Adaptive digital gate control for series connected IGBTs

Abstract

In high power application, series connection of insulated gate bipolar transistors (IGBTs) can increase their voltage handling capability. As to the serial IGBTs, the key issue is to ensure both dynamic and static voltage sharing among serial IGBTs. For the differences of IGBT's characteristics, even the same gate driver could not ensure voltage balance between serial IGBTs. In order to achieve the voltage sharing, the adaptive digital gate control (ADGC) is proposed in this paper. In the proposed adaptive digital gate control, the turn-on di/dt and turn-off dv/dt are digitally sampled and fed back to the control unit, FPGA. The FPGA chooses the suitable gate drive parameters to make the serial IGBTs' switching processes synchronized. The FPGA compares switching speeds of serial IGBTs and determines suitable drive parameters for each serial IGBT. Thus, the serial IGBTs' switching processes can be synchronized and the voltage sharing is achieved. Essentially, it is an optimization of IGBT's switching process, increasing its drive reliability. Experimental results validate the feasibility of the proposed adaptive digital gate control method.