Calculation and Analysis of the Dynamic Turn-On Process of SiC MOSFET Based on a Piecewise Linearization Method

All silicon carbide (SiC) devices have the advantages of high switching speed and low loss. The current slew rate di/dt, current and voltage spikes, oscillation current/voltage, and turn-on loss (DOSs) are important electrical indicators for power devices during the switching process. However, there are few analytical expressions that balance accuracy and simplicity for quantitative analysis of DOSs due to nonlinear issues. This article derives the linearized analytical expressions for DOSs and analyzes the sensitivity of current and voltage spikes to different parameters during the turn-on process based on a piecewise linearization method. The analytical expressions provide an intuitive description of the relationship between DOSs and different parameters. For example, the phenomenon where voltage spikes of the high-side device do not monotonically decrease with the increase of driving resistance is discovered and explained. The sensitivity offers guidance for accurate and simplified linear processes in DOS calculations. The simplified equivalent output capacitance method and accurate dynamic current slew rate are proposed in the linearization process, as the current and voltage spikes have low sensitivity to output capacitance and high sensitivity to the current slew rate. The piecewise linearization method for calculating DOSs is verified by double pulse test (DPT) experiments and the relatively optimal driving resistance is designed and discussed.