As the new energy vehicle sector progresses, there is a growing need for OBC systems in vehicle design to be more compact, lightweight, and efficient in energy conversion. This trend is challenging the physical performance limits of traditional silicon-based power devices. Gallium Nitride (GaN) has emerged as the technology of choice for on-board auxiliary power systems, thanks to its benefits of high-frequency operation, minimal losses, and cost-efficiency. GaN devices boost AC/DC conversion efficiency, minimize energy losses during the charging process, and accommodate higher power density. This results in a substantial reduction in the size and weight of on-board chargers. Their low energy losses and superior thermal efficiency also bolster system reliability. Furthermore, GaN can utilize silicon-based manufacturing processes and 12-inch wafer fabrication facilities, rendering its costs more competitive. Leading global new energy vehicle manufacturers, including Tesla and BYD, have already embraced GaN technology. They are integrating it into on-board charging systems and voltage converters to enhance charging efficiency and drive technological integration.