WO2013095102A1

WO2013095102A1 - Led lamp, lamp assembly, housing, material and use thereof, and method therefor

Info

Publication number: WO2013095102A1
Application number: PCT/NL2012/050826
Authority: WO
Inventors: Francois Christian HOEN
Original assignee: CREATIVE LED HOLDING BV
Current assignee: CREATIVE LED HOLDING BV
Priority date: 2011-11-21
Filing date: 2012-11-20
Publication date: 2013-06-27
Anticipated expiration: 2014-05-21
Also published as: NL2008543A; NL2008543C2

Abstract

The invention relates to an LED lamp (2), lamp assembly, housing (6), material and use thereof, and a method therefor. The LED lamp (2) comprises a housing (6); at least one LED (8,20) arranged in or on the housing (6); and at least one contact point (10,12) connected electrically to the at least one LED (10,12), wherein the housing (6) is at least partially manufactured from a light- transmitting and heat-conducting material such that during use the housing (6) discharges the heat produced by the at least one LED (8,20).

Description

LED LAMP, LAMP ASSEMBLY, HOUSING, MATERIAL AND USE THEREOF, AND METHOD THEREFOR

The present invention relates to an LED lamp. An LED lamp comprises one or more LEDs, such as conventional LEDs, OLEDs (organic LEDs) or PLEDs (polymer LEDs) .

Diverse LED lamps are known in practice.

One of the problems of conventional LED lighting is that a cooling body has to be provided to discharge the heat of the LEDs. Such a cooling body is usually manufactured from aluminium. The cooling body takes up a determined amount of space, makes production of the lamp complex and detracts from the appearance of the lamp. A cooling body moreover blocks part of the light.

An object of the invention is to obviate or at least reduce the above stated problems and to provide an LED lamp in which heat is discharged effectively.

The LED lamp according to the invention comprises:

- a housing;

- at least one LED arranged in or on the housing; and

- at least one contact point connected electrically to the at least one LED,

wherein the housing is at least partially manufactured from a light-transmitting and heat-conducting material such that during use the housing discharges the heat produced by the at least one LED.

Within the context of the invention LED is understood to mean OLED or PLED in addition to conventional LED.

Light-transmitting is understood within the context of the invention to mean that in any case a part of the visible light is transmitted.

The housing is for instance a casing which is for instance largely closed, or an open housing.

By manufacturing the housing at least partially from a light-transmitting and heat-conducting material it is possible to dispense with a separate cooling body. This is because the housing functions as cooling body, or at least as heat dissipator. This simplifies production of the LED lamp. The part of the housing which dissipates heat is moreover prevented from blocking light. This increases the efficiency of the LED lamp. Furthermore, the lamp hereby emits the light in all directions. The improved heat dissipation moreover increases the lifespan of the at least one LED.

The housing is for instance manufactured wholly, or in any case for the greater part, from such a material.

The at least one LED is preferably arranged on the housing, or the LED is located close to the housing, such that the LED transfers its heat to the housing effectively. The at least one LED is for instance mounted on an inner wall of a hollow housing, or the LED is for instance located in the material of the housing.

The thermal conductivity of the light-transmitting and heat-conducting material is preferably greater than 10 W m^_1 K^_1, preferably greater than 50 W m^-1 K^_1, still more

preferably greater than 100 W m^_1 K^-1, still more preferably greater than 200 W m^_1 K^_1 and most preferably greater than 300 W m^"1 K^"1.

The thermal conductivity of the material is for instance 221 W m^_1 K^~~. Such a thermal conductivity is many times greater than the thermal conductivity of known light- transmitting materials such as glass or light-transmitting plastics. The thermal conductivity is at the same time preferably similar to the thermal conductivity of non-light- transmitting materials, such as aluminium, which serve as cooling in conventional lighting.

In a preferred embodiment the transmission of the light-transmitting and heat-conducting material is greater than or equal to 60%, and preferably greater than or equal to 75%, more preferably greater than or equal to 90%.

In a preferred embodiment the light-transmitting and heat-conducting material comprises a mixture, the mixture comprising a continuous phase of a light-transmitting material and a dispersed phase of a heat-conducting

material .

The light-transmitting, heat-conducting material comprises a main component which is light-transmitting, thereby achieving that the material as a whole is light- transmitting. The thermal conductivity of the material is increased in that the mixture also comprises a heat- conducting material. The thermal conductivity of the

dispersed phase is for instance ≥ 200 W m^_1 K^_1, preferably ≥ 500 W m^_1 K^_1, more preferably ≥ 1000 W m^_1 K^~~, most

preferably > 2000 m^"1 K^"1.

The material for instance comprises a composite, i.e. a mixture of materials, this composite comprising a material with a high thermal conductivity, for instance a ceramic material and/or a metal and/or metal alloy.

The ceramic material in the composite is for instance aluminium oxide, alumina, aluminium nitride, silicon

carbide, boron nitride, silicon or a silicon-containing composition, graphite, beryllium oxide, quartz or sapphire.

The metal or the metal alloy is for instance copper, silver, iron, steel, aluminium, bronze, zinc or nickel.

The material is for instance a composite comprising a plastic, further comprising a ceramic material or a metal. Alternatively, the material is a composite of one or more ceramic materials and/or one or more metals and/or one or more plastics.

In a preferred embodiment the continuous phase

comprises a plastic, preferably a light-transmitting

plastic.

Plastics have the advantage that they are generally easy to process, are inexpensive and are widely available.

The plastic is preferably a reused or reusable plastic. In a further preferred embodiment the plastic comprises polycarbonate. Polycarbonate has the advantage that it is a hard material with a high melting temperature. This realizes a robust LED lamp. Polycarbonate moreover has a low expansion coefficient so that the heat during use causes hardly any expansion of the LED lamp.

In a preferred embodiment the dispersed phase comprises carbon particles.

Carbon particles such as carbon nanotubes (CNT) and graphene have a very high thermal conductivity.

The properties of CNT are that the coefficient of conductivity amounts to about 6600 m^-1 K^-1, which is about twice as high as diamond, which was formerly the best-known heat conductor, the tensile strength amounts to about 63 GPa, the tensile strength of steel being about 2 GPa, and the surface area/weight ratio lies in the range of 100-200 m²/g .

The carbon particles preferably comprise graphene and/or carbon nanotubes.

Alternatively or additionally, the dispersed phase comprises a different carbon allotrope such as graphite.

Use is preferably made according to the invention of a mixture formed from CNT and polycarbonate, known as "Borea" . Mixing and heating CNT and polycarbonate creates a substance which provides a plastic with cooling properties. It has been found as a result that the conventional aluminium cooling bodies are unnecessary.

In addition, such a material can be applied in all types of LED chip for the purpose of discharging heat.

A further advantage of the lamp in a currently

preferred embodiment according to the invention is that a fully light-transmitting mixture becomes possible, whereby a 360 degree radiation behaviour is realized. In the case of an LED lamp in the form of an LED tube, full use is thus made of the reflectors in fittings for fluorescent tubes.

In an alternative embodiment according to the invention a closed rear side is provided for the lamp so that it is suitable for downlight application where a reflection by a reflector is not essential. Both types of lamp preferably make use of the Borea technique in order to discharge heat.

In conventional LED lighting use is made of aluminium cooling bodies integrated with the housing. These have the drawback of not allowing passage of light, whereby the emission angle of the LED lamp decreases dramatically. The typical emission angle in a conventional LED tube is for instance 120 degrees. An LED tube according to the invention achieves a greater emission angle, even up to 360 degrees.

Since the housing of the LED lamp according to the invention forms the cooling body and no separate aluminium cooling body need be provided, there is more space in the housing to accommodate the at least one LED.

In a preferred embodiment the housing is tubular and the at least one LED is located eccentrically relative to the longitudinal central axis of the housing.

In the case of an LED tube the at least one LED is preferably provided on one side of the longitudinal axis of the LED tube. This increases the emission angle toward the opposite side. A number of LEDs are for instance provided on a printed circuit board. The printed circuit board is not placed centrally but more toward one side of the tube, whereby the emission angle is increased in the direction away from the LEDs. In other words, the printed circuit board lies to one side of the longitudinal axis of the LED tube .

The material of the housing can optionally comprise a luminescent, phosphorescent or fluorescent substance. This provides for an increased light output in the desired wavelength range.

In a preferred embodiment according to the invention the LED lamp comprises a power supply connected to the at least one LED and preferably accommodated in or arranged on the housing. In conventional LED lighting a separate power supply has to be provided for powering the LEDs . The power supply for instance comprises a transformer for converting mains voltage to a voltage suitable for LEDs. Such an external power supply makes installation of a conventional LED lamp time-consuming and complicated.

Compared to conventional LED lighting, the LED lamp according to the invention has the advantage that the power supply is integrated. An LED tube according to the invention can for instance hereby replace a fluorescent tube one for one. An easy installation of the LED tube is hereby

realized. This is because an LED tube according to the invention can be placed in existing fittings for fluorescent tubes since no external power supply component need be provided. This in contrast to conventional LED tubes, for which such an external power supply is required.

In a preferred embodiment of the LED lamp according to the invention the power supply comprises a power supply chip, also referred to as microchip.

The at least one LED is preferably provided on a printed circuit board (PCB) . The power management is preferably controlled here by the microchip of the lamp according to the invention. This has the advantage that a separate external power supply is not required, and the LED lamp according to the invention can be applied in existing fittings. An LED lamp according to the invention in the form of an LED tube is therefore preferably interchangeable with conventional lighting tubes, such as fluorescent tubes.

According to the invention a power supply chip is alternatively applied in another type of LED lamp, for instance without the light-transmitting and heat-conducting housing material. In other words, the invention also relates to an LED lamp comprising a housing, at least one LED arranged in or on the housing, at least one contact point connected electrically to the at least one LED and a power supply, preferably a power supply chip, connected to the at least one LED.

The LED lamp according to the invention optionally comprises dimmer means operatively connected to the LEDs for the purpose of dimming the at least one LED.

In a further preferred embodiment the LED lamp

comprises a safety switch for automatically creating and/or breaking electrical contact with the at least one contact point of the LED lamp during placing or removing of an LED lamp in or from a fitting. This is particularly advantageous in an embodiment as LED tube.

A fluorescent tube generally has on both its outer ends a contact point for connection to a fitting. The fitting comprises contact points connected to the mains which, after placing of the fluorescent tube in the fitting, connect to the contact points at both outer ends of the fluorescent tube so that the fluorescent tube is powered. In LED tubes however the two outer ends are usually connected

electrically to each other so that there is a risk of an electric shock or damage to the LEDs during placing of the LED tube.

The safety switch in the LED lamp according to the invention reduces or avoids this drawback. By automatically breaking the electrical connection of the contact points to the LEDs when the LED lamp is not fully placed in the fitting, no current can flow through the LEDs. The switch automatically closes the connection between the contact points and the LEDs as soon as the LED lamp has been placed correctly in the fitting.

The outer ends of the housing of the LED tube according to the invention can, if desired, be provided with end parts, so-called end caps. The end caps are preferably adhered to the housing.

The safety switch is preferably embodied as a

microswitch. The microswitch is preferably arranged at the outer ends of the LED lamp, for instance integrated into an end cap.

The LED lamp according to the invention is for instance cylindrical or rectangular. Other shapes are also possible according to the invention.

The housing is for instance liquid-tight and the housing comprises a liquid, such as an oily liquid, for the purpose of discharging heat from the LEDs.

The invention further relates to a lamp assembly comprising an LED lamp as described above and a fitting, a housing, a material and the use thereof, and a method for manufacturing an LED lamp as described above.

The features, advantages and effects described for the LED lamp according to the invention also apply to the lamp assembly, the housing, the material and the use thereof, and the method according to the invention.

The features of the above described embodiments can be combined as desired in the LED lamp, the lamp assembly, the housing, the material and the use thereof, and the method according to the invention.

The housing according to the invention is preferably a housing for an LED lamp. In respect of the material

according to the invention the continuous phase preferably consists wholly of polycarbonate. The dispersed phase preferably consists wholly of carbon nanotubes and/or graphene . The dispersed phase preferably comprises carbon nanotubes and/or graphene in a weight percentage or volume percentage of between 0% and 20%, more preferably between 0 and 15%, still more preferably between 0 and 10% and most preferably between 1 and 10%. The volume or weight

percentage is for instance 3-10%. The use according to the invention preferably comprises the use of the material according to the invention to manufacture a housing for a lamp, preferably an LED lamp.

Further advantages, features and details of the invention are elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

- Figure 1 shows a lamp assembly according to the

invention with an LED tube and a fitting;

- Figure 2 shows the LED tube of figure 1 ;

- Figure 3 shows the interior of the LED tube of figures 1 and 2 ;

- Figure 4 shows a schematic representation of a prior art LED lamp; and

- Figure 5 shows a schematic representation of an LED lamp according to the invention.

Lamp assembly 2 (figure 1) comprises fitting 4 in which an LED tube 6 is placed. LED tube 6 (figure 2) comprises an end part 8, also referred to as end cap. End cap 8 is provided with plug pins 10, 12 which serve as electrical contact point. Also provided on end cap 8 is a microswitch 14 which is electrically connected to plug pins 10, 12.

Provided on the inside of tube 6 is a printed circuit board 16 on which LEDs 18, 20 are arranged. LEDs 18, 20 are electrically connected to plug pins 10, 12 via a microchip 22. This microchip 22 provides for the power management of LEDs 18, 20.

The overall length of this embodiment amounts to 1172 mm. Three types are applied, respectively type A of 396.35 mm for 220 V and 397 mm for 120, 100 V, type B of 380 mm for 100, 120 and 220 V, and type C of 395.65 mm for 220 V and 395 mm for 120 and 100 V. The overall height is 2.2 mm, wherein the ICs protrude about 2 mm above the other parts.

The thermal conductivity of this embodiment amounts to about 221 W/mK, the transmittance to about 90% and the density to about 2.680 kg/dm³.

Tube 6 is provided for this purpose with a material with polycarbonate as light-transmitting continuous phase and carbon nanotubes as heat-conducting dispersed phase.

In the shown embodiment the end caps 8 are provided with a microswitch 14 as safety against electric shocks. In this embodiment end caps 8 are glued and therefore not screwed.

Figure 4 shows an electrical circuit diagram of a prior art LED lamp 24, comprising an alternating voltage source 26, an AC/DC converter 30 and one or more LEDs 28. The electrical circuit diagram of an LED lamp 32 (figure 5) according to the invention comprises an alternating voltage source 34, one or more LEDs 36, an overvoltage protection 38 with a resistor and a voltage regulator, a circuit 40 for reducing electromagnetic interference (EMI) with a capacitor and optionally a circuit 42 for preventing flickering.

Integrated circuit 44 is also provided.

From a comparison between a prior art LED lamp 24 (figure 4) and an LED lamp 32 according to the present invention (figure 5) there emerge a number of differences.

Lamp 32 is thus provided with a configuration which requires only a limited number of electronic components for the AC control and which is further relatively simple compared to conventional lamp 24. In addition, the space required for the circuit for lamp 24 is about 18.5 by 20 mm, and for the similar conventional lamp 32 about a few hundred mm². For lamp 24 the power factor amounts to about 0.97 and for conventional lamp 32 about 0.75-0.85. The lifespan under similar conditions varies from about 40,000 hours for lamp 24 to about 15,000 hours for conventional lamp 2.

The invention is by no means limited to the above described preferred embodiments thereof. The rights sought are defined by the following claims, within the scope of which many modifications can be envisaged.

Claims

1. LED lamp, comprising:

- a housing;

- at least one LED arranged in or on the housing; and

- at least one contact point connected electrically to the at least one LED,

2. LED lamp as claimed in claim 1, wherein the thermal conductivity of the light-transmitting and heat-conducting material is greater than 10 m^_1 K^-1, preferably greater than 50 W m^_1 K^-1, still more preferably greater than 100 m^~~ K^-1, still more preferably greater than 200 W m^-1 K^_1 and most preferably greater than 300 m^_1 K^-1.

3. LED lamp as claimed in claim 1 or 2, wherein the

transmission of the light-transmitting and heat-conducting material is greater than or egual to 60%, preferably greater than or equal to 75%, more preferably greater than or equal to 90%.

4. LED lamp as claimed in claim 1, 2 or 3, wherein the light-transmitting and heat-conducting material comprises a mixture, the mixture comprising a continuous phase of a light-transmitting material and a dispersed phase of a heat- conducting material.

5. LED lamp as claimed in claim 4, wherein the continuous phase comprises a plastic.

6. LED lamp as claimed in claim 5, wherein the plastic comprises polycarbonate.

7. LED lamp as claimed in claim 4, 5 or 6, wherein the dispersed phase comprises carbon particles.

8. LED lamp as claimed in any of the claims 1-7, wherein the housing is tubular and the at least one LED is located eccentrically relative to the longitudinal central axis of the housing.

9. LED lamp as claimed in any of the claims 1-8, comprising a power supply connected to the at least one LED.

10. LED lamp as claimed in claim 9, the power supply comprising a microchip.

11. LED lamp as claimed in claim 9 or 10, the power supply comprising dimmer means.

12. LED lamp as claimed in any of the claims 1-11,

comprising a safety switch for automatically creating and/or breaking electrical contact with the at least one contact point during placing or removing of the LED lamp in or from a fitting.

13. LED lamp as claimed in any of the claims 1-12, wherein the housing is liguid-tight and comprises a liguid,

preferably an oily liguid.

14. Lamp assembly comprising a fitting and an LED lamp as claimed in any of the claims 1-13.

15. Housing for a lamp which is at least partially

manufactured from a light-transmitting and heat-conducting material such that during use the housing discharges heat.

16. Material comprising a mixture comprising a continuous phase of a light-transmitting material and a dispersed phase of a heat-conducting material, wherein the light- transmitting material comprises polycarbonate and the heat- conducting material comprises carbon particles.

17. Use of a material as claimed in claim 16 for application in a housing of a lamp.

18. Method for manufacturing an LED lamp as claimed in any of the claims 1-13, comprising the step of manufacturing at least a part of the housing of the LED lamp from a light- transmitting and heat-conducting material such that during use it discharges heat produced by the at least one LED.