A novel TRIAC dimming LED driver by variable switched capacitance for power regulation

A novel TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variation is proposed. Contrary to conventional PWM LED drivers, proposed LED driver uses TRIAC as a main switch, which inherently guarantees zero current switching and proven to be quite reliable. These characteristics can significantly improve switching loss and provide a long lifetime, which is requisite for LED drivers. The power of the proposed LED is regulated by variable switched capacitance, which is modulated by the TRIAC turn-on timing. Moreover, dimming control is obtained, in the same way of conventional TRIAC dimmers of lamps, by a volume resistor, which changes the current slope of a controlled current mirror of the proposed feedback control circuit. A prototype LED driver of 80 W was implemented with a TRIAC and DIAC, and verified by experiments, where the power factor and total harmonic distortion are 0.94 and 18.9 %, respectively. The maximum LED power variation was well mitigated below 2.5 W for 190 V <; V_s <; 250 V by using the proposed simple control circuit.