Temperature Responsive Control For Lighting Apparatus Including Light Emitting Devices Providing Different Chromaticities And Related Methods

• US 20120280621A1
• Filed: 05/04/2011
• Published: 11/08/2012
• Est. Priority Date: 09/24/2009
• Status: Active Grant

• Current Assignee: IDEAL Industries Lighting, LLC (Ideal Industries Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Pickard, Paul K., Edmond, Mark D., Chobol, Joseph P.
• Granted Patent: US 8,901,845 B2
• Time in Patent Office: Days
• US Class Current: 315/122
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules

Abstract

A lighting apparatus may include a plurality of light emitting devices, a temperature sensor, and a compensation circuit. The plurality of light emitting devices may include a first light emitting device configured to emit light having a first chromaticity, a second light emitting device configured to emit light having a second chromaticity different than the first chromaticity, and a third light emitting device configured to emit light having the second chromaticity. Moreover, the first, second, and third light emitting devices may be electrically coupled in series. The temperature sensor may be configured to generate a temperature sense signal responsive to heat generated by at least one of the plurality of light emitting devices. The compensation circuit may be coupled to the third light emitting device, with the compensation circuit being configured to vary a level of electrical current through the third light emitting device relative to the electrical current through the first and second light emitting devices responsive to the temperature sense signal. Related methods are also discussed.

Claims

1. A lighting apparatus comprising:

a plurality of light emitting devices including a first light emitting device configured to emit light having a first chromaticity, a second light emitting device configured to emit light having a second chromaticity different than the first chromaticity, and a third light emitting device configured to emit light having the second chromaticity;

a temperature sensor configured to generate a temperature sense signal responsive to heat generated by at least one of the plurality of light emitting devices; and

a compensation circuit coupled to the third light emitting device wherein the compensation circuit is configured to vary a level of electrical current through the third light emitting device relative to an electrical current through the first and second light emitting devices responsive to the temperature sense signal.

2. The lighting apparatus of claim 1 wherein the compensation circuit is configured to provide that the level of the electrical current though the third light emitting device is at least ten percent of the electrical current through the first and second light emitting devices over a range of operating temperatures including a lowest operating temperature of no more than about 25 degrees C.

3. The lighting apparatus of claim 1 wherein the compensation circuit is configured to provide the level of the electrical current through the third light emitting device at a first percentage of the electrical current through the first and second light emitting devices responsive to a first temperature sense signal representing a first temperature, wherein the compensation circuit is configured to provide the level of the electrical current through the third light emitting device at a second percentage of the electrical current through the first and second light emitting devices different that the first percentage responsive to a second temperature sense signal representing a second temperature different than the first temperature.

4. The lighting apparatus of claim 3 wherein the first temperature is less than the second temperature and wherein the first percentage is less than the second percentage.

5. The lighting apparatus of claim 3 wherein the first temperature is between about 20 degrees C. and about 45 degrees C., wherein the second temperature is between about 55 degrees C. and about 100 degrees C., wherein the first percentage is in the range of about 0 percent to about 60 percent of the of the electrical current through the first and second light emitting devices, and wherein the second percentage is in the range of about 40 percent to about 100 percent of the electrical current through the first and second light emitting devices.

6. The lighting apparatus of claim 1 wherein the first, second, and third light emitting devices are electrically coupled in series, wherein the compensation circuit comprises a bypass circuit electrically coupled in parallel with the third light emitting device, wherein the bypass circuit is configured to vary the level of electrical current through the third light emitting device by varying a bypass current diverted from the third light emitting device responsive to the temperature of the lighting apparatus.

7. The lighting apparatus of claim 6 wherein the bypass circuit comprises a pulse width modulation circuit configured to vary a duty cycle of the bypass current responsive to the temperature of the lighting apparatus.

8. The lighting apparatus of claim 1 wherein the first light emitting device comprises a blue-shifted-yellow light emitting device, and wherein the second and third light emitting devices comprise red light emitting devices.

9. The lighting apparatus of claim 1 further comprising:

a lighting panel with the plurality of light emitting devices oriented on the lighting panel; and

a directed beam optic system spaced apart from the lighting panel, wherein the plurality of light emitting devices are oriented to emit light through the directed beam optic system to provide a Full-Width-at Half-Maximum opening cone angle of no more than about 60 degrees.

10. The lighting apparatus of claim 1 further comprising:

a lighting panel with the plurality of light emitting devices oriented on the lighting panel; and

an optical diffuser spaced apart from the lighting panel, wherein the plurality of light emitting devices are oriented to emit light through the optical diffuser to provide a diffuse light output.

11. The lighting apparatus of claim 1 wherein the compensation circuit is configured to set the level of electrical current through the third light emitting device at a first level responsive to a first temperature that causes the combination of light emitted by the plurality of light emitting devices to have a first color point, and wherein the compensation circuit is configured to set the level of electrical current through the third light emitting device at a second level responsive to a second temperature that causes the combination of light emitted by the plurality of light emitting devices to have a second color point different than the first color point.

12. The lighting apparatus of claim 11 wherein the first temperature is less than the second temperature, and wherein the first color point is redder than the second color point.

13. A lighting apparatus comprising:

a plurality of light emitting devices including a first light emitting device configured to emit light having a first chromaticity and a second light emitting device configured to emit light having a second chromaticity different than the first chromaticity, wherein the plurality of light emitting devices are oriented to combine the light emitted thereby to provide a combined optical output;

a temperature sensor configured to generate a temperature sense signal responsive to heat generated by at least one of the plurality of light emitting devices; and

a compensation circuit coupled to the second light emitting device, wherein the compensation circuit is configured to vary an electrical current passing through the second light emitting device responsive to the temperature sense signal, wherein the compensation circuit is configured to set a first level of current passing through the second light emitting device so that the combined optical output has a first color point responsive to a first temperature sense signal representing a first temperature, and wherein the compensation circuit is configured to set a second level of current passing through the second light emitting device different than the first level so that the combined optical output has a second color point different than the first color point responsive to a second temperature sense signal representing a second temperature greater than the first temperature wherein the first color point is redder than the second color point.

14. The lighting apparatus of claim 13 wherein the first light emitting device comprises a blue-shifted-yellow light emitting device and the second light emitting device comprises a red light emitting device.

15. The lighting apparatus of claim 13 wherein the compensation circuit is configured to cause the second light emitting device to emit at least some light having the second chromaticity over a range of operating temperatures including a lowest operating temperature of no more than about 25 degrees C.

16. The lighting apparatus of claim 13 further comprising:

a lighting panel with the plurality of light emitting devices oriented on the lighting panel; and

a directed beam optic system spaced apart from the lighting panel, wherein the plurality of light emitting devices are oriented to emit light through the directed beam optic system to provide a Full-Width-at Half-Maximum opening cone angle of no more than about 60 degrees.

17. The lighting apparatus of claim 13 further comprising:

a lighting panel with the plurality of light emitting devices oriented on the lighting panel; and

an optical diffuser spaced apart from the lighting panel, wherein the plurality of light emitting devices are oriented to emit light through the optical diffuser to provide a diffuse light output.

18. The lighting apparatus of claim 13 wherein the compensation circuit is configured to maintain a shift in color of the combined optical output of no more than about 0.007 delta in a u′

v′

chromaticity space over a range of operating temperatures from 30 degrees C. to 75 degrees C.

19. The lighting apparatus of claim 13 wherein combined optical output falls within a ten-step MacAdam ellipse of a point on the black body planckian locus when the lighting apparatus is operated at a full current steady state temperature.

20. The lighting apparatus of claim 13 wherein the plurality of light emitting devices comprises a third light emitting device having the second chromaticity, wherein the first, second, and third light emitting devices are electrically coupled in series, and wherein the compensation circuit is configured to vary a level of electrical current through the third light emitting device relative to the electrical current through the first and second light emitting devices responsive to the temperature sense signal.

21. The lighting apparatus of claim 20 wherein the compensation circuit is configured to provide that the level of the electrical current though the third light emitting device is at least ten percent of the electrical current through the first and second light emitting devices over a range of operating temperatures including a lowest operating temperature of no more than about 25 degrees C.

22. The lighting apparatus of claim 20 wherein the compensation circuit comprises a bypass circuit electrically coupled in parallel with the third light emitting device, wherein the bypass circuit is configured to vary the level of electrical current through the third light emitting device by varying a bypass current diverted from the third light emitting device responsive to the temperature sense signal.

23. The lighting apparatus of claim 22 wherein the bypass circuit comprises a pulse width modulation circuit configured to vary a duty cycle of the bypass current responsive to the temperature sense signal.

24. A method of operating a lighting apparatus including a plurality of light emitting devices including a first light emitting device configured to emit light having a first chromaticity, a second light emitting device configured to emit light having a second chromaticity different than the first chromaticity, and a third light emitting device configured to emit light having the second chromaticity, the method comprising:

varying a level of electrical current through the third light emitting device relative to the electrical current through the first and second light emitting devices responsive to a temperature of the lighting apparatus.

25. The method of claim 24 wherein varying the level of electrical current comprises providing that the level of the electrical current though the third light emitting device is at least ten percent of the electrical current through the first and second light emitting devices over a range of operating temperatures including a lowest operating temperature of no more than about 25 degrees C.

26. A method of operating a lighting apparatus including a plurality of light emitting devices including a first light emitting device configured to emit light having a first chromaticity and a second light emitting device configured to emit light having a second chromaticity different than the first chromaticity, wherein the plurality of light emitting devices are oriented to combine the light emitted thereby to provide a combined optical output, the method comprising:

setting a first level of current passing through the second light emitting device so that the combined optical output has a first color responsive to a first temperature of the lighting apparatus; and

setting a second level of current passing through the second light emitting device different than the first level so that the combined optical output has a second color responsive to a second temperature of the lighting apparatus greater than the first temperature, wherein the first color is redder than the second color.

27. The method of claim 26 further comprising:

maintaining at least some emission of light having the second chromaticity from the second light emitting device over a range of operating temperatures including a lowest operating temperature of no more than about 25 degrees C.