Research On A Zero Voltage Switching Inverter Based On SiC MOSFET

Silicon carbide,SiC,has gradually gained more attention in semiconductor applications because of its superior physical characteristics.And the SiC metal-oxide-semiconductor field-effect transistor(SiC MOSFET)has been applied in many power electronic fields.However,its fast switching speed leads to high dv/dt,and causes many problems such as electromagnetic interference(EMI)and overvoltage of electric machines.To address dv/dt in SiC MOSFET inverters,a resonant inverter is utilized so that zero voltage switching(ZVS)can be realized and dv/dt can be reduced,suppressing EMI problem.SiC MOSFET is different from Si IGBT.So its static and dynamic characterstics are analyzed and tested in order to make use of SiC MOSFET reliably.Static characteristics include output characteristics,transfer characteristics and on-state resistance.Dynamic characteristics include turn-on and turn-off transient characteristics and reverse recovery current of diodes.The dynamic characteristics of discrete SiC MSOFET deives is tested through double pulses test platform and some common problems in application are listed.The soft-swithcing topology is originated from Softswing which has been used in commercial electric vehicles(EV)by BRUSA of Europe.Since few literatures about Softswing can be found,this paper presents detailed analysis,including working process of turn-on and turn-off,different timing control methods and mathematical models of resonance.Different timing control methods and resonant parameters affecting soft-switching realziaiton are analyzed and compared.The timing control with boost current is determined and the resonant parameters have been selected carefully.A soft-switching platform based on SiC MOSFET single-phase half-bridge inverter has been designed,including power circuit and gate driver of SiC MOSFET.The power of the platform is 1kW and the switching frequency can be up to 200 kHz.The gate driver has reliable driving capacity and realizes fast protection within 700 ns.The experimental results under different timing control methods and different resonant parameters are shown,providing reference for designing SiC MOSFET resoant inverters.Compared to hard-swithcing inverter,the soft-switching inverter can reduce high-frequency components up to 100dBμV from the spectrum.