Research On Short Circuit Characteristics And Protection Circuit Of SiC MOSFET

Silicon carbide(SiC)materials have the characteristics of high voltage resistance,fast switching speed,large critical breakdown electric field,high working frequency,high temperature resistance,etc.In the system with higher requirements for the efficiency and power density of power electronic equipment,the power devices made of SiC materials are the better choice.However,due to its small chip area,high current density and thin gate oxide,the short-circuit withstand ability of SiC is weaker than that of silicon.In order to make silicon carbide devices run more safely and reliably in power electronic equipment,it is of great significance to study its short-circuit characteristics and fault protection circuit.In this paper,the short-circuit characteristics and protection circuit of SiC MOSFET are studied.Firstly,the device characteristics of SiC MOSFET are analyzed,and the corresponding drive circuit design is carried out according to the device characteristics,and the parameters of each part of the drive circuit are determined.Considering the problems existing in practical application,the designed driving circuit has the functions of signal and electrical isolation,undervoltage protection,short pulse signal suppression,fault detection and short circuit protection.On this basis,a short-circuit test platform is built to analyze the influence of different gate driving resistance RG,gate source capacitance CGS and detection blind time Tblank on the short-circuit characteristics of SiC MOSFET.An improved soft turn-off protection strategy based on desaturation detection is proposed and the circuit design is completed.At last,the design of the fault protection circuit is verified by experiments.Compared with the traditional switching mode,the improved soft switching mode can effectively reduce the short-circuit switching voltage overshoot and slow down the rate of short-circuit current drop.In the process of switching off,the current change rate of the improved soft switching mode is 1.04A/ns,and the switching voltage peak is 658V.Compared with the traditional switching mode,the current change rate is reduced by 1.28A/ns,and the overvoltage peak is reduced by 128V.The results of this paper are helpful to understand the basic short circuit characteristics of SiC MOSFET and provide some guidance for the design of fault protection circuit of SiC MOSFET.