A Low Flicker TRIAC Dimmable Direct AC LED Driver for Always-on LED Arrays

Direct AC LED drivers have advantages over conventional LED drivers in size and cost because of no need for bulky and expensive inductive components. However, none of conventional direct AC LED drivers researched so far support triode AC switch (TRIAC) compatibility at low percent flicker. This paper achieves both TRIAC dimmer compatibility and low percent flicker by correlating a phase-cut ratio to luminance and using always-on multi-arrays, respectively, without the need of a dedicated IC. The proposed LED driver consists of a phase-cut/DC converter, a switch controller, a current regulator, and three LED arrays. The experimental results based on commercial 15W LEDs show that the percent flicker of 18.6% @ 120 Hz is achieved with an efficiency of 84.7% and a power factor of 97.3% @ 120 V.