Research On SiC MOSFET Parallel Current Sharing And Crosstalk Suppression Driver Circuit

The third-generation semiconductor device SiC MOSFET relies on benefits such as rapid switching speed,high working frequency,high temperature resistance,and low conduction loss,progressively displacing conventional silicon power devices in new energy vehicles,photovoltaic inverters,motor drives,and other applications.Due to the increase in switching speed,devices are more sensitive to parasitic parameters in circuits,which poses a challenge to the safety and stability of SiC MOSFETs in parallel applications.When SiC MOSFETs are used in bridge circuits,the crosstalk problem caused by high-speed switching operations seriously affects the reliability of the system.In order to ensure stable operation of SiC MOSFETs in circuit systems,this thesis mainly focuses on parallel current sharing and crosstalk suppression issues.The first part firstly analyses the electrical characteristics and switching process of SiC MOSFET,introduces the physical structure and operating principle of SiC MOSFET,and compares the differences in transfer characteristics,output characteristics and considerations for application with Si IGBTs according to the datasheet.Next,a double-pulse test circuit is constructed to theoretically analyse the switching process of SiC MOSFET.Finally,the effects of parasitic parameters on the switching characteristics of SiC MOSFETs are investigated,starting from the switching time,voltage and current change rate,voltage and current stress,and switching losses,and the effects of parasitic capacitance,parasitic inductance,and driving resistance on the switching characteristics of SiC MOSFETs are simulated and verified.In the second part,the current sharing problem of SiC MOSFETs in parallel applications is studied.Firstly,the causes of current imbalance are analyzed from both dynamic and steady-state processes.The key influencing factors of current imbalance are theoretically derived and simulated,and the simulation results are consistent with the theoretical analysis.Secondly,a current sharing scheme of impedance compensation combined with gate source common mode choke is adopted,and its current sharing principle is analyzed using an equivalent circuit model.Finally,a simulation model of SiC MOSFET dual transistor parallel circuit was built,and the feasibility of this current sharing scheme was verified by comparing it with no current sharing measures and impedance compensation schemes.The third part investigates the crosstalk suppression driving circuit for SiC MOSFETs.Firstly,the crosstalk problem generation principle is analysed and a crosstalk voltage model is established.Secondly,through the study of typical crosstalk suppression drive circuits,two types of crosstalk suppression circuits are proposed.One is a new drive circuit based on a variable gate source voltage strategy,which is verified to be effective in reducing the crosstalk voltage while reducing the device switching losses through simulation comparisons with capacitor-based drive circuits and RCD-based drive circuits.The second is a new Miller clamp drive circuit based on the gate loop impedance control strategy,which uses triodes and passive devices to change the impedance of the drive loop and effectively suppress crosstalk.Finally,the hardware design of the drive circuit and the experimental platform are built,and the experimental results verify the crosstalk suppression capability of the drive circuit.Through theoretical analysis,simulation,and experimental verification,this thesis studies the parallel current sharing problem and crosstalk suppression problem in SiC MOSFET applications,which is of great significance for maximizing the operational efficiency of SiC MOSFETs in practical applications.