A step-down converter with low ripple input current for power factor correction

Step-down converters can be used to achieve power factor correction when a low output voltage is desired. The paper analyzes a nonisolated, two-inductor, step-down power converter and presents its application to power factor correction, when operating in the continuous conduction mode with average current mode control. The input current of the converter is continuous, since one of the inductors is on the line side. Moreover, for a proper coupling of the two inductors, the ripple of the input current can be significantly reduced. Thus, a PFC preregulator with low output voltage and low-ripple input current is obtained. The paper also presents experimental results for a 48 VDC output-voltage and 200 W output-power power factor correction preregulator, operating with 230 VRMS input voltage.