Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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LIGHT UNIT
FIELD OF THE INVENTION
[0001] The present invention pertains to the field of lighting and in
particular to a light
unit designed for ease of replacement within a lighting device.
BACKGROUND
[0002] Advances in the development and improvements of the luminous flux of
light-
emitting devices such as solid-state semiconductor and organic light-emitting
diodes
(LEDs) have made these devices suitable for use in general illumination
applications,
including architectural, entertainment, and roadway lighting. Light-emitting
diodes are
becoming increasingly competitive with light sources such as incandescent,
fluorescent
and high-intensity discharge lamps.
[0003] As is known, LEDs can vary in production. For example, raw light output
from
a group of LED chips grown on the same wafer manufactured by the same
equipment
may have as much as about a 3:1 variation in their luminous flux output over
the same
wafer. This fact gives rise to a binning strategy which is commonly used in
the industry,
whereby LEDs are individually tested and binned into categories of luminous
flux
output that represent about 30% intervals. Likewise, forward voltage, dominant
wavelength and beam spread may be other factors that are considered during the
binning
process.
[0004] Furthermore, chromaticity and luminous flux output of LEDs can depend
on
junction temperature, which can have undesirable effects on the correlated
colour
temperature (CCT) and more generally the chromaticity of the emitted light.
LED
junction temperature variations can also cause undesired effects in the
spectral power
distribution of the resultant output light. Variations in junction temperature
not only can
reduce the luminous flux output, but can also cause undesirable variations in
the CCT of
mixed light.
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[0005] Based on the inherent emission characteristics of LEDs, a control
system
associated with a LED based lighting device typically comprises calibration
data
regarding the LEDs within the lighting device. In this manner the control
system is
capable of adjusting the operation of the LEDs associated with the lighting
device based
on their respective predetermined emission characteristics.
[0006] Despite the known extended life expectancy of LEDs, it may be necessary
to
replace the LEDs in a lighting device. This required replacement may be a
result of, for
example, failure of an LED, failure of connecting circuitry on a printed
circuit board
(PCB) carrying the LEDs or other factors as would be readily understood. For
example,
in a lighting device containing a large number of LEDs, the likelihood of a
LED failure
increases, and it is typically desirable to replace the failed LED as quickly
as possible, in
order to correct the potentially resulting undesired changes to the
illumination pattern
generated by the lighting device. Given the variability in LED output
parameters, such
as intensity and dominant wavelength, between nominally identical LEDs from
the same
production batch for example, it is typically desirable to recalibrate a
lighting device
after every replacement of LEDs. In some lighting devices, particularly those
in which
the light output from differently coloured LEDs is mixed, the resulting light
pattern after
replacement of the LEDs can remain incorrect, unbalanced or undesired until
the
lighting device is recalibrated, which may entail waiting for a service
technician.
[0007] United States Patent No. 6,806,659 describes a lighting apparatus
comprising a
control module and a light module, wherein the light module is
interchangeable. The
control module comprises a switch, and microcontroller. Memory, which is
contained
within the microcontroller, is used for storing the level of intensity at
which the LED(s)
are driven. Therefore, upon replacement of a light module of this lighting
apparatus, the
control module would require recalibration to account for the emission
characteristics of
the LEDs associated with the new light module.
[0008] United States Patent No. 6,965,205 discloses a lighting system
containing a
system memory for controlling a processor, and discloses that the memory may
contain
calibration data associated with the control signals for driving the LEDs.
This memory,
however, is configured for use by the system as a whole, and therefore any
calibration
data relating to a specific LED must be input to the memory in an additional
step if a
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LED is replaced. Therefore this system requires recalibration after the
replacement of
one or more LEDs.
[0009] In addition, United States Patent Application Publication No. 2006/0002
1 1 0
describes lighting units which contain light sources such as LEDs. The
lighting units
described may also optionally include data storage facilities, which may be
used for
storing calibration information. The data storage facilities are configured to
be
accessible by the processors of the lighting units. This configuration of data
storage
facilities are provided for an entire light system, and therefore upon
replacement of one
or more light sources, new calibration data is to be input into the data
storage facilities
for use by the appropriate processor. Therefore this system also requires
recalibration
after the replacement of one or more light sources.
[0010] Also United States Patent Nos. 6,411,046 and 6,441,558 disclose
luminaires in
which information for the variation in colour coordinates as a function of
temperature
are stored in a memory coupled to the control unit. In this configuration of
the
luminaire, if one or more LEDs are replaced, the recalibration of the
luminaire is
required, wherein appropriate new calibration information is entered into the
memory
associated with the control unit.
[0011] Therefore there is a need for a new light unit which can enable ease of
replacement and interchangability of light-emitting elements of a lighting
device,
without a required recalibration of the lighting device.
[0012] This background information is provided to reveal information believed
by the
applicant to be of possible relevance to the present invention. No admission
is
necessarily intended, nor should be construed, that any of the preceding
information
constitutes prior art against the present invention.
SUMMARY OF THE INVENTION
[0013] An object of the present invention is to provide a light unit. In
accordance with
an aspect of the present invention, there is provided a light unit adapted for
connection
to a lighting device, the lighting device including a control system for
controlling
activation of one or more light-emitting elements, the control system adapted
for
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connection to a source of power, the light unit comprising: one or more
carriers; one or
more light-emitting elements operatively coupled to one or more of the
carriers, the one
or more light-emitting elements for generating electromagnetic radiation; a
memory
device operatively coupled to one or more of the carriers, the memory device
including
information representative of operational characteristics of the one or more
light-
emitting elements, the memory device adapted for connection to the control
system;
wherein the control system provides control signals to the one or more light-
emitting
elements and wherein said control signals are dependent on the operational
characteristics.
BRIEF DESCRIPTION OF THE FIGURES
[0014] Figure 1 illustrates a light unit according to one embodiment of the
present
invention, wherein the light unit is operatively coupled to a control system
of a lighting
device.
DETAILED DESCRIPTION OF THE INVENTION
Definitions
[0015] The term "light-emitting element" is used to define any device that
emits
radiation in any region or combination of regions of the electromagnetic
spectrum for
example, the visible region, infrared and/or ultraviolet region, when
activated by
applying a potential difference across it or passing a current through it, for
example.
Therefore a light-emitting element can have monochromatic, quasi-
monochromatic,
polychromatic or broadband spectral emission characteristics. Examples of
light-
emitting elements include semiconductor, organic, or polymer/polymeric light-
emitting
diodes, optically pumped phosphor coated light-emitting diodes, optically
pumped nano-
crystal light-emitting diodes or other similar devices as would be readily
understood by a
worker skilled in the art.
[0016] As used herein, the term "about" refers to a +/- 10% variation from the
nominal
value. It is to be understood that such a variation is always included in any
given value
provided herein, whether or not it is specifically referred to.
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[0017] Unless defined otherwise, all technical and scientific terms used
herein have the
same meaning as commonly understood by one of ordinary skill in the art to
which this
invention belongs.
[0018] The present invention provides a light unit that is interchangeable
within a
lighting device. The light unit comprises a carrier to which one or more light-
emitting
elements are connected. The light unit further comprises a memory device
operatively
coupled to the carrier, wherein the memory device includes information
representative
of the operational characteristics of the one or more light-emitting elements.
Upon the
operative coupling of the light unit with a lighting device, a control system
associated
with the lighting device can access the memory device to obtain operational
characteristics of the one or more light-emitting elements associated with the
carrier. In
this manner, the operational characteristics of the light-emitting elements
can be
immediately available to the control system, without the need for calibration
of the
lighting device subsequent to the replacement or changing of the light unit
with the
lighting device.
[0019] Figure 1 illustrates a light unit 5 according to one embodiment of the
present
invention, wherein the light unit 5 is operatively coupled to the control
system of a
lighting device. The memory device 10 and the one or more light-emitting
elements 20
are mounted on a single carrier 60. The memory device 10 is configured to
carry the
operational characteristics of the one or more light-emitting elements 20
mounted on the
carrier 60. The control system 40 of the lighting device to which the light
unit 5 is
operatively coupled, accesses the memory device in order to extract or write
30
information relating to the operational characteristics of the one or more
light-emitting
elements 20 or other information on the memory device. In this manner the
control
system 40 can provide control signals 50 to the one or more light-emitting
elements 20
in order that the one or more light emitting elements emit the desired
electromagnetic
radiation, for example the desired colour of light. The control system 40 is
adapted for
connection to a source of power thereby enabling desired activation of the one
or more
light-emitting elements 20.
[0020] In one embodiment of the present invention, other data relating to the
one or
more light-emitting elements and/or the light unit may be contained on the
memory
device. For example the memory device may comprise information relating to
date of
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manufacture, date of calibration, manufacturer's reference information, serial
numbers,
model numbers, bin information of the light-emitting elements and the like.
[0021] In one embodiment of the present invention, operational characteristics
can be
updated according to the number of hours of operation of the one or more light-
emitting
elements associated with the light unit. For example, a record of operational
history of
the one or more light-emitting elements can be useful for the investigation of
malfunctioning of the light-emitting elements or deterioration in operating
parameters
thereof which may provide a means for determining operating conditions under
which
the light-emitting elements may have the greatest lifetime.
Carrier
[0022] The carrier provides a support mechanism for the one or more light-
emitting
elements and/or the memory device.
[0023] In one embodiment, a single carrier provides a unitary support to both
the one or
more light-emitting elements and the memory device, which can provide a means
for
ease of changability of the light unit.
[0024] In an alternate embodiment of the present invention, a carrier is used
as a support
mechanism for the one or more light-emitting elements, and a second carrier is
used as
the support mechanism for the memory device.
[0025] In a further embodiment, a particular carrier is used as a support
mechanism for a
particular format of one or more light-emitting elements. For example, red
light-
emitting elements are operatively coupled to one carrier, green light-emitting
elements
are operatively coupled to a second carrier and blue light-emitting elements
are
operatively coupled to a third carrier.
[0026] In one embodiment of the present invention, when the light unit
comprises
multiple carriers, these multiple carriers can be structurally connected by
frame system,
in order to produce a unitary carrier component. The configuration of the
frame system
can be dependent on the configuration of the light unit, the lighting device
and the
number of carriers within the light unit.
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[0027] In one embodiment, the carrier is made from a standard printed circuit
board
(PCB) type material, for example, an FR4 compound material or other PCB format
as
would be readily understood by a worker skilled in the art.
[0028] In one embodiment the carrier is made of a thermally conductive
material, for
example, ceramic such as A1N, A1203, BeO, metal core printed circuit board
(MCPCB),
direct bond copper (DBC), CVD diamond or other suitable thermally conductive
material as would be known to a worker skilled in the art. Furthermore the
substrate can
be fabricated from a metal, for example Olin 194, Cu, CuW or any other
thermally
conductive alloy. The substrate may be coated with a dielectric for electrical
isolation of
one or more light-emitting elements, and/or electrical contacts. In one
embodiment,
electrical traces can be deposited onto a dielectric coated substrate to allow
electrical
connectivity.
[0029] In one embodiment, the carrier can be designed such that traces provide
electrical
connections from the one or more light-emitting elements and the memory device
to the
control system associated with the lighting device. In one embodiment the
traces are
formed on one side of the carrier. Alternately the carrier can have electrical
connections
or traces on both sides thereof. This configuration of the traces can be based
on the
design of the light-emitting element, the memory device and/or the lighting
device.
[0030] In one embodiment, the carrier can be designed to comprise multiple
electrically
conducting planes in order to reduce the size of the carrier and potentially
increase the
potential density of devices, for example light-emitting elements, thereon due
to the
reduction of circuit traces for example.
[0031] In another embodiment of the present invention, the carrier can
comprise one or
more connectors, plugs or interconnectors which provide for the operative
connection
between the light unit and the lighting device. A worker skilled in the art
would readily
understand configuration of plugs which would provide the desired operative
connection
between the carrier and the lighting device.
[0032] The one or more carriers are electrically configured to operatively
connect to the
control system of the lighting device which would be readily understood by a
worker
skilled in the art.
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[0033] The carrier can be formed into a variety of desired shapes, for example
flat,
curved, square, circular, elliptical or other desired shape or other desired
shape as would
be readily understood. The configuration and shape of the carrier can be
dependent on
the design of the lighting device, which can determine the shape and size
restrictions
that may be placed on the carrier.
Memory Device
[0034] The memory device is operatively coupled to a carrier and provides a
means for
the storing of operational characteristics of the one or more light-emitting
elements with
which it is associated. In this manner, upon the operational coupling of the
light unit to
the lighting device, the operational characteristics of each of the one or
more light-
emitting elements of the lighting unit, are accessible to the control system
of the lighting
device.
[0035] The operational characteristics of the one or more light-emitting
elements can be
representative of the wavelength and intensity emission spectrum of the one or
more
light-emitting elements.
[0036] In one embodiment, the operational characteristics are further
representative of
the temperature dependence of the wavelength and intensity emission spectrum
of the
one or more light-emitting elements. As would be known to a worker skilled in
the art,
different colours of light-emitting elements have varying temperature
dependencies and
therefore appropriate operational characteristics are required to represent
this varying
dependency.
100371 In one embodiment of the present invention, the operational
characteristics are
polynomial expressions or algorithms for the evaluation of the wavelength and
intensity
emission spectrum of the one or more light-emitting elements.
[0038] Ia one embodiment the operational characteristics represent the peak
wavelength
emission, peak intensity emission and spectral line width of the one or more
light-
emitting elements as a function of operational temperature of the one or more
light-
emitting elements. The representation of the spectral output for each of the
one or more
light-emitting elements can be represented by polynomial expression with
predetermined
parameters. For example, the operational characteristics stored in the memory
device
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can be linear or exponential temperature dependent expressions that represent
the
predetermined parameters of the suitable numerical approximation for the one
or more
light-emitting elements.
[0039] In an alternate embodiment, the operational characteristics are
configured in a
tabular format, for example in a look-up table configuration.
[0040] The control system can be a computing device or microcontroller having
a
central processing unit (CPU) and peripheral input/output devices (such as A/D
or D/A
converters) to monitor parameters from one or more peripheral devices that are
operatively coupled to the control system, for example a temperature
determination
mechanism. The controller can optionally include one or more storage media
collectively referred to herein as "memory". The memory can be volatile and
non-
volatile computer memory such as RAM, PROM, EPROM, and EEPROM, flash,
compact disks, optical disks, or the like, wherein control programs (such as
software,
microcode or firmware) for monitoring or controlling the one or more light-
emitting
elements and peripheral devices coupled to the control system are stored and
executed
by the CPU.
[0041] The memory device can be configured as electronically erasable
programmable
read only memory (EEPROM), electronically programmable read only memory
(EPROM), non-volatile random access memory (NVRAM), read-only memory (ROM),
programmable read-only memory (PROM), flash memory or other non-volatile
memory
for storing data as would be readily understood by a worker skilled in the
art.
[0042] In one embodiment, the memory device can be configured as a dip-switch
package for storing the operational characteristics. The dip-switch package
can be set
during the calibration stage of the light-emitting elements, for example
during the
manufacture of the light unit.
[0043] In one embodiment of the present invention, the memory device is
configured as
an addressable device. The address of the memory device can be stored in a dip-
switch
package, or can be stored within the memory device for example defined by
firmware
thereon. Other suitable methods for defining the address of a memory device
would be
readily understood by a worker skilled in the art.
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[0044] It is obvious that the foregoing embodiments of the invention are
exemplary and
can be varied in many ways. Such present or future variations are not to be
regarded as
a departure from the spirit and scope of the invention, and all such
modifications as
would be obvious to one skilled in the art are intended to be included within
the scope of
the following claims.
