(19) United States
`(12) Patent Application Publication (10) Pub. No.: US 2005/0116902 A1
`Miyzawa
`(43) Pub. Date:
`Jun. 2, 2005
`
`US 2005O116902A1
`
`(54) DISPLAY APPARATUS AND METHOD OF
`DRIVING THE SAME
`(75) Inventor: Takao Miyzawa, Nagano-ken (JP)
`Correspondence Address:
`OLIFF & BERRIDGE, PLC
`P.O. BOX 19928
`ALEXANDRIA, VA 22320 (US)
`(73) Assignee: SEIKO EPSON CORPORATION,
`Tokyo (JP)
`(21) Appl. No.:
`10/936,649
`(22) Filed:
`Sep. 9, 2004
`(30)
`Foreign Application Priority Data
`
`Nov. 28, 2003 (JP)...................................... 2003-399339
`
`Publication Classification
`
`G09G 3/30
`51) Int. C.7
`; G09G 3/36
`Int. Cl. ...............................
`1)
`(52) U.S. Cl. ................................................................ 345/76
`(57)
`ABSTRACT
`To provide a technology for preventing effect of precharging
`from becoming nonuniform when the threshold Voltage of a
`driving transistor included in a current drive type pixel
`circuit is nonuniform. In the technology, before Setting the
`internal State of each of current drive type pixel circuits,
`provided to corresponded to interSections of a plurality of
`data lines and a plurality of Scanning lines, in accordance
`with light emission grayScales, precharge Voltages as Volt
`ages to be applied to the data lines are specified. A prede
`termined current is Supplied to the current drive type pixel
`circuits via the data lines. A precharge Voltage is specified in
`accordance with Voltages appearing in the data lines after the
`predetermined current is Supplied.
`
`
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`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 001
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 1 of 14
`
`US 2005/0116902 A1
`
`FIG. 1
`
`300
`
`
`
`200
`
`
`
`
`
`
`
`
`
`DISPLAY MATRIX SECTION
`(DISPLAY REGION)
`
`DATALINE DRIVER
`
`400
`
`CONTROL UNIT
`
`1OO
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 002
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 2 of 14
`
`US 2005/0116902 A1
`
`FIG. 2
`
`
`
`1.
`L
`2
`1.
`?
`L
`2
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`CD
`2
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`a.
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`CW)
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 003
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 3 of 14
`
`US 2005/0116902 A1
`
`FIG. 3
`
`DISPLAY
`MATRIX .
`SECTION
`
`
`
`
`
`
`
`
`
`PROGRAMMING CURREN
`SUPPLYING MEANS
`
`PRECHARGE
`VOLTAGE
`GENERATING MEANS
`
`
`
`VOLTAGE
`MEASURING MEANS
`
`
`
`CONTROLLING
`MEANS
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 004
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 4 of 14
`
`US 2005/0116902 A1
`
`
`
`099099
`
`079 Lu? ES
`
`UUX
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 005
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 5 of 14
`
`US 2005/0116902 A1
`
`FIG. 5
`
`S1 OPEN
`
`CLOSED
`
`OPEN
`
`S2 OPEN
`
`S3 OPEN
`
`VOLTAGE
`
`
`
`CLOSED
`
`OPEN
`
`FIG. 6
`
`in2
`in 1
`
`TIME
`
`Out:3
`
`LOW
`
`HIGH
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 006
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 6 of 14
`
`US 2005/0116902 A1
`
`FIG. 7
`
`S1 OPEN
`
`CLOSED
`
`OPEN
`
`S2 OPEN
`
`CLOSED
`
`OPEN
`
`.
`
`S3 OPEN
`
`FIG. 8
`
`200
`
`41 Oe
`
`RSE
`SECTION
`
`
`
`TEMPERATURE
`DETECTING MEANS
`
`
`
`
`
`
`
`
`
`
`
`
`
`PROGRAMMING CURRENT
`SUPPLYING MEANS
`
`PRECHARGE
`VOLTAGE
`GENERATING MEANS
`
`VOLTAGE
`MEASURING MEANS
`
`
`
`CONTROLLING
`MEANS
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 007
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 7 of 14
`
`US 2005/0116902 A1
`
`FIG. 9
`
`Vth
`
`
`
`T (TEMPERATURE)
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 008
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 8 of 14
`
`US 2005/0116902 A1
`
`FIG 10
`
`a do to des as a m ap up a m us as
`
`p
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`b
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`COLUMN d
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`COLUMN e
`
`DRIVERC
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 009
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 9 of 14
`
`US 2005/0116902 A1
`
`FIG. 11
`
`
`
`
`
`
`
`
`
`DISPLAY MATRIX SECTION
`(DISPLAY REGION)
`
`
`
`CALIBRATION REGION
`
`DRIVERIC
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 010
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 10 of 14
`
`US 2005/0116902 A1
`
`FIG. 12
`
`
`
`PXEL
`CIRCUIT
`
`PIXEL
`CIRCUIT
`
`4.
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`2
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`CA)
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 011
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 11 of 14
`
`US 2005/0116902 A1
`
`FIG. 13
`
`
`
`1.
`2
`1
`O
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`2
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`CD
`4.
`2
`Z
`ad
`Cd
`CfO
`
`130
`
`DATA LINE DRIVER
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 012
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 12 of 14
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`US 2005/0116902 A1
`
`FIG. 14
`
`
`
`1 1 O
`
`e
`
`is
`
`a
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`a
`
`the so
`
`as was a
`
`a
`
`up
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 013
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 13 of 14
`
`US 2005/0116902 A1
`
`FIG. 15
`
`TC
`
`Tpr
`
`Tel
`
`V - - -
`V- l
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 014
`
`

`

`Patent Application Publication Jun. 2, 2005 Sheet 14 of 14
`
`US 2005/0116902 A1
`
`
`
`
`
`(LNEHHnO TWWII dO) \doA ? dA
`
`
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 015
`
`

`

`US 2005/0116902 A1
`
`Jun. 2, 2005
`
`DISPLAY APPARATUS AND METHOD OF
`DRIVING THE SAME
`
`BACKGROUND OF THE INVENTION
`0001) 1. Field of Invention
`0002 The present invention relates to technology of
`Setting the internal State of a current drive type pixel circuit
`corresponding to light emission grayScales for the current
`drive type pixel circuit at a high Speed.
`0003 2. Description of Related Art
`0004.
`In recent years, an electro-optical apparatus using
`an organic electroluminescent (EL) element has been pro
`gressively developed. The organic EL element is a Self
`luminous element and does not require a backlight. Accord
`ingly, a display apparatus using the organic EL element is
`expected to achieve low power consumption, a wide View
`ing angle, and a high contrast ratio. In this Specification, the
`term "electro-optical apparatus' means an apparatus that
`converts electrical Signals into light. The electro-optical
`apparatus normally converts electrical signals representing
`an image into light representing the image and is particularly
`Suitable to implementation of a display apparatus.
`0005 FIG. 13 is a block diagram of a conventional
`display apparatus using an organic EL element. The con
`ventional display apparatus includes a display matrix Section
`(hereinafter, referred to as a "display region”) 120, a scan
`ning line driver 130, and a data line driver 140. The display
`matrix section 120 includes a plurality of pixel circuits 110
`arranged in a matrix. Each pixel circuit 110 includes an
`organic EL element 220. Each of the pixel circuits 110
`arranged in a matrix is connected to one of a plurality of data
`lines Xm (where m=1,2,..., and M) extending in a column
`direction and is connected to one of a plurality of Scanning
`lines Yin (where n=1, 2, .
`. . , and N) extending in a row
`direction.
`0006 FIG. 14 is a circuit diagram illustrating an example
`of the pixel circuit 110. The pixel circuit 110 is located at an
`interSection of an m-th data line Xm and an n-th Scanning
`line Yn. The Scanning line Yn includes two Sub-Scanning
`lines V1 and V2. The pixel circuit 110 is a current drive type
`circuit that controls a light emission grayScale of the organic
`EL element 220 corresponding to a current flowing in the
`data line Xm. In detail, the pixel circuit 110 further includes
`four transistors 211 to 214 and a storage capacitor 230 in
`addition to the organic EL element 220. The Storage capaci
`tor 230 Stores charges corresponding to data Signals received
`via the data line Xm to control the light emission of the
`organic EL element 220 using the Stored charges. In other
`words, the Storage capacitor 230 Stores a Voltage corre
`sponding to the current flowing in the data line Xm. The first
`to third transistors 211 to 213 are n-channel field effect
`transistor (FET) and the fourth transistor 214 is a p-channel
`FET. The organic EL element 220 is a current drive type
`light emission element like a photodiode and is thus marked
`with a symbol of a diode in the drawings.
`0007. The source of the first transistor 211 is connected
`the drain of the second transistor 212, the drain of the third
`transistor 213, and the drain of the fourth transistor 214. The
`drain of the first transistor 211 is connected to the gate of the
`fourth transistor 214. The storage capacitor 230 is connected
`
`between a Source and the gate of the fourth transistor 214.
`The Source of the fourth transistor 214 is connected to a
`power Supply Voltage Vdd.
`0008. The source of the second transistor 212 is con
`nected to the data line driver 140 via the data line Xm. The
`organic EL element 220 is connected between the Source of
`the third transistor 213 and a ground Voltage. The gate of the
`first transistor 211 and the gate of the second transistor 212
`are commonly connected to the first Sub-Scanning line V1.
`The gate of the third transistor 213 is connected to the
`Second Sub-Scanning line V2.
`0009. The first and second transistors 211 and 212 are
`Switching transistors used to accumulate charges in the
`storage capacitor 230. The third transistor 213 is a Switching
`transistor that is in an ON State during the light emission of
`the organic EL element 220. The fourth transistor 214 is a
`driving transistor that controls a value of current flowing in
`the organic EL element 220. The current value in the fourth
`transistor 214 is controlled by the amount of charges Stored
`(i.e., accumulated) in the storage capacitor 230.
`0010 FIG. 15 is a timing chart illustrating the normal
`operation of the pixel circuit 110. In FIG. 15, a voltage in
`the first Sub-Scanning line V1 (hereinafter, referred to as a
`first gate signal V1), a voltage in the Second Sub-Scanning
`line V2 (hereinafter, referred to as a Second gate signal V2),
`a current in the data line Xm (hereinafter, referred to as data
`Signals Iout), and a current IEL in the organic EL element
`220 are represented.
`0011. A driving period Tc is divided into a programming
`period Tpr and a light emission period Tel. The driving
`period Tc is a period of time taken to update a light emission
`grayScale of each of the organic EL elements 220 within the
`display matrix section 120 one time. The driving period Tc
`is referred to as a frame period. A grayScale update is
`performed in a group of pixel circuits in a Single row at one
`time and is Sequentially performed in N groups of pixel
`circuits in the N rows during the driving period Tc. For
`example, when the grayScale update is performed on all of
`the pixel circuits 110 at 30 Hz, the driving period Tc is about
`33 ms.
`0012. The programming period Tpr is a period of time
`while the light emission grayScales of each organic EL
`element 220 is set in a corresponding pixel circuit 110. Here,
`programming indicates the operation of Setting the light
`emission grayScale in the pixel circuit 110. For example,
`when the driving period Tc is about 33 ms and the total
`number N of the Scanning lines Yn is 480, the programming
`period Tpr is less than about 69 us.
`0013 During the programming period Tpr, the second
`gate signal V2 is set to a “low” level and the third transistor
`213 remains turned off. Next, a current Im corresponding to
`the light emission grayScale flows in the data line Xm, the
`first gate signal V1 is set to a “high level, and the first and
`Second transistorS 211 and 212 are turned on. Here, the data
`line driver 140 functions as a constant current source that
`provides the current Im according to the light emission
`grayScale.
`0014 Charges corresponding to the current Im flowing in
`the fourth transistor 214 (i.e., the driving transistor) are
`Stored in the Storage capacitor 230. AS a result, a Voltage
`Stored in the Storage capacitor 230 is applied between the
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 016
`
`

`

`US 2005/0116902 A1
`
`Jun. 2, 2005
`
`Source and the gate of the fourth transistor 214. Hereinafter,
`the current Im of data Signals used in the programming is
`referred to as a “programming current Im”. After the pro
`gramming is finished, the Scanning line driver 130 Sets the
`first gate signal V1 to the “low” level and turns off the first
`and second transistors 211 and 212. The data line driver 140
`Stops outputting the data Signals Iout.
`0.015. During the light emission period Tel, while the first
`gate signal V1 remains at the “low” level, the first and
`Second transistorS 211 and 212 remain turned off, the Second
`gate signal V2 is set to the “high level and the third
`transistor 213 is turned on. Since the Voltage corresponding
`to the programming current Im has been Stored in the Storage
`capacitor 230, almost the same current as the programming
`current Im flows in the fourth transistor 214. Therefore,
`almost the same current as the programming current Im
`flows in the organic EL element 220. The organic EL
`element 220 emits light with a grayScale corresponding to
`the current value Im.
`0016. In the display apparatus illustrated in FIG. 13, the
`light emission of the organic EL element 220 included in
`each pixel circuit 110 is controlled according to the above
`described Sequence of operation. However, when a large
`display panel is manufactured using the above-described
`Structure, the capacitance (Cd) of each data line increases
`and a large amount of time is required to drive the data lines.
`To solve these problems, “Patent Document 1” discloses
`technology for accelerating charge or discharge by writing
`the power Supply Voltage Vdd in the data line Xm connected
`to the pixel circuit 110 before programming a current
`corresponding to the light emission grayScale in the pixel
`circuit 110, that is, before Setting an internal Sate of the pixel
`circuit 110. Hereinafter, the operation of programming a
`predetermined Voltage in a data line connected to a current
`drive type pixel circuit before the internal State of the pixel
`circuit is Set corresponding to the light emission grayScale of
`the pixel circuit, thereby accelerating the charge or dis
`charge, which is referred to as “precharging”. A voltage
`written in the data line by the precharging is referred to as
`a “precharge Voltage'.
`0017
`Patent Document 1 Pamphlet of PCT Publication
`WO 01/006484
`
`SUMMARY OF THE INVENTION
`0.018 When it is assumed that a driving transistor in each
`pixel circuit 110 operates in a Saturation region, a current
`“Ids” flowing between a drain and the source of the driving
`transistor (i.e., a current flowing in the organic EL element
`220) is given by the following equation:
`Expression 1
`Ids=(upre:Wp)/(2 toxlp)(Vgs-Vth) ,
`0.019 where Vgs denotes a voltage flowing between the
`gate and the Source, Vth denotes a threshold Voltage, Wp
`denotes a channel width, Lp denotes a channel length, up
`denotes a hole mobility, tox denotes the thickness of a gate
`insulation layer, and e denotes a dielectric constant of a gate
`insulation material.
`0020. When the threshold voltage Vth of the driving
`transistor is different from the pixel circuits 110, even
`though the organic EL elements 220 emit light with the same
`grayScale, a Voltage to be written in the Storage capacitor
`230 is different from the pixel circuits 110. When a voltage
`
`to be written in the storage capacitor 230 is different from
`the pixel circuits 110, an optimal precharge Voltage to be
`applied to a data line before the Voltage is written in the
`Storage capacitor 230 is also different from the pixel circuits
`110. To solve this problem, the technology disclosed in
`Patent Document 1 always uses the power Supply Voltage
`Vdd as the precharge Voltage. Accordingly, a Satisfactory
`effect by the precharging cannot be obtained in this tech
`nology disclosed in Patent document 1. In detail, referring to
`FIG. 16, when a precharge voltage Vp is much higher or
`lower than an optimal voltage Vopt, a Voltage Stored in the
`Storage capacitor 230 (i.e., the gate voltage of the driving
`transistor) is non-uniform even after the programming
`period Tpr lapses. When the gate Voltage of the driving
`transistor is not uniform, a current flowing in the organic EL
`element 220 becomes nonuniform and the light emission
`grayScale of each organic EL element 220 becomes nonuni
`form. In other words, the quality of a displayed image may
`deteriorate. The deterioration of the quality of a displayed
`image is particularly prominent when the organic EL ele
`ment 220 emits light with a low grayscale. When the organic
`EL element 220 emits light with the low grayScale, Since a
`current corresponding to the low grayScale is Small, it takes
`long to write a Voltage corresponding to the current in the
`Storage capacitor 230, and therefore, the programming of the
`Voltage may not be Satisfactorily performed during the
`programming period Tpr, which is referred to as “insufficient
`programming hereinafter.
`0021. In view of the foregoing, it is an object of the
`present invention to provide a technology for preventing
`effect of precharging from becoming nonuniform when the
`threshold Voltage of a driving transistor included in a current
`drive type pixel circuit is nonuniform.
`0022. To accomplish the above object, the present inven
`tion provides a display apparatus including a plurality of
`data lines, a plurality of Scanning lines, a plurality of current
`drive type pixels provided to corresponded to interSections
`of the plurality of data lines and the plurality of Scanning
`lines; Supplying means which Supplies a predetermined
`current via the plurality of data lines to the corresponding
`pixels, and Specifying means which Specifies precharge
`Voltages as Voltages to be applied to the data lines connected
`to the pixels before the internal State of the pixels corre
`sponding to light emission grayScales is Set, in accordance
`with Voltages appearing in the data lines after the Supplying
`means provides the predetermined current.
`0023. According to the display apparatus, the precharge
`Voltages are specified in accordance with the Voltages
`appearing in the data lines when the internal State of the
`pixels corresponding to the predetermined current is Set.
`That is, the precharge Voltages are Specified when the pixels
`are actually operated. Accordingly, if precharging is per
`formed using the thus specified precharge Voltages, a pre
`charging effect is uniform even when the threshold Voltage
`of a driving transistor included in each pixel is not uniform.
`0024.
`In a more preferred aspect, the display apparatus
`may further comprises Storage means which Stores the
`precharge Voltages Specified by the Specifying means So as
`to correspond to the pixels. In the aspect as described above,
`a precharge Voltage Specified for each pixel is Stored in the
`Storage means to corresponded to the pixel. Generally, in
`order to accurately specify an optimal precharge Voltage, a
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 017
`
`

`

`US 2005/0116902 A1
`
`Jun. 2, 2005
`
`Sufficiently long time for programming is required and is
`usually longer than the time required to display an image.
`However, according to the present invention, for example, in
`factories before forwarding products, a precharge Voltage
`may be specified only one time and Stored in the Storage
`means. Accordingly, compared to a case where a precharge
`Voltage is specified whenever an image is displayed, the time
`required to specify the precharge Voltage is reduced.
`0.025
`In a more preferred aspect, the display apparatus
`may further comprises measuring means which measures the
`Voltages appearing in the data lines after the Supplying
`means provides the predetermined current. The Specifying
`means Specifies the Voltages measured by the measuring
`means as the precharge Voltages. Since the Specified pre
`charge Voltages are the Voltages appearing in the data line
`when the pixels are actually driven, a precharging effect is
`uniform even when the threshold voltage of a driving
`transistor included in a pixel is not uniform.
`0026.
`In a more preferred aspect, the Supplying means
`Supplies the predetermined current to the pixels at least
`when electric power is applied to the display apparatus.
`Since the precharge Voltage for each pixel is specified when
`electric power is Supplied to the display apparatus, even
`when a driving transistor included in the pixel is degraded
`over time and has a threshold Voltage changed, the precharge
`Voltage is specified in accordance with the changed thresh
`old Voltage.
`0027. In a more preferred aspect, the predetermined cur
`rent Supplied to the pixels by the Supplying means corre
`sponds to a current when the pixels are caused to emit light
`with a low grayScale. Generally, a programming current
`corresponding to the low grayScale becomes Small, resulting
`in an insufficient programming problem. However, if pre
`charge Voltages are specified in accordance with to Voltages
`appearing in data lines when the internal State of pixels is Set
`using the current corresponding to the low grayScale, the
`insufficient programming problem can be avoided.
`0028. In a more preferred aspect, the display apparatus
`may further comprises a display region in which the plural
`ity of pixels is arranged in a matrix. The Supplying means
`Supplies the predetermined current to all the pixels arranged
`in the display region. The Specifying means Specifies the
`precharge Voltages for all the pixels. In above-described
`aspect, the precharge Voltages for all the pixels arranged in
`the display region are specified through the actual operation
`of each pixel. Accordingly, a precharging effect is uniform
`even when the threshold Voltage of a driving transistor
`included in the pixel is not uniform.
`0029. In a more preferred aspect, the display apparatus
`may further include a display region in which the plurality
`of pixels is arranged in a matrix. The Supplying means
`Supplies the predetermined current to pixels belonging to a
`row Selected from the display region. The Specifying means
`Specifies the precharge Voltages for the corresponding pixels
`Supplied with the predetermined current by the Supplying
`means and then Specifies the average of the precharge
`Voltages as the precharge Voltage for the pixels in the
`Selected row. In above-described aspect, the precharge Volt
`ages Specified for the pixels belonging to the Selected row
`are equalized in units of rows, and therefore, a calibration
`error is reduced.
`0.030. In a more preferred aspect, the display apparatus
`may further comprise a display region in which the plurality
`
`of pixels is arranged in a matrix. The Supplying means
`Supplies the predetermined current to pixels belonging to at
`least one row or column designated in advance in the display
`region. The Specifying means Specifies the precharge Volt
`ages for the corresponding pixels Supplied with the prede
`termined current and then based on the distribution of the
`Specified precharge Voltages, optimizes the precharge Volt
`ages for the corresponding pixels arranged in the display
`region. Here, the time required to specify the optimal
`precharge Voltages can be reduced compared to a case where
`precharge Voltages for all of the pixels are Specified by
`actually driving all of the pixels in the display region. In
`addition, the Storage capacity required for Storing the Speci
`fied precharge Voltages can be reduced.
`0031. In a more preferred aspect, the display apparatus
`may further comprise a display region in which the plurality
`of pixels is arranged in a matrix. The Supplying means
`Supplies the predetermined current to calibration pixels
`disposed outside the display region along Sides of the
`display region, and the Specifying means Specifies the pre
`charge Voltages for the corresponding calibration pixels and
`then based on the distribution of the Specified precharge
`Voltages, optimizes the precharge Voltages for the corre
`sponding pixels arranged in the display region. In the
`above-described aspect, Since the calibration pixels are
`disposed outside the display region along Sides of the
`display region, the Specification of optimal precharge Volt
`ages and actual image display can be simultaneously per
`formed without affecting the display quality of the display
`region.
`0032. In a more preferred aspect, the calibration pixels
`may be dummy pixels that do not comprise any light
`emission element. According to the above-described aspect,
`Since the dummy pixels do not emit light when they are used
`to specify the precharge Voltages, the display quality of the
`display region is much less affected.
`0033. In a more preferred aspect, the display apparatus
`may further comprise Switching means which Selects either
`a first data line or a Second data line for being connected to
`the Supplying means. The first data line is connected to the
`pixels arranged in the display region to display an image,
`and the Second data line is connected to the calibration
`pixels. The calibration pixels are disposed Such that the
`length of the second data line is smaller than that of the first
`data line. According to the above-described aspect, Since the
`calibration pixels are connected to data lines other than the
`data lines connected to the pixels for image display, the
`floating capacity of the data lines connected to the pixels for
`image display can be decreased, and therefore, the time
`required to specify a precharge Voltage can be reduced.
`0034.
`In a more preferred aspect, the display apparatus
`may further comprise temperature detecting means which
`detects the temperature of the pixels, where the Specifying
`means Specifies the precharge Voltages based on the Voltages
`appearing in the data lines and the temperature detected by
`the temperature detecting means. In the above-described
`aspect, even when the threshold Voltage of a driving tran
`Sistor included in a pixel changes due to an increase in the
`temperature of the driving transistor during image display,
`the precharge Voltage can be specified in accordance with
`the changed threshold Voltage at that time.
`0035) To solve the above object of the present invention,
`the present provides a method of driving a display apparatus.
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 018
`
`

`

`US 2005/0116902 A1
`
`Jun. 2, 2005
`
`The method comprises the Steps of a first Step of Supplying
`a predetermined current to a plurality of current drive type
`pixels provided to corresponded to interSections of a plu
`rality of data lines and a plurality of Scanning lines via the
`data lines, and a Second Step of Specifying precharge Volt
`ages as Voltages to be applied to the data lines connected to
`the pixels before the internal State of the pixels correspond
`ing to light emission grayScales is Set, in accordance with
`Voltages appearing in the data lines after the predetermined
`current is Supplied.
`0036). According to the driving method, even when the
`threshold Voltage of a driving transistor included in the pixel
`is not uniform, a precharge Voltage for each pixel is Specified
`when each pixel is actually driven. Accordingly, if precharg
`ing is performed using the thus specified precharge Voltage,
`a precharging effect can be uniform.
`0037. In a more preferred aspect, the first step may
`comprise Supplying the predetermined current to pixels
`belonging to at least one row or column designated in
`advance in a display region in which the plurality of pixels
`is arranged in a matrix. The Second step may comprise
`Specifying a plurality of the precharge Voltages for the
`corresponding pixels Supplied with the predetermined cur
`rent, and then based on the distribution of the specified
`precharge Voltages, optimizing the precharge Voltages for
`the corresponding pixels arranged in the display region.
`0.038
`Here, the time required to specify the optimal
`precharge Voltages can be reduced compared to a case where
`precharge Voltages for all of the pixels are Specified by
`actually driving all of the pixels in the display region. In
`addition, the Storage capacity required for Storing the Speci
`fied precharge Voltages can be reduced.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`0.039
`FIG. 1 is a block diagram of a display apparatus
`according to the present invention.
`0040 FIG. 2 is a block diagram illustrating the internal
`Structure of a display matrix Section and the internal Struc
`ture of a data line driver according to the present invention.
`0041
`FIG. 3 is a block diagram illustrating a fundamen
`tal structure of a single line driver 410 according to the
`present invention.
`0.042
`FIG. 4 is a detailed block diagram of the single line
`driver 410 according to the present invention.
`0.043
`FIG. 5 is a timing chart illustrating the operation of
`the Single line driver 410 according to the present invention.
`0044 FIG. 6 illustrates the relationship between input
`and output Signals of a comparator according to the present
`invention.
`004.5 FIG. 7 is a timing chart illustrating the operation)
`of the single line driver 410 according to the present
`invention.
`0.046
`FIG. 8 illustrates a single line driver according to
`Modification 1 of the present invention.
`0047 FIG. 9 is a view illustrating an example of a
`temperature-threshold Voltage characteristic of a driving
`transistor.
`
`0048 FIG. 10 is a view illustrating a method of speci
`fying a precharge Voltage according to Modification 2.
`0049 FIG. 11 is a view illustrating a method of speci
`fying a precharge Voltage according to Modification 3.
`0050 FIG. 12 is a view illustrating a display apparatus
`according to the Modification 3.
`0051 FIG. 13 is a block diagram of a conventional
`display apparatus using an organic electroluminescent (EL)
`element.
`0052 FIG. 14 is a circuit diagram illustrating an example
`of a pixel circuit 110 of a general display apparatus.
`0053 FIG. 15 is a timing chart illustrating the normal
`operation of the pixel circuit 110 of the general display
`apparatuS.
`FIG. 16 illustrates effects of different precharge
`0054)
`Voltages.
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS
`0055. Hereinafter, preferred embodiments of the present
`invention will be described in detail with reference to the
`accompanying drawings.
`0056 A. Structure
`0057 FIG. 1 is a schematic block diagram of a display
`apparatus according to an embodiment of the present inven
`tion. AS Shown in FIG. 1, the display apparatus includes a
`control unit 100, a display matrix section 200, a scanning
`line driver 300, and a data line driver 400. The control unit
`100 generates Scanning line driving Signals and data line
`driving Signals, which are used to perform a display on the
`display matrix Section 200, and Supplies the generated
`signals to the scanning line driver 300 and the data line
`driver 400, respectively.
`0058 FIG. 2 is a block diagram illustrating the internal
`structure of the display matrix section 200 and the internal
`structure of the data line driver 400. As shown in FIG. 2, the
`display matrix section 200 includes a plurality of pixel
`circuits 110 arranged in a matrix (refer to FIG. 14). Each of
`the pixel circuits 110 in a matrix is connected to one of a
`plurality of data lines Xm (where m=1 to M) extending in a
`column direction, and connected to one of a plurality of
`Scanning lines Yin (where n=1 to N) extending in a row
`direction. In the present Specification, the pixel circuits 110
`are referred to as unit circuits or pixels. In the embodiment
`of the present invention, the pixel circuits 110 arranged in
`the display matrix section 200 have the same structure as the
`pixel circuit 110 shown in FIG. 14. However, as far as the
`pixel circuits arranged in the display matrix Section 200 are
`current drive type pixel circuits, their circuit Structure may
`be changed. In addition, in the embodiment of the present
`invention, all of the transistors included in the pixel circuits
`110 are field effect transistors (FETs). However, some or all
`of the transistors may be replaced with bipolar transistors or
`other types of Switching devices. For example, Silicon-based
`transistors may be used as this kind of a transistor in addition
`to the thin film transistors (TFTS).
`0059) The control unit 100 shown in FIG. 1 converts
`display data (i.e., image data) representing a display State of
`the display matrix Section 200 into matrix data representing
`
`LG Display Co., Ltd.
`Exhibit 1005
`Page 019
`
`

`

`US 2005/0116902 A1
`
`Jun. 2, 2005
`
`the light emission grayScale of each of organic electrolumi
`nescent (EL) elements 220. The matrix data includes scan
`ning line driving Signals Sequentially Selecting a single
`group of pixel circuits 110 in a Single row and data line
`driving Signals indicating the level of data Signals Supplied
`to the o