A Two-Stage Quasi-Resonant Dual-Buck LED Driver with Digital Control Method

A two-stage quasi-resonant LED driver with a digital control method is proposed in this paper. The first stage of this converter is a boost circuit with a power factor correction function, and the second stage is a dual-buck circuit that works in a quasi-resonant zero voltage switching state. Because of the soft-switching characteristics of the converter, switching losses are reduced and efficiency is significantly improved. A digital control method is adopted to detect the peak value of inductor current and enhance system reliability. Moreover, because LEDs are always driven by a current source, a current loop is designed to maintain constant output current. IRS2104 is chosen as the drive chip and the microcontroller is AT90PWM216, which can improve the quality of the drive signals. The output of the converter is a square wave that drives two branches of antiparallel LEDs. A 60-W prototype was designed to demonstrate the theoretical analysis. The obtained power factor was as high as 0.987 and the efficiency reached 92.3%.