Performance characterization of two self-oscillating controllers for parallel resonant converters operating with unity input power factor

Single stage AC/DC converters based on series-parallel resonant circuit and operating above the resonance frequency provide high input power factor. However, with conventional variable frequency control, zero voltage switching may be lost in some operating conditions. In this paper two control techniques for resonant converter operating above resonance frequency are compared. These control techniques ensure zero voltage switching in all operating points allowing operation at high frequencies. A design procedure is suggested for the selection of resonant circuit parameters. Finally experimental results from a 500 W power factor corrected AC/DC power supply are given to verify the predicted results