Why do LEDs flicker only when dimmed low, how do you diagnose dimmer type versus bulb driver quality?

[Gralsritter]

Quick question for the lighting folks here. I’ve got LEDs that only flicker when they’re dimmed down near the bottom, and it’s weird because mid range and full brightness look perfectly stable.

A specific moment was last weekend when I tried to set the lights super low before bed and the flicker kicked in immediately, then stopped as soon as I nudged the dimmer up a bit. What’s your usual way to narrow this down, like checking if the dimmer is leading edge or trailing edge, trying a known compatible bulb, adjusting the low end trim if the dimmer has it, and figuring out when it’s just a cheap driver that will never behave?

 

[Alan]

Low end flicker is usually the dimmer and LED driver not agreeing on the minimum load. First easy test is swap in one known dimmable LED that is on the dimmer compatibility list, then see if the flicker changes. If your dimmer has a low end trim adjustment, set it so the lowest setting is slightly higher, that often fixes the bottom range flicker.

 

[General_Valeria]

This is usually dimmer and bulb compatibility, not “bad wiring.” At low dim levels, cheap LED drivers struggle and flicker shows up first. I start by confirming the dimmer is rated for LED, then try one known good dimmable LED bulb. If that fixes it, the old bulbs are the issue. If your dimmer has a low end trim, setting that helps a lot.

 

[TankReyn]

Check minimum load on the dimmer. Some dimmers need more load to stay stable, and a few LED bulbs do not give enough. That is when flicker shows up only at the bottom. If adding one more bulb or swapping to a low load LED dimmer fixes it, you found the cause.