NL1026514C2 - LED light fitting with, has LED's mounted on heat conducting ceramic body in thermal contact with cooling blocks - Google Patents

Abstract

The LED's (4) are arranged in series in one or more groups and are mounted on a heat conducting body (3) comprising a ceramic material. This ceramic body is in thermal contact with cooling blocks (12) in the fitting casing (2).

Description

Brief indication: Lighting fixture.

DESCRIPTION

The present invention relates to a lighting fixture comprising a housing and a plurality of light-emitting diodes, LEDs arranged in the housing, the housing being provided with heat-conducting means for diverting heat generated by the LEDs during operation from the housing.

For illuminating spaces, objects or for signaling purposes and the like, a wide variety of lighting fixtures is used in practice. A number of different techniques can be distinguished not only with regard to their application, but also with regard to the means used for generating the light.

In addition to the widely known filament lamps, gas discharge lamps such as the known fluorescent or halogen lamps and so-called solid-state light-emitting components are also used as the light source. The latter group includes the light-emitting diode, which is known per se and is referred to in English as "Light Emitting Diode", abbreviated with the acronym LED.

An LED differs from the known filament lamp or gas discharge lamp by, among other things, a higher service life, more compact dimensions and the availability of the emitted light in various colors. In particular for use in environments where lighting fixtures are difficult to access, such as, for example, high halls, theaters, theaters and the like or for signboards above highways and the like, the use of LED lighting offers great economic advantages due to the longer lifespan compared to incandescent lamps. and gas discharge lamps.

With the so-called Power LEDs currently available on the market, such a high illuminance can be achieved that with 1 groups of such Power LEDs, lighting fixtures can be manufactured whose light output corresponds to that of the known incandescent lamps and gas discharge lamps. For orientation, with for example approx.

100 Power LEDs, a lighting fixture with an illuminance of 5 equal to that of, for example, a 200 W conventional filament lamp or gas discharge lamp can be achieved.

A problem that arises when using groups of LEDs is the dissipation of the heat generated by the LEDs during operation. Because the LEDs are solid or semiconductor components, they can only work in a limited temperature range for emitting their maximum illuminance and, of course, to prevent damage or failure of the LEDs.

The highest light output is obtained with LEDs that operate at an operating temperature of approximately 50 ° C. On average, every 10 10 ° C rise in temperature causes around 10% less light output. The maximum operating temperature must not exceed approximately 90 ° C, because then the risk of damage to the LEDs becomes too large and the light output is unacceptably low.

It is therefore the object of the invention in the first instance to provide a lighting fixture of the type mentioned in the preamble, with which the LEDs can operate as much as possible in their nominal temperature range, so that the highest possible luminous efficiency with the highest possible lifetime is achieved.

In accordance with the present invention, this task is solved by the fact that the LEDs are connected in series as at least one group for connection to the alternating current voltage network and that the LEDs are mounted on a thermally conductive body of ceramic material, which body is thermally is in contact with the heat-conducting means of the housing.

The invention is based on the insight that by using ceramic material for mounting the LEDs and by connecting the LEDs in series in one or more groups, a group directly on the usual AC alternating voltage network of, for example, 230 volts or 400 volts AC can be connected without the risk of voltage breakdown. Namely, ceramic material is suitable for higher voltages than conventional insulating mounting bodies, such as conventional printed circuit boards, which are only suitable for a maximum voltage of approximately 48V.

Ceramic material moreover has good heat-conducting properties and because the heat-conducting body of ceramic material is in direct thermal contact with the heat-conducting means of the housing, the heat generated by the LEDs is directly, via thermally conductive way, with the heat-conducting means of exchanged the housing. An efficient heat management is hereby achieved, wherein the LEDs can function in their nominal operating range during normal operation, whereby an efficient light output is obtained with a long service life customary for LEDs. Furthermore, the dimensions of the housing can be such that a lighting fixture according to the invention can be manufactured with dimensions of commercially available fixtures, such as for instance fluorescent fixtures, with corresponding or even higher illuminance.

In a further embodiment of the lighting fixture according to the invention, the heat-conducting body of ceramic material is advantageously designed as a printed circuit board. The 25 LEDs can hereby be mounted in the desired manner as one or more groups connected in series on the heat-conducting body.

In a still further embodiment of the invention, the heat-conducting body is made of a ceramic material with electrical insulating properties for voltages at least equal to the double value of the usual electricity grid alternating voltage.

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When using groups of LEDs for connection to, for example, the usual 230 Volt alternating current network, the ceramic material must have electrical insulating properties for voltages from approximately 500 V. This effectively reduces the risk of voltage breakdown, which improves the service life of the luminaire coming.

In a preferred embodiment of the lighting fixture according to the invention, the heat-conducting body comprises a ceramic material with a metal oxide incorporated therein, preferably aluminum oxide. Such a heat-conducting body can be mounted in the housing by conventional mechanical means and the assembled lighting fixture is sufficiently resistant to shocks and other mechanical influences during assembly and use.

The heat-conducting means can be arranged separately in the housing of the lighting fixture. In the preferred embodiment of the invention, the heat-conducting means are integrated in the housing, wherein in one embodiment of the invention the housing is made of aluminum. That is, the housing acts both as a casing and as a cooling element for releasing the heat generated by the LEDs to the environment.

In a further embodiment of the lighting fixture according to the invention, optical means are arranged on the light-emitting side of the LEDs, via which the light generated by the LEDs during operation is emitted. With these optical means, the luminaire can be adapted to emit the light in a specific desired direction and / or with a specific desired beam shape. In an embodiment of the invention, the optical means comprise a plurality of lenses with the same or mutually different radiation degrees. It will be clear that the lighting fixture according to the invention is hereby not limited to a certain type of lighting, such as room lighting, but can in fact be used for any lighting application, including (special) object lighting and signaling lighting.

For the latter purpose, the optical means, in a yet further embodiment of the lighting fixture according to the invention, can be provided with a print. Examples are signposts, billboards for facade advertising, pictograms or the like. Although it is advantageous to apply the imprint directly to the optical means, inter alia in order to suffice with as few individual components as possible, the invention also provides in a further embodiment thereof that the imprint can be applied to a separate light-transmitting plate arranged in front of the optical means from the illuminating side of the luminaire. This solution also has the advantage that the light-transmitting plate in question can be specifically adapted to a specific application, for example in shape, without the luminaire itself having to be adapted for this.

The use of the optical means and / or a light-transmitting plate also offers the possibility of using it as a sealing cover for the housing in order to prevent moisture and dirt from penetrating into the housing as much as possible. In particular in order to prevent the ingress of moisture in applications where the lighting fixture is mounted in the outside air or in rooms with a high moisture content, the invention further provides that the sealing cover by means of a sealing ring, such as a rubber sealing ring, connect the housing.

When connecting an LED or a group of LEDs connected in series in the same direction directly to an alternating voltage, it will be clear to a person skilled in the art that the relevant LED or LEDs only operate for half a period of the alternating voltage for emitting light. Although this can be compensated by, for example, switching two or more groups of LEDs connected in series anti-1026-5 T4_ _ 6 in parallel, the invention also provides in a yet further embodiment that at least four groups of LEDs connected in series have bridge branches of a form a double rectifier bridge circuit, wherein at least one group of LEDs connected in series is included as a center branch in the bridge circuit. Of the four bridge branches, two are each conducting for half a period of the alternating voltage, i.e. they emit light. The other two branches of the bridge are active during the other half of the period. The groups of LEDs connected as a so-called mid-branch, that is to say between the DC connection points of the bridge, on the other hand, will emit light both during the positive and the negative half period of the alternating voltage applied. The bridge branches themselves can again consist of groups of LEDs connected in parallel.

Such a circuit offers the advantage that by suitably spreading the LEDs over the heat-conducting mounting body, a light beam that is as homogeneous as possible can be obtained.

In a further embodiment of the lighting fixture according to the invention, the LEDs of the four bridge branches are mounted to this end as much as possible adjacent to each other, such that at least one LED of 20 adjacent LEDs is active during a first half period of the alternating voltage applied and at least one other LED is active during a second half period of the applied alternating voltage. As a result, in each case at least two adjacent LEDs contribute to the emitted light beam during the entire period of the alternating voltage. The LEDs of the group or groups connected in the middle branch, which are each continuously conducting, i.e. during the two halves of the applied alternating voltage, can advantageously be mounted substantially on the circumference of the heat-conducting body, for example when a relatively wide or diffuse light beam is necessary, or is mounted substantially in the middle of the heat-conducting body, when, for example, a 1? S 1 Λ _ 7 light beam with a highly concentrated light effect is required.

The amount of LEDs connected in series in a group is determined such that each LED operates during normal operation around its nominal operating voltage. In the lighting fixture according to the invention, so-called Power LEDs are preferably used.

For controlling the illumination intensity emitted by a lighting fixture, control means in the form of, for example, switching means known per se, including (remotely) electronically controlled switching means, can be incorporated in the lighting fixture with which, for example, one or more groups of LEDs can be selectively selected. switched on and / or off. Not only can the illuminance be adjusted with this, but of course also the shape and direction of the emitted light beam can be influenced. It will be understood that when simple switching means are used, the heat released thereby is negligible compared to electronically controlled foodstuffs used for this purpose in practice.

By connecting a group or groups of LEDs directly to the alternating current network, the need for additional supply circuits is avoided. Hereby not only is a relatively simple and inexpensive circuit obtained, but also an additional heat load of the heat-conducting mounting body or the heat-conducting means of the housing is avoided.

Within the scope of the invention, a group or groups of LEDs can also be connected via a simple rectifier circuit, such as a diode bridge cell, to the rectified voltage of the alternating-voltage voltage network. To maximize the light output, it is recommended to switch a suitable smoothing capacitor across the d.c. voltage terminals of the diode bridge cell. Such a rectifier circuit hardly contributes effectively to the heat output of the luminaire Λ Λ λ · Λ λ! Λ δ as a whole. If necessary, (suppression) filters and current-limiting means can be used for protection.

The LEDs can all be of the same or different colors, whereby the color of the light emitted can also be effectively controlled. _

The lighting fixture according to the invention is not limited to a specific geometric shape, but can essentially take any geometric shape. This makes the lighting fixture according to the invention versatile. In practice, the most common shapes are square, rectangular, round or oval.

The invention will be explained in more detail in the following description with reference to the enclosed drawings of embodiments of lighting fixtures.

Figure 1 shows, diagrammatically, perspective, with exploded parts, an embodiment of a lighting fixture according to the invention.

Figure 2 shows a circuit diagram according to the invention of groups of LEDs connected in series, with different groups being connected anti-parallel.

Figure 3 shows a circuit diagram of LEDs connected in groups in a double bridge rectifier circuit according to an embodiment of the invention.

Figure 4 shows a circuit diagram according to the invention of 25 LEDs connected in series in series, connected to a diode bridge cell rectifier.

Figures 5, 6 and 7 show schematically, perspective embodiments of lighting fixtures according to the invention, with a round, rectangular and elongated housing, respectively.

The invention is explained below with reference to preferred embodiments. It will be understood that the invention is not limited thereto, but that further modifications and additions are possible for a person skilled in the art, without departing from the inventive concept as set forth in the appended claims.

In Fig. 1, the reference numeral 1 as a whole denotes a lighting fixture according to the invention, which is shown in Fig. 1 with exploded parts. Viewed from the bottom up in the figure, the lighting fixture 1 comprises a housing 2, a thermally conductive body 3 of ceramic material, a group or groups of LEDs 4, sealing means 5 and optical means 6.

In the embodiment of figure 1, the housing 2 functions as heat conduction for releasing heat generated by the group or groups of LEDs 4 during operation to the environment. The housing 2 is therefore preferably made of aluminum.

According to the invention, the housing 2 can also be manufactured from, for example, a material that is not or only thermally conductive, wherein individual heat-conducting means are then attached in or to the housing, which are in thermal contact with the heat-conducting body 3. heat conducting means, for example in the form of cooling blocks, whether or not provided with cooling fins and the like, are schematically indicated in Figure 1 by broken lines 12. The cooling blocks 12 as well as the housing 2 can, if desired, be provided with ribs and channels for forced cooling by means of a cool fluid, or for forced air cooling by means of fans and the like.

The heat-conducting body 3, on which the group or groups of LEDs 4 are mounted, is made according to the invention of ceramic material, and in assembled condition is in direct thermal contact with the housing 2 or the heat-conducting means 12 which are in or on the housing 2 can be attached. In the embodiment shown, the housing 2 has a supporting edge 7 projecting along the inner periphery internally of the housing 2, on which the heat-conducting body 3 rests and is in thermal contact with the housing 2.

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The group or groups of LEDs 4 are mounted directly on the heat-conducting body 3 designed as a printed circuit board by means of, for example, suitable soldering connections which are known per se to a person skilled in the art.

Although not shown, it will be understood that on the thermally conductive mounting body 3 designed as a printed circuit board, further connection means and in the form of connection contacts, a rectifier circuit, smoothing capacitors and the like are provided to supply the group or groups of LEDs 4 with the usual electricity network. to connect.

If desired, as shown in Fig. 1, optical means 6 are provided, with which the housing 2 of the lighting fixture 1 can be sealed dust-proof and moisture-tight on the light-emitting side thereof. In order to achieve an optimum sealing, sealing means 5 are provided, in the form of, for example, a rubber sealing ring, which in assembled condition connects to the peripheral edge of the optical means 6 and the peripheral edge of the housing 2. By means of screws known per se or bolts 8, the optical means 6 are attached to the housing. Of course, suitable clamping means can also be used for this purpose or other means known and suitable for a person skilled in the art for fastening means for this purpose.

Figure 1 furthermore schematically shows a light-transmitting body or light-transmitting plate 9, which can be arranged on the light-emitting side of the lighting fixture 1, that is to say mounted directly on the optical means 6 or at a distance therefrom, the light-transmitting plate 9 can in itself also be attached to the housing 2 or to a further housing in which the lighting fixture 1 is accommodated.

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Optionally, both the optical means 6 and the light-transmitting plate 9 can be provided with a suitable imprint, for example for signaling purposes or for forming the light beam emitted or the color of the light emitted from the lighting fixture.

For forming the light beam, i.e. the direction and / or the shape of the emitted light beam, the optical means 6 can advantageously be provided with lenses with the same or mutually different radiation degrees. In figure 1 schematically indicated by the reference numeral 10. The optical means 6 can of course also be designed as a unitary lens. If no light beam formation or influencing is required, the optical means 6 can, if desired, be designed as a transparent sealing cover.

The heat-conducting body 3 of ceramic material preferably consists of a ceramic material with a metal oxide incorporated therein, such as aluminum oxide, in order to achieve optimum mechanical and thermally conductive properties. The ceramic material preferably has electro-insulating properties for voltages at least equal to double the value of the conventional electrical network voltage.

Figure 2 shows a block diagram of an electric LED circuit 20 for use in the lighting fixture according to the invention. In this embodiment, the circuit 20 comprises six groups of LEDs 21, 22, 23, 24, 25, 26 connected in series. The groups 21, 22, 23 are connected to alternating voltage terminals 27, 28 in the same current-conducting direction. The groups 24, 25, 26 are also connected in the same current-conducting direction, but opposite or anti-parallel to the groups 21, 22, 23. That is, the groups 21, 30, 22, 23 conduct during the first half period of the alternating voltage applied AC and the groups 24, 25, 26 conduct during the second half-period. The groups connected in parallel therefore give off light in turns. By mounting the groups spread over or mixed with the printed circuit board 4, a homogeneous light beam can be obtained in total.

For controlling the output beam, if desired, in terms of intensity and / or shape, switching means 31, 32, 33, 34, 35, 36 can be provided, each connected in series with a group of LEDs 21, 22, 23, respectively. 24, 25, 26. The switching means 31, 32, 33, 34, 35, 36 can be remote-controlled mechanical and / or electronic switches 10.

It is understood that more or fewer groups of LEDs may or may not be formed with switching means. With a conventional electricity network with 230 volt AC, a group comprises around 100 Power LEDs connected in series. For example, LEDs of the type 15 Lumileds with an average forward voltage of approximately 3.3 Volts.

Figure 3 shows a further electrical circuit diagram 40 of groups of LEDs 41, 42, 43, 44, 46, 47 connected as a so-called double bridge rectifier circuit. The groups 41, 42, 43, 44 form the four bridge branches and the groups 46, 47 form the so-called center branch of the bridge circuit connected between the DC terminals 48 (+) and 49 (-). The AC mains voltage AC is connected to the terminals 50, 51. One skilled in the art will understand that the AC mains voltage can be added to the circuit 25 via a transformer, such as an isolating transformer, if necessary.

During the positive half period of the applied alternating voltage the bridge branches 41, 42 and the center branch 45 conduct. During the negative half period of the applied alternating voltage the bridge branches 43, 44 and the center branch conduct. The center branch 45, or the groups 46, 47 therefore conduct during the two half periods of the alternating voltage applied.

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It will be understood that the bridge branches 41, 42, 43, 44 per se can also consist of different parallel groups of LEDs. The number of LEDs in a group is determined by the strength of the alternating voltage AC applied and the amount of LEDs connected in series in total that are simultaneously conducting. Of course, the electrical properties of the LEDs used also play a role in this. The circuit 40 can itself be provided again with switching means and with which, for example, one or more of the groups 46, 47 are interrupted or shunted. Of course such that no overload or short circuit occurs. For a maximum light output, a smoothing capacitor can be connected between the DC connection points 48, 49 (not shown).

A very homogeneous light beam can be obtained with the circuit 50 by suitably mounting the LEDs on the heat-conducting body 3 in the form of a printed circuit board.

For example, the groups of LEDs 41, 42, 43, 44 substantially in the center of the plate, such that adjacent LEDs light up alternately, or are conducting, and the continuous conductive groups of LEDs 46, 47 on the periphery of the plate 3. Conversely, the groups 41, 42, 43, 44 can be concentrated on the circumference and the groups 46, 47 substantially in the center of the plate 3. Other, mixed forms are also conceivable, for example depending on a desired application.

In the circuit diagram of FIG. 4, groups of LEDs 68, 69 connected in series are connected to the DC connection terminals 64, 65 of a diode bridge cell rectifier circuit 63 comprising power diodes 70. The AC voltage connection terminals 61, 62 of the diode bridge cell rectifier circuit 63 can be directly connected to the AC power grid AC to be connected.

Because the groups of LEDs 68, 69 are connected to the DC-terminal terminals 64, 65 of the diode bridge cell rectifier circuit 63, the light output is approximately 75% compared to, for example, the diodes of one of the groups of LEDs 21, 22, 23 24, 25, 26 as connected in the circuit 20 of Figure 2.

The light output can be increased still further, up to approximately 100%, by incorporating one or more smoothing capacitors 66 between the DC connection terminals 64, 65 of the diode bridge cell rectifier circuit 63. For voltage stabilization at the DC connection terminals 64, 65, a zener diode 67 can be applied if necessary. , switched as shown, or another DC stabilization circuit known per se. To prevent damage to the 10 LEDs, it is recommended to include a current limiting circuit 71 in series with the groups of LEDs 68, 69. This current limiting circuit 71 is optionally applicable. It will be understood that the diode bridge cell rectifier circuit 63, the one or more smoothing capacitors 66, the direct current stabilizing means or zener diode 67 and the current limiting circuit 71 can be mounted on the mounting body 3 of ceramic material together with the groups of LEDs 68, 69. Of course, the diode bridge cell rectifier circuit 63, the smoothing capacitor (s) 66, the voltage stabilization circuit 67 and the current limiting circuit 71 can also be mounted on a separate printed circuit board, provided that it has a sufficiently high breakdown voltage for clamping the alternating voltage connection. 61, 62 of the diode bridge cell rectifier circuit 63 on, for example, the AC mains voltage of 230 Volts or 400 Volts.

When using a transformer, such as a separation transformer for supplying alternating voltage to the circuit 60, a transformer with a center tap can be chosen, if desired, the rectifier circuit then consisting of only two diodes 70 in order to have a full or double rectification. 30, as is known per se to those skilled in the art.

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Figure 5 shows an assembled lighting fixture 1, according to Figure 1.

Figure 6 shows a lighting fixture 60 with the same construction as the lighting fixture 1, but with an elongated rectangular housing 71, with dimensions to replace, for example, a conventional fluorescent fixture.

Fig. 7 shows a lighting fixture 80 according to the invention with a round housing 81. When the circuit according to Fig. 3 is used, for example, the LEDs located substantially in the middle region 10, indicated by the circle 82 drawn in broken lines, may belong to the groups 46, 47 and the LEDs 83 located outside the circle 82 belong to groups 41, 42, 43, 44.

It also holds for the luminaires 1 and 70 that the LEDs can be suitably grouped in order to obtain, for example, a light beam that is as homogeneous as possible.

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Claims (25)

A lighting fixture comprising a housing and a plurality of light-emitting diodes, LEDs, arranged in the housing, the housing being provided with heat-conducting means for diverting heat generated by the LEDs during operation, characterized in that the LEDs are connected in series as at least one group for connection to the alternating current network and that the LEDs are mounted on a heat-conducting body of ceramic material 10, which body is in thermal contact with the heat-conducting means of the housing. 2. Lighting fixture according to claim 1, characterized in that the heat-conducting body is designed as a printed circuit board. 3. Lighting fixture according to one or more of the preceding claims, characterized in that the heat-conducting body is made of a ceramic material with electrically insulating properties for voltages at least equal to the double value of the AC mains voltage. Lighting fixture according to one or more of the preceding claims, characterized in that the heat-conducting body is made of ceramic material with a metal oxide incorporated therein. 5. Lighting fixture according to claim 4, characterized in that the metal oxide is aluminum oxide. 6. Lighting fixture according to one or more of the preceding claims, characterized in that the heat-conducting means are integrated in the housing. 7. Lighting fixture according to claim 6, characterized in that the housing is made of aluminum. 8. Lighting fixture according to one or more of the preceding claims, characterized in that optical means are arranged on the light-emitting side of the 1026514 LEDs via which the light generated by the LEDs during operation is emitted. 9. Lighting fixture as claimed in claim 8, characterized in that the optical means are adapted to provide a lighting fixture with a predetermined direction of light radiation and / or light beam shape. 10. Lighting fixture according to claim 8 or 9, characterized in that the optical means comprise a plurality of lenses with the same or mutually different radiation degrees. 11. Lighting fixture as claimed in claim 8, 9 or 10, characterized in that the optical means are provided with a print. 12. Lighting fixture as claimed in claim 11, characterized in that the print is provided on a separate light-transmitting plate arranged in front of the optical means, viewed from the light-emitting side of the lighting fixture. The lighting fixture according to one or more of claims 8 to 12, characterized in that the optical means and / or the light-transmitting plate are made attachable to the housing. 14. Lighting fixture according to claim 13, characterized in that the optical means and / or the light-transmitting plate are formed as a sealing cover for the housing, in order to prevent moisture and dirt from penetrating into the housing. 15. Lighting fixture according to claim 14, characterized in that the sealing cover connects to the housing by means of a sealing ring, such as a rubber sealing ring. Lighting fixture according to one or more of the preceding claims, characterized in that at least two groups of LEDs connected in series are connected anti-parallel for connection to the electrical network voltage network. 17. Lighting fixture according to one or more of claims 1 to 16, characterized in that at least four groups of LEDs connected in series 1 * form bridge branches of a double rectifier bridge circuit, wherein at least one group of LEDs connected in series is included as a middle branch in the bridge circuit. 18. Lighting fixture according to claim 16 or 17, characterized in that the LEDs are spread over the heat-conducting body in such a way that a light beam that is as homogeneous as possible is obtained. 19. Lighting fixture according to claim 17, characterized in that the LEDs of the groups connected in the bridge branches are mounted adjacent to each other as much as possible, such that at least one LED of adjacent LEDs is active during a first half period of the alternating voltage applied and at least one other LED is active during a second half period of the alternating voltage applied, and that the LEDs of the group or groups connected in the middle branch are mounted substantially on the circumference of the heat-conducting body, such that they are the LEDs of surround the bridge branches. 20 LEDs at least one LED is active during a first half period of the applied alternating voltage and at least one other LED is active during a second half period of the applied alternating voltage, and that the LEDs of the group or groups connected in the middle branch are substantially are mounted in the middle of the heat-conducting body, such that the LEDs of the bridge branches surround the LEDs of the central branch. 20. Lighting fixture according to claim 17, characterized in that the LEDs of the groups connected in the bridge branches are mounted as much as possible adjacent to each other, such that of adjacent 21. Lighting fixture according to one or more of the preceding claims, characterized in that a group of LEDs comprises an amount of LEDs connected in series such that each LED 30 operates during normal operation around its nominal operating voltage. Lighting fixture according to one or more of the preceding claims, characterized in that the LEDs are so-called Power LEDs. 23. Lighting fixture according to one or more of the preceding claims, provided with control means, for controlling the illuminance of the light emitted by the LEDs during operation. 24. Lighting fixture according to one or more of the preceding claims, characterized in that the housing and the heat-conducting means and / or the optical means and / or the light-transmitting plate with an imprint have an arbitrary geometric shape, in particular square, rectangular , round or oval. 25. Lighting fixture as claimed in claim 24, characterized in that the dimensions of the lighting fixture in the assembled state substantially correspond to dimensions of commercially available fixtures, such as, for example, fluorescent fixtures. <no 1c