Monday, February 14, 2011

White Light Led Driver With Gradual Dimming

 

Many consumer products using white light LEDs for illumination and backlighting provide gradual LED illumination at turnon and turnoff. This gradual illumination is usually achieved with the aid of a Microprocessor that provides PWM dimming control. This circuit uses the Texas Instruments TPS61040 white light LED Driver to provide gradual illumination at turnon and turnoff without the use of a Microprocessor 

The following circuit generates a 101mA constant current to drive up to 6 white LEDs for portable applications such PDAs and digital cameras. The input operating range is 1.8 V to 6 V, which covers two-cell alkaline and NiMh inputs (1.8 V to ~3 V), three-cell alkaline and NiMh inputs (2.7 V to ~4.8 V), and single-cell Li-Ion inputs (3 V~4.2 V). This boost converter uses R1 to set a constant current through the LEDs A detailed description of this circuit CAN be found in the TPS61040 data sheet ( SLVS413 ).

            TPS61040 Constant Current LED Drive Supply
TPS61040 Constant Current LED Drive Supply

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