Analysis and design of a single-stage buck-type AC-DC adaptor

A modified asymmetrical half-bridge flyback converter (AHBFC) to fulfill the single-stage buck-type AC-DC adaptor for notebook application is proposed in this paper. The modified AHBFC is obtained from the integration of a buck converter and a conventional AHBFC. The modified AHBFC is operated in the discontinuous conduction mode to achieve the high input power factor to meet the required regulations. Also, the modified AHBFC can achieve the zero voltage switching (ZVS) for the switch and the zero current switching (ZCS) for the output diode to improve the efficiency. Moreover, the transformer's leakage inductor is utilized as the resonant inductor so the circuit structure is further simplified. The operation principles, important characteristics, and equation derivations of the proposed buck-type AC-DC adaptor are explained. A design example of a 100 W prototype is presented. Computer simulation and experimental results with universal input voltage ranges are obtained to verify the performance of the proposed buck-type AC-DC adopter.