Current Sharing Control For Parallel IGBT Based On Active Gate Drive

Insulated Gate Bipolar Transistor(IGBT),because of its mature structure and control technology,is currently the key devices of the power electronic equipment.Since 1980 s,the process and performance of IGBTs have been continuously improved,but the thermal characteristics and current capacity of the single-module IGBT are limited by the silicon material itself,which causes the performance of IGBTs cannot meet the needs of high-power devices.In terms of cost and scalability,the parallel connection of IGBT modules is one of the best solutions for the design and application of high-power power electronic devices.In the ideal case,the current of each IGBT should be equal.However,due to the asymmetry of the circuit,the difference in device parameters,and the delay of the drive signals,the parallel IGBTs have a current sharing problem,which is also potential safety hazards for long-term work of electronic equipment.Therefore,some methods are taken to improve the dynamic and static current sharing performance when IGBTs are connected in parallel,which is conducive to the further application of IGBT parallel technology.This article aims at the parallel use of IGBT modules,using drive control as the main method by combining the signal delay method and current slope control method to improve the dynamic current balance.The signal delay method uses an analog circuit to feed back the delay time of the parallel IGBT current change to the drive signal to compensate,and finally makes the parallel current rise/fall simultaneously.At the same time,the active gate voltage drive is used to improve the static current distribution of parallel IGBTs by the average current method.The dynamic switching characteristics and static output characteristics of the IGBT are analyzed in this paper.And it is clarified that the difference between the static and dynamic current waveforms of the asymmetric parallel branch.Then,it is also explored that the influence of the IGBT characteristics,driving signals and parasitic parameters on the parallel current distribution.Finally,the design of the drive circuit is determined.The active gate drive circuit is designed and manufactured.The drive circuit can output a variable voltage and control the slope of current flowing through the IGBT.Experiments are conducted through a double pulse test platform to verify the feasibility of the signal delay method and the current slope control method.The combination of the methods is helpful to reduce the imbalance of dynamic current.Through MATLAB software,the closed-loop current sharing control method is analyzed,and the feasibility of the closed-loop current sharing control strategy was clarified.Using FPGA(Field Programmable Gate Array)as the core controller,combines with the above design,the parallel current sharing control experiment of FF300R17KE4 module is conducted.The current balance of the two parallel modules is realized.And the effectiveness of the active drive circuit and current sharing control is further verified.