Modeling And Analysis Of Switching Process Of Wide Band Gap Semiconductor Devices

The wide band gap semiconductor devices represented by SiC and GaN have the advantages of high breakdown voltage,high saturation drift speed,high working frequency and high working junction temperature.Compared with traditional Si devices,they can greatly improve the performance of power electronic system.In this dissertation,SiC MOSFET is taken as the research object to study the influence of parasitic parameters on the switching process in the circuit.The switching speed of SiC MOSFET is very fast.The influence of parasitic parameters on its switching characteristics is much more significant than the traditional Si devices.In practical engineering applications,it is very necessary to make pre optimization design through modeling.By investigating a large number of device models of power semiconductor,this dissertation selects a mathematical model of SiC MOSFET to analyze the switching characteristics.First,after in-depth analysis of the SiC MOSFET switch circuit,we get the voltage and current equations at all stages of the switching process.By solving the mathematical equation in time domain,we get the expression of voltage and current at each stage,and establish a first-order mathematical model.This model can simulate the switching process waveform to some extent,so that we can quickly understand the switching characteristics of a new device.Then,on the basis of the first order mathematical model,the parasitic capacitance and the transconductance of the device are nonlinear expression,and the high order differential equation is solved by the mathematical iteration method,and a more accurate high order mathematical model is established.This model can highly simulate the real switching process of analog devices.After the double verification of SPICE model simulation and double pulse test on high order mathematical model,the accuracy of the simulation of switch process is proved.Then,based on the high-order mathematical model,the influence of parasitic parameters including device parasitic capacitance on device switching process is analyzed,and the corresponding optimization design method in practical engineering application is pointed out.