IES84104Y1 - A utility lamp - Google Patents
A utility lamp Download PDFInfo
- Publication number
- IES84104Y1 IES84104Y1 IE2005/0086A IE20050086A IES84104Y1 IE S84104 Y1 IES84104 Y1 IE S84104Y1 IE 2005/0086 A IE2005/0086 A IE 2005/0086A IE 20050086 A IE20050086 A IE 20050086A IE S84104 Y1 IES84104 Y1 IE S84104Y1
- Authority
- IE
- Ireland
- Prior art keywords
- reflector
- lamp
- leds
- base
- wall
- Prior art date
Links
- 239000004593 Epoxy Substances 0.000 claims abstract description 6
- 125000003700 epoxy group Chemical group 0.000 claims abstract description 6
- 229910052751 metal Inorganic materials 0.000 claims description 8
- 239000002184 metal Substances 0.000 claims description 8
- 239000007767 bonding agent Substances 0.000 claims description 4
- 239000000758 substrate Substances 0.000 abstract description 6
- 239000004411 aluminium Substances 0.000 abstract description 5
- 229910052782 aluminium Inorganic materials 0.000 abstract description 5
- 238000010276 construction Methods 0.000 abstract description 5
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminum Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 abstract description 4
- 230000003287 optical Effects 0.000 description 4
- 230000004907 flux Effects 0.000 description 3
- 238000005286 illumination Methods 0.000 description 3
- 239000000463 material Substances 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 2
- 101700050571 SUOX Proteins 0.000 description 1
- 238000007743 anodising Methods 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000001808 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 230000002708 enhancing Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000017525 heat dissipation Effects 0.000 description 1
- 230000020169 heat generation Effects 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- OAICVXFJPJFONN-UHFFFAOYSA-N phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 1
- 229920001296 polysiloxane Polymers 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000003892 spreading Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Abstract
ABSTRACT A utility lamp (1) comprises a curved reflector (2) having a spherically curved surface. An array of LEDS (3) is arranged in an electrical circuit on a thin substrate mounted via thermally conductive epoxy on a therrnally—conductive base (4), which in turn forms an integral part of the reflector (2). The LEDs are mounted for efficient heat transfer by conduction to the reflector (2). The reflector (2) thus operates as both a light reflector and as a radiative heat sink. The heat radiating properties of the reflector are enhanced by integral fins (7) extending in the radial direction around the periphery of the reflector (2). The reflector (2) is of integral aluminium construction.
Description
INTRODUCTION
Field of the Invention
The invention relates to a utility lamp of the type for a wide range of uses such as
illuminating shop windows or general domestic use.
Prior Art Discussion
At present, most such lamps have as a light source a fluorescent tube or an
incandescent bulb. However, these suffer from having a relatively short life, some
hundreds of hours, and so frequent replacement is necessary. In addition, the
conversion efficiency from electrical power to light is not Very good, especially for
incandescent sources. It has been proposed in patent literature to use light emitting
diodes (LEDs) instead as the light source, since LEDs have lifetimes of more than
100,000 hours provided the operating temperature of the LEDs is kept within the
required limits, and have good operating efficiencies. US6367949 describes an
approach in which a heat sink housing is provided for the LEDS. US6499860
describes an approach in which a glass bulb is of conventional construction, however
a prism supporting triangular arrays of LEDs is mounted inside the bulb. EPI 353120
describes a vehicle lamp having LEDs mounted on a heat conductive post for emitting
light which is reflected from a reflector.
US635004l and US2003/0227774 both describe arrangements in which heat is
conducted from the LEDS through an LED support and to heat sink fins protruding
away on the side opposite the light-emitting side. US6799864 describes a lamp in
which LEDS are in thermal contact with a thermal spreader having fins extending in a
direction opposed to the light-transmitting direction.
US6504301 describes a lamp in which some problems associated with LED heat
generation and dissipation are addressed by providing a particular type of silicone gel
material which is light-transmissive, has good heat conduction and is soft so that it
does not damage bond wires.
It appears that these approaches all suffer from being complex and thus difficult to
produce in high volumes with low cost for the mass market.
The invention is directed towards providing an improved lamp using light emitting
diodes.
SUMMARY OF THE INVENTION
According to the invention, there is provided a utility lamp comprising a group of at
least one light emitting diode mounted within a reflector, wherein:
the reflector comprises a base and a wall having an internal light—retlecting
surface; and
the diode group is mounted on the reflector base so that:
some emitted light reflects from the internal surface of the reflector
wall, and
heat is conducted into the reflector, and the reflector radiates this heat
from its exposed surfaces.
In one embodiment, the reflector wall comprises thermal dissipation fins.
In one embodiment, the fins are on an external surface of the reflector wall.
In one embodiment, the diode group is mounted on a ther1nally—conductive circuit
board which is secured to the reflector base by a thermally-conductive bonding agent.
In one embodiment, the bonding agent is thermally-conductive epoxy.
In another embodiment, the reflector is of greater cross-sectional area at the base than
at the wall.
In one embodiment, the lamp further comprises a diode drive circuit mounted in a
housing on the reflector base on a side opposed to that of the diode group, the housing
being in thermal contact with the reflector.
In one embodiment, an electrical connector fixture is secured to the housing.
In one embodiment, the circuit board comprises a metal layer.
In one embodiment, the metal layer underlies a multi—layer circuit board structure.
In another embodiment, each diode is of the surface mount type, the anode and
cathode of which are soldered to metal tracks which have a thermal path to the
reflector.
In one embodiment, the reflector shape is spherical.
In one embodiment, the reflector shape is parabolic, or alternatively hyperbolidal, or
ellipsoidal.
In one embodiment, the lamp further comprises an optical element mounted over the
diode group.
In a further embodiment, the optical element comprises an internal reflector for
reflecting light from the diode group onto the heat—dissipating reflector.
In one cmbodiment, the internal reflector is of conical or frusto-conical shape.
In one embodiment, the internal reflector comprises a central aperture for narrow-
angle light and a lens aligned with the aperture for focusing said light.
DETAILED DESCRIPTION OF THE INVENTION
Brief Description of the Drawings
The invention will be more clearly understood from the following description of some
embodiments thereof, given by way of example only with reference to the
accompanying drawings in which:-
Fig. l is a diagrammatic cross-sectional sketch of a utility lamp of the
invention;
Figs. 2 to 4 are cross-sectional sketches of alternative utility lamps of the
invention; and
Fig. 5 is a more detailed diagram showing mounting of LEDS on a substrate in
thermal contact with the lamp’s reflector;
Fig. 6 is a plan view showing the arrangement of LEDs in another
embodiment;
Fig 7 is a diagrammatic cross-sectional view of a simple lamp, having only one
LED;
Fig 8 is a diagrammatic cross-sectional view of a further lamp; and
Fig. 9 is a diagrammatic cross-sectional view of a lamp of the invention having
a reflector with an elevated base for LED support.
Description of the Embodiments
Referring to Fig. 1 a utility lamp 1 comprises a curved reflector 2 having a spherically
curved surface. An array or group of LEDs 3 is arranged in an electrical circuit on a
thin substrate mounted via thermally conductive epoxy on a thermally-conductive
base 4, which in turn forms an integral part of the reflector 2. The light emitted from
the array is typically distributed into a beamwidth (full width, half max) of 120°. For
most practical applications this wide beamwidth makes it difficult to provide adequate
illumination on the target area because the intensity has dropped off so much at that
point. Therefore, in order to provide a narrower beamwidth of the light from the LEDS
some optical elements are provided for beam shaping, according to the application.
The reflector 2 is provided for this purpose.
An internal conical reflector 5 is mounted inside the reflector 2, with the apex of the
cone facing towards the LEDs 3. The internal reflector 5 is mounted on cantilever
supports, not shown, so as to provide negligible obscuration of the light emitted from
the lamp. The electronic drive circuit of the LEDS 3 is connected to a standard bayonet
fixture 6. The fixture may alternatively be of any of the standard fixture types such as
bayonet, two pin, or screw-in.
In use, light emitted by the LEDS 3 either directly exits the lamp, as shown by ray Ll ,
or reflects from the internal reflector 5 and then the main reflector 2 as shown by the
rays L2. Another possibility is shown by rays L3, which are redirected directly by the
reflector 2. Thus, the emission angle of the light is generally, with the exception of a
portion of the L1 rays, confined to the required beam angle either by the reflector 2
directly, or by the reflector 2 combined with the reflector 5. Also, there is excellent
uniformity in spatial spread of light in generally circular cross sections spreading from
the lamp 1 .
An important aspect is that the LEDs are mounted for efficient heat transfer by
conduction to the reflector 2. The reflector 2 thus operates as both a light reflector as
illustrated and described above and as a radiating heat sink. The heat radiating
properties of the reflector are enhanced by integral fins extending in the radial
direction around the periphery of the reflector 2. The reflector with the fins 7 is of
integral aluminium construction. The short thermally conductive path from the LEDS
to the reflector, combined with the thermally radiating properties of the reflector
enables the operating temperature of the LED junctions to be minimised. This leads to
excellent operating stability and long product life. Also, the LEDs may be densely
packed. This density provides an intensely concentrated illumination, and the optic
element 5 plays an important role in obscuring the illumination to avoid discomfort
for users which may arise when light is concentrated very much.
It will be noted that this dual purpose role of the reflector allows a much simpler
construction of lamp, for example, avoiding need for a heat sink protruding from
underneath the LEDS. The configuration of the lamp of the invention is also
particularly compact because of avoidance of need for a protruding heat sink.
Regarding the LEDs, an ideal LED source would be a point source in which the
required flux comes from a single source of negligible dimension. In practice, because
the amount of flux from a single LED is likely to be less than that required in most
lamp applications, a number of sources may be required. Thus, being able to pack
LED sources densely is an advantage. In one embodiment the packing density of the
die is 4/mmz. Alternatively, a single large area LED die, several square mm, may be
used as a source and driven with a large current.
The LEDs may be in any suitable arrangement, such as in a high flux package. The
main reflector may be of metal or any material with good thermal conductivity and
which can provide a good reflective surface. The fixture may be an electrical mount of
any suitable conventional type other than bayonet. The optic element 5 may
incorporate an anti-glare feature. Also, it may be more complex than the simple
conical shape illustrated. The LEDs may be of any suitable colour or mix of colours,
and a diffuser may be included. Phosphor may be included in the optic or directly over
the LEDS, so as to produce white light by using ultraviolet or blue LEDs.
The surface shape of the internal reflector may be ellipsoidal so as to have differing
beam properties in two orthogonal directions. The main reflector may not be spherical.
It may have a curved surface of revolution such an ellipsoid or paraboloid or
hyberboloid so as to enhance source-to-beam coupling and to achieve better control of
beamshape. Indeed the main reflector may have flat walls joined at corners to form the
desired shape to surround the LEDS. The reflector may have any numerically-
generated shape for optimised distribution of light.
The back surface of the reflector and of the radiating fins may be treated so as to
increase their thermal emissivity and improve their radiative performance, such as for
example by anodising them black. Also, the reflector may be in thermal contact with a
housing for the electronics, at a location such as directly below the reflector base
supporting the LEDS.
Fig. 2 illustrates in a lamp 15 rays 16 which reflect from the main reflector and rays
17 which directly exit. There is a similar thermal path to the reflector, although in this
embodiment there are no fins shown. Whether fins are needed for any particular lamp
depends upon the amount of electrical power being dissipated in the LEDs, and the
maximum recommended operating junction temperature for the particular LEDS being
used.
Referring to Fig. 3 a lamp 20 has a reflector 2] of spherical curvature and a lens 22
which converts the beams of light from the LEDS, which emit into a relatively large
angle of at least 1200 full width half max, to the required smaller beamwidth (such as
°) of the complete lamp. In this case the reflector 21 has fins 23, of generally
annular shape extending around the reflector 21. The function of the fins is to increase
the available surface area for radiatively cooling the heat sink. They can be arranged
radially with respect to the main axis of the reflector, or tangential to it, or some
random arrangement of fins might be chosen depending upon the most appropriate
type for the manufacturing processes being employed. In some cases, chemical
surface treatments may be used to provide an adequate increase in effective surface
area.
The lens may alternatively be plano-convex, or bi-convex, or any form of collimating
or condensing lens. The lens may be of one or multiple components.
Referring to Fig. 4 a lamp 30 has a spherical reflector 31, an internal reflector 32 with
a central aperture. and a lens 33 aligned with the central aperture. The optics focus a
central part of the source beam and wide—angle rays are re-focused by the main
reflector 31, intermediate angle rays being re-focused by the secondary mirror 32.
This solves the problem of it being difficult to achieve a single very fast lens which
catches all the LED rays which miss the main reflector.
Referring to Fig. 5 a lamp 50 comprises a main reflector 51 having a disc—shaped base
for supporting LEDs via their circuit board. The LEDs are of the surface—mount type.
having an anode and a cathode placed on tracks of a multi-layer circuit board. The
tracks and internal layers are shown as 53. These have a combined total depth of only
about 0.1mm. The LEDs each have a top light - emitting layer. The layers 53 are
bonded to an aluminium substrate 54 which forms part of the circuit board and allows
excellent thermal conduction. This has a depth of c. lmm. A heat path from the LEDs
to the main reflector 51 is completed by thermal epoxy 55 which bonds the aluminium
layer 55 to the reflector. The reflector material in the embodiment is spun—aluminium
A low profile drive circuit housing 56 is secured to the underneath of the reflector 5l,
and it contains in an unobtrusive manner drive electronics 57 connected to a bayonet
fitting 58 and by wiring 59 to contacts 60 on the board 53.
It will be appreciated that this arrangement provides for excellent heat transfer to the
reflector, and a low-profile compact lamp with little protruding on the side opposed to
the LEDs. A standard fitting is provided so that as far as the user is concerned it is a
standard utility lamp. The arrangement of the circuit board with deep A] base layer is
particularly effective for heat conduction to the reflector 51.
Referring to Fig. 6 the central region 70 of an alternative lamp is shown. Again. there
is a disc—shaped base 71 of the reflector which supports the LEDs. There are LEDs 72
arranged radially and electrically driven by wire bonds 73, which connect the
electrodes of the LEDs to the appropriate metal tracks on the thin circuit board layers
not shown) which lie beneath. Power is provided via contacts 74 which lead to the
main electrical connector (not shown).
Referring to Fig. 7 a lamp 80 has a reflector 81 and a single LED 82. The LED 82 is
provided with positive and negative electrical connections by having its connecting
leads 84 soldered to the connecting wires from the main connector fixture which lies
underneath (not shown.) Also, the body of the LED 82 is bonded to the reflector 81 by
thermally conductive epoxy 85. While the LED 82 is of high output power and
therefore high heat output, the thermal dissipation properties of the LED 82 and the
manner in which it is shown connected to a thermally conductive and radiative
reflector, allow it to be used in a confined space.
Referring to Fig. 8 a lamp 90 has a curved concave reflector 91 with fins 92 extending
from the base to the reflector edge. An array of LEDs 93 is placed on a thin, flexible
substrate 94 in good thermal Contact with the reflector 91. Electrical leads 95 extend
through a small aperture in the reflector 91. A conical optical element reflector 96 is
mounted on—axis above the LED array 93 and is supported by un—obtrusive arms 97.
The retlector may in one embodiment incorporate the substrate layers before forming.
This embodiment is particularly suitable for mass—production.
Referring to Fig. 9 a lamp 100 has a reflector 101 with radially-extending fins 102.
The reflector has an integral pyramid—shaped base 103 having four faces for
supporting LEDs 104. The latter are electrically driven via leads 106 extending
through a through-hole 105 and connected to a circuit, not shown.
The invention is not limited to the embodiments described but may be varied in
construction and detail.
Claims (1)
- Claims A utility lamp comprising a group of at least one light emitting diode mounted within a reflector, wherein: the reflector comprises a base and a wall having an internal light-reflecting surface; and the diode group is mounted on the reflector base so that: some emitted light reflects from the internal surface of the reflector wall, and heat is conducted into the reflector, and the reflector radiates this heat from its exposed surfaces. A lamp as claimed in claim 1, wherein the reflector wall comprises thermal dissipation fins; and wherein the fins are on an external surface of the reflector wall; and wherein the diode group is mounted on a therrnally—conductive circuit board whichis secured to the reflector base by a thermally-conductive bonding agent; and wherein the bonding agent is thermally-conductive epoxy; an dwherein the reflector is of greater cross-sectional area at the base than at the wall. A lamp as claimed in any preceding claim, further comprising a diode drive circuit mounted in a housing on the reflector base on a side opposed to that of the diode group, the housing being in thermal contact with the reflector; and wherein an electrical connector fixture is secured to the housing; and wherein the circuit board comprises a metal layer; and wherein the metal layer underlies a mu1ti—layer circuit board structure. A lamp as claimed in any preceding claim, wherein each diode is of the surface mount type, the anode and cathode of which are soldered to metal tracks which have a thermal path to the reflector. A utility lamp as claimed in claim 4, further comprising an internal reflector is of conical shape.
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
IEIRELAND17/02/20042004/0098 |
Publications (2)
Publication Number | Publication Date |
---|---|
IE20050086U1 IE20050086U1 (en) | 2005-09-21 |
IES84104Y1 true IES84104Y1 (en) | 2005-12-29 |
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