A single stage single switch power factor corrected AC/DC converter

This paper presents a single stage single switch isolated power converter topology to achieve a regulated DC output voltage having no low frequency components and a high input power factor. The topology is derived from the basic forward power converter, but incorporates an additional transformer winding, an inductor, and a few diodes. The proposed circuit inherently forces the input current to be discontinuous and AC modulated to achieve high input power factor. Both duty cycle and variable frequency controls are used to regulate the output voltage and to minimize DC capacitor voltage variations. Analysis of the power converter is presented and performance characteristics are given. Further, design guidelines to select critical components of the circuit is presented. Finally, experimental results on a 50 W, 110 VAC to 5 VDC power converter are given which confirm the high efficiency and high power factor features of the proposed topology.