Research On Switching Characteristics Optimization And Multi-level Driver For High-Power SiC MOSFET

Compared with IGBT,SiC MOSFET can achieve faster switching speed,but at the same time,it brings problems such as switching voltage overshoot spike,crosstalk and high frequency oscillation.Compared with the Conventional SiC MOSFET Gate Driver,which balances switching loss and switching voltage overshoot oscillation by adjusting driving resistance,Active Gate Driver,which can dynamically improve the switching characteristics of SiC MOSFET,is of great research value.In this paper,multi-level active gate drive circuit for high power SiC MOSFET module is studied to improve its switching characteristics.Firstly,the structure,static and dynamic characteristics of SiC MOSFET are studied.The relationship between the driving resistance and the driving voltage of key switch transient characteristics is derived.Based on the SiC MOSFET double pulse experiment,the influence of different external driving resistance and driving voltage on the switching characteristics of SiC MOSFET was studied.The effect of load current on switching characteristics of SiC MOSFET is studied.The results show that the load current value can significantly affect the switching characteristics of SiC MOSFET.Secondly,the linear loss model is used to analyze the mechanism of multi-level drive,and an overall structure of multi-level active gate drive circuit for half-bridge module is proposed.In order to improve the drain-source voltage stress margin(decrease the turn-off voltage peak),the inhibition effect of the action time and action level on the turn-off voltage peak was studied.In order to reduce turn-off loss,two driving strategies which can reduce turn-off loss without changing the voltage stress margin are proposed,and the optimization methods are compared with the traditional driving strategies.The improvement effect of switching intermediate level on switching characteristics is studied.Based on the mechanism of crosstalk problem and the idea of driving function reuse,a crosstalk suppression strategy was proposed to improve the crosstalk margin of SiC MOSFET module without adding additional devices.The effectiveness of the proposed driving strategy in improving switching characteristics and crosstalk suppression was verified by double-pulse test.Finally,in order to make the designed multi-level gate driver adapt to different driving resistance,different load current,different type of SiC MOSFET power module and different temperature,an adaptive multi-level drive circuit is designed,a detection conditioning circuit is added and the control strategy is improved.Experiments show that the designed adaptive multi-level active gate driver can optimize the switching characteristics in various working conditions reliably.