Input-Current Distortion of CCM Boost PFC Converters Operated in DCM

Abstract

<para xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> When power-factor correction (PFC) converters designed for operation in continuous-conduction mode (CCM) at full power are operated at reduced load, operation in discontinuous-conduction mode (DCM) occurs in a zone that is close to the crossover of the line voltage. This zone will gradually expand with decreasing load to finally encompass the entire line cycle. Whereas, in CCM, the parasitic capacitances of the switches only cause switching losses, in DCM, they are a source of converter instability, resulting in significant input-current distortion. In this paper, this source of input-current distortion is analyzed, and a solution is proposed. Experimental results are obtained using a digitally controlled boost PFC converter, which is designed to operate in CCM for 1 kW. </para>