LED-BASED FIXTURES AND RELATED METHODS FOR THERMAL MANAGEMENT

• US 20080285271A1
• Filed: 05/02/2008
• Published: 11/20/2008
• Est. Priority Date: 05/04/2007
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Philips Solid-State Lighting Solutions (Koninklijke Philips N.V.)
• Inventors: Lys, Ihor, Shikh, Igor, Roberge, Brian, Mollnow, Tomas, Koerner, Brad, Roberts, Ron
• Granted Patent: US 7,828,465 B2
• Time in Patent Office: Days
• US Class Current: 362/235
• CPC Class Codes: F21S 8/026 intended to be recessed in a ceiling or like overhead structure, e.g. suspended ceiling
• CPC Class Codes: F21S 8/033 the surface being a wall or like vertical structure, e.g. building facade
• CPC Class Codes: F21S 8/038 intended to be mounted on a light track suspended from a light track F21S8/066; details of supporting elements displaceable along a guiding element F21V21/34
• 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: F21S 8/06 by suspension
• CPC Class Codes: F21V 21/34 Supporting elements displaceable along a guiding element telescopic mounting of lighting devices F21V21/22
• CPC Class Codes: F21V 29/60 characterised by the use of a forced flow of gas, e.g. air
• CPC Class Codes: F21V 29/67 characterised by the arrangement of fans
• CPC Class Codes: F21V 29/677 the fans being used for discharging
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21V 29/763 the planes containing the fins or blades having the direction of the light emitting axis
• CPC Class Codes: F21V 29/773 the planes containing the fins or blades having the direction of the light emitting axis
• CPC Class Codes: F21V 29/80 with pins or wires
• CPC Class Codes: F21V 29/83 the elements having apertures, ducts or channels, e.g. heat radiation holes
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05B 45/00 Circuit arrangements for operating light-emitting diodes [LED]
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/325 Pulse-width modulation [PWM]
• CPC Class Codes: H05B 45/355 Power factor correction [PFC]; Reactive power compensation
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 : using buck topology
• CPC Class Codes: H05B 45/38 : using boost topology
• CPC Class Codes: H05B 45/385 : using flyback topology

Abstract

LED-based lighting fixtures suitable for general illumination in surface-mount or suspended installations, in which heat dissipation properties of the fixtures are significantly improved by decreasing thermal resistance between LED junctions and the ambient air. In various examples, improved heat dissipation is accomplished by increasing a surface area of one or more heat-dissipating elements proximate a trajectory of air flow through the fixture. In one aspect, various structural components of the fixtures are particularly configured to create and maintain a “chimney effect” within the fixture, resulting in a high air-flow rate, natural convection cooling system capable of efficiently dissipating the waste heat from the fixture without active cooling.

Claims

1. A lighting apparatus, comprising:

at least one LED light source;

a heat sink thermally coupled to the at least one LED light source;

a first housing portion mechanically coupled to the heat sink; and

a second housing portion mechanically coupled to the heat sink,

wherein;

the first housing portion is disposed with respect to the heat sink so as to form (i) a first air gap, (ii) a second air gap and (iii) an air channel through the lighting apparatus such that, when the heat sink transfers heat from the at least one LED light source during operation of the at least one LED light source so as to create heated air surrounding the heat sink, ambient air is drawn through the first air gap and the heated air is exhausted through the second air gap so as to create an air flow trajectory in the air channel from the first air gap to the second air gap.

2. The apparatus of claim 1, wherein the lighting apparatus is configured as a downlight fixture, wherein the second housing portion includes a mounting plate for mounting the downlight fixture to a surface, and wherein the first housing portion includes a bezel plate.

3. The apparatus of claim 2, further comprising a cover lens, disposed within a cavity formed by the bezel plate, for covering the at least one LED light source.

4. The apparatus of claim 1, wherein the heat sink is formed such that a majority of a surface area of the heat sink is disposed along the air channel between the first air gap and the second air gap.

5. The apparatus of claim 1, wherein the heat sink comprises a plurality of heat-dissipating fins.

6. The apparatus of claim 1, wherein the air channel substantially surrounds a perimeter of the at least one LED light source.

7. The apparatus of claim 5, wherein the second housing portion includes a mounting plate for mounting the apparatus to a surface, and wherein the first housing portion includes a bezel plate.

8. The apparatus of claim 6, wherein the lighting apparatus is mounted to the surface, the heat sink is disposed vertically above the light source and the air flow trajectory is primarily in an upward direction.

9. The apparatus of claim 8, wherein the apparatus further includes a power supply, wherein the heat sink includes a first recess on a first side of the heat sink for receiving the at least one LED light source, and wherein the heat sink further includes a second recess on a second side opposite the first side for receiving the power supply.

10. The apparatus of claim 1, wherein the at least one LED light source comprises:

a plurality of LEDs disposed on a printed circuit board; and

a plurality of reflector optics disposed so as to receive light generated by the plurality of LEDs,

wherein the plurality of reflector optics is coupled to the printed circuit board without using an adhesive.

11. A lighting fixture, comprising:

a bezel plate including an opening through which light passes, when generated by the fixture;

an LED module including at least one LED for generating the light; and

a heat dissipating frame mechanically coupled to the bezel plate and including a mounting portion positioned within the opening of the bezel plate, the LED module being disposed on the mounting portion of the heat dissipating frame,

wherein the bezel plate and the heat dissipating frame are positioned with respect to each other so as to form an air channel through the fixture, such that an air flow is created in the air channel via a chimney effect in response to heat generated by the LED module.

12. The fixture of claim 11, wherein at least a portion of the bezel plate constitutes a front face of the lighting fixture when the lighting fixture is mounted to a surface, and wherein the bezel plate and the heat dissipating frame are positioned with respect to each other so as to form an inlet air gap in the front face of the lighting fixture to allow ambient air to be drawn into the air channel via the chimney effect.

13. The fixture of claim 12, wherein the based plate and the heat dissipating frame are positioned with respect to each other so as to form an outlet air gap such that, when the lighting fixture is mounted to the surface, the outlet air gap is proximate to the surface to allow effluent air to be exhausted out of the air channel via the chimney effect.

14. The fixture of claim 11, wherein the LED module includes at least one white LED.

15. The fixture of claim 11, wherein the LED module comprises:

a printed circuit board;

a plurality of LEDs coupled to the printed circuit board;

a thermal gap pad for providing a thermal connection and electrical isolation between the printed circuit board and the mounting portion of the heat dissipating frame; and

an optical assembly coupled to the printed circuit board for collimating the light generated by the LED module.

16. The fixture of claim 15, wherein the plurality of LEDs includes at least one white LED.

17. The fixture of claim 15, wherein the optical assembly is coupled to the printed circuit board without using an adhesive.

18. The fixture of claim 15, wherein the LED module is coupled to the mounting portion of the heat dissipating frame without using an adhesive.

19. The fixture of claim 17, wherein the mounting portion of the heat dissipating frame includes a first recess within which the LED module is disposed.

20. The fixture of claim 11, wherein the mounting portion of the heat dissipating frame includes a first recess within which the LED module is disposed, wherein the heat dissipating frame includes a second recess on an opposing side of the first recess, and wherein the fixture further comprises a power/control module disposed within the second recess.

21. The fixture of claim 20, wherein the power/control module includes a switching power supply for providing power factor correction and an output voltage to the LED module via control of a single switch, without requiring any feedback information associated with the at least one LED.

22. The fixture of claim 21, wherein the switching power supply includes at least one controller coupled to the single switch, the at least one controller controlling the single switch using a fixed off time (FOT) control technique.

23. The fixture of claim 21, wherein the output voltage and/or the power provided to the at least one LED is significantly variable only in response to variations in an RMS value of an A.C. input voltage applied to the power supply.

24. The fixture of claim 21, wherein the switching power supply comprises a boost converter configuration including an over-voltage protection circuit for shutting down the switching power supply if the output voltage exceeds a predetermined value.

25. The fixture of claim 21, wherein the power/control module further includes an A.C. dimmer for varying an RMS value of an A.C. input voltage applied to the power supply, wherein the output voltage to the at least one LED-based light source varies based at least in part on the RMS value of the A.C. input voltage.

26. A method for cooling an LED-based lighting fixture, comprising:

drawing ambient air into the lighting fixture through a first air gap, flowing the ambient air through an internal air channel of the lighting fixture, and exhausting heated air from the lighting fixture through a second air gap, without using a fan and via a chimney effect in response to heat generated by at least one LED of the LED-based lighting fixture.