Methods and Apparatus for Improved Heat Spreading in Solid State Lighting Systems

• US 20080089069A1
• Filed: 10/11/2006
• Published: 04/17/2008
• Est. Priority Date: 10/11/2006
• Status: Active Grant

• Current Assignee: IDEAL Industries Lighting, LLC (Ideal Industries Incorporated)
• Original Assignee: CREE Incorporated (Wolfspeed, Inc.)
• Inventors: Medendorp, Nicholas W.
• Granted Patent: US 7,794,114 B2
• Time in Patent Office: Days
• US Class Current: 362/294
• CPC Class Codes: F21S 2/005 of modular construction
• CPC Class Codes: F21S 6/00 Lighting devices intended to be free-standing F21S9/00, F21S10/00, F21S13/12 take precedence lighting devices specially adapted to be transported from place to place, e.g. lighting devices carried on wheeled supports F21L; details of supports for lighting devices F21V21/00
• CPC Class Codes: F21S 8/04 intended only for mounting on a ceiling or the like overhead structures F21S8/02 takes precedence; details of ceiling bases F21V21/03
• CPC Class Codes: F21V 29/70 characterised by passive heat-dissipating elements, e.g. heat-sinks
• CPC Class Codes: F21V 29/763 the planes containing the fins or blades having the direction of the light emitting axis
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: F28F 21/02 of carbon, e.g. graphite
• CPC Class Codes: F28F 3/02 Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations F28F3/08 takes precedence

Abstract

A solid state lighting subassembly or fixture includes an anisotropic heat spreading material. A heat spreading layer may be placed between a light emitting diode (LED) and luminaire or reflector and serves to spread heat laterally away from the LED. Low profile, low weight heat spreading may be utilized both to retrofit existing light fixtures with. LEDs or to replace existing incandescent and fluorescent fixtures with LED based fixtures.

Claims

1. A solid state lighting fixture comprising:

a thermally conductive component;

a solid state light source;

an anisotropic heat spreader in thermal contact with the solid state light source and the thermally conductive component of the lighting fixture so as to spread heat from the solid state light source in a preferential direction from the solid state light source to said thermally conductive component thereby making said thermally conductive component a more effective heat sink for the solid state light source.

2. The solid state lighting fixture of claim 1 further comprising a plurality of high power solid state light sources capable of providing sufficient ambient room lighting greater than or equivalent to a comparably sized fluorescent lighting fixture.

3. The solid state lighting fixture of claim 2 wherein said plurality of high power solid state light sources comprises a plurality of high power light emitting diodes (LEDs) having a current of at least 125 mA.

4. The solid state lighting fixture of claim 3 wherein said plurality of high power LEDs are mounted so that at least one sheet of anisotropic graphite spreads the heat from all of said plurality of high power LEDs.

5. The solid state lighting fixture of claim 4 wherein said at least one sheet of anisotropic graphite is pressed on an underside of a standard luminaire.

6. The solid state light fixture of claim 4 wherein said at least one sheet of anisotropic graphite is pressed on an overside of a standard luminaire.

7. The solid state lighting fixture of claim 6 wherein a heat conductive via thermally connects the high power LEDs mounted on an underside of the standard luminaire to said at least one sheet of graphite pressed on the overside of the standard luminaire.

8. The solid state lighting fixture of claim 1 wherein said lighting fixture provides at least an equivalent amount of light with a profile and size comparable to that of a standard fluorescent lighting fixture.

9. The solid state lighting fixture of claim 3 wherein said plurality of high power LEDs are mounted parallel to a longitudinal axis of the solid state lighting fixture and each one of said plurality of high power LEDs has a corresponding strip of anisotropic graphite to direct its heat preferentially in a direction substantially perpendicular to the longitudinal axis of the solid state lighting fixture.

10. The solid state lighting fixture of claim 5 wherein said single sheet of anisotropic graphite is covered with a polymer-based overfill having a color matching that of said standard luminaire.

11. The solid state lighting fixture of claim 1 wherein the anisotropic heat spreader spreads heat better in a plane by a factor of at least five times than in a direction perpendicular to the plane.

12. The solid state lighting fixture of claim 1 wherein said thermally conductive component is an aluminum reflector.

13. The solid state lighting fixture of claim 12 wherein the aluminum reflector has a thermal conductivity of approximately 205-220 W/m-K at room temperature.

14. The solid state lighting fixture of claim 13 wherein the anisotropic heat spreader is a sheet material thermally adhered to the thermally conductive component and has a thermal conductivity in a plane of at least twice that of the aluminum reflector.

15. The solid state lighting fixture of claim 11 wherein said thermally conductive component is an isotropic heat sink.

16. A solid state lighting subassembly comprising:

a plurality of light emitting diodes (LEDs);

a thermally isotropic mount supporting the plurality of light emitting diodes;

and anisotropic material thermally conducting heat from one or more of said plurality of LEDs and the thermally isotropic mount in a preferential direction to more effectively utilize said mount as a heat sink.

17. The solid state lighting subassembly of claim 16 wherein said mounting material comprises an aluminum reflectors.

18. The solid state lighting subassembly of claim 16 wherein said anisotropic material is a sheet of anisotropic graphite.

19. The solid state lighting subassembly of claim 16 wherein said plurality of LEDs have a current of at least 125 mA.

20. The solid state lighting subassembly of claim 16 wherein said mount is an isotropic heat slink and said anisotropic material is a sheet adhered to a face of said mount, and said anisotropic material has a thermal conductivity in the plan of the sheet which is at least a factor of five times greater than its thermal conductivity in a direction perpendicular to said plane.