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.
An integrated phase dimmer decoding and dimmer detection circuitry allows for easy design and highest efficiency. The LM3447 LED driver operates with leading edge (TRIAC) and trailing edge dimmers and primary side control supports isolated lighting designs without opto-couplers.
Constant power LED load regulation improves efficacy of LED array by compensating for LED junction temperature changes, while fixed frequency discontinuous conduction mode flyback topology with valley switching simplifies EMI filter design. A greater than 0.9 power factor correction meets all regulatory requirements and thermal fold-back protects LED array from over-temperature while still providing reduced light output. LED open- and short-circuit protection and driver IC thermal shutdown protect lamp electronics from damage during fault conditions.
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 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.