Active Gate Drive to Increase the Power Capacity of Hard-Switched IGBTs

The effect of the gate drive on the power-processing capacity of a hard-switched insulated-gate bipolar transistor (IGBT) in a bridge leg is investigated in this article. The performance of two active gate drive (AGD) techniques [variable ramp (VR) and push-pull (PP)] is compared against a conventional two-level [fast gate drive (FGD)] gate drive method. The two proposed techniques reduce the voltage overshoot, which allows the dc-bus voltage to be increased closer to the IGBT voltage rating, improving the utilization of the device's blocking voltage. Consequently, the safe operating area of the IGBT is extended without exceeding the thermal limit of the device (limited by the maximum junction temperature). An experimental method, the first of its kind in the literature, is developed to determine whether using these AGDs can lead to an increase in the power that the IGBT can process. This article reveals that the PP-AGD technique can increase the IGBT power throughput by approximately 5%-8% across a range of switching frequencies. This better IGBT utilization allows a given device to process more power or may allow the designer to choose lower power rated devices potentially leading to higher converter power density.