새로운 방식의 전해커패시터 없는 LED구동용 AC-DC 컨버터

Abstract

Nowadays, LED lighting is a popular application because of the advantage such as long life, environmental friendliness, high efficacy, etc. Moreover, The LED lighting has a lifespan range of 50,000 hours to 100,000 hours which is very longer than that of the conventional incandescent lamp. For this reason, LED lighting market is steadily growing. However, because the lifespan of the converter for the LED drive is not as long as the LED itself due to electrolytic capacitors it hinders the most useful advantage of LED lighting. For this reason, recently, various methods for electrolytic capacitor-less AC-DC converter for LED drive have been developed. Since the luminous flux of LED increases with the average value of the LED drive current, pulsating current is available for the LED drive. In this paper, a new single-stage flyback power converter with PFC for electrolytic capacitor-less LED driver is proposed. In order to minimize the peak-to-average ratio of the LED driving pulsating current, proper current is added to the LED driving current near the current valley area as well as the third harmonic component injection into the input current. The added current is provided by the auxiliary circuit connected between the positive and negative sides of the input rectifier output. In this proposed scheme, capacitance capacity of the capacitor is as small as 10uF. It means that different type of long life time capacitor with low cost can be used instead of electrolytic capacitor. Operating principle of the proposed converter is described in each operating mode. Simulation and experimental results show the usefulness of the proposed topology. The peak-to-average ratio of the LED driving current is 1.482 which is the lowest value obtainable in pulsating LED current drive converters. The input PF is 0.92 which is high enough to satisfy the requirement of the KS standards. The input current THD requirement is also satisfied according to IEC 61000-3-2 Class C standards.