Analysis And Active Suppression Of Crosstalk For SiC Power Device Based Servo Drives

With the development of servo system towards high precision,high dynamic and high energy density,the performance of servo drives based on traditional silicon(SI)devices has been difficult to meet the requirements.SiC power device has the advantages of high withstand voltage,high switching speed and low loss.Its application in servo drives can significantly improve the power density and dynamic performance of servo driver.However,in the high switching speed SiC inverter,there is inevitably a serious problem of bridge arm crosstalk,which restricts the development of SiC based servo drives.At the same time,the traditional simplified bridge arm crosstalk modeling method also makes the understanding of crosstalk phenomenon not deep enough.Therefore,this paper studies the application and existing problems of the SiC MOSFET in servo drives.Firstly,the mechanism of crosstalk in SiC MOSFET inverter bridge arm is introduced,and the problems of the traditional simplified bridge arm crosstalk model are pointed out.In view of the shortcomings of the traditional bridge arm crosstalk model,the traditional crosstalk model is improved by taking into account the common source inductance,nonlinear junction capacitance,different packaging and other factors.The bridge arm crosstalk voltage is mathematically modeled and analyzed in stages according to the characteristics of crosstalk phenomenon,and the model is verified by both of the PSpice simulation and experiment.In addition,mathematical model calculation,PSpice simulation and experimental analysis are carried out for different voltage and current operating points,and the influence of different voltage and current operating points on bridge arm crosstalk voltage is given.Secondly,the mechanism of driving resistance affecting bridge arm crosstalk voltage is studied,and the mathematical relationship between driving resistance and bridge arm crosstalk voltage is deduced.Through the simulation and experiment of crosstalk voltage change under different driving resistance,the crosstalk voltage change of driving resistance in the range of 5Ω-30 Ω is obtained.The crosstalk suppression method of parallel external capacitance between gate and source is studied,and the influence of parallel external capacitance between gate and source on crosstalk voltage is obtained through experiments.The effect of grid source parallel zener diode on crosstalk suppression is analyzed,and its ability to suppress crosstalk negative pressure is verified by experiments.The influence of three common passive suppression methods on crosstalk voltage is summarized.Combined with the influence on SiC MOSFET performance and crosstalk voltage,a better passive parameter selection scheme is given.Moreover,two crosstalk suppression methods based on driving circuit are proposed,including crosstalk suppression based on multi-level SiC MOSFET and crosstalk suppression based on resonant auxiliary driving circuit.The working principles of the two driving circuits are analyzed.The effectiveness of the two circuits for crosstalk suppression is verified by simulation and experiment.Finally,the servo drive based on SiC MOSFET is designed,including power circuit and control circuit.This paper introduces the key points of hardware circuit design of SiC MOSFET based servo drive,and improves the design based on the first version of inverter for better performance.Finally,the experimental platform for the SiC MOSFET based servo drive is built to test the performance at 50 k Hz switching frequency,which proves higher dynamic performance owned by the proposed servo drive system.