How TRIAC Dimmers Work

Working principle of TRIAC dimmer (forward phase control dimmer)

• The RC circuit connecting R1, R2 and C1 delays the start of the TRIAC dimmer until the voltage of C1
rises to the trigger voltage of the AC diode (Diac).
• The higher the resistance of the potentiometer (the further the slider moves down), the longer the start delay time. This shortens
the "on time" of the TRIAC dimmer or reduces its "conduction angle" (θ).
The average power supplied to the load is reduced.

TRIAC Dimmer Holding Current

A holding current (IH) must be continuously supplied to ensure that the circuit is always in the "on" state