Adaptive algorithm for camera flash LED power control vs. battery impedance, state of discharge (SOD), aging, temperature effects
First Claim
1. A method for driving a light-emitting semiconductor, the method comprising:
- converting a supply voltage into a secondary output voltage for supplying the light-emitting semiconductor with an output voltage and an output current during a high current phase;
sensing a level for the supply voltage at the beginning of the high current phase of the light-emitting semiconductor;
determining a threshold voltage level for the supply voltage level based on the sensed level;
starting the high current phase with the light-emitting semiconductor;
continuously comparing the sensed level with the threshold voltage level; and
controlling the output current through the light-emitting semiconductor such that the sensed level does not drop below the threshold voltage level.
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Abstract
A method for driving a light-emitting semiconductor is provided. A supply voltage is converted into a secondary output voltage for supplying the light-emitting semiconductor with an output voltage. A level for the supply voltage at the beginning of a high current phase of the light-emitting semiconductor is sensed. A threshold voltage level for the supply voltage level is determined based on the sensed level. The high current phase with the light-emitting semiconductor is stated. The sensed level is continuously compared with the threshold voltage level, and an output current through the light-emitting semiconductor is controlled such that the sensed level does not drop below the threshold voltage level.
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Citations
15 Claims
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1. A method for driving a light-emitting semiconductor, the method comprising:
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converting a supply voltage into a secondary output voltage for supplying the light-emitting semiconductor with an output voltage and an output current during a high current phase; sensing a level for the supply voltage at the beginning of the high current phase of the light-emitting semiconductor; determining a threshold voltage level for the supply voltage level based on the sensed level; starting the high current phase with the light-emitting semiconductor; continuously comparing the sensed level with the threshold voltage level; and controlling the output current through the light-emitting semiconductor such that the sensed level does not drop below the threshold voltage level. - View Dependent Claims (2, 3, 4)
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5. An apparatus comprising:
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a plurality of light emitters; a driver that receives a supply voltage and outputs a secondary voltage and an output current to each of a plurality of outputs paths during a high current phase, wherein each output path includes at least one of the light emitters; a current regulator coupled to each output path, wherein the current regulator is adapted to determine the output current through each output path; and a controller that is coupled to the driver, the current regulator, and the output paths, wherein the controller includes; a comparator that compares the supply voltage to a threshold voltage during the high current phase; and control logic that determines the threshold voltage level at the beginning of the high current phase and that controls the output current through each of the light-emitters during the high current phase such that the supply voltage does not fall below the threshold voltage level. - View Dependent Claims (6, 7, 8, 9, 10, 11)
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12. An apparatus for driving a light-emitting semiconductor, the apparatus comprising:
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means for converting a supply voltage into a secondary output voltage for supplying the light-emitting semiconductor with an output voltage and an output current during a high current phase; means for sensing a level for the supply voltage at the beginning of the high current phase of the light-emitting semiconductor; means for determining a threshold voltage level for the supply voltage level based on the sensed level; means for starting the high current phase with the light-emitting semiconductor; means for continuously comparing the sensed level with the threshold voltage level; and means for controlling the output current through the light-emitting semiconductor such that the sensed level does not drop below the threshold voltage level. - View Dependent Claims (13, 14, 15)
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Specification