Design consideration of MHz active clamp flyback converter with GaN devices for low power adapter application

With ever increasing demands of smaller size, lighter weight for all forms of consumer electronics, efficient power conversion with higher operating frequency has always being pursued rigorously. This paper demonstrates high frequency, high efficiency and high power density design of active clamp flyback converter for adapter application. Both the primary and secondary switches are gallium nitride (GaN) devices which can significantly reduce the device related conduction and switching loss. The design procedures, including the selection of active clamping capacitor, optimization of flyback transformer, and EMI filter design, are presented in detail. A 65W (19.5V/3.3A) prototype of active clamp flyback front end converter is developed to verify the feasibility of the system design. The prototype efficiency is 1~2% higher than the state of art product and the power density (exclude case) is more than 40W/in 3 .