proposed method can be used to effectively improve the mosfet HF-Osc, which provides guidance for the application of SiC mosfet s.