A 2-kW, 95% Efficiency Inductive Power Transfer System Using Gallium Nitride Gate Injection Transistors

Abstract

This paper presents an inductive power transfer (IPT) system targeting at electric vehicles (EVs) and hybrid EVs. IPT systems provide significant benefits over the conventional plug-in chargers. However, in order for IPT to be adopted for EV charging, efficiency is a key figure of merit, which needs to be achieved. This paper presents a high-frequency inverter using gallium nitride (GaN) power transistors that have the benefit of low on-resistance and gate charge to reduce the switching and conduction loss. The switching characteristics of the GaN GIT are studied, and the inverter is designed to ensure low switching losses while keeping overshoot and slew rates under control. An efficiency centric mode of operation is proposed to improve the efficiency of the system while ensuring sufficient power transfer. The system efficiency peaks at 95% at 100-kHz operation and 92% at 250-kHz operation for a coil gap of 80 mm at 2-kW output power. At a coil gap of 150 mm, the system obtains above 90% efficiency at 1.3 kW. The IPT system is compared with a similar system using SiC power transistors and outperforms it by 1% at 2 kW.