SYSTEMS AND METHODS FOR CONTROLLING SOLID STATE LIGHTING DEVICES AND LIGHTING APPARATUS INCORPORATING SUCH SYSTEMS AND/OR METHODS

• US 20120306375A1
• Filed: 06/03/2011
• Published: 12/06/2012
• Est. Priority Date: 06/03/2011
• Status: Active Grant

• Current Assignee: IDEAL Industries Lighting, LLC (Ideal Industries Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: van de Ven, Antony P.
• Granted Patent: US 10,178,723 B2
• Time in Patent Office: Days
• US Class Current: 315/122
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/3577 Emulating the dimming characteristics, brightness or colour temperature of incandescent lamps
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices

Abstract

A lighting apparatus includes at least two sets of light-emitting devices with overlapping spectra and different chromaticities, such as two sets of blue-shifted yellow (BSY) LEDs producing outputs with different yellow content. The devices may be selectively controlled, e.g., by using selective current bypass circuits, to provide a desired color temperature or other visual performance in response to a dimming control input such that, for example, a light output approximating that of an incandescent lamp may be achieved.

Claims

1. A lighting apparatus comprising:

a string of serially-connected light-emitting diodes (LEDs) coupled between first and second terminals and comprising a first set of LEDs having a first chromaticity and a second set of LEDs having a second chromaticity different from the first chromaticity; and

a control circuit operatively coupled to the string and configured to vary a color temperature produced by the string responsive to a variation in a total current passing between the first and second terminals.

2. The apparatus of claim 1, wherein the control circuit is configured to differentially vary current passing through the first and second sets of LEDs responsive to the total current such that the color temperature varies as the total current varies.

3. The apparatus of claim 2, wherein the control circuit comprises a bypass circuit configured to differentially bypass current around the first set of light-devices with respect to the second set responsive to the total current.

4. The apparatus of claim 3, wherein the bypass circuit is configured to differentially bypass current around the first set of LEDs with respect to the second set of LEDs responsive to the total current such that the color temperature decreases as the total current decreases.

5. The apparatus of claim 3, wherein the bypass circuit comprises at least one resistor coupled in parallel with at least one LED of the first set of LEDs.

6. The apparatus of claim 3, wherein the bypass circuit comprises a variable resistance circuit.

7. The apparatus of claim 3, wherein the bypass circuit comprises a switching circuit.

8. The apparatus of claim 1, wherein the first set of LEDs comprises a first set of blue-shifted yellow (BSY) LEDs, wherein the second set of LEDs comprises a second set of BSY LEDs.

9. The apparatus of claim 8, wherein the string further comprises a set of red LEDs coupled in series with the first and second sets of BSY LEDs.

10. The apparatus of claim 1, wherein the control circuit is further configured to control the total current responsive to a dimmer control input signal.

11. The apparatus of claim 1, wherein the control circuit is configured to conform the color temperature to the Planckian locus.

12. The apparatus of claim 1, wherein the control circuit is configured to conform the color temperature to within at least a 10 step MacAdam ellipse of the Planckian locus.

13. The apparatus of claim 1, wherein the control circuit is configured to conform the color temperature to within at least a 7 step MacAdam ellipse of the Planckian locus.

14. The apparatus of claim 1, wherein the control circuit is configured to conform the color temperature within at least a 5 step MacAdam ellipse of the Planckian locus.

15. The apparatus of claim 1, wherein the control circuit is configured to cause a color temperature produced by the plurality of LEDs to vary in response to the total current over a range from about 3500K to about 1800K while maintaining a color rendering index (CRI) greater than about 80%.

16. The apparatus of claim 15, wherein the control circuit and the plurality of LEDs are configured to maintain a CRI greater than about 90% for brightness levels between a maximum brightness level and about 5% of the maximum brightness level.

17. The apparatus of claim 1, wherein the control circuit is configured to provide a substantially fixed color temperature over a first range of the total current and to conform the color temperature to the Planckian locus over a second range of the total current and to.

18. The apparatus of claim 17, wherein the first range of total current corresponds to a range of brightness levels between a maximum brightness level and about 5% of the maximum brightness level.

19. A lighting apparatus comprising:

a plurality of light-emitting devices comprising at least one red light-emitting device, at least one BSY light-emitting device having a first BSY output and at least one BSY light-emitting device having a second BSY output with a greater yellow content than the first BSY output; and

a control circuit operatively coupled to the plurality of light-emitting devices and configured to cause a color temperature produced by the plurality of light-emitting devices to vary substantially in conformance with the Planckian locus in response to a dimming control input.

20. The apparatus of claim 19, wherein the control circuit is configured to conform the color temperature to within at least a 10 step MacAdam ellipse of the Planckian locus.

21. The apparatus of claim 19, wherein the control circuit is configured to conform the color temperature to within at least a 7 step MacAdam ellipse of the Planckian locus.

22. The apparatus of claim 19, wherein the control circuit is configured to conform the color temperature to within at least a 5 step MacAdam ellipse of the Planckian locus.

23. The apparatus of claim 19, wherein the control circuit is configured to preferentially decrease a current through the at least one light BSY light-emitting device having the first BSY output in comparison to a current through the at least one BSY light-emitting device having the second BSY output responsive to the dimming control input commanding a decrease in brightness.

24. The apparatus of claim 19, wherein the control circuit is configured to cause a color temperature produced by the plurality of light-emitting devices to vary in response to the dimming control input over a range from about 3000 K to about 1800 K while maintaining a color rendering index (CRI) greater than about 80%.

25. The apparatus of claim 24, wherein the control circuit and the plurality of light-emitting devices are configured to maintain a CRI greater than about 90% for brightness levels between a maximum brightness level and about 5% of the maximum brightness level.

26. The apparatus of claim 19:

wherein the least one red light-emitting device, the at least one BSY light-emitting device having a first BSY output and the at least one BSY light-emitting device having a second BSY output with a greater yellow content than the first BSY output are serially connected in a string of light-emitting devices coupled between first and second terminals; and

wherein the control circuit is configured to vary a color temperature produced by the string responsive to a variation in a total current passing between the first and second terminals.

27. The apparatus of claim 19, wherein the control circuit is configured to provide a substantially fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels.

28. The apparatus of claim 27, wherein the first range of brightness levels is a range of brightness levels between a maximum brightness level and about 20% of the maximum brightness level.

29. A lighting apparatus comprising:

a plurality of light-emitting devices comprising light-emitting devices having at least three different chromaticities; and

a control circuit operatively coupled to the plurality of light-emitting devices and configured to cause a color temperature produced by the plurality of light-emitting devices to vary in response to a dimming control input over a range from about 5000K to about 2000K while maintaining a color rendering index (CRI) greater than about 80%.

30. The apparatus of claim 29, wherein the control circuit and the plurality of light-emitting devices are configured to maintain a CRI greater than about 90% for brightness levels between a maximum brightness level and about 20% of the maximum brightness level.

31. The apparatus of claim 29, wherein the plurality of light-emitting devices comprises at least one BSY light-emitting device having a first BSY output, at least one BSY light-emitting device having a second BSY output with a greater yellow content than the first BSY output and at least one red light-emitting device.

32. The apparatus of claim 29:

wherein the plurality of light-emitting devices comprises a string of serially-connected light-emitting devices coupled between first and second terminals and comprising a first set of light-emitting devices having a first chromaticity and a second set of light-emitting devices having a second chromaticity different from the first chromaticity; and

wherein the control circuit is operatively coupled to the string and configured to vary a color temperature produced by the string responsive to a variation in a total current passing between the first and second terminals.

33. The apparatus of claim 32, wherein the string of serially-connected light-emitting devices comprises at least one BSY light-emitting device having a first BSY output and at least one BSY light-emitting device having a second BSY output with a greater yellow content than the first BSY output.

34. The apparatus of claim 29, wherein the control circuit is configured to provide a substantially fixed color temperature over a first range of brightness levels and to conform the color temperature to the Planckian locus over a second range of brightness levels.

35. The apparatus of claim 34, wherein the first range of brightness levels is a range of brightness levels between a maximum brightness level and about 20% of the maximum brightness level.

36. A lighting apparatus comprising:

a plurality of light-emitting devices comprising first and second sets of light-emitting devices having substantially overlapping output spectra and chromaticities falling within respective first and second different chromaticity ranges; and

a control circuit operatively coupled to the plurality of light-emitting devices and configured to differentially operate the first and second sets of light-emitting devices in response to a dimming control input.

37. The apparatus of claim 36, wherein the first and second sets of light-emitting devices comprise first and second sets of LEDs in a string of LEDs serially-connected between first and second terminals.

38. The apparatus of claim 37, wherein the control circuit is configured to differentially vary current passing through the first and second sets of LEDs responsive to a total current passing between the first and second terminals.

39. The apparatus of claim 38, wherein the control circuit comprises a bypass circuit configured to differentially bypass current around the first set of LEDs with respect to the second set of LEDs responsive to the total current.

40. The apparatus of claim 36, wherein the first set of light emitting devices comprises a first set of blue-shifted yellow (BSY) LEDs, wherein the second set of LEDs comprises a second set of BSY LEDs.