The analysis of TRIAC dimming LED driver by variable switched capacitor for long life and high power-efficient applications

Abstract

The analysis of the proposed TRIAC dimming LED driver, which adopts a variable switched capacitor, is proposed in this paper. Because the proposed LED driver adopts a TRIAC switch as the main switch, it is proven to be power-efficient and reliable over long life. Similar to the previous TRIAC dimmers of lamps, turn-on timing of a TRIAC can be controlled by a volume resistor in the proposed LED driver, which modulates the effective capacitance of the variable switched capacitor. Thus, LED power regulation for source voltage change and LED dimming control can be achieved, meeting the standard of power factor (PF) and total harmonic distortion (THD). Because the proposed LED driver has long life and high power efficiency characteristics, it is adequate for industrial lighting applications such as street, factory, parking garage, and emergency stair. The detail analysis of the proposed LED driver is presented in this paper. A prototype of 80 W was fabricated and verified by experiments, which show the efficiency, PF, and THD at V s = 220 V are 93.8%, 0.95, and 22.5%, respectively, and the LED power variation is well mitigated below 3.75% for 190 V s < 250 V.