Research On Crosstalk Suppression And Short Circuit Protection Of SiC MOSFET Driver Circuit

Traditional silicon-based power devices have gradually replaced by wide-gap semiconductor devices SiC MOSFETs in the fields of solar photovoltaics,electric vehicles,and high-frequency power supplies due to the latter's advantages in fast switching speed,high operating frequency,low conduction loss,and high temperature resistance.As the switching speed is increased,the di/dt and d V/dt will gradually increase during the switching process,and there are a large number of parasitic parameters in the devices and circuits,which will cause serious electromagnetic interference to the system.The bridge-leg crosstalk is caused by the higher di/dt and d V/dt on the power side of the SiC MOSFET coupled to the driver loop through the Miller capacitance and source inductance.On the other hand,SiC MOSFET has the characteristics of small chip area,large short-circuit current,and concentrated heating positions,which results in short short-circuit withstand time and limited withstand energy.The defects of SiC MOSFET in the above two aspects have caused its application in the high-frequency field to be limited.Therefore,this paper will take the driver circuit of SiC MOSFET as the research object,focusing on its crosstalk suppression and short-circuit protection.The first part of this paper analyzes the generation mechanism of SiC MOSFET bridge-leg crosstalk.Taking the bridge circuit synchronous Buck converter as an example,the switching process of SiC MOSFET is analyzed,and the transient waveforms of voltage and current are calculated based on the parameters extracted from the device data sheet and experiments.Secondly,the mechanism of crosstalk is analyzed at different stages of turn-on and turn-off,taking into account the nonlinear characteristics of Miller capacitors,the overshoot and oscillation process of the drain-source voltage,the common source stray inductance,and the reverse recovery process of body diode.Establish a mathematical model of crosstalk,and has been verified by simulation.Finally,the trend of crosstalk is analyzed by changing various circuit parameters in the Buck converter.The second part of this paper designs the driver circuits for SiC MOSFET crosstalk suppression.Based on the analysis of the above-mentioned bridge-leg crosstalk mechanism,two crosstalk suppression circuits are proposed.One is a multi-level drive circuit based on RC voltage delay.The negative gate driver voltage is generated by the RCD voltage level converter.The driver signal consistent with the control terminal is delayed by the RC series circuit and then connected to the input terminal of auxiliary Nchannel MOSFET,and realizes the function of three-level driver voltage;the second is a passive Miller clamp suppression circuit,through the auxiliary circuit to change the impedance of the driver circuit during the switching transient of the SiC MOSFET,and releases the Miller current to the ground,so the crosstalk is effectively suppressed.Finally,simulation and experiment results verify the feasibility of the effect of crosstalk suppression.The third part of this paper designs the driver circuit for SiC MOSFET short-circuit protection.Taking hard-switching short-circuit faults and load short-circuiting faults as examples,the failure mechanism is analyzed from the perspective of semiconductor physics.Secondly,by changing the relevant parameters in the device and the circuit,the trend of the short-circuit waveform is analyzed.Finally,based on the saturation voltage detection method and the gate current detection method,a two-level soft turn-off shortcircuit protection circuit is proposed,which prevents damage to the device by slowing down the turn-off speed of the SiC MOSFET.The simulation results verify the reliability of the performance of short-circuit protection.In this paper,theoretical analysis,simulation and experimental verification are used to study the crosstalk problem and short-circuit protection problem in the SiC MOSFET driver circuit.Based on the above methods to study the generation mechanism of bridge leg crosstalk and the mechanism of short-circuit failure,and improve on the traditional driver circuit,it will exert the working efficiency of SiC MOSFET to a greater extent,which is of great significance to the development of applications of wide-bandgap power semiconductor devices.