Study and implementation of an improved-power factor alternating-current-light emitting diode driver

In this study, a novel driver converter for the alternating-current light emitting diode (AC-LED) is proposed to improve the input power factor (PF) and reduce current harmonics. The presented driver consists of an LED-bridge rectifier and an LED string which is divided into controlled and uncontrolled parts by a low switching-frequency metal-oxide semiconductor field effect transistor. The influences of the LED number in the bridge rectifier on the peak reverse voltage of the LED string and the input current command are investigated. The relationship between the input inductance and the maximum input current ripple is studied. In addition, the effects of the LED number on the LED string on the switch voltage rating, input PF, current harmonics and conversion efficiency are presented. The experimental results show that the proposed AC-LED driver features a high efficiency and input PF, and is compatible to the TRIode for Alternating Current-dimmer. Comparisons between the proposed and the conventional AC-LED drivers will also be given to verify the improved features.