Why does TRIAC dimming flicker? Compatibility checks and selection advice
TRIAC flicker usually comes from a mismatch between dimmer and driver: a leading-edge dimmer oscillates on a capacitive input, and operation becomes unstable below the dimmer's minimum wattage. Check the compatibility list, calculate the minimum load, and switch to 0-10V or DALI if it still fails.
Why TRIAC dimming fights with the driver
A TRIAC dimmer removes part of the AC waveform to reduce the effective voltage; there are leading-edge and trailing-edge types. Leading-edge is simple and cheap, but its steep rise excites current spikes in the driver's input filter capacitors, so the dimmer misreads the load and the lamp may buzz or visibly flicker.
On-site check order
Light one lamp alone first to rule out mixed driver brands on the same circuit; then swap in a dimmer known to be compatible as a control; then connect a sufficiently rated dummy load and see whether the flicker disappears, which points to an insufficient minimum load; finally check the driver's rated minimum load against the dimmer compatibility list.
Three fixes and alternatives
When the minimum load is insufficient, reduce the number of lamps per circuit or add a dummy load; when the topology mismatches, use a trailing-edge dimmer; if the protocol is not yet locked, switch to 0-10V or DALI digital dimming and avoid the phase-cut versus capacitive-load conflict altogether.
| Symptom | Check first | Action |
|---|---|---|
| Flickers only at low level, fine at full output | Dimmer minimum load not met | Reduce lamps per circuit or add a dummy load |
| Slight shimmer across the whole range | Leading-edge cut versus capacitive input mismatch | Use trailing-edge, or move to 0-10V / DALI |
| Accompanied by a faint buzz | Filter capacitor resonating with the cut frequency | Use a low-ripple driver, or switch to digital dimming |
Frequently asked questions
Can every LED lamp be TRIAC dimmed?
No. The driver input must explicitly support phase-cut dimming and fall within the dimmer's compatibility list and power range.
Does a dummy load waste power?
A dummy load is only for on-site diagnosis. The long-term fix is higher per-lamp wattage or a digital dimming protocol.