Research And Circuit Design Of Negative Pressure Integrated High-reliability SiC MOSFET Drive Strategy

With the continuous development of the power electronics industry,modern power electronic equipment has been extended to higher voltage,higher frequency and more efficient industrial applications.The characteristics of the wide-bandgap semiconductor material make SiC MOSFET stand out in high-voltage,high-frequency,high-temperature,high-efficiency,high power consumption electric and hybrid vehicles and solar inverters.Since SiC MOSFETs are different from Si MOSFETs in terms of gate charge,onresistance,and I-V curve characteristics,the development and design of dedicated SiC MOSFET driver chips is necessary.According to the device characteristics and switching characteristics of SiC MOSFET,some basic design requirements of SiC MOSFET driver chip are determined: negative voltage turn-off,high-voltage drive,high-current drive,power supply voltage undervoltage unlock judgment,overcurrent protection,etc.Therefore,in accordance with the above driver design requirements,this article has made a specific design for the high-reliability drive strategy and the high-reliability negative voltage power rail of the SiC MOSFET drive chip.A high-current drive strategy with dynamic Miller clamp is proposed,and a negative voltage charge pump is integrated to provide a stable negative voltage.A floating power rail is designed to provide a 5V differential voltage power rail for thin gate oxide devices,and a dynamically controlled Miller clamp transistor is added to ensure that the gate voltage of SiC MOSFET is not affected by crosstalk.In order to provide a stable negative voltage,based on the voltage sampling feedback model,a closed-loop linear negative voltage charge pump circuit is designed in this paper.A simple charge pump structure is used to realize the conversion from positive voltage to negative voltage.The linear closed-loop collects information from the output of the charge pump and feeds it back to the input of the charge pump through the loop to adjust the charge pump output,and sets the loop reference voltage on the basis of the external input setting voltage VEESET,and achieve the purpose of controlling the output of the charge pump by VEESET.Building the loop in Simplis,setting a reasonable pole-zero and bandwidth,verified the stability of the closed-loop linear charge pump.When VEESET is greater than 10 V,VEE is a stable output around-8V.The driver stage of the charge pump switching system is similar to the SiC MOSFET driver stage,and dynamic Miller clamps are set on both the high and low sides of the driver to suppress crosstalk according to the demand.The integrated driver chip is also equipped with reference,linear regulator,current bias,desaturation over-current detection,undervoltage lockout,and over-temperature protection to ensure the stability,integrity and reliability of the driver chip.Based on0.18?m BCD high-voltage process,500 k Hz system switching frequency,1200 V powerlevel DC voltage,20 V drive voltage,the circuit design and simulation verification of the negative voltage integrated high-reliability SiC MOSFET drive strategy are completed.When the 1n F load capacitance simulates the SiC MOSFET input capacitance,a driving edge as low as 7ns is achieved,a driving delay of 17 ns,a driving current of 4A and the anti-crosstalk ability is above 150V/ns are realized,which meets the drive design requirements for SiC MOSFETs.The negative voltage integrated charge pump realizes the ideal setting relationship between the input setting voltage VEESET and the output voltage VEE,and provides a stable and reliable output voltage of-8V when VEESET is greater than 10V.