Lighting device having a light source heat sink arranged separate from a driver

Abstract

A lighting device (1) comprising a driver (7) arranged at a base (2) of the lighting device (1), a heat sink (14) arranged at a portion (3) of the lighting device (1), separate from the driver (7), a light source (13) mounted to the heat sink (14), and a wire (10) arranged to electrically connect the light source (13) to the driver (7), wherein a portion of the wire (10) extending from the base (2) to the portion of the lighting device (1) is arranged to be exposed to light from the light source (13). The present embodiment is advantageous in that the thermal performance is improved and the lifetime of the lighting device (1) is increased. Further, the exposed wire (10) may be illuminated by the light source (13) and visible from outside the lighting device (1), thereby having the appearance of a filament.

Claims

1. A lighting device, comprising: a driver arranged at a base of the lighting device; a heat sink arranged at a portion of the lighting device, separate from the driver; a light source mounted to the heat sink; a wire arranged to electrically connect the light source to the driver; and an envelope arranged to enclose at least the light source and an exposed portion of the wire; a reflector arranged at the base of the lighting device and positioned to reflect light from the light source out of the lighting device, the reflector tapering towards the portion of the lighting device with the heat sink such that the reflector reflects light from the light source out of the envelope in lateral and backward directions relative to a main forwards emission direction of the light source; wherein the wire is arranged separate from the envelope and runs freely from the base to the portion of the lighting device with the heat sink, the wire not contacting the envelope between the base and the portion of the lighting device with the heat sink, and wherein a portion of the wire extending from the base to said portion of the lighting device with the heat sink is arranged to be exposed to light from the light source.

2. The lighting device as defined in claim 1, wherein the exposed portion of the wire is adapted to reflect light from the light source out of the lighting device.

3. The lighting device as defined in claim 1, wherein the reflector extends towards, but not up to, the portion of the lighting device with the heat sink.

4. The lighting device as defined in claim 1, wherein the reflector has a surface structure comprising one or more of: grooves, prisms and a scattering pattern.

5. The lighting device as defined in claim 4, wherein the reflector encloses the driver in a cavity of the base.

6. The lighting device as defined in claim 5, wherein the exposed portion of the wire is at least partly enameled.

7. The lighting device as defined in claim 6, wherein a segment of the exposed portion of the wire is arranged as a coil.

8. The lighting device as defined in claim 7, further comprising an additional heat sink arranged at the base of the lighting device for cooling the driver.

9. The lighting device as defined in claim 8, wherein the portion of the lighting device with the heat sink is arranged opposite to the base.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

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

(2) FIG. 1 shows a lighting device according to an embodiment of the present invention.

(3) FIG. 2 is a cross sectional view of the lighting device shown in FIG. 1.

(4) FIG. 3 is an exploded view of the lighting device shown in FIGS. 1 and 2.

(5) FIG. 4 shows a lighting device according to another embodiment of the present invention.

(6) All the figures are schematic, not necessarily to scale, and generally only show parts which are necessary in order to elucidate the invention, wherein other parts may be omitted or merely suggested.

DETAILED DESCRIPTION

(7) With reference to FIGS. 1-3, a lighting device according to an embodiment of the present invention will be described.

(8) FIGS. 1-3 show a lighting device 1 having a base 2 (or lower portion) and an upper portion 3 opposite to the base 2. At the base 2 of the lighting device 1, a cap 4 (such as a threaded cap) for fitting the lighting device 1 in a lamp fitting and a driver heat sink 5 (also referred to as an additional heat sink in the present disclosure) defining a cavity 6 are arranged. In the cavity 6, a driver 7 for driving a light source 13 of the lighting device 1 (such as a printed circuit board, PCB, driver) is arranged. Preferably, the driver 7 is mounted in the cavity 6 without (or at least with just a small amount of) thermal glue or potting for facilitating assembly as well as recycling of the lighting device 1. The driver heat sink 5 may be made of a material having high thermal conductivity, such as a metal, e.g. aluminum. Alternatively, the driver heat sink 5 may be omitted and a supporting element, of a similar shape and made of e.g. ceramic or plastic, may instead define the cavity 6. Such alternative supporting element is possible since the driver 7 only produces a rather small amount of heat, whereby a heat sink for cooling the driver in some cases may be optional.

(9) The driver 7 is enclosed in the cavity 6 of the base 2 by a reflector 8 having a shape which is tapered towards the upper portion 3 of the lighting device 1. For example, the reflector 8 may be conical. The reflector 8 may preferably be made of plastic (which is cheap, light and easy to shape) or any other thermally insulating material. Further, the upper surface, i.e. the surface of the reflector 8 facing the upper portion 3, is coated with a reflective material, such as a film or layer. In an embodiment, structures for achieving a desired light output profile may be comprised in the reflector 8. In the example shown in FIG. 3, grooves 9 are provided in the reflector for smoothening the light distribution. Alternatively, or as a complement, prism-shapes and/or scattering patterns (not shown) may be provided in the reflector 8.

(10) At the upper portion 3, such as at the top most portion, of the lighting device 1, a heat sink 14 is arranged and, at an underside 15 of the heat sink 14 (i.e. the side 15 of the heat sink 14 facing the base 2 of the lighting device 1), the light source 13 is arranged. The light source 13 (or the PCB at which light source 13 is connected) may be attached onto the heat sink 14 with e.g. glue or screw. The heat sink 14 is adapted to dissipate heat from the light source 13 and may therefore be made of metal (such as aluminum) and may preferably be provided with fins 16 (or ribs) for further improving heat dissipation from the light source 13.

(11) An envelope 12 encloses the interior of the lighting device 1 and reaches at least from the base 2 to the upper portion 3 of the lighting device 1. The envelope 12 may be diffuse (scattering particles may then be enclosed in the envelope 12) or clear, and made of e.g. glass or plastic.

(12) The light source 13 is electrically connected to the driver 7 by a wire 10 running inside the envelope 10 from the driver 7 in the base 2 up to the light source 13 at the upper portion 3. As neither the reflector 8 nor any other component of the lighting device 1 obscures the wire 10, the wire 10 is exposed to light from the light source 13 and may be visible through the envelope 12, in particular if the envelope 12 is clear, from outside the lighting device 1. It will be appreciated that the wire 10 may be visible both if the light source 13 is on or off. As the wire 10 is exposed and hence visible from outside the lighting device 1, the wire 10 may be assimilated as a filament, such as for incandescent lamps. The wire 10 may be arranged separate from the envelope 12 and run freely from the base 2 up to the upper portion 3. Conductors for both current directions (to and from the light source 13) may be included in the same wire 10, whereby a single wire 10 is sufficient (as shown in FIGS. 1-3). However, it will be appreciated that the conductors for the two current directions may be comprised in separate wires, whereby two wires may extend from the driver to the light source 13 (not shown). It is also conceivable that the lighting device may comprise several light sources (not shown), wherein one or more wires may connect the light sources to the driver.

(13) For further improving the resemblance of a filament, at least a part of the exposed portion of the wire 10 may be provided with a coating. The coating may e.g. comprise enamel for slightly reflecting light from the light source 13 out of the lighting device 1. The enamel (or coating) may be transparent, whereby the metal core of the wire 10 is visible. Alternatively, or in combination, the coating may comprise luminescent material, such as yellow/red pigments or dye, for tuning impinging light in respect of color. The wire 10 may then better resemble a glowing filament.

(14) In the present embodiment, the wire 10 runs straight from the base 2 up to the upper portion 3, but it will be appreciated that the wire 10 may have any desired shape.

(15) With reference to FIG. 4, a lighting device according to another embodiment of the present invention will be described.

(16) FIG. 4 shows a lighting device 2 which may be identical to the lighting device 1 described with reference to FIGS. 1-3, except for the shape of the wire 20. In the present embodiment, a segment of the exposed portion of the wire 10 is arranged as a coil 21 for further improving the resemblance to a filament. Further, the conductors for the two current directions between the driver and the light source are comprised in separate wires 20, whereby two wires 20 extend from the driver to the light source.

(17) 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. It should be noted that the above-mentioned embodiments illustrate rather than limit the invention and that those skilled in the art will be able to design alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be constructed as limiting the claim. The word “comprising” does not exclude the presence of elements or steps not listed in a claim. The word “a” or “an” preceding an element does not exclude the presence of a plurality of such elements. The usage of the words first, second and third, etc., does not indicate any ordering. These words are to be interpreted as names. No specific sequence of acts is intended to be required unless specifically indicated.