An Integrated Voltage and Current Balancing Strategy of Series-Parallel Connected IGBTs

IGBTs are often connected in series and parallel to meet the requirements of high power applications. Unavoidable differences in circuit parasitic parameters and device parameters lead to voltage and current imbalance even to the destruction of devices. In this paper, an integrated voltage and current balancing strategy of IGBT is proposed, it can suppress turn-off overvoltage meanwhile balance the turn-on current of IGBT. IGBT voltage is clamped by RCD snubber circuit, and current of IGBT is controlled to follow a predefined I_c. Both current and voltage time delay are compensated by FPGA. The strategy integrates the digital global control into the analog control circuit, thus possess the flexibility of the digital circuit and the high reliability and the fast adjustment speed of the analog circuit. Research aims at seeking IGBT series and parallel modules possessing high reliability. Details about the strategy and its superiority are discussed. Experiment results with four series-parallel devices under double pulse test validate the effectiveness of the proposed method.