AC/DC converter free LED driver for lightings

This paper presents a noble AC/DC converter-free LED driver for LED lighting applications. The presented LED driver applies the AC mains power directly to the LED strings with no AC/DC converter stage, thus bulky transformer and life-time limiting electrolytic capacitor no longer needed. This small-sized, low-cost and reliable LED lighting driver was realized with an LED driver IC, which selectively empowers multi-channel LED strings based on the measured input AC voltage signal. The IC was fabricated in 1-um high voltage BCD process capable of handling AC input voltage up to 240 V. By PWM-controlling the LED-driving high-voltage switches, the IC resolved the thermal issue which is critical for the reliability of LED lighting module. A 4-W prototype LED driver module was implemented and tested to verify the feasibility of the suggested Converter-/Capacitor-less (ie. CC-less) LED driver scheme for low cost LED lighting.