WO2011117775A1

WO2011117775A1 - Illumination device with enclosure

Info

Publication number: WO2011117775A1
Application number: PCT/IB2011/051075
Authority: WO
Inventors: Ralph Kurt; Mark Eduard Johan Sipkes
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-03-22
Filing date: 2011-03-15
Publication date: 2011-09-29

Abstract

An illumination device comprising a carrier (1), a LED module (2) arranged on the carrier, the LED module comprising a plurality of LEDs (3), and a ring-shaped element (6) surrounding the LED module (2) and in contact with the carrier (1), sides of the ring-shaped element (6) facing the LEDs (3) being reflective. The ring-shaped element (6) has a first proximal portion (7) arranged closest to the carrier and defining an opening to surround the LED module, and a second, distal portion (8) arranged outside the proximal portion withrespect to the carrier and defining an exit aperture of the illumination device. The exit aperture is smaller than the opening in the proximal portion, so that the distal portion covers a portion (9) of the opening in the proximal portion. The inner edge of the secondportion thus forms an overhang along portions of the ring-shaped element, and along these portions covers an area immediately inside the proximal portion. In this shielded area parts of a relatively large LED module can be housed and be protected by the distalportion.

Description

Illumination device with enclosure

FIELD OF THE INVENTION

The present invention relates to an illumination device comprising a carrier, a LED module with a substrate supporting a plurality of LEDs, and an enclosure covering the LED array, the enclosure including a ring-shaped element arranged surrounding the LED array and in contact with the carrier, the sides of the ring-shaped element facing the LEDs being reflective.

BACKGROUND OF THE INVENTION

In various illumination applications, such as spot illumination systems for scene setting or other atmosphere creating lighting, white light sources with colored filters has been used to a great extent. Lately, as an alternative, illumination systems with colored light sources, such as light emitting diodes, LEDs, have been developed.

Using colored light sources eliminates the need for filtering, and thus increases efficiency and color consistency (replaced filter might introduce variation). Further, the emitted color can be changed by electronic control, and all accessible colors are always available without any hardware replacements. The market for these systems is quickly growing as LED performance improves.

The densely packed LED arrays are typically mounted on a carrier, such as a PCB, and enclosed by a suitabel enclosure. The LED array and its critical components such as wire bonds need to be protected against damage (non-intentional use) while still maintaining or even improving the light output. Document US 2009/0311811 discloses an example of such an enclosure, comprising a ring-shaped part surrounding the LED package, having a reflective inside, and a transmissive compound covering the LEDs inside the ring- shaped part. The inner edge of the ring-shaped part is tapered towards the carrier.

However, solutions such as that disclosed in US 2009/0311811 are not entirely satisfactory for all implementations. SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved LED module enclosure.

According to a first aspect of the invention, this and other objects are achieved by an illumination device as disclosed in the introduction, wherein the ring-shaped element has a first proximal portion arranged closest to said carrier and defining an opening to surround the LED module, and a second, distal portion arranged outside the proximal portion with respect to the carrier and defining an exit aperture of the illumination device, and wherein the exit aperture is smaller than the opening in the proximal portion, so that the distal portion covers a portion of the opening in the proximal portion.

The inner edge of the second portion thus forms an overhang along portions of the ring-shaped element, and along these portions covers an area immediately inside the proximal portion. In this shielded area parts of a relatively large LED module can be housed and be protected by the distal portion. Such parts of the LED module will thus be effectively outside the optical exit aperture of the device. Moreover, sensitive components such as wirebonds or sensors (optical / thermal sensors) may be placed in the "shadow" of the distal portion.

It should be noted that the overhang may be formed all along the inside of the ring-shaped element, or be formed only along some portions.

The ring-shaped element can be formed as a single piece, or be formed as two separate parts joined together to form an integral part.

The illumination device may further comprise a transmissive cover structure disposed within the ring-shaped element arranged to cover each LED while allowing light from each LED to be emitted from the illumination device. Such a transmissive cover structure can be adapted to protect the LEDs from the environment, and may also be adapted to provide an optical function. In the latter case, the transmissive cover structure should be in optical contact with the LEDs.

A transmissive cover structure may be divided into a plurality of individual elements, each adapted to cover one or several of said plurality of LEDs. Alternatively, the transmissive structure can be formed by a transmissive material filling a void inside said ring- shaped element.

The illumination device may further comprise a collimating/mixing element arranged to receive light from the LEDs, wherein the ring-shaped element is adapted to serve as a mechanical interface between the carrier and the collimating/mixing element. Such a collimating/mixing element may be adapted to collimate light from the LEDs, and/or to provide color mixing of light from differently colored LEDs.

According to a preferred embodiment said collimating / mixing element is a tubular reflector with a reflective inner surface, the tubular reflector having an entrance aperture and an exit aperture being larger than the entrance aperture; wherein the LED module is arranged to emit light (preferably of different spectral content / different colors) into said tubular reflector at the entrance aperture thereof.

The exit aperture preferably has a cross section adapted to match the cross section of a collimating/mixing element mounted to the illumination device. According to one embodiment, the exit aperture has a polygonal cross section, preferably a rectangular, a square, a pentagonal, hexagonal, heptagonal, or octagonal cross section.

The cross section of the exit aperture does not necessarily match the cross section of the opening defined by the first portion, closest to the carrier. As an example, the first portion can define a circular opening, while the second portion defines a polygonal opening. In this case, the opening in the second portion may lie entirely within the opening in the first portion, or it may coincide with the opening in the first portion in certain points or along certain segments.

It is noted that the invention relates to all possible combinations of features recited in the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing embodiment(s) of the invention.

Figure 1 is a perspective exploded view of an illumination device according to a first embodiment of the present invention.

Figure 2 is a perspective, sectional view of the illumination device in figure 1.

Figure 3 is a perspective view of an illumination device according to a first embodiment of the present invention. DETAILED DESCRIPTION

The illumination device in figure 1-2 comprises a carrier 1, on which a LED module 2 is mounted. The LED module comprises a plurality of LEDs 3, here mounted in groups on rectangular sub-mounts 4. The LED module further comprises driver and control circuitry 5, arranged in between the LED sub-mounts, and wiring to interconnect the circuitry and the LEDs. The LED module may further include sensors, such as temperature and/or light sensors, connected to the control circuitry. In the illustrated example, a plurality of submounts are mounted on a substrate, such as an IMS (insulated metal substrate) or a FR4 substrate.

As an example, the LED module may comprise between 5 and 250 LEDs, and typically between 70 and 150 LEDs. The LED module 2 may include a high densely packed LED array characterized by a high EPI density, preferably between 5 and 70%, more preferably between 15 and 50%.

Each array may further comprise several, for example 2-8, sets of light sources that emit different colors, for example one set of red LEDs, one set of blue LEDs, and one set of green LEDs. According to another example, the light source arrays include LEDs with white (W), red (R), green (G), blue (B) or amber (A), cyan (C), deep red (dR) and/or deep blue (dB) emission spectrum. By combination thereof, any desired light spectrum is obtainable that falls within the color space made up by the color coordinates of the

WRGBAdRdB starting LEDs. Other combinations are also possible, such as neutral white and warm white (NW + WW), combinations with cold white (e.g. CW + WW), (RGBA), (RGB AW), (RGBW), (RGB AC), (RGBAdR), (RGBACdR) and (RGBACdRW).

The illumination device further comprises a ring-shaped element 6, mounted on the carrier 1 so as to surround the LED module 2. As shown in figure 1, the ring 6 has a first proximal portion 7, closest to the carrier 1, and a second distal portion 8 further away from the carrier. The proximal portion 7 defines a first opening, here a circular opening, having a first effective inner diameter dl . This opening is formed to surround the LED module, so that the entire substrate fits within the opening. The distal portion 8 defines a second opening, here a heptagonal opening, having an effective inner diameter d2 which is smaller than the first effective diameter. In other words, the distal portion 8 extends inside the edge of the first opening, at least along some sections of the inner edge of the first opening 7. Along these sections, the distal portion forms an overhang that extends inside the inner edge of the first portion, so as to cover an area 9 immediately inside the first portion 7.

In the illustrated example, the second, heptagonal, opening is formed so that its seven corners coincide with the inner edge of the first, circular, opening.

As shown in figure 2, the ring 6 can be mounted so that peripheral parts of the LED module 2 are located in the area 9, so as to be covered, and protected, by the second portion 8 of the ring 6. As also shown in figure 2, the inner diameter d2 of the second portion 8 is selected such that all LEDs of the LED module are located inside the second portion 8 of the ring 6. The second portion 8 defines an exit aperture 10 of the illumination device.

The ring 6 should have a thickness, in a direction normal to the carrier surface, sufficient to exceed the height of the components of the LED module. At the same time, a relatively flat ring 6 is desirable, in order to minimize shear forces on the ring. Depending on the type of LED module, a suitable thickness may be between 0.5 mm and 10 mm, preferably between 0.7 mm and 5 mm, and most preferably between 0.8 mm and 2 mm. Preferably, the ring is mechanically attached onto the carrier 1.

The inside 11 of the ring 6 is reflective, in order to enhance light emission from the illumination device. According to one embodiment, the entire ring 6 is made of a reflective material, for example a material comprising Titanium oxide. A suitable material could be a polymeric matrix, or a ceramic (e.g. A1203 or the like).

The ring 6 can be in thermal contact with a heat sink (not shown), so as to enhance thermal dissipation from the LEDs. For example, the heat sink may be mounted on the reverse side of the carrier 1.

The LEDs are further, in the illustrated case, covered by a transmissive cover structure, here in the form of individual semi- spherical lenses 12 arranged on each LED 3. The transmissive cover structure may also comprise one or several more complex optical structure(s) with lens shape on the surface such as a microlens array.

The transmissive cover structure may comprise one or several of a transmissive ceramic material, a substantially transmissive glass or polymeric foil material, and a transmissive silicon layer. The transmissive cover structure is preferably in direct contact with the LEDs, for improved optical light outcoupling.

According to one embodiment (not shown), the entire space 13 within the ring 6 is filled with an encapsulant, such as a transparent silicon. The components (LEDs, circuitry, etc) and wire bonds are thus effectively protected against moisture, contamination and unintended damage.

According to the embodiment shown in figure 3, the illumination device further comprises a mixing element in the form of a trumpet shaped parabolic reflector 20 to mix the colors. An example of such a trumpet shaped reflector is described in US 6200002, which is hereby incorporated by reference.

In the embodiment in figure 3, the ring 61 serves as a mechanical and optical interface between the LED module on the carrier and the mixing element. For this purpose, the ring 61 has a broader base 62 that is in contact with the carrier 1, so as to provide a more secure attachment. Further, the ring 61 comprises a reflective sleeve 63 facing the LEDs, which sleeve serves as an interface to the trumpet shaped reflector.

The ring 61 is attached to the carrier 1 by means of fastening elements 64, which also serve to attach the reflector 20 to the ring 61. This provides an integrated unit, comprising the carrier 1, the ring 61 and the reflector 20.

Just as in figure 1-2, the LED module 2 is located inside the ring 61, with parts of its peripheral edges covered by the overhang of the ring 61.

The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For example, the geometry of the ring 6 may be varied, and have different cross section, relative inner diameters, thickness, etc. Further, the LED module may take on a variety of different forms.

Claims

CLAIMS:

1. An illumination device comprising:

a carrier (1),

a LED module (2) arranged on said carrier, said LED module comprising a plurality of LEDs (3), and

an enclosure covering said LED module,

said enclosure including a ring-shaped element (6) surrounding the LED module (2) and in contact with the carrier (1), sides of said ring-shaped element (6) facing said LEDs (3) being reflective,

wherein said ring-shaped element (6) has a first proximal portion (7) arranged closest to said carrier and defining an opening to surround the LED module, and a second, distal portion (8) arranged outside said proximal portion with respect to the carrier and defining an exit aperture of said illumination device,

wherein the exit aperture is smaller than the opening in the proximal portion, so that the distal portion covers a portion (9) of the opening in the proximal portion.

2. The illumination device according to claim 1, wherein the proximal portion (7) has a first effective inner diameter (dl) selected so as to encompass the entire LED module, and said distal portion (8) has a second effective inner diameter (d2), smaller than said first effective inner diameter.

3. The illumination device according to claim 1 or 2, wherein said ring-shaped element (6) is formed as a single piece.

4. The illumination device according to any one of the preceding claims, wherein said ring-shaped element (6) has a thickness, in a direction normal to the carrier surface, between 0.5 mm and 10 mm, preferably between 0.7 mm and 5 mm, and most preferably between 0.8 mm and 2 mm.

5. The illumination device according to any one of the preceding claims, wherein said enclosure further comprises a transmissive cover structure (12) disposed within said ring-shaped element arranged to cover each LED while allowing light from each LED to be emitted from the illumination device.

6. The illumination device according to claim 5, wherein said transmissive structure is arranged in optical contact with each LED.

7. The illumination device according to claim 5 or 6, wherein said transmissive structure is composed of a plurality of individual elements (12), each adapted to cover one or several of said plurality of LEDs.

8. The illumination device according to claim 5 or 6, wherein said transmissive structure is formed by a transmissive material filling a void inside said ring-shaped element.

9. The illumination device according to any one of the preceding claims, further comprising a collimating/mixing element (20) arranged to receive light from said LEDs, wherein said ring-shaped element is adapted to serve as a mechanical interface between said carrier and said collimating/mixing element.

10. The illumination device according to claim 9, wherein said collimating/mixing element is a tubular reflector (20) with a reflective inner surface, the tubular reflector having an entrance aperture and an exit aperture being larger than the entrance aperture.

11. The illumination device according to any one of the preceding claims, wherein the exit aperture has a polygonal cross section.