The wide-scale adoption and accelerated growth of electric vehicle (EV) use and increasing demand for faster charging necessitate the research and development of power electronic converters to achieve high-power, compact, and reliable EV charging solutions. Although the fast charging concept is often associated with off-board DC chargers, the importance of on-board AC fast charging is undeniable with the increasing battery capacities. This article comprehensively reviews gallium nitride (GaN) semiconductor-based bidirectional on-board charger (OBC) topologies used in both 400 V and 800 V EV applications. Moreover, comparative evaluations of GaN-based bi-directional OBC topologies regarding power conversion losses (conduction loss and soft switching capabilities), power density, implementation considerations, power quality, electromagnetic interference, and reliability aspects have been presented. The status of commercially available GaN power modules, advancements in GaN technology, applicable industry standards, and application requirements for OBCs have been also included in this study. Finally, in light of forthcoming advancements in GaN power transistor technology, this study highlights potential areas of research related to the reviewed topologies. Such research can aid researchers and designers in improving the performance and user experience of electric vehicles, ultimately supporting the widespread adoption of EVs.

Gallium nitride (GaN) power semiconductors are being explored as promising alternatives for the next generation of high-power traction inverters, suitable for both high- and low-voltage applications. In such scenarios, the peak current can reach several hundred amps. Hence, using multiple GaN HEMT chips or dies in parallel is definitely a design approach to extend power capacity and minimize power losses. However, the parallelization and packaging structure of GaN devices present numerous challenges. Achieving balanced dynamic and static current sharing between paralleled devices, as well as ensuring robust gate driving signals, is indispensable for reliable operation during high dV/dt and di/dt transients, particularly with switching noise-sensitive gate-source threshold voltages. Additionally, thermal dissipation and mechanical stress must fulfill industrial requirements. This paper introduces a compact 100 V/360 A GaN power module specifically designed for packaging on insulated metal substrates (IMS) or direct-bonded copper (DBC). The proposed packaging approach offers superior electrical performance, excellent thermal dissipation, minimal mechanical stress, and a cost-effective solution. Finally, the advantages of the proposed power module design are validated through various experimental setups, including a 48 V/328 A double pulse test, a 48 V/24 V 3 kW buck converter implementation, and a 48 V/5 kW three-phase inverter demonstration.