WO2006105346A2

WO2006105346A2 - Small form factor downlight system

Info

Publication number: WO2006105346A2
Application number: PCT/US2006/011771
Authority: WO
Inventors: Stephen G. Johnson
Original assignee: Integrated Lighting Solutions Llc
Priority date: 2005-03-29
Filing date: 2006-03-29
Publication date: 2006-10-05
Also published as: WO2006105346A3

Abstract

A downlight system includes a substrate. One or more light emitting diodes are disposed on a surface of the substrate for emitting light in a single direction. A respective primary optic for providing a substantially even color of light is optically coupled to a respective one of each of said one or more light emitting diodes.

Description

SMALL FORM FACTOR DOWNLIGHT SYSTE

CROSS-REFERENCE TO RELATED APPLICATIONS

This Application claims the benefit of U.S. Provisional Application No. 60/666,103 filed on March 29, 2005, entitled SMALL FORM FACTOR LED DOWNLIGHT SYSTEM WITH ADJUSTABLE SECONDARY OPTICS, the disclosure of which is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

This invention is directed to a downlight system, in particular a downlight system making use of light emitting diodes (LEDs) to produce light in a smaller form factor.

Reference is first made to Fig. 1 where a schematic diagram of a downlight as known in the art is provided. Downlights 100 are luminaires and include housings 102 having sufficient height that they are recessed into ceilings 106 and project light in the downward direction of arrow A towards the floor. Downlights 100 currently use a number of different lamp types 104, as is known in the art; namely incandescent, halogen, compact fluorescent and metal halide light sources. All prior downlights have a common construction utilizing a single light source, or in some cases, compact fluorescent luminaires utilize two light sources, whose emitted radiation is focused downward by a reflecting element, either within the housing 102 or within the bulb 104. For aesthetic purposes, ceiling lights are desired to be flush with ceiling 106. Accordingly, because of the space requirement of housing 102, housing 102 projects up into ceiling 106 when luminaire 100 is flush with ceiling 106 requiring a space of many inches above the ceiling to accommodate the

The electrical connection is made to the luminaires made in the space above ceiling 106. The efficiency of these luminaires varies, depending greatly on the reflective element. The conventional sources emit light in a spherical pattern, 4pi steradians, requiring the reflector design to refocus the light emitted thereon, in the direction of Arrow A through fixture opening 108. These luminaires have been satisfactory, however, they are large, cumbersome, and highly energy inefficient.

Accordingly, a downlight luminaire for overcoming the shortcomings is desired. BRIEF SUMMARY OF THE INVENTION

In one embodiment of the invention, each of the light emitting diodes is formed as a die- package, the primary optics including a lens, the lens being matched to minimize the refractive index as a function of the angle of the emissive distribution of light from the LED. In another embodiment, the primary optics includes a phosphor layer. In another embodiment of the invention, the primary optics includes a high refractive encapsulant material within the die-package.

The substrate may be formed of thermally conductive material to act as a heat sink. A trim ring is disposed about the substrate. The trim ring provides both aesthetic attributes and function. In one embodiment, the trim ring is formed of a thermally conductive material to act as an ancillary heat sink.

A secondary lens is provided along the light path of the LEDs to control the beam spread of the light emitted from the downlight system. The lens may be a non-imaging lens.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings:

Fig. 1 is a schematic view of a downlight fixture in accordance with the prior art;

Fig. 2 is an exploded perspective view of a downlight fixture in accordance with the invention;

Fig. 3 is side elevation sectional view of a pair of LEDs disposed on a substrate in accordance with the invention;

Fig. 4 is a perspective view of a downlight fixture constructed in accordance with the invention; Fig. 5 is a side elevational view of a downlight fixture constructed in accordance with the invention;

Fig. 6 is a first circuit diagram of the downlight fixture constructed in accordance with the invention;

Fig. 7 is a second circuit diagram of the downlight fixture constructed in accordance with the invention;

Fig. 8 is a schematic view of the downlight fixture mounted to the ceiling in accordance with the invention; and

Fig. 9 is the downlight fixture mounted to the ceiling in accordance with a second embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference is made to Fig.2 in which an LED downlight system, generally indicated as 10, constructed in accordance with the invention, is provided. Downlight system 10 includes a substrate 20. Substrate 20 has a downward facing surface 25. A plurality of light emitting diodes 22 are disposed on downward facing surface 25 and oriented to project light in a direction away from surface 25. hi a preferred embodiment, substrate 20 is made of a thermally conductive material to act as a heat sink to dissipate heat generated by the one or more LEDs 22.

Each of LEDs 22 is formed as a die as shown in Fig. 3. LEDs 22 are disposed within an optical cavity 24 formed within substrate 20. In a preferred embodiment, a high refractive encapsulant 26 is disposed within optical cavity 24 encapsulate LED 22. In a preferred embodiment, the high refractive encapsulant 26 has an index of refraction greater than about 1.5. The encapsulant may be a silicon gel, by way of non-limiting example, having an index of refraction greater than 1.5.

LEDs 22, as known in the art, do not emit white light. They most commonly emit red, green and blue, and are capable of emitting other colors such as amber. Therefore, to produce white light, LEDs 22 may be formed in patterns of red, blue, green to combine for a white light effect. However, in a preferred embodiment, a phosphor diffuser layer 28 is disposed across an opening in optical cavity 24 downstream of the path of light as indicated by Arrow B. It should be noted that other color LED amber may be combined to soften the color of the emitted light. By mixing and matching the LED colors or using a phosphor layer 28, the possibility for an LED assembly that can emit a single color or a variety of colors is present.

The light that is emitted from the optical cavity 24 is focused by two elements; a primary lens 27 and the reflective surface 23 under the primary lens 27. In a preferred embodiment, lens 27 is matched to the function of the angle of the emissive distribution of light from phosphor layer 28, or in the absence of phosphor layer 28, from the reflector to minimize internal reflections.

In a preferred embodiment, lens 27 defines a volume between lens 27 and a respective LED 22. A second high refractive index encapsulant 29 is disposed in the volume defined by lens 27. In a preferred, non-limiting example, the lens 27 is a substantially hemispherical, substantially transparent, lens in order to maximize light transmission and reduce reflection. The reflector and lens 27 are optimized for the emissive distribution pattern of the LEDs.

In the preferred embodiment, LED 22 is optically coupled with high refractive index encapsulants 26, 29, phosphor diffuser layer 28, and lens 27. However, it is well within the scope of the invention to provide a downright without one or more of these structures associated with the LED. Therefore, the structures are collectively and individually referred to as the primary optics for creating a substantially even color of light across LEDs 22. Additionally, a common lens 27, and associated gels and phosphor layers may be associated with two or more LEDs 22, and two or more LEDs may be disposed in a single optical cavity. Furthermore, LEDs 22 may be formed as die-packages mounted to substrate 20, rather than optical cavities formed within substrate 20; both being considered disposed on the substrate.

Secondary lens 30 is used as an additional optical element. Secondary lens 30 may serve to further diffuse the light from the individual LEDs 22, or it may provide additional optical control to the light emitted from the assembly of LEDs 22.

In a preferred embodiment, secondary lens 30 is a non-imaging lens utilizing the principles of non-imaging optics to generate a desired light distribution. As known in the art, nonimaging optics incorporate the calculation of free form surfaces, which redistributes light. Such non-imaging optics are known in the art; provided by OEC by way of example. As a result of the non-imaging mixing, secondary lens 30 can farther diffuse the light or enhance a uniform light color output by mixing different colored light output by the individual LEDs 22 of different color distributions as visible white light.

Furthermore, by interchanging a plurality of secondary lenses 30, the beam spread of the light may be changed from a straight beam (spotlight) or a wide beam (Gaussian) distribution. In such a way, adjustable beam spread is provided by secondary lens 30.

Lastly, as a result of the non-imaging structure, secondary lens 30 can control the output from the LEDs 22 to reduce or eliminate veiling glare, improving the aesthetics of the fixtures when viewed from below.

Trim ring 40 is disposed about substrate 20 and hides substrate 20 improving the overall aesthetics of downlight system 10. In a preferred embodiment, trim ring 40 is formed of a thermally conductive material and may be provided with radiating fins 42 disposed around the circumference of trim ring 40. In this way, trim ring 40 acts as an ancillary or secondary heat sink to thermally manage the heat generated by the operation of LEDs 22. It is understood that, in lesser-preferred embodiments, active elements such as a fan may be used to dissipate heat by convection. Furthermore, passive heat dissipation structure such as fins 42 may be located on the side of substrate 20 opposite side 23 to hide the heat dissipation structure from view.

LEDs 22 are low voltage direct current devices. As such, the power source, particularly for household use, will convert the supplied power from AC to a predetermined DC voltage potential. The power supply design may be either a voltage limiting or current limiting circuit. In a preferred embodiment, LEDs 22 are arrayed in a pattern to control the current by matching the voltage of the power source. IfLEDs 22 are in parallel with the power supply 70 (see Fig. 6), the voltage is lowered. IfLEDs 22 are in series with the power supply 70 (see Fig. 7), then the current can be lowered. It should be noted that the power source may be independent of downlight system 10 as in conventional wiring structures for light fixtures as known in the art. However, as a result of the compact design as a result of the use of LEDs 22 and substrate 20, the power source may be incorporated directly into downlight system 10.

Reference is now made to Figs. 8 and 9 wherein the manner in which downlight system 10 is mounted is provided. As is readily seen from Fig. 5, as a result of the use of substrate 20 to support the light source, rather than the elongated housing 102 as known in the prior art, downlight system 10 has a substantially planar, thin profile relative to the prior art. Therefore, as seen in Fig. 8, downlight system 10 may be affixed directly to ceiling 106 without need for any recess therein and still provide the aesthetics of being essentially flush with ceiling 106. However, to appear even more flush with ceiling 106, downlight system 10 may be recessed within ceiling 106 as seen in Fig. 9.

By providing an LED downlight system, a light fixture is provided which projects light downward from the ceiling in a fundamentally different form and manner. Because the light sources are much smaller than traditional sources, they may be assembled as an array on a flat substrate. This allows for even distribution of light across the emitting surface of the luminaire. By incorporating small optics associated with each respective LED (light source) to direct the light in the desired direction, the large luminaire conventional design is no longer needed. Therefore, the luminaire can be made to be much thinner, reducing the requirement for a large space above the ceiling. The luminaire may be so thin as to not require penetration of the ceiling at all.

The LED assembly may be powered at a DC voltage allowing ease of wiring both above and below the ceiling surface. A decorative ring or trim ring may be incorporated that cosmetically masks the transition of the ceiling to the luminaire as well as dissipate the heat generated by the LEDs and the heat generated by the power source. If the light source is assembled on a substrate acting as a heat sink, maximum dissipation of the heat of the components is provided while facilitating a thin dimension to the system. Optics may be built into the individual LEDs to provide primary optics of the source while a detachable lens may provide secondary optics providing a variety of light color, beam shape and softness utilizing a simple interchangeable structure.

While this invention has been particularly shown and described with references to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention encompassed by the inventive claims.

Claims

CLAIMSWhat is claimed as new and desired to be protected by Letters Patent of the United States is:

1. A downright system comprising: a substrate; a light source mounted on said substrate, said light source including a plurality of light-emitting diodes and primary optics optically coupled with said light emitting diodes for providing a substantially even color of light.

2. The system of claim 1 , wherein said substrate is formed of a thermally conductive material for dissipating heat from said light source.

3. The system of claim 1 , wherein said plurality of light emitting diodes are assembled as an array on said substrate.

4. The system of claim 1, further comprising a plurality of optical cavities formed in said substrate, said light emitting diodes being disposed in said plurality of optical cavities, each said optical cavity having an open end.

5. The system of claim 1, wherein said primary optics includes a phosphor layer disposed downstream of light emitted from said light emitting diode.

6. The system of claim 4, wherein said primary optics includes a phosphor layer disposed across said open end downstream of light emitted from said light emitter diode.

7. The system of claim 4, wherein said primary optics includes a high refractive index encapsulant disposed within said optical cavity substantially encapsulating said light emitting diode.

8. The system of claim 1, wherein said primary optics includes a primary lens disposed downstream of light emitted from said light emitting diode.

9. The system of claim 8, wherein said primary lens defines a volume between said lens and said light emitting diode and said primary optics includes a high refractive index encapsulant disposed in said defined volume.

10. The system of claim 1 , further comprising a plurality of optical cavities formed in said substrate, said light emitting diodes being disposed in said plurality of optical cavities, each said optical cavity having an open end; said primary optics including a phosphor layer disposed across said open end; a high refractive index encapsulant being disposed within said optical cavity substantially encapsulating said light emitting diode; a primary lens disposed downstream of light emitted from said light emitting diode and circumscribing a volume; and a second high refractive index encapsulant disposed within said circumscribed volume.

11. The system of claim 1 , wherein at least one of said light emitting diodes emits light of a first color and at least a second one of said light emitting diodes emits light of a second color, the first color being different from the second color.

12. The system of claim 1, further comprising a trim ring disposed about said substrate.

13. The system of claim 12, wherein said trim ring is formed of a thermally conductive material.

14. The system of claim 12, wherein said trim ring includes radiating fins for thermally dissipating heat from said light source.

15. The system of claim 1, further comprising a secondary lens for diffusing light from said light source.

16. The system of claim 15, wherein said secondary lens is a non-imaging lens.

17. The system of claim 1 , further comprising a plurality of interchangeable secondary lenses to provide a degree of output light beam spread, each secondary lens of said plurality of secondary lenses providing a different respective degree of output light beam spread.

18. The system of claim 11 , further comprising a secondary lens, the secondary lens receiving light of at least the first color and the second color emitted by the light emitting diodes and producing a uniform colored light output.

19. The system of claim 1 , further comprising a secondary lens downstream of the light output to provide a uniform luminance of light emitted by said light source.

20. The system of claim 1, wherein said plurality of light emitting diodes are arranged to require a voltage equivalent to a voltage supplied by a power source.