IGBT Gate Control Methods to Reduce Electrical Power Losses of Hybrid Vehicles

Reducing the loss of the power control unit (PCU) in a hybrid vehicle (HV) is an important part of improving HV fuel efficiency. Furthermore the loss of power devices (insulated gate bipolar transistors (IGBTs) and diodes) used in the PCU must be reduced since this amounts to approximately 20% of the total electrical loss in an HV. One of the issues for reducing loss is the trade-off relationship with reducing voltage surge. To restrict voltage surge, it is necessary to slow down the switching speed of the IGBT. In contrast, the loss reduction requires the high speed switching. One widely known method to improve this trade-off relationship is to increase the gate voltage in two stages. However, accurate and high-speed operation of the IGBT gate control circuit is difficult to accomplish. This research clarifies a better condition of the two-stage control and designed a circuit that improves this trade-off relationship by increasing the speed of feedback control. Combining two-stage control with this new feedback method reduced loss by approximately 4%, helping to improve vehicle fuel efficiency. In addition to reducing loss, this development also improved the trade-off relationship between reducing loss and voltage surge. This is also regarded as a promising gate control method for potential next-generation devices such as reverse conducting IGBTs (RC-IGBTs) and silicon carbide metal-oxide-semiconductor field-effect transistors (SiC MOSFETs).