U.S. patent application number 11/865114 was filed with the patent office on 2008-01-24 for independent control of light emitting diodes for backlighting of color displays.
This patent application is currently assigned to Cree, Inc.. Invention is credited to Gerald H. Negley.
Application Number | 20080018830 11/865114 |
Document ID | / |
Family ID | 37038100 |
Filed Date | 2008-01-24 |
United States Patent
Application |
20080018830 |
Kind Code |
A1 |
Negley; Gerald H. |
January 24, 2008 |
INDEPENDENT CONTROL OF LIGHT EMITTING DIODES FOR BACKLIGHTING OF
COLOR DISPLAYS
Abstract
Backlighting systems for color display screens include clusters
of LED devices of different colors that are configured to radiate
the different colors in a light path that impinges on the color
display screen, to provide backlighting on the color display
screen. LED device controllers are provided, a respective one of
which is configured to control operating parameters of a subset of
the clusters of LED devices, a single cluster of LED devices and/or
individual LED devices in the individual clusters. The LED device
controllers may use a common data line.
Inventors: |
Negley; Gerald H.;
(Hillsborough, NC) |
Correspondence
Address: |
MYERS BIGEL SIBLEY & SAJOVEC, P.A.
P.O. BOX 37428
RALEIGH
NC
27627
US
|
Assignee: |
Cree, Inc.
|
Family ID: |
37038100 |
Appl. No.: |
11/865114 |
Filed: |
October 1, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
11185397 |
Jul 20, 2005 |
|
|
|
11865114 |
Oct 1, 2007 |
|
|
|
Current U.S.
Class: |
349/69 ; 315/35;
362/231 |
Current CPC
Class: |
G09G 3/32 20130101; G09G
3/3426 20130101; G09G 2320/0233 20130101; G02F 1/133603
20130101 |
Class at
Publication: |
349/069 ;
315/035; 362/231 |
International
Class: |
G02F 1/13357 20060101
G02F001/13357; H01J 7/44 20060101 H01J007/44; H05B 33/22 20060101
H05B033/22 |
Claims
1. A backlight system for a flat panel color display screen that
includes an array of optical shutter color picture elements, the
backlight system comprising: a plurality of clusters of Light
Emitting Diode (LED) devices of different colors that are
configured to radiate light of the different colors in a light path
that impinges on the flat panel color display screen to provide
backlighting of the array of optical shutter color picture elements
on the flat panel color display screen; and a plurality of LED
device controllers, a respective one of which is configured to
control operating parameters of a subset of the clusters of LED
devices to provide uniform backlighting of the array of optical
shutter color picture elements that appears as white light, by
compensating for electrical/optical parameter differences among the
LED devices, wherein a respective LED device controller is
configured to control the operating parameters of a respective
single cluster of LED devices; and wherein a respective cluster of
LED devices comprises a red, a blue and a green LED device, wherein
the plurality of LED device controllers comprise a plurality of LED
device controller integrated circuits, a respective one of which
includes a reflective cavity therein and wherein a respective
cluster comprising a red, a blue and a green LED device is mounted
in the respective reflective cavity in a respective LED device
controller integrated circuit.
2. A backlight system according to claim 1 further comprising a
mounting substrate, wherein the plurality of LED device controller
integrated circuits are mounted on the mounting substrate.
3. A backlight system according to claim 1 wherein at least some of
the LED controller integrated circuits are electrically connected
to a common data line.
4. A backlight system according to claim 1 in combination with the
flat panel color display screen that includes the array of optical
shutter color picture elements.
5. A backlight system according to claim 4 wherein the array of
optical shutter color picture elements comprises an array of color
Liquid Crystal Display (LCD) picture elements.
6. A backlight system for a flat panel color display screen that
includes an array of optical shutter color picture elements, the
backlight system comprising: a plurality of clusters of Light
Emitting Diode (LED) devices of different colors that are
configured to radiate light of the different colors in a light path
that impinges on the flat panel color display screen to provide
backlighting of the array of optical shutter color picture elements
on the flat panel color display screen; and a plurality of LED
device controllers, a respective one of which is configured to
control operating parameters of a subset of the clusters of LED
devices to provide uniform backlighting of the array of optical
shutter color picture elements that appears as white light, by
compensating for electrical/optical parameter differences among the
LED devices, wherein a respective LED device controller is
configured to control the operating parameters of a respective
single cluster of LED devices; and wherein a respective cluster of
LED devices comprises a red, a blue and a green LED device, wherein
the plurality of LED device controllers comprise a plurality of LED
device controller integrated circuits, wherein a respective cluster
comprising a red, a blue and a green LED device and a respective
LED device controller integrated circuit are mounted on a common
substrate, wherein the common substrate comprises a reflector
cavity and wherein the cluster of LED devices is mounted in the
reflector cavity.
7. A backlight system according to claim 6 further comprising a
mounting substrate, wherein a plurality of the common substrates
are mounted on the mounting substrate.
8. A backlight system according to claim 6 wherein at least some of
the LED controller integrated circuits are electrically connected
to a common data line.
9. A backlight system according to claim 6 in combination with the
flat panel color display screen that includes the array of optical
shutter color picture elements.
10. A backlight system according to claim 9 wherein the array of
optical shutter color picture elements comprises an array of color
Liquid Crystal Display (LCD) picture elements.
11. A backlight system for a color display screen that includes an
array of color picture elements, the backlight system comprising: a
plurality of clusters of Light Emitting Diode (LED) devices of
different colors that are configured to radiate light of the
different colors in a light path that impinges on the color display
screen to provide backlighting on the color display screen; and a
plurality of LED device controller integrated circuits, a
respective one of which is configured to control operating
parameters of a subset of the clusters of LED devices; wherein a
respective LED device controller integrated circuit includes a
reflective cavity therein and wherein a respective subset of the
clusters of LED devices is mounted in the respective reflective
cavity.
12. A backlight system according to claim 11 wherein a respective
LED device controller integrated circuit is configured to control
the operating parameters of a respective single cluster of LED
devices.
13. A backlight system according to claim 12 wherein a respective
LED device controller integrated circuit is configured to control
the operating parameters of individual LED devices of different
colors in a respective single cluster of LED devices.
14. A backlight system according to claim 12 wherein a respective
cluster of LED devices comprises a red, a blue and a green LED
device.
15. A backlight system according to claim 14 further comprising a
mounting substrate, wherein the plurality of LED device controller
integrated circuits are mounted on the mounting substrate.
16. A backlight system according to claim 14 wherein at least some
of the LED controller integrated circuits are electrically
connected to a common data line.
17. A backlight system according to claim 11 wherein the plurality
of LED device controller integrated circuits are configured to
control operating parameters of the clusters of LED devices to
provide uniform backlighting by compensating for electrical/optical
parameter differences among the LED devices.
18. A backlight system according to claim 11 wherein the plurality
of LED device controller integrated circuits are configured to
control operating parameters of the clusters of LED devices to
provide a desired color point of the backlighting by compensating
for electrical/optical parameter differences among the LED
devices.
19. A backlight system according to claim 11 in combination with
the color display screen that includes the array of color picture
elements.
20. A backlight system according to claim 19 wherein the array of
color picture elements comprises an array of color Liquid Crystal
Display (LCD) picture elements.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a divisional of U.S. application Ser.
No. 11/185,397, filed Jul. 20, 2005, entitled Independent Control
Of Light Emitting Diodes For Backlighting Of Color Displays,
assigned to the assignee of the present application, the disclosure
of which is hereby incorporated herein by reference in its entirety
as if set forth fully herein.
FIELD OF THE INVENTION
[0002] This invention relates to displays such as Liquid Crystal
Displays (LCDs), and more particularly, to backlighting of displays
such as LCDs.
BACKGROUND OF THE INVENTION
[0003] Display screens are widely used for computer monitors,
televisions and many other consumer and commercial display
applications. Some flat panel display screens include an array of
optical shutters and a backlight system that impinges light on the
display screen.
[0004] For example, LCD devices are widely used in flat panel
displays for monitors, televisions and other consumer and
commercial display applications. As is well known to those having
skill in the art, an LCD display generally includes an array of LCD
devices that act as an array of optical shutters. Transmissive LCD
displays employ backlighting using, for example, fluorescent cold
cathode tubes above, beside and sometimes behind the array of LCD
devices. A diffusion panel behind the LCD devices can be used to
redirect and scatter the light evenly to provide a more uniform
display.
[0005] Conventional shuttered display devices generally include
three different color picture elements (often referred to as pixels
and/or subpixels), generally red (R), green (G) and blue (B)
picture elements. A backlight system for shuttered display devices
may be configured to uniformly radiate light on the display screen
that provides the appearance of white light. As used herein,
"different colors" means different frequency spectra having
different center frequencies.
[0006] It is also known to provide an array of fluorescent cold
cathode tubes behind and facing the planar array of LCD devices.
Unfortunately, an array of fluorescent cold cathode tubes may
increase the thickness of the LCD display and/or increase the power
consumption thereof. It also may be difficult to uniformly
illuminate the planar array of LCD devices with the array of
fluorescent cold cathode tubes.
[0007] Semiconductor light emitting devices, such as Light Emitting
Diode (LED) devices, also may be used for edge illumination of a
planar array of LCD devices. For example, U.S. patent application
Ser. No. 10/898,608, filed Jul. 23, 2004, entitled Reflective
Optical Elements for Semiconductor Light Emitting Devices, to the
present inventor Negley, and assigned to the assignee of the
present invention, the disclosure of which is hereby incorporated
herein by reference in its entirety as if set forth fully herein,
describes side emission LEDs that may be used for large area LCD
and/or television backlighting.
[0008] LED devices also may be used for direct backlighting of LCD
displays. For example, U.S. patent application Ser. No. 11/022,332,
filed Dec. 23, 2004, entitled Light Emitting Diode Arrays For
Direct Backlighting Of Liquid Crystal Displays, to the present
inventor Negley, and assigned to the assignee of the present
invention, the disclosure of which is hereby incorporated herein by
reference in its entirety as if set forth fully herein, describes a
display panel for a flat panel display that includes a planar array
of LCD devices and a planar array of LED devices that is closely
spaced apart from the planar array of LCD devices, to provide
backlighting for the planar array of LCD devices.
[0009] As is well known to those having skill in the art, the
electrical and/or optical parameters of individual LED devices that
are fabricated may vary considerably, for example, due to routine
process variations. In order to provide backlighting uniformity
and/or to provide a desired backlighting color point, it may be
desirable to sort or "bin" LED devices that are to be used for
backlighting applications, to allow close matching of electrical
and/or optical parameters of the LED devices. Unfortunately, this
binning may produce additional manufacturing complexity and/or may
lead to at least some of the LED devices being rejected as being
unsuitable. Binning and/or rejection of some LED devices also may
increase the resultant cost of LED backlighting systems.
SUMMARY OF THE INVENTION
[0010] Exemplary embodiments of the invention provide edge and/or
direct backlighting systems for color display screens that include
an array of color picture elements. These backlighting systems
include a plurality of clusters of LED devices of different colors
that are configured to radiate light of the different colors in a
light path that impinges on the color display screen, to provide
backlighting on the color display screen. An LED device controller
also is provided that is configured to independently control
operating parameters of subsets of the clusters of LED devices. In
some embodiments, the LED device controller is configured to
independently control the operating parameters of individual
clusters of LED devices. In other embodiments, the LED device
controller is configured to independently control the operating
parameters of individual LED devices in individual clusters of LED
devices. In yet other embodiments, the LED device controller is
configured to use a common data line. In some embodiments, the
operating parameters of the subsets, clusters and/or individual LED
devices may be controlled to provide uniform backlighting, by
compensating for electrical/optical parameter differences among the
LED devices and/or to provide a desired color point of the
backlighting, by compensating for electrical/optical parameter
differences among the LED devices.
[0011] In other embodiments of the present invention, a plurality
of LED device controllers is provided, a respective one of which is
configured to control operating parameters of a subset of the
clusters of LED devices. In other embodiments, a respective LED
device controller is configured to control the operating parameters
of a single cluster of LED devices, and, in some embodiments, to
control the operating parameters of the individual LED devices in
the cluster. A common data line also may be used in some
embodiments.
[0012] Various packaging techniques for edge and/or direct
backlight LED devices and LED device controllers may be provided
according to various embodiments of the present invention. For
example, in some embodiments, a respective cluster of LED devices
comprises a red, a blue and a green LED device, and the plurality
of LED device controllers comprise a plurality of LED device
controller integrated circuits. In some embodiments, a respective
cluster comprising a red, a blue and a green LED device is mounted
on a respective LED device controller integrated circuit. Multiple
LED device controller integrated circuits may be mounted on a
mounting substrate. In some embodiments, a reflector also may be
provided between a respective cluster of red, blue and green LED
devices, and a respective LED device controller integrated
circuit.
[0013] In still other embodiments, a respective cluster comprising
a red, blue and green LED device and a respective LED device
controller integrated circuit are mounted on a common substrate.
The common substrate may include a reflector adjacent the cluster
of LED devices. The common substrates may be mounted on a mounting
substrate.
[0014] In any of the above-described embodiments, at least some of
the LED controller integrated circuits may be electrically
connected to a common data line. The plurality of LED device
controllers may be configured to control operating parameters of
the LED devices, and thereby provide uniform backlighting and/or a
desired color point of the backlighting, by compensating for
electrical/optical parameter differences among the LED devices.
[0015] It will be understood that embodiments of the invention have
been described above in connection with edge and/or direct
backlight systems for color display screens. However, other
embodiments of the present invention can provide backlighting
methods for color display screens, wherein operating parameters of
subsets of the clusters of LED devices are independently controlled
during operation thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIGS. 1-4 are cross-sectional views of color display screens
including backlighting systems/methods according to exemplary
embodiments of the present invention.
[0017] FIGS. 5-7 are perspective views of backlighting
systems/methods according to exemplary embodiments of the present
invention.
DETAILED DESCRIPTION
[0018] The present invention now will be described more fully
hereinafter with reference to the accompanying drawings, in which
embodiments of the invention are shown. However, this invention
should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art. In the
drawings, the thickness of layers and regions are exaggerated for
clarity. Like numbers refer to like elements throughout. As used
herein the term "and/or" includes any and all combinations of one
or more of the associated listed items and may be abbreviated as
"/".
[0019] The terminology used herein is for the purpose of describing
particular embodiments only and is not intended to be limiting of
the invention. As used herein, the singular forms "a", "an" and
"the" are intended to include the plural forms as well, unless the
context clearly indicates otherwise. It will be further understood
that the terms "comprises" and/or "comprising," when used in this
specification, specify the presence of stated features, regions,
steps, operations, elements, and/or components, but do not preclude
the presence or addition of one or more other features, regions,
steps, operations, elements, components, and/or groups thereof.
[0020] It will be understood that when an element, such as a layer
or region, is referred to as being "on" or extending "onto" another
element, it can be directly on or extend directly onto the other
element or intervening elements may also be present. In contrast,
when an element is referred to as being "directly on" or extending
"directly onto" another element, there are no intervening elements
present. It will also be understood that when an element is
referred to as being "connected" or "coupled" to another element,
it can be directly connected or coupled to the other element or
intervening elements may be present. In contrast, when an element
is referred to as being "directly connected" or "directly coupled"
to another element, there are no intervening elements present.
[0021] It will be understood that, although the terms first,
second, etc. may be used herein to describe various elements,
components, regions, layers and/or sections, these elements,
materials, regions, layers and/or sections should not be limited by
these terms. These terms are only used to distinguish one element,
material, region, layer or section from another element, material,
region, layer or section. Thus, a first element, material, region,
layer or section discussed below could be termed a second element,
material, region, layer or section without departing from the
teachings of the present invention.
[0022] Furthermore, relative terms, such as "lower", "base", or
"horizontal". and "upper", "top", or "vertical" may be used herein
to describe one element's relationship to another element as
illustrated in the Figures. It will be understood that relative
terms are intended to encompass different orientations of the
device in addition to the orientation depicted in the Figures. For
example, if the device in the Figures is turned over, elements
described as being on the "lower" side of other elements would then
be oriented on "upper" sides of the other elements. The exemplary
term "lower", can therefore, encompasses both an orientation of
"lower" and "upper," depending on the particular orientation of the
figure. Similarly, if the device in one of the figures is turned
over, elements described as "below" or "beneath" other elements
would then be oriented "above" the other elements. The exemplary
terms "below" or "beneath" can, therefore, encompass both an
orientation of above and below. Moreover, the terms "front" and
"back" are used herein to describe opposing outward faces of a flat
panel display. Conventionally, the viewing face is deemed the
front, but the viewing face may also be deemed the back, depending
on orientation.
[0023] Embodiments of the present invention are described herein
with reference to cross section illustrations that are schematic
illustrations of idealized embodiments of the present invention. As
such, variations from the shapes of the illustrations as a result,
for example, of manufacturing techniques and/or tolerances, are to
be expected. Thus, embodiments of the present invention should not
be construed as limited to the particular shapes of regions
illustrated herein but are to include deviations in shapes that
result, for example, from manufacturing. For example, a region
illustrated or described as flat may, typically, have rough and/or
nonlinear features. Moreover, sharp angles that are illustrated,
typically, may be rounded. Thus, the regions illustrated in the
figures are schematic in nature and their shapes are not intended
to illustrate the precise shape of a region and are not intended to
limit the scope of the present invention.
[0024] Unless otherwise defined, all terms (including 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. It will be further understood that terms, such
as those defined in commonly used dictionaries, should be
interpreted as having a meaning that is consistent with their
meaning in the context of the relevant art and the present
disclosure, and will not be interpreted in an idealized or overly
formal sense unless expressly so defined herein.
[0025] FIG. 1 is a cross-sectional view of a color display screen
including a backlighting system/method according to exemplary
embodiments of the present invention. As shown in FIG. 1, these
color display screens 100 include an array of color picture
elements 110, such as a three-dimensional array of color LCD
devices. As is well known to those having skill in the art, the
array of color picture elements 110 may include a liquid crystal
substance between pieces of glass or other material, and may also
include polarizing films and one or more electrode layers. The
design of an array of color LCD picture elements is well known to
those having skill in the art, and need not be described further
herein.
[0026] Still referring to FIG. 1, a backlighting system 120
includes a plurality of clusters 130 of LED devices of different
colors that are configured to radiate light of the different colors
in a light path 140 that impinges on the color display screen 110,
to provide backlighting on the color display screen 110. It will be
understood that a cluster of LED devices of different colors
includes at least two LEDs of different colors, but may also
include more than one LED of a given color. An LED device
controller 150 is configured to independently control operating
parameters of subsets of the clusters 130 of LED devices. In some
embodiments, the LED device controller 150 may be configured to
independently control parameters of subsets of two or more of the
clusters of LED devices. Moreover, in some embodiments, as
illustrated in FIG. 1, the LED device controller is configured to
individually control the operating parameters of individual
clusters 130 of LED devices, as shown schematically by the
individual connections 152 between the controller 150 and the
individual clusters 130 of LED devices. In other embodiments,
individual clusters 130 of LED devices may be controlled without
the need for individual connections 152 between the controller 150
and the individual clusters 130, as will be described in detail
below.
[0027] In some embodiments, the LED device controller 150 is
configured to control operating parameters of the clusters 130 of
LED devices, to provide uniform backlighting, by compensating for
electrical and/or optical parameter differences among the LED
devices. As used herein, "uniform" backlighting means that an
ordinary viewer, who views the display at a conventional viewing
distance, is not aware of variation in backlighting intensity. In
some embodiments, variations of less than about 25% may provide
uniform intensity. whereas, in other embodiments. variations of
less than 5% may provide uniform intensity. In still other
embodiments of the invention, the LED device controller 150 is
configured to control operating parameters of the clusters 130 of
LED devices, to provide a desired color point in the backlighting,
by compensating for electrical/optical parameter differences among
the LED devices. As is well known to those having skill in the art,
a color point may refer to a point on a color spectral chart, for
example represented by a set of x and y coordinates in a CIE1931
spectral chart. Operating parameters of the clusters 130 of LED
devices may also be controlled to achieve other potentially desired
results, such as a time and/or space varying color point.
[0028] Accordingly, exemplary embodiments of the invention can
provide uniform backlighting and/or a desired color point of the
backlighting, notwithstanding that the individual clusters of LED
devices may have a wide variation in electrical and/or optical
parameters, such as forward voltage and/or optical efficiency. The
sorting or binning of large numbers of LED devices for uniformity
of optical and/or electrical parameters may not need to be
performed and/or relaxed binning standards may be used, because the
operating parameters of the LED devices in a given backlight system
may be controlled in subsets and/or individually, according to
embodiments of the present invention.
[0029] FIG. 2 is a cross-sectional view of color display screens
200 including backlighting systems/methods 220, according to other
exemplary embodiments of the present invention. In these
embodiments, the LED devices in a cluster 130 comprise a red, a
green and a blue LED device R, G, B, respectively. An LED device
controller 250 is configured to independently control the operating
parameters of individual LED devices R, G, B, in individual
clusters 130, as indicated by the control lines 252. In some
embodiments, two green LED devices are used. The two green LED
devices may emit green light of the same or different
frequencies.
[0030] It will be understood by those having skill in the art that
embodiments of FIGS. 1 and 2 may use a relatively large number of
control lines 152 and/or 252 between the LED clusters 130 and the
respective controller 150, 250. In contrast, embodiments of FIGS. 3
and 4, which will now be described, can use common data lines to
allow the number of control lines that are used to be reduced.
[0031] More specifically, FIG. 3 is a cross-sectional view of a
color display screen 300 according to other embodiments of the
invention, wherein a backlighting system/method 330 includes a
plurality of LED device controllers 350, a respective one of which
is configured to control operating parameters of a subset of the
clusters 130 of LED devices. In some embodiments, a respective LED
device controller 350 may be configured to control operating
parameters of two or more clusters 130 of LED devices. In other
embodiments, as shown in FIG. 3, a respective LED device controller
350 may be configured to control the operating parameters of a
single cluster 130 of LED devices.
[0032] Moreover, as shown in FIG. 3, the plurality of LED device
controllers 350 may be embodied as a plurality of LED device
controller integrated circuits that may be electrically connected
to one another by a common data line 354. In FIG. 3, a serial
connection is illustrated. However, parallel or combined
parallel-serial connections to the common data line also may be
provided. According to some embodiments of the present invention,
the individual LED device controllers 350 may be addressed using
well known addressing techniques, via the common data line 354.
Common power supply/ground lines and/or other lines also may be
provided. Accordingly, the number of external connections 356 that
are used for external connection to an LED backlighting external
device can be reduced or minimized.
[0033] FIG. 4 illustrates a color display screen 400 including
backlighting systems/methods 420 according to still other
embodiments of the present invention, wherein a given LED device
controller 450 is configured to independently control operating
parameters of individual ones of the red, green and blue LEDs R, G,
B, respectively, in a given cluster 130. As also shown in FIG. 4,
this independent control may be provided using a common data line
454. In FIG. 4, the individual LED device controllers 450 are
connected to the common control line 454 in parallel. However,
series and/or series-parallel connections also may be provided. The
common data line 454 can reduce the number of external connections
for the backlight system 420. It will be understood that other
common connection lines, such as power supply, ground and/or other
common connection lines, also may be provided.
[0034] It also will be understood by those having skill in the art
that embodiments of FIGS. 1-4 may be combined in various
combinations and subcombinations.
[0035] FIGS. 1-4 provided schematic cross-sectional views of
embodiments of the present invention. FIGS. 5-7 are perspective
views of packaging techniques for embodiments of FIGS. 1-4,
according to exemplary embodiments of the present invention.
[0036] In particular, as shown in FIG. 5, a respective cluster 130
of LED devices comprising a red, a green and a blue LED device R,
G, B, is mounted on a respective LED device controller integrated
circuit 450. Amounting substrate 510 also is provided, in some
embodiments, and the plurality of LED device controller integrated
circuits 450 are mounted on the mounting substrate 510. As shown in
FIG. 5, wire bonds 520 may be used to electrically connect the
individual LED devices in a cluster 130 to the LED device
controller integrated circuits 450. However, other conventional
electrical connection techniques, such as solder bumps, may be
used. Moreover, solder bumps 530 may be used to connect a LED
device controller integrated circuit 450 to a mounting substrate
510. However, other conventional electrical connection techniques,
such as wire bonding, also may be used. The common data line 454 of
FIG. 4 is illustrated by "D". Common power supply connections are
indicated by "+" and "-" designations. It will be understood that,
although embodiments of FIG. 5 may correspond to FIG. 4, analogous
embodiments for FIGS. 1-3 also may be provided.
[0037] It also will be understood that multiple LED devices of a
given color may be used in a cluster. Thus, for example, as shown
in FIG. 5, two green LED devices may be used in a cluster 130 of
FIG. 5, to compensate for the relatively lower output of green LED
devices compared to red or blue LED devices.
[0038] FIG. 6 illustrates other embodiments of the present
invention, wherein a reflector 610 is provided adjacent the cluster
130. As shown in FIG. 6, a reflector 610 may be provided between a
respective cluster 130 that comprises a red, a blue and a green LED
device, and a respective LED device controller integrated circuit
450. The reflector may be embodied by a reflective cavity
integrated in a substrate, as described in application Ser. No.
10/659,108, filed Sep. 9, 2003, entitled Solid Metal Block Mounting
Substrates for Semiconductor Light Emitting Devices; application
Ser. No. 11/011,748, filed Dec. 14, 2004, entitled Semiconductor
Light Emitting Device Mounting Substrates And Packages Including
Cavities And Cover Plates, And Methods Of Packaging Same;
application Ser. No. 11/022,332, Filed Dec. 23, 2004, entitled
Light Emitting Diode Arrays For Direct Backlighting Of Liquid
Crystal Displays; and/or application Ser. No. 10/972,910, filed
Oct. 25, 2004, Solid Metal Block Semiconductor Light Emitting
Device Mounting Substrates And Packages Including Cavities And Heat
Sinks, And Methods Of Packaging Same, all of which are assigned to
the assignee of the present invention, the disclosures of all of
which are hereby incorporated herein by reference in their entirety
as if set forth fully herein. In other embodiments, a freestanding
reflector may be provided between the LED devices 130 and the
controller integrated circuit 450. Many other configurations of
freestanding and/or integrated reflectors may be provided.
[0039] FIG. 7 illustrates other packaging techniques according to
exemplary embodiments of the present invention, wherein an LED
device controller 450 is mounted on a common substrate 710 along
with the red, green and blue LEDs in a cluster. The common
substrate 710 may itself be mounted on a mounting substrate 510. In
still other embodiments, the common substrate 710 may not be
needed, and the individual LED device controllers 450 and the
associated LED devices may be directly mounted on a mounting
substrate 510. Finally, in still other embodiments, the controller
450 and the associated LED devices may be mounted in a reflector,
as was shown at 610 in FIG. 6. A common substrate 710 may or may
not be used.
[0040] It will be understood that the packaging schemes of FIGS.
5-7 may be combined in various combinations and subcombinations.
Moreover, although connections of the controller integrated circuit
450 and of the common substrate 710 are shown on both sides
thereof, other embodiments may provide connections, such as wire
bonds, on a single side thereof.
[0041] Some embodiments of the present invention have been
described above in connection with a plurality of LED device
controllers 450 that may be electrically connected to a common data
line. The design of such LED controllers are well known to those
having skill in the art. For example, LED controllers 450 may be
embodied as Chromasic.TM. 1 microchips, marketed by Color Kinetics
Incorporated. As described in the Color Kinetics website,
"Chromasic.TM. 1 is a custom-designed microchip that integrates
power, communications, and control, to enable next-generation
digital lighting systems and networks. Chromasic combines digital
LED control and communication technology in a tiny package,
enabling highly controllable lamp nodes to generate 64 billion
color combinations. The fully-integrated, three channel, 12-bit LED
driver encompasses all components necessary to receive a serial
command bitstream, decode and extract PWM values, and re-create a
new serial bitstream. Also included are a high accuracy bandgap
reference, external programming circuit, and all necessary
circuitry to drive three independent LED channels. All that is
required to create a controlled RGB light node are: LEDs, a single
resistor for current programming, and a single bypass capacitor.
Chromasic 1 is available in 8-pin SC8 package. Inherent in the
design is the self-addressing of Chromasic. This means that each
Chromasic-based light element, whether it is a fixture or a single
pixel address itself based solely on its location within the
network. This provides an easy, scalable solution for large scale
lighting applications as well as video and electronic displays."
See colorkinetics.com/products/owm/chips/chromasic/.
[0042] It will also be understood that other conventional color
controllers may be used in other embodiments of the invention. Such
color controllers are widely used in many other applications. Such
color controllers may use the well known DMX lighting protocol. The
DMX protocol, which can include the DMX512 protocol, was developed
by the Engineering Commission of USITT in 1986, with subsequent
revisions in 1990 and 2004. The 2004 standard is also known as
DMX512-A. Multiple light fixtures may be controlled under the DMX
standard using a common 3-pin cable.
[0043] In some embodiments, a 24'' diagonal LCD display may employ
a 24'' diagonal backlighting system that includes 280 clusters of
RGGB LED devices in an array of 14 rows and 20 columns of clusters.
In some embodiments, each of the 1120 LED devices (4 LED devices in
each of 280 clusters) may use a minimum of 1120 external
connections in order to allow individual addressing. In contrast,
other embodiments of the present invention can allow as few as
three external connections for common power, ground and data, to
individually control the 1120 LED devices. A single common set of
power, ground and data connections may be provided to subsets of
the 280 clusters, such as to an individual row of LED clusters,
which may be addressed by a common data connection. It will also be
understood that embodiments of the invention have been described
herein in connection with array backlighting. However, edge
backlighting of an LCD display can also be provided according to
other embodiments of the present invention.
[0044] As was described above, conventional LED backlighting
systems and methods may place LED devices in series and/or parallel
strings. It may be desirable for the LEDs in a series string to be
run at the same current, and it may be desirable for the parallel
strings to be voltage matched. Current or voltage matching may
place strict requirements on binning of the forward voltages and/or
other parameters of the LED devices. In sharp contrast, some
embodiments of the present invention allow an Application-Specific
Integrated Circuit (ASIC) to be used to individually address each
LED in an LED backlight array. This can allow color balancing of
each pixel by driving each LED at a desired current to achieve a
desired "white point".
[0045] Moreover, by incorporating DMX and/or other processing, only
three external connections may be needed from board to board, which
can thereby reduce or minimize the number of external
interconnects. As was also described above, the LED clusters, such
as an RGB or an RGGB cluster, can be mounted on top of the ASIC
itself, with optical features such as reflectors included to
provide light extraction and/or to improve performance. Only three
signals may need to exist: positive, negative and data signals,
according to some embodiments of the present invention. Each
integrated circuit controller location may be known, and can be
individually addressed with respect to drive current. Hence, each
integrated circuit can be independently operated and each LED in
each cluster can be individually controlled, in some
embodiments.
[0046] Finally, it will be understood that embodiments of the
invention have been described primarily with respect to LCD
displays. However, other shuttered color displays, such as Digital
Light Projector (DLP) displays, may be used in other embodiments of
the present invention. Accordingly, a desired color (defined, for
example, in x, y coordinates from the 1931 CIE diagram and/or by
u', v' coordinates from the 1976 UCS CIE diagram), a desired color
intensity and/or a desired uniformity may be obtained by
individually controlling each pixel, while allowing wider
wavelengths or color bins of the individual R, G and B dice to be
used.
[0047] In the drawings and specification, there have been disclosed
embodiments of the invention and, although specific terms are
employed, they are used in a generic and descriptive sense only and
not for purposes of limitation, the scope of the invention being
set forth in the following claims.
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