WO2014102642A1

WO2014102642A1 - Lighting assembly

Info

Publication number: WO2014102642A1
Application number: PCT/IB2013/060836
Authority: WO
Inventors: Jianhong CHEN
Original assignee: Koninklijke Philips N.V.
Priority date: 2012-12-24
Filing date: 2013-12-12
Publication date: 2014-07-03

Abstract

A lighting assembly (120) comprising a lighting unit (116), which comprises a light source (102) thermally coupled to a first heat dissipating element (100), and a driver unit (118) which comprises light source driver electronics (104) thermally coupled to a second heat dissipating element (106), wherein both of the light source (102) and the driver electronics (104) are arranged intersecting with a same plane perpendicular to an optical axis (114) of the lighting assembly (120).

Description

LIGHTING ASSEMBLY

FIELD OF THE INVENTION

The invention relates to a lighting assembly. In particular, the invention relates to a cooling arrangement for a lighting assembly.

BACKGROUND OF THE INVENTION

The development of new and more energy efficient illumination devices is one of the important technical challenges which society faces. A popular technology which is more efficient than traditional lighting (e.g. incandescent bulbs) is based on Light Emitting Diodes (LEDs). An easy way to save energy in an ordinary household is to use LED lamps instead. A LED lamp can be made to look and feel like an incandescent bulb but with LEDs emitting the light. Many different models of LED lamps are already on the market today and they most often include a DC converter to drive the LEDs.

A LED lamp can save energy compared to traditional lighting, which will make LEDs widely used in the future. LEDs also have a much longer lifetime which may decrease environmental impact from production of lamps. However, in an ordinary LED lamp 75%~85% of the energy provided will be converted to heat. Consequently, there is a need to use high power LEDs to produce enough lighting for most ordinary indoor applications as efficient as possible. However, these high power LEDs also produce heat. High demands are therefore put both on the LEDs but also on their driver circuits to deliver high lumen output at a high temperature.

In a LED lamp the driver circuits are often provided integrated in the lamp, these driver circuits convert an AC voltage into a DC voltage which is then used by the LEDs. These driver circuits will also produce heat when converting the voltage, and the driver components for a driver circuit able to provide more power must also be able to withstand higher temperatures. If the heat is not managed in a LED lamp, the light output and lifetime will be reduced. In US2012/0147600, the aforementioned issues relating to thermal management are addressed through an LED lamp having a thermally conductive body. The thermally conductive body also has cavities and openings for allowing air to flow through the body to cool the entire LED lamp.

SUMMARY

With regards to the above-mentioned desired properties of an LED lighting arrangement, it is a general object of the present invention to enable improved performance of a lighting arrangement through improved cooling of the light source and the driver electronics.

It is also an object of the present invention to enable further choice in components for LED lighting.

According to a first aspect of the invention, these and other objectives are achieved through a lighting assembly comprising a lighting unit which comprises a light source thermally coupled to a first heat dissipating element and a driver unit which comprises light source driver electronics thermally coupled to a second heat dissipating element wherein both of the light source and the driver electronics are arranged intersecting with a same plane perpendicular to an optical axis of the lighting assembly.

By lighting assembly it should be understood that the purpose of the device is to provide lighting, and that the lighting unit with a light source is the main component providing this function.

An optical axis is defined as an axis around which there is rotational symmetry of the light output from an optical system. The central axis of a lighting assembly is typically aligned with the optical axis of the lighting assembly.

Furthermore, the assembly is essentially divided into two parts, a lighting unit and a driver unit, where the driver unit comprises the driver electronics capable of driving the light source. This divide makes it possible to provide each unit with a separate heat dissipating element, which may in turn enable a reduced thermal coupling between the two units. The present invention is based on the realization that by thermally separating the light source and light source driver electronics from each other a lower temperature can be achieved, during use, in the entire assembly. In particular, components of the driver electronics circuitry, such as electrolytic elements in the form of capacitors, may be more sensitive to high

temperatures than the light source. For example, a light source such as an LED may operate at 125°C while conventional components for driver electronics may fail at temperatures around 80°C. Accordingly, it is desirable to arrange the thermally sensitive driver components in a cooler area where they are better protected from high temperatures. Additionally, even though suitable high-temperature components may be available, they are in general much more expensive than conventional components.

Moreover the light source and driver electronics are arranged intersecting with a plane perpendicular to the optical axis of the lighting assembly. In other words, the light source and the driver electronics are arranged laterally with respect to the optical axis. This arrangement may, when the lighting assembly is arranged with its optical axis in an essentially vertical plane, provide a lower heat conduction between the light source and light source driver electronics than the prior art. Although there may be some displacement between the light source and driver electronics along the direction of the optical axis, they are at the substantial same level. In contrast, in the prior art, the light source and the driver electronics are arranged in essentially a vertically stacked manner, which allows heat to be conducted vertically between the light source and light source driver electronics. Air being heated from the light source and light source driver electronics will rise due to the lower density of warm air. When the light source and light source driver electronics are arranged, as in the prior art, in an essentially vertical manner, the warm air rising from the light source will heat the light source driver electronics. The light source driver electronics must then be able to provide the same effect at a higher temperature. A lighting assembly according to the present invention may provide lower heat conduction between the light source and light source driver electronics, which may lower the overall temperature of both the light source and light source driver electronics. The present invention may thus allow the light source driver electronics to provide a higher effect than before at the same temperature due to improved cooling, or provide lower energy consumption due to higher efficiency of the light source driver electronics at lower temperatures.

Furthermore the lower temperature may allow other materials to be used in manufacturing the lighting assembly, which may be cheaper and/or enable a simpler manufacture of the components. Lower heat conduction may thus be achieved since air in the proximity of either the light source or the light source driver electronics which is heated will rise, but heated air does not pass the other component since they are arranged essentially in the same horizontal plane.

Additionally, by decreasing the thermal coupling between the light source and the light source driver electronics resulting from rising warm air, the present invention enables a design where energy may be saved due to a higher efficiency of the light source driver electronics, or a higher lumen output may be achieved from the lighting assembly without inferring additional thermal protection, fabrication costs may also be lowered through use of different materials.

According to one embodiment of the invention, the lighting assembly may further comprise a connecting portion in a connecting end of the lighting assembly for connecting the lighting assembly to a socket, and a light output end opposite of the connecting end of the lighting assembly, wherein the lighting unit and the driver unit are arranged in the light output end.

By arranging the lighting unit and the driver unit at the light output end, adjacent to each other, in a plane perpendicular to an optical axis of the lighting assembly, a lower heat coupling may be ensured as heated air from either unit does not affect the other. The light output end is in the opposite end of the lighting assembly with respect to the connecting end along the optical axis. In many lighting applications, lighting assemblies are directed downwards to provide an aesthetically pleasing lighting indoors. This will, in use, place the light output end with the lighting unit and driver unit, which in use produces heat, at a lower part of the lighting assembly. An adequate separation in distance between a connecting socket and the heat producing components of the lighting assembly may then be allowed due to the arrangement of the driver unit and lighting unit at the light output end. This separation in distance may enable air circulation around the heat dissipating elements.

In one embodiment of the invention, the second heat dissipating element may surround a portion of the first heat dissipating element.

Surrounding a portion of the first heat dissipating element with the second heat dissipating element enables the possibility of an advantageous placement of the light source and the light source driver electronics, where the driver unit may surround the lighting unit instead of being placed adjacent laterally, which may enable a lighting assembly having a shape similar to conventional incandescent bulbs.

According to another embodiment of the invention, the second heat dissipating element may surround a portion of the first heat dissipating element at the light output end. As the surrounding portion is in direct contact with the ambient air, cooling of the surrounding portion may be more efficient. Accordingly, it may be advantageous to arrange the second heat dissipating element of the more thermally sensitive driver electronics adjacent to the surrounding air.

According to another embodiment of the invention the driver unit may surround a portion of the lighting unit comprising said light source. By surrounding a portion of the lighting unit comprising the light source with the driver unit, thermal separation may be enabled between the light source and the light source driver electronics. When the lighting assembly is arranged in an essentially vertical plane, air which may be heated indirectly or directly by the light source or the light source driver electronics will rise, but not impinge upon and heat the other component since it is ensured that the light source and light source driver electronics are both in a plane perpendicular to the essentially vertical plane. In one embodiment of the invention, the light source and the light source driver electronics may be arranged adjacent to each other. This allows a compact size of the lighting assembly.

According to one embodiment of the invention the lighting assembly may also further comprise a thermally insulating material arranged between the lighting unit and the driver unit. It may be the case that further thermal separation is desired between the driver unit and the lighting unit, for instance where a high lumen output is desired which requires high power. It may therefore be advantageous to arrange a thermally insulating material in between the driver unit and the lighting unit for further thermal separation. The insulating material could also be an absence of material where a spacing in itself provides thermal insulation i.e. the material in question would then be air, vacuum or another gaseous compound with low thermal conductivity.

According to another embodiment of the invention, the first heat dissipating element may further comprise; a plurality of cooling fins and at least one cavity having a first opening at the light output end of the lighting unit and a second opening adjacent to the plurality of cooling fins, such that when the lighting unit is arranged with its optical axis in an essentially vertical plane, ambient air is allowed to enter the first opening, pass through the cavity and exit the cavity through the second opening, wherein the cooling fins are arranged such that air pass the cooling fins when leaving the at least one cavity. To further increase thermal dissipation to the surrounding from the lighting assembly, the cooling fins will increase the area able to dissipate heat to the surrounding air through convection, and to even further dissipate heat through radiation. Furthermore, when the lighting assembly is oriented in an essentially vertical direction such that the first opening at the light output end and the second opening adjacent to the cooling fins are essentially aligned vertically, the cavity defining a chimney, will together with the cooling fins create a "chimney" effect. The chimney effect results in ambient air being pulled through the cavity which will further increase thermal dissipation. The ambient air is generally colder than the air which has passed by the cooling fins, which will increase the cooling effect which the air has on the cooling fins. According to another embodiment of the invention, each of the plurality of cooling fins may be extending radially from the optical axis of the lighting unit. This embodiment may advantageously even further increase the available surface area for dissipating heat to the surrounding environment.

According to another embodiment of the invention, the at least one cavity may be aligned with the optical axis of the lighting assembly. By aligning the cavity with the optical axis of the lighting assembly, the cavity will advantageously as mentioned above be placed in an essentially vertical plane as the present lighting assembly is preferably oriented vertically to enable the advantageous cooling features. This will as mentioned enable the cavity together with the cooling fins to create a "chimney" effect and pull ambient air through the cavity. An essentially vertical orientation of the lighting assembly and chimney may thus create the most efficient cooling conditions.

According to another embodiment of the invention the lighting assembly may further comprise potting material encasing the light source driver electronics to conduct heat from the light source driver electronics to the second heat dissipating element which encases the potting material. By further encasing the light source driver electronics in potting material the light source driver electronics will be able to conduct heat more efficiently to the second heat dissipating element, whereby the light source driver electronics may produce more power, or they may be manufactured by other less costly materials, materials having a smaller environmental impact or materials producing more heat at the same power.

According to another embodiment of the invention the potting material may advantageously be made from at least one from a group of silicon oil, micro silica powder and asphalt, or a mixture thereof, which are materials with a thermal conductivity which is advantageous for use as potting material.

According to another embodiment of the invention, the first heat dissipating element further comprises a coating for increasing thermal radiation from the first heat dissipating element. By increasing the thermal radiation even further, even more heat dissipation to the surrounding is enabled, which will as discussed above enable a higher lumen output from the assembly and/or a different choice of materials used in the lighting assembly.

In one embodiment of the invention, the first heat dissipating element may further comprise a coating for increasing thermal radiation from the first heat dissipating element, where the coating is black and/or white paint. Black and/or white paint may advantageously be used as coating to improve the emissivity of the surface, which may in turn increase the heat radiation and thus the heat dissipated to the surrounding.

According to one embodiment of the invention the lighting assembly may further comprise an optical element arranged in front of the light source, where the optical element may further comprise an opening aligned with the first opening of the first heat dissipating element for allowing air to enter the cavity. Introducing an optical element in front of the light source may protect the light source from contact with the outside environment and protect the light source from e.g., dust.

According to another embodiment of the invention, the optical element may be a lens. A lens will advantageously enable many effects such as focusing or dispersing the light from the light source depending on what type of lens is chosen.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

This and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an embodiment of the invention.

Fig. 1 schematically illustrates an exploded view of the lighting assembly according to an embodiment of the invention; Fig. 2 is a schematic representation of the lighting assembly; and Fig. 3 is a cross-section view of the lighting assembly illustrated in Fig.

2. DETAILED DESCRIPTION OF THE DRAWINGS

In the present detailed description, an embodiment of a lighting assembly according to the present invention is mainly discussed with reference to a lighting assembly comprising an LED light source. It should be noted that this by no means limit the scope of the invention, which is also applicable in other circumstances, for example for use with other types of light sources.

The invention will now be described with reference to the enclosed drawings where first attention will be drawn to the structure, and secondly, functions of the lighting assembly will be described.

In Fig. 1 the lighting assembly 120 is represented through an exploded view drawing, where the first heat dissipating element 100 and a printed circuit board (PCB) 102 comprising a light source (not shown), arranged towards the light output end 1 10 is shown. The first heat dissipating element 100 further comprises cooling fins 130 for improving the heat dissipation. The first heat dissipating element 100 and the PCB 102 comprising the light source 102 together form the lighting unit 1 16. Furthermore, the connecting end 1 12 with a connecting portion 122 of the lighting assembly 120 is shown.

Light source driver electronics 104 are mounted on a printed circuit board 105, to be arranged within a second heat dissipating element 106. Together, the PCB 105 comprising the light source driver electronics 104 and the second heat dissipating element 106 form the driver unit 1 18. The driver unit 1 18 further comprises potting material 108, which is to be placed in the second heat dissipating element 106 enclosing the driver electronics 104 in order to provide a thermal coupling between the driver electronics 104 and the second heat dissipating element 106. An optical element 109 in the form of a lens is also shown arranged between the light source 102 and the light output end 1 10 of the lighting assembly 120.

The lighting assembly 120 has a shape as shown in Fig. 1 , where the lighting assembly 120 is essentially rotationally symmetric around an optical axis 1 14.

In Fig. 2, a schematic representation where the lighting assembly 120 of Fig. 1 is assembled, is shown. The portion of the lighting unit 1 16

comprising the light source 102 is surrounded towards the light output end by the driver unit 1 18 comprising the driver electronics 104, and the light source 102 and the driver electronics 104 are thereby arranged adjacent to each other in a plane perpendicular to the optical axis 1 14 of the lighting assembly 120.

Functional aspects from the features of the lighting assembly 120 will now be explained together with Fig. 3 which is a cross-section view of the assembled lighting assembly illustrated in Fig. 2.

In Fig. 3, the air flow entering the lighting assembly 120 and the air flow exiting the lighting assembly 120 is illustrated by arrow 124. When ambient air has entered the cavity 126 the ambient air passes the cooling fins 130, the cooling fins 130 and ambient air exchange heat. The heated air will rise and more ambient air will be pulled into and through the cavity 126 defining a chimney along the path of the airflow 124. The lighting assembly 120 is advantageously mounted with the optical axis 1 14 in an essentially vertical orientation, where the connecting portion 122 is the highest point of the lighting assembly 120.

Furthermore, the lighting unit 1 16 comprising the first heat dissipating element 100 and the light source 102, and the driver unit 1 18 comprising the second heat dissipating element 106 and the light source driver electronics 104 are arranged adjacent to each other in a plane perpendicular to the optical axis 1 14 of the lighting assembly 120, where the driver unit 1 18 surrounds a portion of the lighting unit 1 16 comprising the light source 102. If the lighting assembly 120 is mounted with the optical axis 1 14 in an essentially vertical plane this arrangement may further reduce the thermal coupling between the driver unit 1 18 and the lighting unit 1 16 since heated air rising from the lighting unit 1 16 will not impinge upon the driver unit 1 18.

The driver unit 1 18 further comprises potting material 108 which is comprised of silicon oil and micro silica powder which conducts heat more efficient to the second heat dissipating element 106, from the light source driver electronics 104. Alternatively, potting material 108 may be asphalt or a mixture of similar materials.

Moreover the physical contact area 128 between the driver unit 1 18 and the lighting unit 1 16 illustrated in Fig. 3 may further comprise a thermally insulating material inserted to further reduce the thermal connection between the driver unit 1 16 and the lighting unit 1 18. The thermally insulating material would increase the spacing between the driver unit 1 18 and the lighting unit 1 16, but would not essentially otherwise change any structural details of the lighting assembly 120.

The lighting assembly 120 further comprises an optical element 109 in the form of a lens. This optical element 109 will protect the light source 102 from the outside environment and may also in the form of a lens produce features such as but not limited to focusing the light emitted from the light source or dispersing it.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. For example the light source could be a laser, OLED, or another material or device producing light. The connecting end may be shaped in another way or angled or slightly angled for fitting into a non-standard socket. The optical element might be colored or produced from a luminescent material which converts the light into another wavelength or wavelength spectra. The cooling fins may extend all the way to the opening at the light output end, or they may be arranged in another configuration.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measured cannot be used to advantage.

Claims

1 . A lighting assembly (120) comprising:

a lighting unit (1 16) comprising a light source (102) thermally coupled to a first heat dissipating element (100); and

a driver unit (1 18) comprising light source driver electronics (104) thermally coupled to a second heat dissipating element (106);

wherein both of said light source (102) and said driver electronics (104) are arranged intersecting with a same plane perpendicular to an optical axis (1 14) of said lighting assembly (120).

2. The lighting assembly (120) according to claim 1 , further comprising:

a connecting portion (122) in a connecting end (1 12) of said lighting assembly (120) for connecting said lighting assembly (120) to a socket; and a light output end (1 10) opposite of said connecting end (1 12) of said lighting assembly (120);

wherein said light source (102) and said driver electronics (104) are arranged in said light output end (1 10).

3. The lighting assembly (120) according to claim 1 or 2, wherein said second heat dissipating element (106) surrounds a portion of said first heat dissipating element (100).

4. The lighting assembly (120) according to claim 2 or 3, wherein said second heat dissipating element (106) surrounds a portion of said first heat dissipating element (100) at said light output end (1 10).

5. The lighting assembly (120) according to any one of the preceding claims, wherein said driver unit (1 18) surrounds a portion of said lighting unit (1 16) comprising said light source (102).

6. The lighting assembly (120) according to any one of the preceding claims, wherein said light source (102) and said light source driver electronics (104) are arranged adjacent to each other.

7. The lighting assembly (120) according to any one of the preceding claims, further comprising a thermally insulating material arranged between said lighting unit (1 16) and said driver unit (1 18).

8. The lighting assembly (120) according to any one of the preceding claims, wherein said first heat dissipating element (100) further comprises;

a plurality of cooling fins (130); and

at least one cavity (126), having a first opening at the light output end (1 10) of said lighting unit (1 16) and a second opening adjacent to said plurality of cooling fins (130), such that when said lighting unit (1 16) is arranged with its optical axis (1 14) in an essentially vertical plane, ambient air is allowed to enter said first opening, pass through said cavity (126) and exit said cavity (126) through said second opening;

wherein said cooling fins (130) are arranged such that air pass said cooling fins (130) when leaving said at least one cavity (126).

9. The lighting assembly (120) according to claim 8, wherein each of said plurality of cooling fins (130) is extending radially from an optical axis (1 14) of said lighting assembly (120).

10. The lighting assembly (120) according to claim 8 or 9, wherein said at least one cavity (126) is aligned with the optical axis (1 14) of said lighting assembly (120).

1 1 . The lighting assembly (120) according to any one of the preceding claims, further comprising; potting material (108) encasing said light source driver electronics (104) to conduct heat from said light source driver electronics (104) to said second heat dissipating element (106) which encases said potting material (108).

12. The lighting assembly (120) according to claim 1 1 , wherein said potting material (108) is made from at least one from a group of silicon oil, micro silica powder and asphalt, or a mixture thereof.

13. The lighting assembly (120) according to any one of the preceding claims, wherein said first heat dissipating element (100) further comprises a coating for increasing thermal radiation from said first heat dissipating element (100).

14. The lighting assembly (120) according to any one of the preceding claims, wherein said lighting assembly (120) further comprises an optical element (109) arranged in front of said light source (102), wherein the optical element (109) comprises an opening aligned with said first opening configured to allow air to enter said opening.

15. The lighting assembly (120) according to claim 14, wherein said optical element (109) is a lens.