Research On PSpice Short-circuit Model And Short-circuit Protection Circuit Of SiC MOSFET

As the progress of power electronics technology,traditional silicon devices can no longer meet the performance requirements of some applications such as high temperature,high voltage and high power density,and wide bandgap semiconductor devices emerged as the times require.SiC MOSFET,as a typical representative of wide bandgap semiconductor devices,has the advantages of high temperature resistance,high voltage resistance,fast switching speed and low conduction loss,and has became a research hotspot in the power device market.Compared with Si IGBT of the same level,SiC MOSFET has smaller chip area and higher current density,and the short-circuit withstand time of SiC MOSFET is only 2-7?s,which is much shorter than that of Si IGBT.Therefore,the requirements of short-circuit protection circuit for SiC MOSFET is also higher.In order to study the short-circuit characteristic of SiC MOSFET,provide simulation model for the design of short-circuit protection circuit,and reduce the circuit design cycle,a simulation model of SiC MOSFET considering the short-circuit characteristic is established in this thesis,and on the basis of the short-circuit simulation model,a short-circuit protection circuit based on drain-source voltage integration is proposed.Firstly,the switching characteristic and short-circuit characteristic of SiC MOSFET are analyzed in detail,including the switching process and switching trajectory of SiC MOSFET,as well as the short-circuit behavior under different short-circuit fault conditions,and the influencing factors of the short-circuit characteristic of SiC MOSFET are studied through experiments.These provide a theoretical basis for the establishment of short-circuit simulation model of SiC MOSFET and the design of short-circuit protection circuit.Secondly,in order to determine the maximum delay time of the short-circuit protection action,the leakage current generated during short-circuit of SiC MOSFET is modeled,and then the short-circuit model of SiC MOSFET is established according to the short-circuit characteristic of SiC MOSFET.A short-circuit model of SiC MOSFET at room temperature is established first,and the accuracy of the model is verified by simulation.Then,the modeling method is extended to establish a short-circuit simulation model suitable for different operating temperature conditions.The simulation results of double pulse and short circuit at different temperatures are compared with the experimental results to verify the accuracy of the established short-circuit model.In addition,the short-circuit model is applied to the three-phase full bridge circuit in SIMetrix for simulation to verify the convergence and compatibility of the proposed short-circuit model.Finally,aiming at the short-circuit characteristic that the short-circuit withstand time of SiC MOSFET decreases with the increase of dc bus voltage,based on the short-circuit simulation model of SiC MOSFET,a short-circuit protection circuit based on drainsource voltage integration is proposed to meet the requirement that the higher the dc bus voltage,the faster the short-circuit protection action.Simulation and experimental verification are carried out under different dc bus voltage levels to verify the rapidity and effectiveness of the proposed short-circuit protection circuit.