TRIAC LED Driver Packs Full-Range, Flicker-Free Dimming

Promising to extend LED life via a patent-pending control architecture, the LM3445 TRIode for alternating current (TRIAC) dimmable LED driver enables off-line, uniform flicker-free dimming of high-brightness LEDs with a conventional TRIAC forward or reverse phase-control wall dimmer. It allows for a full 100:1 range of dimming and can maintain greater than 1A of constant current to large strings of LEDs. It also allows master-slave operation, enabling control of multiple strings of LED bulbs. Residing in a 10-pin mini SOIC package, the device is an adaptive constant off-time ac/dc buck constant current controller that includes a TRIAC dimming decoder. It includes a bleeder circuit to ensure proper TRIAC operation by allowing current flow while the line voltage is low to enable proper firing of the TRIAC. A passive power factor correction circuit ensures reliable power factor by drawing current directly from the line for most of the cycle and provides a constant positive voltage to the buck regulator. Additional features include thermal shutdown, current limit, and under-voltage lockout. The LM3445 is available now for $1.75 each/1,000. NATIONAL SEMICONDUCTOR CORP., Santa Clara, CA. (800) 272-9959.