Lighting device

A lighting device includes a heat sink, through which air can flow transversely to its longitudinal extension and a plurality of semiconductor light sources, in particular light-emitting diodes, arranged on the heat sink, wherein at least two of the semiconductor light sources are aligned in different directions.

RELATED APPLICATIONS

The present application is a national stage entry according to 35 U.S.C. § 371 of PCT application No.: PCT/EP2012/051252 filed on Jan. 26, 2012, which claims priority from German application No.: 10 2011 004 022.6 filed on Feb. 14, 2011.

TECHNICAL FIELD

Various embodiments relate to a lighting device having a heat sink, through which air can flow transversely to its longitudinal extension, and having a plurality of semiconductor light sources arranged on the heat sink, in particular light-emitting diodes.

BACKGROUND

LED retrofit lamps are known, in which light-emitting diodes (LEDs) are arranged on a support region oriented toward the front and only emit their light into a front half space. Cooling ribs extend in the rear direction from the support region.

Furthermore, LED retrofit lamps are known, which achieve a roughly omnidirectional light emission by a use of appropriately shaped optical waveguides.

LED retrofit lamps are also known, which have a cuboid carrier standing vertically on a base (which also accommodates a driver). The carrier is covered by a cover similar to an incandescent lamp. The light-emitting diodes are arranged on all free sides of the carrier and are therefore aligned toward the front (in the direction of a longitudinal axis aligned from back to front) and laterally with a rotational symmetry of 90° around the longitudinal axis. A heat sink around which cooling air can flow does not exist.

SUMMARY

Various embodiments provide a lighting device, in particular a retrofit lamp, of the type mentioned at the beginning, which, using simple means, allows a high cooling action and an optically effective light emission characteristic into a broad spatial angle range, in particular an at least approximately omnidirectional light emission.

The lighting device has a heat sink, through which (cooling) air can flow transversely to its longitudinal extension and a plurality of semiconductor light sources arranged on the heat sink. At least two of the semiconductor light sources are aligned in different directions.

Good cooling and avoidance of overheating are made possible even in the event of a recumbent or horizontal location of the lighting device by way of the heat sink which can have transverse flow. Through the different alignment of the semiconductor light sources (three-dimensional arrangement), a light emission is made possible into a broad spatial angle range even without a complex provision of reflectors.

The fact that at least two of the semiconductor light sources are aligned in different directions can mean in particular that they are arranged on support regions which are not aligned parallel to one another.

The heat sink has in particular at least one cooling structure. The cooling structure can in particular have at least one cooling projection, in particular at least one cooling rib or cooling strut, but also cooling pins, lamellae, or the like.

The at least one semiconductor light source preferably includes at least one light-emitting diode. If a plurality of light-emitting diodes are provided, these may emit light in the same color or in different colors. A color may be monochrome (e.g., red, green, blue, etc.) or multichrome (e.g., white). The light emitted by the at least one light-emitting diode can also be infrared light (IR-LED) or ultraviolet light (UV-LED). A plurality of light-emitting diodes may generate a mixed light; e.g., white mixed light. The at least one light-emitting diode may contain at least one wavelength-converting phosphor (conversion LED). The phosphor may alternatively or additionally be arranged at a distance from the light-emitting diode (“remote phosphor”). The at least one light-emitting diode may be provided in the form of at least one individually housed light-emitting diode or in the form of at least one LED chip. A plurality of LED chips may be installed on a shared substrate (“submount”). The at least one light-emitting diode can be equipped with at least one separate and/or shared optic for beam guiding, e.g., at least one Fresnel lens, collimator, etc. Instead of or in addition to inorganic light-emitting diodes, e.g., based on InGaN or AlInGaP, in general organic LEDs (OLEDs, e.g., polymer OLEDs) are also usable. Alternatively, the at least one semiconductor light source can have, e.g., at least one diode laser.

In one embodiment, the lighting device has a light-transmissive cover for covering the semiconductor light sources and a cooling structure of the heat sink, in particular including a plurality of cooling struts, protrudes into a longitudinal section of the lighting device in which the cover is also located (also referred to hereafter as the “bulb region”). The cooling structure and the cover therefore share the bulb region, whereby heat dissipation of the lighting device in the bulb region is improved.

Alternatively, the heat sink may substantially not protrude into the bulb region, but rather may only be arranged behind the semiconductor light sources, for example. The semiconductor light sources may be arranged, for example, on a three-dimensionally shaped, heat-conductive carrier, so that waste heat of the light-emitting diodes can be transmitted to the heat sink via the substrate (which itself does not have any dedicated cooling structure).

In one embodiment, parts of the cooling structure of the heat sink, in particular cooling struts, and semiconductor light sources are arranged alternately in a circumferential direction of the lighting device. A lighting device which may be substantially uniformly and effectively cooled in the bulb region and which illuminates sufficiently uniformly in the circumferential direction may thus be provided. This embodiment may include, for example, a repeated sequence in the circumferential direction of a cooling strut and at least one semiconductor light source.

In still another embodiment, the heat sink has a front support region for arranging at least one of the semiconductor light sources, a plurality of cooling ribs or cooling struts extend in the rear direction (opposite to the direction of the longitudinal axis) from the upper support region, in particular from its edge, a plurality of laterally aligned or lateral support regions for respectively at least one of the semiconductor light sources project from the upper support region, in particular from its edge, and/or the lateral support regions are arranged between respective cooling struts (or other cooling projections). The upper support regions and the lateral support regions (or the support surfaces thereof which carry the semiconductor light sources) are aligned differently. Direct irradiation of an upper half space extending in the direction of the longitudinal axis is easily made possible by the front support region, for example, by means of a support surface oriented toward the front for at least one of the semiconductor light sources. The cooling struts extending from the front support region cause a large-area, effective heat dissipation from the upper support region. The lateral support regions allow lateral light emission in a simple manner, in particular substantially over a half space extending on both sides up to the longitudinal axis. The lateral support regions can extend in the rear direction, for example. Because the lateral support regions are arranged between respective cooling struts, amplified heat dissipation is also allowed from the lateral support regions, in particular toward the cooling struts, and with light emission which is not substantially obstructed by the cooling struts. The cooling struts, or the like, preferably protrude to the rear beyond the lateral support regions, in order to allow a high level of transverse flow.

Instead of the lateral support regions provided on the heat sink, these can also be provided, for example, on a carrier, in particular one which has good thermal conductivity, which is fastened on the heat sink.

For still further amplified heat dissipation from the lateral support regions to the cooling struts, adjacent lateral support regions and cooling struts are preferably connected to one another, for example, by welding or integrally. The lateral support regions and the cooling struts can thus in particular form a ring.

Furthermore, in one embodiment, the cover overlaps the front support region and the lateral support regions while leaving the cooling struts free. The cover thus does not obstruct the effect of the cooling struts and nonetheless reliably protects the semiconductor light sources.

The cover may then have in particular a plurality of strip-shaped or tab-shaped regions, which each overlap one of the lateral support regions. The lateral support regions and similarly the tab-shaped regions may be regularly distributed in particular in the circumferential direction. The tab-shaped regions preferably run together at a tip of the cover, wherein the tip may be used in particular to cover the front support region.

The cover may be latched onto the heat sink in particular, for example, clipped on. For this purpose, the cover may have catch projections in particular on the tab-shaped regions, e.g., catch lugs, which can engage in a matching catch opening or undercut of the heat sink or which can engage behind the heat sink.

The cover may be transparent or opaque (diffusely scattering).

In an embodiment which has particularly good thermal heat dissipation and is producible simply and cost-effectively, at least the front support region, at least a part of the cooling struts, and the lateral support regions are integrally connected to one another or form an integral part.

In a preferred embodiment for particularly simple production, the heat sink is implemented in two parts. In particular, the first part may include the front support region, the cooling struts, and the lateral support regions. The second part may include further cooling struts, for example.

In particular if the heat sink is constructed in two parts, the inner cooling struts and the outer cooling struts may be arranged on different parts.

The heat sink can in general have different types of cooling struts, in particular outer cooling struts and inner cooling struts, wherein the outer cooling struts are arranged further to the outside in the radial direction than the inner cooling struts. The inner cooling struts and/or the outer cooling struts can be arranged rotationally-symmetrically around the longitudinal axis. The inner cooling struts and/or the outer cooling struts may also be distributed uniformly in the circumferential direction.

The heat sink may in particular have at least one sheet-metal part, in particular a stamped/bent part. Alternatively, the heat sink may have at least one cast part, in particular a diecast part, in particular an aluminum diecast part.

In still another embodiment, the lighting device has a light-transmissive cover for covering the semiconductor light sources and has, in a longitudinal section of the lighting device in which the cover is also located, at least one air passage, wherein the at least one air passage allows an air flow through the lighting device in the longitudinal section substantially parallel to the longitudinal extension of the lighting device. An amplified heat dissipation in the bulb region can thus be achieved. Furthermore, a stronger air flow through the heat sink and therefore more effective cooling can be achieved in the event of a vertical or upright location of the lighting device, for example, in that an accumulation of air at a front region of the heat sink is prevented.

The air passages may be implemented in particular as air passage channels. The at least one air passage may extend through the cover, for example, in that the cover provides a corresponding (e.g., funnel-shaped or tubular) channel or channel section. Alternatively or additionally, the cover may be omitted around the air passage. The air passage may in particular include an air passage opening in the heat sink.

Furthermore, in one embodiment, a housing part or housing region, which has a driver cavity provided for receiving a driver, is arranged outside the bulb space, i.e., below the region covered or enclosed by the cover. A reduced heat dissipation from the semiconductor light sources because of waste heat generated by the driver is thus avoided.

In an alternative embodiment, a housing region having a driver cavity is arranged at least partially inside the bulb space, i.e., in the region covered or enclosed by the cover. A particularly short lighting device may thus be provided. For effective heat dissipation of the driver operating in the cavity, in particular by an air stream flowing past it, it is preferable if a greater fraction of the waste heat generated by the driver is generated at the housing part arranged inside the bulb space.

So as not to worsen heat dissipation from the light-emitting diodes because of the waste heat of the driver, in one embodiment, a thermally insulating layer is provided between the driver housing and the heat sink. The thermally insulating layer can be, for example, a layer made of a material having poor thermal conductivity, for example, plastic, or also may be an air gap.

In a refinement, the lighting device is a lamp. In particular, the lamp may be a retrofit lamp, in particular an incandescent lamp retrofit lamp. Retrofit lamps are provided for the purpose of replacing conventional lamps, for example, incandescent lamps. The lighting device has the same electrical terminal for this purpose as the incandescent lamp to be replaced and has an at least coarsely approximated external contour, which in particular does not exceed or does not substantially exceed an external contour of the conventional incandescent lamp.

DETAILED DESCRIPTION

The following detailed description refers to the accompanying drawing that show, by way of illustration, specific details and embodiments in which the disclosure may be practiced.

FIG. 1shows a side view of a lighting device101according to a first embodiment. The lighting device101is an LED incandescent lamp retrofit lamp, i.e., it uses light-emitting diodes as semiconductor light sources and is provided for the purpose of replacing a conventional incandescent lamp. The lighting device101has the same electrical terminal for this purpose as the incandescent lamp to be replaced and has an at least coarsely approximated external contour, which in particular does not exceed or does not substantially exceed an external contour of the conventional incandescent lamp.

The lighting device101is elongated substantially along its longitudinal axis L. The lighting device101is substantially rotationally-symmetrical to the longitudinal axis L. A rear end of the lighting device101is formed by a base102, which forms the electrical terminal, for example, an Edison screw-type base. A front end of the lighting device101is formed by a tip103of a light-transmissive cover104. The light-transmissive cover104has a shape of a spherical cap and covers a plurality of light-emitting diodes (not illustrated). At least two of the light-emitting diodes are aligned in different directions (three-dimensional arrangement), i.e., they have different main emission directions. A greater spatial angle can thus be irradiated in comparison to an alignment of the light-emitting diodes performed only in parallel to the longitudinal axis L. Since light-emitting diodes typically only emit into a half space centered around their main emission direction, in the event of an alignment of the light-emitting diodes or their main emission direction only in the direction of the longitudinal axis L (“planar arrangement”), only an upper half space OH above their light exit surfaces (direct and therefore particularly optically effective) is also irradiated. By way of the different alignments of the light-emitting diodes, light can be irradiated in a simple manner also directly into a lower half space UH complementary to the upper half space OH.

The light-emitting diodes are arranged, for example, on a front region (not illustrated) of a heat sink105, which is covered here by the cover104. The heat sink105is constructed in two parts, as described in greater detail hereafter with reference toFIGS. 6 to 9.

Five outer cooling struts106extend in the rear direction from the front region of the heat sink105. The outer cooling struts106are arranged in a circumferential direction uniformly spaced apart at an angular offset of approximately 72°. Adjacent outer cooling struts106have a large air gap between them. Furthermore, inner cooling struts107extend in the rear direction from the front region, which are arranged rotationally-symmetrically in a circumferential direction. A large air gap is located between at least some of the inner cooling struts107. The inner cooling struts107are shorter than the outer cooling struts106.

The cooling struts106and107are seated with their respective rear end108or109, respectively, on a housing region110or are attached with their rear ends108,109close to the housing region110. The housing region110adjoins the base102at the rear and carries the heat sink105on the front side. The housing region110is also used for receiving a driver for operating the light-emitting diodes from an electrical signal tapped via the base102and contains a driver cavity for this purpose (not illustrated).

During operation of the lighting device101, the light-emitting diodes heat up and dissipate their waste heat to the heat sink105. A space which is covered by the cover104is also heated, from which heat is partially dissipated via the cover104. In addition, the driver housed in the housing region110also heats up, and dissipates its waste heat to the housing region110. If the cooling struts106and107contact the housing region110with their free ends, the housing region110can at least partially transmit its heat directly to the cooling struts106and107.

In the case of an upright or vertical alignment of the lighting device101, the cooling struts106and107have an air stream, which is likewise aligned substantially vertically (flowing along the longitudinal extension), flowing around them and are thus cooled. In the case of a recumbent or horizontal alignment of the lighting device101, air can also simply flow through the cooling struts106and107of the heat sink105(transversely to the longitudinal extension), so that good heat dissipation of the heat sink105is also possible in this location.

FIG. 2shows a side view of a lighting device201according to a second embodiment.

In contrast to the lighting device201, the other cooling struts206now extend in relation to the longitudinal axis L up to a section, also designated hereafter as the bulb region KB, in which the cover204is also located. In other words, both parts of the outer cooling struts206and also the parts of the cover204are located in the bulb region KB. This improves heat dissipation of the lighting device201, in particular also in the upper half space OH.

More precisely, the cover204has a plurality of strip-shaped or tab-shaped regions211, which are distributed uniformly in the circumferential direction. The tab-shaped regions211run together at a tip203of the cover204. The tab-shaped regions211and the outer cooling struts206alternate in the bulb region KB in the circumferential direction.

In particular, the tab-shaped regions211may overlap laterally or radially aligned light-emitting diodes412, as shown in greater detail inFIG. 3.

Each of the tab-shaped regions211overlaps two light-emitting diodes412, which are aligned radially in relation to the longitudinal axis L and are shown as semitransparent here. The light-emitting diodes412are not substantially shaded by the cooling struts206, so that a broad emission results with respect to a circumferential direction. Since the light-emitting diodes412are additionally arranged above the gap between the outer cooling struts206, a broad azimuthal emission with respect to the longitudinal axis L without substantial shading by the cooling struts206is also made possible, i.e., broadly into the lower half space UH. This allows an omnidirectional light emission.

FIG. 4shows the lighting device201as a sectional illustration in a diagonal view.FIG. 5shows the lighting device201in a view diagonally from the front. The heat sink205has a flat front support region513, which is perpendicular to the longitudinal axis L and has at least one light-emitting diode412aligned toward the front (i.e., in the direction of the longitudinal axis L) on its outer side in the middle. The front support region513merges at its edge into an edge region514angled perpendicularly thereto to the rear. The edge region514is composed of the sections of the outer cooling struts206present in the bulb region KB and of lateral support regions515arranged in between them. The edge of the front support region513and the edge region514have a pentagonal shape in a top view, so that adjacent outer cooling struts206or adjacent lateral support regions515are arranged offset at an angle of approximately 72° about the longitudinal axis L. The light-emitting diodes412of adjacent lateral support regions515thus also emit laterally offset at an angle of approximately 72° about the longitudinal axis L. By way of the different (three-dimensional) alignment (parallel or perpendicular to the longitudinal axis L, respectively) of the support region513and the edge regions514, a great spatial angle range is irradiated and an at least coarsely approximately isotropic light emission similar to a conventional incandescent lamp is made possible.

The front support region513, the lateral support regions515, and the outer cooling struts206are embodied integrally. The edge region514is closed, so that good thermal connection of the lateral support regions515to the outer cooling struts206results.

A plurality of air passage holes516, to each of which an opening517in the cover204is assigned on the outside, are located in the front support region513. In particular, air located in front of the lighting device201can directly reach inside the heat sink205through the air passage holes516, specifically inside an inner region there enclosed by the cooling struts107,206, or vice versa. This improves in particular an air stream at the cooling struts107,206(by reducing an air accumulation at the front support region513) and at the cover204in the event of a vertical (upright or inverted) location of the lighting device201and improves its cooling. The openings have side walls519, which obstruct a cooling air stream to the light-emitting diodes412and direct mechanical contact and therefore the soiling thereof or mechanical damage thereto.

Furthermore, the housing region110is connected to the upper support region513via a cable channel518, in order to be able to lead at least one electrical line originating from the driver (not illustrated) to the light-emitting diodes412.

As shown in particular inFIG. 5, two light-emitting diodes412are installed in each case on a shared substrate619, and the substrate619is fastened on the associated front support region513or lateral support region515.

FIG. 6shows a first (integral) part205aof the two-part heat sink205. The first part205aconsists of the front support region513, the lateral support regions515, and the outer cooling struts206. The lateral support regions515and the sections of the outer cooling struts206connected thereto form the closed circumferential edge or edge region514. The front support region513and the edge region514are thus embodied in a cup or shell shape having a pentagonal basic shape. The outer cooling struts206are rounded at their transition to the adjacent lateral support regions515, in order to provide a sufficiently tight support for the cover204. The sections of the outer cooling struts206originating from the edge region514are inclined inward (in the direction of the longitudinal axis L).

The first part205amay be in particular a sheet-metal part, which is in particular stamped out of a piece of sheet metal and then bent into shape, i.e., a stamped/bent part.

FIG. 7shows an (integral) second part205bof the heat sink105. The second part205bhas a peripheral edge820having a pentagonal footprint (in a top view), which fits into the edge region514of the first part without play or with only slight play. The edge820is open on both sides (to the front and to the rear), so that the cable channel518can be led through. The (inner) cooling struts107extend from a lower side821of the edge820, wherein two at least approximately parallel inner cooling struts107respectively extend from each of the five lateral surfaces822. Adjacent inner cooling struts107of adjacent lateral surfaces822abut one another. For this purpose, the inner cooling struts107are bent inward close to the edge820and then oriented pointing outward again at a predetermined bending line823(with increasing distance from the edge820).

The second part205bcan also be in particular a sheet-metal part, which is in particular stamped out of a piece of sheet metal and then bent into shape, i.e., a stamped/bent part.

FIG. 8shows the heat sink205, which is composed of the first part205aand the second part205b. For this purpose, the second part205bhas been plugged with its edge820in front from the rear into the first part205a, in particular up to the stop, for example, with elastic bending of the outer cooling struts206. The two parts205aand205bcan be connected to one another, for example, by a press fit and/or gluing. The two parts205a,205bcan also be latched with one another, for which purpose they can have suitable catch elements (not illustrated).

The cover204may be latched on the heat sink205, e.g., by providing inwardly directed catch projections, in the form here of catch lugs, on the free ends of the tab-shaped regions211, wherein the catch lugs can engage behind a lower edge of the associated lateral support regions515. The cover204can thus be snapped or clipped onto the heat sink205, for example.

FIG. 9shows a polar diagram of three measurements M1, M2, M3of an intensity of a light emission of the lighting device201, wherein the polar angle is determined with respect to the longitudinal axis L and a polar angle of 0° corresponds to a view against the direction of the longitudinal axis L onto the lighting device201or a position of an observer from the lighting device201in the direction of the longitudinal axis L. This approximately isotropic light emission achieves an optical pattern which is at least coarsely similar to that of a conventional incandescent lamp and can be described as omnidirectional.

FIG. 10shows a sectional illustration in a diagonal view of a lighting device1101according to a third embodiment.

The lighting device1101is implemented similarly to the lighting device201, except that now the housing region110protrudes up to the bulb region KB and the cable channel518is no longer provided for this purpose. The housing region110is divided into a first housing part110aand a second housing part110b. The housing parts110aand110bmay form two subregions of a shared driver cavity or may include different driver cavities. In particular, the housing part110aprotruding into the bulb region KB may accommodate at least a part of the driver, which generates in particular more waste heat than the part of the driver which is housed in the housing part110b.

A thermally insulating layer1123is introduced between the first housing part110aand the front support region513of the heat sink205.

LIST OF REFERENCE SIGNS

101lighting device102base103tip of the cover104light-transmissive cover105heat sink106outer cooling strut107inner cooling strut108rear end of the outer cooling strut109rear end of the inner cooling strut110housing region201lighting device203tip of the cover204cover205heat sink205afirst part of the heat sink205bsecond part of the heat sink206outer cooling strut211tab-shaped region of the cover412light-emitting diode513front support region514edge region515lateral support region516air passage hole517opening of the cover518cable channel519side wall of the opening619substrate820edge of the second part of the heat sink821lower side of the edge of the second part822lateral surface of the edge of the second part823bending line1101lighting device1110housing region1110afirst part of the housing region1110bsecond part of the housing region1123thermally insulating layerKB bulb regionL longitudinal axisM1-M3measurementsOH upper half spaceUH lower half space