LED controller with constant power regulation provides smooth, flicker-free dimming

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By eeNews Europe

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, including A19, E26/27 and PAR30/38 bulbs, as well as can light retrofits.

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. Conversely, 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. The result is up to 10-percent improvement in efficacy across the expected operating temperature range of the fixture.

The LM3447 joins TI’s portfolio of off-line LED lighting controllers that include the National LM3445, the industry’s first phase-dimmable LED driver with constant current control, and the TPS92310 primary side regulator for non-dimming applications.

The LM3447 LED driver’s integrated phase dimmer decoding and dimmer detection circuitry allows for easy design and highest efficiency.  The device operates with leading edge (TRIAC) and trailing edge dimmers and offers primary side control which supports isolated lighting designs without opto-couplers.

The LM3447 features a fixed frequency discontinuous conduction mode flyback topology with valley switching simplifies EMI filter design and greater than 0.9 power factor correction meets all regulatory requirements.

Thermal fold-back protects LED array from over-temperature while still providing reduced light output.

Availability and Pricing

The LM3447 is available in volume now from TI and its authorized distributors. Offered in a 14-pin TSSOP package, the suggested retail price is $1.15 in 1,000-unit quantities.

More information about the LM3447 LED at

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