Recently, rectifier usage has been increasing in industry. Rectifiers are known as nonlinear loads causing harmonic distortion in power grids. For this reason, power factor correction (PFC) converters are employed to create a sinusoidal current which is in phase with line voltage. Thus, many standards are established to limit the total harmonic distortion of the converters. One of the definitions for measuring harmonic distortion is power factor. Power factor is calculated from the ratio of real power to apparent power. In this thesis, at first the definition of power factor and its mathematical relations are presented and then the advantages and disadvantages of basic switching converters are mentioned. To increase the efficiency, bridgeless PFCs are reviewed. In bridgeless PFCs, the rectifier is combined with the PFC converter to create a new converter. Because the number of semiconductor devices are reduced in bridgeless PFCs, the conduction losses are reduced and the efficiency is increased. Bridgeless PFC converters are divided in to three categories: step up, step down and step up – step down. The advantages and disadvantages of each type of these converters are based on what type of basic switching converter is used. Due to high output voltage of boost PFC converters, they are not used in low output voltage applications. In this thesis, to use the converter at low output voltage applications, buck PFC converter is investigated. Buck type converters have the advantage of low output voltage and capability of converter protection at overload condition. However, dead angle, floating gate drive and hard switching are the disadvantages of this converter. To overcome some of the disadvantages and increasing the performance of this converter, Discontinuous Capacitor Voltage Mode (DCVM) is employed. Buck type converters in DCVM are benefited from inherent PFC, Zero Voltage Switching (ZVS) at switch turn off, and shorter dead angle than other converters. Therefore, in this thesis, a new bridgeless buck converter is proposed which operates in DCVM. The proposed converter provides ZVS at switch turn off, small dead angle and offers inherent PFC characteristic. One of the drawbacks of DCVM converters is high voltage stress for semiconductor devices. To solve this issue, three level converters are employed. Three level converters can half the voltage stress. In this thesis, three level converters technique are combined with the proposed converter and new three level bridgeless buck converter is proposed. Since, DCVM only provides ZVS at turn off for the switches, the proposed converter is redesigned in Discontinuous Inductor Current Mode to reduce the turn on switching loss. At last, the proposed converter has major advantages such as good efficiency, lower voltage stress than other converters, less dead angle, and simple feedback circuit due to the inherent PFC capability. The operation of the proposed discontinuous capacitor voltage mode bridgeless buck converter is mentioned in details. Also, the proposed converter at various operating conditions is analyzed. Finally, the proposed converter is designed and simulation results are presented. To verify the theoretical analysis, the proposed converter is implemented and the results are provided. Keywords Power Factor Correction Converters, Bridgeless PFCs, Discontinuous Capacitor Voltage Mode, Three Level Converters