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

DETAILED DESCRIPTION It is an object of the present invention to overcome disadvantages of the prior art systems and methods of controlling an RGB based LED luminary.
In accordance with one form of the present invention, 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 includes 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 the 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.
In accordance with another form of the present invention, a control system for an LED luminary including red, green and blue (RGB) light emitting diodes (LEDs) driven by forward currents to produce a mixed color-light includes: a feedback unit which generates feedback values representative of the mixed color light produced by said LED luminary, said feedback values corresponding to output signals of a photodiode; and a controller which acquires a difference between said feedback values and reference values representative of a desired mixed color light, said controller adjusting said forward currents in accordance with said difference.
These and other objects, features and advantages of the present invention will become apparent from the following detailed description of illustrative embodiments, which is to be read in connection with the accompanying drawings.