Tunable White Point Light Source Using a Wavelength Converting Element

• US 20080142816A1
• Filed: 12/15/2006
• Published: 06/19/2008
• Est. Priority Date: 12/15/2006
• Status: Active Grant

• Current Assignee: Lumileds LLC (Apollo Global Management, Inc.)
• Original Assignee: Philips Lumileds Lighting Company LLC (Apollo Global Management, Inc.)
• Inventors: Harbers, Gerard, Bierhuizen, Serge J.
• Granted Patent: US 7,902,560 B2
• Time in Patent Office: Days
• US Class Current: 257/82
• CPC Class Codes: F21K 9/00 Light sources using semiconductor devices as light-generating elements, e.g. using light-emitting diodes [LED] or lasers
• CPC Class Codes: F21V 23/0457 the sensor sensing the operating status of the lighting device, e.g. to detect failure of a light source or to provide feedback to the device
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H01L 25/0753 the devices being arranged next to each other
• CPC Class Codes: H01L 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 31/14 the light source or sources being controlled by the semiconductor device sensitive to radiation, e.g. image converters, image amplifiers or image storage devices
• CPC Class Codes: H01L 33/504 Elements with two or more wavelength conversion materials
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/40 Details of LED load circuits

Abstract

A uniform high brightness light source is provided using a plurality of light emitting diode (LED) chips with slightly different pump wavelengths with a wavelength converting element that includes at least two different wavelength converting materials that convert the light to different colors of light. The intensity of the light produced by the LED chips may be varied to provide a tunable CCT white point. The wavelength converting element may be, e.g., a stack or mixture of phosphor or luminescent ceramics. Moreover, the manufacturing process of the light source is simplified because the LED chips are all manufactured using the same technology eliminating the need to manufacture different types of chips.

Claims

1. A light source comprising:

at least two light emitting diode chips, each of which produces light having wavelengths that differ by 5nm or more; and

a wavelength converting element mounted to receive the light emitted by the at least two light emitting diode chips, the wavelength converting element comprising at least two different wavelength converting materials that convert the light from the at least two light emitting diode chips to different colors of light.

2. The light source of claim 1, wherein the wavelength converting element comprises a stack of wavelength converting films.

3. The light source of claim 1, wherein the wavelength converting element comprises a mixture of the different wavelength converting materials that convert the light from the at least two light emitting diode chips to different colors of light.

4. The light source of claim 3, wherein the mixture of the different wavelength converting materials is approximately homogenous.

5. The light source of claim 1, wherein the wavelength converting element comprises one or more luminescent ceramics.

6. The light source of claim 1, wherein the wavelength converting element comprises one or more phosphor layers.

7. The light source of claim 1, further comprising at least one submount, the at least two light emitting diode chips mounted to the at least one submount.

8. The light source of claim 7, further comprising:

a heat sink, the at least one submount being mounted on the heat sink; and

a support that is coupled to the heat sink, the support holding the wavelength converting element.

9. The light source of claim 7, wherein the at least one submount is one submount and the at least two light emitting diode chips are mounted on the one submount.

10. The light source of claim 1, further comprising:

at least one light detector positioned to receive light produced by the wavelength converting element and producing a signal in response to the intensity of the light detected; and

a drive circuit coupled to the at least two light emitting diode chips and the at least one light detector, the drive circuit controlling the intensity of the light emitted by at least one of the light emitting diode chips in response to the signal produced by the at least one light detector.

11. The light source of claim 1, further comprising a wavelength selection element positioned between the at least two light emitting diode chips and the wavelength converting element.

12. The light source of claim 11, further comprising:

a collimator element positioned between the at least two light emitting diode chips and the wavelength selection element; and

a concentrator element positioned between the wavelength selection element and the wavelength converting element.

13. The light source of claim 1, wherein the at least two light emitting diode chips produce light having wavelengths that differ by 50 nm or less.

14. A method comprising:

producing light from a plurality of light emitting diode chips, each chip producing light with a different range of wavelengths that differ by more than approximately 5 nm;

converting portions of the light from the plurality of light emitting diode chips to at least two different colors of light using a wavelength converting element and transmitting other portions of the light from the plurality of light emitting diode chips through the wavelength converting element to produce a combined converted and transmitted light; and

controlling the white point of the combined converted and transmitted light by altering an intensity of the light from at least one light emitting diode chip to vary an intensity of at least one color of light converted by the wavelength converting element.

15. The method of claim 14, further comprising mounting the plurality of light emitting diode chips on at least one submount.

16. The method of claim 15, further comprising:

mounting the at least one submount to a heat sink; and

mounting the wavelength converting element over the plurality of light emitting diode chips on a support that is coupled to the heat sink.

17. The method of claim 14, wherein converting portions of the light from the plurality of light emitting diode chips is performed in a stack of wavelength converting films that form the wavelength converting element.

18. The method of claim 17, wherein the stack of wavelength converting films comprises one or more luminescent ceramics.

19. The method of claim 14, wherein the stack of wavelength converting films comprises one or more phosphor layers.

20. The method of claim 14, wherein converting portions of the light from the plurality of light emitting diode chips is performed by a mixture of a different wavelength converting materials in the wavelength converting element.

21. The method of claim 20, wherein the mixture of the different wavelength converting materials is approximately homogenous.

22. The method of claim 14, further comprising:

detecting the combined converted and transmitted light and producing a signal in response; and

altering an intensity of the light from at least one light emitting diode chip in response to the signal produced by the light detector.

23. The method of claim 22, wherein the detecting and altering are performed continuously or periodically.

24. The method of claim 22, wherein the detecting and altering are performed once.

25. The method of claim 14, further comprising transmitting light from a plurality of light emitting diode chips through a wavelength selection element and reflecting back converted light from the wavelength converting element by the wavelength selection element.

26. The method of claim 25, further comprising:

approximately collimating the light from a plurality of light emitting diode chips prior to being transmitted through the wavelength selection element; and

concentrating the light from a plurality of light emitting diode chips after being transmitted through the wavelength selection element and prior to being incident on the wavelength converting element.

27. The method of claim 14, the method further comprising producing light from at least one group of light emitting diode chips, each chip within a group producing light with a range of wavelengths that differ by less than approximately 5 nm.

28. The method of claim 14, wherein each chip produces light with a different range of wavelengths that differ by less than approximately 50 nm.