Triacs are bidirectional ac switches that can control loads with currents as high as 25A rms at voltages as high as 600V. They find wide use in motor-speed, heater, and incandescent-lamp controls.

Non-insulated power supplies are often required when a power semiconductor, which has to be controlled using this supply, has its drive reference connected to the mains (line or neutral terminal).

The LM3445 from National Semiconductor enables a full 100:1 range of offline, uniform, flicker-free dimming for high-brightness LEDs with a conventional TRIAC forward or reverse phase-control wall ...