Analysis And Optimization Of SiC MOSFET Transient Performance Based On Active Gate Drive Circuit

Compared with silicon?Si?devices,silicon carbide?SiC?devices have higher blocking voltage,lower on-resistance,higher switching frequency,and better thermal conductivity.Thence,the power electronic devices with SiC MOSFET can operate at higher power densities.However,the faster switching speed of SiC MOSFETs will deteriorate transient performance such as overshoot and oscillation during switching process and the crosstalk in phase-leg configuration.The active gate drive circuit can effectively optimize the transient performance of SiC MOSFET by improving the driving voltage,driving current and driving resistance,which has been widely studied by scholars at home and abroad.Therefore,this paper optimizes and analyzes the transient performance of SiC MOSFETs based on active gate drive circuitFirst,in order to optimize the transient performance of SiC MOSFETs,a detailed study of the switching characteristics of SiC MOSFETs has been conducted in this paper,including the basic structure and working mechanism of SiC MOSFETs.Based on the PSpice simulation software,the characteristics of the transient performance of SiC MOSFET compared to Si MOSFET and the effects of parasitic parameters on overshoot and oscillation in the circuit were explored.In order to reduce the damage caused by overshoot and oscillation of the switch waveform,the causes and suppression mechanisms of overshoot and oscillation during the switching process are analyzed,and a voltage injective active gate drive circuit is proposed,which can effectively suppress the overshoot and oscillation of voltage and current.Secondly,in term of the crosstalk of SiC MOSFETs in the phase-leg configuration,the formation mechanism of crosstalk and the influence of nonlinearity of gate drain capacitor(C_gd)on crosstalk peaks are analyzed.It is pointed out that the peak value of crosstalk calculated with the methods do not consider the nonlinearity of C_gd has a large deviation wih the experimental crosstalk peaks.In order to predict the peak value of crosstalk accurately,this paper proposes an algorithm considering the nonlinearity of C_gd,which was verified in Kelvin-packaged SiC MOSFET.The experimental results that he proposed algorithm has higher accuracy than the conventional method without considering the nonlinearity of C_gd.Finally,this paper summarizes the crosstalk characteristics under zero-voltage and negative-voltage gate drive circuit,and summarizes the ideal driving waveform that can effectively suppress crosstalk in the bridge circuit.Based on the formation mechanism and ideal driving waveform,a multilevel active gate drive circuit for crosstalk suppression is proposed.The control method and hardware design of the multilevel active gate drive circuit are also described in detail,and is verified in half bridge circuit by experiments.The experimental results show that the positive and negative spikes of crosstalk are in the within safe voltage range.