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Method and apparatus for sensing the color point of an RGB LED white luminary using photodiodes

  • US 6,630,801 B2
  • Filed: 10/22/2001
  • Issued: 10/07/2003
  • Est. Priority Date: 10/22/2001
  • Status: Expired due to Term
First Claim
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1. A method of controlling an LED luminary including red, green and blue (RGB) light emitting diodes (LEDs) driven by forward currents to produce a mixed color light comprising the steps of:

  • measuring an output signal of a filtered photodiode for each of the red, green and blue LEDs of the LED luminary;

    measuring an output signal of an unfiltered photodiode for each of the red, green and blue LEDs of the LED luminary;

    calculating a photodiode output signal ratio by dividing the output signal for the filtered photodiode with the output signal of the unfiltered photodiode for each of the red, green and blue LEDs;

    utilizing the photodiode output signal ratio to determine chromaticity coordinates for each of the red, green and blue LEDs; and

    adjusting the forward currents for each of the red, green and blue LEDs to produce a desired color light.

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