An Accurate Analytical Model of SiC MOSFETs for Switching Speed and Switching Loss Calculation in High-Voltage Pulsed Power Supplies

Nanosecond output pulse and high efficiency are achieved in high-voltage pulsed power supplies (HVPPSs) by applying silicon carbide (SiC) metal-oxide-semiconductor field-effect transistors (mosfets), whose switching speed and switching loss are two vital characteristic parameters. However, the existing research on switching characteristics of SiC mosfets is mainly based on the double pulse test circuits with inductive loads, which is not suitable for assessing the devices in HVPPSs with resistive loads. Besides, some simplified analytical methods in HVPPSs lead to poor precision. To accurately predict the switching behavior of SiC mosfets in HVPPSs for guiding the design of gate driving circuits and power loops, this article proposes an accurate analytical model considering parasitic inductances, nonlinear parasitic capacitances, transfer characteristic, and output characteristics of SiC mosfets. High-precision fitting of transfer characteristic is realized by using the Gaussian function. Besides, the dynamic parasitic gate-drain capacitance is measured by experiment, and three-dimensional curve fitting is performed on the output characteristics to exactly represent on-resistance. Furthermore, switching speed and switching loss can be directly calculated according to the solved state variables. Finally, the analytical model is verified by experiment, and the effects of gate driving circuits and power loops on switching characteristics are researched in detail.