An auxiliary winding with an associated capacitor is added on the single-stage power factor corrector (PFC) based on fly-back conversion to reduce the ripple on the dc output voltage. The associated capacitor takes out partial energy at every switching cycle from the fly-back conversion and releases the stored energy to the load at the valley of the rectified line voltage. The negative effect of such an approach is that the converter does not draw a current from the AC line at the lower voltage near zero crossing, leading to deterioration in the power factor. This thesis analyzes how an auxiliary winding affects the voltage of the associated capacitor, which in turn changes the cut-in angle of the input current and thus the power factor of the AC source. To facilitate the implementation, the fly-back converter is operated at the boundary conduction mode (BCM). A design example is given for the 24 V, 48 W load, based on the derived equations. The laboratory circuit is built and tested to verify the computer simulations and analytical predictions. The experimental results confirm the circuit analyses on the converter performances.