Non-linear loads will force current harmonics to the grid. These harmonics will increase the grid losses and therefore, the grid is not used effectively. Furthermore, theses harmonics can have unwanted effects on other loads. Therefore, IEC standards are enacted to limit current harmonics produced by the users. Usually, two stage converters are used as power factor correction circuit. The first stage forces a sinusoidal current to the grid and the second stage meets the requirements of the load. For low power applications the power factor correction stage and voltage regulation stage are combined to simplify the circuit. Theses converters are known as single stage power factor correction circuits. These converters are preferred for low power applications. In this thesis single stage power factor correction converters are studied. Theses converters are usually based on isolated converters such as flyback converter and suffer from voltage spikes across converter switch. In this thesis two new single stage power factor correction circuits with active clamp are presented. The control circuit is simple and just a simple voltage controller is required. Furthermore, active clamp circuit provides soft switching condition. The proposed converters are analyzed and the advantages are discussed. The converters are simulated and simulation results justify the theoretical analysis. Also, a prototype converter is implemented. Keywords: Power Factor Correction (PFC), single stage Power Factor Converter, Soft Switching, Flyback-forward Converter, Flyback Converter, Active Clamp Circuit
