Low THD Variable Load Buck PFC Converter

International standards impose several constraints concerning the electric power quality and require that the harmonic content of the line current of grid connected equipment is below assigned limits; for this reason operating of ac-dc converters with high power factor and low line current distortion has become essential. In this paper a single phase buck type PFC converter based on discontinuous capacitor voltage mode is presented for grid connected 1kW-48Vdc applications. With proper design, low total harmonic distortion and power factor close to unity over a wide load range are easily achieved by means of the proposed buck PFC converter. Good results for the proposed PFC are achieved when combined operating conditions are provided, discontinuous capacitor voltage mode for input capacitor and discontinuous inductor current mode for output inductor.