Study On The Effect Of High Speed Switching Behavior About GaN Based Circuit And Its Suppression Methods

With the continuous development of Si power devices,the device performance is gradually approaching the theoretical limit,which also limits the further improvement of the performance of power electronic devices.The third generation semiconductor materials have attracted extensive attention in industry and academia because of their advantages such as high band gap,high electron mobility and fast saturation drift speed.The smaller gate source charge of GaN power devices is more suitable for high-frequency working conditions,making it one of the important technical means to realize high-frequency,high efficiency and high power density,However,the high voltage change rate dv/dt and high current change rate di/dt produced in the process of high-speed switching will threaten the safe and reliable application of GaN power devices.This paper will study the related problems of high-speed switching behavior of GaN power devices.Firstly,this paper compares and analyzes the characteristic differences of GaN power devices with different structures,and analyzes the influence of parasitic parameters of test equipment on the test results of double pulse circuit based on the equivalent circuit model of test equipment.For the voltage test equipment,this paper analyzes the influence of parasitic inductance of grounding spring and ground clamp on the voltage waveform in the switching process;For the current test equipment,this paper analyzes the parasitic parameter differences between the sampling resistance and the coaxial shunt,which lays the foundation for the standardized use of the test circuit and the accurate test of the device performance,and paves the way for the work content of the following paper.This paper solves the related problems in the high-speed switching process of GaN power devices from the perspective of driving circuit.Therefore,the electrical requirements of driving chip and the selection of driving resistance are analyzed in detail.Secondly,the common mode current caused by high voltage change rate dv/dt acting on the isolation capacitor and the overvoltage of bootstrap capacitor caused by high current change rate di/dt acting on the parasitic inductance are studied in this paper.For the problem of common mode current in driving circuit,the generation mechanism of common mode current is analyzed based on the conduction path model.At the same time,the suppression mechanism of common mode choke and cascade auxiliary power supply is analyzed and verified by experiments.For the over-voltage problem of bootstrap capacitor,this paper analyzes the influence of parasitic inductance in the charging stage of bootstrap capacitor,and suppresses the over-voltage of bootstrap capacitor by means of parallel Zener diode and series charging resistance of bootstrap path,so as to ensure the normal working state of GaN power device.Finally,this paper studies the bridge crosstalk caused by the joint action of high voltage change rate dv/dt and high current change rate di/dt,and explains the formation mechanism of bridge crosstalk through the stage analysis of switching process.Negative voltage turn-off driving mode is a common method for bridge crosstalk suppression.Based on the mathematical analysis model,this paper reveals the internal relationship between negative voltage levels and device loss.At the same time,a new Similar to the half-bridge negative voltage gate driver is proposed,and its working principle and parameter design method are described in detail.Finally,the bridge crosstalk suppression effect of the driving circuit is verified by experiments.