Output inductor-less active clamp forward converter employing current boost-up circuit for high power density adaptor

Nowadays, as the demand of portable electric products is increased, that of adaptors, which charge the battery of portable electric products or supply power, is also increased. Key issues of portable electric products are power density, temperature, average efficiency and stand-by power. Many isolated DC/DC converter topologies suitable for high power density is presented [1]∽[3]. All of them try to reduce size and cost by minimizing the number of components. Generally, converter topologies which have no output-inductor for DC/DC converter is suitable for high power density application. Active clamp flyback converter and output-inductor-less forward converter are representative converters without output inductor. However, these converters have critical problems. In active clamp flyback converter, DC offset current which degrades transformer utilization and makes transformer bulky. Therefore it causes low power density. In the other side, output-inductor-less active clamp forward converter has high RMS value of current which causes heat problem. This paper proposes an output-inductor-less active clamp forward converter employing current boost-up circuit for adaptors. Due to applying the proposed current boost-up circuit, the proposed converter has low conduction loss and low voltage ringing of the secondary rectifier. This paper presents the operational principle and design consideration of the proposed converter. Experimental results are demonstrated to verify the feasibility and advantages of the proposed converter.