# US 11,308,881 B2 · Display device and method for driving same

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- Number: US 11,308,881 B2
- Document ID: US11308881B2
- Status: Granted
- Kind: B2
- Application number: 17/277,267
- Filed: 2018-09-20
- Published: 2021-10-14
- Granted: 2022-04-19
- Earliest claimed: 2018-09-20
- Assignees: Sharp Kabushiki Kaisha
- Applicants: Sharp Kabushiki Kaisha
- Inventors: Tetsuya Ueno
- Web page: https://patentgrep.com/patent/US11308881B2

## CPC

- G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element
- G09G 3/2092: {Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto (suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165)}
- G09G 3/3266: Details of drivers for scan electrodes
- G09G 3/3291: in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
- G09G 2300/0819: used for counteracting undesired variations, e.g. feedback or autozeroing
- G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor
- G09G 2300/0861: with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
- G09G 2310/0251: Precharge or discharge of pixel before applying new pixel voltage
- G09G 2320/0223: Compensation for problems related to R-C delay and attenuation in electrodes of matrix panels, e.g. in gate electrodes or on-substrate video signal electrodes
- G09G 2320/0233: Improving the luminance or brightness uniformity across the screen
- G09G 2320/0285: using tables for spatial correction of display data
- G09G 2330/02: Details of power systems and of start or stop of display operation
- G09G 2330/028: Generation of voltages supplied to electrode drivers in a matrix display other than LCD
- G09G 2360/12: Frame memory handling
- G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data
- G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00)

## Abstract

The present application discloses a current-driven display device capable of preventing a decrease in display quality due to luminance gradient or the like caused by a voltage drop in a power supply line while preventing an increase in circuit and processing necessary for driving a pixel circuit. In an organic EL display device, at a connection point of a high-level power supply line ELVDD with a pixel circuit 15 (Pix(n,k)) (n=1 to N; k=1 to M) on each branch wire ELVk, a display control circuit calculates a voltage drop ΔVn=V0−Vn caused by a current flowing in the branch wire ELVk in a data write period for the pixel circuit Pix(n,k), corrects corresponding pixel data (pixel data for Pix(n,k)) dn in input image data based on the voltage drop ΔVn, and generates a driving image data signal Sdda to be given to a data-side drive circuit based on the corrected pixel data dcn.

## Claims

### Claim 1

A display device having a plurality of scanning signal lines extending in a row direction, a plurality of data signal lines extending in a column direction and intersecting the plurality of scanning signal lines, and a plurality of pixel circuits arranged in a matrix form along the plurality of scanning signal lines and the plurality of data signal lines, the display device comprising:
a power supply line including first and second power supply voltage lines;
an image data correction unit configured to generate driving image data by correcting input image data that represents an image to be displayed;
a data signal line drive circuit configured to drive the plurality of data signal lines based on the driving image data generated by the image data correction unit; and
a scanning signal line drive circuit configured to selectively drive the plurality of scanning signal lines,
wherein the first power supply voltage line includes a trunk wire, and a plurality of branch wires diverging from the trunk wire and arranged along the plurality of data signal lines, respectively,
each of the pixel circuits corresponds to any one of the plurality of scanning signal lines, corresponds to any one of the plurality of data signal lines, and corresponds to any one of the plurality of branch lines,
includes a display element driven by a current, a holding capacitor configured to hold a data voltage for controlling a drive current of the display element, and a drive transistor configured to control the drive current of the display element in accordance with the data voltage held in the holding capacitor, and is configured such that a voltage of a corresponding data signal line is written in the holding capacitor as a data voltage when a corresponding scanning signal line is selected,
in each of the pixel circuits,
a first conductive terminal of the drive transistor is connected to a branch wire corresponding to the each pixel circuit,
a second conductive terminal of the drive transistor is connected to the second power supply voltage line via the display element, and
a control terminal of the drive transistor is connected to the corresponding branch wire via the holding capacitor, and
the image data correction unit obtains an estimated value of a current that flows in a branch wire corresponding to any one of the plurality of pixel circuits when a data voltage is written in the any one pixel circuit, determines a voltage drop at a connection point between the branch wire and the any one pixel circuit based on the estimated value of the current, and corrects image data for the any one pixel circuit out of the input image data in accordance with the voltage drop, so as to generate image data corresponding to the data voltage to be written in the any one pixel circuit out of the driving image data, wherein the image data correction unit
sequentially receives the input image data for each frame,
acquires, as a present-frame current value, an estimated value of a current supplied from the power supply line to a preceding pixel circuit corresponding to any one of scanning signal lines selected before the scanning signal line corresponding to the any one pixel circuit in which the data voltage is to be written out of pixel circuits on one column connected to the branch wire corresponding to the any one pixel circuit in which the data voltage is to be written, based on the image data for the preceding pixel circuit out of the input image data of the present frame, and acquires, as an immediately-preceding-frame current value, an estimated value of a current supplied from the power supply line to a succeeding pixel circuit corresponding to any one of scanning signal lines selected after the scanning signal line corresponding to the any one pixel circuit in which the data voltage is to be written out of the pixel circuits on the one column based on the image data for the succeeding pixel circuit out of the input image data of the immediately preceding frame, and calculates the voltage drop based on the present-frame current value and the immediately-preceding-frame current value.

### Claim 2 (depends on 1)

The display device according to claim 1, wherein the image data correction unit
obtains an estimated value of a current supplied from the power supply line to a pixel circuit that is in an emission state and is connected to a branch wire corresponding to the any one pixel circuit in which the data voltage is to be written, except for the any one pixel circuit in which the data voltage is to be written, based on image data for said pixel circuit in the emission state, and
calculates the voltage drop at the connection point at a time of writing the data voltage in the any one pixel circuit based on the estimated value of the current.

### Claim 3 (depends on 2)

The display device according to claim 2, wherein each of the pixel circuits is configured such that when a scanning signal line corresponding to the each pixel circuit is selected, the each pixel circuit is in a non-emission state, and no current is supplied to the each pixel circuit from the power supply line.

### Claim 4 (depends on 3)

The display device according to claim 3, wherein each of the pixel circuits is configured such that even when a scanning signal line to be selected immediately before the selection of the scanning signal line corresponding to the each pixel circuit is selected, the each pixel circuit is in a non-emission state, and no current is supplied to the each pixel circuit from the power supply line.

### Claim 5 (depends on 1)

The display device according to claim 1, further comprising:
a plurality of emission control lines corresponding to the plurality of scanning signal lines, respectively; and
an emission control circuit configured to drive the plurality of emission control lines,
wherein each pixel circuit includes an emission control switching element provided in series with the display element in a path from the first power supply voltage line to the second power supply voltage line via the display element,
each emission control line is connected to a control terminal of the emission control switching element in a pixel circuit corresponding to the corresponding scanning signal line, and
the image data correction unit obtains an estimated value of a current supplied from the power supply line to a pixel circuit connected to an emission control line in an active state based on image data for the pixel circuit connected to the emission control line in the active state out of the pixel circuits connected to the branch wire corresponding to the any one pixel circuit in which the data voltage is to be written, the image data correction unit calculating the voltage drop at the connection point at a time of writing the data voltage in the any one pixel circuit based on the estimated value of the current.

### Claim 6 (depends on 1)

The display device according to claim 1, wherein
each of the pixel circuits is configured such that no current is supplied to the each pixel circuit from the power supply line when a scanning signal line corresponding to the each pixel circuit is selected, and
the image data correction unit calculates the voltage drop at a time of writing the data voltage in the any one pixel circuit on the assumption that no current is supplied from the power supply line to the any one pixel circuit in which the data voltage is written.

### Claim 7 (depends on 1)

The display device according to claim 1, further comprising a memory capable of storing respective current values of the plurality of pixel circuits and configured to store the present-frame current value for the preceding pixel circuit and store the immediately-preceding-frame current value for the succeeding pixel circuit, wherein each of the pixel circuits is configured such that no current is supplied from the power supply line to the each pixel circuit when a scanning signal line corresponding to the each pixel circuit is selected, the scanning signal line drive circuit selects the plurality of scanning signal lines in ascending order, the image data correction unit sequentially receives image data for each of the pixel circuits constituting the input image data of each frame in accordance with the selection of the plurality of scanning signal lines in ascending order, upon receipt of image data for a pixel circuit on an (i+1)th row and a jth column out of the input image data of the present frame, determines an estimated value of a current supplied from the power supply line to the pixel circuit on the (i+1)th row and the jth column as the present-frame current value based on the received image data, rewrites the current value of the pixel circuit on the (i+1)th row and the jth column stored in the memory to the present-frame current value of the pixel circuit, determines, from a voltage at a connection point between a pixel circuit on an ith row and the jth column and a branch wire on the jth column at a time of writing a data voltage in said pixel circuit, a voltage at a connection point between the pixel circuit on the (i+1)th row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit, based on the present-frame current value of the pixel circuit on the ith row and jth column and the immediately-preceding-frame current value stored in the memory as a current value of a pixel circuit on the jth column corresponding to any one of the scanning signal lines selected after a scanning signal line corresponding to the pixel circuit on the ith row and jth column, calculates the voltage drop based on the determined voltage, and corrects the received image data for the pixel circuit on the (i+1)th row and the jth column in accordance with the calculated voltage drop so as to generate image data corresponding to the data voltage to be written in the pixel circuit on the (i+1)th row and jth column of the driving image data.

### Claim 8 (depends on 7)

The display device according to claim 7, wherein
each of the pixel circuits is configured such that no current is supplied from the power supply line to the each pixel circuit even when the scanning signal line to be selected immediately before the selection of the scanning signal line corresponding to the each pixel circuit is selected, and
upon receipt of image data for the pixel circuit on the (i+1)th row and a jth column out of the input image data of the present frame, the image data correction unit determines, from a voltage at a connection point between the pixel circuit on the ith row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit, a voltage at a connection point between the pixel circuit on the (i+1)th row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit, based on the present-frame current value of the pixel circuit on the ith row and jth column and the immediately-preceding-frame current value stored in the memory as a current value of a pixel circuit on an (i+2)th row and the jth column, the image data correction unit calculating the voltage drop based on the determined voltage.

### Claim 9 (depends on 1)

The display device according to claim 1, wherein
the trunk wire is formed only in one picture-frame region along the plurality of scanning signal lines out of picture-frame regions adjacent to a display region in which the plurality of pixel circuits are arranged, and
the plurality of branch wires diverge from the trunk wire and are each supplied with a power supply voltage from the trunk wire.

### Claim 10

A method for diving a display device that includes a plurality of scanning signal lines extending in a row direction, a plurality of data signal lines extending in a column direction and intersecting the plurality of scanning signal lines, a power supply line including first and second power supply voltage lines, and a plurality of pixel circuits arranged in a matrix form along the plurality of scanning signal lines and the plurality of data signal lines, the method comprising:
an image data correction step of generating driving image data by correcting input image data that represents an image to be displayed;
a data signal line drive step of driving the plurality of data signal lines based on the driving image data; and
a scanning signal line drive step of selectively driving the plurality of scanning signal lines,
wherein the first power supply voltage line includes a trunk wire, and a plurality of branch wires diverging from the trunk wire and arranged along the plurality of data signal lines, respectively,
each of the pixel circuits
corresponds to any one of the plurality of scanning signal lines, corresponds to any one of the plurality of data signal lines, and corresponds to any one of the plurality of branch lines,
includes a display element driven by a current, a holding capacitor configured to hold a data voltage for controlling a drive current of the display element, and a drive transistor configured to control the drive current of the display element in accordance with the data voltage held in the holding capacitor, and
is configured such that a voltage of a corresponding data signal line is written in the holding capacitor as a data voltage when a corresponding scanning signal line is selected,
in each of the pixel circuits,
a first conductive terminal of the drive transistor is connected to a branch wire corresponding to the each pixel circuit,
a second conductive terminal of the drive transistor is connected to the second power supply voltage line via the display element, and
a control terminal of the drive transistor is connected to the corresponding branch wire via the holding capacitor,
the image data correction step includes
a current estimation step of obtaining an estimated value of a current that flows in a branch wire corresponding to any one of the plurality pixel circuits when a data voltage is written in the any one pixel circuit, and
a driving data generation step of determining a voltage drop at a connection point between the branch wire and the any one pixel circuit based on the estimated value of the current and correcting image data for the any one pixel circuit in the input image data in accordance with the voltage drop, so as to generate image data corresponding to a data voltage to be written in the any one pixel circuit out of the driving image data,
in the image data correction step, the input image data is input sequentially for each frame, in the current estimation step,
an estimated value of a current supplied from the power supply line to a preceding pixel circuit corresponding to any one of scanning signal lines selected before the scanning signal line corresponding to the any one pixel circuit in which the data voltage is to be written out of pixel circuits on one column connected to the branch wire corresponding to the any one pixel circuit in which the data voltage is to be written, is acquired as a present-frame current value based on the image data for the preceding pixel circuit out of the input image data of the present frame, and
an estimated value of a current supplied from the power supply line to a succeeding pixel circuit corresponding to any one of scanning signal lines selected after the scanning signal line corresponding to the any one pixel circuit in which the data voltage is to be written out of the pixel circuits on the one column, is acquired as an immediately-preceding-frame current value based on the image data for the succeeding pixel circuit out of the input image data of the immediately preceding frame, and
in the driving data generation step, the voltage drop is calculated based on the present-frame current value and the immediately-preceding-frame current value.

### Claim 11 (depends on 10)

The driving method according to claim 10, wherein
the display device further includes a memory capable of storing respective current values of the plurality of pixel circuits and configured to store the present-frame current value for the preceding pixel circuit and store the immediately-preceding-frame current value for the succeeding pixel circuit,
each of the pixel circuits is configured such that no current is supplied from the power supply line to the each pixel circuit when a scanning signal line corresponding to the each pixel circuit is selected,
in the scanning signal line drive step, the plurality of scanning signal lines are selected in ascending order,
the image data correction step further includes a memory write step of sequentially receiving image data for each of the pixel circuits constituting the input image data of each frame in accordance with the selection of the plurality of scanning signal lines in ascending order, and upon receipt of image data for a pixel circuit on an (i+1)th row and a jth column out of the input image data of the present frame, obtaining an estimated value of a current supplied from the power supply line to the pixel circuit on the (i+1)th row and the jth column as the present-frame current value based on the received image data, and rewriting the current value of the pixel circuit on the (i+1)th row and the jth column stored in the memory to the present-frame current value of the pixel circuit, and
the driving data generation step further includes
a voltage drop calculation step of determining, upon receipt of image data for the pixel circuit on the (i+1)th row and the jth column out of the input image data of the present frame, from a voltage at a connection point between a pixel circuit on an ith row and the jth column and a branch wire on the jth column at a time of writing a data voltage in said pixel circuit, a voltage at a connection point between the pixel circuit on the (i+1)th row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit, based on the present-frame current value of the pixel circuit on the ith row and jth column and the immediately-preceding-frame current value stored in the memory as a current value of a pixel circuit on the jth column corresponding to any one of the scanning signal lines selected after a scanning signal line corresponding to the pixel circuit on the ith row and jth column, and calculating the voltage drop based on the determined voltage, and
an image data correction step of correcting the received image data for the pixel circuit on the (i+1)th row and the jth column in accordance with the calculated voltage drop so as to generate image data corresponding to the data voltage to be written in the pixel circuit on the (i+1)th row and jth column out of the driving image data.

### Claim 12 (depends on 11)

The driving method according to claim 11, wherein
each of the pixel circuits is configured such that no current is supplied from the power supply line to the each pixel circuit even when the scanning signal line to be selected immediately before the selection of the scanning signal line corresponding to the each pixel circuit is selected, and
in the voltage drop calculation step, upon receipt of image data for the pixel circuit on the (i+1)th row and the jth column out of the input image data of the present frame, from a voltage at a connection point between the pixel circuit on the ith row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit, a voltage at a connection point between the pixel circuit on the (i+1)th row and the jth column and the branch wire on the jth column at a time of writing a data voltage in said pixel circuit is determined based on the present-frame current value of the pixel circuit on the ith row and jth column and the immediately-preceding-frame current value stored in the memory as a current value of a pixel circuit on an (i+2)th row and the jth column, and the voltage drop is calculated based on the determined voltage.

### Claim 13 (depends on 10)

The driving method according to claim 10, wherein
the trunk wire is formed only in one picture-frame region along the plurality of scanning signal lines out of picture-frame regions adjacent to a display region in which the plurality of pixel circuits are arranged, and
the plurality of branch wires diverge from the trunk wire and are each supplied with a power supply voltage from the trunk wire.