: Recently years using switching power supplies are vastly applied for electronic devices. Therefor many reaches are performed to improve DC-DC converters.These converters inject many current harmonics to power system. Harmonics cause instability and losses in the power systems. Thusadding power factor correction (PFC)circuits to the input of switching power supplies is necessary. Therefor switching power supplies implemented in two stages: input stage that forms the input current and removes the current harmonics. Output stage is a converter that regulates the output voltage.For reducing cost and complexity of switching power supply, single stage power factor correction converters are introduced. In this kind of PFC converters, two stages are combined. Various topologies of single stage PFC converters are introduced in literature. Many single stage PFC converters apply boost converter as the input stage. The boost converter operates under discontinues conduction mode. For implementation of single stage PFC converter, this boost converter is combined with flyback or forward convertersas the voltage regulator. Single stage PFC converters have attractive properties such as simple structure and low cost, but suffer fromhigh voltage stress across bulk capacitor and power switch. Also,input current is discontinues and an additional LC filter is required. In this research, various kind of single stage PFC converters are investigated. Then, a new single stage PFC converter is presented to improve conventional single stage PFC converters. This converter applied buck converter as input current shaper. The buck converter operates under discontinues voltage mode. Flyback converter is used as the output voltage regulator. By combining these converters, new single stage PFC converter is implemented. Design considerations are discussed and simulation results are presented. Then a prototype is implemented to verify the theoretical analysis. Efficiency is another important issue in the DC-DC converters. Single stage converters have lower efficiency in comparison to other PFC converters. This is due to the switching and conduction losses. Soft switching technics are applied in these converters to reduce switching losses. For reducing switching losses and increasing the efficiency soft switching techniques are applied inthe proposed converter. Thus, a single stage soft switching PFC converter is presented. The proposed soft switching converter is analyzed and simulation results are presented to verify theoretical results.
