Design and implementation of high frequency AC-LED driver with digital dimming

In this paper a two-stage high frequency AC-LED driver is designed and studied. The front-stage is a boost power-factor correction (PFC) circuit and the rear-stage is a halfbridge series resonant inverter. The lighting characteristics of high frequency AC voltage driving LEDs, and the effect of LED to half-bridge resonant circuit are discussed. The proposed design uses the digital dimming control to reduce LED chromaticity shift, and connect the LEDs as a full-bridge rectifier to simplify the current sensing circuit. An 80-W high frequency AC-LED driver with universal voltage input (90~264 Vrms) is implemented to verify the design. Experimental results show that the variation of chromaticity coordinates (u´, v´) from brightness 100% to 20% is within 0.0023.