Active Gate Driver For SiC MOSFET Based On Switching Transient Feedback

Compared with the traditional Si based power devices,the third generation of semiconductor devices Si C MOSFET has the advantages of wide band gap,high breakdown and blocking voltage,good thermal conductivity,fast switching speed and has a huge advantage that traditional power devices can not match in electric vehicles,aerospace,new energy and other fields.However,with the increase of the switching speed of Si C MOSFET,the switching characteristics of the device are very sensitive to the internal parasitic parameters and junction capacitance,resulting in the high speed switching process that is easy to produce serious current,voltage overshoot and high frequency oscillation,at the same time,aggravate the influence of electromagnetic interference(EMI),increase the device loss and shorten the operating life.The reliability of Si C-based devices is seriously affected.Therefore,in order to improve the reliability of Si C MOSFET driving operation and reduce the electrical stress borne by the device during operation,the switching characteristics of Si C MOSFET are firstly analyzed in depth in this pa per,and the mechanism of current and voltage overshot and switching oscillation in the process of Si C MOSFET switching is revealed.The mathematical relation between gate current and current voltage overshoot is also established.Then,based on LTspice si mulation platform,the CAS300M12BM2 Si C MOSFET half-bridge module simulation model is built,and the influence of each driving parameter on the switching characteristics of the device is studied and analyzed,which provide theoretical guidance for the subsequent design of active drive circuit.In order to solve the problem of switching current and voltage overshoot,there are many problems in the traditional driving circuit and active gate driving circuit of Si C MOSFET,such as complex driving circuit desig n,low reliability,unsatisfactory switching current and voltage overshoot suppression effect,and unbalanced switching loss increment,,a novel active drive circuit with variable gate current is proposed.In the Si C MOSFET switching process,the gate cur rent is actively regulated during the drain current and drain-source voltage rise phase by directly detecting and feedback the transient drain current change rate d Id/dt,drain-source voltage transformation rate d Vds/dt,and gate voltage Vgs.The overshoot and oscillation of the current and voltage are suppressed.According to the working principle of active drive circuit,the hardware circuit is designed,the corresponding device selection is determined,and the hardware circuit experiment platform is buil t.Based on the designed active drive hardware circuit,a double-pulse test platform is built.The feasibility of the active drive circuit is verified by several experimental conditions,including different gate resistance,different bus voltage and differ ent load circuit conditions.The experimental results are compared and analyzed with the traditional drive circuit.The results have shown that the active drive circuit method can effectively reduce switching current and voltage overshoot,suppress oscilla tion and electromagnetic interference,and improve the operation reliability of Si C MOSFET converter.