A primary side controlled WLED driver compatible with Triac dimmer

This paper proposes a single-stage Flyback PFC Converter with new primary side control scheme for Triac compatible LED drivers. The proposed control scheme can achieve high power factor and efficiency by eliminating the conventional dummy load required for Triac dimmer. Also, almost linear dimming can be achieved by the phase angle feed forward and primary side constant power control. No secondary side current feedback is required, which dramatically simplify the whole circuit and increases the reliability. The detailed operation principles are presented and the experimental results for a WLED driver verified the theoretical analysis.