Study On The Parallel Characteristics And Driving Of Silicon Carbide MOSFET Devices

In recent years,with the rapid development of power electronic technology,traditional silicon materials are limited by their physical characteristics,and power electronic devices based on them can no longer meet the application requirements of high efficiency,high power density and some special occasions.The SiC power device has fast switching speed,low loss,and high switching frequency,which can better realize the high frequency,miniaturization and light weight of power electronic converters.In order to realize the application of SiC devices in high-power applications,it is necessary to use parallel SiC MOSFETs to increase their current capacity.However,due to the mismatch between the device’s own parameters and the parasitic parameters in the peripheral circuit,it is difficult to achieve a better current sharing effect between the parallel devices.Therefore,this article conducts an in-depth study on the current sharing problem of parallel SiC MOSFETs,and proposes a drive circuit design that can improve the current sharing effect.This article first establishes an equivalent circuit model of SiC MOSFET considering parasitic parameters,analyzes the switching process of the device in detail,and derives the mathematical model of the voltage and current of the device during the switching process.Based on the analysis of the switching characteristics of SiC devices,combined with the basic requirements of the parallel SiC MOSFET system for the drive circuit,the key analysis and research are carried out from the aspects of the structure of the drive circuit,the configuration of the drive resistance,the power of the drive power,and the peak current of the drive.The driving parameters of the three SiC MOSFET parallel system are designed.The designed drive circuit not only has enough drive capability,but also can ensure the synchronization of the gate drive signals of the parallel devices.The LTspice simulation circuit is built,and the factors that affect the current sharing effect of the SiC MOSFET parallel system and the mechanism of action are analyzed in detail through simulation.The emphasis is on the influence of the parasitic parameters in the system and the difference in device operating junction temperature on the current sharing effect.It mainly includes the stray inductance of the power circuit,the difference of parasitic parameters in the drive circuit,and the influence of the asymmetry of its own parameters caused by the asymmetry of the junction temperature of the device on the parallel system.Aiming at the problems of the existing parallel current sharing measures that severely sacrifice switching speed and complex structure,a parallel SiC MOSFET driving circuit with added source resistance is proposed.When the device has uneven current in the switching transient,the circuit uses the voltage drop on the source resistance of the drive loop to use its "negative feedback" effect on the device gate-source voltage,thereby improving the parallel device in the switching process.Asynchronous phenomenon,so as to realize the improvement of the transient current sharing effect of the device switching.By building an experimental platform of a600V/60 A parallel system of three SiC MOSFETs,it is shown that the driving scheme of adding source resistance has a good effect on improving the transient uneven current phenomenon of the switch.During the turn-on process,the current spike difference before the improvement is 13 A,and the current spike difference after the improvement is 5.5A.In the turn-off process,the peak value of the drain current oscillation is reduced,and the problem of asynchronous and uneven current of each parallel device in the turn-off transient state is better solved.This article mainly designs a parallel SiC MOSFET drive circuit and analyzes the factors that affect the current sharing effect of the device,and finally proposes a driving scheme with added source resistance,which can better solve the problem of uneven current in switching transients.This paper has 74 figures,8 tables,and 95 references.