Accurate Evaluation of Commutations of 650 V GaN Power Switches Assisted by Electromagnetic Simulations in a 7 kW Dual Active Bridge Converter for Automotive Battery Charging Applications

The exploitation of high-voltage GaN power switches enables the development of power converters with superior characteristics with respect to components developed with heritage silicon-based technologies. One of the key advantages of GaN switches is their very fast commutation capability due to reduced parasitic capacitance and inductance with respect to silicon devices. The capability of an accurate evaluation of the switch commutations in the design phase is of crucial importance to maximize performance and avoid reliability or electromagnetic compatibility issues in the final converter. In this paper, an accurate evaluation of high-voltage GaN HEMT commutations is performed, exploiting detailed non-linear dynamic models of transistors and electromagnetic simulations of a PCB. A deep insight into the commutation waveforms in the intrinsic device (i.e., conductive drain current and intrinsic node voltages) is proposed to evaluate and explain the mechanisms of almost lossless turn-off and turn-on commutations in a 7 kW DAB converter. The influence on the performance of the PCB parasitics and the driver characteristics are accurately reproduced by simulations, suggesting important guidelines for the optimal design of power converters fully exploiting GaN HEMT’s potential. This detailed simulation/analysis approach for transistor commutation is typically adopted in Radio Frequency amplifier design but also becomes very valuable in power converter design when the very fast commutations of a GaN HEMT at a high switching frequency cannot be fully described and taken under control with conventional approaches used in power electronics design. The simulation results are confirmed by experimental data.