Design on PFC circuit of BOOST convertor under critical conduction mode

WANG Jie
(Chongqing Branch of Chinese Coal Research Institute, Chongqing 400037, China)

Abstract: Aiming at the problem of power factor correction(PFC) in critical conduction mode, taking the BOOST electric circuit as object of study, the input current formula of PFC circuit in the critical conduction mode was deduced, a detailed analysis of steady characteristics of BOOST switch convertor was made for power factor correction in the critical conduction mode, the relation of switching frequency with input voltage and power was concluded. It was proposed that special IC simplifies PFC control chip was used to adjust the opening time of switch tube, its shutoff conditions were improved and the working efficiency of the whole circuit was enhanced, and the purpose of improving power factor was achieved. The study results indicate that the constant switch conduction time in the half work cycle of input power can realize the converter unity power factor work, which provides a theoretical basis for the convertor design.
Key words: critical conduction; BOOST convertor; power factor correction(PFC)