Analysis of buck converters used as power factor preregulators

Abstract

Buck-type converters are analyzed for application as power factor preregulators. In particular, the maximum power for which the IEC 1000-3-2 standards are met is calculated for different conversion ratios and modulation techniques. Two step-down converters are proposed, which comply with EMC standards thanks to an auxiliary flyback stage which uses the same switches of the main converter plus a small power switch commutated at the line frequency. With proper design, the voltage stress of the main switch remains the same as for a conventional buck topology. Simulations and experimental results are reported to validate the theoretical analysis.