Definition
TRIAC (Triode for Alternating Current) dimming, also called phase-cut dimming, works by chopping off a portion of each AC voltage waveform to reduce the average power delivered to the light source. Leading-edge TRIAC dimmers cut the beginning of each half-cycle; trailing-edge (ELV/reverse-phase) dimmers cut the end. Originally designed for incandescent bulbs (purely resistive loads), TRIAC dimming requires special 'TRIAC-dimmable' LED drivers that can interpret the chopped waveform and convert it to a smooth dimming signal for the LEDs. TRIAC is the dominant residential dimming method because it works with existing 2-wire wall-box wiring (no additional control wires needed), but it can cause flicker, audible buzz, and limited dimming range if the driver and dimmer are not carefully matched.
Key Data
| Parameter | Value / Explanation |
|---|---|
| Wiring | 2-wire retrofit-friendly (line + neutral or line + load) — no additional control wiring |
| Dimming range | Typically 100% to 10-20% minimum. Premium LED drivers + matched dimmers achieve 5% |
| Compatibility | CRITICAL: dimmer and LED driver must be tested together. Mismatched pairs cause flicker/buzz. |
| Best application | Residential retrofit (replace incandescent dimmer with LED-compatible dimmer). <20 fixtures. |
| Not recommended for | Commercial projects >20 fixtures, precision dimming, or applications requiring smooth fade-to-black |
Application Guide
Residential retrofit
TRIAC-dimmable LED + compatible phase-cut dimmer (Lutron, Leviton LED-rated)
Reuses existing 2-wire wiring; homeowner-friendly; no electrician required
Small hospitality (boutique hotel)
TRIAC acceptable for guest rooms <10 fixtures; DALI for public areas
TRIAC is cost-effective at small scale; DALI for scene-setting in lobby/restaurant
Commercial office
0-10V or DALI — avoid TRIAC for ≥20 fixtures
TRIAC doesn't scale; per-fixture dimmer cost exceeds 0-10V at quantity; no energy reporting
Conclusion & Procurement Recommendation
TRIAC dimming is the right choice for residential retrofit and very small commercial projects (<20 fixtures) where the simplicity of 2-wire installation outweighs its limitations. For B2B procurement above 20 fixtures: specify 0-10V or DALI instead. Key TRIAC requirements: (1) Always test the specific dimmer + driver combination before bulk ordering — compatibility lists from manufacturers are guidelines, not guarantees, (2) Specify 'trailing-edge' (ELV/reverse-phase) for LED — it's smoother and quieter than leading-edge, (3) Verify the driver's minimum AND maximum load ratings — TRIAC dimmers have minimum load requirements (typically 10-40W) that a single LED fixture may not meet.