WO2014195891A1

WO2014195891A1 - Lighting device and luminaire

Info

Publication number: WO2014195891A1
Application number: PCT/IB2014/061966
Authority: WO
Inventors: Xiao Qiao ZHANG; Yan Xiong
Original assignee: Koninklijke Philips N.V.
Priority date: 2013-06-08
Filing date: 2014-06-05
Publication date: 2014-12-11

Abstract

Disclosed is a lighting device (10) comprising a tubular body (100) having an inner volume and a carrier (110) in said inner volume, the carrier comprising a first section (112) carrying a first plurality of solid state lighting elements (132) and a second section (116) carrying a second plurality of solid state lighting elements (142), wherein the first section and the second section are in different planes. A luminaire comprising such a lighting device (10) is also disclosed.

Description

LIGHTING DEVICE AND LUMINAIRE

FIELD OF THE INVENTION

The present invention relates to a lighting device comprising a tubular body having an inner volume housing a plurality of solid state lighting elements.

The present invention further relates to a luminaire comprising such a lighting device.

BACKGROUND OF THE INVENTION

With a continuously growing population, it is becoming increasingly difficult to meet the world's energy needs as well as to control carbon emissions to kerb greenhouse gas emissions that are considered responsible for global warming phenomena. These concerns have triggered a drive towards a more efficient use of electricity in an attempt to reduce energy consumption.

One such area of concern is lighting applications, either in domestic or commercial settings. There is a clear trend towards the replacement of traditional energy-inefficient light bulbs such as incandescent or fluorescent light bulbs with more energy efficient replacements. Indeed, in many jurisdictions the production and retailing of incandescent light bulbs has been outlawed, thus forcing consumers to buy energy-efficient alternatives, e.g. when replacing incandescent light bulbs.

A particular promising alternative is provided by solid state lighting (SSL) devices, which can produce a unit luminous output at a fraction of the energy cost of incandescent light bulbs. An example of such a SSL element is a light emitting diode.

A drawback of SSL element-based lighting devices is that the compatibility with incandescent light-based device fittings, e.g. luminaires, is not perfect, which hampers the market penetration of the SSL element-based lighting devices. SSL element-based lighting devices typically require one or more driver circuits for driving the SSL elements, which when integrated in the lighting device can compromise the internal volume available for luminous output, i.e. for the SSL elements. This is for instance problematic in tubular lighting devices based on SSL elements such as tubular light bulbs in which the driver circuit is typically located inside the tube towards an end portion of the tube, e.g. adjacent to an end cap of the tube for connecting the tube into the fitting of a luminaire. An example of such an arrangement is disclosed in CN 101893178 A. The absence of SSL elements in such an end segment of the tubular lighting device gives the end segments of the lighting device a dark appearance, which renders the SSL elements-based tubular lighting device aesthetically inferior compared to traditional tubular light bulbs such as fluorescent light bulbs.

SUMMARY OF THE INVENTION

The present invention seeks to provide a lighting device according to the opening paragraph that facilitates the production of a luminous output over the full width of the tubular body of the lighting device.

The present invention further seeks to provide a luminaire comprising such a lighting device.

In accordance with an aspect of the present invention, there is provided a lighting device comprising a tubular body having an inner volume and a carrier in said inner volume, the carrier comprising a first section carrying a first plurality of solid state lighting elements and a second section carrying a second plurality of solid state lighting elements, wherein the first section and the second section are in different planes.

The provision of a carrier having sections in different planes, i.e. having one section elevated in respect of the other section, creates a volume portion of the inner volume that is delimited by the elevated portion of the carrier and a section of the inner wall of the tubular body. This volume portion is excluded from the optical path of the luminous output of the SSL elements, e.g. inorganic or organic light emitting diodes (LEDs), such that this volume portion can be utilized to house additional components inside the tubular body without compromising the luminous output of the lighting device. Advantageously, the lighting device may further comprise a first end cap at a first end of the tubular body, wherein said carrier extends from the first end cap to a second end of the tubular body opposite said first end. Consequently, the full length of the lighting device is utilized for the generation of luminous output, thus improving the appearance of the lighting device.

In an embodiment, the carrier has a stepped profile, the first section and second section defining respective steps of said profile. This allows for a straightforward and cost-effective way to provide such a carrier in the lighting device.

The lighting device preferably further comprises a first driver circuit for driving at least some of said solid state lighting elements, wherein said first driver circuit is placed in a first volume portion of the inner volume delimited by the tubular body and the first section. This provides a lighting device with integrated driver circuit in which the volume occupied by the driver circuit does not affect the luminous output area of the lighting device.

In an embodiment, the first section extends from a first end of the tubular body, said first driver circuit being supported by a first end cap at said first end. This provides a lighting device that can be easily assembled and in which the first driver circuit is securely fitted to the first end cap, thus providing a robust and cost-effective lighting device.

The lighting device may further comprise a first end cap at a first end of the tubular body wherein said first section extends from the first end cap, the carrier further comprising a third section in the same plane as the first section, the third section carrying a third plurality of solid state elements and being separated from the first section by the second section, wherein the lighting device further comprises a second end cap at a second end of the tubular body, said third section extending from said second end cap. This for instance allows for the placement of an additional component in the inner volume portion delimited by the inner wall of the tubular body and the third section of the carrier.

The lighting device may for instance further comprise a second driver circuit for driving at least some of said solid state lighting elements, wherein said second driver circuit is placed in a second volume portion of the inner volume delimited by the tubular body and the third section, said second driver circuit being supported by said second end cap.

In an embodiment, the carrier is a heat sink for the SSL elements. The heat sink may advantageously be formed from a pliable metal sheet such as an aluminium sheet, which allows for the formation of the different sections in a straightforward manner.

The first plurality of solid state lighting elements may be located on a first printed circuit board (PCB) mounted on the first section and the second plurality of solid state lighting elements may be located on a second printed circuit board mounted on the second section. The use of separate PCBs simplifies the design of the lighting device such that the lighting device can be produced in a particularly cost-effective manner.

The heat sink may further comprise an intermediate section connecting the first section to the second section, said intermediate section comprising an opening. This opening may for instance be utilized to facilitate the connection of the second plurality of SSL elements to a driver circuit underneath the first section.

In an embodiment, at least the first section and the second section of the carrier have curved side walls. This allows for a straightforward fit of the carrier in the tubular body. Preferably, the curved side walls of at least the second section have a constant radius matching the radius of the inner wall of the tubular body.

This optimizes the thermal coupling between the second section and the tubular body, thus optimizing the heat dissipation of the lighting device. The curved side walls may extend from a planar central portion, which has the advantage that the

SSL elements can be fitted to the carrier in a straightforward manner, e.g. using circuit boards with planar surfaces.

Preferably, the first section carries a higher density of solid state lighting elements than the second section. It is known per se that SSL elements in close vicinity of the tubular body can create luminous spots on its luminous surface due to the fact that the limited distance between the luminous surface of the SSL elements and the tubular body prevents overlap of the luminous output of neighbouring SSL elements. This problem is addressed by increasing the density of the first plurality of SSL elements to such an extent that such separate spots are no longer formed. It is noted that because the majority of SSL elements will be located on the second section that is spaced apart further from the light exit surface of the tubular body, there is no need to increase the density of the second plurality of SSL elements on the second section. Consequently, the additional heat generated by the higher density of SSL elements on the first section is limited and can be dissipated by the lighting device without causing overheating.

In accordance with another aspect of the present invention, there is provided a luminaire comprising the lighting device according to an embodiment of the present invention. Such a luminaire may for instance be a holder of the lighting device or an apparatus into which the lighting device is integrated.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in more detail and by way of non- limiting examples with reference to the accompanying drawings, wherein

FIG. 1 schematically depicts a cross section of a lighting device according to an embodiment of the present invention;

FIG. 2 schematically depicts a cross section of an aspect of the lighting device of FIG.1 ;

FIG. 3 schematically depicts another cross section of an aspect of the lighting device of FIG.1 ;

FIG. 4 schematically depicts a cross section of a lighting device according to another embodiment of the present invention; and

FIG. 5 schematically depicts a cross section of a lighting device according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

FIG. 1 schematically depicts a cross section in a length direction of a tubular lighting device 10. The lighting device 10 comprises a tubular body 100 having an inner volume in which a carrier 1 10 is fitted. The tubular body 100 may be made of any suitable material, e.g. glass or a suitable polymer such as polycarbonate or PMMA and may be transparent or translucent, e.g. clouded, to allow light to exit the lighting device 10. The carrier 1 10 comprises a first section 1 12 carrying a first plurality of SSL elements 132 mounted on a first circuit board 130 and a second section 1 16 carrying a second plurality of SSL elements 142 mounted on a second circuit board 130. Alternatively, each SSL element of the first plurality of SSL elements 132 and the second plurality of SSL elements 142 may be mounted individually on the first section 1 12 and the second section 1 16 respectively of the carrier 1 10. The SSL elements in the lighting device 10 may be LEDs, e.g. organic or inorganic LEDs.

The carrier 1 10 preferably acts as a heat sink for the first plurality of SSL elements 132 and the second plurality of SSL elements 142. The carrier 1 10 preferably is made of a material having good heat conductive properties, e.g. a metal. Aluminium is particularly preferred as it is pliable such that the carrier 10 can be easily molded, e.g. extruded, into its desired shape.

The first section 1 12 of the carrier 1 10 is in a different plane to the second section 1 16. In other words, the first section 1 12 is located on or near the longitudinal axis of symmetry of the tubular body 100, whereas the second section 1 16 is located on or near the inner wall of the tubular body 100. Hence, the plane of the second section 1 16 is axially displaced in respect of the plane of the first section 1 12. This creates a first volume portion or cavity inside the tubular body 100 that is delimited by a wall section of the tubular body 100, by the first section 1 12 and by an intermediate section 1 14 of the carrier 1 10 that interconnects the first section 1 12 and the second section 1 16. The first volume portion or cavity underneath the first section 1 12 of the carrier houses a component such as a first driver circuit 160 for driving at least some of the first plurality of SSL elements 132 and the second plurality of SSL elements 142. FIG. 2 schematically depicts a cross section of the lighting device 10 along the plane A in FIG. 1. As can be seen in FIG. 2, the first driver circuit 160 is fitted in between the first section 1 12 of the carrier 1 10 and a wall portion of the tubular body 100. A first SSL element 132 on the first circuit board 130 (or on the first segment 112 as previously explained) has a luminous surface facing the tubular body 100 and has a clearance H1 between its luminous surface and the uppermost portion of the tubular body 100. The first driver circuit 160 may comprise one or more connectors 162 for engaging with a first end cap 102 of the tubular body 100. In an embodiment, the driver circuit 160 comprises one or more pins 162 that fit into opposite sockets on the first end cap 102. Alternatively, the first driver circuit 160 comprises one or more sockets 162 for receiving opposite pins of the first end cap 102. The engagement between the first driver circuit 160 and the first end cap 102 aids in securing the first driver circuit 160 inside the tubular body 100. It should be understood that further securing measures, e.g. screws, clips, an adhesive and so on may be used to further secure the first driver circuit 160 inside the tubular body 100.

FIG. 3 schematically depicts a cross section of the lighting device 10 along the plane B in FIG. 1. As can be seen in FIG. 3, the second portion 1 16 of the carrier 1 10 is located on a different plane in the tubular body 100 compared to the first portion 1 12 of the carrier 1 10 such that a second SSL element 142 on the second circuit board 140 (or on the second segment 1 16 as previously explained) has a luminous surface facing the tubular body 100 and has a clearance H2 between its luminous surface and the uppermost portion of the tubular body 100. In embodiments of the present invention, H1 is smaller than H2 as a consequence of the first portion 1 12 and the second portion 1 16 being located in different planes.

In an embodiment, the second section 1 16 has curved side walls 304 to create a good fit between the side walls 304 of the second section 1 16 and the tubular body 100. The curved side walls 304 preferably extend from a planar central portion 302 for supporting the circuit board 140 or the SSL elements 142 directly as previously explained. The curved side walls 304 may have a constant radius matching the radius of the inner wall of the tubular body 100 to establish an intimate contact between the second section 1 16 and the inner wall of the tubular body 100. This promotes heat transfer between the second section 1 16 and the tubular body 100, thereby increasing the efficiency of the dissipation of the heat generated by the SSL elements inside the tubular body 100.

The first section 112 shown in FIG. 2 may also have such curved side walls 204 preferably extending from a planar central section 202; this has the advantage that the carrier 1 10 can be manufactured in a straightforward manner, e.g. by metal extrusion, as it has a uniform overall shape. For the avoidance of doubt it is noted that where the present application refers to the planes of the various sections of the carrier 100, reference is made to the planar central portions 202 and 302 in the present embodiment. However, it should be understood that although the carrier 1 10 preferably has curved side walls, such as curved side walls of constant radius, it is equally feasible to fit a carrier 1 10 of different shapes, e.g. having a planar shape, in the tubular body 100 of the lighting device 10.

Upon returning to FIG. 1 , in an embodiment the intermediate section 1 14 comprises an opening providing access to the second plurality of SSL elements 142. For instance, as shown in FIG. 1 , the second circuit board 140 may extend into the first volume portion through this opening, such that the connections, e.g. wiring, from the first driver circuit 160 to the second circuit board 140 may be provided inside the first volume portion. Alternatively the wiring from the first driver circuit 160 to the second circuit board 140 may be fed through the opening in the intermediate section 1 14 in case the second circuit board 140 does not extend through this opening. Other suitable arrangements will be apparent to the skilled person.

In an embodiment, the carrier 1 10 further comprises a third section 1 12' that lies in a different plane to the second section 1 16 and is connected to the second section 1 16 via a further intermediate section 1 14'. The third section 1 12' may lie in the same plane as the first section 1 12. The third section 1 12' supports a third plurality of SSL elements 152, e.g. organic or inorganic LEDs, which may be mounted on a third circuit board 150 or directly on the third section 1 12' as previously explained in the context of the first plurality of SSL elements 132.

A component such as a second driver circuit 170 may be placed in the second volume portion of the inner volume of the tubular body 100, which second volume portion is delimited by the third section 1 12', the further intermediate section 1 14' and a further wall portion of the tubular body 100. The second driver circuit 170 may be supported by a second end cap 104 at a second end of the tubular body 100 opposite its first end as previously explained in respect of the first driver circuit 160 and the first end cap 102. For instance, the second driver circuit may have one or more pins or sockets 172 for engaging with sockets or pins respectively of the second end cap 104. It should be understood that further securing measures, e.g. screws, clips, an adhesive and so on may be used to further secure the second driver circuit 170 inside the tubular body 100. In an embodiment, the first driver circuit 160 is arranged to drive the first plurality of SSL elements 132 and part of the second plurality of SSL elements 142, whereas the second driver circuit 170 is arranged to drive the third plurality of SSL elements 152 and the other part of the second plurality of SSL elements 142. Other arrangements are of course equally feasible.

As with the intermediate section 1 14, the further intermediate section 1 14' may contain a further opening providing access to the second plurality of SSL elements 142. For instance, as shown in FIG. 1 , the second circuit board 140 may extend into the second volume portion through this opening, such that the connections, e.g. wiring, from the second driver circuit 170 to the second circuit board 140 may be provided inside the second volume portion. Alternatively the wiring from the second driver circuit 170 to the second circuit board 140 may be fed through the further opening in the further intermediate section 1 14' in case the second circuit board 140 does not extend through this opening. Other suitable arrangements will be apparent to the skilled person. Because the first plurality of SSL elements 132 and the third plurality of SSL elements 152 near the end portions of the tubular body 100 are located nearer to the light exit surface of the tubular body 100, as indicated by clearance H1 in FIG. 2, the pitch of the first plurality of SSL elements 132 and the third plurality of SSL elements 152 is smaller than the pitch of the second plurality of SSL elements 142, as can be seen in FIG. 1 . In other words, the first section 1 12 and the third section 1 12' of the carrier 1 10 carry a higher density of SSL elements than the second section 1 16. The SSL elements of the first plurality of SSL elements 132 and the third plurality of SSL elements 152 are placed closer together, i.e. at a smaller pitch, to avoid spotting on the light exit surface portion of the tubular body 100 caused by incomplete mixing of the luminous output of neighbouring SSL elements in relatively close vicinity to the light exit surface portion of the tubular body 100.

In an embodiment, the length of the second section 1 16 is larger than the length of the first section 1 12 and the third section 1 12' of the carrier 1 10 such that the second section 116 carries a higher number of SSL elements than each of the first section 1 12 and the third section 1 12' of the carrier 1 10. Consequently, the majority of the SSL elements, i.e. the second plurality of SSL elements 142, are further spaced apart than the minority of SSL elements, i.e. the first plurality of SSL elements 132 and the third plurality of SSL elements 152, which is beneficial in terms of heat dissipation by the carrier 1 10 and the tubular body 100.

At this point it is noted that the presence of the third section 1 12' of the carrier 1 10 in the tubular body 100 is optional. It is equally feasible to limit the number of sections of the carrier 100 to two, i.e. the first section 1 12 and the second section 1 16 only. This embodiment is shown in FIG. 4. This is for instance feasible if the first driver circuit 160 is capable of driving the first plurality of SSL elements 132 and the second plurality of SSL elements 142. In this embodiment, the second section 1 16 of the carrier 1 10 extends to the second end portion of the tubular body 100. In this embodiment, the second end cap 104 may be present or may be omitted instead. It should be understood that from an ease of manufacturing perspective it is preferable to place the one or more components, e.g. first driver circuit 160 and optionally the second driver circuit 170 at the (opposite) end portion(s) of the tubular body 100 as shown in FIG. 1 and 4 respectively. However, it is equally feasible to provide such components in a central section of the tubular body, as is shown in FIG. 5. Here, the second section 116 is located in the same plane as the first section 1 12 in FIG. 1 , whereas the first section 1 12 and the third section 1 12' respectively are located in the same plane as the second section 1 16 in FIG. 1 , such that the first volume portion housing the one or more components such as first driver circuit 160 and second driver circuit 170 is delimited by the second section 1 16, the intermediate section 1 14, the further intermediate section 1 14' and a portion of the tubular body 100. Wiring 164 and 174 may be provided to connect the first driver circuit 160 and the second driver circuit 170 to the first end cap 102 and the second end cap 104 respectively. Because the second plurality of SSL elements 142 is now in closer vicinity to the light exit surface portion of the tubular body 100 compared to the first plurality of SSL elements 132 and the third plurality of SSL elements 152, the second section 1 16 carries a higher density of SSL elements than the first section 1 12 and the third section 1 12' to avoid spotting issues as previously explained.

The lighting device 10 according to embodiments of the present invention may be advantageously included in a luminaire such as a holder of the lighting device, e.g. a ceiling light fitting, an armature for fitting underneath a cabinet or the like, an apparatus into which the lighting device is integrated, e.g. a cooker hood or the like, and so on.

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 many alternative embodiments without departing from the scope of the appended claims. In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps other than those listed in a claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The invention can be implemented by means of hardware comprising several distinct elements. In the device claim enumerating several means, several of these means can be embodied by one and the same item of hardware. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

1. A lighting device (10) comprising a tubular body (100) having an inner volume and a carrier (1 10) in said inner volume, the carrier comprising a first section (1 12) carrying a first plurality of solid state lighting elements (132) and a second section (116) carrying a second plurality of solid state lighting elements (142), wherein the first section and the second section are in different planes.

2. The lighting device (10) of claim 1 , further comprising a first end cap (102) at a first end of the tubular body (100) wherein said carrier (1 10) extends from the first end cap to a second end of the tubular body opposite said first end.

3. The lighting device (10) of claim 1 or 2, wherein the carrier (1 10) has a stepped profile, the first section (112) and second section (1 16) defining respective steps of said profile.

4. The lighting device (10) of any of claims 1 -3, further comprising a first driver circuit (160) for driving at least some of said solid state lighting elements (132, 142), wherein said first driver circuit is placed in a first volume portion of the inner volume delimited by the tubular body (100) and the first section (1 12).

5. The lighting device (10) of claim 4, wherein the first section (1 12) extends from a first end of the tubular body (100), said first driver circuit (160) being supported by a first end cap (102) at said first end.

6. The lighting device (10) of any of claims 1 -4, further comprising a first end cap (102) at a first end of the tubular body (100) wherein said first section (1 12) extends from the first end cap, the carrier (1 10) further comprising a third section (1 12') in the same plane as the first section (1 12), the third section carrying a third plurality of solid state elements (152) and being separated from the first section by the second section (1 16), wherein the lighting device further comprises a second end cap (104) at a second end of the tubular body (100), said third section extending from said second end cap.

7. The lighting device (10) of claim 6, further comprising a second driver 5 circuit (170) for driving at least some of said solid state lighting elements (142, 152), wherein said second driver circuit is placed in a second volume portion of the inner volume delimited by the tubular body (100) and the third section (1 12'), said second driver circuit (170) being supported by said second end cap (104). o

8. The lighting device (10) of any of claims 1 -7, wherein the carrier (1 10) is a heat sink.

9. The lighting device (10) of claim 8, wherein the heat sink is formed from an aluminium sheet.

5

10. The lighting device (10) of claim 8 or 9, wherein first plurality of solid state lighting elements (132) is located on a first printed circuit board (130) mounted on the first section (1 12) and the second plurality of solid state lighting elements (142) is located on a second printed circuit board (140) mounted on the second0 section (1 16).

1 1 . The lighting device (10) of claim 10, wherein the heat sink comprises an intermediate section (1 14) connecting the first section (1 12) to the second section (1 16), said intermediate section comprising an opening.

5

12. The lighting device (10) of any of claims 1 -1 1 , wherein at least the first section (1 12) and the second section (116) of the carrier (1 10) have curved side walls (204, 304). 0

13. The lighting device (10) of claim 12, wherein said curved side walls (204, 304) extend from a planar central portion (202, 302).

14. The lighting device (10) of any of claim 1 -13, wherein the first section (1 12) carries a higher density of solid state lighting elements than the second section (1 16).

15. A luminaire comprising the lighting device (10) of any of claims 1 -14.