TECHNICAL NOTE6 MIN · 12 JUL 2026
When the dimmer buzzes, here's why it usually is
S
Siddharth V.
Lead Systems Engineer
Trailing edge, leading edge, minimum load and inrush current — the four variables behind almost every dimming complaint we receive.
That faint 50Hz hum emanating from a wall plate or acoustic ceiling fixture isn't a defect in the LED itself — it is physical coil vibration caused by steep dV/dt voltage spikes.
Leading Edge (TRIAC) vs Trailing Edge (ELV)
Leading-edge dimmers chop the front of the sinusoidal AC voltage curve, creating an abrupt electrical shockwave that resonates inside toroidal filter chokes.
Trailing-edge (reverse-phase) dimmers turn off gently at the zero-crossing, eliminating the high-frequency ringing that produces audible acoustic buzz and optical flicker.
Driver Compatibility ChecklistSPEC SHEET
- Preferred Protocol
- Trailing Edge (ELV) or DALI-2 Bus
- Minimum Circuit Load
- ≥ 10% of dimmer rated capacity
- Driver Modulation
- Hybrid Amplitude + 3.2kHz PWM
- Inrush Limiter
- NTC Thermistor or Active Soft-Start
Key Engineering Takeaways
- Specify trailing-edge electronic low voltage (ELV) dimmers instead of TRIAC for LED loads.
- Ensure the driver operates on amplitude modulation (CC) down to 5% before PWM kicks in.
- Always calculate aggregate inrush current when placing 10+ drivers on a single circuit.