White LED luminary light control system

• US 6,441,558 B1
• Filed: 12/07/2000
• Issued: 08/27/2002
• Est. Priority Date: 12/07/2000
• Status: Expired due to Term

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Koninklijke Philips Electronics N.V. (Koninklijke Philips N.V.)
• Inventors: Chang, Chin, Muthu, Subramanian, Bruning, Gert
• Primary Examiner(s): Wong, Don
• Assistant Examiner(s): Lee, Wilson
• Application Number:
  US09/732,197
• Publication Number:
  US 20020097000A1
• Time in Patent Office: 628 Days
• Field of Search: 315/149-159, 315/112-120, 315/291, 315/224, 315/307, 315/308
• US Class Current: 315/149
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback

Abstract

An LED luminary system for providing power to LED light sources to generate a desired light color comprises a power supply stage configured to provide a DC current signal. A light mixing circuit is coupled to said power supply stage and includes a plurality of LED light sources with red, green and blue colors to produce various desired lights with desired color temperatures. A controller system is coupled to the power supply stage and is configured to provide control signals to the power supply stage so as to maintain the DC current signal at a desired level for maintaining the desired light output. The controller system is further configured to estimate lumen output fractions associated with the LED light sources based on junction temperature of the LED light sources and chromaticity coordinates of the desired light to be generated at the light mixing circuit. The light mixing circuit further comprises a temperature sensor for measuring the temperature associated with the LED light sources and a light detector for measuring lumen output level of light generated by the LED light sources. Based on the temperatures measured, the controller system determines the amount of output lumen that each of the LED light sources need to generate in order to achieve the desired mixed light output, and the light detector in conjunction with a feedback loop maintains the required lumen output for each of the LED light sources.

Claims

1. An LED luminary system for providing power to LED light sources to generate a desired light color, said LED luminary system comprising:

a power supply stage configured to provide a DC current signal;

a light mixing circuit coupled to said power supply stage, said light mixing circuit having a plurality of LED light sources configured to receive said DC current signal; and

a controller system coupled to said power supply stage configured to provide control signals to said power supply stage so as to maintain said DC current signal at a desired level, said controller system further configured to respond to a temperature associated with said LED light sources and to estimate lumen output fractions associated with said LED light sources based on junction temperature of said LED light sources and chromaticity coordinates of said desired light color to be generated at said light mixing circuit.

2. The LED luminary system according to claim 1 wherein said light mixing circuit further comprises a plurality of red, green and blue LED light sources.

3. The LED luminary system according to claim 2, wherein said light mixing circuit further comprises a temperature sensor for measuring the temperature associated with said LED light sources and a light detector for measuring lumen output level of light generated by said LED light sources.

4. The LED luminary system according to claim 3 wherein said controller further comprises a memory table configured to store said lumen output fractions as a function of junction temperature of said LED light sources and chromaticity coordinates of said desired light color.

5. The LED luminary system according to claim 4, wherein said junction temperature of said LED light sources is measured based on forward voltage drop of said LED light source.

6. The LED luminary system according to claim 4, wherein said junction temperature of said LED light sources is measured based on current signal provided to said LED light sources, and lumen output level corresponding to said current signal.

7. The LED luminary system according to claim 6 wherein said junction temperature is measured by solving $\frac{I_{\mathrm{v2}}}{}$

(T2)Iv1

(T1)=If2If1



-(T1-T2)/T0

wherein I_v is lumen output of said LED light source at a specified temperature and I_f is current signal provided to said LED light source corresponding to said specified temperature.

8. In an LED luminary system a method for providing power to LED light sources to generate a desired light color, said method comprising the steps of:

generating a plurality of DC current signals;

providing said signals to a plurality of LED light sources to effect production of a desired light; and

responding to a temperature associated with said LED light sources and estimating lumen output fractions associated with said LED light sources based on junction temperature of said LED light sources and chromaticity coordinates of said desired light color to be generated by said plurality of LED light sources.

9. The method according to claim 8 wherein said step of estimating lumen output fractions further comprises the steps of:

estimating chromaticity coordinates of said LED light sources as a function of junction temperature of said LED light sources;

generating a plurality of lumen output fractions as a function of said junction temperature and chromaticity coordinates of a plurality of said desired light color levels; and

storing said lumen output fractions as a function of said junction temperature.

10. The method according claim 9 further comprising the step of providing a feedback control for maintaining said desired light color based on lumen levels of said LED light sources associated with said output lumen fractions.

11. The method according to claim 10 further comprises the step of measuring the temperature associated with said LED light sources and measuring lumen output level of light generated by said LED light sources.

12. The method according to claim 11 further comprising the step of estimating said junction temperature of said LED light sources based on forward voltage drop of said LED light source.

13. The method according to claim 11, further comprising the step of estimating said junction temperature of said LED light sources based on current signal provided to said LED light sources, and lumen output level corresponding to said current signal.

14. The method according to claim 13 wherein said step of estimating further comprises the step of solving $\frac{I_{\mathrm{v2}}}{}$

(T2)Iv1

(T1)=If2If1



-(T1-T2)/T0

wherein I_v is lumen output of said LED light source at a specified temperature and I_f is current signal provided to said LED light source corresponding to said specified temperature.