U.S. patent application number 13/368138 was filed with the patent office on 2012-11-22 for pixel, display device including the pixel, and driving method of the display device.
Invention is credited to Sang-Myeon Han.
Application Number | 20120293479 13/368138 |
Document ID | / |
Family ID | 47174590 |
Filed Date | 2012-11-22 |
United States Patent
Application |
20120293479 |
Kind Code |
A1 |
Han; Sang-Myeon |
November 22, 2012 |
Pixel, Display Device Including The Pixel, And Driving Method Of
The Display Device
Abstract
A display device that includes a pixel including an organic
light emitting diode (OLED), a driving transistor connected to the
driving voltage and supplying a driving current to the OLED, a
compensation capacitor connected to the gate electrode of the
driving transistor, and a first storage capacitor and a second
storage capacitor electrically connected to or blocked from the
compensation capacitor, and a driving method thereof.
Inventors: |
Han; Sang-Myeon;
(Yongin-city, KR) |
Family ID: |
47174590 |
Appl. No.: |
13/368138 |
Filed: |
February 7, 2012 |
Current U.S.
Class: |
345/212 ;
345/204 |
Current CPC
Class: |
G09G 2300/0842 20130101;
G09G 2300/0861 20130101; G09G 3/3266 20130101; G09G 3/003 20130101;
G09G 2300/0819 20130101; H04N 13/341 20180501; G09G 3/3208
20130101; G09G 2300/0852 20130101; G09G 3/3291 20130101; G09G
3/3233 20130101; G09G 2320/0252 20130101; G09G 2320/0261 20130101;
G09G 2310/0205 20130101 |
Class at
Publication: |
345/212 ;
345/204 |
International
Class: |
G06F 3/038 20060101
G06F003/038 |
Foreign Application Data
Date |
Code |
Application Number |
May 19, 2011 |
KR |
10-2011-0047525 |
Claims
1. A driving method of a display device including a plurality of
pixels, each including an organic light emitting diode (OLED), a
driving transistor connected to a driving voltage and supplying a
driving current to the OLED, a compensation capacitor connected to
a gate electrode of the driving transistor, a first storage
capacitor electrically connected to or disconnected from the
compensation capacitor, and a second storage capacitor, the method
comprising: a reset step in which an anode voltage of the OLED is
discharged; a compensation step in which a threshold voltage of the
driving transistor is stored to the compensation capacitor; a scan
step in which a data voltage is stored to the first storage
capacitor according to a corresponding data signal; and a light
emitting step in which the OLED emits light according to the
driving current flowing to the driving transistor by a data voltage
stored to the second storage capacitor, wherein the light emitting
steps of the plurality of pixels are concurrently generated, and
the scan step and the light emitting step are temporally
overlapped.
2. The driving method of claim 1, wherein the scan step includes a
step in which the connection of the first storage capacitor and the
compensation capacitor is blocked, and the first storage capacitor
is transmitted with the corresponding data signal.
3. The driving method of claim 1, wherein the light emitting step
includes a step in which the second storage capacitor and the
compensation capacitor are connected, and the voltage of the gate
electrode of the driving transistor is changed by the data voltage
stored in the second storage capacitor.
4. The driving method of claim 1, wherein the reset step includes a
step in which the driving transistor is turned on such that an
anode of the OLED is connected to the driving voltage, and a
different driving voltage input to a cathode of the OLED is higher
than the driving voltage.
5. The driving method of claim 1, wherein the compensation step
includes a step in which the first storage capacitor is connected
to the compensation capacitor, a set voltage is input to a node to
which the first storage capacitor and the compensation capacitor
are connected, and the driving transistor is diode-connected.
6. The driving method of claim 1, wherein the reset step includes a
step in which the first storage capacitor and the compensation
capacitor are connected, a set reference voltage is transmitted to
a node at which the first storage capacitor and the compensation
capacitor are connected, and the voltage of the gate electrode of
the driving transistor is initialized by the reference voltage.
7. The driving method of claim 6, wherein the reference voltage is
a level for turning on the driving transistor.
8. The driving method of claim 7, wherein the display device
further includes another driving voltage connected to a cathode of
the OLED, and a voltage level of the other driving voltage during
the reset step and the compensation step is different than that
during the light emitting step.
9. A driving method of a display device including a plurality of
pixels, each including a driving transistor, a first storage
capacitor, and a second storage capacitor, the method comprising:
programming first frame data to the first storage capacitor of each
of the plurality of pixels during a first scan period; programming
second frame data to the second storage capacitor of each of the
plurality of pixels during a second scan period; and emitting light
through the plurality of pixels by a driving current flowing in the
driving transistor of each of the plurality of pixels according to
the first frame data programmed to the first storage capacitor
during a first light emitting period, wherein the second scan
period and the first light emitting period are temporally
overlapped.
10. The driving method of claim 9, further comprising programming
third frame data preceding the first frame data to the second
storage capacitor of each of the plurality of pixels; and emitting
light through the plurality of pixels by a driving current flowing
in the driving transistor of each of the plurality of pixels
according to the third frame data programmed to the second storage
capacitor of each of the plurality of pixels during a second light
emitting period, and the second light emitting period and the first
scan period are temporally overlapped.
11. The driving method of claim 9, wherein the first frame data is
first view point data, and the second frame data is second view
point data different from the first view point data.
12. A pixel comprising: an organic light emitting diode (OLED); a
driving transistor configured to be electrically connected to a
first driving voltage and to supply a driving current to the OLED;
a compensation capacitor including one electrode connected to a
gate electrode of the driving transistor; a first operation control
transistor including one electrode connected to another electrode
of the compensation capacitor and configured to be controlled by a
first operation control signal; a second operation control
transistor including one electrode connected to the other electrode
of the compensation capacitor and configured to be controlled by a
second operation control signal; a first storage capacitor
including one electrode connected to another electrode of the first
operation control transistor; and a second storage capacitor
including one electrode connected to another electrode of the
second operation control transistor, wherein the second operation
control transistor is configured such that when it is turned on,
the second storage capacitor and the compensation capacitor are
connected during a period in which the first operation control
transistor is turned off such that a data voltage is stored to the
first storage capacitor according to a corresponding data
signal.
13. The pixel of claim 12, further comprising: a first switching
transistor including one electrode connected to the one electrode
of the first storage capacitor, and another electrode configured to
be input with the corresponding data signal and to be controlled by
a first scan signal; and a second switching transistor including
one electrode connected to the one electrode of the second storage
capacitor, and another electrode configured to be input with the
corresponding data signal and to be controlled by a second scan
signal.
14. The pixel of claim 13, further comprising a compensation
transistor connected between the gate electrode and a drain
electrode of the driving transistor.
15. The pixel of claim 14, wherein the first switching transistor
is configured to be turned on and the compensation transistor is
configured to be turned on during a compensation period.
16. The pixel of claim 12, wherein: the first storage capacitor
includes another electrode configured to be connected to the first
driving voltage; and the second storage capacitor includes another
electrode configured to be connected to the first driving
voltage.
17. The pixel of claim 12, wherein: the first storage capacitor
includes another electrode configured to be connected to a set
reference voltage different from the first driving voltage; and the
second storage capacitor includes another electrode configured to
be connected to the reference voltage.
18. The pixel of claim 12, wherein: the first driving voltage
includes a second driving voltage and a third driving voltage; the
second driving voltage and the third driving voltage have the same
waveform; and the pixel further includes a first light emitting
transistor connected between a source of the second driving voltage
and the driving transistor, and a second light emitting transistor
connected between a source of the third driving voltage and the
driving transistor.
19. The pixel of claim 12, wherein the pixel further includes a
source of a fourth driving voltage applied to a cathode of the
organic light emitting diode (OLED), and the driving transistor is
turned on during a reset period and the first driving voltage has a
lower level than the fourth driving voltage.
20. A display device comprising: a plurality of data lines for
transmitting a plurality of data signals; a plurality of first scan
lines for transmitting a plurality of first scan signals; a
plurality of second scan lines for transmitting a plurality of
second scan signals; a first operation control line and a second
operation control line for transmitting a first operation control
signal and a second operation control signal; a first voltage line
for transmitting a first driving voltage and a second voltage line
for transmitting a second driving voltage; and a plurality of
pixels each connected to a corresponding data line of the data
lines, a corresponding first scan line of the first scan lines, a
corresponding second scan line of the second scan lines, the first
operation control line, the second operation control line, the
first voltage line, and the second voltage line, wherein each of
the pixels includes an organic light emitting diode (OLED)
including a cathode connected to the second voltage line, a driving
transistor connected to the first voltage line for supplying a
driving current to the OLED, a compensation capacitor connected to
a gate electrode of the driving transistor, a first storage
capacitor and a second storage capacitor connected between the
compensation capacitor and a source of the driving voltage, and
wherein the display device is configured to provide: a first period
in which the first storage capacitor is connected to the
corresponding data line according to both a first scan signal of
the first scan signals transmitted through the corresponding first
scan line and the first operation control signal transmitted
through the first operation control line, and the compensation
capacitor is blocked; and a second period temporally overlapped
with the first period and in which the second storage capacitor is
blocked from the corresponding data line and is connected to the
compensation capacitor according to both a second scan signal of
the second scan signals transmitted through the corresponding
second scan line and the second operation control signal
transmitted through the second operation control line.
21. The display device of claim 20, wherein the display device
further includes a compensation control line for transmitting a
compensation signal, and each of the pixels further includes a
compensation transistor connected between the gate electrode and a
drain electrode of the driving transistor and operated according to
the compensation signal.
22. The display device of claim 21, wherein during a reset period
in which the compensation transistor is turned on and the first
driving voltage transmitted through the first voltage line is at a
first level, the display device is configured to provide the second
driving voltage with a voltage level transmitted through the second
voltage line that is different from the level of the second driving
voltage during the first period and the second period.
23. The display device of claim 22, wherein the first driving
voltage is at a second level different from the first level during
the first period and the second period.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to and the benefit of
Korean Patent Application No. 10-2011-0047525, filed in the Korean
Intellectual Property Office on May 19, 2011, the entire content of
which is incorporated herein by reference.
BACKGROUND
[0002] 1. Field
[0003] The following description relates to a pixel, a display
device including the same, and a driving method thereof.
Particularly, the following description relates to a pixel
including an organic light emitting diode (OLED), a display device
of an active matrix type including the same, and a driving method
thereof.
[0004] 2. Description of the Related Art
[0005] One frame of the active matrix type of display device
includes a scan period for programming image data and a light
emitting period for emitting light according to the programmed
image data. However, as the size of the display panel and the
resolution thereof is increased, the Resitive-Capacitive (RC) delay
of the display panel is increased. Thus, the time for programming
the image data to each pixel of the display panel is increased such
that it is difficult to drive the display device.
[0006] Also, when the display device displays a stereoscopic image,
this problem may be more severe.
[0007] When the display device displays the stereoscopic image
according to a National Television System Committee (NTSC) method,
the display device must alternately display left eye pictures of 60
frames and right eye pictures of 60 frames during one second.
Accordingly, the driving frequency of the display device to display
the stereoscopic image must be at least twice compared with the
display device displaying a plane image.
[0008] In the case of displaying the stereoscopic image, data
writing must be completed within at least 1/120 of a second, and
therefore a driver operating with a high driving frequency to scan
the entire display panel during the scan period and to program the
image data is required. The driver of the high driving frequency
increases production cost.
[0009] The above information disclosed in this Background section
is only for enhancement of understanding of the background of the
invention and therefore it may contain information that does not
form the prior art that is already known in this country to a
person of ordinary skill in the art.
SUMMARY
[0010] Aspects of embodiments of the present invention are directed
toward a pixel suitable for a large-sized and high resolution
display device and that displays a stereoscopic image, a display
device including the same, and a driving method thereof.
[0011] A display device according to an embodiment of the present
invention includes a plurality of pixels including an organic light
emitting diode (OLED), a driving transistor connected to a driving
voltage and supplying a driving current to the organic light
emitting diode (OLED), a compensation capacitor connected to the
gate electrode of the driving transistor, a first storage capacitor
electrically connected to or disconnected from the compensation
capacitor, and a second storage capacitor. A driving method of the
display device includes: a reset step in which an anode voltage of
the organic light emitting diode (OLED) is discharged; a
compensation step in which a threshold voltage of the driving
transistor is stored to the compensation capacitor; a scan step in
which the data voltage is stored to the first storage capacitor
according to the corresponding data signal; and a light emitting
step in which the organic light emitting diode (OLED) emits light
according to the driving current flowing to the driving transistor
by the data voltage stored to the second storage capacitor, wherein
the light emitting steps of the plurality of pixels are
concurrently or simultaneously generated, and the scan step and the
light emitting step are temporally overlapped.
[0012] In one embodiment, the scan step includes a step in which
the connection of the first storage capacitor and the compensation
capacitor is blocked, and the first storage capacitor is
transmitted with the corresponding data signal.
[0013] In one embodiment, the light emitting step includes a step
in which the second storage capacitor and the compensation
capacitor are connected, and the voltage of the gate electrode of
the driving transistor is changed by the data voltage stored in the
second storage capacitor.
[0014] In one embodiment, the reset step includes a step in which
the driving transistor is turned on such that the anode of the
organic light emitting diode (OLED) is connected to the driving
voltage, and a different driving voltage input to a cathode of the
organic light emitting diode (OLED) is higher than the driving
voltage.
[0015] In one embodiment, the compensation step includes a step in
which the first storage capacitor is connected to the compensation
capacitor, a set or predetermined voltage is input to a node at
which the first storage capacitor and the compensation capacitor
are connected, and the driving transistor is diode-connected.
[0016] In one embodiment, the reset step includes a step in which
the first storage capacitor and the compensation capacitor are
connected, a set or predetermined reference voltage is transmitted
to the voltage of the node at which the first storage capacitor and
the compensation capacitor are connected, and the voltage of the
gate electrode of the driving transistor is initialized by the
reference voltage. In one embodiment, the reference voltage is at a
level that turns on the driving transistor.
[0017] In one embodiment, the display device further includes
another driving voltage connected to the cathode of the organic
light emitting diode (OLED), and a voltage level of the other
driving voltage during the reset step and compensation step is
different than that during the light emitting period.
[0018] A display device according to an embodiment of the present
invention includes a plurality of pixels each including a driving
transistor, a first storage capacitor, and a second storage
capacitor. A driving method of the display device includes:
programming first frame data to the first storage capacitor of each
of the plurality of pixels during a first scan period; programming
second frame data to the second storage capacitor of each of the
plurality of pixels during a second scan period; and emitting light
through the plurality of pixels by a driving current flowing in the
driving transistor of each of the plurality of pixels according to
the first frame data programmed to the first storage capacitor
during a first light emitting period, wherein the second scan
period and the first light emitting period are temporally
overlapped.
[0019] In one embodiment, the driving method of the display device
further includes a step in which the third frame data preceding the
first frame is programmed to the second storage capacitor of each
of the plurality of pixels, and the plurality of pixels emit light
during a second light emitting period by a driving current flowing
in the driving transistor of each of the plurality of pixels
according to the third frame data programmed to the second storage
capacitor of each of the plurality of pixels, and the second light
emitting period and the first scan period are temporally
overlapped.
[0020] In one embodiment, the first frame data is first view point
data, and the second frame data is second view point data different
from the first view point.
[0021] A pixel of a display device according to an embodiment of
the present invention includes: an organic light emitting diode
(OLED); a driving transistor electrically connected to a first
driving voltage and supplying a driving current to the organic
light emitting diode (OLED); a compensation capacitor including one
electrode connected to the gate electrode of the driving
transistor; a first operation control transistor including one
electrode connected to the other electrode of the compensation
capacitor and controlled by the first operation control signal; a
second operation control transistor including one electrode
connected to the other electrode of the compensation capacitor and
controlled by the second operation control signal; a first storage
capacitor including one electrode connected to the other electrode
of the first operation control transistor; and a second storage
capacitor including one electrode connected to the other electrode
of the second operation control transistor, wherein the second
operation control transistor is turned on such that the second
storage capacitor and the compensation capacitor are connected
during a period in which the first operation control transistor is
turned off such that the data voltage is stored to the first
storage capacitor according to the corresponding data signal.
[0022] In one embodiment, the pixel further includes a first
switching transistor including one electrode connected to the one
electrode of the first storage capacitor and the other electrode
input with the corresponding data signal and controlled by the
first scan signal, and a second switching transistor including one
electrode connected to one electrode of the second storage
capacitor and the other electrode input with the corresponding data
signal and controlled by the second scan signal.
[0023] In one embodiment, the pixel further includes a compensation
transistor connected between the gate electrode and the drain
electrode of the driving transistor.
[0024] In one embodiment, the first switching transistor is turned
on and the compensation transistor is turned on during a
compensation period.
[0025] In one embodiment, the first storage capacitor includes the
other electrode connected to the first driving voltage, and the
second storage capacitor includes the other electrode connected to
the first driving voltage.
[0026] In one embodiment, the first storage capacitor includes the
other electrode connected to a set or predetermined reference
voltage different from the first driving voltage, and the second
storage capacitor includes the other electrode connected to the
reference voltage.
[0027] In one embodiment, the first driving voltage includes a
second driving voltage and a third driving voltage, the second
driving voltage and the third driving voltage have the same
waveform, and the pixel further includes a first light emitting
transistor connected between the second driving voltage and the
driving transistor, and a second light emitting transistor
connected between the third driving voltage and the driving
transistor.
[0028] In one embodiment, the pixel further includes a source of a
fourth driving voltage applied to a cathode of the organic light
emitting diode (OLED), and the driving transistor is turned on
during a reset period and the first driving voltage has a lower
level than the fourth driving voltage.
[0029] A display device according to an embodiment of the present
invention includes: a plurality of data lines transmitting a
plurality of data signals; a plurality of first scan lines
transmitting a plurality of first scan signals; a plurality of
second scan lines transmitting a plurality of second scan signals;
a first operation control line and a second operation control line
transmitting a first operation control signal and a second
operation control signal; a first voltage line transmitting a first
driving voltage and a second voltage line transmitting a second
driving voltage; and a plurality of pixels each connected to the
corresponding data line, the corresponding first scan line, the
corresponding second scan line, the first operation control line,
the second operation control line, the first voltage line, and the
second voltage line, wherein the pixel includes an organic light
emitting diode (OLED) including a cathode connected to the second
voltage line, a driving transistor connected to the first voltage
line supplying a driving current to the organic light emitting
diode (OLED), a compensation capacitor connected to a gate
electrode of the driving transistor, a first storage capacitor and
a second storage capacitor connected between the compensation
capacitor and a source of the driving voltage, and wherein the
display device is configured to provide: a first period in which
the first storage capacitor is connected to the corresponding data
line according to both the first scan signal transmitted through
the corresponding first scan line and the first operation control
signal transmitted through the first operation control line, and
the compensation capacitor is blocked; and a second period
temporally overlapped with the first period and in which the second
storage capacitor is blocked from the corresponding data line and
is connected to the compensation capacitor according to both a
second scan signal transmitted through the corresponding second
scan line and the second operation control signal transmitted
through the second operation control line.
[0030] In one embodiment, the display device further includes a
compensation control line transmitting a compensation signal, and
the pixel further includes a compensation transistor connected
between the gate electrode and the drain electrode of the driving
transistor and operated according to the compensation signal.
[0031] In one embodiment, during a reset period in which the
compensation transistor is turned on and the first driving voltage
transmitted through the first voltage line is at a first level, the
display device is configured to provide the second driving voltage
level transmitted through the second voltage line that is different
from the level of the second driving voltage during the first
period and the second period. In one embodiment, the first driving
voltage is at a second level different from the first level during
the first period and the second period.
[0032] Embodiments of the present invention provide a pixel
suitable for a large size and high resolution display device that
can display a stereoscopic image, a display device including the
same, and a driving method thereof.
BRIEF DESCRIPTION OF THE DRAWINGS
[0033] FIG. 1 is a view showing a case of driving all pixels of a
display unit divided into two groups.
[0034] FIG. 2 is a view of a motion artifact that may be generated
in a display device.
[0035] FIG. 3 is a view showing a driving method of a display
device according to an exemplary embodiment of the present
invention.
[0036] FIG. 4 is a view showing a display unit of a display device
according to an exemplary embodiment of the present invention.
[0037] FIG. 5 is a view of a pixel structure according to an
exemplary embodiment of the present invention.
[0038] FIG. 6 is a view showing a driving waveform of a display
device according to an exemplary embodiment of the present
invention.
[0039] FIG. 7 is a view of a case when a stereoscopic image is
displayed according to a simultaneous light emitting driving method
according to an exemplary embodiment of the present invention.
[0040] FIG. 8 is a view of another pixel structure according to an
exemplary embodiment of the present invention.
[0041] FIG. 9 is a view of another pixel structure according to an
exemplary embodiment of the present invention.
[0042] FIG. 10 is a view of a display device according to an
exemplary embodiment of the present invention.
DETAILED DESCRIPTION
[0043] In the following detailed description, only certain
exemplary embodiments of the present invention have been shown and
described, simply by way of illustration. As those skilled in the
art would realize, the described embodiments may be modified in
various different ways, all without departing from the spirit or
scope of the present invention. Accordingly, the drawings and
description are to be regarded as illustrative in nature and not
restrictive. Like reference numerals designate like elements
throughout the specification.
[0044] Throughout this specification and the claims that follow,
when it is described that an element is "coupled" to another
element, the element may be "directly coupled" to the other element
or "indirectly or electrically coupled" to the other element
through one or more third elements. In addition, unless explicitly
described to the contrary, the word "comprise" and variations such
as "comprises" or "comprising" will be understood to imply the
inclusion of stated elements, but not the exclusion of any other
elements.
[0045] A display device according to an exemplary embodiment of the
present invention is operated by a concurrent or simultaneous light
emitting method. The concurrent or simultaneous light emitting
method is a method in which a plurality of pixels that are
light-emitted during a corresponding frame, concurrently or
simultaneously emit light such that an image of one frame displayed
by the display device is concurrently or simultaneously
displayed.
[0046] For concurrent or simultaneous light emitting by all pixels
during the light emitting period, data writing must be completed
for all pixels before the light emitting period. If the period of
one frame is divided into a scan period for programming the data to
all pixels and the light emitting period, the scan period may be
less than half of one frame period. Also, the light emitting period
may be less than half of one frame period.
[0047] To sufficiently obtain the light emitting period and the
scan period, all pixels of the display device are divided into two
groups, and two groups may be alternatively operated with the scan
period or the light emitting period.
[0048] FIG. 1 is a view showing a case of driving all pixels of a
display unit divided into two groups.
[0049] A plurality of pixels of the display unit are divided into a
plurality of first group pixels emitting light during a first field
and a plurality of second group pixels emitting light during a
second field. The first field and the second field are display
periods including at least one frame, and one frame may
sequentially include a reset period 1, a compensation period 2, a
scan period 3, and a light emitting period 4.
[0050] The reset period 1 is a period for resetting an anode
voltage of an organic light emitting diode (OLED) by a discharge,
and compensating a threshold voltage of the driving transistor of
the pixel of the compensation period 2.
[0051] Also, the first field EFD and the second field OFD are
driven in synchronization with a time that is moved by a set or
predetermined period SF. In detail, one frame 1FO of the second
field temporally close to one frame 1FE of the first field EFD is
temporally shifted by a period SF from the start of the one frame
1FE. The period SF is set up to not overlap the scan period 3. One
frame 2FE of the first field is continuous after the frame 1FE, and
one frame 2FO of the second field is continuous after the frame
1FO.
[0052] During the period 4 in which the first group pixels emit
light, the scan period 3 in which the data signal respectively
corresponding to the second group pixels is programmed. Likewise,
during the period 4 in which the second group pixels emit the
light, the scan period 3 in which the data signal respectively
corresponding to the second group pixels is programmed, is
generated. Accordingly, the scan period 3 may be sufficiently
obtained such that a temporal margin to drive the display panel is
increased. Also, the scan frequency may be decreased such that the
bandwidths of both a data driver generating and transmitting a data
signal to a data line, and a scan driver generating the scan
signal, are decreased, and resultantly the cost of circuit parts
may be reduced.
[0053] As described above, when the pixels are divided into two
groups and the field in which each group emits light is divided and
operated, the display device may be manufactured with a large size
and high resolution. Also, the display device is driven according
to the concurrent or simultaneous light emitting such that a motion
blur may be reduced compared with the conventional art of
sequentially emitting the light according to the scan lines. In
addition, when two groups respectively display the image of a set
or predetermined view point, the display device displays a screen
of different view points for two groups such that a stereoscopic
image display is possible.
[0054] However, to divide a plurality of pixels into two groups, a
driving voltage must be divided and supplied to two groups, and a
wire supplying the driving voltage must be separated. Also, the
pixel circuit structure and wire structure may be complicated
according to the arrangement of the first group pixels and the
second group pixels. That is, the panel design may be
complicated.
[0055] The data representing the image must also be mapped
according to the arrangement of the first group pixels and the
second group pixels such that the constitution and operation of a
controller mapping the data may be complicated.
[0056] In addition, since a time difference of the light emitting
exists between the first group pixels and the second group pixels,
when a pattern is moved with a set or predetermined speed, the
shape and arrangement in the panel of the first group pixels and
the second group pixels may be recognized as a pattern. This is
referred to as a motion artifact.
[0057] FIG. 2 is a view of a motion artifact that may be generated
in a display device. FIG. 2 shows the motion artifact that may be
generated when the first group pixels and the second group pixels
are formed per pixel row.
[0058] As shown in FIG. 2, the arrangement of the first group
pixels and the second group pixels is recognized. Thus, as shown in
FIG. 2, the motion artifact in which the block edges of each group
appear to be missing according to the arrangement of two groups may
be generated.
[0059] Embodiments of the present invention provide a display
device in which the operation of the light emitting period and the
operation of the scan period are executed for a plurality of
pixels, as a display device driven by the concurrent or
simultaneous light emitting method. Thus, the scan period and the
light emitting period may be sufficiently obtained, and the
above-described drawbacks such as the motion artifact generated in
the display device in which the pixels are not divided into two
groups may be reduced or prevented.
[0060] In addition, the scan and light emitting are executed
together for each pixel such that the display device of an
embodiment of the present invention may extend the data writing
period and the light emitting period.
[0061] Next, an exemplary embodiment of the present invention will
be described with reference to FIG. 3.
[0062] FIG. 3 shows a driving method of a display device according
to an exemplary embodiment of the present invention.
[0063] As shown in FIG. 3, one frame includes the reset period 1,
the compensation period 2, the scan period 3, and the light
emitting period 4. The scan period 3 and the light emitting period
4 are generated to be temporally overlapped.
[0064] The pixel emits light at the light emitting period 4 of the
current frame according to the data programmed at the scan period 3
of the previous frame, and the pixel emits light at the light
emitting period 4 of the next frame according to the data
programmed to the pixel at the scan period 3 of the current
frame.
[0065] The period T1 includes the scan period 3 and the light
emitting period 4 of the N-th frame. Accordingly, the data
programmed to the pixels at the scan period 3 of the period T1 is
the data of the N-th frame, and the pixels emit light according to
the data of the N-th frame programmed at the scan period 3 of the
(N-1)-th frame at the light emitting period 4 of the period T1.
[0066] The period T2 includes the scan period 3 and the light
emitting period 4 of the (N+1)-th frame. Accordingly, the data
programmed to the pixels at the scan period 3 of the period T2 is
the data of the (N+1)-th frame, and the pixels at the light
emitting period 4 of the period T2 emit the light according to the
data of the N-th frame programmed at the scan period 3 (that is,
the period T1) of the N-th frame.
[0067] In the scan period 3 of the periods T3 and T4, the data of
the (N+2)-th frame and the data of the (N+3)-th frame are
programmed to the pixels, and in the light emitting period 4 of the
periods T3 and T4, the pixels emit light according to both the data
programmed at the scan period 3 of the (N+1)-th frame and the data
programmed at the scan period 3 of the (N+2)-th frame.
[0068] A structure of the pixel in which (1) the data of the
current frame is programmed during the scan period 3 and (2) the
pixel is emitting light according to the data of the previous frame
and during the light emitting period 4 that is temporally
overlapped with the scan period 3 will be described with reference
to FIG. 4 and FIG. 5.
[0069] FIG. 4 is a view of a display unit 100 of a display device
according to an exemplary embodiment of the present invention.
[0070] As shown in FIG. 4, the display unit 100 includes a
plurality of first scan lines SA1-SAn, a plurality of second scan
lines SB1-SBn, a plurality of data lines data1-datam, a first
voltage line 101, a second voltage line 102, a compensation control
line 103, a first operation control line 104, and a second
operation control line 105.
[0071] The plurality of first scan lines SA1-SAn respectively
extend in a transverse direction, and are respectively connected to
a plurality of pixels PX of one row. The plurality of second scan
lines SB1-SBn respectively extend in the transverse direction, and
are respectively connected to a plurality of pixels PX of one
row.
[0072] The plurality of data lines data1-datam extend in a
longitudinal direction, and intersect or cross the transverse
direction of the plurality of first scan lines SA1-SAn and the
plurality of second scan lines SB1-SBn. The plurality of data lines
data1-datam are each connected to a plurality of pixels PX of one
column.
[0073] The first voltage line 101 is a wire for transmitting a
driving voltage ELVDD to a plurality of pixels PX. The first
voltage line 101 may be connected to a plurality of pixels PX. In
FIG. 4, as one example, the first voltage line 101 is formed with a
plurality of wires formed in the longitudinal direction and with
one connection wire connecting them.
[0074] The second voltage line 102 is a wire for transmitting a
driving voltage ELVSS to a plurality of pixels PX. The second
voltage line 102 may be also connected to a plurality of pixels PX.
In FIG. 4, as one example, the second voltage line 101 includes a
plurality of wires formed in the longitudinal direction and one
connection wire connecting them.
[0075] The compensation control line 103 is a wire for transmitting
a compensation control signal GC to a plurality of pixels PX. The
compensation control line 103 may also be connected to a plurality
of pixels PX. In FIG. 4, as one example, the compensation control
line 103 includes a plurality of wires formed in the transverse
direction and one connection wire connecting them.
[0076] The first operation control line 104 is a wire for
transmitting the first operation control signal MA to a plurality
of pixels PX. The first operation control line 104 may be connected
to a plurality of pixels PX. In FIG. 4, as one example, the first
operation control line 104 includes a plurality of wires formed in
the transverse direction and one connection wire connecting
them.
[0077] The second operation control line 105 is a wire for
transmitting the second operation control signal MB to a plurality
of pixels PX. The second operation control line 105 may be
connected to a plurality of pixels PX. In FIG. 4, as one example,
the second operation control line 105 includes a plurality of wires
formed in the transverse direction and one connection wire
connecting them.
[0078] A plurality of pixels PX are respectively connected to a
corresponding data line of a plurality of data lines, a
corresponding first scan line of a plurality of first scan lines, a
corresponding second scan line of a plurality of second scan lines,
two driving voltage lines, the compensation control line, the first
operation control line, and the second operation control line.
[0079] Next, the pixel structure will be described with reference
to FIG. 5.
[0080] FIG. 5 is a view of a pixel structure according to an
exemplary embodiment of the present invention. The pixel PX shown
in FIG. 5 is a pixel connected to the first scan line SAi, the
second scan line SBi, and the data line dataj. The other pixels are
the same as the pixel shown in FIG. 5.
[0081] As shown in FIG. 5, the pixel includes six transistors TD,
TSA, TSB, TMA, TMB, and TGC, two storage capacitors CA and CB, a
compensation capacitor CTH, and an organic light emitting diode
(OLED).
[0082] The driving voltage ELVDD and the driving voltage ELVSS for
operating the pixel are supplied to both terminals to which the
driving transistor TD and the organic light emitting diode (OLED)
are connected in series.
[0083] The six transistors TD, TSA, TSB, TMA, TMB, and TGC shown in
FIG. 5 are P-channel-type transistors. However, the present
invention is not limited thereto, and the channel type of each
transistor is determined according to the signal level input to the
gate electrode of each transistor and the operation state of each
transistor according to the signal level.
[0084] The driving transistor TD includes the source electrode
connected to the driving voltage ELVDD, the drain electrode
connected to the anode of the organic light emitting diode (OLED),
and the gate electrode connected to the compensation capacitor
CTH.
[0085] The compensation transistor TGC includes both electrodes
respectively connected to the gate electrode and the drain
electrode of the driving transistor TD, and the gate electrode
input with the compensation control signal GC. The compensation
transistor TGC diode-connects the driving transistor TD of the
compensation period 2.
[0086] The compensation capacitor CTH includes one electrode
connected to the gate electrode of the driving transistor TD, and
the other electrode connected to each one electrode of two
transistors TMA and TMB.
[0087] The first operation control transistor TMA includes the gate
electrode input with the first operation control signal MA, one
electrode connected to the other electrode of the compensation
capacitor CTH, and the other electrode connected to both one
electrode of the first switching transistor TSA and one electrode
of the storage capacitor CA.
[0088] The first switching transistor TSA includes the gate
electrode input with the scan signal SA[i], one electrode connected
to both the other electrode of the first operation control
transistor TMA and the one electrode of the capacitor CA, and the
other electrode connected to the data line dataj.
[0089] The second operation control transistor TMB includes the
gate electrode input with the first operation control signal MB,
one electrode connected to the other electrode of the compensation
capacitor CTH, and the other electrode connected to both one
electrode of the first switching transistor TSB and one electrode
of the storage capacitor CB.
[0090] The second switching transistor TSB includes the gate
electrode input with the scan signal SB[i], one electrode connected
to both the other electrode of the second operation control
transistor TMB and the one electrode of the storage capacitor CB,
and the other electrode connected to the data line dataj.
[0091] The other electrode of the storage capacitor CA is connected
to the voltage ELVDD, and the other electrode of the storage
capacitor CB is connected to the voltage ELVDD.
[0092] The pixel shown in FIG. 5 includes the first path driving
the driving transistor TD according to the data signal programmed
to the storage capacitor CA, and the second path driving the
driving transistor TD according to the data signal programmed to
the storage capacitor CB.
[0093] The switch controlling a connection and a disconnection of
the first path is the transistor MA, and the switch controlling the
connection and the disconnection of the second path is the
transistor MB. The transistor MA is controlled by the first
operation control signal MA, and the transistor MB is controlled by
the second operation control signal MB.
[0094] FIG. 6 is a view showing a driving waveform of a display
device according to an exemplary embodiment of the present
invention.
[0095] As shown in FIG. 6, the driving voltages ELVDD and ELVSS,
the first scan signals SA[1]-SA[n], the second scan signals
SB[1]-SB[n], the first operation control signal MA, the second
operation control signal MB, the data signals data[1]-data[m], and
the compensation control signal GC are changed according to the
reset period 1, the compensation period 2, the scan period 3, and
the light emitting period 4.
[0096] In FIG. 6, an initialization period INIT is further included
before the reset period 1 of each frame. The reset period according
to an exemplary embodiment of the present invention further
includes the initialization period. The initialization operation
may be omitted according to the characteristics of the display
panel.
[0097] During the period in which the first scan signals
SA[1]-SA[n] are at the enable ENABLE level among the initialization
period INIT, the data signals data[1]-data[m] are changed into the
reference voltage for initializing the node ND. The first switching
transistor TSA is the P-channel type such that the enable ENABLE
level of the first scan signals SA[1]-SA[n] is the low level.
[0098] The level of the reference voltage is set as a level to
improve the response waveform of the organic light emitting diode
(OLED).
[0099] The response waveform of the organic light emitting diode
(OLED) is affected by a hysteresis characteristic of the driving
transistor TD supplying the driving current to the organic light
emitting diode (OLED). For example, in the characteristic curve
between the drain current and the gate-source voltage of the
driving transistor, a difference between the drain current of the
direction that the gate-source voltage is increased and the drain
current of the direction that the gate-source voltage is decreased,
is generated. This phenomenon is the hysteresis characteristic of
the driving transistor.
[0100] For the same data signal, if the current flowing to the
organic light emitting diode (OLED) when the organic light emitting
diode (OLED) is changed from high luminance to low luminance, and
the current flowing to the organic light emitting diode (OLED) when
the organic light emitting diode (OLED) is changed from low
luminance to high luminance are different, then a motion blur is
generated. This means that the response waveform of the organic
light emitting diode (OLED) is affected in a case of receiving
influence by the hysteresis characteristic.
[0101] The initialization period is to eliminate the hysteresis
characteristic by initializing the voltage of the gate electrode of
the driving transistor.
[0102] The transistors in an exemplary embodiment of the present
invention are all the P-channel type such that the enable level is
the low level capable of fully turning on the transistor of the
P-channel type. In contrast, the disable level is the high level
capable of fully turning off the transistor of the P-channel
type.
[0103] In an exemplary embodiment of the present invention, the
reference voltage is set up as the voltage of the low level,
however it may be changed according to the channel type of the
driving transistor. That is, when the driving transistor is the
N-channel type, the reference voltage may be set up as the voltage
of the high level.
[0104] In the initialization period INIT, during the period in
which the first scan signal SA[1]-SA[n] is the enable level and the
first operation control signal MA is the enable level, the first
switching transistor TSA and the first operation control transistor
TMA are turned on such that the data signals data[1]-data[m] are
transmitted to the node ND. Here, the data signals data[1]-data[m]
are the reference voltage of the low level such that the voltage of
the node ND is decreased and the gate voltage of the driving
transistor TD is decreased.
[0105] The voltage of the node ND of each of all pixels is
decreased to the reference voltage at the initialization period
INIT such that the gate voltage of the driving transistor TD of
each of all pixels is decreased by the decreasing voltage of the
node ND to become the low voltage at the low level, and thereby the
driving transistor TD is turned on. At this time, the driving
voltage ELVSS is the high level such that the current does not flow
to the organic light emitting diode (OLED) and the light is not
emitted.
[0106] If the driving voltage ELVDD becomes the low level in the
reset period 1, the anode voltage of the organic light emitting
diode (OLED) is reset to the driving voltage (ELVDD) level through
the driving transistor TD of the on state. In the reset period 1,
the first scan signals SA[1]-SA[n] are the disable level such that
the first switching transistor TSA is in the turned off state.
[0107] If the compensation control signal GC becomes the low level
at the time point T11 among the reset period 1, the compensation
transistor TGC is turned on, and thereby the gate electrode of the
driving transistor TD and the anode of the organic light emitting
diode (OLED) are connected.
[0108] If the driving voltage ELVDD becomes the high level in the
compensation period 2, the gate electrode and the drain electrode
of the driving transistor TD are connected by the compensation
transistor TGC of the on state. That is, the driving transistor TD
is diode-connected. Thus, the current flows through the
diode-connected driving transistor TD. At this time, the driving
voltage ELVSS is the high level such that the current does not flow
to the organic light emitting diode (OLED) and the light is not
emitted.
[0109] In the compensation period 2, the first scan signals
SA[1]-SA[n] are all at the low level and the first switching
transistor TSA is turned on, and thereby the data signals
data[1]-data[m] are transmitted to the node ND. The voltage of the
data signals data[1]-data[m] of the compensation period 2 is
referred to as an assistance voltage VSUS. In an exemplary
embodiment of the present invention, the assistance voltage VSUS is
set up as 10V, and the driving voltage ELVDD is set up as 12V in
the compensation period 2, however the present invention is not
limited thereto.
[0110] The voltage of the node NG is ELVDD+VTH (the threshold
voltage of the driving transistor TD) by the diode-connected
driving transistor TD, and the voltage of the node ND is VSUS such
that the voltage ELVDD+VTH-VSUS is stored to the compensation
capacitor CTH.
[0111] If the compensation control signal GC becomes the high
level, then the compensation transistor TGC is turned off, and the
voltage of the node ND and the node NG is maintained by the
capacitor CA and the compensation capacitor CTH that is connected
to the compensation capacitor CTH in series.
[0112] The scan period 3 and the light emitting period 4
concurrently or simultaneously progress after the compensation
period 2. The driving current following to the data signal
programmed to the pixel PX during the scan period of the previous
frame (the (N-1)-th frame, not shown) of the N-th frame is
generated such that the organic light emitting diode (OLED) emits
the light. The data signals data[1]-data[m] transmitted to a
plurality of pixels PX during the scan period of the (N-1)-th frame
is stored to the capacitor CB.
[0113] A plurality of data signals data[1]-data[m] are sequentially
transmitted to a plurality of pixels PX during the N-th frame scan
period 3. The data signal data[1]-data[m] programmed at the N-th
frame is stored to the capacitor CA.
[0114] After the compensation period 2 is finished, the driving
voltage ELVSS is decreased from the high level 10V to the low level
0V, the first operation control signal MA is changed from the low
level to the high level, and the second operation control signal MB
is changed from the high level to the low level. The first
operation control signal MA and the second operation control signal
MB are inverse, and the levels of the two operation control signals
MA and MB are changed every frame at the scan period 3 and the
light emitting period 4.
[0115] During the scan period 3 and light emitting period 4, the
light emitting is operated by the operation control signal turning
on either the first operation control transistor TMA or the second
operation control transistor TMB, and the scan operation is
executed by the operation control signal turning off either the
first operation control transistor TMA or the second operation
control transistor TMB.
[0116] In FIG. 6, as an example, during the scan period 3 and the
light emitting period 4 of the N-th frame, the first operation
control signal MA is at the high level turning off the first
operation control transistor TMA such that the scan operation in
which the data signal data[1]-data[m] of the N-th frame is
programmed to the storage capacitor CA is executed. Also, the
second operation control signal MB is at the low level turning on
the second operation control transistor TMB such that the driving
transistor TD controls the driving current according to the data
signal stored to the storage capacitor CB, and the light emitting
operation in which the organic light emitting diode (OLED) emits
the light by the driving current is executed.
[0117] Firstly, the light emitting operation of the N-th frame is
described. The second operation control signal MB is the low level
such that the second operation control transistor TMB is turned on,
and then the node ND is connected to the storage capacitor CB. The
storage capacitor CB is stored with the data signal of the previous
(N-1)-th frame.
[0118] The data signal stored to the storage capacitor CB is
applied to the node ND by the turn-on of the second operation
control transistor TMB. The parasitic capacitor CP of the driving
transistor TD (not shown) and the compensation capacitor CTH are
connected in series such that the capacitor of the driving
transistor for the node ND is the capacitor CX(CTH*CP/(CTH+CP)) of
which the compensation capacitor CTH and the parasitic capacitor CP
are connected in series.
[0119] The capacitor CX and the capacitor CB are connected in the
light emitting period 4 in series, and the voltage VDT of the node
ND by the charge sharing of two capacitors is as in the following
Equation 1.
VDT=a*Vdata Equation 1
[0120] Here, a is equal to CB/CB+CX. Capacitances of the capacitor
CB and the capacitor CX are represented by "CB" and "CX",
respectively. The Vdata is equal to the voltage stored to the
capacitor CB according to the data signal of the previous (N-1)-th
frame.
[0121] The voltage stored to the capacitor CB is changed according
to the charge sharing of two capacitors, and the node ND is changed
to the voltage VDT. The node ND and the gate electrode NG are
coupled by the capacitor CTH, and the voltage of the gate electrode
NG is also changed to the voltage ELVDD+VTH-VSUS+VDT according to
the voltage change VDT-VSUS of the node ND.
[0122] The driving current IOLED supplied to the organic light
emitting diode (OLED) through the driving transistor VD during the
light emitting period 4 is as in the following Equation 2.
IOLED=k(VGS-VTH) 2=k((ELVDD+VTH-VSUS+VDT)-ELVDD-VTH) 2=k(VDT-VSUS)
2 Equation 2
[0123] Here, k is equal to a constant determined according to an
inherent parameter of the driving transistor TD.
[0124] As shown in Equation 2, the driving current IOLED is not
influenced by the threshold voltage of the driving transistor and
the driving voltage ELVDD. Accordingly, the driving current is not
influenced by the threshold voltage deviation between the driving
transistors and the voltage drop IR-DROP generated in the wire
supplying the driving voltage, and is determined according to the
data signal.
[0125] Next, the scan period 3 is described.
[0126] The capacitor CA blocked with the node ND by the first
operation control signal MA is programmed with the data signal of
the N-th frame during the scan period 3. The voltage of the node ND
of the light emitting period 4 of the next (N+1)-th frame is
determined according to the voltage stored to the capacitor CA
during the scan period 3, and the voltage of the gate electrode NG
of the driving transistor TD is determined.
[0127] A plurality of first scan signals SA[1]-SA[m] become the
pulse signals of the low level that is sequentially the enable
level during the scan period 3. Thus, the first switching
transistor TSA of a plurality of pixels connected to the scan line
supplied with the first scan signals SA[1]-SA[m] of the low level
pulse is turned on, and the corresponding data signal among a
plurality of data signals data[1]-data[m] is stored to the
capacitor CA through the turned-on first switching transistor
TSA.
[0128] As described above, the N-th frame is finished, and the next
(N+1)-th frame is started. During the initialization period INIT,
the reset period 1, and the compensation period 2 of the (N+1)-th
frame, the second operation control transistor TMB is in the
turn-on state, and the first operation control transistor TMA is in
the turn-off state.
[0129] As shown in FIG. 6, during the light emitting period 4 of
the N-th frame, and the initialization period INIT, the reset
period INIT, and the compensation period INIT of the (N+1)-th
frame, the second operation control signal MB is at the low level
of the enable level, and the first operation control signal MA is
at the high level of the disable level.
[0130] As the signals alternately having the enable level and the
disable level, the first operation control signal MA and the second
operation control signal MB are operated at the same frequency, and
have a phase difference of one frame.
[0131] The initialization period INIT and the compensation period 2
of the (N+1)-th frame are executed through the second operation
control transistor TMB differently from the N-th frame. Also, the
second operation control signal MB is at the disable level and the
scan operation is executed to the capacitor CB during the scan
period 3 of the (N+1)-th frame. Also, the first operation control
signal MA becomes the enable level during the light emitting period
4 of the (N+1)-th frame, and a plurality of pixels PX emit the
light according to a plurality of data signals programmed during
the scan period 3 of the N-th frame.
[0132] In the initialization period INIT, since the first scan
signals SB[1]-SB[n] are the enable level and the second operation
control signal MB is the enable level, the second switching
transistor TSB and the second operation control transistor TMB are
turned on such that the data signals data[1]-data[m] are
transmitted to the node ND. Here, the data signals data[1]-data[m]
are the reference voltage of the low level such that the voltage of
the node ND is initialized to the reference voltage and the gate
voltage of the driving transistor TD is decreased.
[0133] The voltage of the node ND of each of all pixels is
decreased to the reference voltage at the initialization period
INIT such that the gate voltage of the driving transistor TD of
each of all pixels is decreased by the decreasing voltage of the
node ND to become the low voltage at the low level. The driving
voltage ELVSS is the high level such that the current does not flow
to the organic light emitting diode (OLED), and the light is not
emitted.
[0134] If the driving voltage ELVDD is at the low level in the
reset period 1, the anode voltage of the organic light emitting
diode (OLED) is reset to the driving voltage ELVDD level through
the on state of the driving transistor TD. The first scan signals
SB[1]-SB[n] are the disable level in the reset period 1 such that
the second switching transistor TSB is in the turn-off state.
[0135] If the compensation control signal GC is at the low level at
the time point T12 of the reset period 1, the compensation
transistor TGC is turned on such that the gate electrode of the
driving transistor TD is connected to the anode of the organic
light emitting diode (OLED).
[0136] If the driving voltage ELVDD is at the high level in the
compensation period 2, the driving transistor TD is
diode-connected. Thus, the current flows through the
diode-connected driving transistor TD. Here, the driving voltage
ELVSS is at the high level such that the current does not flow to
the organic light emitting diode (OLED) and the light is not
emitted.
[0137] In the compensation period 2, the first scan signals
SB[1]-SB[n] are all at the low level and the second switching
transistor TSB is turned on such that the data signals
data[1]-data[m] are transmitted to the node ND. The data signals
data[1]-data[m] of the compensation period 2 are at the assistance
voltage VSUS. The voltage of the node NG is ELVDD+VTH by the
diode-connected driving transistor TD, and the voltage of the node
ND is the assistance voltage VSUS such that the voltage
ELVDD+VTH-VSUS is stored to the compensation capacitor CTH.
[0138] The scan period 3 and the light emitting period 4 are
currently or simultaneously processed after the compensation period
2. The driving current following the data signal programmed to the
pixel PX during the scan period 3 of the previous N-th frame of the
(N+1)-th frame is generated such that the organic light emitting
diode (OLED) emits the light and a plurality of data signals
data[1]-data[m] of the (N+1)-th frame are sequentially programmed
to a plurality of pixels PX. The data signals data[1]-data[m]
transmitted at the (N+1)-th frame are stored to the capacitor
CB.
[0139] After the compensation period 2 is finished, the driving
voltage ELVSS is decreased from the high level 10V to the low level
0V, the second operation control signal MB is changed from the low
level to the high level, and the first operation control signal MA
is changed from the high level to the low level.
[0140] During the scan period 3 and the light emitting period 4 of
the (N+1)-th frame, the second operation control signal MB is at
the high level turning off the second operation control transistor
TMB such that the scan operation in which the data signals
data[1]-data[m] of the (N+1)-th frame are programmed to the storage
capacitor CB is executed. Also, the first operation control signal
MA is at the low level turning on the first operation control
transistor TMA such that the driving transistor TD controls the
driving current according to the data signal stored to the storage
capacitor CA, and the light emitting operation in which the organic
light emitting diode (OLED) emits the light by the driving current
is executed.
[0141] Firstly, the light emitting operation of the (N+1)-th frame
is described. The first operation control signal MA is the low
level such that the first operation control transistor TMA is
turned on and the node ND is connected to the storage capacitor CA.
The storage capacitor CA is stored with the data signal of the
previous N-th frame.
[0142] The data signal stored to the storage capacitor CA is
applied to the node ND by the turn-on of the first operation
control transistor TMA. Like the above Equation 1, the voltage VDT
of the node ND is equal to a*Vdata. Here, a is equal to CB/CB+CX,
and Vdata is the voltage stored to the capacitor CA according to
the data signal of the previous N-th frame. Also, the voltage of
the gate electrode NG is changed to the voltage ELVDD+VTH-VSUS+VDT
according to the voltage change VDT-VSUS of the node ND. The
driving current IOLED supplied to the organic light emitting diode
OLED through the driving transistor VD during the light emitting
period 4 may be represented as Equation 2.
[0143] Next, the scan period 3 is described.
[0144] The capacitor CB blocked from the node ND by the second
operation control signal MB is programmed with the data signal of
the (N+1)-th frame during the scan period 3. A plurality of second
scan signals SB[1]-SB[m] sequentially become the low level pulse
signal of the enable level during the scan period 3. Thus, the
second switching transistor TSB of each of a plurality of pixels
connected to the scan line supplied with the second scan signals
SB[1]-SB[m] of the low level pulse is turned on, and the
corresponding data signal of a plurality of data signals
data[1]-data[m] is stored to the capacitor CB through the turned-on
second switching transistor TSB.
[0145] This operation is repeated, and thereby the scan period 3
and the light emitting period 4 are concurrently or simultaneously
executed.
[0146] The concurrent or simultaneous light emitting driving method
according to an exemplary embodiment of the present invention is
further appropriate to display a stereoscopic image compared with a
conventional art.
[0147] FIG. 7 shows a case that a stereoscopic image is displayed
according to a concurrent or simultaneous light emitting driving
method according to an exemplary embodiment of the present
invention.
[0148] The display device displays a left-eye image and a right-eye
image to realize the stereoscopic image. There is a method using
shutter glasses among methods of displaying the left-eye image and
the right-eye image. The left eye lens of the shutter glasses is
opened during a period that the left-eye image is displayed and the
right eye lens is closed during this period. The right eye lens of
the shutter glasses is opened during the period that the right-eye
image is displayed and the left eye lens is closed during this
period.
[0149] FIG. 7 shows a method that the display device displays the
left-eye image and the right-eye image according to the shutter
glasses method. As shown in FIG. 7, each frame includes the reset
period 1, the compensation period 2, the scan period 3, and the
light emitting period 4.
[0150] In FIG. 7, the frame in which a plurality of data signals
(hereinafter referred to as left eye image data signals)
representing the left-eye image are respectively programmed to a
plurality of pixels is indicated by a reference numeral "L", and
the frame in which a plurality of data signals (hereinafter
referred to as right eye image data signals) representing the
right-eye image are respectively programmed to a plurality of
pixels is indicated by a reference numeral "R".
[0151] The waveform of the driving voltage, the scan signal, the
compensation control signal, and the operation control signal of
the reset period 1, the compensation period 2, the scan period 3,
and the light emitting period 4 is the same as the waveform shown
in FIG. 6. The description for each period is omitted.
[0152] The left eye image data signal of the N_L frame is
transmitted to a plurality of pixels during the scan period 3 of
the period T21. During the scan period 3, the left eye image data
signals corresponding to the plurality of pixels PX are programmed.
At this time, a plurality of pixels emit the light according to the
right eye image data signals programmed at the scan period 3 of the
N-1_R frame during the light emitting period 4 of the period
T21.
[0153] The right eye image data signal of the N_R frame is
transmitted to a plurality of pixels at the scan period 3 of the
period T22.
[0154] The right eye image data signal respectively corresponding
to the plurality of pixels PX is programmed during the scan period
3. At this time, a plurality of pixels emit the light according to
the left eye image data signal programmed at the scan period 3 of
the N_L frame during the light emitting period 4 of the period
T22.
[0155] The left eye image data signal of the N+1_L frame is
transmitted to a plurality of pixels at the scan period 3 of the
period T23. The eye image data signal respectively corresponding to
a plurality of pixels PX is programmed during the scan period 3. At
this time, a plurality of pixels emit the light according to the
right eye image data signal programmed at the scan period 3 of the
N_R frame during the light emitting period 4 of the period T23.
[0156] The right eye image data signal of the N+1_R frame is
transmitted to a plurality of pixels at the scan period 3 of the
period T24. The right eye image data signal respectively
corresponding to a plurality of pixels PX is programmed during the
scan period 3. Here, a plurality of pixels emit the light according
to the left eye image data signal programmed in the scan period 3
of the N+1_L frame during the light emitting period 4 of the period
T24.
[0157] By this method, the light due to the right-eye image is
concurrently or simultaneously emitted during the period that the
left-eye image is programmed, and the light due to the left-eye
image is concurrently or simultaneously emitted during the period
that the right-eye image is programmed. Thus, a sufficient light
emitting period may be obtained, and thereby the image quality of
the stereoscopic image is improved.
[0158] The scan period 3 and the light emitting period 4 are
included in the same period such that the interval T31 between the
light emitting period 4 of each frame may be set up regardless of
the scan period. Here, the interval between the light emitting
period 4 may be set up as an interval that is desired in
consideration of the response speed of the liquid crystal of the
shutter glasses.
[0159] In a conventional case in which the scan period 3 and the
light emitting period 4 are not included in the same period, the
light emitting period 4 is disposed after the scan period 3 such
that the temporal margin at which the light emitting period 4 may
be set up among the period of one frame is small. According to an
exemplary embodiment of the present invention, the light emitting
period 4 may be set up in the period except for the reset period
and the compensation period among the period of one frame, or in
the period except for the initialization period, reset period, and
compensation period of one frame. Accordingly, the temporal margin
that is capable of setting up the light emitting period 4 is
increased compared with the conventional case, and thereby the
interval between the light emitting periods 4 may be set up when
considering the liquid crystal response speed of the shutter
glasses.
[0160] For example, the interval T31 between the light emitting
periods 4 may be set up when considering the time that the right
eye lens (or the left eye lens) of the shutter glasses is
completely opened from the view point that the light emitting of
the left-eye image (or the right-eye image) is finished.
[0161] Next, various pixel structures applied with the concurrent
or simultaneous light emitting method according to an exemplary
embodiment of the present invention will be described with
reference to FIGS. 8 and 9.
[0162] FIG. 8 is a view of another pixel structure according to an
exemplary embodiment of the present invention.
[0163] A pixel PX' shown in FIG. 8 further includes a reference
voltage compared with the pixel PX shown in FIG. 5. The storage
capacitor CA and the storage capacitor CB are connected to the
reference voltage VREF instead of the driving voltage ELVDD.
[0164] The scan period 3 and the light emitting period 4 are
concurrently or simultaneously generated such that the voltage drop
IR-DROP of the driving voltage ELVDD may be influenced by the data
writing of the scan period 3 during the light emitting period
4.
[0165] For example, during the period that the data signal data[j]
is programmed to the pixel PX' such that the voltage according to
the data signal data[j] is stored to the storage capacitor CA, if
the driving voltage ELVDD is decreased to the voltage drop, the
voltage stored to the storage capacitor CA is decreased. To prevent
this, the reference voltage VREF that is different from the driving
voltage ELVDD may be used.
[0166] The storage capacitor CA includes one electrode connected to
both the first switching transistor TSA and the first operation
control transistor TMB, and the other electrode connected to the
reference voltage VREF.
[0167] The storage capacitor CB includes one electrode connected to
both the second switching transistor TSB and the second operation
control transistor TMB, and the other electrode connected to the
reference voltage VREF.
[0168] FIG. 9 is a view of another pixel structure according to an
exemplary embodiment of the present invention.
[0169] Compared with the pixel PX shown in FIG. 5, in the pixel
PX'' shown in FIG. 9, the storage capacitor CA and the storage
capacitor CB are respectively connected to the driving voltage
ELVDD_A and the driving voltage ELVDD_B, and the driving transistor
TD is alternately connected to the driving voltage ELVDD_A and the
driving voltage ELVDD_B through the first light emitting transistor
ETA and the second light emitting transistor ETB. The driving
voltage ELVDD_A and the driving voltage ELVDD_B are the voltages
having the same waveform.
[0170] The storage capacitor CA includes one electrode connected to
both the first switching transistor TSA and the first operation
control transistor TMA, and the other electrode connected to the
driving voltage ELVDD_A. The storage capacitor CB includes one
electrode connected to both the second switching transistor TSB and
the second operation control transistor TMB, and the other
electrode connected to the driving voltage ELVDD_B.
[0171] The first light emitting transistor ETA is connected between
the driving voltage ELVDD_A and the driving transistor TD, and the
on/off thereof is controlled by the first operation control signal
MA. The first light emitting transistor ETA includes the gate
electrode input with the first operation control signal MA, the
source electrode connected to the driving voltage ELVDD_A, and the
drain electrode connected to the source electrode of the driving
transistor TD.
[0172] The second light emitting transistor ETB is connected
between the driving voltage ELVDD_B and the driving transistor TD,
and the on/off thereof is controlled by the second operation
control signal MB. The second light emitting transistor ETB
includes the gate electrode input with the second operation control
signal MB, the source electrode connected to the driving voltage
ELVDD_B, and the drain electrode connected to the source electrode
of the drain driving transistor TD.
[0173] If the first light emitting transistor ETA is turned on by
the first operation control signal MA, then the driving transistor
TD is connected to the driving voltage ELVDD_A. Here, the driving
transistor TD generates the driving current according to the
voltage difference between the driving voltage ELVDD_A and the gate
electrode during the light emitting period 4.
[0174] If the second light emitting transistor ETB is turned on by
the second operation control signal MB, then the driving transistor
TD is connected to the driving voltage ELVDD_B. Here, the driving
transistor TD generates the driving current according to the
voltage difference between the driving voltage ELVDD_B and the gate
electrode during the light emitting period 4.
[0175] As described above, using two driving voltages ELVDD_A and
ELVDD_B obtains the same effect as using the reference voltage
VREF. That is, the driving voltage connected to the driving
transistor TD and the driving voltage connected to the capacitor to
which the data writing is executed among the capacitor CA and the
capacitor CB, are different from each other during the period that
the organic light emitting diode (OLED) emits the light.
[0176] For example, during the period that the driving transistor
TD is connected to the driving voltage ELVDD_B and the driving
current is supplied to the organic light emitting diode (OLED), the
voltage according to the data signal is stored to the capacitor CA.
Here, the driving voltage ELVDD_A is connected to the capacitor CA.
As described above, the driving voltage for the light emitting
operation and the driving voltage for the data writing operation
are divided such that the voltage drop IR-drop by the light
emitting is not generated among the data writing operation, thereby
obtaining luminance uniformity of the screen.
[0177] Next, a constitution of a display device according to an
exemplary embodiment of the present invention will be described
with reference to FIG. 10. FIG. 10 is a view of a display device
according to an exemplary embodiment of the present invention.
[0178] As shown in FIG. 10, the display device 10 includes an image
processing unit 700, a timing controller 200, a data driver 300, a
scan driver 400, a power source controller 500, a compensation
control signal unit 600, and a display unit 100.
[0179] The image processing unit 700 generates a video signal ImS
and a synchronization signal from an input signal InS. The
synchronization signal includes a horizontal synchronization signal
Hsync, a vertical synchronization signal Vsync, and a main clock
signal CLK.
[0180] The image processing unit 700 divides the left-eye image
signal representing the left eye picture and the right eye video
signal representing the right eye picture as the frame unit when
the signal (hereinafter, image source signal) representing the
image included in the input signal InS is the signal representing
the stereoscopic image. The image processing unit 700 arranges the
left-eye image signal and the right eye image signal according to
the vertical synchronization and the horizontal synchronization to
generate the video signal ImS.
[0181] When the image source signal is the signal representing the
plane image, the image processing unit 700 divides the image source
signal as the frame unit and arranges the image source signal
according to the vertical synchronization and the horizontal
synchronization to generate the video signal ImS.
[0182] The main clock signal CLK may be a clock signal having a
basic frequency included in the image source signal, or may be one
of clock signals appropriately generated according to the necessity
of the image processing unit 700.
[0183] The timing controller 200 generates first to fourth driving
control signals CONT1-CONT4 and the image data signal ImD according
to the video signal ImS, the vertical synchronization signal Vsync,
the horizontal synchronization signal Hsync, and the main clock
signal CLK.
[0184] The timing controller 200 divides the video signal ImS as
the frame unit according to the vertical synchronization signal
Vsync and divides the video signal ImS as the scan line unit
according to the horizontal synchronization signal Hsync to
generate the image data signal ImD and transmit it to the data
driver 300 along with the first driving control signal CONT1.
[0185] The data driver 300 samples and holds the image data signal
ImD input according to the first driving control signal CONT1, and
respectively transmits a plurality of data signals data[1]-data[m]
to a plurality of data lines.
[0186] The scan driver 400 generates a plurality of first scan
signals SA[1]-SA[n], a plurality of second scan signals
SB[1]-SB[n], the first operation control signal MA, and the second
operation control signal MB according to the second driving control
signal CONT2, and transmits them to the corresponding scan line
during the initialization period INIT, the reset period 1, the
compensation period 2, the scan period 3, and the light emitting
period 4 of each frame.
[0187] The power source controller 500 determines the level of the
driving voltages ELVDD and ELVSS during the initialization period
INIT, the reset period 1, the compensation period 2, the scan
period 3, and the light emitting period 4 according to the third
driving control signal CONT3, and supplies them to the power line.
When applying the pixel structure according to FIG. 9, two driving
voltages ELVDD_A and ELVDD_B are generated from the power source
controller 500 and are supplied to the display unit 100.
[0188] The compensation control signal unit 600 determines the
level of the compensation control signal GC during the
initialization period INIT, the reset period 1, the compensation
period 2, the scan period 3, and the light emitting period 4
according to the fourth driving control signal CONT4 and supplies
them to the control signal line.
[0189] The display unit 100 was described above with reference to
FIG. 4.
[0190] In view of the foregoing, an embodiment of the present
invention provides a display device including a pixel including an
organic light emitting diode (OLED), a driving transistor connected
to the driving voltage and supplying a driving current to the
organic light emitting diode (OLED), a compensation capacitor
connected to the gate electrode of the driving transistor, and a
first storage capacitor and a second storage capacitor electrically
connected to or blocked from the compensation capacitor, and a
driving method thereof. In one embodiment, an anode voltage of the
organic light emitting diode (OLED) is discharged to be reset, and
a threshold voltage of the driving transistor is stored to the
compensation capacitor. The data voltage is stored to the first
storage capacitor according to the corresponding data signal, and
the organic light emitting diode (OLED) emits light according to
the driving current flowing to the driving transistor by the data
voltage stored to the second storage capacitor. Here, the organic
light emitting diode (OLED) of each of a plurality of pixels emits
the light by the corresponding driving current during the same
light emitting period. In addition, a step that the data voltage is
stored and a step that the organic light emitting diode (OLED)
emits the light are temporally overlapped.
[0191] While this invention has been described in connection with
what is presently considered to be practical exemplary embodiments,
it is to be understood that the invention is not limited to the
disclosed embodiments, but, on the contrary, is intended to cover
various modifications and equivalent arrangements included within
the spirit and scope of the appended claims.
DESCRIPTION OF SYMBOLS
[0192] reset period 1, compensation period 2, scan period 3, light
emitting period 4
[0193] first scan lines SA1-SAn, second scan lines SB1-SBn
[0194] data lines data1-datam, first voltage line 701, second
voltage line 702
[0195] compensation control line 703, first operation control line
704, second operation control line 705
[0196] driving transistor TD, first switching transistor TSA
[0197] second switching transistor TSB, first operation control
transistor TMA
[0198] second operation control transistor TMB, compensation
transistor TGC
[0199] storage capacitor CA, CB, compensation capacitor CTH,
organic light emitting diode OLED
[0200] driving voltage ELVDD, ELVSS, ELVDD_A, ELVDD_B, pixel PX,
PX', PX''
[0201] image processing unit 700, timing controller 200, data
driver 300
[0202] scan driver 400, power source controller 500, compensation
control signal unit 600, display unit 100
* * * * *