Primary-controlled constant current LED driver with extremely low THD and optimized phase-cut dimming compatibility

This paper describes a novel control method for high-power-factor quasi-resonant (Hi-PF QR) flyback converters able to meet simultaneously three control objectives: a) performing constant-current control with primary sensing regulation (CC-PSR); b) achieving ideally no harmonic distortion of the ac input current; c) being fully compatible with real-world “phase-cut” wall dimmers. Simulation results and experimental verification data are provided to validate the method, which has been implemented in a control IC targeting solid state lighting applications (LED drivers).