Single Stage Quasi Active Power Factor Correction Scheme of AC/DC Rectifiers

ABSTRACT : In the proposed system, the power factor is improved by using an auxiliary winding coupled to the transformer of a cascade dc/dc fly back converter. The auxiliary winding is placed between the input rectifier and the low-frequency filter capacitor to serve as a magnetic switch to drive an input inductor. Since the dc/dc converter is operated at high-switching frequency, the auxiliary windings produce a high frequency pulsating source such that the input current conduction angle is significantly lengthened and the input current harmonics is reduced. It eliminates the use of active switch and control circuit for PFC, which results in lower cost and higher efficiency. In order to achieve low harmonic content, the input inductor is designed to operate in discontinuous current mode. Since the use of a single inductor, the cost is reduced and the efficiency of the system is improved. The power factor is maintained constant by using a buffer capacitor in parallel to the system for compensating the inductive components.