Research of Voltage-Balancing Methods of Series-Connected IGBTs

Abstract

Voltage-balancing method is the key to the application of series-connected Insulated-Gate Bipolar Transistor(IGBT). In this paper the voltage-balancing process is divided into 4 stages: dynamic turning-on process, dynamic turning-off process, the tail current state and steady state, whose voltage-balancing methods are then proposed respectively: gate compensation capacitor network for dynamic process; resistance capacitance(RC) voltage-balancing circuit designed for tail current state with the capacitance given by a formula; and parallel-connected voltage-balancing resistance for the steady state. Based on the work above, power module of two series-connected IGBTs is designed and tested under high voltage and high current condition. The result shows that under the series total voltage 2kV (1.85kV maximum peak voltage for each IGBT) and 2kA current, the power module balanced the voltage of the whole period of an turning on and off process, and both of the voltage-unbalance-rate of dynamic and steady state are less than 5%.