Recently, the switched-mode power supply, as a light, a small size, and a high effective power supply, is used for all most electronic equipment because of the advancement of the power electronics. However, power supplies connected to AC mains introduce harmonic currents in the utility due to their capacitor-input rectifier filters. It is well known that these harmonic currents cause several problems such as voltage distortion, heating, noises and reduce the capability of the line to provide energy. This fact and the presence of standards or recommendations have forced to use power factor correction in power supplies, even some regulations like IEC 61000-3-2 are recommended. And a lot of circuit configurations about the power-factor-correction (PFC) technique have been proposed.
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