Using existing triac controllers and wiring offers a number of challenges for LED lighting. To maximize the success and adoption of solid-state lighting for retrofit lamps, the LED lamps should be capable of dimming when used with existing controllers and wiring.
Lighting designs with flicker-free LED dimming article explores the typical TRIAC dimmer, some of the challenges of using it with LED lighting, and two interesting new power management solutions that solve these issues.
A common lighting dimmer available today is the leading-edge TRIAC dimmer. For an LED lamp to be dimmable, the lamp’s power supply must interpret the variable phase angle output from the TRIAC controller to monotonically adjust the constant current drive.
The difficulty of achieving this while keeping the dimmer working correctly may result in flickering, audible noise, and blinking as the light level is adjusted. These are generally caused by a combination of false triggering or premature shutdown of the TRIAC and inadequate control of the LED current. For reliable dimming down to low levels, the TRIAC must remain conducting almost to the point where the AC voltage falls to zero.