Lighting system using light bars

Abstract

A lighting system comprises a plurality of spaced of light bars (22) each having first and second connection pads (26a, 26b) for receiving electrical power. An interconnecting strip (30) extends across the light bars (22) for providing electrical power connections to the connection pads (26a, 26b). The interconnecting strip (30) comprises a first line (32a) of connection terminals (34) extending along a first edge and a second line (32b) of connection terminals (34) extending along an opposite second edge, wherein the pitch (p1) between connection terminals (34) is smaller than a pitch (p2) between the light bars (22). The first and second lines of connection terminals (34) each form a toothed structure. This provides flexibility in the spacing of the light bars.

Description

[0001] Lighting system using light bars

[0002] FIELD OF THE INVENTION

[0003] This invention relates to lighting systems which use light bars, in particular lighting system in the form of a lighting panel comprising a set of light bars.

[0004] BACKGROUND OF THE INVENTION

[0005] Panel lighting is used in various lighting applications and is for example the most common luminaire type for office lighting. One luminaire architecture uses a dot-lens based light engine, comprising lines of LEDs, each with an associated lens. These lines of LEDs are formed as light bars, and they are electrically connected to form a 2D array of LEDs.

[0006] The light bars are placed with a certain spacing to achieve a homogenous light effect to an exit window of the luminaire. For example, a 60cm x 60cm exit window is common for office panel luminaires. A flexible or rigid printed circuit is used to connect the light bars and thus functions as an interconnecting strip. Solder pads are provided along the interconnecting strip with a fixed pitch, such as 80.5mm.

[0007] However, for different lighting purposes, such as to configure a different light flux or efficacy, or to fit different sizes of housings, the light bars may be placed with a different spacing, for example to provide more light bars in a given housing, or for a different size of housing. For example, a standard luminaire may use six light bars, while eight light bars may be used for a high efficacy version.

[0008] The original interconnecting strip cannot then be used because of the changed spacing between the connections.

[0009] SUMMARY OF THE INVENTION

[0010] The invention is defined by the claims.

[0011] According to examples in accordance with an aspect of the invention, there is provided a lighting system comprising: a plurality of light bars, each comprising an array of lighting units arranged on each light bar, wherein the light bars are arranged side-by-side with each other with a spacing between them, wherein each light bar comprises first and second connection pads for receiving electrical power; and a flexible interconnecting strip extending across the light bars for providing electrical power connections to the connection pads of the light bars, wherein the interconnecting strip comprises a first line of connection terminals extending along a first edge and a second line of connection terminals extending along an opposite second edge, wherein the first and second lines of connection terminals each form a toothed structure, wherein a pitch between connection terminals, in a length direction of the interconnecting strip, is smaller than a pitch between the light bars, and wherein the first and second connection pads of the light bars are each for soldering to connection terminals of the first and second lines of connection terminals respectively.

[0012] This lighting system has light bars connected by an interconnecting strip. The interconnecting strip has connection terminals more closely spaced than the light bars, so that there is flexibility in the pitch that can be set between light bars. In this way, a same set of components can be used to create a lighting system with different spacing between light bars. Thus, a lighting system can be formed with different efficacy, or light output flux, or size and shape, using the same components.

[0013] Preferably, the light bars can be spaced with any spacing within an allowable range. Thus, they may be positioned with a random spacing.

[0014] The pitch between the connection terminals is for example less than a width of each light bar. This means the light bars can be positioned with a pitch adjustment that is finer than the width of the light bar. This means fine adjustment of the light bar pitch is possible.

[0015] The width of each connection terminal, in the length direction of the interconnecting strip, is for example equal to half the pitch between connection terminals. This assists the soldering to an individual connection terminal.

[0016] A width of each connection pad is for example at least equal to the sum of two times the width of each connection terminal and the space between adjacent connection terminals. In this way, two connection terminals fit over a connection pad, meaning that any positional alignment is possible. For example, if the space between connection terminals is equal to the connection terminal width, then the width of each connection pad, in a length direction of the interconnecting strip, may be greater than 3 times the width of each connection terminal, in the length direction of the interconnecting strip. The width of each connection pad may be greater than 4 times the width of each connection terminal, to provide a safety margin.

[0017] If there is no space between connection terminals, then the width of each connection pad, in a length direction of the interconnecting strip, may be greater than 2 times the width of each connection terminal.

[0018] The width of each connection pad, in a length direction of the interconnecting strip, is for example greater than 2mm. This facilitates soldering, especially manual soldering.

[0019] The pitch between the light bars is preferably less than 600mm. The pitch may be set with any value in the range from the width of the light bar to 600mm. 600 mm x 600 mm is the normal size of a troffer luminaire.

[0020] The interconnecting strip for example comprises a base layer, a copper layer and a screening later, wherein the copper layer comprises first and second copper areas, wherein the first copper area forms the first line of connection terminals, and the second copper area forms the second line of connection terminals. This provides a simple structure for the interconnecting strip. The base layer for example comprises polyimide.

[0021] The first and second copper areas for example each comprise a backbone from which a plurality of U-shaped connection terminals protrude, wherein the connection terminals are arranged in a linear array, wherein the screening layer substantially covers the backbones. In this way, a line of separated connection terminals are exposed for soldering, but they are electrically all connected together. Power connections are made to the first and second copper areas.

[0022] The first and second copper areas for example have grooves between neighboring U-shaped connection terminals. These grooves prevent heat spreading quickly along the copper layer during the soldering, thus easing the soldering process.

[0023] The screening layer for example comprises a layer of insulating paint.

[0024] The invention also provides the interconnecting strip of the system as defined above.

[0025] These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] For a beter understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

[0027] Figure 1 shows a known interconnecting strip for connecting light bars;

[0028] Figure 2 shows a lighting system comprising a plurality of interconnected light bars;

[0029] Figure 3 shows an enlarged portion of the interconnecting strip to show dimensions;

[0030] Figure 4 shows an example of the structure of the interconnecting strip in exploded view;

[0031] Figure 5 shows how connections are made, in more detail;

[0032] Figure 6 shows the arrangement of Figure 5 with a different alignment; and Figure 7 shows three possible lighting system configurations using the same interconnecting strip.

[0033] DETAILED DESCRIPTION OF THE EMBODIMENTS

[0034] The invention will be described with reference to the Figures.

[0035] It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become beter understood from the following description, appended claims, and accompanying drawings. 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.

[0036] The invention provides a lighting system that comprises a plurality of spaced of light bars each having first and second connection pads for receiving electrical power. An interconnecting strip extends across the light bars for providing electrical power connections to the connection pads. The interconnecting strip comprises a first line of connection terminals extending along a first edge and a second line of connection terminals extending along an opposite second edge, wherein the pitch between connection terminals is smaller than a pitch between the light bars. The first and second lines of connection terminals each form a toothed structure. This provides flexibility in the spacing of the light bars.

[0037] Figure 1 shows a known interconnecting strip 10 for connecting light bars. It has a series of connection pads 12 spaced along the bar for soldering to connection terminals on the light bars. The connecting pads have a fixed spacing to correspond to the pitch between light bars with a lighting system, such as a panel luminaire. The pitch is for example 80.5mm.

[0038] The invention provides a connection method which can enable different numbers of light bars to be electrically connected as well as enabling different sizes of housing. In particular, any spacing of light bars is possible, within an overall range.

[0039] Figure 2 shows a lighting system 20 comprising a plurality of light bars 22, each comprising an array of lighting units 24 arranged in an array, such as a linear array. The light bars are arranged in spaced apart formation side-by-side and / or in parallel, so they form a rectangular overall shape. The lighting units 24 are preferably LEDs although other lighting units could be used.

[0040] Each light bar comprises first and second connection pads 26a, 26b for receiving electrical power. This electrical power is delivered by an interconnecting strip 30 extending across the light bars, for example perpendicular to the length direction of the light bars. There are soldered connections between the interconnecting strip 30 and the two connection pads 26a, 26b of each light bar. Thus, a single external pair of power connections is made to the interconnecting strip, and the interconnecting strip then routes electrical power to each of the light bars 22.

[0041] Figure 3 shows an enlarged portion of the interconnecting strip extending over two light bars 22. The interconnecting strip 30 comprises a first line 32a of connection terminals 34 extending along a first edge and a second line 32b of connection terminals 34 extending along an opposite second edge. Each connection terminal 34 comprises a U-shaped recess extending outwardly from a central area. A solder connection is to be made to the recess, hence connecting the connection pad beneath with the U-shaped connection terminal.

[0042] It is noted that the connection pads and connection terminals are both copper areas which are to be soldered together. The terms "pad" and "terminal" are used simply to avoid confusion as to the features being referred to. It is not intended to imply any particular structure. The lines of connection terminals 34 extend along opposite edges of the interconnecting strip. The connection terminals each comprise a recess into the edge for receiving solder, so that the edges have an undulating or zigzag shape. Thus, they have a toothed structure. For example, the space between the connection terminals is equal to or smaller than the width of the connection terminals, i.e., the connection terminals are close together (so that there are many positioning options) and they occupy at least half of the length of the interconnecting strip edge.

[0043] Figure 3 shows various dimensions which are discussed further below.

[0044] There is a pitch pl between the connection terminals 34, in a length direction of the interconnecting strip. This pitch pl is smaller than the pitch p2 (in the same direction) between the light bars. Thus, there are multiple options for the positioning of the light bars while still having the connection pads aligned with connection terminals. When the light bars are connected, there are unused connection terminals between them. Thus, instead of providing connection terminals at the intended spacing of the light bars, there are more connection terminals to provide flexibility in the positioning of the light bars. In this way, a same set of components can be used to create a lighting system with different spacing between light bars. Thus, a lighting system can be formed with different efficacy, or light output flux, or size and shape, using the same components.

[0045] The relative pitches and sizes of the connection pads and terminals are chosen to give a good range of lighting bar positions that can achieve correct alignment.

[0046] Figure 3 shows the following additional dimensions: dl: the width of the recess of the connection terminal (this will simply be termed the "width of the connection terminal"); dla: minimum width of copper at each connection terminal; d2: the width of the connection pads (in the length direction of the interconnecting strip); w: the width of the lighting bar (in the length direction of the interconnecting strip).

[0047] In the example shown, there is a spacing between the recesses of the connection terminals 34. At the limit, this spacing may be zero (hence dl=dla and dl=pl). This may be considered to define a full zigzag shape for the connection terminals.

[0048] The pitch pl between the connection terminals 34 is for example less than a width d2 of each light bar. This means the light bars can be positioned with a pitch adjustment that is finer than the width of the light bar. This means fine adjustment of the light bar pitch is possible.

[0049] The width dl of each connection terminal 34 in some examples is less than the pitch between the connection terminals, for example equal to half the pitch pl between connection terminals. By having a larger pitch, there is a gap between the connection terminal recesses. As explained below, this enables a slot to be provided between the connection terminals, to act as a thermal barrier during soldering.

[0050] For the example having a width dl equal to half the pitch pl, the width d2 of each connection pad is preferably greater than 3 times the width of each connection terminal, in the length direction of the interconnecting strip, and preferably more than 4 times the width of each connection terminal.

[0051] The two conditions above (pl =2dl and d2>3dl) rules together enable at least one connection terminal to be aligned with a connection pad for any desired pitch between the light bars (this will be shown in Figure 5). This is because two connection terminals can overlap with one connection pad.

[0052] For the example mentioned above with no spacing between connection terminals (dl =pl ), the width d2 of each connection pad only needs to be greater than 2 times the width of each connection terminal in order to enable this positioning of the light bars with any desired pitch.

[0053] In general, the width d2 of each connection pad is preferably at least equal to the sum of two times the width dl of each connection terminal and the space between adjacent connection terminals. Two connection terminals thus fit over the connection pad. In this way, any positional relationship will always result in one full connection terminal overlapping with a connection pad.

[0054] The width d2 of each connection pad 26a, 26b is for example greater than 2mm. This facilitates soldering. The pitch between the light bars is for example less than 600mm. The pitch may be set with any value in the range from the width of the light bar (i.e., with no spacing) to 600mm.

[0055] Figure 4 shows an example of the structure of the interconnecting strip in exploded view. The structure for example has the form of a flexible PCB, although it does not need to be flexible.

[0056] The interconnecting strip has a base layer 40, such as a polyimide (which can withstand relatively high temperature) layer, a copper layer 42a, 42b and a screening layer 44. The screening layer protects the copper layer and for example comprises an insulating paint. For example, in a PCB layout, only soldering pads and soldering fingers are exposed, whereas the other areas are painted with a protective coating, giving less risk of oxidation.

[0057] The copper layer comprises a first copper area 42a and a second copper area 42b. The first copper area 42a forms the first line 32a of connection terminals and the second copper area 42b forms the second line 32b of connection terminals. This provides a simple structure for the interconnecting strip.

[0058] The first and second copper areas each comprise a backbone 46 (in the form of an axial bar) from which a line of U-shaped connection terminals 34 project laterally. The solder is applied within the U-shaped opening and thus contacts the connection pad of the light bar beneath. The solder flows over the edges of the U-shape, i.e., over the whole area of the connection terminal, to form a mechanical and electrical connection between the connection pad of the light bar and the connection terminal of the interconnecting strip.

[0059] The central backbones thus electrically connect all of the connection terminals 34, but the connection terminals 34 are spaced apart so that they may be individually soldered to the connection pad of a selected light bar.

[0060] Figure 5 shows how connections are made, in more detail.

[0061] It shows the line of connection terminals 34 with gaps 52 between them. These gaps are formed by slots in the copper areas which extend beneath the screening layer 44, as illustrated as hidden detail 53. The gap between the two copper areas 42a, 42b (between the two backbones) is shown as hidden detail 54. The substrate is exposed beneath the gaps 52. The gaps provide a thermal barrier during soldering.

[0062] The screening layer 44 substantially covers the backbones of the copper areas but leaves exposed the line of separated connection terminals 34. The screening layer may also expose two power connection pads 46a, 46b to enable the two copper areas to be connected to an external power supply by soldering.

[0063] Figure 5 also shows one possible size relationship between the connection pad 26 and the connection terminals 34. It shows the case where pl=2dl and d2=3dl. If d2>=3dl, any positional relationship between the light bar and the interconnecting strip (and hence any desired light bar pitch) will result in alignment between at least one connection terminal 34 and the connection pad 26.

[0064] More preferably d2>4dl so that there is alignment between at least one connection terminal 34 and the connection pad with an additional clearance each side of the connection terminal 34 for the solder connection. Figure 6 shows a different alignment to Figure 5 and shows that for the example pl=2dl and d2=3dl, two recesses 34 (and one of the spaces between them) exactly cover a pad 26a, 26b.

[0065] This condition may be applied more generally, for any space si between the connection terminals 34. It means the width d2 of each connection pad, in a length direction of the interconnecting strip, is at least equal to the sum of two times the width dl of each connection terminal and the space si between adjacent connection terminals, i.e., d2>2dl+sl.

[0066] Figure 7 shows three possible lighting system configurations using the same interconnecting strip.

[0067] The top image shows six light bars evenly spaced across a width of a luminaire.

[0068] The middle image shows eight light bars evenly spaced across the same luminaire width hence giving increased light flux.

[0069] The bottom image shows six light bars but grouped into two groups of three, with a larger spacing between the groups.

[0070] The examples above show a single interconnecting strip connecting to multiple light bars. There could also be multiple interconnecting strips, each connecting to a sub-set of light bars. For example, a full set of light bars could be grouped into sub-sets, where each sub-set is a different color channel. An interconnecting strip may then provide power to a respective color channel. This approach may for example be used to create a tunable white lighting system.

[0071] Variations to the disclosed embodiments can be understood and effected by those skilled in the art 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.

[0072] 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.

[0073] If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

[0074] Any reference signs in the claims should not be construed as limiting the scope.

Claims

CLAIMS:

1. A lighting system comprising: a plurality of light bars (22), each comprising an array of lighting units (24) arranged on each light bar (22), wherein the light bars are arranged side-by-side with each other with a spacing between them, wherein each light bar comprises first and second connection pads (26a, 26b) for receiving electrical power; and a flexible interconnecting strip (30) extending across the light bars for providing electrical power connections to the connection pads (26a, 26b) of the light bars, wherein the interconnecting strip (30) comprises a first line (32a) of connection terminals (34) extending along a first edge and a second line (32b) of connection terminals (34) extending along an opposite second edge, wherein the first and second lines of connection terminals (34) each form a toothed structure, wherein a pitch (pl) between connection terminals (34), in a length direction of the interconnecting strip, is smaller than a pitch (p2) between the light bars (22), and wherein the first and second connection pads (26a, 26b) of the light bars for soldering to connection terminals of the first and second lines (32a, 32b) of connection terminals respectively.

2. The system of claim 1, wherein the light bars are solderable to the interconnecting strip with any spacing within a range of spacings.

3. The system of claim 1 or 2, wherein a width (d2) of each connection pad (26a, 26b), in a length direction of the interconnecting strip, is at least equal to the sum of two times the width (dl) of each connection terminal and the space (si) between adjacent connection terminals, in the length direction of the interconnecting strip.

4. The system of any one of claims 1 to 3, wherein the pitch (pl) between the connection terminals is less than a width (w) of each light bar.

5. The system of any one of claims 1 to 4, wherein a width (dl) of each connection terminal (34), in the length direction of the interconnecting strip, is equal to half the pitch (pl) between connection terminals.

6. The system of any one of claims 1 to 5, wherein a width (d2) of each connection pad (26a, 26b), in a length direction of the interconnecting strip, is greater than 2mm.

7. The system of any one of claims 1 to 6, wherein a pitch (p2) between the light bars (22) is less than 600mm.

8. The system of any one of claims 1 to 7, wherein each interconnecting strip comprises a base layer (40), a copper layer (42a, 42b) and a screening layer (44), wherein the copper layer comprises first and second copper areas (42a, 42b), wherein the first copper area (42a) forms the first line (32a) of connection terminals and the second copper area (42b) forms the second line (32b) of connection terminals.

9. The system of claim 8, wherein the base layer (40) comprises polyimide.

10. The system of claim 8 or 9, wherein the first and second copper areas (42a, 42b) each comprise a central backbone (46) from which a plurality of U-shaped connection terminals (34) protrude, wherein the connection terminals are arranged in a linear array, wherein the screening layer (44) substantially covers the backbones.

11. The system of claim 10, wherein the screening layer (44) covers the central backbones (46).

12. The system of claim 10 or 11, wherein the first and second copper areas (42a, 42b) have grooves between neighboring U-shaped connection terminals (34).

13. The system of any one of claims 8 to 12, wherein the screening layer (44) comprises a layer of insulating paint.

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