Solid state luminaires for general illumination

• US 20070247414A1
• Filed: 04/21/2006
• Published: 10/25/2007
• Est. Priority Date: 04/21/2006
• Status: Active Grant

• Current Assignee: Brightplus Ventures LLC (IPValuation Partners, LLC)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Roberts, John
• Granted Patent: US 7,777,166 B2
• Time in Patent Office: Days
• US Class Current: 345/102
• CPC Class Codes: F21K 9/68 Details of reflectors forming part of the light source
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: F21V 13/10 the elements being reflectors and screens
• CPC Class Codes: F21V 29/70 characterised by passive heat-dissipating elements, e.g. heat-sinks
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21V 7/10 Construction
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: G01D 11/28 Structurally-combined illuminating devices
• CPC Class Codes: G01J 1/32 adapted for automatic variation of the measured or reference value regulation of light intensity G05D25/00
• CPC Class Codes: G09F 9/3026 Video wall, i.e. stackable semiconductor matrix display modules video wall control systems G06F3/1446, G09G2300/026
• CPC Class Codes: G09G 3/32 semiconductive, e.g. using light-emitting diodes [LED]
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: H04N 9/315 Modulator illumination systems general applications of lighting devices F21V; general optical systems G02B; lamp houses for projectors not peculiar to the presence of an electronic spatial light modulator G03B21/20

Abstract

A lighting panel includes a tile having a first side parallel to a principal plane of the lighting panel, a plurality of solid state lighting devices arranged on the first side of the tile and configured to emit light, a reflector sheet on the first side of the tile, and a brightness enhancement film on the reflector sheet. The reflector sheet may be arranged between the tile and the brightness enhancement film and the brightness enhancement film may be configured to increase the on-axis intensity of emitted light. A luminaire adapted for general illumination includes a lighting panel as described above, a current supply circuit configured to supply an on-state drive current to a string of lighting devices in response to a control signal, a photosensor arranged to receive light from one of the solid state lighting devices, and a control system configured to receive an output signal from the photosensor and to adjust the control signal responsive to the output signal of the photosensor.

Claims

1. A lighting panel, comprising:

at least one tile having a first side parallel to a principal plane of the lighting panel;

a plurality of solid state lighting devices arranged on the first side of the at least one tile and configured to emit light;

a reflector sheet on the first side of the at least one tile; and

a brightness enhancement film on the reflector sheet, wherein the reflector sheet is arranged between the at least one tile and the brightness enhancement film and the brightness enhancement film is configured to preferentially emit light having a first orientation from the lighting panel and to preferentially reflect light having a second orientation, different from the first orientation, back into the lighting panel.

2. The lighting panel of claim 1, wherein the reflector sheet is configured to reflect and disperse light incident thereon.

3. The lighting panel of claim 1, wherein the reflector sheet includes a plurality of apertures therethrough, wherein respective ones of the plurality of apertures aligned with corresponding ones of the plurality of solid state lighting devices.

4. The lighting panel of claim 3, wherein respective ones of the apertures include angled sidewalls to thereby form reflective optical cavities around the corresponding ones of the plurality of solid state lighting devices.

5. The lighting panel of claim 1, wherein the reflector sheet comprises a plastic foam.

6. The lighting panel of claim 1, further comprising a diffuser sheet between the reflector sheet and the brightness enhancement film.

7. The lighting panel of claim 1, wherein the brightness enhancement film comprises a plurality of three dimensional light extraction features configured to bend at least some light rays passing through the brightness enhancement film toward the direction normal to the principal plane of the lighting panel.

8. The lighting panel of claim 7, wherein the light extraction features are random features.

9. The lighting panel of claim 7, wherein the brightness enhancement film is configured to limit direct emission from the lighting panel of light emitted by the plurality of solid state light emitting devices to thereby encourage light recycling/diffusion in the lighting panel.

10. The lighting panel of claim 7, wherein the light extraction features comprise fresnel-type lenses.

11. The lighting panel of claim 7, wherein the brightness enhancement film is configured to substantially collimate light emitted by the lighting panel.

12. The lighting panel of claim 1, further comprising a heatsink panel on a second side of the at least one tile opposite to the first side and configured to draw heat away from the at least one tile in a direction opposite to a direction of light emission from the at least one tile.

13. The lighting panel of claim 12, wherein the heatsink panel comprises black anodized aluminum.

14. The lighting panel of claim 13, wherein the heatsink panel comprises a plurality of heatsink features configured to reduce a thermal resistance of the heatsink panel.

15. The lighting panel of claim 14, wherein the plurality of heatsink features comprise cooling fins.

16. The lighting panel of claim 14, wherein respective ones of the plurality of heatsink features are aligned with corresponding ones of the plurality of solid state light emitting devices.

17. A luminaire adapted for general illumination, the luminaire comprising:

a lighting panel including at least one tile, a plurality of solid state lighting devices electrically connected in a string and arranged on a first side of the at least one tile and configured to emit light at a dominant wavelength, a reflector sheet on the first side of the at least one tile, and a brightness enhancement film on the reflector sheet, wherein the reflector sheet is arranged between the at least one tile and the brightness enhancement film;

a current supply circuit configured to supply an on-state drive current to the string in response to a control signal;

a photosensor arranged to receive light from at least one of the plurality of solid state lighting devices; and

a control system configured to receive an output signal from the photosensor and to adjust the control signal responsive to the output signal of the photosensor to thereby adjust an average current supplied to the string by the current supply circuit.

18. The luminaire of claim 17, wherein the current supply circuit comprises a closed loop variable voltage boost converter current source.

19. The luminaire of claim 17, wherein the control system is configured to sample the output of the photosensor when current is not being supplied to the string of solid state lighting devices to obtain an ambient light value.

20. The luminaire of claim 19, wherein the control system is configured to decrease average current to the string as the ambient light value increases.

21. The luminaire of claim 17, wherein the control system is configured to sample the photosensor during an interval in which current is being supplied to the string in order to obtain a brightness value.

22. The luminaire of claim 21, wherein the control system is configured to decrease the average current to the first string as the brightness value increases.

23. The luminaire of claim 22, wherein the control system is configured to adjust the average current supplied to the string based on the ambient light value and the brightness value.

24. The luminaire of claim 23, wherein the control system is configured to adjust the average current supplied to the string based on a difference between the ambient light value and the brightness value.

25. The luminaire of claim 23, wherein the control system is configured to adjust the average current supplied to the string based on a ratio of the ambient light value and the brightness value.

26. The luminaire of claim 23, wherein the control system is configured to maintain an average luminosity of the first string independent of an ambient/background illumination.

27. The luminaire of claim 23, wherein the control system is configured to maintain a relationship between an ambient/background illumination and an average luminosity of the string by providing a first feedback signal with respect to the ambient light value and a second feedback signal with respect to the brightness value.

28. The luminaire of claim 17, wherein the control signal comprises a pulse width modulation (PWM) signal, and wherein the control system is configured to control an average current supplied to the string by varying a duty cycle of the PWM signal.

29. The luminaire of claim 17, wherein the control system is configured to control an average current supplied to the string by varying a pulse frequency of the control signal.

30. The luminaire of claim 17, wherein the current supply circuit is configured to maintain the on-state current supplied to the string at a substantially constant value even as the average current supplied to the string is varied.

31. The luminaire of claim 17, wherein the control system comprises:

a color management unit coupled to the photosensor and configured to sample and process the output signal of the photosensor and to provide the processed output signal to the control system.

32. The luminaire of claim 17, further comprising:

a temperature sensor configured to sense a temperature associated with the lighting panel, wherein the control system is configured to adjust an average current supplied to the first string in response to a change in the sensed temperature.

33. A luminaire, comprising:

a lighting panel including at least one tile, at least a first string of solid state lighting devices on a first side of the at least one tile and configured to emit light at a first dominant wavelength and a second string of solid state lighting devices on the first side of the at least one tile and configured to emit light at a second dominant wavelength, different from the first dominant wavelength, a reflector sheet on the first side of the at least one tile, and a brightness enhancement film on the reflector sheet, wherein the reflector sheet is arranged between the at least one tile and the brightness enhancement film;

a first current supply circuit configured to supply an on-state drive current to the first string in response to a first control signal;

a second current supply circuit configured to supply an on-state drive current to the second string in response to a second control signal;

a photosensor arranged to receive light from at least one solid state lighting device in the first string and at least one solid state lighting device in the second string; and

a control system configured to receive an output signal from the photosensor and to adjust the first control signal and/or the second control signal responsive to the output signal of the photosensor to thereby adjust an average current supplied to the first string by the first current supply circuit and/or to adjust an average current supplied to the second string by the second current supply circuit, such that the photosensor, the control system and the first and second current supply circuits thereby form a feedback loop for the lighting panel;

wherein the first and second control signals comprise pulse width modulation (PWM) signals, and wherein the control system is configured to control an average current supplied to the first and/or second string by varying a duty cycle of the first and/or second control signal.

34. The luminaire of claim 33, wherein a leading edge of a pulse of the first control signal occurs at a different time from a leading edge of a pulse of the second control signal.

35. The luminaire of claim 34, wherein the leading edge of the pulse of the first control signal is delayed from the leading edge of the pulse of the second control signal by a fixed delay.

36. The luminaire of claim 34, wherein the leading edge of the pulse of the first control signal is delayed from the leading edge of the pulse of the second control signal by a variable delay.

37. The luminaire of claim 36, wherein the variable delay changes within a range of delay intervals that is random, chaotic or determined by a sweep function, table or other technique, and/or is dependent on the pulse width of the first control signal and/or the second control signal.