Primary side control circuit of a flyback converter for HBLED

This paper presents a constant-current power supply for HB-LED(High Brightness LED). The proposed power supply is designed and implemented by adopting a flyback converter with primary side control and without galvanic isolation. Based on discontinuous conduction mode (DCM), the flyback converter has constant average output current when the peak current on the transformer primary side and the ratio of t´off to TS are constant. A laboratory prototype based on UC3843 PWM controller has been built and tested. Laboratory experimental results from a 12.6W prototype are given to verify the validity and effectiveness. The converter meets the performance requirements of HB-LED driver with ±3% current accuracy in the wide output voltage range.