What is triac dimming?

TRIAC dimming is one of the most widely used and longest-standing dimming methods. It is commonly found in incandescent and TRIAC-compatible LED lights in homes, hotels, and other places.

Principle:

Core component: TRIAC (Thyristor)

A TRIAC is a semiconductor device that can be regarded as an "electronic switch". Its key characteristic is that once triggered to conduct, it will remain on until the current passing through it drops below its holding current. This feature forms the basis for dimming.

Control mode: Phase-Cutting

AC power is a sine wave, with positive and negative half cycles. A silicon-controlled rectifier dimmer works by controlling the moment when the current starts to flow in each half cycle (i.e., the trigger angle).

Non-dimming (full brightness): The thyristor is triggered almost immediately after the voltage crosses zero, allowing the current to flow smoothly throughout the entire half-cycle, and the lamp receives almost all the energy.

Dimming (Dimming down): The dimmer will delay the triggering of the thyristor. For instance, it will trigger it only when the voltage is close to its peak. As a result, a portion of the voltage and current in each half-cycle is "cut off" and cannot be delivered to the lamp.

The later the trigger occurs, the more waveform parts will be cut off, the less energy will be delivered to the lamp, and the dimmer the light will be.

Requirements for the lamp end:

Traditional incandescent lamps are purely resistive loads and can directly work with this chopped waveform. However, for LED lamps, there must be a dedicated thyristor dimming driver power supply inside. This driver power supply will "interpret" the chopped waveform, identify how much has been cut off, and then adjust the current output to the LED lamp beads accordingly, thereby achieving a linear change in brightness.

Advantages:

Strong compatibility: Directly compatible with the vast majority of traditional wall dimmer switches (designed for incandescent bulbs), no need to replace the wiring.

Low cost: The technology is mature, the industrial chain is complete, and it has a cost advantage.

No additional wiring required: Usually only two wires (live wire and neutral wire) are needed, consistent with the wiring of ordinary switches.

Disadvantages:

Minimum load requirement: Many silicon-controlled rectifier (SCR) dimmers have a minimum power requirement (such as 25W). When connected to low-power LED lights, they may not function properly (resulting in flickering, inability to turn off, or a limited dimming range).

Compatibility issues: Not all LED lights are perfectly compatible with all dimmers, and problems such as noise, flickering, and dead zones (sudden turning off only when dimmed to the last segment) may occur.

The efficiency is slightly lower: As the waveform is cut, some harmonics will be generated, causing minor pollution to the power grid. The efficiency is not as good as that of 0-10V dimming.

Main applications:

Residential, restaurant, hotel room and other retrofit markets, as well as scenarios requiring replacement of traditional incandescent dimming systems.