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US 7,119,498 B2Granted
Current control device for driving LED devices
AssigneeTexas Instruments Incorporated
InventorsDavid J. Baldwin, Sanmukh Patel
Life of this patent
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Abstract
A current control device for driving LED devices uses a switched-mode current control loop inside of an output intensity low-frequency pulse width modulation (PWM) control loop. This allows separate control of current level (for accurate light wavelength output) and light intensity. The current control device requires only one switch to regulate current level, and no other switches for the intensity control. This allows lower parts count for greater reliability and lower system cost.
Claims10
A device for driving light emitting diodes comprising:
- an integrator coupled to a first LED current node;
- a comparator having a first input coupled to the integrator;
- an oscillator coupled to a second input of the comparator;
- a control device having a first input coupled to the comparator and for providing a hysteretic pulse width modulated signal on an output node of the control device;
- a temperature control device coupled to a second input of the control device for setting a value for LED current deration with increase in ambient temperature;
- a driver having an input coupled to the output of the control device;
- a driver transistor having a control node coupled to an output of the driver;
- and
- an inductor coupled between the driver transistor and a second LED current node.
6 more elements
Dependencies are inferred from the claim text.