LED luminaire with electrically adjusted color balance using photodetector
First Claim
1. A luminaire comprising:
- an array of LEDs comprising at least one LED in each of a plurality of colors;
Means for supplying electrical current to said LEDs in each said color, said electrical current including a measuring drive pulse having a measuring period that comprises a “
turn off”
portion, said LEDs in each said color having a light output, such that said light output has a nominal continuous value during ordinary operation and is interrupted during said “
turn off”
portion, and the array having a combined light output when current is supplied to all of the LEDs in the array;
a photodiode arranged to measure the light outputs of at least one of the LEDs in the array; and
means for selectively turning off the electrical current to one of said LEDs so that said photodiode measures the light output for each color separately in response to said measuring drive pulse.
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Accused Products
Abstract
The combined light output (chromaticity) of a white light emitting LED luminaire is electronically controlled based on measurements by a single photodiode arranged to measure the light outputs of at least a plurality of the LEDs in the array. This is accomplished by measuring the light output of the LEDs in each color separately in a sequence of time pulses. For an array of red, green, and blue LEDs there are three time pulses in a measuring sequence. During each time pulse, the current for the color being measured is turned off. The response time of a typical photodiode is extremely short, so the measuring sequence can be performed in a sufficiently short time that an-observer will not detect it (e.g. 10 ms). Measured light outputs for the colors are compared to desired outputs, which may be set by user controls, and changes to the power supply for the color blocks are made as necessary. Chromaticity is thus automatically controlled without regard to the factors which may cause it to change. The user inputs permit varying the desired chromaticity to either warm white (more red output) or cool white (more blue output).
528 Citations
24 Claims
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1. A luminaire comprising:
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an array of LEDs comprising at least one LED in each of a plurality of colors;
Means for supplying electrical current to said LEDs in each said color, said electrical current including a measuring drive pulse having a measuring period that comprises a “
turn off”
portion, said LEDs in each said color having a light output, such that said light output has a nominal continuous value during ordinary operation and is interrupted during said “
turn off”
portion, and the array having a combined light output when current is supplied to all of the LEDs in the array;
a photodiode arranged to measure the light outputs of at least one of the LEDs in the array; and
means for selectively turning off the electrical current to one of said LEDs so that said photodiode measures the light output for each color separately in response to said measuring drive pulse. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A method for reducing flicker while driving an array of LEDs comprising at least one LED in each of a plurality of colors in a luminaire comprising the steps of:
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supplying electrical current to said LEDs in each said color, such that said LEDs have a light output with a nominal continuous value during ordinary operation;
measuring a first light level of said LEDs;
turning off said electrical current to one of said LEDs;
measuring a second light level of remaining current supplied said LEDs;
determining the light output of the one of said LEDs by determining the difference between the first light level and the second light level. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24)
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Specification