Switching Time Analysis And Driving Technology Of High-Power SiC MOSFET

With the rapid development of power electronics,the application of high voltage and high current put forwards higher requirements on switching characteristics of power devices.As a new type of wide-band semiconductor device,silicon carbide devices have advantages of fast switching speeds and low switching losses compared to conventional silicon devices.Due to the increase of switching speed,the high voltage and current conversion rates during the switching process act with parasitic parameters in the circuit.Voltage and current overshoots and oscillations are generated.This will affect the safe working margin of the devices and cause serious electromagnetic interference to the system.Therefore,the driver and protection of high-power SiC MOSFET modules are currently a popular research topic domesticly and internationally.Based on the research on conventional gate driver and protection circuit,the mechanism of high di/dt during the switching process of high-power SiC MOSFET module is analyzed in this paper.A method to change the switching process by switching into bypass current sources is proposed.The main research contents of this paper are as follows:1.The switching process of SiC MOSFET power module is modeled.For a typical bridge circuit,the distribution of parasitic parameters is systematically analyzed.Each stage of SiC MOSFET switching process is modeled and calculated.Furtherly,the formations of voltage and current overshoots,oscillations,and losses during the switching process are given.This provides a theoretical basis for the driver design.2.The driver and protection circuit of high-power SiC MOSFET is designed.According to requirements of high-power SiC MOSFET driver,the conventional gate driver is optimized to achieve reliable driving of SiC MOSFET devices.Furthermore,for the short-circuit,crosstalk,gate overvoltage and other faults that may occur to SiC MOSFET devices,corresponding protection circuits are designed.3.An active gate driver with bypass current sources switching into the circuit is proposed.By switching bypass current sources of into the gate driver at specific moments during the turnon and turn-off processes,current rising and falling speeds can be slow down.Thereby voltage and current overshoots can be reduced during the switching process.Based on the steady-state voltage and current feedbacks of the circuit,a closed-loop control strategy is further designed.The proposed driver design in this paper is applied to the 1200 V 300A SiC MOSFET halfbridge module.The validity and superiority of the designed driver circuit are verified by a doublepulse test circuit and a buck circuit.