High-precision constant current controller for primary-side feedback LED drivers

This paper presents a novel constant current LED controller with primary-side feedback control method for flyback topology. The method is proposed based on sampling input peak current and secondary-side electric information detected by an extra auxiliary winding. Eliminating opto-isolator, the controller can still regulated the output current precisely by designing special sample circuit and compensating signal propagation delay. A prototype with 7 LEDs has been built to verify the control method. The experiment's results meet the design requirements of 3% current regulation in a wide range of input ac voltage from 85 V to 265 V.