Experimental verification of a linear AC LED driver with a light flicker compensating circuit and high power factor operation by modulating the current regulator

Abstract

This article proposes a linear PFC regulator with a light flicker compensating circuit for LED lighting applications. The proposed circuit is small in size because it includes no reactors or electrolytic capacitors. The light flicker compensating circuit, which is connected in parallel to the LED string, consists of four ceramic capacitors and diodes. These capacitors are operated in series in the charge state and in parallel in the discharge state by using a diode network circuit. Therefore, an external controller and large capacitors are not required. The proposed circuit is experimentally validated using a 9 W prototype. From the experimental results, it is found that the power fluctuation of the LED string is less than the JIS and JLMA limitations, and the power factor is 0.95. In addition, the power loss is analyzed at an efficiency of 89.4% for the prototype circuit. Also, by modulating the current regulator, sinusoidal input current can be achieved. The second proposed circuit is experimentally validated using a 7.5 W prototype, and the power factor and input current distortion are found to be 0.999 and 2.1%, respectively.