FOLDED LIGHTING DEVICE WITH LED ARRAY

Abstract

A folded light engine comprising an array of LEDs mounted on a strip substrate, wherein the strip substrate comprises a central portion provided with a first set of through-holes, a first peripheral portion provided with an electrically conducting track connecting a first group of LEDs and a second set of through holes, and a second peripheral portion provided with an electrically conducting track connecting a second group of LEDs. The first peripheral portion is folded over the central portion, so that the LEDs thereon coincide with through-holes in the central portion, and the second peripheral portion is folded over the first peripheral portion, so that each LEDs thereon coincide with a combined through-hole formed by through-holes in the central portion and in the first peripheral portion. An elongated light engine can be cost efficiently manufactured in a relatively simple processes, including single-sided circuit patterning and LED mounting.

Claims

1. A folded light engine comprising an array of LEDs mounted on a strip substrate, wherein the strip substrate comprises a central portion and first and second peripheral portions of substantially equal width and extending in parallel in the longitudinal direction of the strip substrate, the central portion being provided with a first set of through-holes, the first peripheral portion being provided with at least one electrically conducting track, connecting a first group of LEDs mounted on the first peripheral portion, each LED in the first group being aligned with a through-hole in the central portion, the first peripheral portion further being provided with a second set of through holes, each through-hole in the second set being aligned with a through-hole in the first set, the second peripheral portion being provided with at least one electrically conducting track, connecting a second group of LEDs mounted on the second peripheral portion, each LED in the second group being aligned with a through-hole in the first set and with a through-hole in the second set, wherein the first peripheral portion has been folded over the central portion, so that the LEDs mounted on the first peripheral portion coincide with through-holes in the central portion, and through-holes in the first peripheral portion coincide with corresponding through-holes in the central portion, and wherein the second peripheral portion has been folded over the first peripheral portion, so that LEDs mounted on the second peripheral portion coincide with a combined through-hole formed by a through-hole in the central portion and a through-hole in the first peripheral portion.

2. The folded light engine according to claim 1, wherein the first peripheral portion is provided with two separate electrically conducting tacks, each connecting one sub-group of LEDs in the first group.

3. The folded light engine according to claim 1, wherein surfaces of the central portion and surfaces of the first and second peripheral portions are attached to each other after folding.

4. The folded light engine according to claim 1, further comprising an additional peripheral portion, located outside the second peripheral portion, said additional peripheral portion being configured to be folded onto the backside of the central portion.

5. The folded light engine according to claim 1, wherein a protecting sleeve is arranged around the folded substrate.

6. The folded light engine according to claim 5, wherein said protective sleeve is formed by a light transparent foil, wrapped around the folded light engine.

7. The folded light engine according to claim 5, wherein a space between the protecting sleeve and the folded substrate is filled with a curable filler.

8. A multi-light-engine device, comprising a plurality of light engine light engines according to any one of the preceding claims, said light engines being formed on one common substrate, said common substrate further comprising a transversal portion connecting respective ends of the central portions of each light engine.

9. The multi-light-engine device according to claim 8, wherein said transversal portion further is provided with electrically conductive tracks, connecting the tracks of the respective light engines in parallel.

10. The multi-light-engine device according to claim 9, wherein the substrate further comprises flaps extending from the transversal portion and located opposite of each central portion, said flaps being folded over the respective central portion so as to prevent short-circuit.

11. A lighting device comprising at least one folded light engine according to claim 1, and at least two drivers connected in parallel to respective conducting tracks of each folded light engine.

12. The lighting device according to claim 11, further comprising a controller configured to apply a different drive signal to each drive signal line, wherein each drive signal is time varying so as to cause a time variation of at least one property of light emitted from the LED light sources.

13. The lighting device according to claim 11, said multi-light-engine devices each having a shape of a fork, and the light engines of one multi-light-engine device being interleaved with the light engines of another multi-light-engine device.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] 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.

[0037] FIG. 1 shows schematically a distribution of LED light sources of three LED chains.

[0038] FIG. 2 shows an arrangement including a lighting device with a single LED array, according to an embodiment of the present invention.

[0039] FIG. 3 shows an arrangement including a plurality of lighting devices according to an embodiment of the present invention.

[0040] FIGS. 4a-d show schematically manufacture of a folded lighting device according to an embodiment of the present invention.

[0041] FIG. 5 shows a folded lighting device with three rows of LEDs.

[0042] FIG. 6 shows a device with three folded lighting devices according to a further embodiment of the invention.

[0043] FIGS. 7a-c show schematically manufacture of a device with three folded lighting devices according to yet another embodiment of the present invention.

DETAILED DESCRIPTION OF CURRENTLY PREFERRED EMBODIMENTS

[0044] FIG. 1 shows a light area 1 comprising of an array of 9×16 pixels 2. Three non-pixelated LED chains 3a, 3b, 3c, each including 48 LED light sources (nodes) 4 have been deployed to address all the pixels 2 in the array. The assignment of each pixel 2 to a node 4 in a given LED string (3a, 3b or 3c) is random (i.e. not systematic), and as a result the nodes 4 of each LED chain are spread out substantially evenly (similar sparsity) across the entire area in a non-symmetrical (or non-regular) manner. The randomized positions of the light sources 4 in FIG. 1 can for example be routed onto a PCB, with the electric tracks providing the intended allocation of each pixel to a given LED chain.

[0045] The distribution of pixels (i.e. possible locations of light nodes) may be regular (e.g. a rectangular grid) or irregular (e.g. Voronoi, polygonal or hexagonal arrays). The distribution may further exhibit gradients and/or local variation in density (the number of light nodes per area temporarily increases and/or decreases) with the local density variation being either uniform and/or non-uniform in nature (e.g. mix of coarse and fine meshes).

[0046] FIG. 2 shows a light engine 10, including a linear array 11 of LED light sources 12, belonging to a plurality (here three) randomly nested LED chains. The three LED chains are each connected to a LED chain driver 13a, 13b, 13c, which each driver being configured to generate drive waveforms. All LED light sources (nodes) 12 of a particular LED chain are driven by the same drive waveform(s).

[0047] The drivers 13a, 13b, 13c are in turn connected to a controller 14 arranged to control the light emission of all LED chains in the light engine 10. The controller 14 may be a microcontroller running a suitable control program. The controller 14 (e.g. the computer program running on a microcontroller) and the drivers are together capable of providing a well-controlled natural light effect, comprising transitions between different intensities, colors, hue, frame rate, etc. The randomized assignment of light source location enables change of scene and content while maintaining a natural and non-looped experience.

[0048] Each driver 13a-c may be controlled to provide a unique waveform, Alternatively, the output from one single driver (waveform generator) is time shifted to provide a set of different drive signals for driving a set of LED chains differently.

[0049] By arranging a plurality of light engines 10 in parallel (each with a unique random nesting of LED chains), a larger light area as shown in FIG. 1 may be obtained. In principle, each light engine 10 could be provided with individual controllers 13a-c as shown in FIG. 2. Alternatively, and as shown in FIG. 3, the drivers 13a-c are connected in parallel to a plurality of light engines 10 (FIG. 3 shows five light engines).

[0050] FIG. 4a-4d illustrates how a folded light engine 10 may be manufactured from a single, flexible, elongated substrate strip 20. The substrate 20 may for example be made of a foil material kept on a roll. The substrate is further configured to allow printing of circuit tracks and surface mounting of electrical components. The substrate strip 20 comprises a plurality, here three, parallel and equally wide portions 20a, 20b, 20c extending along the entire length of the substrate. The portions 20a-c may be separated by perforations or folding lines 21, to facilitate folding as will be discussed below. The substrate portions 20a-c may generally have optical properties suitable for a specific application, and may for example be (semi-) transparent, colored, diffuse, reflective or structured. The substrate may be co-extruded, allowing different portions to have different properties. For example, the substrate may have a light transparent central portion 20b, and a reflective peripheral portion 20a.

[0051] The center portion 20b is further provided with a first set of through-holes 22. In the illustrated example, the through holes 22, 22′ are equidistantly distributed along the portion 20b. The function of the through-holes 22, 22′ will be discussed in more detail below. However, in addition to their function in the light engine 10, the through holes 22, 22′ may also be useful in the manufacturing process, and may serve to allow a chain-paper-type controlled guidance of the substrate.

[0052] The first peripheral portions, here portion 20a, is provided with a second set of through-holes 23, fewer in number than the through holes 22. In the illustrated case, the first set includes four through holes 22, 22′, while the second set includes only one through-hole 23.

[0053] A first group of LEDs 24a, 24b are mounted on the first peripheral portion, and connected by electrically conducting tracks 25a, 25b. In the illustrated case, the first group of LEDs includes two sub-groups of LEDs 24a and 24b, each connected by separate tracks 25a and 25b. The two sub-groups thus form two LED-chains which may be individually controllable by different drive signals.

[0054] In a similar manner, a second group of LEDs 26 are mounted on the second peripheral portion 20c, and connected by electrically conducting tracks 27. This second group of LEDs 26 forms a third LED-chain, individually controllable by a different drive signal than the first group of LEDs 24a, 24b.

[0055] In practice, it may be advantageous to first provide the circuit tracks 25a, 25b and 27 in a circuit patterning process. The tracks preferably include connection pads (solder pads) in the location where the LEDs 24a, 24b and 26 are to be mounted. Then, when the tracks have been printed, the LEDs 24a, 24b, 26 are mounted in a surface mounting process. It is noted that the circuit patterning and surface mounting processes are facilitated by the fact that all tracks and LEDs are located on the same side of the substrate 20.

[0056] The holes 23 and LEDs 24a, 24b in the first peripheral portion 20b are aligned with the holes 22, 22′ in the center portion, such that, when the first peripheral portion 20a is folded over the center portion 20b, as shown in FIG. 4b, the holes 23 and LEDs 24a, 24b will each coincide with one of the holes 22, 22′. Further, the LEDs 26 on the second peripheral portion 20c (here only one) are aligned with the holes 23 in the first peripheral portion 20a, such that, when the second peripheral portion 20c is folded over the center portion 20b and the first peripheral portion 20a, as shown in FIG. 4c, the LEDs 26 will each coincide with a combined hole 28 formed by a through-hole 22′ in the central portion 20b and a through-hole 23 in the first peripheral portion 20a.

[0057] When both peripheral portions 20a, 20c have been folded over the central portion 20b, all LEDs 24a, 24b, 26 will thus be visible from the other side of the light engine 10, as shown in FIG. 4d. The separate tracks 25a, 25b and 27, and their respective nested LED-chains, may now be connected to different drive signals, e.g. by means of drivers 13a-c as shown in FIG. 2.

[0058] In the folded state of the light engine 10, the LEDs 24a, 24b, 26 will be protected by the folded portions 20a, 20b, 20c of the substrate, preventing electrical and mechanical access. To even further enhance this effect, the substrate portions 20a-c are preferably attached and sealed to each other, at least locally. Sealing may be achieved in various ways, including adhesive or spot-welding. Alternatively, the substrate is formed of a heat-sealable foil, allowing the folded light engine 10 to be heat-sealed.

[0059] Although not shown in FIG. 4a-d, an additional sealing portion may be provided along the outside the second peripheral portion 20c, and be folded around the folded light engine onto the backside of the central portion. Such a sealing portion may be formed by the same (non-transparent) substrate as the other portions 20a-c, in which case it preferably is sufficiently narrow so that it will not obstruct the LEDs in the through holes.

[0060] Another alternative is to form this sealing portion of a light transparent foil, in which it can extend over the through holes and the LEDs thereunder, so as to shield the LEDs from direct/mechanical access, to prevent debris and contaminants to reach the LEDs and circuit tracks, or simply to provide a water tight barrier/envelope. Such a transparent foil may be co-extruded and form part of the substrate 20, or be formed as a separate piece.

[0061] The transparent foil may be wide enough to extend fully around the folded light engine, thus providing a fully sealed envelope around the light engine. In fact, such a transparent foil may extend more than one turn around the light engine, to even further increase the protective effect. In this case, however, the foil is preferably provided with through holes matching the holes 22, 22′, 23 in each layer except the final layer. This is because each layer causes some Fresnel reflection at the foil's surface, resulting in a reduced light output when compared to no covering foil.

[0062] The total number of LEDs 24a, 24b, 26 corresponds to the number of holes 22, 22′ in the first set of through-holes, so four in this case. In reality, there would typically be a larger number of holes 22, 22′, e.g. more than 10, more than 20, or even more than 50, and a corresponding number of LEDs 24a, 24b, 26.

[0063] Each separate LED-chain preferably includes roughly the same number of LEDs. In the illustrated example, where the first peripheral portion 20a comprises two separate chains of LEDs 24a, 24b, the number of holes 23 in the first peripheral portion 20a, and thus the number of LEDs 26 on the second peripheral portion 20c, is preferably around one third of the number of holes 22, 22′ (or, put differently, around half of the number of LEDs 24a, 24b on the first peripheral portion 20a).

[0064] In FIGS. 4a-d the central portion 20b has one single row of holes 22, 22′, and the complete light engine thus has one single row of LEDs 24a, 24b, 26. It is noted that the central portion may equally well have several (e.g. three) rows of holes 22, 22′, and the LEDs 24a, 24b, 26 may be aligned with holes in all rows. FIG. 5 gives an example of a lighting device manufactured according to the principles of FIGS. 4a-d, but with three rows of LEDs.

[0065] With reference to FIG. 6, several lighting devices 10 arranged in parallel may be manufactured from one single substrate 30. As shown in FIG. 6, the substrate 30 here has three sets of parallel portions 30a, 30b, 30c, each corresponding to the portions 20a, 20b, 20c in FIG. 4a, to allow forming three lighting devices 10. The three central portions 30b are connected in their respective ends by two transversal portions 31a, 31b, to form a ladder-like shape. One of the transversal portions 30a is provided with printed circuit tracks 35 connecting the tracks 25a, 25b, 27 (27 is not shown in FIG. 6) on the respective devices 10 in parallel. Three drive signals may now be connected to all lighting devices together, e.g. by connecting three drivers 13a-c as shown in FIG. 3.

[0066] When the light engine 10 is intended to be used in a lighting device as discussed in the application titled “Lighting device for providing a natural lighting effect” filed on the same date as the present application, the distribution of LEDs, i.e. the nesting of the separate LED-chains, is irregular, or randomized. In other words, each light engines 10 in FIG. 6 will have a unique distribution of LEDs, and the plurality of light engines 10 will form a light area having three nested LED-chains with LEDs substantially evenly and non-symmetrically distributed over the light area.

[0067] FIGS. 7a-7c show a further example of manufacturing a plurality of lighting devices 10 from a single substrate. Similar to the substrate in FIG. 6, the substrate 40 in FIG. 7a includes three sets of parallel portions 40a, 40b, 40c. In this case, however, the center portions 40b are connected by a transversal portion 41 only on one side, so as to form a device 42 in the shape of a fork when folded, as shown in FIG. 7b. Similar to FIG. 6, the transversal portion 41 is provided with printed circuit tracks 45 connecting the tracks 25a, 25b, 27 on the respective devices 10 in parallel. In the illustrated example, the central portions 40b are provided with circuit tracks 46 which connect the tracks 45 on the transversal portion with the tracks 25a, 25b and 27. As shown in FIG. 7c, two forks 42, each with a plurality of lighting devices 10, may be interleaved.

[0068] The substrate 40 is further provided with flaps 47, extending from the transversal portion 41, and located opposite of each central portion 40b. As shown in FIG. 7b, the flaps 46 are folded over the end 48 of the central portions 40b, before the peripheral portions 40a, 40c are folded over the central portion 40b. The flaps 47 serve to isolate circuit tracks 46 on the central portion 40b, and to avoid any short-circuit caused when folding the peripheral portions 40a, 40c. It is noted that such flaps 47 may be provided also in the embodiments in the previous figures.

[0069] 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 appropriate number of LED chains in each group may be different. Further, the density of the LED chain or group of LED chains may be either uniform or non-uniform for a portion of a light area.

[0070] Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.