LED lamp assembly

There is provided a LED lamp assembly (1300) comprising a heat sink (1301) having a cooling structure with an outer circumference part and a center part (1311), which supports a plurality of LEDs, and the material thickness of the cooling structure increases inwards from the outer circumference part to the center of the heat sink. The LED assembly may further comprise a lampshade supported by the outer circumference part of the heat sink. There is also provided a LED lamp assembly comprising a heat sink having a center, an outer circumference part supporting a plurality of LEDs, and a cooling structure with a number of vent-holes allowing passage of air, the cooling structure supported by the outer circumference part and extending inwards towards the center from the outer circumference part. Furthermore, a LED lamp assembly comprises an outer circumference part which supports a plurality of LEDS and cooling fans extending inwards and tilted relatively to a center axis, the material thickness of the cooling fins decreases inwards from the outer circumference.

RELATED APPLICATIONS

This application claims the benefit under 35 U.S.C. §371 of International Patent Application No. PCT/EP2011/057125, which has an International Filing Date of May 4, 2011, which claims priority to Danish Patent Application No. PA 2010 00391, filed May 5, 2010, the contents of all of which are incorporated herein by reference in their entirety.

FIELD OF INVENTION

The present invention relates to a light emitting diode (LED) lamp assembly, and more particularly to LED lamp assembly having a heat sink supporting a plurality of LEDs.

BACKGROUND OF THE INVENTION

The technology of light emitting diodes, LEDs, has rapidly developed in recent years from indicators to illumination applications. With the features of long-term reliability, environment friendliness and low power consumption, the LED is viewed as a promising alternative for future lighting products.

A conventional LED lamp comprises a heat sink and a plurality of LED modules having LEDs attached to an outer surface of the heat sink to dissipate heat generated by the LEDs. The outer surface of the heat sink generally is a plane and the LEDs are arranged close to each other, whereby considerable heat is generated. When the LED lamp works, the LEDs mounted on the planar outer surface of the heat sink only form a flat light source.

Thus, it is desirable to devise a new LED lamp assembly having a heat sink providing an effective dissipation of the generated heat. It is also desirable to devise a new LED lamp assembly providing an even and broad illumination of the light generated by the LEDs.

SUMMARY OF THE INVENTION

According to a first aspect of the invention there is provided a LED lamp assembly comprising: a heat sink having a cooling structure with an outer circumference part and a centre part, which centre part supports a plurality of LEDs, and wherein the material thickness of the cooling structure increases inwards from the outer circumference part to the centre of the heat sink. The cooling structure may comprise a number of vent-holes allowing passage of air, and the size of the vent-holes may decrease inwards towards the centre of the heat sink. The vent-holes or openings may have an oblong shape.

It is within an embodiment of the first aspect of the invention that the cooling structure has the form of an inverted bowl, and it is within another embodiment of the first aspect of the invention that the upper surface of the cooling structure is flat.

According to an embodiment of the first aspect of the invention, the area taken up by the vent-holes compared to the area of the rigid cooling part surrounding the vent-holes increases inwards from the outer circumference part to the centre of the heat sink.

According to one or more embodiments of the first aspect of the invention, the LED assembly may further comprise a lampshade supported by the outer circumference part of the heat sink.

The first aspect of the invention also covers an embodiment, wherein the cooling structure has a folded or pleat like form. Here, the cooling structure may be closed without vent-openings, and the cooling structure may have the form of an inverted bowl.

It is within one or more embodiments of the first aspect of the invention that the bottom of the centre part of the heat sink is adapted to support the LED light source. The LED light source may be a PrevaLED® Core light engine. The bottom of the centre part of the heat sink may also hold a diffuser plate below the LED light source.

For the first aspect of the invention it is preferred that the heat sink has a substantially circular outer circumference.

According to a second aspect of the present invention there is provided a LED lamp assembly comprising: a heat sink supporting a plurality of LEDs, wherein the heat sink has an outer circumference part supporting at least part of the LEDs. It is preferred that the heat sink has a cooling structure allowing passage of air, which cooling structure is supported by the outer circumference part and extends inwards from the outer circumference part. The cooling structure may comprise a number of vent-holes and/or a plurality of cooling fins.

Thus, the second aspect of the invention also covers a LED lamp assembly comprising: a heat sink having a centre, an outer circumference part supporting a plurality of LEDs, and a cooling structure with a number of vent-holes allowing passage of air, said cooling structure being supported by the outer circumference part and extending inwards towards the centre from the outer circumference part. The size of the vent-holes may decrease inwards towards the centre of the heat sink. The cooling structure may have the form of an inverted bowl.

For embodiments of the second aspect of the invention it is preferred that the material thickness of the cooling structure decreases inwards from the outer circumference part to the centre of the heat sink.

It is preferred that a major part or all of the LEDs are supported by the outer circumference part of the heat sink. Preferably, the outer circumference part of the heat sink is circumferentially closed, but the present invention also covers embodiments wherein the outer circumference part of the heat sink is made up of two or more separated circumference sub-parts.

According to an embodiment of the second aspect of the invention, the heat sink may have a plurality of cooling fins being supported by the outer circumference part and extending inwards from the outer circumference part

For embodiments of the second aspect of the invention, wherein the cooling structure comprises a plurality of cooling fins extending inwards from the outer circumference part, then at least part of or all of the cooling fins may be tilted or partly tilted relatively to a centre axis of the heat sink. Here, the cooling fins may be arranged so that a lower surface part of a first cooling fin is partly shielding an upper surface part of a following second cooling fin, when looking downwards at the top surface of the heat sink.

Thus, the second aspect of the invention also covers a LED lamp assembly comprising: a heat sink having a centre and an outer circumference part, which outer circumference part supports a plurality of LEDS, and which outer circumference part further supports a plurality of cooling fins extending inwards towards the centre from the outer circumference part, wherein at least part of or all of the cooling fins are tilted or partly tilted relatively to a centre axis of the heat sink, and wherein the material thickness of the cooling fins decreases inwards from the outer circumference part towards the centre of the heat sink.

It is preferred that the tilt angle of the cooling fins decrease from the outer circumference part towards the centre of the heat sink. The tilt angle of the cooling fins may at the outer circumference part be in the range of 10-45°, such as in the range of 20-35°, such as in the range of 25-30°. The tilt angle of the cooling fins at the end of the cooling fins, close to the centre, may be below 20°, such as below 10°.

For embodiments of the second aspect of the invention wherein the cooling structure comprises a plurality of cooling fins extending inwards from the outer circumference part, then the width or cross sectional area of the cooling fins may decrease in the inward direction from the outer circumference part towards the centre of the heat sink. It also within one or more embodiments of the second aspect of the invention that the cooling fins have an upper surface, a lower surface, and first and second side surfaces, and that, for at least a part of or for all of the cooling fins, the area of each side surface is larger than the area of the upper surface and larger than the area of the lower surface.

For embodiments of the second aspect of the invention having a cooling structure with vent-holes, then the area taken up by the vent-holes compared to the area of the rigid cooling part surrounding the vent-holes may increase inwards from the outer circumference part to the centre of the heat sink.

For both the first and second aspects of the invention it is preferred that the outer circumference part of the heat sink is made of an electrically non-conducting material, such as a ceramic material. It is also preferred that the cooling structure is made of an electrically non-conducting material such as a ceramic material. Thus, the whole heat sink may be made of an electrically non-conducting material such as a ceramic material. The electrically non-conducting material or ceramic material may in one embodiment be aluminium nitride, AlN.

It is within a preferred embodiment of the second aspect of the invention that at least part of or all of the LEDs are surface-mount LEDs. The surface-mount LEDs may on the back side have a cathode pad, an anode pad and a thermal pad, and the thermal pads may be thermally contacting or mounted to the outer circumference part of the heat sink.

The second aspect of the invention also covers one or more embodiments, wherein the heat sink is made of an electrically conductive material, such as aluminium, copper or zirconium. Here, the LEDs may be mounted on a printed circuit board, which may be a rigid or a flexible printed circuit board, and which may be mounted to the outer circumference part of the heat sink.

The second aspect of the invention also covers embodiments where at least the outer circumference part of the heat sink or the whole heat sink is made of an electrically non-conducting material, such as a ceramic material, and where the LEDs are mounted on a printed circuit board, which may be a rigid or a flexible printed circuit board, and which may be mounted to the outer circumference part of the heat sink.

According to an embodiment of the second aspect of the invention, then an electrically conducting layer, plate or ring may be arranged at the outer circumference part of the heat sink and provide at hold for the LEDs supported by this outer circumference. The conducting plate or ring may be secured to the top of the outer circumference part of the heat sink by a number of conically shaped pins inserted into corresponding holes from the bottom of the heat sink.

According to present invention the LEDs may be electrically connected in series, in parallel, or in a combination of serial and parallel connections. In a preferred embodiment the LEDs may be divided into a number of groups with the LEDs of the same group being electrically connected in series, with each group of series connected LEDs have first and second voltage inputs. For embodiments having the electrically conducting layer, plate or ring, the first voltage inputs may be electrically conductive connected to the conducting plate or ring. The second voltage inputs may be electrically connected to corresponding contact plugs arranged at the outer circumference part of the heat sink.

The second aspect of the invention further covers one or more embodiments, wherein the assembly further comprises a base for holding the heat sink. The base may also be adapted for providing supply of electrical power to the LEDs. The base may have a number of legs for holding the heat sink, and these legs may also be adapted for providing the supply of electrical power to the LEDs. For embodiments having groups of serially connected LEDs, then the number of base-legs may equal the number of LED groups. It is preferred that the base holds driver circuitry for supplying a DC voltage to the LEDs. The driver circuitry may comprise an AC to DC converter for converting a high-voltage AC input into a DC output for supplying the LEDs. According to a preferred embodiment the base has a retrofit adaptor being compatible with Edison type sockets.

The second aspect of the invention also covers one or more embodiments wherein the heat sink is made of an electrically non-conductive material, such as a ceramic material, and thick film conductors are printed directly on the heat sink for supplying power to the LEDs. Here thick film conductors may be printed directly on non-conductive parts of the heat sink and connected to cathode and anode pads of the surface-mount LEDs for supplying power to the LEDs.

According to one or more embodiments of the second aspect of the invention, the heat sink may further have a centre part, which is also supporting the cooling fins. The heat sink may be made of an electrically non-conductive material, such as a ceramic material, and thick film conductors may be printed along the cooling fins allowing a voltage supply to the LEDs. The heat sink may alternatively be made of an electrically conductive material, such as aluminium, and electrically conductive wiring or lines may be arranged at an insulating layer being provided between the heat sink and the conductive wiring or lines, where the conductive wiring or lines are arranged for supplying power to the LEDs.

Also for embodiments of the second aspect of the invention is it preferred that the heat sink has a substantially circular outer circumference.

It should be understood that the second aspect of the present invention covers assemblies having different directions of the emitted light from the LEDs. According to a first embodiment, the LEDs supported by the outer circumference of the heat sink may be arranged so that the main direction of the emitted light is perpendicular to a centre axis of the heat sink. According to another embodiment, the LEDs supported by the outer circumference of the heat sink may be arranged so that the main direction of the emitted light is parallel to a centre axis of the heat sink. In yet another embodiment, the LEDs supported by the outer circumference of the heat sink may be arranged so that the main direction of the emitted light is tilted when compared to a centre axis of the heat sink.

The second aspect of the presenting also covers one or more embodiments, wherein the LED lamp assembly further comprises lenses or a lens being arranged in front of at least part of the LEDs being supported by the outer circumference of the heat sink. Preferably, the lens/lenses covers/cover the LEDs, which are supported by the outer circumference of the heat sink. It is also preferred that the lens/lenses is/are made in one piece. In a preferred embodiment, then for each LED or at least part of the LEDs a corresponding outwardly pointing convex part is formed on the inner surface part of the lens/lenses facing the LED. It is preferred that the lens/lenses is/are made of Silicone. The lens/lenses may be formed so as to spread out the diode light at an angle being wider than the light emission angle of the LEDs or the viewing angle of the LEDs.

The lens or lenses may be formed so as to spread out the diode light at an angle or a wide angle in a main direction equal to the main direction of the light received from the LEDs. However, the lens/lenses may also be formed so as to spread out the diode light in a main direction being at an angle relative to the main direction of the light received from the LEDs. Here, the lens/lenses may be formed so as to spread out the diode light in a main direction being substantially perpendicular to the main direction of the light received from the LEDs. Furthermore, the lens/lenses may be formed so as to spread out the diode light in at least two different main directions, which may be two substantially opposite main directions, and which again may be substantially perpendicular to the main direction of the light received from the LEDs.

According to a third aspect of the present invention there is provided a LED lamp assembly comprising: a heat sink supporting a plurality of LEDs, wherein lenses or a lens are/is arranged in front of at least part of the LEDs. Here, the lens/lenses may be made in one piece, and it may have a substantially ring- or tubular shaped form. The third aspect of the invention covers one or more embodiments, wherein, for each LED or at least part of the LEDs or all of the LEDs, a corresponding outwardly pointing convex part is formed on the inner surface of the lens/lenses, which inner surface is facing the LED. Also for the third aspect of the invention is it preferred that the lens/lenses is/are made of Silicone. According to a preferred embodiment of the third aspect of the invention the heat sink may have an outer circumference part supporting at least part of the LEDs. Here, the outer circumference part of the heat sink may be circumferentially closed. Preferably, lenses, a lens or a lens part are/is arranged in front of each of the LEDs.

The third aspect of the invention covers one or more embodiments wherein lens/lenses are formed so as to spread out the diode light at an angle being wider than the light emission angle of the LEDs.

It is within one or more embodiments of the third aspect of the invention that the lens/lenses are formed so as to spread out the diode light at a wide angle in a main direction equal to the main direction of the light received from the LEDs. The lens/lenses may alternatively be formed so as to spread out the diode light in a main direction being at an angle relative to the main direction of the light received from the LEDs. Here, the lens/lenses may be formed so as to spread out the diode light in a main direction being substantially perpendicular to the main direction of the light received from the LEDs. The third aspect of the invention further covers one or more embodiments, wherein the lens/lenses are formed so as to spread out the diode light in at least two different main directions, which may be two substantially opposite main directions, and where said two opposite main directions may be substantially perpendicular to the main direction of the light received from the LEDs.

According to a fourth aspect of the invention there is provided a LED lamp assembly comprising a heat sink supporting a plurality of LEDs, wherein at least part of the LEDs are surface-mount LEDs, which on the back side have a cathode pad, an anode pad and a thermal pad, and wherein the thermal pads are thermally contacting or mounted to the heat sink. It is preferred that the heat sink or the part of the heat sink being in contact with the LEDs is made of an electrically non-conducting material. Thick film conductors may be printed directly on the non-conductive parts of the heat sink and connected to cathode and anode pads of the surface-mount LEDs for supplying power to the LEDs.

The fourth aspect of the invention also covers one or more embodiments, wherein the surface-mount LEDs are divided into a number of groups with the LEDs of the same group being electrically connected in series, and wherein thick film conductors are printed directly on non-conductive parts of the heat sink and connected to cathode and anode pads of the surface-mount LEDs for providing said series connection of the LEDs.

According to an embodiment of the fourth aspect of the invention, the heat sink has a non-conducting outer circumference part supporting the surface-mount LEDs, where the outer circumference part of the heat sink may be circumferentially closed. Preferably, the heat sink has a cooling structure allowing passage of air, which cooling structure is supported by the outer circumference part and extends inwards from the outer circumference part. The cooling structure may comprise a number of vent-holes and/or a plurality of cooling fins. According to an embodiment of the fourth aspect of the invention, an electrically conducting plate or ring is arranged at the outer circumference part of the heat sink, and a first voltage input to the LEDs may provided via said plate or ring.

For assemblies according to the fourth aspect of the invention it is preferred that the non-conducting parts of the heat sink is made of a ceramic material.

It should be understood that the for the embodiments of the present invention, the expression light emitting diodes, LEDs, also covers organic light emitting diodes, OLEDs.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1ashows a first LED lamp assembly100according to a first embodiment of the invention, wherein the assembly holds a heat sink101mounted with LEDs, andFIG. 2ais a cut through drawing of the heat sink101. The heat sink101has a ring-shaped outer circumference102supporting a number of LEDs103. Grooves104are provided in the heat sink101for receiving the LEDs103. For the assembly shown inFIG. 1a, a ring-shaped groove105is provided at the top of the heat sink101for receiving a ring-shaped top-ring106, which may be made of a conductive material such as metal, which for example could be aluminium, copper or zirconium. The LEDs103are mounted on a substrate having no conductors on the front side, and the top-ring106is formed so as to hold the LEDs103in place by contacting the front side of the diode substrates. For the assembly ofFIG. 1a, the top-ring106may be used for supplying ground voltage to the LEDs103.

Three conic pins110may be used to keep the main body of the heat sink101and the top-ring together106via a bayonet-grip with the top-ring106. The conically shaped pins110are inserted into corresponding holes111from the bottom of the heat sink110, and the conic shape of the pins110holds the heat sink101and the bayonet grip holds the top-ring106. See alsoFIG. 4c.

The heat sink101has a plurality of cooling fins107, which are supported by the outer circumference part102and extending inwards from the outer circumference part102. The width or cross sectional area of the cooling fins107decreases in the inward direction from the outer circumference part102towards the centre of the heat sink108. Thus, the material thickness of the cooling fins107decreases in the inward direction from the outer circumference part102towards the centre108. The cooling fins107are dimensioned so that the area of each of the side surfaces of a cooling fin107is larger than the area of the upper surface and larger than the area of the lower surface of the cooling fin107. The cooling fins107are tilted or partly tilted relatively to a centre axis of the heat sink101, whereby a lower surface part of a first cooling fin107is partly shielding an upper surface part of a following second cooling fin107, when looking downwards at the top surface of the heat sink101.

FIG. 1bshows a second LED lamp assembly200according to a first embodiment of the invention, wherein the assembly holds a heat sink201mounted with LEDs, andFIG. 2bis a cut through drawing of the assembly200and the heat sink201. The heat sink201has a ring-shaped outer circumference202with a groove supporting a number of LEDs203. For the assembly shown inFIG. 1b, a ring-shaped groove205is provided at the top of the heat sink201for receiving a ring-shaped top-ring206, which may be made of a conductive material such as metal, which for example could be aluminium, copper or zirconium. The LEDs203are mounted on a substrate, which may be a flexible printed circuit board204, which is arranged in the groove of the outer circumference202. For the assembly ofFIG. 1b, the LEDs203may be connected in series, and in one embodiment, at zener diode is connected in parallel with each LED203.

Also the heat sink201has a plurality of cooling fins207, which are supported by the outer circumference part202and extending inwards from the outer circumference part202. The width or cross sectional area of the cooling fins207decreases in the inward direction from the outer circumference part202towards the centre of the heat sink208. Thus, the material thickness of the cooling fins207decreases in the inward direction from the outer circumference part202towards the centre208. The cooling fins207are dimensioned so that the area of each of the side surfaces of a cooling fin207is larger than the area of the upper surface and larger than the area of the lower surface of the cooling fin207. The cooling fins207are tilted or partly tilted at an angle relatively to a centre axis of the heat sink201. For the heat sink201ofFIGS. 1band2bit is preferred that the distance between the cooling fins207is so large that the tilted cooling fins207do not shield for each other when looking downwards at the top surface of the heat sink201.

For both heat sinks101and201it is preferred that the tilt angle of the cooling fins107,207decreases from the outer circumference part102,202towards the centre108,208, to thereby increase the airflow. The tilt angle of a cooling fin107,207, may be defined as the angle between a plane going through the centre axis of the heat sink108,208and the upper side surface of the cooling fin107,207. The tilt angle of the cooling fins107,207may at the outer circumference part102,202be in the range of 10-45°, such as in the range of 20-35°, such as in the range of 25-30°, and at the end of the cooling fins107,207, close to the centre108,208, the tilt angle may be below 20°, such as below 10°.

It is preferred that the opening at the centre108,208has a diameter of at least 10 mm.

The cooling fins107,207are almost conic shaped from the outer circumference part102,208towards the centre108,208to obtain an even heat-dissipation and they are tilted to obtain the largest possible surface area with the given mass properties. The heat travels from the outer circumference part102,202into the cooling fins107,207, where the heat leaves the heat sink101,201. Due to the convection of heat travelling upwards when leaving the heat sink101,201, a vacuum may be created and cold air may be drawn in from the bottom of the heat sink101,201.

The heat sinks101,201of the LED light assemblies100,200, both has a center ventilation-hole108,208that is connected to the ventilation area between the conic cooling-fins107,207, which are thickest near the LED heat source103,203. The heat sink constructions have one center ventilation-hole108,208, which creates one collective airflow stream with less resistance as opposed to several small ventilation-holes. The angled climbing cooling-fins107,207force the air between the cooling-fins107,207into a spin like a vortex around the center airflow stream that travels faster due to the convection and free airflow. The heat gets pulled out in between the cooling-fins107,207, which are angled in a way that gives them a larger surface area with the same mass-properties as vertical fins. This causes for a larger surface-area for the heat to dissipate from.

For the heat sinks101,201of the assemblies ofFIGS. 1a,1b, then the outer circumference part of the heat sink101,201may be made of an electrically non-conducting material. For the preferred embodiment, the cooling fins107,207are also made of an electrically non-conducting material, and the whole heat sink101,201may thus be made of an electrically non-conducting material. The electrically non-conducting material may be a ceramic material such as aluminium nitride, AlN. It is preferred that the heat sinks101,201are made in a casting process.

FIG. 2cshows a stacked LED lamp assembly210holding three of the LED assemblies200shown inFIG. 1b. The three LED assemblies211,212, and213are stacked so that the cooling fins207are aligned, whereby the top surface of a cooling fin207of assembly211is aligned with the bottom surface of a cooling fin207of assembly212, and the top surface of a cooling fin207of assembly212is aligned with the bottom surface of a cooling fin207of assembly213.

FIGS. 3aand3bare diagrams illustrating examples of surface-mount LEDs, which may be used in the assemblies ofFIGS. 1aand1b. The LED301ofFIG. 3ais a LUXEON® Rebel type compact, surface-mount, high power LED.302ashows the LED301from the front side, and302bshows the LED301from the back side. The diode part303is arranged on the front side302a, and on the back side302b, the LED301has a cathode pad304, an anode pad305, and a thermal pad306, where the thermal pad306is electrically isolated from the cathode and anode contact pads304,305. When LEDs301,103are arranged in the grooves104of the heat sink101, the thermal pads306are thermally contacting or mounted to the outer circumference part102of the heat sink101.

The LED307ofFIG. 3bis Cree® XLamp® XR-E type LED.308ashows the LED307from the front side, and308bshows the LED307from the back side. The diode part309is arranged on the front side308a, and on the back side308b, the LED307has a cathode pad310, an anode pad311, and a thermal pad312, where the thermal pad312is electrically isolated from the cathode and anode contact pads310,311.

For the assemblies100,200ofFIGS. 1aand1b, the heat sink101,201could also be made of an electrically conductive material, such as aluminium. In this case, the LEDs may be mounted on a printed circuit board, such as a flexible printed circuit board, which is then mounted to the outer circumference part102,202of the heat sink101,102.

FIGS. 4a-4dillustrate an example of electrical connections and mounting of the LEDs103of the assembly100ofFIG. 1a.FIGS. 4aand4bshow the electrical connections for the assembly ofFIG. 1awhen using LEDs of the type301ofFIG. 3b, whereFIG. 4bis an enlarged drawing. For each groove104there is an electrical connection401for the anode305, and an electrical connection402for the cathode304. The groove104is formed so to fit with the thermal pad306. The LEDs103may be divided into a number of groups with the LEDs103of the same group being electrically connected in series, with each group of series connected LEDs103have first and second voltage inputs. The groups of series connected LEDs103may be connected in parallel, where the first voltage inputs are connected to ground or minus of the supply voltage and the second voltage inputs are connected to plus of the supply voltage. However, in another embodiment all the LEDs103may be connected in series.

For the assembly shown inFIGS. 4a-4d, the heat sink101including both the outer circumference part102and the cooling fins107is made of a non-conducting material such as aluminium nitride, AlN. In order to serially connect the LEDs103, metallization tracks403are provided at the outer circumference part102of the heat sink101for connecting the anode401of a first LED103to the cathode402of the next LED103. For a group of series connected LEDs103the first voltage inputs of the groups of LEDs103may be electrically conductive connected to the conducting plate or ring106, and the second voltage inputs of the groups of LEDs103may be electrically connected to corresponding contact plugs arranged at the outer circumference part102of the heat sink101.

FIGS. 4c-4dshow the mounting of the LEDs103of the assembly100ofFIG. 1a, whereFIG. 4dis similar toFIG. 1a. The three conic pins110are used to keep the main body of the heat sink101and the top-ring106together via a bayonet-grip with the top-ring106. The conic pins110are inserted into the openings111of the top ring106, where the openings111are made large enough to make room for contact plugs604for a second voltage input to a corresponding group of LEDs103.

FIGS. 4eand4fillustrate electrical connections and mounting of the LEDs203of the assembly200ofFIG. 1b, whereFIG. 4fis similar toFIG. 1b.FIG. 4eshows the flexible printed circuit board204with the LEDs203mounted thereon. The LEDs203are electrically connected in series by the printed circuit board204.FIG. 4eshows the heat sink201, the flexible printed circuit board204and the top ring206before being assembled. The circuit board204is arranged in the groove in the outer circumference part202, and the top-ring206is arranged at the top groove205to thereby lock the circuit board204holding the LEDs203.

FIG. 5shows a LED lamp assembly according to an embodiment of the invention, wherein the assembly100ofFIG. 1afurther holds a base501with a retrofit adaptor502. The base501is adapted for holding the heat sink101and for providing supply of electrical power to the LEDs103. The base501is attached to the assembly100via three legs503and three plugs504, through which legs503and plugs504power is supplied to the LEDs103. When having groups of series connected LEDs103power is supplied to the second voltage inputs of the groups of LEDs103. The plugs504fits into the opening111of the top ting106. For the embodiment illustrated inFIG. 5, there are three base-legs503and there may be three corresponding groups of series connected LEDs103. The base501shown inFIG. 5has a retrofit adaptor502being compatible with Edison type sockets. The adaptor502of the base501holds driver circuitry for supplying a DC voltage to the LEDs103, where the driver circuitry comprises an AC to DC converter for converting a high-voltage AC input into a DC output for supplying the LEDs. The base501may also be used for the LED lamp assembly200ofFIG. 1b.

FIGS. 6a-6cshows LED lamp assemblies100according to embodiments of the invention, wherein the assembly100ofFIG. 1afurther holds a lens or lenses601for spreading the light from the LEDs103. The lens or lenses601may be shaped as a ring and in different designs depending on which light direction is needed from the lamp assembly. The lens or lenses601may be an optical fiber ring or rings, and it is preferred to use transparent Silicone, which may have a high internal reflection. The lens or lenses601should be designed to fit the outer diameter of the heat sink101and be shaped for directing the light from the LEDS103into a wanted direction. The lens or lenses601may be mounted like a rubber band that can be expanded and placed round the heat sink101.

Thus, the lenses or a lens601may be arranged in front of at least part of the LEDs103, which are supported by the outer circumference of the heat sink101, and the lens/lenses601may cover the LEDs102being supported by the outer circumference of the heat sink101, and the lens/lenses601may be made in one piece.

It is preferred that for each LED103a corresponding outwardly pointing convex part701is formed on the inner surface part702of the lens/lenses601facing the LED103. This is further illustrated inFIG. 7, which is a detailed view of the lens ofFIG. 6ashowing the outwardly convex parts701of the lens601. The convex parts701may be partially cylindrically formed. By using such convex formed parts701in the lens601, the light emitted from the corresponding LED103, may be collected to be more parallel than when emitted from the LED103.

It is preferred that overall design of the lens601is made so as to spread out the diode light at an angle being wider than the light emission angle of the LEDs103or the viewing angle of the LEDs103.

For the assembly ofFIG. 6aand for the lens ofFIG. 7, the outer surface602aof the lens/lenses601lens/lenses is formed so as to spread out the diode light at a wide angle in a main direction equal to the main direction of the light received from the LEDs103. The outer surface602bof the lens/lenses601may also be formed so as to spread out the diode light in a main direction being at an angle relative to the main direction of the light received from the LEDs103, which is illustrated by the assembly ofFIG. 6b, where the outer surface602bof lens/lenses601is formed so as to spread out the diode light in a main direction being substantially perpendicular to the main direction of the light received from the LEDs103. The present invention also covers an assembly, wherein the outer surface602cof the lens/lenses601is formed so as to spread out the diode light in at least two different main directions as illustrated by the assembly ofFIG. 6c. InFIG. 6cthe outer surface602cof the lens601is formed so as to spread out the diode light in two substantially opposite main directions being substantially perpendicular to the main direction of the light received from the LEDs.

It should be understood that the present invention also covers LED lamp assemblies, wherein the assembly200ofFIG. 1afurther holds a lens or lenses, which may be a lens as described in connection withFIGS. 6a-6candFIG. 7.

FIG. 8shows a LED lamp assembly800according to a second embodiment of the invention, wherein the assembly holds a heat sink801mounted with LEDs803. The heat sink is made of an electrically non-conductive material, such as a ceramic material, and thick film conductors804may be printed directly on the heat sink for supplying power to the LEDs803.FIG. 9is a detailed view of the assembly ofFIG. 8showing thick film connector prints804at the heat sink801. The thick film conductors804may be printed directly on non-conductive parts803of the heat sink801and connected to cathode and anode pads of the surface-mount LEDs803for supplying power to the LEDs803. It is preferred that the LEDs803are surface-mount LEDs, which may be of the type shown inFIG. 3b, and which on the back side have a cathode pad, an anode pad and thermal pad, and wherein the thermal pads are thermally contacting or mounted to the heat sink801.

The surface-mount LEDs803may be divided into a number of groups with the LEDs of the same group being electrically connected in series with the printed thick film conductors electrically connecting the LEDs803.

For the assembly800ofFIGS. 8 and 9, the heat sink801comprises a ring-shaped outer circumference802supporting the cooling fins807and the LEDs803and a centre part805also supporting the cooling fins807. The thick film conductors804are printed along the cooling fins807allowing a voltage supply to the LEDs803.

FIGS. 10aand10bshow LED lamp assemblies1000a,1000baccording to a third embodiment of the invention, wherein the assemblies1000a,1000bhold a heat sink1001a,1001bmounted with LEDs1003a,1003band wherein an insulating layer1005a,1005bis provided between the heat sink1001a,1001band conductors1004a,1004bsupplying power to the LEDs1003a,1003b. The heat sink1001a,1001bmay be made of an electrically conductive material, such as aluminium.

FIGS. 11a-cillustrate a LED lamp assembly1100according to a fourth embodiment of the invention. The assembly1100holds a heat sink1101with a ring shaped outer circumference1102for holding the LEDs (not shown). The heat sink1101further has a cooling structure1107with vent-holes1108to allow passage of air.FIG. 11ais a side/top view of the assembly1100, showing that the heat sink1101with the cooling structure1107has the form of a bowl. However, the heat sink1101could also be flat. The size of the vent-holes1108decreases inwards towards the centre1109, but it is preferred that the size of the vent-holes1108is dimensioned so that the area taken up by the vent-holes1108relative to the area of the rigid cooling part surrounding the vent-holes1108increases inwards from the outer circumference part to1102the centre1109of the heat sink1101.

FIG. 11bis a side/bottom view of the assembly1100, andFIG. 11cis a detailed view illustrating the arrangement of electrical conductors1104,1105for supplying power to the LEDs, and further showing a solder pad1106for soldering the thermal pad of the LED to the outer circumference part1102of the heat sink. The heat sink may be made of an electrically non-conductive material, such as a ceramic material, and thick film conductors1104,1105may be printed directly on the heat sink1107,1102for supplying power to the LEDs. The LEDs are surface-mount LEDs, which may be of the type shown inFIG. 3b, and which on the back side have a cathode pad, an anode pad and thermal pad, and wherein the thermal pads may be thermally contacting or mounted to the heat sink1101via soldering1106.

FIGS. 12ais a side view,FIG. 12bis a cut-through view, whereFIG. 12cshows the cut-through line, andFIG. 12dis a bottom view of the LED lamp assembly1100ofFIG. 11.FIG. 12bshows that the material thickness of the cooling structure1107decreases inwards from the outer circumference part1102to the centre1109of the heat sink1101.

In order to obtain a desired amount of light from an assembly according to the present invention, the LEDs103,803,1003may be arranged at the outer circumference of the heat sink101,801,1001with a nearest neighbour distance in the range of 1-3 cm, such as in the range of 1.5-2 cm.

For the assemblies illustrated inFIGS. 1a,1b, the LEDs103,203supported by the outer circumference102,202of the heat sink101,201are arranged so that the main direction of the emitted light is perpendicular to a centre axis of the heat sink101,201, while for the assemblies illustrated inFIGS. 8,9,10a,10b, the LEDs803,1003a,1003bsupported by the outer circumference802,1002a,1002bof the heat sink is arranged so that the main direction of the emitted light is parallel to a centre axis of the heat sink. It should however be understood that the present invention also covers assemblies, wherein the LEDs supported by the outer circumference of the heat sink is arranged so that the main direction of the emitted light is tilted when compared to a centre axis of the heat sink.

For the LED lamp assemblies described in connection withFIGS. 1-12, the light emitting sources, the LEDs, are arranged on or supported by the outer circumference part of the heat sink. For the lamp assemblies ofFIGS. 1,2,11, and12, it is preferred that the heat sinks are designed so that the material thickness of the rigid cooling part or parts of a heat sink decreases inwards from the outer circumference part, where the LEDs may be arranged, towards the centre of the heat sink. It is further preferred that this decrease in material thickness is a continuous decrease. However, the present invention also covers embodiments, wherein the one or more light emitting sources are arranged at or around the centre of the heat sink.

Such embodiments are described in connection with the lamp assemblies ofFIGS. 13-17. Here, the light emitting source may be an arrangement of LEDs, such a for example the PrevaLED® Core light engines from OSRAM, seeFIGS. 18aandb. The PrevaLED® Core light engines come with different numbers of LEDs and thereby with different light intensities, such as from 800-300 lumen. They may all have the same outer diameter about 48 mm, and the LEDs are arranged at the centre within a circle having a diameter of about 16-21 mm.

FIGS. 13a-eillustrate a lamp assembly1300according to a fifth embodiment of the invention, which may be used together with LED light source, such as a PrevaLED® Core light engine, and wherein the heat sink1301comprises a cooling structure with vent-holes1308.FIGS. 13a, bandcare a top view, a side view, and a bottom view of the lamp1300, respectively, showing the heat sink1301with a lampshade1302around the heat sink1301. The lamp1300is supported by a wire1304and an electrical supply wire1305goes through a hole1310in the heat sink and reaches the light source/engine1303arranged at the bottom side of the heat sink1301. It is preferred that a diffuser or diffuser plate1306is arranged below the light source/engine1303.FIG. 13dis a top view of the heat sink1301andFIG. 13eis a bottom view of the heat sink1301. The heat sink1301has a ring shaped outer circumference, and comprises a cooling structure1307with vent-holes1308to allow passage of air. A recess1309is provided at the centre and at the bottom of the heat sink1301. The recess1309is dimensioned to fit a light source/engine1303, such as a PrevaLED® Core light engine, and the recess may have a groove for holding a diffuser1306.

FIGS. 14a-cillustrate a side view, a cut-through view and a top view, respectively, of the heat sink1301of the lamp assembly1300ofFIGS. 13a-e, whereFIG. 14cshows the cut-through line, E-E. As may be seen fromFIG. 14c, the size of the vent-holes1308may decrease inwards towards the centre, and it is preferred that the size of the vent-holes1308is dimensioned so that the area taken up by the vent-holes1308relative to the area of the rigid cooling part surrounding the vent-holes1308increases inwards from the outer circumference part to the centre of the heat sink1301. The cut through view inFIG. 14bshows the recess1309provided for the light source/engine1303. It is also seen from FIG.14bthat there are no through going vent holes1308at the centre part1311of the heat sink1301, where the centre part1311holds the recess1309, which again may hold the light source/engine1303. It is also seen fromFIG. 14bthat the material thickness of the cooling structure1307increases inwards from the outer circumference part towards the centre part1311, where the light source/engine may be arranged. The upper surface of the heat sink1301may have the form of an inverted bowl. The heat sink1301may be made of an electrically non-conductive material, such as a ceramic material. It is preferred that through going vent-holes1308has a size of no less than 0.5 cm2and a length not smaller than 0.7 cm.

FIGS. 15a-eillustrate a lamp assembly1500according to a sixth embodiment of the invention, which may be used together with LED light source, such as a PrevaLED® Core light engine, and wherein the heat sink1501has a folded cooling structure.FIG. 15ais a top view of the lamp1500, whileFIG. 15bis a bottom view of the lamp. The lamp assembly1500is mainly made up of the heat sink1501, and supported by a wire1504with an electrical supply wire1505going through a hole1510in the heat sink1501to reach the light source/engine at the bottom side of the heat sink1501.FIGS. 15c-eillustrate a side view, a cut through view, and a top view, respectively, of the heat sink1501. The heat sink1501has a folded or pleat like cooling structure and no vent-holes. The bottom view ofFIG. 15band the cut through view ofFIG. 15dshows a recess1509provided for the light source/engine. Also here a groove may be provided at the recess1509for holding a diffuser below the light source/engine. It may also be seen fromFIG. 15dthat the material thickness of the cooling heat sink1501increases inwards from the outer circumference part towards the centre part1511, where the light source/engine may be arranged. Thus the volume or relative volume taken up by the rigid cooling part of the heat sink1501increases inwards from the outer circumference part towards the centre part1511. The folded shape of the heat sink1501creates a larger cooling surface when compared to a conventional disc shape of the same diameter. The heat sink1501may have the form of an inverted bowl. The heat sink1501may be made of an electrically non-conductive material, such as a ceramic material.

FIGS. 16a-dillustrate a lamp assembly1600according to a seventh embodiment of the invention, which may be used together with LED light source, such as a PrevaLED® Core light engine, and wherein the heat sink1601comprises a cooling structure with vent-holes or openings1608.FIGS. 16aandbare a top view and a bottom view of the lamp1600, respectively, showing the heat sink1601with a lampshade1602around the heat sink1601. The lamp1600is supported by a wire1604and an electrical supply wire1605goes through the heat sink1601and reaches the light source/engine, which may be arranged at the bottom side of the heat sink1601. Also here a diffuser or diffuser plate may be arranged below the light source/engine.FIG. 16cis a top view of the heat sink1601andFIG. 16dis a bottom view of the heat sink1601. The heat sink1601has a ring shaped outer circumference, and comprises a cooling structure1607with oblong vent-openings1608to allow passage of air. A recess1609is provided at the centre and at the bottom of the heat sink1601. The recess1609is dimensioned to fit a LED light source/engine, such as a PrevaLED® Core light engine, and the recess may have a groove for holding a diffuser below the light source.

FIGS. 17a-cillustrate a side view, a cut-through view and a bottom view, respectively, of the heat sink1601of the lamp assembly1600ofFIGS. 16a-d, whereFIG. 17cshows the cut-through line, G-G. The cut through view inFIG. 17bshows the recess1609provided for the light source/engine. It is also seen fromFIG. 17bthat there are no through going vent-openings1608at the centre part1611of the heat sink1601, where the centre part1611holds the recess1609, which again may hold the light source/engine. It is also seen fromFIGS. 17aand17bthat the material thickness of the cooling structure1607increases inwards from the outer circumference part towards the centre part1611, where the light source/engine may be arranged. The upper surface of the heat sink1601may be flat. The heat sink1601may be made of an electrically non-conductive material, such as a ceramic material.

For the lamp assemblies or heat sinks ofFIGS. 13-17, it is preferred that the heat sinks are designed so that the material thickness of the rigid cooling part or parts of a heat sink increases inwards from the outer circumference part towards the centre of the heat sink, where the LED light source may be arranged. It is further preferred that this increase in material thickness is a continuous increase.

A LED light source/engine which can be used together with the lamp assemblies and heat sinks ofFIGS. 13-17is shown inFIGS. 18aandb, which are top and bottom views, respectively, of a LED light source1800of the type PrevaLED® Core light engines from OSRAM. The LEDs1803are arranged at the bottom and at the centre of the light source1800.

In the above discussion of embodiments of the invention, light emitting diodes, LEDs, have been described for the light sources. It should be understood that the for the embodiments of the present invention, the expression light emitting diodes, LEDs, also covers organic light emitting diodes, OLEDs.