Phase-Dimmable LED Driver

Texas Instruments (Dallas, TX) has introduced a new LED controller with constant power regulation. The LM3447 AC/DC LED driver includes a dimmer detect, phase decoder and adjustable hold current circuits to provide smooth and flicker-free dimming operation in off-line, isolated LED lighting applications.

Traditional drivers use constant current control to accurately regulate LED forward current. This approach produces consistent light output or intensity from LEDs in the same bin. However, once current is applied to the LED, its solder point temperature rises, leading to a decrease in forward voltage and a drop in efficacy. By using the new LM3447 with constant power regulation, the LED forward voltage droop over temperature is offset by an increase in LED current to maintain constant LED power.