HK1112775B - Display drive apparatus and display apparatus - Google Patents

Description

Display driving device and display device

Technical Field

The present invention relates to a display driving device and a driving method thereof, and a display device and a driving method thereof, and more particularly, to a display driving device that drives a display pixel including a light emitting element that emits light by supplying a current, a display device that includes a display panel in which a plurality of the display pixels are arranged, and displays image information, and a driving method thereof.

Background

In recent years, as a next-generation display following a liquid crystal display device, research and development have been actively conducted on a self-luminous display device including a display panel in which light-emitting elements such as organic light-emitting elements (organic EL elements), inorganic light-emitting elements (inorganic EL elements), or light-emitting diodes (LEDs) are arranged in a matrix.

In particular, a self-luminous display using an active matrix driving method has extremely excellent characteristics that the display response speed is higher and the viewing angle dependency is small as compared with a known liquid crystal display device, and that high luminance and high contrast can be achieved, and high definition of display image quality can be achieved, and that a backlight and a light guide plate are not required as in the liquid crystal display device, and therefore, the self-luminous display can be further thinned. Therefore, it is expected to be applied to various electronic apparatuses in the future.

Such an active matrix driving type self-luminous display includes a display pixel element, a light emitting element, and a pixel driving circuit including a plurality of switching elements (transistors) for controlling the light emitting state of the light emitting element.

As a gradation control method for the display pixel, there is generally a current designation method in which a gradation current having a current value corresponding to display data is supplied to the display pixel, a voltage component corresponding to the current value of the gradation current is held in a pixel drive circuit, and a drive current is caused to flow into a light emitting element based on the held voltage to control light emission luminance; a voltage designating system for supplying a gradation voltage having a voltage value corresponding to display data to a display pixel, holding a voltage component corresponding to a current flowing in accordance with the supplied gradation voltage in a pixel driving circuit, and flowing a driving current to a light emitting element based on the held voltage component to control a light emission luminance.

In the current specification method, even when a characteristic change or variation occurs in the switching element of the pixel drive circuit, an influence on the drive current supplied to the light emitting element can be suppressed, and therefore, a light emitting operation at an appropriate luminance gradation corresponding to display data can be stably realized for a long period of time.

On the other hand, in the voltage specification method, although it is difficult to cause insufficient writing because the current flowing when supplying the gradation voltage to the display pixel can be increased, the current value flowing at the time of writing changes due to the characteristic change of the switching element of the pixel drive circuit, and the voltage component held in the pixel drive circuit changes, so that the current value of the drive current flowing in the light emitting element changes.

The present invention is a display driving device for driving display pixels having light emitting elements and a display device having the display driving device, and has advantages of: the occurrence of write shortage is suppressed, and a change in characteristics of a drive element of a display pixel is compensated, so that a light emitting element is caused to emit light at an appropriate luminance gradation corresponding to display data over a long period of time.

In order to achieve the above-described advantages, a display driving device according to the present invention drives a display pixel including a light emitting element and a driving element in accordance with display data, the display driving device including: a specific value detection circuit that detects a specific value corresponding to a variation amount of an element characteristic of the drive element based on a current value of a current flow path flowing through the drive element when a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the drive element of adjacent gray scales of the display data is applied to the display pixel; and a gradation voltage correction circuit which corrects a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to display data based on a compensation voltage based on the specific value and the unit voltage, generates a corrected gradation voltage, and supplies the corrected gradation voltage to the display pixel.

In order to achieve the above-described advantages, the 1 st display device according to the present invention displays image information corresponding to display data, the display device including: a display panel in which a plurality of display pixels including light emitting elements and driving elements for supplying current flowing in current flow paths to the light emitting elements are arranged in the vicinity of intersections of a plurality of selection lines and data lines arranged in a row direction and a column direction; a selection driving section that sequentially applies a selection signal to each of the plurality of selection lines at a predetermined time and sets the display pixels in each row to a sequentially selected state; a data driving section for generating a gradation signal corresponding to the display data and supplying the gradation signal to each of the display pixels in the row set to the selected state through each of the data lines; the data driving unit includes at least: a specific value detection circuit that detects a specific value corresponding to a variation amount of an element characteristic of each of the driving elements of the plurality of display pixels based on a current value of a current flow path flowing through the driving element of each of the display pixels when a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gradations of the display data is applied to each of the display pixels through each of the data lines; and a gradation voltage correction circuit which corrects a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to the display data based on the compensation voltage based on the specific value and the unit voltage to generate a corrected gradation voltage, and supplies the corrected gradation voltage to each display pixel through each data line as the gradation signal.

In order to achieve the above-described advantages, a 2 nd display device according to the present invention is a display device for displaying image information corresponding to display data, including a display panel in which a plurality of display pixels each including a light-emitting element and a pixel drive circuit for controlling a light-emitting state of the light-emitting element are arranged, the pixel drive circuit including at least: a 1 st switching element to which a power supply voltage is applied by one end of a current flow path, the other end of the current flow path being connected to a connection contact of the light emitting element and to which a signal voltage based on the display data is applied; a 2 nd switching element to which the power supply voltage is applied by one end of a current flow path, the other end of the current flow path being connected to a control terminal of the 1 st switching element; and a voltage holding element connected between the control terminal of the 1 st switching element and the connection contact; the power supply voltage is set to either a 1 st voltage having a voltage value for making the light emitting element non-emitting or a 2 nd voltage having a voltage value for making the light emitting element emitting.

In order to achieve the above advantages, a driving method of a display driving device of the present invention drives a display pixel having a light emitting element and a driving element according to display data, characterized in that: applying a detection voltage to the display pixel based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gray scales of the display data; the display device detects a specific value corresponding to a variation amount of an element characteristic of the driving element based on a current value flowing through a current flow path of the driving element, generates a gradation voltage having a voltage value for causing the light emitting element to perform a light emitting operation with a luminance gradation corresponding to display data, corrects the gradation voltage based on a compensation voltage based on the specific value and the unit voltage, generates a corrected gradation voltage, and supplies the corrected gradation voltage to the display pixel.

In order to achieve the above advantages, the 1 st driving method of a display device according to the present invention is a method of displaying image information corresponding to display data, comprising: the display device includes a display panel in which a plurality of display pixels each having a light-emitting element and a driving element for supplying a current flowing through a current flow path to the light-emitting element are arranged in the vicinity of each intersection of a plurality of selection lines and data lines arranged in a row direction and a column direction; the method comprises the following actions: sequentially applying a selection signal to each of the plurality of selection lines to set the display pixels in each row to a sequentially selected state; applying a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gray scales of the display data to the display pixels of the selected row through the data lines; detecting a specific value corresponding to a variation amount of an element characteristic of each of the driving elements based on a current value flowing through a current flow path of the driving element of each of the display pixels; generating a gradation voltage having a voltage value for causing the light emitting element to perform a light emitting operation with a luminance gradation corresponding to the display data; generating a compensation voltage based on the specific value and the unit voltage; the gradation voltage is corrected based on the compensation voltage to generate a corrected gradation voltage, and the corrected gradation voltage is supplied to each display pixel in the selected row through each data line.

In order to achieve the above-described advantages, a 2 nd driving method of a display device according to the present invention is a driving method of a display device for displaying image information corresponding to display data, the display device including a display panel in which a plurality of display pixels each including a light-emitting element and a pixel driving circuit for controlling a light-emitting state of the light-emitting element are arranged, the pixel driving circuit including at least:

a 1 st switching element to which a power supply voltage is applied by one end of a current flow path, the other end of the current flow path being connected to a connection contact of the light emitting element and to which a signal voltage based on the display data is applied;

a voltage holding element connected between the control terminal of the 1 st switching element and the connection contact;

the power supply voltage is set to either a 1 st voltage having a voltage value for making the light emitting element non-emitting or a 2 nd voltage having a voltage value for making the light emitting element emitting.

In order to achieve the above-mentioned advantages, a driving method of a display driving device of the present invention is the 1 st driving method of a display device of the present invention for achieving the above-mentioned advantages, a driving method of a display driving device for driving a display pixel having a light emitting element and a driving element, wherein a detection voltage based on a unit voltage set in accordance with the characteristics of the drive element is applied to the display pixel, a specific value corresponding to the variation of the element characteristics of the drive element is detected based on the current value flowing through the current path of the drive element, and a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to display data is generated, the gradation voltage is corrected based on the compensation voltage based on the specific value and the unit voltage, a corrected gradation voltage is generated, and the display pixel is provided.

In order to achieve the above-described advantages, a 1 st driving method of a display device according to the present invention is a driving method of a display device for displaying image information corresponding to display data, the display device including a display panel in which a plurality of display pixels having a light emitting element and a driving element for supplying a current flowing through a current flow path to the light emitting element are arranged in the vicinity of each intersection of a plurality of selection lines and data lines arranged in a row direction and a column direction, the method including the acts of sequentially applying a selection signal to each of the plurality of selection lines, setting the display pixels in each row to a sequentially selected state, applying a detection voltage based on a predetermined unit voltage to each of the display pixels in the selected row via each of the data lines, and based on a current value of the current flow path flowing through the driving element of each of the display pixels, and a correction voltage generation unit that generates a correction gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to the display data, and supplies the correction gradation voltage to each of the display pixels in the selected row via each of the data lines.

In order to achieve the above-described advantages, a 2 nd driving method of a display device according to the present invention is a driving method of a display device for displaying image information corresponding to display data, the display device including a display panel in which a plurality of display pixels each including a light-emitting element and a pixel driving circuit for controlling a light-emitting state of the light-emitting element are arranged, the pixel driving circuit including at least:

a 1 st switching element to which a power supply voltage is applied by one end of a current flow path, the other end of the current flow path being connected to a connection contact of the light emitting element and to which a signal voltage based on the display data is applied;

a 2 nd switching element to which the power supply voltage is applied by one end of a current flow path, the other end of the current flow path being connected to a control terminal of the 1 st switching element; and

a voltage holding element connected between the control terminal of the 1 st switching element and the connection contact;

the driving method includes a writing operation of turning on the current flow path of the 2 nd switching element, electrically connecting a control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element, setting the power supply voltage to a 1 st voltage having a voltage value that causes the light emitting element to be in a non-light emitting state, and applying a data voltage corresponding to display data to the other end of the current flow path; and a light emitting operation of rendering the current flow path of the 2 nd switching element non-conductive, electrically disconnecting the control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element, setting the power supply voltage to a 2 nd voltage having a voltage value for causing the light emitting element to emit light, and causing a drive current based on the voltage component held in the voltage holding element to flow through the light emitting element.

Drawings

Fig. 1 is an equivalent circuit diagram showing a main portion structure of a display pixel used in a display device of the present invention;

fig. 2 is a signal waveform diagram showing a control operation of a display pixel used in the display device of the present invention;

FIGS. 3A and 3B are schematic explanatory views showing an operation state of a display pixel in a write operation;

fig. 4A is a characteristic diagram showing operation characteristics of a driving transistor of a display pixel in a writing operation;

fig. 4B is a characteristic diagram showing a relationship between a drive current and a drive voltage of the organic EL element;

fig. 5A, B is a schematic explanatory view showing an operation state in the holding operation of the display pixel;

fig. 6 is a characteristic diagram showing an operation characteristic of the driving transistor in the holding operation of the display pixel;

fig. 7A, B is a schematic explanatory view showing an operation state in a light emitting operation of a display pixel;

fig. 8A, B is a characteristic diagram showing the operating characteristics of the driving transistor of the display pixel and the load characteristics of the organic EL element during the light emitting operation;

fig. 9 is a schematic configuration diagram showing an embodiment of a display device of the present invention;

fig. 10 is a main part configuration diagram showing an example of a data driver and a display pixel which can be used in the display device of the present embodiment;

fig. 11 is a flowchart showing an example of the correction data acquiring operation of the display device according to the present embodiment;

fig. 12 is a conceptual diagram illustrating a correction data acquiring operation of the display device according to the present embodiment;

fig. 13 is a timing chart showing an example of a display driving operation of the display device of the present embodiment;

fig. 14 is a flowchart showing an example of a writing operation of the display device according to the present embodiment;

fig. 15 is a conceptual diagram illustrating a writing operation of the display device according to the present embodiment;

fig. 16 is a conceptual diagram illustrating a holding operation of the display device according to the present embodiment;

fig. 17 is a conceptual diagram illustrating a light emitting operation of the display device of the present embodiment;

fig. 18 is an operation timing chart schematically showing a specific example of the driving method of the display device according to the present embodiment.

Detailed Description

Hereinafter, a display driving device and a driving method thereof, and a display device and a driving method thereof according to the present invention will be described in detail based on the illustrated embodiments.

< major structure of display Pixel >

First, a main structure of a display pixel used in a display device of the present invention and a control operation thereof will be described with reference to the drawings.

Fig. 1 is an equivalent circuit diagram showing a main structure of a display pixel used in a display device of the present invention.

Here, as a current control type light emitting element provided in a display pixel, a case where an organic EL element is used will be described for convenience.

As shown in fig. 1, the display device of the present invention includes a pixel driving circuit DCx and an organic EL element OLED serving as a current-controlled light-emitting element.

The pixel drive circuit DCx has, for example:

a driving transistor T1 (1 st switching element) having a drain terminal and a source terminal connected to a power supply terminal TMv to which a power supply voltage Vcc is applied and a contact N2, respectively, and a gate terminal connected to a contact N1;

a holding transistor T2 (2 nd switching element) having a drain terminal and a source terminal connected to a power supply terminal TMv (drain terminal of the driving transistor T1) and a contact N1, respectively, and a gate terminal connected to the control terminal TMh;

the capacitor (voltage holding element) Cx is connected between the gate and source terminals of the driving transistor T1 (between the contact N1 and the contact N2).

The organic EL element OLED is connected to the anode terminal through the contact N2, and the constant voltage Vss is applied to the cathode terminal TMc.

Here, as described in the control operation to be described later, the power supply voltage Vcc having a voltage value different depending on the operation state is applied to the power supply terminal TMv, the power supply voltage Vss is applied to the cathode terminal TMc of the EL element OLED, the hold control signal Shld is applied to the control terminal TMh, and the data voltage Vdata corresponding to the gradation value of the display data is applied to the data terminal TMd connected to the contact N2, depending on the operation state of the display pixel (pixel drive circuit DCx).

The capacitance Cx may be a parasitic capacitance formed between the gate and source terminals of the driving transistor T1, or may be a capacitance formed by connecting a capacitance element in parallel between the contact N1 and the contact N2 in addition to the parasitic capacitance. The element structures, characteristics, and the like of the driving transistor T1 and the holding transistor T2 are not particularly limited, and an n-channel thin film transistor is used here.

< control action of display Pixel >

Next, a control operation (driving method) of the display pixels (the pixel driving circuit DCx and the organic EL element OLED) having the above-described circuit configuration will be described.

Fig. 2 is a signal waveform diagram showing a control operation of a display pixel of the display device of the present invention.

As shown in fig. 2, the operation states of the display pixel (pixel driving circuit DCx) having the circuit structure shown in fig. 1 can be roughly divided into: a write operation of writing a voltage component corresponding to a gradation value of the display data into the capacitance Cx; a holding operation of holding the voltage component written in the writing operation in the capacitance Cx; and a light emission operation of causing a gradation current corresponding to the gradation value of the display data to flow into the organic EL element OLED based on the voltage component held by the holding operation, and causing the organic EL element OLED to emit light with a luminance gradation corresponding to the display data. Each operation state will be specifically described below with reference to the timing chart shown in fig. 2.

(write action)

In the writing operation, in a light-off state where the organic EL element OLED is not caused to emit light, an operation of writing a voltage component corresponding to the gradation value of the display data into the capacitance Cx is performed.

Fig. 3A and 3B are schematic explanatory views showing an operation state of the display pixel in the writing operation.

Fig. 4A is a characteristic diagram showing operation characteristics of the driving transistor of the display pixel in the writing operation.

Fig. 4B is a characteristic diagram showing a relationship between a drive current and a drive voltage of the organic EL element.

A solid line SPw shown in fig. 4A is a characteristic line showing a relationship between the drain-source voltage Vds and the drain-source current Ids in an initial state in which an n-channel thin film transistor is used as the driving transistor T1 and the diode is connected. The broken line SPw2 shows an example of a characteristic line of the driving transistor T1 when a characteristic change occurs with a driving process. As will be described in detail later. A point PMw on the characteristic line SPw indicates an operation point of the driving transistor T1.

The characteristic line SPw has a threshold voltage Vth with respect to the drain-source current Ids, and if the drain-source voltage Vds exceeds the threshold voltage Vth, the drain-source current Ids increases nonlinearly with an increase in the drain-source voltage Vds. That is, in the figure, the value indicated by Veff _ gs is a voltage component that effectively forms the drain-source current Ids, and the drain-source voltage Vds is the sum of the threshold voltage Vth and the voltage component Veff _ gs, as shown in equation (1).

Vds＝Vth+Veff_gs……(1)

A solid line SPe shown in fig. 4B is a characteristic line showing a relationship between the driving voltage Voled and the driving current Ioled in the initial state of the organic EL element OLED. The chain line SPe2 is an example of a characteristic line when the characteristics of the organic EL element OLED change with the driving process. As will be described in detail later. The characteristic line SPe has a threshold voltage Vth _ oled with respect to the driving voltage Voled, and when the driving voltage Voled exceeds the threshold voltage Vth _ oled, the driving current Ioled increases non-linearly with an increase in the driving voltage Voled.

In the write operation, first, as shown in fig. 2 and 3A, the hold control signal Shld at the on level (high level) is applied to the control terminal TMh of the hold transistor T2, and the hold transistor T2 is turned on. Thereby connecting (short-circuiting) the gate-drain of the driving transistor T1, and setting the driving transistor T1 to a diode-connected state.

Next, the first power supply voltage Vccw for the write operation is applied to the power supply terminal TMv, and the data voltage Vdata corresponding to the gradation value of the display data is applied to the data terminal TMd. At this time, a current Ids corresponding to the drain-source potential difference (Vccw-Vdata) flows between the drain and the source of the driving transistor T1. The data voltage Vdata is set to a voltage value such that the current Ids flowing between the drain and the source becomes a current value required to cause the organic EL element OLED to emit light with a luminance gradation corresponding to the gradation value of the display data.

At this time, since the driving transistor T1 is diode-connected, as shown in fig. 3B, the drain-source voltage Vds of the driving transistor T1 is equal to the gate-source voltage Vgs, as shown by equation (2).

Vds＝Vgs＝Vccw-Vdata……(2)

Then, the gate-source voltage Vgs is written (charged) into the capacitance Cx.

Here, a condition required for the value of the first power supply voltage Vccw will be described. Since the driving transistor T1 is of an n-channel type, in order for the drain-source current Ids to flow, the gate potential of the driving transistor T1 must be positive with respect to the source potential, the gate potential is equal to the drain potential, the first power supply voltage Vccw, and the source potential is the data voltage Vdata, and therefore the relationship of expression (3) must be established.

Vdata＜Vccw……(3)

Further, the contact N2 is connected to the data terminal TMd and also to the anode terminal of the organic EL element OLED, and in order to turn off the organic EL element OLED during writing, the potential Vdata of the contact N2 is required to be equal to or less than the value obtained by adding the threshold voltage Vth _ OLED of the organic EL element OLED to the voltage Vss of the cathode terminal TMc of the organic EL element OLED, and therefore the potential Vdata of the contact N2 is required to satisfy expression (4).

Vdata≤Vss+Vth_oled……(4)

Here, if Vss is set to the ground potential 0V, equation (5) is obtained.

Vdata≤Vth_oled……(5)

Next, formula (6) is obtained from formulae (2) and (5).

Vccw-Vgs≤Vth_oled……(6)

Further, from equation (1), Vgs — Vds — Vth + Veff — gs yields equation (7).

Vccw≤Vth_oled+Vth+Veff_gs……(7)

Here, even if Veff _ gs is 0, the expression (7) must be satisfied, and therefore, when Veff _ gs is 0, the expression (8) is obtained.

Vdata＜Vccw≤Vth_oled+Vth……(8)

In other words, in the write operation, the value of the first power supply voltage Vccw needs to be set to a value satisfying the relationship of expression (8) in the state where the diode is connected. Next, the influence of the characteristic change of the driving transistor T1 and the organic EL element OLED with the continuation of the driving process will be described. It is known that the threshold voltage Vth of the driving transistor T1 increases according to the driving process.

A broken line SPw2 shown in fig. 4A represents an example of a characteristic line when a characteristic change occurs due to a driving process, and Δ Vth represents a change amount of the threshold voltage Vth. As shown in the figure, the characteristic change of the driving transistor T1 due to the driving process is changed in such a manner that the initial characteristic line is shifted almost in parallel. Therefore, in order to obtain a gradation current (drain-source current Ids) corresponding to the gradation value of the display data, the required value of the data voltage Vdata must be increased by only the change amount Δ Vth of the threshold voltage Vth.

Further, it is known that the organic EL element OLED has high impedance according to a driving process. The chain line SPe2 shown in fig. 4B shows an example of a characteristic line when a characteristic change occurs according to a driving process, and the characteristic change of the organic EL element OLED due to high impedance change caused by the driving process changes in a direction of approximately decreasing the increase rate of the driving current Ioled with respect to the driving voltage Voled with respect to the initial characteristic line. In other words, the driving voltage Voled for flowing the driving current Ioled necessary for causing the organic EL element OLED to emit light with the luminance gradation corresponding to the gradation value of the display data is increased only by the portion of the characteristic line SPe2 — the characteristic line SPe. As shown by Δ Voled max in fig. 4B, when the driving current Ioled is the maximum value Ioled (max) and the highest gradation is obtained, the increased portion is the largest.

(holding action)

Fig. 5A, B is a schematic explanatory view showing an operation state in the holding operation of the display pixel.

Fig. 6 is a characteristic diagram showing operation characteristics of the driving transistor in the holding operation of the display pixel.

In the holding operation, as shown in fig. 2 and 5A, the holding control signal Shld at the off level (low level) is applied to the control terminal TMh, so that the holding transistor T2 is turned off, the gate-drain of the driving transistor T1 is disconnected (non-connected state), and the diode connection is released. Thus, as shown in fig. 5B, the voltage Vds between the drain and the source of the driving transistor T1 (gate-source voltage Vgs) that charges the capacitance Cx is held in the above-described writing operation.

The solid line SPh shown in fig. 6 is a characteristic line when the diode connection of the driving transistor T1 is released and the gate-source voltage Vgs is a constant voltage.

A broken line SPw shown in fig. 6 is a characteristic line when the driving transistor T1 is diode-connected. The holding operation point PMh is an intersection of the characteristic line SPw when the diode is connected and the characteristic line SPh when the diode is disconnected.

The chain line SPo shown in fig. 6 is introduced as the characteristic line SPw-Vth, and the intersection Po of the chain line SPo and the characteristic line SPh represents the pinch-off voltage Vpo. Here, as shown in fig. 6, in the characteristic line SPh, the drain-source voltage Vds is in an unsaturated region in a region from 0V to the pinch-off voltage Vpo, and the drain-source voltage Vds is in a saturated region in a region equal to or higher than the pinch-off voltage Vpo.

(Lighting action)

Fig. 7A, B is a schematic explanatory view showing an operation state in a light emitting operation of a display pixel.

Fig. 8A, B is a characteristic diagram showing the operating characteristics of the driving transistor of the display pixel and the load characteristics of the organic EL element during the light emitting operation.

As shown in fig. 2 and 7A, the state where the hold control signal Shld at the off level (low level) is applied to the control terminal TMh (the state where the diode connection state is released) is maintained, and the first power supply voltage Vccw for writing the terminal voltage Vcc of the power supply terminal TMv is switched to the second power supply voltage Vcce for light emission. As a result, the current Ids corresponding to the voltage component Vgs held in the capacitance Cx flows between the drain and the source of the driving transistor T1, and the current is supplied to the organic EL element OLED, so that the organic EL element OLED emits light at a luminance corresponding to the supplied current value.

A solid line SPh shown in fig. 8A is a characteristic line of the driving transistor T1 when the gate-source voltage Vgs is made constant. The solid line SPe represents a load line of the organic EL element OLED, and is obtained by plotting the driving voltage Voled-driving current Ioled characteristic of the organic EL element OLED in reverse direction with reference to the potential difference between the power supply terminal TMv and the cathode terminal TMc of the organic EL element OLED, i.e., the value of Vcce-Vss.

The operating point of the driving transistor T1 during the light emission operation shifts from PMh during the holding operation to PMe, which is the intersection of the characteristic line SPh of the driving transistor T1 and the load line SPe of the organic EL element OLED. Here, as shown in fig. 8A, the operating point PMe indicates a point at which a voltage of Vcce-Vss is divided between the source-drain of the driving transistor T1 and between the anode and the cathode of the organic EL element OLED in a state where the voltage is applied between the power supply terminal TMv and the cathode terminal TMc of the organic EL element OLED. In other words, at the operating point PMe, the voltage Vds is applied between the source and the drain of the driving transistor T1, and the driving voltage Voled is applied between the anode and the cathode of the organic EL element OLED.

Here, in order to prevent the current Ids (expected value current) flowing between the drain and the source of the driving transistor T1 during the writing operation and the driving current Ioled supplied to the organic EL element OLED during the light emitting operation from changing, the operating point PMe must be maintained within the saturation region on the characteristic line. Voled becomes the maximum Voled (max) at the highest gradation. Therefore, in order to maintain the PMe in the saturation region, the value of the second power supply voltage Vcce must satisfy the condition of expression (9).

Vcce-Vss≥Vpo+Voled(max)……(9)

Here, when Vss is set to the ground potential 0V, expression (10) is obtained.

Vcce≥Vpo+Voled(max)……(10)

< relationship between change in characteristics of organic element and Voltage-Current characteristics >

As shown in fig. 4B, the organic EL element OLED is made high impedance according to the driving process, and changes in a direction in which the increase rate of the driving current Ioled with respect to the driving voltage Voled decreases. In other words, the change is in the direction in which the slope of the load line SPe of the organic EL element OLED shown in fig. 8A decreases. Fig. 8B is a graph showing changes in accordance with the driving process of the load line SPe of the organic EL element OLED, where the load line changes from SPe → SPe2 → SPe 3. Therefore, as a result, the action point of the driving transistor T1 moves in the direction of PMe → PMe2 → PMe3 on the characteristic line SPh of the driving transistor T1 accompanying the driving process.

At this time, the operation point is located in the saturation region on the characteristic line (PMe → PMe2), and the drive current Ioled maintains the value of the current of the expected value in the write operation, but when the operation point enters the unsaturated region (PMe3), the drive current Ioled is reduced from the current of the expected value in the write operation, and a display defect occurs. In fig. 8B, the pinch-off point Po is located on the boundary between the unsaturated region and the saturated region, that is, the potential difference between the operating points PMe and Po at the time of light emission becomes a compensation margin for maintaining the OLED drive current at the time of light emission with respect to high impedance of the organic EL. In other words, at each Ioled level, the potential difference on the characteristic line SPh of the driving transistor between the locus SPo of the pinch-off point and the load line SPe of the organic EL element becomes a compensation margin. As shown in fig. 8B, the compensation margin decreases with an increase in the value of the drive current Ioled, and increases with an increase in the voltage Vcce-Vss applied between the power supply terminal TMv and the cathode terminal TMc of the organic EL element OLED.

< relationship between variation in characteristics of TFT element and voltage-current characteristics >

However, in the voltage gradation control using the transistor employed in the display pixel (pixel driving circuit), the data voltage Vdata is set according to the characteristics of the drain-source voltage Vds-drain-source current Ids of the transistor set in advance, but as shown in fig. 4A, the threshold voltage Vth increases according to the driving process, the current value of the light emission driving current supplied to the light emitting element (organic EL element OLED) does not correspond to the display data (data voltage), and the light emission operation cannot be performed with an appropriate luminance gradation. It is known that, particularly when an amorphous silicon transistor is employed as a transistor, variations in element characteristics are significantly generated.

Here, an example of initial characteristics (voltage-current characteristics) of the drain-source voltage Vds and the drain-source current Ids in the amorphous silicon transistor having the design values shown in table 1 when a display operation of 256 gradations is performed is shown.

[ Table 1]

< design value of transistor >

Gate insulation film thickness	300nm (3000)
		Width W of channel	500μm
Channel length L	6.28μm
		Threshold voltage Vth	2.4V

In the voltage-current characteristic of the n-channel type amorphous silicon transistor, that is, the relationship between the drain-source voltage Vds and the drain-source current Ids shown in fig. 4A, an increase in Vth (movement from the initial state: SPw to the high voltage side: SPw 2) due to gate electric field cancellation due to carrier trapping to the gate insulating film accompanying the driving process and time variation occurs. Therefore, when the drain-source voltage Vds applied to the amorphous silicon transistor is a constant voltage, the drain-source current Ids decreases, and the luminance gradation of the light-emitting element decreases.

In the change of the element characteristics, the threshold voltage Vth is mainly increased, and the voltage-current characteristic line (V-I characteristic line) of the amorphous silicon transistor is in a shape in which the characteristic line in the initial state is shifted almost in parallel, so that the shifted V-I characteristic line SPw2 can be substantially matched with the voltage-current characteristic obtained by simply adding a constant voltage (corresponding to the offset voltage Vofst described later) corresponding to the amount of change Δ Vth (about 2V in the figure) in the drain-source voltage Vds of the V-I characteristic line SPw in the initial state (that is, when the V-I characteristic line SPw is shifted only in parallel by Δ Vth).

In other words, at the time of a write operation for writing display data into a display pixel (pixel drive circuit DCx), a data voltage (corresponding to a correction gradation voltage Vpix described later) obtained by adding and correcting a constant voltage (offset voltage Vofst) corresponding to a variation Δ V in the element characteristic (threshold voltage) of the drive transistor T1 provided in the display pixel is applied to the source terminal (contact N2) of the drive transistor T1, whereby it is possible to compensate for a shift in the voltage-current characteristic due to a variation in the threshold voltage Vth of the drive transistor T1, and to cause the drive current em having a current value corresponding to the display data to flow into the organic EL element OLED, thereby performing a light emission operation at a desired gradation.

Further, the holding operation of switching the holding control signal Shld from the on level to the off level and the light emitting operation of switching the power supply voltage Vcc from the voltage Vccw to the voltage Vcce may be performed simultaneously.

Hereinafter, a display device having a display panel in which a plurality of display pixels including the main structure of the pixel driving circuit are arranged in 2 dimensions will be described in detail with reference to the entire structure thereof.

< display device >

Fig. 9 is a schematic configuration diagram showing an embodiment of a display device of the present invention.

Fig. 10 is a main part configuration diagram showing an example of a data driver and a display pixel which can be used in the display device of the present embodiment.

Fig. 10 shows a circuit configuration corresponding to the pixel drive circuit DCx (see fig. 1). In fig. 10, for convenience of explanation, various signals and data transmitted from between the respective structures of the data driver, and applied currents and voltages are all conveniently shown by arrows, but as described later, these signals and data, currents and voltages are not limited to being transmitted or applied at the same time.

As shown in fig. 9 and 10, the display device 100 of the present embodiment includes:

a display panel 110 in which a plurality of display pixels PIX including the main configuration of the pixel drive circuit DCx (see fig. 1) are arranged in a matrix of n rows × m columns (n, m are any positive integer), for example, in the vicinity of each intersection of a plurality of selection lines Ls arranged in a row direction (horizontal direction in the figure) and a plurality of data lines Ld arranged in a column direction (vertical direction in the figure);

a selection driver (selection driving section) 120 that applies a selection signal Ssel to each selection line Ls at a predetermined timing;

a power supply driver (power supply driving section) 130 which is parallel to the selection line Ls and applies a power supply voltage Vcc of a predetermined voltage level to a plurality of power supply voltage lines Lv arranged in the row direction at a predetermined timing;

a data driver (display driving device, data driving unit) 140 for supplying a gradation signal (correction gradation voltage Vpix) to each data line Ld at a predetermined timing;

a system controller 150 that generates and outputs a selection control signal, a power supply control signal, and a data control signal for controlling at least the operation states of the selection driver 120, the power supply driver 130, and the data driver 140, based on a timing signal supplied from a display signal generation circuit 160, which will be described later;

the display signal generation circuit 160 generates display data (luminance gradation data) made of a digital signal based on an image signal supplied from, for example, the outside of the display device 100, supplies the display data to the digital driver 140, extracts or generates a timing signal (system clock or the like) for displaying predetermined image information on the display panel 110 based on the display data, and supplies the timing signal to the system controller 150.

The above-described configurations will be explained below.

(display panel)

In the display device 100 of the present embodiment, as shown in fig. 9, a plurality of display pixels PIX arranged in a matrix on a substrate of the display panel 110 are grouped into an upper region and a lower region of the display panel 110, and the display pixels PIX included in each group are connected to the branched power supply voltage lines Lv, respectively. In other words, the power supply driver 130 independently outputs the power supply voltage Vcc commonly applied to the display pixels PIX in the 1 st to n/2 nd rows in the upper area of the display panel 110 and the power supply voltage Vcc commonly applied to the display pixels PIX in the 1+ n/2 th to n th rows in the lower area through different power supply voltage lines Lv at different timings. The select driver 120 and the data driver 140 may be disposed in the display panel 110, or the select driver 120, the power driver 130, and the data driver 140 may be disposed in the display panel 110.

(display pixel)

The display pixel PIX according to the present embodiment is disposed in the vicinity of an intersection between the select line Ls connected to the select driver 120 and the data line Ld connected to the data driver 140, and includes, for example, as shown in fig. 10: an organic EL element OLED which is a current control type light emitting element; and a pixel drive circuit DC which includes the main structure of the pixel drive circuit DCx (see fig. 1) and generates a light emission drive current for driving the organic EL element OLED to emit light.

The pixel drive circuit DC includes: a transistor Tr11 (diode connection transistor; 2 nd switch circuit) having a gate terminal connected to the selection line Ls, a drain terminal connected to the power supply voltage line Lv, and a source terminal connected to the junction N11; a transistor Tr12 (selection transistor) having a gate terminal connected to the selection line Ls, a source terminal connected to the data line Ld, and a drain terminal connected to the contact N12; a transistor Tr13 (driving transistor; driving element, 1 st switching circuit) having a gate terminal connected to the junction N11, a drain terminal connected to the power supply voltage line Lv, and a source terminal connected to the junction N12; and a capacitor Cs (voltage holding element) connected between the junction N11 and the junction N12 (between the gate-source terminals of the transistor Tr 13).

Here, the transistor Tr13 corresponds to the drive transistor T1 shown in the main configuration of the pixel drive circuit DCx (fig. 1), the transistor Tr11 corresponds to the holding transistor T2, the capacitance Cs corresponds to the capacitance Cx, and the contact N11 and the contact N12 correspond to the contact N1 and the contact N2, respectively. The selection signal Ssel applied to the selection line Ls from the selection driver 120 corresponds to the retention control signal Shld, and the gradation signal (the correction gradation voltage Vpix or the detection voltage Vdet) applied to the data line Ld from the data driver 140 corresponds to the data voltage Vdata.

The anode terminal of the organic EL element OLED is connected to the contact N12 of the pixel driving circuit DC, and a constant low voltage, i.e., a reference voltage Vss, is applied to the cathode terminal TMc.

Here, in the drive control operation of the display device to be described later, during the write operation period in which the gradation signal (the correction gradation voltage Vpix) corresponding to the display data is supplied to the pixel drive circuit DC, the correction gradation voltage Vpix applied by the data driver 140, the reference voltage Vss, and the high-potential power supply voltage Vcc (Vcce) applied to the power supply voltage line Lv during the light emission operation period satisfy the relationships (3) to (10) described above, and therefore the organic EL element OLED is not turned on during writing.

Further, the capacitance Cs may be a parasitic capacitance formed between the gate and the source of the transistor Tr13, or may be a capacitive element other than the transistor Tr13 connected between the contact N11 and the contact N12 in addition to the parasitic capacitance.

The transistors Tr11 to Tr13 are not particularly limited, and may be all formed of, for example, n-channel field effect transistors, and thus n-channel amorphous silicon thin film transistors may be used. In this case, the pixel drive circuit DC including the amorphous silicon thin film transistor having stable operation characteristics (such as electron mobility) can be manufactured by a relatively simple manufacturing method using an already established amorphous silicon manufacturing technique. In the following description, a case where the transistors Tr11 to Tr13 are all formed of n-channel type thin film transistors will be described.

The circuit configuration of the display pixel PIX (pixel drive circuit DC) is not limited to the configuration shown in fig. 10, and may have a configuration including at least elements corresponding to the drive transistor T1, the holding transistor T2, and the capacitance Cx shown in fig. 1, and the current flow path of the drive transistor T1 may be connected in series to the current control type light emitting element (organic EL element OLED), or may have another circuit configuration. The light-emitting element driven to emit light by the pixel drive circuit DC is not limited to the organic EL element OLED, and may be another current-controlled light-emitting element such as a light-emitting diode.

(selection driver)

The select driver 120 applies a select signal Ssel of a select level (high level in the display pixels PIX shown in fig. 10) to each select line Ls based on a select control signal supplied from the system controller 150, thereby setting the display pixels PIX of each row to a selected state. Specifically, in the correction data acquisition operation period and the write operation period, which will be described later, the operation of applying the high-level selection signal Ssel to the selection line Ls of each row is sequentially performed for each row at a predetermined timing, whereby the display pixels PIX in each row are set in the sequentially selected state.

The select driver 120 may adopt a structure having: a shift register that sequentially outputs shift signals corresponding to the selection lines Ls of the respective rows based on, for example, a selection control signal supplied from a system controller 150 described later; the output circuit unit (output buffer) converts the shift signal into a predetermined signal level (selection level) and sequentially outputs the signal to the selection line Ls in each row as a selection signal Ssel. If the driving frequency of the select driver 120 is within a possible range in the action in the amorphous silicon transistor, the transistors Tr11 to Tr13 within the pixel driving circuit DC may be manufactured, and a part or all of the transistors included in the select driver 120 may be manufactured.

(Power driver)

The power supply driver 130 applies a low-potential power supply voltage Vcc (Vccw: 1 st voltage) to each power supply voltage line Lv at least during a correction data acquiring operation period and a writing operation period, which will be described later, based on a power supply control signal supplied from the system controller 150, and applies a power supply voltage Vcc (Vcce: 2 nd voltage) having a potential higher than the low-potential power supply voltage Vccw during a light emitting operation period.

Here, in the present embodiment, as shown in fig. 9, the display pixels PIX are grouped into, for example, an upper region and a lower region of the display panel 110, and the branched power supply voltage lines Lv are arranged in each group, so that the power supply voltage Vcc having the same voltage level is applied to the display pixels PIX arranged in the same region (included in the same group) via the power supply voltage lines Lv arranged so as to be branched in the region during each operation period.

Further, the power driver 130 may have a structure including: a timing generator (for example, a shift register which sequentially outputs shift signals) which generates a timing signal corresponding to the power supply voltage line Lv of each region (group) based on the power supply control signal supplied from the system controller 150; the output circuit unit converts the timing signal into a predetermined voltage level (voltage values Vccw, Vcce) and outputs the voltage level as a power supply voltage Vcc to the power supply voltage line Lv of each region.

(data driver)

The data driver 140 detects a specific value (offset set value Vofst) corresponding to a variation in the element characteristic (threshold voltage) of the light emission driving transistor Tr13 (corresponding to the driving transistor T1) provided in each display pixel PIX (pixel driving circuit DC) arranged in the display panel 110, stores the value in each display pixel PIX as correction data, corrects a signal voltage (original gradation voltage Vorg) corresponding to display data (luminance gradation data) of each display pixel PIX supplied from a display signal generation circuit 160 described later based on the correction data, generates a correction gradation voltage Vpix, and supplies the correction gradation voltage Vpix to each display pixel PIX through the data line Ld.

Here, for example, as shown in fig. 10, the data driver 140 includes: a shift register/data register section (gradation data transfer circuit, specific value transfer circuit, correction data transfer circuit) 141, a gradation voltage generation section (gradation voltage generation circuit) 142, an offset voltage generation section (specific value detection circuit, detection voltage setting circuit, specific value extraction circuit, compensation voltage generation circuit) 143, a voltage adjustment section (gradation voltage correction circuit) 144, a current comparison section (specific value detection circuit, current comparison circuit) 145, and a frame memory (memory circuit) 146. Here, the gradation voltage generating section 142, the bias voltage generating section 143, the voltage adjusting section 144, and the current comparing section 145 are provided on the data line Ld of each column, and m groups are provided in the display device 100 of the present embodiment. In the present embodiment, as shown in fig. 10, the case where the frame memory 146 is built in the data driver 140 has been described, but the present invention is not limited to this, and may be separately provided outside the data driver 140.

The shift register/data register section 141 includes: for example, a shift register sequentially outputting shift signals based on a data control signal supplied from the system controller 150; the data register transfers the display data supplied from the display signal generating circuit 160 to the gradation voltage generating portions 142 provided in the respective columns based on the shift signal, acquires the correction data output from the offset voltage generating portions 143 provided in the respective columns at the time of the correction data acquiring operation, and outputs the correction data to the frame memory 146, and acquires the correction data output from the frame memory 146 at the time of the writing operation and the correction data acquiring operation, and transfers the correction data to the offset voltage generating portions 143.

The shift register/data register section 141 selectively performs at least one operation of sequentially acquiring display data (luminance gradation data) corresponding to the display pixels PIX for each 1 row of the display panel 110, which are sequentially supplied as serial data from the display signal generation circuit 160 to be described later, and transferring the display data to the gradation voltage generation sections 142 provided for the respective columns; an operation of acquiring correction data corresponding to the amounts of change in the element characteristics (threshold voltages) of the transistor Tr13 and the transistor Tr12 of each display pixel PIX (pixel drive circuit DC) output from the bias voltage generator 143 provided for each column based on the comparison determination result of the current comparator 145, and sequentially transferring the correction data to the frame memory 146; the correction data of the display pixels PIX of 1 specific row are sequentially acquired from the frame memory 146 and transferred to the bias voltage generating units 143 provided for the respective columns. These actions will be described in detail later.

The gradation voltage generating section 142 generates and outputs an original gradation voltage Vorg having a voltage value for causing the organic EL element OLED to perform a light emitting operation or a non-light emitting operation (black display operation) at a predetermined luminance gradation based on the display data of each display pixel PIX acquired by the shift register/data register section 141.

Here, as a configuration for generating the original gray-scale voltage Vorg having a voltage value corresponding to the display data, a configuration may be adopted which has: for example, a digital-to-analog converter (D/a converter) for converting a digital signal voltage of the display data into a logic signal voltage based on a gradation reference voltage (a reference voltage corresponding to the number of gradations included in the display data) supplied from a power supply unit (not shown); and an output circuit for outputting the analog signal voltage as the original gray-scale voltage Vorg at a predetermined timing.

The offset voltage generator 143 generates and outputs an offset voltage (offset voltage) Vofst corresponding to the amount of change (corresponding to/Δ Vth shown in fig. 4A) in the threshold voltage of the transistor Tr13 of each display pixel PIX (pixel drive circuit DC) based on the correction data acquired from the frame memory 146. Here, when the pixel drive circuit DC has the circuit configuration shown in fig. 10, since the direction of the current flowing into the data line Ld during the write operation is set to flow from the data line Ld to the data driver 140 side, the generated offset voltage (offset voltage) Vofst is also set so that the current flows from the power supply voltage line Lv through the drain-source electrode of the transistor Tr13, the drain-source electrode of the transistor Tr12, and the data line Ld.

Specifically, the value satisfies the following expression (1) in the write operation.

Vofst＝Vunit×Minc……(11)

Here, Vunit is a unit voltage, is a preset voltage minimum unit, and is a negative potential. Minc is an offset setting value and is digital correction data read from the frame memory 146. As will be described in detail later.

In this way, the offset voltage Vofst is a voltage obtained by correcting the amount of change in the threshold voltage of the transistor Tr13 and the amount of change in the threshold voltage of the transistor Tr12 in each display pixel PIX (pixel drive circuit DC) so that a corrected gradation current having a value approximated to a normal gradation current by the corrected gradation voltage Vpix flows between the drain and the source of the transistor Tr 13.

On the other hand, in the correction data acquisition operation performed before the write operation, the value of the offset set value Minc multiplied by the unit voltage vuit is appropriately changed until the offset set value (variable) Minc becomes the optimum value, so that optimization is realized. Specifically, the offset voltage Vofst corresponding to the initial offset set value Minc is generated, and the offset set value Minc is output to the shift register/data register unit 141 as the correction data based on the comparison determination result output from the current comparing unit 145.

For example, the offset setting value Minc may be set by providing a counter inside the offset voltage generating unit 143, which operates at a predetermined clock frequency, increasing the value of the counter by 1 when a signal of a predetermined voltage value acquired at the timing of the clock frequency CK is input, and sequentially modulating (for example, increasing) the value of the counter based on the comparison determination result, or by providing a setting value for appropriately performing overmodulation processing from the system controller 150 or the like based on the comparison determination result.

Further, the unit voltage vuit can be set to an arbitrary constant voltage, but the smaller the absolute value of the voltage of the unit voltage vuit is set, the smaller the voltage difference between the offset voltages Vofst can be made, so that the offset voltage Vofst approximated by the amount of change in the threshold voltage of the transistor Tr13 of each display pixel PIX (pixel drive circuit DC) can be generated in the write operation, and the gradation signal can be corrected more finely and more appropriately.

As the voltage value set to the unit voltage Vunit, for example, a voltage difference between drain-source voltages Vds of adjacent gray scales in a voltage-current characteristic (for example, an operation characteristic diagram shown in fig. 4A) of a transistor can be used. The unit voltage vuit may be stored in a memory provided in the bias voltage generator 143 and the data driver 140, or may be supplied from the system controller 150 or the like and temporarily stored in a register provided in the data driver 140.

At this time, it is preferable that the unit voltage Vunit is set to a potential difference that is the smallest of potential differences obtained by subtracting the drain-source voltage Vds _ k +1 (> Vds _ k) of the (k +1) th gray scale from the drain-source voltage Vds _ k (positive voltage value) of the kth gray scale (k is an integer, the larger the luminance gray scale is), of the transistor Tr 13. In the thin film transistor such as the transistor Tr13, particularly, the amorphous silicon TFT, if combined with the organic EL element OLED in which the emission luminance increases substantially linearly with respect to the current density of the flowing current, generally, the higher the gradation, that is, the higher the drain-source voltage Vds, that is, the higher the drain-source current Ids, the smaller the potential difference between adjacent gradations. In other words, when the 256-gray scale voltage gray scale control is performed (the 0 th gray scale is made to emit no light), the potential difference between the voltage Vds of the highest-luminance gray scale (for example, the 255 th gray scale) and the voltage Vds of the 254 th gray scale is the smallest among the potential differences between the adjacent gray scales. Therefore, the unit voltage Vunit is preferably a value obtained by subtracting the drain-source voltage Vds of the highest luminance gradation (or a level in the vicinity thereof) from the drain-source voltage Vds of the next luminance gradation of the highest luminance gradation (or a level in the vicinity thereof).

The voltage adjustment section 144 adds the original gradation voltage Vorg output from the gradation voltage generation section 142 and the offset voltage Vofst output from the offset voltage generation section 143, and outputs the resultant to the data lines Ld arranged in the column direction of the display panel 110 via the current comparison section 145. Specifically, in the correction data obtaining operation, the offset voltage Vofst generated based on the offset setting value optimized by the above-described appropriate modulation is logically added to the original gradation voltage Vorg _ x corresponding to the predetermined gradation (x gradation) output from the gradation voltage generating unit 142, and a voltage component obtained by summing the offset voltage Vofst and the original gradation voltage Vorg _ x is output to the data line Ld as the detection voltage Vdet.

In the writing operation, the correction gradation voltage Vpix is a value satisfying the following expression (2).

Vpix＝Vorg+Vofst……(12)

That is, the offset voltage Vofst generated by the offset voltage generating unit 143 based on the correction data retrieved from the frame memory 146 is logically (when the gradation voltage generating unit 142 has a D/a converter) or digitally added to the original gradation voltage Vorg corresponding to the display data output from the gradation voltage generating unit 142, and a voltage component constituted by the sum of these is output to the data line Ld during the write operation as the correction gradation voltage Vpix.

The current comparing section 145 has a current meter (current measuring circuit) therein, and during the correction data obtaining operation, the detection voltage Vdet generated by the voltage adjusting section 144 is applied to the data line Ld, the current value of the detection current Idet flowing in the data line Ld is measured by a potential difference with the power supply voltage Vcc (Vccw) applied to the power supply voltage line Lv, and an expected current Iref _ x (for example, a current value required to cause the organic EL element OLED to emit light at the maximum luminance gradation) composed of the current value and a predetermined current value of a predetermined gradation x (for example, the maximum luminance gradation) set in advance is compared with each other, and the magnitude relationship (comparison determination result) is output to the bias voltage generating section 143.

The expected current value Iref _ x corresponds to a current value of a current Ids flowing between the drain and the source of the driving transistor Tr13 of the pixel driving circuit DC when a voltage obtained by subtracting the unit voltage Vunit from the detection voltage Vdet is applied to the data line Ld in a state where the driving transistor (driving element, 1 st switching circuit) Tr13 of the pixel driving circuit DC is in an initial state and an initial characteristic is maintained in which a change in element characteristics due to a driving process hardly occurs. As described above, when the voltage difference between the drain-source voltages Vds of the adjacent gradations is used as the unit voltage Vunit, the current value of the current Ids flowing between the drain and the source of the driving transistor Tr13 maintaining the initial characteristic state when the gradation voltage 1 gradation lower than the detection voltage Vdet is applied to the data line Ld becomes the expected current value Iref.

Here, the expected current value Iref may be stored in a memory provided in the current comparing unit 145 or the data driver 140, or may be temporarily stored in a register provided in the data driver 140 by being supplied from the system controller 150, for example. In the write operation, the corrected gradation voltage Vpix generated by the voltage adjustment unit 144 is applied to the display pixel PIX through the data line Ld, and the measurement of the detection current and the comparison with the expected current are not performed. Therefore, for example, the bypass current comparing unit 145 may be further configured during the write operation.

In the correction data obtaining operation performed before the writing operation of writing the display data (the correction gradation voltage Vpix) into each display pixel PIX arranged on the display panel 110, the frame memory 146 sequentially obtains the offset setting value Minc of the display pixel PIX for each row set in the offset voltage generating unit 143 provided for each column by the shift register/data register unit 141, stores the offset setting value Minc as the correction data in each area of each display pixel PIX for each screen (1 frame) of the display panel, and sequentially outputs the correction data of the display pixel PIX for each 1 row to the offset voltage generating unit 143 by the shift register/data register unit 141 in the writing operation.

(System controller)

The system controller 150 generates and outputs a selection control signal, a power supply control signal, and a data control signal for controlling the operation state for each device such as the selection driver 120, the power supply driver 130, and the data driver 140, operates each driver at a predetermined timing, generates and outputs a selection signal Ssel, a power supply voltage Vcc, a detection voltage Vdet, and a correction gradation voltage Vpix having a predetermined voltage level, performs a series of drive control operations (a correction data acquisition operation, a write operation, a hold operation, and a light emission operation) for each display pixel PIX (pixel drive circuit DC), and controls the display of predetermined image information based on an image signal on the display panel 110.

(display Signal generating Circuit)

The display signal generation circuit 160 extracts a luminance gradation signal component from an image signal supplied from the outside of the display device 100, for example, and supplies the luminance gradation signal component to the data driver 140 as display data (luminance gradation data) made of a digital signal every 1 line of the display panel 110. Here, when the image signal includes a timing signal component that defines the display timing of the image information, such as a television transmission signal (composite image signal), the display signal generation circuit 160 may have a function of extracting the timing signal component in addition to the function of extracting the luminance gradation signal component, and may provide the system controller 150 with the extracted timing signal component. At this time, the system controller 150 generates control signals for supplying the selection driver 120, the power supply driver 130, and the data driver 140, respectively, based on the timing signal supplied from the display signal generation circuit 160.

< method for driving display device >

Next, a method of driving the display device of the present embodiment will be described.

The drive control operation of the display device 100 of the present embodiment generally includes the following operations: a correction data acquiring operation of detecting an offset voltage Vofst (strictly speaking, a detection voltage Vdet and a detection current Idet) corresponding to a change in element characteristics (threshold voltage) of a transistor Tr13 (drive transistor) for a light-emitting driver of each display pixel PIX (pixel drive circuit DC) arranged on the display panel 110, and storing an offset set value (specific value) for generating the offset voltage Vofst in the frame memory 146 as correction data for each display pixel PIX; in the display driving operation, the original gradation voltage Vorg corresponding to the display data is corrected based on the correction data acquired in each display pixel PIX, and written as the correction gradation voltage Vpix in each display pixel PIX, and stored as a voltage component, and based on the voltage component, the light emission driving current Iem having a current value corresponding to the display data for compensating the influence of the element characteristic change of the transistor Tr13 is supplied to the organic EL element OLED, and light is emitted at a predetermined luminance gradation. These correction data acquisition operations and display driving operations are performed based on various control signals supplied from the system controller 150.

Hereinafter, each operation will be specifically described.

(correction data obtaining operation)

Fig. 11 is a flowchart showing an example of the correction data acquiring operation of the display device according to the present embodiment.

Fig. 12 is a conceptual diagram illustrating a correction data acquiring operation of the display device according to the present embodiment.

As shown in fig. 11, in the correction data acquiring operation (offset voltage detecting operation: step 1) of the present embodiment, first, the offset setting value minic (initial time minic is 0) of the display pixel PIX in the ith row (1. ltoreq. i.ltoreq.n) is read from the frame memory 146 into the offset voltage generating section 143 via the shift register/data register section 141 (step S111), and then, in the same manner as the writing operation of the pixel drive circuit DCx, the power supply voltage Vcc (Vccw. ltoreq. reference voltage Vss; 1 st voltage) which is the writing operation level, is a low potential, is applied from the power supply driver 130 to the power supply voltage line Lv connected to the display pixel PIX in the ith row (1. ltoreq. i.ltoreq.n, positive integer in the present embodiment, the power supply voltage line Lv connected to all the display pixels PIX in the group including the ith row is connected in common, the selection driver 120 applies the selection signal Ssel of the selection line in the ith row, the display pixels PIX in the ith row are set to the selected state (step S112).

Accordingly, the transistor Tr11 provided in the pixel drive circuit DC of the display pixel PIX in the i-th row is turned on, the transistor Tr13 (drive transistor) is set to a diode connection state, the power supply voltage Vcc (Vccw) is applied to the drain terminal and the gate terminal (the contact N11; one end side of the capacitor Cs) of the transistor Tr13, the transistor Tr12 is also turned on, and the source terminal (the contact N12; the other end of the capacitor Cs) of the transistor Tr13 is electrically connected to each column data line Ld.

Next, the offset voltage Vofst is set based on the offset set value Minc input to the offset voltage generator 143, as shown in the above equation (1) (step S113). Here, the offset voltage Vofst generated by the offset voltage generating unit 143 is calculated by multiplying the offset set value Minc by the unit voltage Vunit (Vofst is Vunit × Minc), and therefore, initially, when there is no threshold shift, the offset set value Minc output from the frame memory 146 is 0, and the initial value of the offset voltage Vofst is 0V.

The voltage adjustment unit 144 adds the offset voltage Vofst output from the offset voltage generation unit 143 to the original gradation voltage Vorg _ x corresponding to the predetermined gradation (x gradation) output from the gradation voltage generation unit 142 in accordance with the display data according to the following expression (13) to generate a detection voltage vdet (p) (step S114), and applies the detection voltage vdet to each data line Ld arranged in the column direction of the display panel 110 by the current comparison unit 145 as shown in fig. 12 (step S115).

Vdet(p)＝Vofst(p)+Vorg_x……(13)

Here, p in vdet (p) and vofst (p) is an offset setting number of the correction data acquisition operation, and is a natural number, and the values sequentially increase according to a change in the offset setting value described later. Therefore, vofst (p) is a variable consisting of negative values whose absolute values increase as p increases, and vdet (p) is a variable consisting of negative values whose absolute values increase as vofst (p) increases, that is, as p increases.

Therefore, since the transistor Tr12 applies the detection voltage Vdet (═ Vofst + Vorg _ x) to the source terminal (contact N12) of the transistor Tr13 and the low-potential power supply voltage Vccw to the gate terminal (contact N11) and the drain terminal of the transistor Tr13, a voltage component (| Vdet-Vccw |) corresponding to the difference between the detection voltage Vdet and the power supply voltage Vccw is applied between the gate and the source of the transistor Tr13 (both ends of the power supply Cs), and the transistor Tr13 performs the on operation.

Here, if it is designed that the voltage value (theoretical value) of the original gradation voltage Vorg _ x outputted by the upper gradation voltage generation unit 142 is such that the display pixel PIX (organic EL element OLED) instructed by the detection target of the offset voltage Vofst corresponding to the change of the threshold voltage Vth of the transistor Tr13 can perform a light emission operation with an arbitrary luminance gradation (for example, x gradation), the detection voltage Vdet obtained by adding the offset voltage Vofst is set to a voltage value having a negative polarity with respect to the power supply voltage Vccw of the write operation level (low level) applied from the power supply driver 130 to the display pixel PIX (Vdet Vofst + Vorg _ x < Vccw ≦ 0). The display data for specifying the gradation (x gradation) of the original gradation voltage Vorg _ x may be stored in the gradation voltage generating section 142 in advance, or may be input from the outside of the data driver 140.

Next, in a state where the detection voltage Vdet is applied to the data line Ld from the voltage adjustment unit 144, the current value of the detection current Idet flowing through the data line Ld is measured by a current meter provided in the current comparison unit 145 (step S116). Here, the voltage relationship of the display pixel PIX is such that the detection voltage Vdet having a lower potential than the low potential power supply voltage Vccw applied to the power supply voltage line Lv is applied to the data line Ld, and therefore the detection current Idet flows from the display pixel PIX side toward the data driver 140 (voltage adjustment section 144) through the data line Ld.

Next, a current comparison process is performed to compare the current value of the detection current Idet measured by the ammeter in the current comparison unit 145 with the design value of the current (expected current Iref) flowing in the data line Ld when the display pixel PIX (organic EL element OLED) is caused to perform a light emission operation with the above-described arbitrary luminance gradation (for example, x gradation), and the comparison determination result (magnitude relation) is output to the bias voltage generation unit 143 (step S117). Here, the comparison process of the detected current Idet and the expected current Iref for x gradation by the current comparing section 145 is to compare and determine whether or not the detected current Idet is also smaller than the expected current Iref (Idet < Iref).

When the detection current Idet is also smaller than the expected current Iref _ x, if the detection voltage vdet (p) is applied to the data line Ld as the correction gradation voltage Vpix while keeping it unchanged during the write operation, a current lower than the gradation to be originally displayed may flow between the drain and the source of the transistor Tr13 due to the influence of the threshold shift caused by the transistor Tr12 and the V-I characteristic line SPw2 of the transistor Tr 13.

Therefore, when the detected current Idet is smaller than the expected current Iref _ x, the current comparing unit 145 outputs a comparison determination result (for example, a positive voltage signal) obtained by increasing the counter value of the bias voltage generating unit 143 by 1 to the counter of the bias voltage generating unit 143.

If the counter value of the offset voltage generator 143 increases by 1, the offset voltage generator 143 adds 1 to the offset set value Minc (step S118), and based on the added offset set value Minc, the process returns to step S113 again to generate Vofst (p + 1). Therefore, Vofst (p +1) is a negative value satisfying the following equation (14).

Vofst(p+1)＝Vofst(p)+Vunit…(14)

Thereafter, the steps from step S114 are repeated until the detected current Idet is larger than the expected current Iref _ x in step S117.

In step S117, when the detected current Idet is larger than the expected current Iref _ x, a comparison determination result (for example, a negative voltage signal) that the counter value of the bias voltage generating unit 143 does not increase is output to the counter of the bias voltage generating unit 143.

When the comparison determination result (negative voltage signal) is put in the counter, the bias voltage generator 143 regards the detection voltage vdet (p) as the threshold shift potential due to the V-I characteristic line SPw2 of the transistor Tr12 and the transistor Tr13 being corrected, and outputs the detection voltage vdet (p) at that time as the corrected gradation voltage Vpix applied to the data line Ld and the gradation bias setting value minic at that time as correction data to the shift register data register unit 141. In the shift register/data register unit 141, the gradation offset setting value Minc of the correction data constituting each column is transferred to the frame memory 146, and the acquisition of the correction data is completed (step S119).

Then, the frame memory 146 outputs the accumulated gradation offset setting value Minc to the offset voltage generator 143 when performing either the correction data acquisition operation or the writing operation.

Next, after the correction data is acquired for the display pixels PIX in the ith row, in order to perform the series of processing operations also for the display pixels PIX in the next row (i +1 th row), processing is performed to increase the variable "i" for specifying the row (i ═ i +1) (step S120). Here, whether or not the variable "i" subjected to the increment processing is smaller than the total number of lines n set on the display panel 110 (i < n) is compared and determined (step S121).

In the comparison of the variables for specifying the row in step S121, when it is determined that the variable "i" is smaller than the number of rows n (i < n), the processes from step S112 to step S121 are performed again, and the same process is repeated until it is determined that the variable "i" and the number of rows n match in step S121 (i ═ n).

In step S121, when it is determined that the variable "i" and the number of lines n match (i ═ n), the correction data acquisition operation for each line of the display pixels PIX is performed for all the lines of the display panel 110, the correction data for each display pixel PIX is stored in each of the predetermined storage areas of the frame memory 146, and the series of correction data acquisition operations is terminated.

In addition, since the potentials of the terminals satisfy the relationships (3) to (10) during the correction data acquisition operation, no current flows in the organic EL element OLED, and no light emission operation is performed.

In this way, in the correction data obtaining operation, as shown in fig. 12, when the detection current Idet flowing when the detection voltage Vdet is applied to the data line Ld is measured, the drain-source current Ids _ x of the transistor Tr13 at the x-gradation level corresponding to the V-I characteristic line SPw in the initial state is set as an expected value, the offset voltage Vofst for flowing the drain-source current Ids of the transistor Tr13 approximate to the expected value is set in the writing operation, and the gradation offset set value Minc at the offset voltage Vofst is stored in the frame memory 146 as the correction data.

In short, the voltage adjustment unit 144 adds the offset voltage vofst (p) of the negative potential corresponding to the gradation offset setting value Minc from the offset voltage generation unit 143 and the original gradation voltage Vorg _ x of the negative potential of the x gradation from the gradation voltage generation unit 142 according to equation (13) to generate the detection voltage vdet (p), and stores the gradation offset setting value Minc of the detection voltage vdet (p) in the frame memory 146 so that the potential of the detection voltage vdet (p) is treated as the corrected gradation voltage Vpix applied to the data line Ld if the detection voltage vdet (p) is corrected so as to be approximated to the drain-source current Ids _ x of the expected value of the transistor Tr13 in the write operation.

In addition, although the gradation voltage generating unit 142 generates the original gradation voltage Vorg _ x based on the display data of each of the display pixels PIX supplied from the display signal generating circuit 160, the original gradation voltage Vorg _ x for adjustment may be set to a fixed value, and the gradation voltage generating unit 142 may output the original gradation voltage Vorg _ x for adjustment without supplying the display data from the display signal generating circuit 160. As described above, the potential of the adjustment original gray-scale voltage Vorg _ x at this time is preferably such that the expected current Iref _ x is a current at which the organic element OLED emits light at the highest luminance gray scale (or a gray scale in the vicinity thereof) during the light emission operation.

In the above embodiment, the display device 100 is a current draw-in type display device in which the drain-source current Ids of the transistor Tr13 flows from the display transistor Tr13 to the data driver 140, and therefore the unit voltage vuit is a negative value, but if the drain-source current Ids of the transistor flows from the data driver to the transistor connected in series to the organic EL element OLED, the unit voltage vuit is a positive value.

(display drive action)

Next, a display driving operation of the display device of the present embodiment will be described.

Fig. 13 is a timing chart showing an example of a display driving operation of the display device according to the present embodiment.

For the sake of convenience of explanation, a timing chart is shown in which, in the display pixels PIX arranged in a matrix on the display panel 110, display pixels PIX in i rows and j columns and (i +1) rows and j columns (i is a positive integer of 1 ≦ i ≦ n, and j is a positive integer of 1 ≦ j ≦ m) are caused to emit light at a luminance gradation corresponding to display data.

Fig. 14 is a flowchart showing an example of the writing operation of the display device according to the present embodiment.

Fig. 15 is a conceptual diagram illustrating a writing operation of the display device according to the present embodiment.

Fig. 16 is a conceptual diagram illustrating a holding operation of the display device according to the present embodiment.

Fig. 17 is a conceptual diagram illustrating a light emitting operation of the display device according to the present embodiment.

The display driving operation of the display device 100 according to the present embodiment is set to perform at least the following operations in a predetermined display driving period (1 processing cycle period) Tcyc as shown in fig. 13, for example, in the same manner as the driving method of the pixel driving circuit DCx described above: a write operation (write operation period Twrt) for generating a corrected gradation voltage Vpix by adding an offset voltage Vofst generated by setting the correction data stored in the frame memory 146 to an offset set value Minc and an original gradation voltage Vorg corresponding to display data for each of the display pixels PIX supplied from the display signal generation circuit 160, and supplying the corrected gradation voltage Vpix to each of the display pixels PIX through each of the data lines Ld; a holding operation (a holding operation period Thld) of charging the capacitance Cs with a voltage component corresponding to the correction gradation voltage Vpix set between the gate and the source of the transistor Tr13 provided in the pixel drive circuit DC of the display pixel PIX by the writing operation and holding the voltage component; in the light emission operation (light emission operation period Tem), a light emission drive current Iem having a current value corresponding to display data is caused to flow into the organic EL element OLED based on the voltage component held in the capacitor Cs by the holding operation, and light is emitted at a predetermined luminance gradation (Tcyc ≧ Twrt + Thld + Tem).

Here, the 1 processing cycle period employed in the display drive period Tcyc of the present embodiment is set to a period required for the display pixel PIX to display image information of 1 pixel in the 1-frame image, for example. In other words, in the display panel 110 in which a plurality of display pixels PIX are arranged in a matrix in the row direction and the column direction, when displaying 1 frame image, the 1 processing cycle period Tcyc is set to a period required for the 1-line display pixels PIX to display 1 line image in the 1 frame image.

(write action)

In the writing operation (writing operation period Twrt), first, as shown in fig. 13, the power supply voltage line Lv connected to the display pixels PIX in the i-th row is applied with the selection signal Ssel at the selection level (high level) to the selection line Ls in the i-th row in a state where the power supply voltage Vcc (Vccw ≦ Vss: the 1 st voltage) at the writing operation level (0V or negative voltage) is applied, and the display pixels PIX in the i-th row are set in the selected state. Accordingly, the transistor Tr11 (holding transistor) and the transistor Tr12 provided in the pixel drive circuit DC are turned on, the transistor Tr13 (drive transistor) is set to a diode-connected state, the power supply voltage Vcc is applied to the drain terminal and the gate terminal of the transistor Ttr13, and the source terminal is connected to the data line Ld.

At the same time, the correction gradation voltage Vpix corresponding to the display data is applied to the data line Ld. Here, the corrected gradation signal Vpix is generated based on a series of processing operations (gradation voltage correcting operation) shown in fig. 14, for example.

In other words, as shown in fig. 14, first, the luminance gradation value of the display pixel PIX to be subjected to the write operation is acquired from the display data supplied from the display signal generation circuit 160 (step S211), and it is determined whether or not the luminance gradation value is "0" (step S212). In the gradation value determination operation in step S212, when the luminance gradation value is "0", the predetermined gradation voltage (black gradation voltage) Vzero for performing the non-light emission operation (or the black display operation) is output from the gradation voltage generation section 142, and is applied to the data line Ld without being added to the offset voltage Vofst by the voltage adjustment section 144 (that is, without performing the compensation process for the threshold voltage variation of the transistor Tr13) (step S213). Here, the gradation voltage Vzero for the non-light emitting operation is set to a voltage value having a relationship of (-Vzero < Vth-Vccw) having a relationship (Vgs < Vth) that the voltage Vgs (≈ Vccw-Vzero) applied between the gate and the source of the diode-connected transistor Tr13 is lower than the threshold voltage Vth of the transistor Tr 13. Here, in order to suppress the threshold shift of the transistor Tr12 and the transistor Tr13, it is preferable that Vzero be Vccw.

In step S212, when the luminance gradation value is not "0", the gradation voltage generating unit 142 generates and outputs the original gradation voltage Vorg having a voltage value corresponding to the luminance gradation value (display data) (step 2), and sequentially reads out the correction data stored in association with each display pixel PIX of the row from the frame memory 146 by the shift register/data register unit 141 (step S214), outputs the correction data to the offset voltage generating unit 143 provided on each column data line Ld, and multiplies the correction data by the unit voltage Vunit to generate the offset voltage Vofst (═ Vunit × Minc) corresponding to the threshold voltage variation of the transistor Tr13 of each display pixel PIX (pixel drive circuit DC) (step S215; step 3).

Then, as shown in fig. 15, the voltage adjustment section 144 adds the original gradation voltage Vorg of the negative potential output from the gradation voltage generation section 142 and the offset voltage Vofst of the negative potential output from the offset voltage generation section 143 according to equation (12) to generate a corrected gradation voltage Vpix of the negative potential (step S216), and then applies the corrected gradation voltage Vpix to the data line Ld (step S217). Here, the corrected gradation voltage Vpix generated by the voltage adjustment section 144 is set to have a voltage amplitude of a relatively negative potential with reference to the power supply voltage Vcc (Vccw) of the write operation level (low potential) applied from the power supply driver 130 to the power supply voltage line Lv. The correction gradation voltage Vpix decreases on the negative potential side (the absolute value of the voltage amplitude increases) as the gradation increases.

Accordingly, since the corrected gradation voltage Vpix corrected by adding the offset voltages Vofst corresponding to the variation of the threshold voltage Vth of the transistor Tr13 is applied to the source terminal (contact N12) of the transistor Tr13, the corrected voltage Vgs is written between the gate and the source of the transistor Tr13 (both ends of the capacitance Cs) (step 4). In such a writing operation, since a desired voltage is directly applied to the gate terminal and the source terminal of the transistor Tr13 without flowing a current corresponding to display data to set a voltage component, the potential of each terminal or contact can be set to a desired state quickly.

In the writing operation period Twrt, the voltage value of the correction gradation voltage Vpix applied to the contact point N12 on the anode terminal side of the organic EL element OLED is set to be lower than the reference voltage Vss applied to the cathode terminal TMc (in other words, the organic EL element OLED is set in a reverse bias state), and therefore no current flows through the organic EL element OLED, and no light emitting operation is performed.

(holding action)

Next, in the holding operation (holding operation period Thld) after the end of the above-described writing operation period Twrt, as shown in fig. 13, by applying the selection signal Ssel at the non-selection level (low level) to the selection line Ls in the i-th row, as shown in fig. 16, the transistor Tr11 and the transistor Tr12 are turned on, the diode connection state of the transistor Tr13 is released, the correction gradation voltage Vpix applied to the source terminal (contact N12) of the transistor Tr13 is turned off, and the voltage component (| Vpix-Vccw |) applied to the gate-source of the transistor Tr13 charges the capacitance Cs and is held.

At this timing, since the selection signal Ssel at the selection level (high level) is applied from the selection driver 120 to the selection line Ls in the (i +1) th row, the writing operation of the correction gradation voltage Vpix is performed in the display pixels PIX in the (i +1) th row in the same manner as in the above case. In this way, during the holding operation period Thld of the display pixels PIX in the ith row, the holding operation is continued until the voltage components (the correction gradation voltages Vpix) corresponding to the display data are sequentially written into the display pixels PIX in the other rows.

(Lighting action)

Next, in a light emitting operation (light emitting operation period Tem; step 5) after the end of the writing operation period Twrt and the holding operation period Thld, as shown in fig. 13, in a state where the selection signal Ssel at the non-selection level (low level) is applied to the selection line Ls in each row, a high potential (positive voltage) power supply voltage (2 nd voltage) Vcc (Vcce > 0V: 2 nd voltage) at the light emitting operation level is applied to the power supply voltage line Lv connected to each row of display pixels PIX.

Here, as in the case shown in fig. 7 and 8, since the high-potential power supply voltage Vec (Vcce) applied to the power supply voltage line Lv is set to be greater than the sum of the saturation voltage (pinch-off voltage Vpo) of the transistor Tr13 and the driving voltage (Voled) of the organic EL element OLED, the transistor Tr13 operates in the saturation region. Further, since the positive voltage corresponding to the voltage component (| Vpix-Vccw |) set between the gate and the drain of the write operation write transistor Tr13 is applied to the anode side (contact N12) of the organic EL element OLED, and the reference voltage Vss (for example, ground potential) is applied to the cathode terminal TMc to set the organic EL element OLED in the forward bias state, as shown in fig. 17, the light emission drive current Iem (gate-drain current Ids of the transistor Tr13) having a current value corresponding to the display data (strictly, corrected gradation voltage; corrected gradation voltage Vpix) is caused to flow from the power supply voltage line Lv through the transistor Tr13 to the organic EL element OLED and is caused to perform the light emission operation at a predetermined luminance gradation.

This light emission operation is continued until the power supply driver 130 applies the power supply voltage Vcc (Vccw) at the write operation level (negative voltage) until the next display drive period (1 processing cycle period) Tcyc starts.

By this series of display driving operations, as shown in fig. 13, in a state where the power supply voltage Vcc (Vccw) at the write operation level is applied to each row of display pixels PIX arranged on the display panel 110, the correction gradation voltage Vpix is written to each row of each row, an operation of holding a predetermined voltage component (| Vpix-Vccw |) is sequentially performed, and the power supply voltage Vcc (Vcce) at the emission operation level is applied to the display pixels PIX of the row in which the write operation and the holding operation have ended, thereby enabling the display pixels PIX of the row to emit light.

For example, when all the display pixels PIX in each group are caused to emit light at once after the writing operation of the display pixels PIX in all the rows in each group described below is completed, the holding operation is set between the writing operation and the light emitting operation. At this time, the lengths of the holding operation periods Thld of the respective lines are different. In addition, when such drive control is not performed, the holding operation may not be performed.

Here, in the display device 100 of the present embodiment, as shown in fig. 9, the display pixels PIX arranged on the display panel 110 are grouped into 2 groups each consisting of an upper region and a lower region of the display panel 110, and the power supply voltage Vec is applied to each group via the branched power supply voltage lines Lv, so that the display pixels PIX of a plurality of rows included in each group can be caused to emit light all at once. A specific drive control operation at this time will be described below.

Fig. 18 is an operation timing chart schematically showing a specific example of the driving method of the display device according to the present embodiment.

For the sake of convenience of explanation, fig. 18 shows an operation timing chart in which 12 rows (12, 1 st to 12 th rows) of display pixels are arranged on a display panel, and display pixels in the 1 st to 6 th rows (corresponding to the above-described upper region) and the 7 th to 12 th rows (corresponding to the above-described lower region) are grouped into 2 groups.

As shown in fig. 18, the drive control operation of the display device 100 including the display panel 110 shown in fig. 9 is such that the above-described correction data acquisition operation is sequentially performed for each of the rows at a predetermined timing for all the display pixels PIX arranged on the display panel 110, and after the correction data acquisition operation for all the rows of the display panel 110 is completed (that is, after the correction data acquisition operation period Tdet is completed), a correction gradation voltage obtained by adding the original gradation voltage Vorg corresponding to the display data and the offset voltage Vofst corresponding to the element characteristic change of the drive transistor (transistor Tr13) of each display pixel PIX is written to the display pixels PIX (pixel drive circuit DC) for each row of the display panel 110 within 1 frame period Tfr, and an operation of holding a predetermined voltage component (| Vpix-Vccw |) is sequentially repeated for all the rows, and the display pixels PIX (organic elements EL) are grouped in the 1 to 6 th rows or 7 to 12 th rows in advance OLED), a display driving operation (a display driving period Tcyc shown in fig. 13) is repeated in which all the display pixels PIX included in the group emit light at the same time with a luminance gradation corresponding to the display data (the correction gradation voltage Vpix), and image information of one screen of the display panel 110 is displayed.

Specifically, in the group of the display pixels PIX arranged in the display panel 110, in a state where the low-potential power supply voltage Vcc (Vccw) is applied to each group via the power supply voltage line Lv commonly connected to the display pixels PIX, the correction data obtaining operation (correction data obtaining operation period Tdet) is sequentially performed from the display pixels PIX in the 1 st row, and the correction data corresponding to the change in the threshold voltage of the transistor Tr13 (drive transistor) provided in the pixel drive circuit DC is stored (stored) in a predetermined region of the frame memory 146 for each of the display pixels PIX arranged in the display panel 110.

Next, after the correction data obtaining operation period Tdet is completed, in a group of display pixels PIX in rows 1 to 6, the writing operation (writing operation period Twrt) and the holding operation (holding operation period Thld) are sequentially performed from the display pixel PIX in row 1 in a state where the low-potential power supply voltage Vcc (Vccw) is applied via the power supply voltage line Lv commonly connected to the display pixels PIX in the group, and the display pixels PIX in row 6 are switched so that the high-potential power supply voltage Vcc (Vcce) is applied via the power supply voltage line Lv in the group at a timing when the writing operation for the display pixels PIX in row 6 is completed, thereby performing the light emitting operation for the display pixels PIX in row 6 of the group at a luminance gradation based on the display data (correction gradation voltage Vpix) written in each display pixel PIX. This light emission operation continues until the timing of starting the next write operation to the display pixel PIX in row 1 (light emission operation period Tem in rows 1 to 6).

Then, at the timing when the writing operation to the display pixels PIX of the 1 st to 6 th rows is finished, in a group of display pixels PIX in rows 7 to 12, a low-potential power supply voltage Vcc (Vccw) is applied via a power supply voltage line Lv commonly connected to the display pixels PIX in the group, and the writing operation (writing operation period Twrt) and the holding operation (holding operation period Thld) are sequentially performed from the display pixel PIX in row 7, switching is performed at the timing when the writing operation to the display pixel PIX in the 12 th row is completed, so that a high-potential power supply voltage Vcc (Vcce) is applied through the power supply voltage line Lv of the group, thus, the display pixels PIX of 6 rows in the group are caused to perform a light emission operation (light emission operation period Tem of 7 th to 12 th rows) at the same time with a luminance gradation based on the display data (correction gradation voltage Vpix) written in each display pixel PIX. During the write operation and the hold operation for the display pixels PIX in the 7 th to 12 th rows, as described above, the high-potential power supply voltage Vcc (Vcce) is applied to the display pixels PIX in the 1 st to 6 th rows via the power supply voltage line Lv, and the operation of emitting light in unison is continued.

In this way, after the correction data acquiring operation is performed for all the display pixels PIX arranged on the display panel 110, the writing operation and the holding operation are sequentially performed for each row of the display pixels PIX at a predetermined timing, and the drive control is performed for each set group so that all the display pixels PIX of the set group perform the light emitting operation at once at a timing at which the writing operation performed for the display pixels PIX of all the rows included in the set group is completed.

Therefore, in the display device driving method (display driving operation) as described above, in the 1-frame period Tfr, during the writing operation for each row of display pixels in the same group, the light emission operation for all the display pixels (light emitting elements) in the group is not performed, and the non-light emission state (black display state) can be set. Here, in the operation timing chart shown in fig. 18, the 12 rows of display pixels PIX constituting the display panel 110 are divided into 2 groups and controlled so that the groups perform the light emission operation at the same time at different timings, and therefore the ratio of the black display period (black insertion rate) in the above-described non-light emission operation in the 1 frame period Trf can be set to 50%. Here, in order to clearly view a moving image without blurring in human vision, generally, a black insertion rate of about 30% or more is aimed, so that a display device with good display quality can be realized by the present driving method.

In addition, although the present embodiment (fig. 9) shows a case where each continuous row of the plurality of display pixels PIX arranged on the display panel 110 is divided into 2 groups, the present invention is not limited to this, and may be divided into any number of groups such as 3 groups or 4 groups, or may be divided into discontinuous rows such as even-numbered rows and odd-numbered rows. Therefore, the light emission timing and the black display period (black display state) can be arbitrarily set according to the number of groups of the packets, and the display quality can be improved.

Further, instead of grouping the plurality of display pixels PIX arranged on the display panel 110 as described above, the display pixels PIX may be operated to emit light in each row by providing (connecting) the power supply voltage lines to each row and independently applying the power supply voltage Vcc at different timings, or all the display pixels PIX of one screen arranged on the display panel 110 may be operated to emit light in all the display pixels PIX of one screen by applying the common power supply voltage Vcc to all the display pixels PIX of one screen in all the rows.

As described above, the display device and the driving method thereof according to the present embodiment can employ a voltage-designating type (or voltage-applying type) gradation method in which the correction gradation voltage Vpix designating the voltage value corresponding to the display data and the change in the element characteristics (threshold voltage) of the driving transistor is directly applied between the gate and the source of the driving transistor (transistor Tr13) during the writing operation of the display data, a predetermined voltage component is held in the capacitor (capacitor Cs), and the light emission driving current Iem flowing into the light emitting element (organic EL element OLED) is controlled based on the voltage component to emit light with a desired luminance gradation.

Therefore, compared with a current-specifying gradation method in which a current corresponding to display data is supplied and a writing operation (holding a voltage component corresponding to the display data) is performed, even when the display panel is increased in size and made finer in definition or when low-gradation display is performed, a gradation signal (correction gradation voltage) corresponding to the display data can be quickly and reliably written to each display pixel, so that occurrence of insufficient writing of the display data can be suppressed, a light emitting operation can be performed at an appropriate luminance gradation corresponding to the display data, and good display quality can be achieved.

Further, since the corrected gradation signal (corrected gradation voltage) of each display pixel can be generated and applied based on the correction data when the correction data corresponding to the change in the threshold voltage of the drive transistor provided in each display pixel is acquired and the writing operation is performed before the display driving operation including the writing operation, the holding operation, and the light emitting operation of the display data is performed on the display pixel (pixel driving circuit), the influence (shift in the voltage-current characteristic of the drive transistor) due to the change in the threshold voltage can be compensated, and each display pixel (light emitting element) can be caused to emit light with an appropriate luminance gradation corresponding to the display data, and thus variation in the light emitting characteristic of each display pixel can be suppressed, and the display quality can be improved.

Claims (46)

1. A display driving device for driving a display pixel including a light emitting element and a driving element in accordance with display data, comprising:

a specific value detection circuit that detects a specific value corresponding to a variation amount of an element characteristic of the drive element based on a current value of a current flow path flowing through the drive element when a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the drive element of adjacent gray scales of the display data is applied to the display pixel;

and a gradation voltage correction circuit which corrects a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to display data based on a compensation voltage based on the specific value and the unit voltage, generates a corrected gradation voltage, and supplies the corrected gradation voltage to the display pixel.

2. The display driving device according to claim 1, further comprising:

and a storage circuit for storing the specific value detected by the specific value detection circuit as correction data.

3. The display drive device according to claim 2, wherein:

the gradation voltage correction circuit reads the correction data from the memory circuit, and generates the correction gradation voltage based on the read correction data.

4. The display driving device according to claim 3, further comprising:

a gradation voltage generation circuit that generates the gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to display data; and

a compensation voltage generation circuit that generates the compensation voltage for compensating for a variation in the element characteristic of the drive element, based on a specific value corresponding to the correction data read from the memory circuit;

the compensation voltage generation circuit generates a voltage component by multiplying the specific value by the unit voltage as the compensation voltage;

the gradation voltage correction circuit adds the compensation voltage generated by the compensation voltage generation circuit and the gradation voltage generated by the gradation voltage generation circuit to each other to obtain a value as the corrected gradation voltage.

5. The display driving device according to claim 2, wherein the specific value detection circuit includes:

a current comparison circuit that detects a current value of a current flowing through the current flow path of the drive element when the detection voltage is applied to the display pixel, and compares the detected current value with an expected current value corresponding to an expected value of the current flowing through the current flow path of the drive element when a voltage obtained by subtracting the unit voltage from the detection voltage is applied to the display pixel;

an offset voltage setting circuit that reads the correction data from the memory circuit, sets an offset voltage to a value based on an offset set value corresponding to the read correction data and the unit voltage, performs processing to change or not change the offset set value based on a comparison result of the current comparison circuit comparing the detected current value with the expected current value, sets the offset set value, and updates and sets the offset voltage value to a value based on the offset set value and the unit voltage value after the setting;

a detection voltage setting circuit that sets a voltage value of the detection voltage to a value based on the offset voltage value set in the offset voltage setting circuit; and

and a specific value extracting circuit that extracts the bias set value set in the bias voltage setting circuit as the specific value.

6. The display drive device according to claim 5, wherein:

the offset voltage setting circuit sets the offset set value to a value corresponding to the correction data read from the memory circuit without changing the offset set value when the current value of the detected current is determined to be equal to or greater than the expected current value in the comparison by the current comparison circuit.

7. The display drive device according to claim 5, wherein:

in the above-described configuration, the offset voltage setting circuit changes the offset setting value to a value after the increase when the detected current value is determined to be smaller than the expected current value in the comparison by the current comparison circuit, and sets a voltage component obtained by multiplying the changed offset setting value by the unit voltage as the offset voltage.

8. The display drive device according to claim 7, wherein:

the detection voltage setting circuit sets the voltage value of the detection voltage to a value obtained by adding a voltage component obtained by multiplying the offset set value by the unit voltage to an initial value of the detection voltage,

an initial value of the detection voltage setting circuit is a voltage value of the gradation voltage for causing the light emitting element to perform a light emitting operation with a specific 1 st gradation;

the unit voltage is a voltage corresponding to a potential difference between the 1 st gray scale and the 2 nd gray scale lower than the specific gray scale of the gray scale voltage;

the expected current value is an expected value of a current flowing through the current flow path of the driving element when the gradation voltage of the 2 nd gradation is applied to the display pixel with the driving element maintaining initial characteristics.

9. The display drive device according to claim 8, wherein:

the 1 st gray scale is the highest gray scale set in the light emitting element.

10. A display device for displaying image information corresponding to display data, comprising:

a display panel in which a plurality of display pixels including light emitting elements and driving elements for supplying current flowing in current flow paths to the light emitting elements are arranged in the vicinity of intersections of a plurality of selection lines and data lines arranged in a row direction and a column direction;

a selection driving section that sequentially applies a selection signal to each of the plurality of selection lines at a predetermined time and sets the display pixels in each row to a sequentially selected state;

a data driving section for generating a gradation signal corresponding to the display data and supplying the gradation signal to each of the display pixels in the row set to the selected state through each of the data lines;

the data driving unit includes at least:

a specific value detection circuit that detects a specific value corresponding to a variation amount of an element characteristic of each of the driving elements of the plurality of display pixels based on a current value of a current flow path flowing through the driving element of each of the display pixels when a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gradations of the display data is applied to each of the display pixels through each of the data lines;

and a gradation voltage correction circuit which corrects a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to the display data based on the compensation voltage based on the specific value and the unit voltage to generate a corrected gradation voltage, and supplies the corrected gradation voltage to each display pixel through each data line as the gradation signal.

11. The display device according to claim 10, wherein:

the specific value detection circuit detects the specific value for all of the plurality of display pixels;

the display device further includes a memory circuit that stores the detected specific value as correction data in correspondence with each of the plurality of display pixels.

12. The display device according to claim 11, wherein:

the gradation voltage correction circuit reads out the correction data corresponding to each of the display pixels of the row set to the selected state from the memory circuit, and generates the correction gradation voltage based on the read-out correction data.

13. The display device according to claim 12, further comprising:

a gradation voltage generation circuit that generates the gradation voltage having a voltage value for causing the light emitting element to perform a light emitting operation with a luminance gradation corresponding to display data; and

a compensation voltage generation circuit that generates the compensation voltage for compensating for a variation in the element characteristic of the drive element, based on the specific value corresponding to the correction data read from the memory circuit;

a compensation voltage generation circuit that generates a voltage component by multiplying the unit voltage by the specific value corresponding to the correction data read from the memory circuit, as the compensation voltage;

the gradation voltage correction circuit adds the compensation voltage generated by the compensation voltage generation circuit and the gradation voltage generated by the gradation voltage generation circuit to each other to obtain a value as the correction gradation voltage.

14. The display device according to claim 11, wherein the specific value detection circuit comprises:

a current comparison circuit that detects a current value of a current flowing through the current flow path of the driving element of each display pixel when the detection voltage is applied to each display pixel through the data line, and compares the detected current value with an expected current value corresponding to an expected value of a current flowing through the current flow path of the driving element when a voltage obtained by subtracting the unit voltage from the detection voltage is applied to the display pixel;

an offset voltage setting circuit that reads out the correction data corresponding to each of the display pixels of the row set to the selected state from the memory circuit, sets an offset voltage to a value based on an offset set value corresponding to the read-out correction data and the unit voltage, performs a process of changing or not changing the offset set value based on a comparison result of the current comparison circuit comparing the detected current value and the expected current value, sets the offset set value, and updates and sets the offset voltage value to a value based on the offset set value and the unit voltage value after the setting;

a detection voltage setting circuit that sets a voltage value of the detection voltage to a value based on the offset voltage value set in the offset voltage setting circuit; and

and a specific value extracting circuit that extracts the bias set value set in the bias voltage setting circuit as the specific value.

15. The display device according to claim 14, wherein:

the offset voltage setting circuit sets the offset set value to a value corresponding to the correction data read from the memory circuit without changing the offset set value when the detected current value is determined to be equal to or greater than the expected current value in the comparison by the current comparison circuit.

16. The display device according to claim 14, wherein:

the offset voltage setting circuit updates the offset set value to an increased value when the detected current value is determined to be smaller than the expected current value in the comparison by the current comparison circuit, and sets a voltage component obtained by multiplying the updated offset set value by a predetermined unit voltage as the offset voltage.

17. The display device according to claim 16, wherein:

the detection voltage setting circuit sets the voltage value of the detection voltage to a value obtained by adding a voltage component obtained by multiplying the offset set value by the unit voltage to an initial value of the detection voltage,

an initial value of the detection voltage setting circuit is a voltage value of the gradation voltage for causing the light emitting element to perform a light emitting operation with a specific 1 st gradation;

the unit voltage is a voltage corresponding to a potential difference between the 1 st gray scale and the 2 nd gray scale lower than the specific gray scale of the gray scale voltage by 1 gray scale;

the expected current value is an expected value of a current flowing through the current flow path of the driving element when the gradation voltage of the 2 nd gradation is applied to the display pixel with the driving element maintaining initial characteristics.

18. The display device according to claim 17, wherein:

the 1 st gray scale is the highest gray scale set in the light emitting element.

19. The display device according to claim 10, wherein:

the light-emitting element is an organic electroluminescent element.

20. The display device according to claim 10, wherein:

each of the display pixels includes at least a pixel drive circuit, and the pixel drive circuit includes:

a 1 st switching element to which a power supply voltage is applied at one end of a current flow path, the other end of the current flow path being connected to a connection contact of the light emitting element and electrically connected to the data line, and forming the driving element;

a 2 nd switching element to one end of which the power supply voltage is applied and the other end of which is connected to a control terminal of the 1 st switching element; and

a voltage holding element connected between the control terminal of the 1 st switching element and the connection contact;

the display device includes a power supply driving unit for supplying the power supply voltage,

a power supply driving section for setting the power supply voltage to a 1 st voltage for causing the light emitting element to be in a non-emission state and setting the light emitting element to be in a non-emission state during a period in which the specific value is detected by the specific value detecting circuit and during a period in which the corrected gradation voltage is supplied to each display pixel by the gradation voltage correcting circuit,

in the subsequent time, the power supply voltage is set to a 2 nd voltage different from the 1 st voltage, which causes the light emitting element to emit light, and the light emitting element is set to emit light.

21. The display device according to claim 20, wherein:

the 1 st and 2 nd switching elements are field effect transistors each including a semiconductor layer made of amorphous silicon.

22. The display device according to claim 20, wherein:

the display pixel further includes a 3 rd switching element having one end of a current path connected to the data line and the other end connected to the connection contact.

23. The display device according to claim 22, wherein:

the 3 rd switching element is a field effect transistor including a semiconductor layer made of amorphous silicon.

24. The display device according to claim 20, wherein:

the plurality of display pixels are divided into a plurality of groups each having a plurality of rows,

the power supply driving unit sets the power supply voltage applied to one end of the current flow path of the 1 st switching element of the multi-row display pixels of each of the groups to the 2 nd voltage and simultaneously sets the multi-row display pixels of each of the groups to a light-emitting state during a period after the corrected gradation voltage is supplied to the multi-row display pixels of each of the groups.

25. The display device according to claim 20, further comprising:

a connection state control unit for controlling the conduction state of the current flow path of the 2 nd switching element,

a connection state control unit configured to control the current flow path of the 2 nd switching element to be conductive and connect one end of the current flow path of the 1 st switching element to a control terminal when the 1 st voltage is supplied from the power supply driving unit and the light emitting element is set to a non-light emitting state;

when the 2 nd voltage is supplied from the power supply driving unit to set the light emitting element to a light emitting state, the current flow path of the 2 nd switching element is made non-conductive, and the connection between one end of the current flow path of the 1 st switching element and the control terminal of the 1 st switching element is released.

26. A driving method of a display driving apparatus for driving a display pixel having a light emitting element and a driving element in accordance with display data, characterized in that:

applying a detection voltage to the display pixel based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gray scales of the display data;

detecting a specific value corresponding to a variation amount of an element characteristic of the driving element based on a current value flowing through a current flow path of the driving element,

generating a gradation voltage having a voltage value for causing the light emitting element to emit light with a luminance gradation corresponding to display data,

the gradation voltage is corrected based on the compensation voltage based on the specific value and the unit voltage, and a corrected gradation voltage is generated and supplied to the display pixel.

27. The driving method according to claim 26, characterized in that:

the method includes a storing operation of storing the detected specific value as correction data in a memory circuit.

28. The driving method according to claim 27, characterized in that:

the operation of generating the correction gradation voltage includes an operation of reading the correction data from the memory circuit;

the correction gradation voltage is generated based on the read correction data.

29. The driving method according to claim 28, characterized in that:

the operation of generating the correction gradation voltage includes an operation of multiplying the specific value corresponding to the correction data read from the memory circuit by the unit voltage to obtain a voltage component as the compensation voltage;

and adding the compensation voltage and the generated gray scale voltage to obtain a value as the corrected gray scale voltage.

30. The driving method according to claim 27, characterized in that:

the operation of detecting the specific value includes an operation of detecting that the specific value is a value of a predetermined threshold value

Reading the correction data from the memory circuit;

the offset voltage is set to a value based on the offset set value corresponding to the read correction data and the unit voltage,

setting a voltage value of the detection voltage to a value based on the bias voltage value, and applying the voltage value to the display pixel;

detecting a current value of a current flowing through a current flow path of the driving element;

comparing a current value of the detected current with an expected current value corresponding to an expected value of a current flowing through the current flow path of the driving element when a voltage obtained by subtracting the unit voltage from the detected voltage is applied to the display pixel;

changing the offset set value when the comparison determines that the detected current value of the current is smaller than the expected current value; setting the offset set value without changing the offset set value when the detected current value is equal to or greater than the expected current value;

updating and setting the value of the bias voltage to a value based on the set bias value and the unit voltage value;

updating and setting a voltage value of the detection voltage to a value based on the set bias voltage;

and extracting the set offset value as the specific value.

31. The driving method according to claim 30, characterized in that:

the operation of setting the offset setting value includes an operation of setting the offset setting value to a value corresponding to the predetermined value

Changing the value of the offset set value to a value after the increase when the comparison determines that the detected current value of the current is smaller than the expected current value;

the operation of updating the value of the bias voltage includes an operation of updating the value of the bias voltage

And setting a voltage component obtained by multiplying the set offset value by the unit voltage as the offset voltage.

32. The driving method according to claim 30, characterized in that:

the operation of updating the voltage value of the detection voltage includes an operation of updating the voltage value of the detection voltage to a predetermined value

Setting a voltage value of the detection voltage to a value obtained by adding a voltage component obtained by multiplying the changed offset setting value by the unit voltage to an initial value of the detection voltage;

the initial value of the detection voltage is a voltage value of the gradation voltage for causing the light emitting element to perform a light emitting operation at a specific 1 st gradation;

the unit voltage is a voltage corresponding to a potential difference between the 1 st gray scale and the 2 nd gray scale lower than the specific gray scale of the gray scale voltage by 1 gray scale;

the expected current value is an expected value of a current flowing through the current flow path of the driving element when the gradation voltage of the 2 nd gradation is applied to the display pixel with the driving element maintaining initial characteristics.

33. A method of driving a display device for displaying image information corresponding to display data, comprising:

the display device includes a display panel in which a plurality of display pixels each having a light-emitting element and a driving element for supplying a current flowing through a current flow path to the light-emitting element are arranged in the vicinity of each intersection of a plurality of selection lines and data lines arranged in a row direction and a column direction;

the method comprises the following actions:

sequentially applying a selection signal to each of the plurality of selection lines to set the display pixels in each row to a sequentially selected state;

applying a detection voltage based on a unit voltage corresponding to a voltage difference between drain-source voltages of the driving elements of adjacent gray scales of the display data to the display pixels of the selected row through the data lines;

detecting a specific value corresponding to a variation amount of an element characteristic of each of the driving elements based on a current value flowing through a current flow path of the driving element of each of the display pixels;

generating a gradation voltage having a voltage value for causing the light emitting element to perform a light emitting operation with a luminance gradation corresponding to the display data;

generating a compensation voltage based on the specific value and the unit voltage;

the gradation voltage is corrected based on the compensation voltage to generate a corrected gradation voltage, and the corrected gradation voltage is supplied to each display pixel in the selected row through each data line.

34. The driving method according to claim 33, characterized in that:

an operation of detecting the specific value for all of the plurality of display pixels, further comprising a storing operation of storing the detected specific value as correction data in a storage circuit for each of the plurality of display pixels,

the operation of storing the correction gradation voltage in the storage circuit is performed at a timing before the operation of supplying the correction gradation voltage to each display pixel.

35. The driving method according to claim 34, characterized in that:

the operation of generating the corrected gradation voltage and supplying the corrected gradation voltage to each display pixel includes an operation of generating the corrected gradation voltage and supplying the generated corrected gradation voltage to each display pixel

Reading out the correction data corresponding to each of the display pixels of the row set to the selected state from the memory circuit,

the correction gradation voltage is generated based on the correction data.

36. The driving method according to claim 35, wherein:

the operation of generating the corrected gradation voltage and supplying the corrected gradation voltage to each display pixel includes an operation of generating the corrected gradation voltage,

a voltage component obtained by multiplying the unit voltage by the specific value corresponding to the correction data read from the memory circuit is used as the compensation voltage; a value obtained by adding the compensation voltage and the gradation voltage is generated as the correction gradation voltage.

37. The driving method according to claim 34, characterized in that:

the operation of detecting the specific value includes the following operations:

reading the correction data corresponding to each of the display pixels of the row set to the selected state from the memory circuit;

the offset voltage is set to a value based on the offset set value corresponding to the read correction data,

setting a voltage value of the detection voltage to a value based on the bias voltage value, and applying the detection voltage to each display pixel;

detecting a current value of a current flowing through a current flow path of the driving element of each display pixel;

comparing a current value of the detected current with an expected current value corresponding to an expected value of a current flowing through the current flow path of the driving element when a voltage obtained by subtracting the unit voltage from the detected voltage is applied to the display pixel;

changing the offset set value when the comparison determines that the detected current value of the current is smaller than the expected current value; setting the offset set value without changing the offset set value when the detected current value is equal to or greater than the expected current value;

updating and setting the value of the bias voltage to a value based on the set bias value;

updating and setting the voltage value of the detection voltage to a value based on the set bias voltage;

the set offset value is extracted as the specific value.

38. The driving method according to claim 37, characterized in that:

the operation of setting the offset setting value includes an operation of setting the offset setting value to a value equal to or greater than a predetermined value

Changing the value of the offset set value to a value after the increase when the comparison determines that the current value of the detected current is smaller than the expected current value;

the operation of updating the value of the bias voltage includes an operation of updating the value of the bias voltage

And setting a voltage component obtained by multiplying the set offset value by the unit voltage as the offset voltage.

39. The driving method according to claim 38, characterized in that:

the operation of updating the voltage value of the detection voltage includes an operation of updating the voltage value of the detection voltage to a predetermined value

Setting the voltage value of the detection voltage to a value obtained by adding a voltage component obtained by multiplying the changed offset setting value by the unit voltage to an initial value of the detection voltage,

the initial value of the detection voltage is a voltage value of the gradation voltage for causing the light emitting element to perform a light emitting operation at a specific 1 st gradation;

the unit voltage is a voltage corresponding to a potential difference between the 1 st gray scale and the 2 nd gray scale lower than the specific gray scale of the gray scale voltage by 1 gray scale;

the expected current value is an expected value of a current flowing through the current flow path of the driving element when the gradation voltage of the 2 nd gradation is applied to the display pixel with the driving element maintaining initial characteristics.

40. The driving method according to claim 39, wherein:

the 1 st gray scale is the highest gray scale set in the light emitting element.

41. The driving method according to claim 37, characterized in that:

each of the display pixels includes at least a pixel drive circuit, and the pixel drive circuit includes:

a 1 st switching element to which a power supply voltage is applied at one end of a current path, the other end of the current path being connected to a connection contact of the light emitting element and electrically connected to the data line, and constituting the driving element;

a 2 nd switching element to which the power supply voltage is applied at one end of a current flow path, the other end of the current flow path being connected to a control terminal of the 1 st switching element; and

a voltage holding element connected between the control terminal of the 1 st switching element and the connection contact;

the driving method includes the following operations:

setting the power supply voltage to a 1 st voltage having a voltage value for making the light emitting element non-emitting during the operation of detecting the specific value and the operation of generating the correction gradation voltage and supplying the correction gradation voltage to each display pixel;

in the subsequent time, the power supply voltage is set, and the voltage is switched to the 2 nd voltage having a voltage value that causes the light emitting element to be in a light emitting state, thereby setting each of the light emitting elements to be in a light emitting state.

42. The driving method according to claim 41, characterized in that:

the operation of detecting the specific value includes an operation of detecting the specific value

Conducting the current flow path of the 2 nd switching element to electrically connect the control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element;

setting the power supply voltage to the 1 st voltage;

the detection voltage is applied to the other end of the current flow path of the 1 st switching element.

43. The driving method according to claim 41, characterized in that:

the operation of supplying the corrected gradation voltage to each display pixel includes a writing operation

Conducting the current flow path of the 2 nd switching element to electrically connect the control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element;

setting the power supply voltage to the 1 st voltage;

the corrected gradation voltage is applied to the other end of the current flow path of the 1 st switching element.

44. The driving method according to claim 43, wherein:

the operation of supplying the corrected gradation voltage to each of the display pixels further includes a holding operation of holding the corrected gradation voltage

At a time point after the write operation is performed, rendering the current flow path of the 2 nd switching element non-conductive, and electrically disconnecting the control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element;

setting the power supply voltage to the 1 st voltage;

the voltage holding element holds a voltage component corresponding to a potential difference applied to both ends of the current flow path of the 1 st switching element.

45. The driving method according to claim 41, characterized in that:

the operation of setting the light emitting elements to light emitting states includes a light emitting operation of setting the light emitting elements to light emitting states

Rendering the current flow path of the 2 nd switching element non-conductive, and electrically disconnecting the control terminal of the 1 st switching element and one end of the current flow path of the 1 st switching element;

the power supply voltage is set to the 2 nd voltage, and a current corresponding to the voltage component held in the voltage holding element is supplied to each light emitting element.

46. The driving method according to claim 41, characterized in that:

the operation of setting the light emitting elements to emit light includes the following operations:

the plurality of display pixels are divided into a plurality of groups each having a plurality of rows, the power supply voltage applied to one end of the current flow path of the 1 st switching element of the plurality of display pixels of each group is set to the 2 nd voltage, and the light emitting elements of the plurality of display pixels of each group are simultaneously set to a light emitting state.