A Single-Stage Single-Switch Soft-Switching Power-Factor-Correction LED Driver

This paper proposes a new isolated single-stage single-switch soft-switching power-factor-correction (S6-PFC) driver without electrolytic capacitors for supplying light-emitting diodes (LEDs). In the proposed LED driver, all the semiconductor devices are soft-switched without employing any extra active switch. The leakage inductance of transformer acts as a resonant component so that the leakage energy is recycled. Soft-switching operation of the semiconductor devices together with absorption of the leakage energy improve the proposed driver efficiency. Furthermore, input current of the driver has very low harmonics resulting in high power-factor. Operating principles of the proposed S6-PFC LED driver as well as its design guidelines are presented. Also, experimental results of a laboratory prototype for supplying a 21W/30 V LED module from 220 V/50 Hz ac mains are provided to verify the theoretical analysis. The presented results show that the implemented prototype has an efficiency of 92% under full-load condition and its input current total harmonic distortion is as low as 2.6%.