Study On Current Sharing In Parallel Of SiC MOSFET Devices

As one of the representative devices of wide band gap semiconductor,SiC MOSFET has the advantages of low on loss,fast switching speed and high temperature tolerance.It can reduce converter loss and improve power density when applied to power electronic converter.In order to meet the application requirements of SiC MOSFET in medium and high power applications,it is necessary to parallel SiC MOSFET to improve the current capability.Therefore,this paper focuses on the parallel current sharing of SiC MOSFET.First of all,starting from the switching characteristics of SiC MOSFET,the theoretical analysis of every stage of the non ideal switching process of SiC MOSFET considering the parasitic inductance is carried out in detail.The theoretical analysis results of the influence of threshold voltage,on resistance and parasitic inductance difference on the current sharing characteristics and switching energy of parallel SiC devices are given.The theoretical analysis is verified by the two transistor parallel double pulse circuit model of SiC MOSFET built by Pspice simulation software.Secondly,in order to investigate the steady-state junction temperature difference of SiC MOSFET in parallel operation,the variable temperature characteristics of the device parameters of SiC MOSFET and its influence on the current sharing in parallel are analyzed.In this paper,the influence of threshold voltage,on resistance and the difference of main parasitic parameters on the steady-state junction temperature difference of parallel silicon MOSFET is studied.Then,aiming at the current imbalance of parallel devices caused by the difference of threshold voltage,the influence of the parasitic inductance on the current imbalance is analyzed in detail.On this basis,the suppression effect of auxiliary resistance on the current sharing problem is studied.In addition,the influence of driving resistance on the switching characteristics of SiC MOSFET is also studied in this chapter.It is proposed that the driving resistance regulation can effectively suppress the dynamic current imbalance in parallel,which is verified by experiments.Finally,the influence of the parasitic inductance difference on the current sharing characteristics and switching energy of the parallel devices is verified by experiments.The design points of the drive circuit and power circuit of the SiC MOSFET are given.Through Q3 D simulation,the difference of parasitic inductance between the conventional layout and the elimination of inductance is compared,and then the multi transistor parallel experiment circuit of the SiC MOSFET is built to verify.