Lifetime correction for aging of LEDs in tunable-white LED lighting devices
First Claim
1. A method for controlling a multi-color lighting system for combining light from multiple solid state light sources of the system, each configured for producing light of a different color characteristic, each light source comprising one or more light emitting diodes (LEDs), the method comprising the steps of:
- for a period of operation, selectively controlling drive currents supplied to the LEDs of the multiple solid state light sources to produce a combined light output of overall color characteristic and intensity corresponding to a user input selection based in part on determined output characteristics of the LEDs of the multiple solid state light sources;
after the period of operation, obtaining updated output characteristics of the LEDs of the multiple solid state light sources by;
driving one or more LEDs configured for producing light of a first color characteristic, while LEDs configured for producing light of different color characteristics than the first color characteristic are turned OFF, and measuring a level of the light of the first color characteristic with a photosensor;
driving one or more LEDs configured for producing light of a second color characteristic, while LEDs configured for producing light of different color characteristics than the second color characteristic are turned OFF, and measuring a level of the light of the second color characteristic with the photosensor;
driving one or more LEDs configured for producing light of a third color characteristic, while LEDs configured for producing light of different color characteristics than the third color characteristic are turned OFF, and measuring a level of the light of the third color characteristic with the photosensor; and
processing the measured levels of the light of the first, second and third color characteristics to obtain updated output characteristics of the LEDs of the multiple solid state light sources; and
selectively controlling drive currents supplied to the LEDs of the multiple solid state light sources to produce combined light output of an overall color characteristic corresponding to a user input selection, based in part on the updated determined output characteristics of the LEDs of the multiple solid state light sources, wherein the step of selectively controlling the drive currents based in part on the updated determined output characteristics includes;
correcting changes in performance of the LEDs of the multiple solid state light sources, after the period of operation of the multi-color lighting system.
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Abstract
A lighting system having at least three light sources receives an input relating to color coordinates of a target point representing a desired color characteristic for a combined output from the light sources. The system provides color tunable output and/or dimmable output in response to differences in user input. The system also corrects changes in performance of the light sources due to lifetime degradation in each of the light sources. After a period of system operation, outputs of the sources are measured. The system increases the luminosity outputs of each of the light sources by a respective amount relative to the degradations measured in all the light sources; in this manner, the luminosity outputs of the light sources remain substantially constant in relations to each other over the lifetime of the light sources.
45 Citations
20 Claims
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1. A method for controlling a multi-color lighting system for combining light from multiple solid state light sources of the system, each configured for producing light of a different color characteristic, each light source comprising one or more light emitting diodes (LEDs), the method comprising the steps of:
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for a period of operation, selectively controlling drive currents supplied to the LEDs of the multiple solid state light sources to produce a combined light output of overall color characteristic and intensity corresponding to a user input selection based in part on determined output characteristics of the LEDs of the multiple solid state light sources; after the period of operation, obtaining updated output characteristics of the LEDs of the multiple solid state light sources by; driving one or more LEDs configured for producing light of a first color characteristic, while LEDs configured for producing light of different color characteristics than the first color characteristic are turned OFF, and measuring a level of the light of the first color characteristic with a photosensor; driving one or more LEDs configured for producing light of a second color characteristic, while LEDs configured for producing light of different color characteristics than the second color characteristic are turned OFF, and measuring a level of the light of the second color characteristic with the photosensor; driving one or more LEDs configured for producing light of a third color characteristic, while LEDs configured for producing light of different color characteristics than the third color characteristic are turned OFF, and measuring a level of the light of the third color characteristic with the photosensor; and processing the measured levels of the light of the first, second and third color characteristics to obtain updated output characteristics of the LEDs of the multiple solid state light sources; and selectively controlling drive currents supplied to the LEDs of the multiple solid state light sources to produce combined light output of an overall color characteristic corresponding to a user input selection, based in part on the updated determined output characteristics of the LEDs of the multiple solid state light sources, wherein the step of selectively controlling the drive currents based in part on the updated determined output characteristics includes; correcting changes in performance of the LEDs of the multiple solid state light sources, after the period of operation of the multi-color lighting system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. A lighting system comprising:
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at least three light sources each for producing light of a different one of at least three colors, each light source including one or more light emitting diodes (LEDs); an input; a photosensor; and a controller responsive to information received via the input and coupled to control the at least three light sources to produce a combined light output of the system, wherein the controller is configured to control functions of the lighting system, including functions to; for a period of operation of the lighting system, selectively control drive currents supplied to the LEDs of the at least three light sources to produce combined light output of an overall color characteristic corresponding to a user input selection, based in part on determined output characteristics of the LEDs of the at least three light sources; after the period of operation of the lighting system, obtain updated output characteristics of the LEDs of the at least three light sources by functions to; drive one or more LEDs configured for producing light of a first of the at least three color characteristics, while LEDs configured for producing light other than the first color characteristic are turned OFF, and measure a level of the light of the first color characteristic with the photosensor; drive one or more LEDs configured for producing light of a second of the at least three color characteristics, while LEDs configured for producing light other than the second color characteristic are turned OFF, and measure a level of the light of the second color characteristic with the photosensor; drive one or more LEDs configured for producing light of a third of the at least three color characteristics, while LEDs configured for producing light other than the third color characteristic are turned OFF, and measure a level of the light of the third color characteristic with the photosensor; and process the measured levels of the light of the first, second and third color characteristics to obtain the updated output characteristics of the LEDs of the at least three light sources; selectively control drive currents supplied to the LEDs of the three light sources to produce a combined light output of an overall color characteristic corresponding to a user input selection, based in part on the updated output characteristics of the LEDs of the three light sources; determine a relative amount of change in each of the three levels of light, after the period of operation, in which the relative amount of change is measured between (a) an initial time during the period of operation and (b) a final time after the period of operation; determine the smallest relative amount of change among the first, second, and third color characteristics; and increase the drive current supplied to the one or more LEDs configured for producing a respective first, second, or third color characteristic by the difference between (a) the smallest relative amount of change and (b) the relative amount of change determined in the respective first, second, or third color characteristic. - View Dependent Claims (11, 12, 13, 14, 15)
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10. A lighting system comprising:
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at least three light sources each for producing light of a different one of at least three colors, each light source including one or more light emitting diodes (LEDs); an input; a photosensor; and a controller responsive to information received via the input and coupled to control the at least three light sources to produce a combined light output of the system, wherein the controller is configured to control functions of the lighting system, including functions to; for a period of operation of the lighting system, selectively control drive currents supplied to the LEDs of the at least three light sources to produce combined light output of an overall color characteristic corresponding to a user input selection, based in part on determined output characteristics of the LEDs of the at least three light sources; after the period of operation of the lighting system, obtain updated output characteristics of the LEDs of the at least three light sources by functions to; drive one or more LEDs configured for producing light of a first of the at least three color characteristics, while LEDs configured for producing light other than the first color characteristic are turned OFF, and measure a level of the light of the first color characteristic with the photosensor; drive one or more LEDs configured for producing light of a second of the at least three color characteristics, while LEDs configured for producing light other than the second color characteristic are turned OFF, and measure a level of the light of the second color characteristic with the photosensor; drive one or more LEDs configured for producing light of a third of the at least three color characteristics, while LEDs configured for producing light other than the third color characteristic are turned OFF, and measure a level of the light of the third color characteristic with the photosensor; and process the measured levels of the light of the first, second and third color characteristics to obtain the updated output characteristics of the LEDs of the at least three light sources; selectively control drive currents supplied to the LEDs of the three light sources to produce a combined light output of an overall color characteristic corresponding to a user input selection, based in part on the updated output characteristics of the LEDs of the three light sources; determine each of the three levels of light, at an initial time during the period of operation; determine a respective amount of change for each of the three levels of light, at a final time after the period of operation; and increasing the drive current supplied to the one or more LEDs configured for producing a respective first, second, or third color characteristic by the respective amount of change. - View Dependent Claims (16, 17, 18, 19, 20)
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Specification