Variable Amplitude Gate Voltage Synchronous Drive Technique for Improving Dynamic Current Balancing in Paralleled IGBTs

Abstract

The problem of current sharing imbalance in the parallel connection of IGBT multi-modules affects the wide-scale application of parallel IGBT. The current imbalance problem in the dynamic process is mainly caused by the difference in control loop parameters. In parallel IGBT applications, current sharing is a critical concern. Objective differences in IGBT module and driver circuit parameters, as well as incomplete symmetry in the power circuit, lead to inconsistent parasitic parameters, resulting in both static and dynamic current-sharing issues. Static current sharing refers to the uneven distribution of load current under static operating conditions, while dynamic current sharing refers to the imbalance in current distribution among parallel IGBT modules during turn-on and turn-off processes. This is mainly influenced by the synchronization of turn-on and turn-off timings and the consistency of collector current change rates during these processes. The difference in characteristic parameters of IGBT modules is an important factor leading to the difference in control loop parameters, which has a profound impact on the dynamic current-sharing characteristics of IGBT parallel applications. In the case where the device parameters cannot be changed, some drive compensation controls can compensate for the influence of device differences on dynamic current sharing. Accurate identification of the characteristic parameters of the IGBT module is the key to this method. This paper mainly studies a synchronous variable-amplitude drive scheme and studies the influence of parameters such as synthetic gate resistance, gate-emitter capacitance, and on-off gate threshold voltage on the dynamic current-sharing characteristics. The correlation characteristics of the characteristic parameters of the IGBT device body are studied, and the characteristic model of each parameter and the influencing variable is constructed. The parallel working model of PSpice devices is established, and the influence of different characteristic parameters on the current-sharing characteristics is evaluated, and its sensitivity is summarized through simulation analysis. Through the 1700 V/300 A IGBT parallel switch characteristic experiment, the current sharing effectiveness of the synchronous variable amplitude driving method is verified. Finally, the effects of different gate control voltages and different action times on the dynamic current-sharing characteristics are summarized.