TRIAC Dimming, also known as phase-cut or leading-edge dimming, is a widely used analog dimming method in LED power supplies that is fully backward-compatible with traditional TRIAC (Triode for Alternating Current) wall dimmers originally designed for incandescent lamps. It works by chopping the leading portion of the AC sine wave at a variable phase angle (typically 0°–180°), reducing the RMS voltage delivered to the driver. The LED driver's internal circuitry detects this chopped waveform, interprets the phase angle, and proportionally adjusts the output current or PWM duty cycle to dim the LEDs smoothly from 100% down to as low as 5–10% brightness.
This type is ideal for residential retrofits, hotels, and commercial spaces where existing wiring and TRIAC dimmer switches are already installed-no additional control wires are required. Advantages include low cost, simplicity, and broad compatibility with legacy infrastructure. However, challenges exist: poor compatibility can cause flickering, buzzing, or limited dimming range; some drivers need a minimum load or special "TRIAC-dimmable" circuitry to stabilize performance. It also generates more EMI than digital methods (0-10V or DALI).
Modern TRIAC-dimmable LED drivers incorporate active filtering, deep-dimming algorithms, and soft-start features to minimize issues. They are most suitable for non-critical, cost-sensitive applications where easy installation and universal dimmer support matter more than precision or flicker-free operation at very low levels.
