LED Driver with TRIAC Dimming Control by Variable Switched Capacitance for Power Regulation

Abstract

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below ± 2% for 190 V < V s < 250 V by using the proposed simple control circuit.

Long-Lasting and Highly Efficient TRIAC Dimming LED Driver with a Variable Switched Capacitor

“…9 was fabricated with a silicon steel plate core, and the parasitic resistance of the fabricated inductor L 1 was measured as 13.0 Ω. The current rating of the fabricated inductor was 550 mA, and the total weight of the prototype LED driver was measured as 960 g. The inductor L 1 and proposed LED driver weighed 930 and 30 g, respectively; hence, the proposed LED driver is lighter and smaller than conventional TRIAC dimming LED drivers weighing 1,390 g [30], [31].…”

“…The other circuit parameters of the DC power supply circuit and feedback control circuit, as shown in Fig. 1, can be determined by a design procedure [30], [31]. The proposed Fig.…”

“…1, is based on the previous TRIAC dimming LED driver [30], [31]; hence, except for a passive input filter and a variable switched capacitor, the other circuit components such as a DC power supply circuit and a feedback control circuit are the same as previous one. In order to provide this LED driver with an LED power control function, a conventional TRIAC switch with a DIAC is inserted in series with C 1 to vary the connecting time portion of C 1 in a switching period, which results in a variation of equivalent capacitance for the proposed variable switched capacitor.…”

“…In this paper, a TRIAC dimming LED driver, which reduces the number of passive components in the passive input filter and improves power efficiency in comparison with the aforementioned TRIAC dimming control LED driver [30]- [31], is proposed, as shown in Fig. 1.…”

“…In order to provide LED power regulation capability with high efficiency and long-life characteristics, a triode for alternating current (TRIAC) dimming control LED driver with a passive input filter was proposed [30], [31]. This LED driver adopts a variable switched capacitor to modulate LED power, which can be controlled through the turn-on duration of a TRIAC together with a diode for alternating current (DIAC); in this way, it was proven that LED dimming and LED power regulation are successfully achieved.…”