In electrical equipment’s low power factor in power systems caused by power converters have been of great concern. To overcome these problems several converter topologies using advanced semiconductor devices and control schemes have been proposed. This invest igation is to identify a low cost, small size, efficient and reliable AC to DC converter to meet the input performance index of UPS. The performance of single phase and three phase AC to DC converter along with various control techniques are studied and compared. This project presents a novel AC/DC converter based on a flyback converter based active Power Factor Correction  ( PFC )  scheme. In the proposed method, the power factor is improved by using an auxiliary winding coupled to the transformer of a cascade AC/DC flyback converter.The auxiliary winding is placed between the input rectifier and the low-frequency filter capacitor to serve as a magnetic switch to drive an input inductor. Since the AC/DC converter is operated at high-switching frequency, which results in lower cost and higher efficiency. Finally a DC motor load is applied and hardware results are presented.