The use of electronic devices is increasing day by day. Meanwhile, most electronic equipment requires direct voltage for proper operation, while the most accessible power source is the AC mains supply. This has led to a growing use of rectifiers. Since rectifiers are nonlinear loads, their connection to the grid results in the injection of current harmonics into the network, thereby distorting the current waveform from its sinusoidal form. One of the most widely used methods for converting AC voltage to DC is through switched-mode power supplies (SMPS). In these power supplies, the mains AC voltage is first rectified an‎d then regulated by control circuits to the desired level for the load. The rectification process is performed by a diode bridge an‎d a smoothing capacitor. However, due to the nonlinear nature of this structure, it draws non-sinusoidal currents from the grid. Drawing non-sinusoidal currents from the grid leads to the injection of harmonics into the power system, which causes various problems in the network. To prevent an‎d limit the level of harmonics injected by consumers into the grid, specific stan‎dards have been established. Compliance with these stan‎dards is essential for all electronic equipment connected to the power grid. Therefore, the implementation of power factor correction (PFC) circuits in power supplies is of great importance to reduce the harmonics injected into the power distribution network. Moreover, due to the high cost of energy, there is a deman‎d for power supplies that achieve maximum efficiency an‎d minimize consumer costs. In this thesis, three single-stage power factor correction converter topologies are proposed with the objective of reducing losses an‎d improving efficiency. The first proposed converter, which is a combination of flyback an‎d boost converters, utilizes a synchronous switch to achieve soft-switching conditions, thereby eliminating switching losses an‎d reducing conduction losses. However, due to the use of a diode bridge, a portion of the input power is dissipated across the rectifier diodes, resulting in reduced efficiency. To address this issue, the second proposed converter is introduced. In this structure, by integrating the input rectifier diodes with the power switches, losses are reduced an‎d efficiency is improved. In addition, a supplementary circuit is employed to achieve soft switching. Nevertheless, part of the power is still dissipated across the output diode, which lowers efficiency. To overcome this limitation, the third proposed converter is presented. This converter is a bridgeless, single-stage structure with only one power switch. By adding a synchronous switch, the output diode losses are eliminated, leading to enhanced overall efficiency. The first an‎d second proposed converters are fully analyzed, an‎d laboratory prototypes are constructed to verify their performance an‎d validate the theoretical analyses. The experimental results confirm the proper operation of the proposed circuits. Furthermore, due to the implementation of soft switching an‎d the reduction in the number of semiconductor components in the power path, the efficiency of the proposed converters is improved compared to existing structures.

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