A High PFC Integrated AC–DC Circuit With Inherent Lossless LCD Snubber

This research presents an isolated single-stage-single-switch integrated LED driver with high efficiency, high input power factor (IPF), and in compliance to the stringent IEC61000-3-2 and ENERGY STAR standards. The proposed integration combines the power factor correction (PFC) SEPIC and power control (PC) flyback converters. The flyback converter in the PC stage operates in DCM to achieve a higher IPF. The PFC stage consists of an inductor-capacitor-diode (LCD) which together functions as an inherent lossless snubber. The LCD clamps the peak voltage spike of the switch to a lower voltage during the switching transient. In addition the inherent LCD snubber recycles the leakage inductance energy which is shared between the PFC stage and the load. The inherent snubber operation reduces the extra cost and space that would incur because of an additional auxiliary snubber circuit. Unlike a conventional AC-DC system with a snubber, the driver works in a non-resonant mode. The proposed system's operating principles, mathematical analysis, and theoretical conclusion are discussed. The simulation results are verified by using a 60W/65V hardware prototype. The proposed topology achieve an efficiency of 91.8% with an IPF of 0.995 with less than 5% input current harmonics.