A high-efficiency active clamped flyback AC-DC converter using an integrated digital isolator in isolated communication

This paper presents a 45w (20V, 2.25A) output active clamped flyback (ACF) AC-DC controller using a capacitor-coupled integrated digital isolator in isolated communication in place of a bulky optocoupler, which not only helps to reduce system volume but also improves the reliability of the ACF converter. In contrast with the conventional ACF, the controller in this paper features a delicate adaptive zero voltage switching (ZVS) control to reduce conduction and switching losses so as to improve the power efficiency. Designed in a 0.18-μm isolated BCD process, the simulation result shows the proposed ACF converter approached 95.1% maximum efficiency when GaN power transistors are used as power switches. The feasibility of the proposed digital isolator is also verified and exhibits high transmission accuracy with low propagation delay.