JP2023055191A - Display device - Google Patents

Abstract

To measure deterioration of luminance in a spontaneous light emitting element.SOLUTION: A display device includes: a display pixel circuit including a display light emitting element; a reference light emitting element; and a display drive circuit. The display pixel circuit controls light emission of the display light emitting element on the basis of a data signal corresponding to image data. The reference light emitting element is disconnected from control corresponding to image data. The display drive circuit acquires a reference signal for showing current/voltage characteristics of the reference light emitting element, acquires a characteristic signal for showing current/voltage characteristics of the display light emitting element, and generates a signal for showing a degree of deterioration of the display light emitting element on the basis of a difference between a reference signal and a characteristic signal.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present disclosure relates to display devices, and more particularly to measurement of luminance degradation of self-luminous elements.

An OLED (Organic Light-Emitting Diode) element is a current-driven self-luminous element, so it does not require a backlight, and has advantages such as low power consumption, a wide viewing angle, and a high contrast ratio. Expected in the development of flat panel displays.

A self-luminous device such as an OLED element undergoes an irreversible characteristic change that affects its lighting life. Specifically, a problem such as burn-in or an afterimage occurs, in which traces of the fixed form display are constantly visible. One example of a method of solving or reducing this problem is to compensate for luminance deterioration of the OLED element. This method estimates the degree of deterioration of each OLED element, and executes light emission control for correcting luminance according to the degree of deterioration. As a result, it is possible to reduce the luminance difference between pixels due to the deterioration of the OLED elements.

U.S. Patent Application Publication No. 2008/0012804 U.S. Patent Application Publication No. 2020/0013358 U.S. Patent Application Publication No. 2011/0134101

Luminance deterioration of the self-luminous element can be estimated from changes in current-voltage characteristics of the self-luminous element. However, the change in the current-voltage characteristics of the self-luminous element may be caused more by the environment than by the deterioration over time. For example, the change in current-voltage characteristics of an OLED element due to temperature changes is much greater than the change in current-voltage characteristics of an OLED element due to deterioration.

Therefore, the measurement of the current-voltage characteristics of the self-luminous element must handle a wide range of voltages (currents), which makes it more difficult to accurately measure the current-voltage characteristics due to deterioration.

A display device of one embodiment of the present disclosure includes a display pixel circuit including a display light emitting element, a reference light emitting element, and a display driving circuit. The display pixel circuit controls light emission of the display light emitting element based on a data signal corresponding to video data. The reference light emitting element is excluded from control according to the video data. The display driving circuit obtains a reference signal indicating current-voltage characteristics of the reference light-emitting element, obtains a characteristic signal indicating current-voltage characteristics of the display light-emitting element, and calculates a difference between the reference signal and the characteristic signal. to generate a signal indicating the degree of deterioration of the display light-emitting element.

According to one aspect of the present disclosure, it is possible to measure luminance deterioration of a self-luminous element.

1 schematically shows a configuration example of an OLED display device. 4 schematically shows a configuration example of a pixel circuit and a sense line driving circuit; 4 shows a flow chart of an example operation for measuring current-voltage characteristics of an OLED element of a display pixel circuit. 4 schematically shows changes due to temperature and deterioration of current-voltage characteristics of an OLED element. FIG. 3 shows a timing chart of control signals in the configuration examples shown in FIGS. 4 schematically shows a configuration example of an OLED display device according to a second embodiment; FIG. 10 shows a timing chart of control signals in the second embodiment. FIG. FIG. 12 schematically shows a configuration example of an OLED display device according to a third embodiment; FIG. FIG. 9 shows a timing chart of control signals in the configuration example shown in FIG. 3 shows another configuration example of the difference calculation circuit. 3 shows another configuration example of the difference calculation circuit. 4 schematically shows changes due to temperature and deterioration of current-voltage characteristics of an OLED element. 4 schematically shows a timing chart of an example of measuring luminance degradation of a self-luminous element within a frame period;

Embodiments of the present disclosure will be described below with reference to the accompanying drawings. It should be noted that the present embodiment is merely an example for realizing the present disclosure and does not limit the technical scope of the present disclosure.

A display device according to an embodiment of the present specification measures luminance degradation of a self-luminous element. Luminance deterioration of the self-luminous element can be estimated from changes in current-voltage characteristics of the self-luminous element. However, the change in the characteristics of the self-luminous element may be caused more by the environment than by the deterioration over time. For example, compared with the characteristic change of OLED (Organic Light-Emitting Diode) due to deterioration, the characteristic change of OLED element due to temperature change is much larger.

Therefore, it is necessary to handle a wide range of voltage (current) to measure the characteristic change due to deterioration, which makes it more difficult to accurately measure the characteristic change due to deterioration. In order to measure small changes over a wide variation range, high-resolution measurement circuits, such as high-resolution analog-to-digital converters, are required. For example, between 0.degree. C. and 85.degree. On the other hand, the amount of change in the measured voltage due to deterioration of the OLED element is about 0.1V.

A display device according to an embodiment of the present specification measures the characteristics of a self-luminous element in a display pixel circuit that displays an image based on the characteristics of a reference light-emitting element that is excluded from image display. As a result, it becomes possible to accurately measure luminance deterioration of the self-luminous element using a measurement circuit with a lower resolution.

<First embodiment>
[Configuration of display device]
A configuration of a display device according to an embodiment of the present specification will be described with reference to FIG. In order to make the description easier to understand, the dimensions and shapes of the illustrated objects may be exaggerated. An OLED display device will be described below as an example of the display device. The characteristic measurement of the light-emitting device of the present disclosure can be applied to self-light-emitting devices other than OLED devices.

FIG. 1 schematically shows a configuration example of an OLED display device 10. As shown in FIG. The OLED display device 10 includes a display area 125 including a plurality of display pixel circuits 210 arranged on a substrate, and dummy pixel circuits 220 arranged outside the display area 125 on the substrate.

The OLED element is sealed by a sealing structure (not shown). A display drive circuit is arranged around the display area 125 . Specifically, a display scanning line driving circuit 131, a sensing scanning line driving circuit 132, a sense line driving circuit 133, and a data line driving circuit 134 are arranged. OLED display device 10 further includes video control circuitry 307 . The image control circuit 307 is mounted, for example, on an anisotropic conductive film (ACF) connected to the substrate. Note that the circuits for controlling these OLED display devices 10 may be mounted anywhere.

The display pixel circuit 210 includes an OLED element (light emitting element) and a TFT (Thin Film Transistor) circuit for controlling light emission. The dummy pixel circuit 220 includes OLED elements and TFT circuits. In one embodiment herein, the circuitry of the dummy pixel circuit 220 and the circuitry of the display pixel circuit 210 are similar.

In the configuration example of FIG. 1, the display area 125 is composed of M display pixel circuit rows composed of a plurality of display pixel circuits 210 arranged along the X axis. The display pixel circuit rows are arranged along the Y-axis. The display area 125 is composed of N display pixel circuit columns composed of the display pixel circuits 210 arranged along the Y-axis. The display pixel circuit columns are arranged along the X-axis. The layout of the pixel circuits 210 and 220 can be arbitrarily determined according to the design. A display pixel row or display pixel column is a display pixel line.

The OLED elements of each display pixel circuit 210 emit light in a particular color. For example, the emission color of all display pixel circuits 210 may be white, and each display pixel circuit 210 may emit light of any color red, green, or blue. The display pixel circuits 210 forming the display area 125 display an image according to image data from the outside.

Dummy pixel circuit 220 contains a reference OLED element that is referenced to measure luminance degradation of display pixel circuit 210 . The dummy pixel circuit 220 is used for measuring luminance deterioration of the display pixel circuit 210 and is excluded from displaying an image according to image data. The dummy pixel circuit 220 may be hidden from front view by a shield (not shown), for example.

In the configuration example of FIG. 1, the number of dummy pixel circuits 220 formed on the substrate is one, which is included in one pixel circuit row together with one display pixel circuit row. A pixel circuit row is a pixel circuit line. The emission colors of the OLED elements of the dummy pixel circuit 220 are the same as those of any of the display pixel circuits 210 . In one embodiment herein, a dummy pixel circuit 220 containing OLED elements corresponding to each OLED element of every color in display area 125 is preferably located outside display area 125 . The dummy pixel circuit 220 is used to measure luminance degradation of the display pixel circuit 210 containing OLED elements of the same color. This enables accurate luminance deterioration measurement from each display pixel circuit 210 .

Each display pixel circuit row is connected to two common display scanning lines WS and ES extending along the X-axis. In FIG. 1, by way of example, each scanning line is indicated by WS and ES. The display scanning line driving circuit 131 is arranged along one side of the display area 125 outside the display area 125 . The display scanning line drive circuit 131 drives the display scanning lines WS and ES, and outputs signals for controlling the display pixel circuits 210 or the dummy pixel circuits 220 connected thereto.

As will be described later, the scan lines WS carry selection signals for selecting pixel circuit rows into which data signals that determine the brightness of the OLED elements are written. The scanning line ES transmits a light emission control signal for turning ON/OFF the current supply to the OLED element. The dummy pixel circuits 220 are connected to the same scanning lines WS and ES as the corresponding display pixel circuit row, and controlled by signals transmitted by them.

Each display pixel circuit row is connected to one common sensing scanning line. FIG. 1 shows M sense scanning lines SS1 to SSM extending along the X-axis. M is an integer greater than one. The sensing scanning line driving circuit 132 is arranged on the opposite side of the display scanning line driving circuit 131 outside the display area 125 . The sensing scanning line drive circuit 132 drives the sensing scanning lines SS1 to SSM and outputs signals for controlling the display pixel circuits 210 or the dummy pixel circuits 220 connected thereto.

As will be described later, the sensing scanning line selects a pixel circuit row for luminance deterioration measurement. A pixel circuit row includes a display pixel circuit 210 and a dummy pixel circuit 220 or is composed of only the display pixel circuit 210 . In the configuration example of FIG. 1, the dummy pixel circuit 220 is connected to the same sensing scanning line SS1 as the uppermost display pixel circuit row first selected by the sensing scanning line. When the display area 125 includes a plurality of OLED elements of different colors, for example, dummy pixel circuits including OLED elements of respective colors are connected to the sensing scan line SS1.

Each display pixel circuit column is connected to one common data line DL extending along the Y-axis. In FIG. 1, one data line is indicated by the symbol DL as an example. The data line driving circuit 134 is arranged outside the display area 125 at a position different from the other display driving circuits. In the example of FIG. 1, the data line driving circuit 134 is arranged along the upper side of the display area 125 . The data line drive circuit 134 drives the data lines DL and outputs data signals that define the light emission luminance of the OLED elements to each data line DL.

In the configuration example of FIG. 1 , the dummy pixel circuit 220 is connected to the data line DL that is not connected to any display pixel circuit 210 . In one embodiment of this specification, no data signal is written to the dummy pixel circuit 220 from the data line DL. If multiple color dummy pixel circuits are present, they may be connected to different data lines.

FIG. 1 shows (N+1) sense lines SLD, SL1 to SLN, extending along the Y-axis. N is an integer greater than one. The display scan lines, the sense scan lines, and the sense lines are control lines. The sense line driving circuit 133 is arranged on the opposite side of the data line driving circuit 134 outside the display area 125 . The sense line driving circuit 133 drives the sense lines SLD, SL1 to SLN for measuring the characteristics of the display pixel circuit 210, and from the display pixel circuit 210 or the dummy pixel circuit 220 connected thereto, the characteristics of the OLED elements are obtained. receive a signal indicating

In the configuration example of FIG. 1, one sense line SLD is connected to the dummy pixel circuit 220 and is not connected to the other display pixel circuits 210 . The sense lines SL1 to SLN are connected to display pixel circuit columns, respectively. The sense line transmits the characteristic signal of the pixel circuit selected for the sensing scanning line to the sense line drive circuit 133 in the connected pixel circuits.

The sense line drive circuit 133 includes a selector circuit 301 , a difference calculation circuit 303 and an AD converter (ADC) 305 . A selector circuit 301 selects a sense line for capturing a signal. A difference calculation circuit 303 calculates the difference between the characteristic signals of the selected display pixel circuit and the dummy pixel circuit. AD converter 305 converts an analog signal into a digital signal. Details of these circuit elements will be described later.

The image control circuit 307 generates a data signal for displaying an image corresponding to the image data in the display area 125 from the image data from the outside, and controls the display drive circuits 131 to 134 . The video control circuit 307 acquires data indicating characteristics of the OLED elements of the display pixel circuit 210 from the sense line driving circuit 133 . Specifically, the video control circuit 307 acquires data indicating the difference between the characteristics of the reference OLED element in the dummy pixel circuit 220 and the characteristics of the display OLED element in the display pixel circuit 210 . The video control circuit 307 determines a data signal to be given to the display pixel circuit 210 based on the data.

Note that the layout of the display scanning lines, the sensing scanning lines, the data lines, and the sense lines is not limited to the example shown in FIG. In the configuration example of FIG. 1, pixel circuits (display pixel circuits and dummy pixel circuits) connected to the same display scanning line are connected to the same sensing scanning line. Alternatively, pixel circuits connected to the same display scanning line may be connected to different sensing scanning lines. The dummy pixel circuit 220 may have a circuit configuration different from that of the display pixel circuit 210 .

[Circuit configuration]
Display pixel circuit 210 contains the display OLED element and dummy pixel circuit 220 contains the reference OLED element. The pixel circuits 210 and 220 control the brightness of the OLED elements by controlling the current supplied to the anode electrodes of the OLED elements. In the example described below, it is assumed that the display pixel circuit 210 and the dummy pixel circuit 220 have the same circuit configuration. This makes it possible to more accurately measure the deterioration of the luminance characteristics of the OLED elements in the display pixel circuit 210 .

FIG. 2 schematically shows a configuration example of the display pixel circuit 210 and the sense line driving circuit 133. As shown in FIG. The circuit configuration of the dummy pixel circuit 220 is similar to that of the display pixel circuit 210 . The display pixel circuit 210 includes an OLED element E1, a drive transistor P1, a select transistor P2 for display, an emission transistor P3, and a storage capacitor C1. Display pixel circuit 210 further includes select transistor P4 for characterization of OLED element E1. In the configuration example of FIG. 2, the transistors are P-type TFTs.

The selection transistor P2 is a switch that selects a pixel circuit to write a data signal. A gate of the selection transistor P2 is connected to the display scanning line WS. The source is connected to the data line DL. The drain is connected to the gate of the drive transistor P1.

The drive transistor P1 is a transistor (drive TFT) for driving the OLED element E1. The gate of the driving transistor P1 is connected to the drain terminal of the selection transistor P2. The source of the drive transistor P1 is connected to a power supply line 108 that transmits the power supply potential VDD. The drain of the drive transistor P1 is connected to the source terminal of the emission transistor P3. A holding capacitor C1 is formed between the gate and source of the driving transistor P1.

The emission transistor P3 is a switch that controls supply and stop of the drive current to the OLED element E1. A gate of the emission transistor P3 is connected to the display scanning line ES. The source of the emission transistor P3 is connected to the drain of the driving transistor P1. The drain of emission transistor P3 is connected to the anode of OLED element E1. A cathode power supply potential VSS is applied to the cathode of the OLED element E1.

The characteristic measurement selection transistor P4 is a switch that selects a pixel circuit for measuring the characteristic of the OLED element E1. The gate of the characteristic measurement selection transistor P4 is connected to the sensing scanning line SS. The scanning line for sensing SS means any one scanning line for sensing. One of the source/drain is connected to the anode of the OLED element E1, and the other is connected to the sense line SLk. Sense line SLk means the k-th sense line.

Next, the operation of the display pixel circuit 210 for image display will be described. The display scanning line driving circuit 131 outputs a selection pulse to the scanning line WS to turn on the selection transistor P2. A data voltage supplied from the data line drive circuit 134 via the data line DL is stored in the storage capacitor C1. The holding capacitor C1 holds the stored voltage throughout one frame period. The hold voltage causes the conductance of the drive transistor P1 to change in an analog manner, and the drive transistor P1 supplies a forward bias current corresponding to the emission gradation to the OLED element E1.

The emission transistor P3 is located on the drive current supply path. The display scanning line driving circuit 131 outputs a control signal to the scanning line ES to control on/off of the emission transistor P3. When the emission transistor P3 is on, a drive current is supplied to the OLED element E1. This supply is stopped when the emission transistor P3 is in the off state. By controlling the on/off of the emission transistor P3, the lighting period (duty ratio) within one frame period can be controlled.

Next, the circuit configuration for measuring the characteristics of the OLED element E1 of the display pixel circuit 210 will be described. Selector circuit 301 includes a switch corresponding to each sense line. FIG. 2 shows an arbitrary switch SLkSW connected to the sense line SLk as an example. The selector circuit 301 includes switches for each of the sense lines SLD and SL1 to SLN. The selector circuit 301 sequentially selects the switches to select the sense line that transmits the signal of the OLED element E1 to be measured. As a result, the number of difference calculation circuits 303 and AD converters 305 can be reduced.

The difference calculation circuit 303 includes a current source 310 , switches SW<b>1 and SW<b>2 , sample hold circuits (S/H) 311 and 312 , and a differential amplifier (operational amplifier) 313 . The sense line drive circuit 133 shown in FIG. 2 measures the voltage of the sense line at a constant current (voltage detection method). This voltage indicates the current-voltage characteristics of the OLED element.

[Measurement of characteristics of display pixel circuit]
Next, the operation for measuring the characteristics of the OLED element E1 of the display pixel circuit 210 will be described. FIG. 3 shows a flowchart of an example operation for measuring the current-voltage characteristics of OLED element E1 of display pixel circuit 210. As shown in FIG. The OLED display device 10 selects the dummy pixel circuit 220 by the sense scanning line driving circuit 132 and the sense line driving circuit 133, detects the Vsense voltage on the sense line SLD, and holds it by the sample hold circuit 311 (S11).

Next, the OLED display device 10 selects the display pixel circuit 210 by the scanning line driving circuit 132 for sensing and the sense line driving circuit 133, detects the Vsense voltage on the sense line, and holds it by the sample and hold circuit 312 (S12). .

Next, the OLED display device 10 uses the differential amplifier circuit 313 to measure the voltage difference Vout between the Vsense voltages of the dummy pixel circuit and the display pixel circuit (S13). Further, the OLED display device 10 sequentially selects the display pixel circuits 210 by the scanning line driving circuit 132 for sensing and the sense line driving circuit 133, and measures the voltage difference Vout (S14).

The video control circuit 307 calculates the amount of change in the Vout voltage from the initial state for each display pixel circuit, estimates the luminance deterioration of each OLED element from the amount of change, and performs luminance correction based on the estimated value (S15). ).

A more specific circuit operation will be described. During the display operation, the characteristic measurement selection transistor P4 is kept OFF. The characteristic measurement of the OLED element E1 may be performed during a period other than the period during which video data is displayed (display period), for example, during the startup sequence or shutdown sequence of the display device 10 .

In order to measure the characteristics of the OLED element E1, the sensing scanning line driving circuit 132 outputs a selection pulse to the sensing scanning line SS to turn on the selection transistor P4. This brings the sense line SLk and the OLED element E1 into conduction. The sense line driving circuit 133 takes in a signal indicating the characteristics of the OLED element E1 from the sense line SLk.

The selector circuit 301 selects the sense line SLD of the dummy pixel circuit 220, that is, turns on the switch of the sense line SLD and keeps the switches of the other sense lines off. A current source 310 provides a constant current Is to the sense line SLD through the switch of the sense line SLD. The difference calculation circuit 303 closes the switch SW1, applies the voltage of the sense line SLD to the sample hold circuit 311, and then opens the switch SW1. The switch SW2 remains OFF. The sample hold circuit 311 holds the voltage of the sense line SLD when the switch SW1 is opened.

Next, the selector circuit 301 selects the sense line of the display pixel circuit 210 to be measured. Here, it is assumed that sense line SLk is selected. The selector circuit 301 turns ON the switch SLkSW of the sense line SLk and keeps the switches of the other sense lines OFF. Current source 310 provides constant current Is to sense line SLk via switch SLkSW.

The difference calculation circuit 303 closes the switch SW2, applies the voltage of the sense line SLk to the sample hold circuit 312, and then opens the switch SW2. The switch SW1 remains OFF. The sample hold circuit 312 holds the voltage of the sense line SLk when the switch SW2 is open.

The differential amplifier circuit 313 outputs a signal Vout proportional to the difference (Vsense1-Vsense2) between the voltages held by the two sample-and-hold circuits 311 and 312. FIG. That is, the differential amplifier circuit 313 generates a reference signal (Vsense1) indicating the current-voltage characteristics of the reference OLED element of the dummy pixel circuit 220 and a characteristic signal (Vsense1) indicating the current-voltage characteristics of the display OLED element of the display pixel circuit 210 to be measured. A signal proportional to the difference from Vsense2) is output. The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value.

Note that the pixel circuit in FIG. 2 is an example, and the pixel circuit may have other circuit configurations. Although the pixel circuit in FIG. 2 uses p-channel TFTs, the pixel circuits may use n-channel TFTs. The switches of the selector circuit 301 and the difference calculation circuit 303 may be formed of TFTs of the same type as the pixel circuits, for example.

FIG. 4 schematically shows changes due to temperature and deterioration in current-voltage characteristics (IV characteristics) of an OLED element. In the graph of FIG. 4, the horizontal axis indicates the voltage of the OLED element, and the vertical axis indicates the current. FIG. 4 schematically shows changes in the voltage of the OLED element due to temperature changes and aging at a constant current Is. Specifically, FIG. 4 shows changes due to deterioration of current-voltage characteristics at temperatures of 85° C., 25° C., and 0° C. FIG. As the temperature decreases from 85° C. to 0° C., the voltage across the OLED device at constant current Is increases significantly. In comparison, voltage change due to deterioration at temperatures of 85°C, 25°C, or 0°C is small.

The OLED display device 10 of the present embodiment refers to the difference between the current-voltage characteristics of the reference OLED element and the current-voltage characteristics of the OLED element to be measured, so that the measured value of the current-voltage characteristic of the OLED element to be measured is The effect of temperature can be reduced. Thereby, for example, the resolution required for the AD converter 305 can be reduced.

FIG. 5 shows a timing chart of control signals in the configuration example shown in FIGS. Specifically, FIG. 5 shows the control signals for the sensing scanning lines SS1 to SSM, the control signals for the switches SLDSW and SL1SW to SLNSW in the selector circuit 301, and the control signals for the switches SW1 and SW2 in the difference calculation circuit 303. Indicates time change. The switches SLDSW, SL1SW to SLNSW are switches for the sense lines SLD, SL1 to SLN in the selector circuit 301, respectively.

The time change of the control signal for measuring the current-voltage characteristics of the display pixel circuit 210 will be described below. Transistors P2 and P3 in the pixel circuit are OFF during the measurement of the current-voltage characteristics.

At time T1, the signal on the sensing scanning line SS1 changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SS1 is selected. That is, the selection transistor P4 in the pixel circuit is turned ON. In addition to the display pixel circuit 210, a dummy pixel circuit 220 is connected to the sensing scanning line SS1. The signals of the other sensing scanning lines are High, and the selection transistors P4 of the pixel circuits connected to them remain OFF.

Furthermore, the control signal for the switch SLDSW of the selector circuit 301 changes from High to Low, turning the switch SLDSW ON. The other switches SL1SW-SLNSW remain OFF. In addition, the control signal for the switch SW1 in the difference calculation circuit 303 changes from High to Low, turning ON the switch SW1. The switch SW2 remains OFF.

Since the selection transistor P4 of the dummy pixel circuit 220 is ON and the switch SLDSW of the selector circuit 301 is ON, the constant current from the constant current source 310 of the difference calculation circuit 303 is applied to the sense line SLD and the OLED element E1. flow. Since the switch SW1 of the difference calculation circuit 303 is ON, the sample hold circuit 311 takes in the voltage of the sense line SLD, that is, the signal indicating the voltage of the OLED element E1 of the dummy pixel circuit 220. FIG.

Next, at time T2, the control signal for the switch SLDSW of the selector circuit 301 changes from Low to High, turning off the switch SLDSW. Also, the control signal for the switch SW1 in the difference calculation circuit 303 changes from Low to High, and the switch SW1 is turned off. Other control signals remain unchanged. A signal indicating the voltage of the OLED element E1 of the dummy pixel circuit 220 is held in the sample-and-hold circuit 311 by switching the two switches.

In one embodiment herein, switch SW1 is turned OFF immediately after switch SLDSW is turned OFF. As a result, the sample and hold circuit 311 can reliably hold the correct signal of the sense line SLD. This point is the same in the control of other pairs of switches in the selector circuit 301 and the switches in the difference calculation circuit 303 and other embodiments.

Next, at time T3, the control signal for the switch SL1SW of the selector circuit 301 changes from High to Low, turning ON the switch SL1SW. The other switches SLDSW, SL2SW-SLNSW remain OFF. In addition, the control signal for the switch SW2 in the difference calculation circuit 303 changes from High to Low, turning on the switch SW2. The switch SW1 remains OFF.

Next, at time T4, the control signal for the switch SL1SW of the selector circuit 301 changes from Low to High, turning off the switch SL1SW. Also, the control signal for the switch SW2 in the difference calculation circuit 303 changes from Low to High, and the switch SW2 is turned off. Other control signals remain unchanged. By switching the two switches, the sample and hold circuit 312 holds a signal indicating the voltage of the OLED element E1 of the display pixel circuit 210 connected to the sensing scanning line SS1 and the sense line SL1.

The differential amplifier circuit 313 outputs a signal proportional to the difference between the voltages (signals) held by the two sample-and-hold circuits 311 and 312 . These are a reference signal indicating current-voltage characteristics of the reference OLED element of the dummy pixel circuit 220 and a characteristic signal indicating current-voltage characteristics of the display OLED element of the display pixel circuit 210 selected by the scanning line SS1 for sensing and the switch SL1SW. is a signal proportional to the difference between The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value. The image control circuit 307 determines the luminance correction parameter of this display pixel circuit 210 based on the received data. The temperature detected by the temperature sensor may be referred to in determining the correction parameter.

The above process described for the switch SL1SW is also performed for the switches SL2SW to SLNSW of the other sense lines. The characteristic signals of the display pixel circuits 210 connected to the sensing scanning line SS1 are sequentially taken into the sample and hold circuit 312 from the sense lines SL2 to SLN. Data representing a signal proportional to the difference between the characteristic signal of each display pixel circuit 210 and the reference signal of the dummy pixel circuit 220 held in the sample and hold circuit 311 is provided to the video control circuit 307 .

Next, at time T5, the signal on the sensing scanning line SS1 changes from Low to High. As a result, the pixel circuit row connected to the sensing scanning line SS1 is in a non-selected state. Also, the signal on the sensing scanning line SS2 changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SS2 is selected. No dummy pixel circuit is connected to the sensing scanning line SS2, and only the display pixel circuit 210 is connected. The signals of the other sensing scanning lines are High, and the selection transistors P4 of the pixel circuits connected to them remain OFF.

Between time T5 and time T6, the signal on the sensing scanning line SS2 is maintained at Low. During this period, the characteristic signals of the display pixel circuits 210 selected by the sensing scanning line SS2 are sequentially captured by the sample-and-hold circuit 312 as described above. The sample hold circuit 311 holds a reference signal that indicates the characteristics of the dummy pixel circuit 220 . Therefore, data proportional to the difference between the characteristic signal of each display pixel circuit 210 connected to the sensing scanning line SS2 and the reference signal of the dummy pixel circuit 220 is supplied to the video control circuit 207. FIG.

After that, the sensing scanning lines SS3 to SSM are sequentially turned on, and the above-described processing for the sensing scanning line SS2 is performed. Thereby, the current-voltage characteristics of the OLED elements of all the display pixel circuits 210 are measured based on the current-voltage characteristics of the OLED elements of the dummy pixel circuit 220 .

As noted above, dummy pixel circuits of different colors may be used. For example, red, green, and blue dummy pixel circuits are connected to the sensing scanning line SS1. For example, the OLED display device 10 measures each display pixel circuit of the first color with the dummy pixel circuit of the first color as a reference, and the display pixel circuit of the second color with the dummy pixel circuit of the second color as a reference. Each measurement is performed, and each measurement of the display pixel circuit of the third color is performed using the dummy pixel circuit of the third color as a reference.

<Second embodiment>
An OLED display device according to one embodiment of the present specification is described. Differences from the OLED display device of the first embodiment will be mainly described below. FIG. 6 schematically shows a configuration example of the OLED display device 10 according to this embodiment. Compared to the configuration example shown in FIG. 1, the dummy pixel circuits D1 to DM are connected to the sensing scanning lines SS1 to SSM, respectively. The dummy pixel circuits D1 to DM are arranged at different positions on the Y axis.

The dummy pixel circuit Dk is selected by the sensing scanning line SSk. k is any value from 1 to M. Each sensing scanning line SSk is connected to a plurality of display pixel circuits 210 and dummy pixel circuits Dk, and each pixel circuit row includes a plurality of display pixel circuits 210 and dummy pixel circuits Dk.

The dummy pixel circuits D1-DM are connected to the sense line SLD. A signal of the dummy pixel circuit Dk selected by one sense scanning line SSk is taken into the sense line drive circuit 133 from the sense line SLD. In one embodiment herein, the circuitry of all dummy pixel circuits is common and may be the same as display pixel circuit 210 .

Each pixel circuit row preferably includes dummy pixel circuits containing OLED elements E1 of different colors. For example, three dummy pixel circuits each containing a red, green, and blue OLED element are connected to each sense scan line. By arranging a plurality of dummy pixel circuits at different positions, deterioration of the display pixel circuit can be measured more appropriately according to the temperature distribution in the Y-axis direction on the substrate surface. Note that some of the sensing scanning lines may not be connected to the dummy pixel circuits.

FIG. 7 shows a timing chart of control signals in this embodiment. Differences from the timing chart of FIG. 5 will be mainly described below. The operation from time T1 to just before T5 is the same as the timing chart of FIG. 5 except that the dummy pixel circuit D1 is selected.

At time T5, the signal on the sensing scanning line SS2 changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SS2 is selected. That is, the selection transistor P4 in the pixel circuit is turned on. In addition to the display pixel circuit 210, the dummy pixel circuit D2 is connected to the sensing scanning line SS2. The signals of the other sensing scanning lines are High, and the selection transistors P4 of the pixel circuits connected to them remain OFF.

Furthermore, the control signal for the switch SLDSW of the selector circuit 301 changes from High to Low, turning the switch SLDSW ON. The other switches SL1SW-SLNSW remain OFF. In addition, the control signal for the switch SW1 in the difference calculation circuit 303 changes from High to Low, turning ON the switch SW1. The switch SW2 remains OFF.

Since the selection transistor P4 of the dummy pixel circuit D2 is ON and the switch SLDSW of the selector circuit 301 is ON, the constant current from the constant current source 310 of the difference calculation circuit 303 is applied to the sense line SLD and the OLED element E1. flow. Since the switch SW1 of the difference calculation circuit 303 is ON, the sample hold circuit 311 takes in the voltage of the sense line SLD, that is, the signal indicating the voltage of the OLED element E1 of the dummy pixel circuit D2.

Next, at time T7, the control signal for the switch SLDSW of the selector circuit 301 changes from Low to High, turning off the switch SLDSW. Also, the control signal for the switch SW1 in the difference calculation circuit 303 changes from Low to High, and the switch SW1 is turned off. There is no change in other control signals. By switching the two switches, a signal indicating the voltage of the OLED element E1 of the dummy pixel circuit D2 is held in the sample-and-hold circuit 311. FIG.

Next, at time T8, the control signal for the switch SL1SW of the selector circuit 301 changes from High to Low, turning ON the switch SL1SW. The other switches SLDSW, SL2SW-SLNSW remain OFF. In addition, the control signal for the switch SW2 in the difference calculation circuit 303 changes from High to Low, turning on the switch SW2. The switch SW1 remains OFF.

Next, at time T9, the control signal for the switch SL1SW of the selector circuit 301 changes from Low to High, turning off the switch SL1SW. Also, the control signal for the switch SW2 in the difference calculation circuit 303 changes from Low to High, and the switch SW2 is turned off. There is no change in other control signals. By switching the two switches, the sample and hold circuit 312 holds a signal indicating the voltage of the OLED element E1 of the display pixel circuit 210 connected to the sensing scanning line SS2 and the sense line SL1.

The differential amplifier circuit 313 outputs a signal proportional to the difference between the voltages (signals) held by the two sample-and-hold circuits 311 and 312 . These are a reference signal indicating current-voltage characteristics of the reference OLED element of the dummy pixel circuit D2 and a characteristic signal indicating current-voltage characteristics of the display OLED element of the display pixel circuit 210 selected by the scanning line SS2 for sensing and the switch SL1SW. is a signal proportional to the difference between The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value.

The above process described for the switch SL1SW is also performed for the switches SL2SW to SLNSW of the other sense lines. The characteristic signals of the display pixel circuits 210 connected to the sensing scanning line SS2 are sequentially taken into the sample and hold circuit 312 from the sense lines SL2 to SLN. Data representing a signal proportional to the difference between the characteristic signal of each display pixel circuit 210 and the reference signal of the dummy pixel circuit D2 held in the sample and hold circuit 311 is provided to the video control circuit 307 .

Next, at time T6, the signal on the sensing scanning line SS2 changes from Low to High. As a result, the pixel circuit row connected to the sensing scanning line SS2 is in a non-selected state. Also, the signal of the next sensing scanning line SS3 (not shown in FIG. 7) changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SS3 is selected. The process described above for sense scan line SS2 is performed for sense scan line SS3.

After that, the sensing scanning lines SS4 to SSM are sequentially turned on, and the above-described processing for the sensing scanning line SS2 is performed. Thereby, the current-voltage characteristics of the OLED elements of all the display pixel circuits 210 are measured based on the current-voltage characteristics of the OLED elements of the dummy pixel circuits D1 to DM.

<Third Embodiment>
An OLED display device according to one embodiment of the present specification is described. Differences from the OLED display device of the first embodiment will be mainly described below. FIG. 8 schematically shows a configuration example of an OLED display device 10 according to this embodiment. Dummy pixel circuits DC<b>1 and DC<b>2 are arranged above the display area 125 instead of the dummy pixel circuit 220 in the configuration example shown in FIG. 1 .

The dummy pixel circuits DC<b>1 and DC<b>2 are connected to the sensing scanning lines SSD in the display area 125 . Other display pixel circuits 210 are not connected to the sensing scanning line SSD. In the sequential selection of the sensing scanning lines, the sensing scanning lines SSD are selected first. The dummy pixel circuit DC1 is connected to the sense line SL1, and the dummy pixel circuit DC2 is connected to the sense line SLN/2+1. Here, N is an even number.

As will be described later, the dummy pixel circuit DC1 provides a reference characteristic signal for measuring the characteristics of the display pixel circuits connected to the sense lines SL1-SLN/2. The dummy pixel circuit DC2 provides a reference characteristic signal for characteristic measurement of the display pixel circuits connected to the sense lines SLN/2+1 to SLN. The dummy pixel circuits DC1, DC2 are at different positions along the X-axis. Therefore, the influence of the temperature distribution in the X-axis direction on the panel surface on the current-voltage characteristics of the display pixel circuit 210 can be reduced.

The OLED display device 10 includes a sense line drive circuit 135 instead of the sense line drive circuit 133 of FIG. Sense line drive circuitry 135 includes two sets of circuitry for measuring the characteristics of the OLED elements of display pixel circuitry 210 . One set includes selector circuit 501A, difference calculation circuit 503A, and AD converter 505A. Another set includes selector circuit 501B, difference calculation circuit 503B, and AD converter 505B.

One circuit set measures the characteristics of the display pixel circuits connected to the sense lines SL1-SLN/2, and the other circuit set measures the characteristics of the display pixel circuits connected to the sense lines SLN/2+1-SLN. do. These two circuit sets execute processing (first processing and second processing) in parallel. This makes it possible to lengthen the selection time per pixel circuit or to perform high-speed processing.

Selector circuits 501A and 501B, like selector circuit 301 shown in FIG. 2, include switches for the respective sense lines they are in charge of. As shown in FIG. 9, the selector circuit 501A includes switches SL1SW to SLN/2SW that switch connection/disconnection of the sense lines SL1 to SLN/2, and the selector circuit 501B connects/disconnects the sense lines SLN/2+1 to SLN. switches SLN/2+1SW to SLNSW for switching between

The difference calculation circuits 503A and 503B, like the difference calculation circuit 303 shown in FIG. 2, include a constant current source, two switches and a sample hold circuit. As shown in FIG. 9, the difference calculation circuit 503A includes switches SW11 and SW12, and the difference calculation circuit 503B includes switches SW21 and SW22.

FIG. 9 shows a timing chart of control signals in the configuration example shown in FIG. Specifically, FIG. 9 shows control signals for sense scanning lines SSD and SS1 to SSM, control signals for switches SL1SW to SLN/2SW in the selector circuit 501A, and switches SLN/2+1SW to SLNSW in the selector circuit 501B. , the time change of the control signal of . The switches SL1SW to SLNSW are switches for the sense lines SL1 to SLN, respectively.

FIG. 9 further shows temporal changes in the control signals for the switches SW11 and SW12 in the difference calculation circuit 503A and the control signals for the switches SW21 and SW22 in the difference calculation circuit 503B. The switches SW11 and SW12 switch connection/disconnection between the corresponding sample hold circuit and the selector circuit 501A. The switches SW21 and SW22 switch connection/disconnection between the corresponding sample hold circuit and the selector circuit 501B.

At time T11, the signal on the sensing scanning line SSD changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SSD, that is, the two dummy pixel circuits DC1 and DC2 are selected. The signals of the other sensing scanning lines are High and are in a non-selected state.

Further, the control signal for the switch SL1SW of the selector circuit 501A changes from High to Low, turning ON the switch SL1SW. Other switches SL2SW to SLN/2SW in the selector circuit 501A remain OFF.

In addition, the control signal for the switch SLN/2+1SW of the selector circuit 501B changes from High to Low, turning ON the switch SLN/2+1SW. Other switches SLN/2+2SW to SLNSW in selector circuit 501B remain OFF.

Also, the control signals for the switch SW11 in the difference calculation circuit 503A and the switch SW21 in the difference calculation circuit 503B change from High to Low, turning ON the switches SW11 and SW21. The switches SW12 and SW22 remain OFF.

The first sample-and-hold circuit of the difference calculation circuit 503A takes in the reference characteristic signal of the reference OLED element E1 of the dummy pixel circuit DC1 from the sense line SL1 via the switches SL1SW and SW11. The first sample-and-hold circuit of the difference calculation circuit 503B takes in the reference characteristic signal of the reference OLED element E1 of the dummy pixel circuit DC2 from the sense line SLN/2+1 via the switches SLN/2+1SW and SW21.

Next, at time T12, the control signal for the switch SL1SW of the selector circuit 501A changes from Low to High, turning off the switch SL1SW. Also, the control signal for the switch SLN/2+1SW of the selector circuit 501B changes from Low to High, and the switch SLN/2+1SW is turned off.

Furthermore, the control signal for the switch SW11 in the difference calculation circuit 503A changes from Low to High, turning off the switch SW11. Also, the control signal for the switch SW21 in the difference calculation circuit 503B changes from Low to High, and the switch SW21 is turned off. There is no change in other control signals. By switching these switches, the reference characteristic signals of the OLED elements E1 of the dummy pixel circuits DC1 and DC2 are held in the first sample-and-hold circuits of the difference calculation circuits 503A and 503B, respectively.

After that, sense lines SL2 to SLN/2 and SLN/2+2 to SLN are sequentially selected. Since only the dummy pixel circuits DC1 and DC2 are connected to the sensing scanning line SSD, none of the pixel circuit signals are held in the second sample-and-hold circuits of the difference calculation circuits 503A and 503B. . Note that the operation of the sensing scanning line SSD after time T12 may be omitted.

Next, at time T13, the signal on the sensing scanning line SSD changes from Low to High, and the signal on the sensing scanning line SS1 changes from High to Low. As a result, the pixel circuit row connected to the sensing scanning line SS1 is selected. The signals of the other sensing scanning lines are High and are in a non-selected state.

Further, the control signal for the switch SL1SW of the selector circuit 501A changes from High to Low, turning ON the switch SL1SW. Other switches SL2SW to SLN/2SW in the selector circuit 501A remain OFF.

In addition, the control signal for the switch SLN/2+1SW of the selector circuit 501B changes from High to Low, turning ON the switch SLN/2+1SW. Other switches SLN/2+2SW to SLNSW in selector circuit 501B remain OFF.

Also, the control signals for the switch SW12 in the difference calculation circuit 503A and the switch SW22 in the difference calculation circuit 503B change from High to Low, turning ON the switches SW12 and SW22. The switches SW11 and SW21 remain OFF.

The second sample-and-hold circuit of the difference calculation circuit 503A takes in the characteristic signal of the display OLED element E1 of the display pixel circuit 210 from the sense line SL1 via the switches SL1SW and SW12. The second sample hold circuit of the difference calculation circuit 503B takes in the characteristic signal of the display OLED element E1 of the display pixel circuit 210 from the sense line SLN/2+1 via the switches SLN/2+1SW and SW22.

Next, at time T14, the control signal for the switch SL1SW of the selector circuit 501A changes from Low to High, turning off the switch SL1SW. Also, the control signal for the switch SLN/2+1SW of the selector circuit 501B changes from Low to High, and the switch SLN/2+1SW is turned off.

Furthermore, the control signal for the switch SW12 in the difference calculation circuit 503A changes from Low to High, turning off the switch SW12. Also, the control signal for the switch SW22 in the difference calculation circuit 503B changes from Low to High, and the switch SW22 is turned off. There is no change in other control signals. By switching these switches, the characteristic signals of the OLED element E1 of the display pixel circuit 210 are held in the second sample-and-hold circuits of the difference calculation circuits 503A and 503B, respectively.

The difference calculation circuit 503A outputs data indicating the difference between the characteristic signals of the dummy pixel circuit DC1 and the display pixel circuit 210 to the video control circuit 307 via the AD converter 505A. The difference calculation circuit 503B also outputs data indicating the difference between the characteristic signals of the dummy pixel circuit DC2 and the display pixel circuit 210 to the video control circuit 307 via the AD converter 505B.

The signal on the sensing scanning line SS1 is maintained at Low until time T15. During time T14 to T15, selector circuit 501A sequentially selects sense lines SL2 to SLN/2. The difference calculation circuit 503A captures the characteristic signal of the OLED element of the display pixel circuit 210 from the sense line selected by the second sample-and-hold circuit, and calculates the difference between the dummy pixel circuit DC1 and the captured characteristic signal of the display pixel circuit 210. Data indicating the difference is output to the video control circuit 307 .

Similarly, selector circuit 501B sequentially selects sense lines SLN/2+2 to SLN. The difference calculation circuit 503B captures the characteristic signal of the OLED element of the display pixel circuit 210 from the sense line selected by the second sample-and-hold circuit, and calculates the difference between the dummy pixel circuit DC2 and the captured characteristic signal of the display pixel circuit 210. Data indicating the difference is output to the video control circuit 307 .

After that, the sensing scanning lines SS2 to SSM are sequentially selected, and the process described above for the sensing scanning line SS1 is performed. Thereby, the current-voltage characteristics of the OLED elements of all the display pixel circuits 210 are measured based on the current-voltage characteristics of the OLED elements of the dummy pixel circuit DC1 or DC2.

In the sequence diagram shown in FIG. 9, the length of time each switch is ON is approximately twice the length of time in the sequence diagram shown in FIG. In the example described with reference to FIG. 9, the selection time for measurement of each pixel circuit is approximately twice the selection time for measurement of each pixel circuit in the example described with reference to FIG.

The example configurations described with reference to FIGS. 8 and 9 use two dummy pixel circuits and two sets of circuits for degradation measurements. In other examples, three or more dummy pixel circuits and three or more circuit sets for degradation measurements may be used. Each pixel circuit row may include a dummy pixel circuit, and current-voltage characteristics of the dummy pixel circuit and the display pixel circuit of each pixel circuit row may be compared as in the second embodiment. A pixel circuit column is a pixel circuit line. The plurality of dummy pixel circuits may be connected to different sense lines than the display pixel circuits, as described with reference to FIG.

A plurality of dummy pixel circuits may be included in different pixel circuit rows. For example, the first dummy pixel circuit may be connected to the sensing scanning line SS1, and the second dummy pixel circuit may be connected to the sensing scanning line SSM/2+1.

The current-voltage characteristics of the display pixel circuits connected to the sensing scanning lines SS1 to SSM/2 are measured based on the current-voltage characteristics of the first dummy pixel circuit. The current-voltage characteristics of the display pixel circuits connected to the sensing scanning lines SSM/2+1 to SSM are measured based on the current-voltage characteristics of the second dummy pixel circuit. The measurements based on the characteristics of the first dummy pixel circuit and the measurements based on the characteristics of the second dummy pixel circuit are performed in parallel, as described with reference to FIGS.

<Fourth Embodiment>
Another configuration example of the difference calculation circuit will be described below. FIG. 10 shows another configuration example of the difference calculation circuit. Differences from the configuration example shown in FIG. 2 will be mainly described. The difference calculation circuit 600 uses the correlated double sampling circuit to generate a signal proportional to the difference between the reference characteristic signal of the dummy pixel circuit and the characteristic signal of the display pixel circuit. The correlated double sampling circuit includes an operational amplifier 601 , capacitive element CS, capacitive element CF and switch 61 .

A capacitive element CS is connected between the inverting input of the operational amplifier 601 and the selector circuit 301 . A switch SW61 and a capacitive element CF are connected in parallel between a node between the inverting input of the operational amplifier 601 and the capacitive element CS and the output of the operational amplifier 601 . Current source 310 is connected to a node between capacitive element CS and selector circuit 301 .

With the switch SW61 turned on, the signal Vsense1 from the dummy pixel circuit is sampled and held. After that, with the switch SW61 turned off, the signal Vsense2 is input from the display pixel circuit. The output Vout of the operational amplifier 601 is (Cs/Cf*(Vsense1-Vsense2)).

FIG. 11 shows another configuration example of the difference calculation circuit. Differences from the configuration example shown in FIG. 2 will be mainly described. The difference calculation circuit 650 includes a current-voltage conversion circuit (I/V conversion circuit) 651 instead of the constant current source 310 of the difference calculation circuit 303 shown in FIG. The current-voltage conversion circuit 651 supplies a voltage to the OLED element E1 through SLkSW and the selection transistor P4, and converts a current signal (Isense) flowing through the OLED element through the sense line into a voltage signal.

A sample-and-hold circuit 311 holds a signal from the dummy pixel circuit subjected to current-voltage conversion, and a sample-and-hold circuit 312 holds a signal from the display pixel circuit subjected to current-voltage conversion. As described with reference to FIG. 2, the differential amplifier circuit 313 outputs the voltage difference Vout to ADC. It is also possible to connect the correlated double sampling circuit shown in FIG.

Difference calculation circuit 650 measures the current of the OLED element at a constant voltage. FIG. 12 schematically shows changes due to temperature and deterioration of current-voltage characteristics (IV characteristics) of an OLED element. In the graph of FIG. 12, the horizontal axis indicates the voltage of the OLED element, and the vertical axis indicates the current. FIG. 12 schematically shows changes in the current of the OLED element due to temperature changes and deterioration at a constant voltage Vs.

Specifically, FIG. 12 shows changes due to deterioration of current-voltage characteristics at temperatures of 85° C., 25° C., and 0° C. FIG. As the temperature decreases from 85° C. to 0° C., the current of the OLED device at constant voltage Vs increases significantly. In comparison, current changes due to degradation at temperatures of 85°C, 25°C and 0°C are small.

By referring to the difference between the current-voltage characteristics of the reference OLED element and the current-voltage characteristics of the OLED element to be measured, the influence of temperature on the measured values of the current-voltage characteristics of the OLED element to be measured can be reduced. Thereby, for example, the resolution required for the AD converter 305 can be reduced.

<Fifth Embodiment>
In this embodiment, the IV characteristics are measured during the video display period. As a result, it is possible to measure in accordance with the current situation. The image display period is a period during which each pixel circuit row of the display area 125 displays an image according to image data from the outside. A video display period is composed of a plurality of continuous frame periods. For example, the frame periods of different pixel circuit rows have the same length. Since the pixel circuit rows are sequentially selected and supplied with data signals, the start times of the frame periods of different pixel circuit rows are shifted according to the order in which the pixel circuit rows are selected.

In this embodiment, an IV characteristic measurement (IV sense) period is inserted in one frame period, and the IV characteristic of the OLED element is measured during that period. In the example described below, it is assumed that the OLED display device 10 has the configuration example shown in FIG. During the IV sense period, the pixel circuit does not perform light emission control according to the data signal, so that period is a period during which no frame image in the video is displayed.

The scanning line drive circuit 132 for sensing sequentially selects pixel circuit rows, and the sense line drive circuit 133 sequentially selects pixel circuits in the selected pixel circuit rows to measure IV characteristics. The measurement of the IV characteristics is performed in a period different from the period (frame image display period) during which light emission is controlled according to the data signal within one frame period. The IV characteristics of unselected pixel circuits are not measured.

FIG. 13 shows a timing chart of control signals in this embodiment. FIG. 13 shows successive frame periods of Y−1 pixel circuit row, Y pixel circuit row and Y+1 pixel circuit row. By way of example, the first and second frame periods of the Y pixel circuit rows are indicated at 701 and 702, respectively. The start time of the first frame period of the Y−1 pixel circuit row is earlier than the start time of the first frame period 701 by a predetermined time, and the start time of the first frame period of the Y+1 pixel circuit row is the start of the first frame period 701. It is later than the time by the predetermined time. The length of the frame period is common.

The example shown in FIG. 13 selects the Y pixel circuit row for IV characteristic measurement. In the first frame period 701, X display pixel circuit columns are selected for IV characteristic measurement, and in the following second frame period 702, X+1 display pixel circuit columns are selected for IV characteristic measurement. there is In the example shown in FIG. 13, only one pixel circuit is selected for IV characteristic measurement within one frame period, and different pixel circuits are sequentially selected as the frame period progresses.

The Y-1 pixel circuit row is selected for the IV characteristics measurement immediately before the Y pixel circuit row, and the Y+1 pixel circuit row is selected for the IV characteristics next to the Y pixel circuit row. As described above, the pixel circuits of the selected pixel circuit row are sequentially selected for IV characteristic measurements in successive different frames. For example, a dummy pixel circuit is selected first, and then different display pixel circuits are sequentially selected from the leftmost display pixel circuit to the right. In the example of FIG. 13, the IV characteristics of the dummy pixel circuits in the Y pixel circuit row have already been measured X frame periods before the first frame period 701 .

A first frame period 701 is composed of a frame image display period 711 and a subsequent IV sense period 712 of the X pixel circuit row. The pixel circuit selected for IV characteristic measurement causes the OLED element to emit light with luminance corresponding to the data signal during the frame image display period 711, and performs an operation for IV characteristic measurement during the IV sense period 712. FIG.

That is, during the frame image display period 711, the transistor P3 is ON and the transistor P4 is OFF. During IV sense period 712, transistor P3 is OFF and transistor P4 is ON.

As shown in FIG. 2, the display scanning line driving circuit 131 sequentially selects pixel circuit rows by scanning lines ES. The transistor P3 in the selected pixel circuit row is ON, and the transistor P3 in the non-selected pixel circuit row is OFF. In this example, the pulse width of the scanning signal transmitted by the scanning line ES for all pixel circuit rows is common. Therefore, pixel circuit rows and pixel circuits not selected for IV characteristic measurement have a frame image non-display period of the same length as the IV sense period 712 . Only the IV characteristics of the selected pixel circuit are measured during the frame image non-display period.

The transistor P4 is ON/OFF controlled by a selection signal transmitted by the scanning line for sensing. In the example shown in FIG. 13, the width (low period) of the selection pulse 722 of the sensing scanning line SSY is greater than the width of the selection pulse 721 of the sensing scanning line SSY-1 and the width of the selection pulse 723 of the sensing scanning line SSY+1. long.

The sensing scanning line drive circuit 132 sequentially outputs pulses 721, 722, and 723 to the sensing scanning lines SSY-1, SSY, and SSY+1. The sensing scanning line driving circuit 132 can adjust the width of the selection pulse output to each sensing scanning line by controlling the clock signal that shifts the pulse.

The selection pulse 721 for the sensing scanning line SSY-1 is output during the first half of the image non-display period for the Y-1 pixel circuit row, and the selection pulse 723 for the sensing scanning line SSY+1 is output during the image non-display period for the Y+1 pixel circuit row. is output in the second half of The selection pulse for the sensing scanning line preceding (preceding) the sensing scanning line SSY is output at the same timing as the selection pulse 721 for the sensing scanning line SSY-1. In addition, the selection pulse for the sensing scanning line after the sensing scanning line SSY (later stage) is output at the same timing as the selection pulse 723 for the sensing scanning line SSY+1. Here, all selection pulses other than the selection pulse 722 may have a common width.

In this way, by shifting the timing of the selection pulse before and after the Y pixel circuit row, the width of the selection pulse for the Y pixel circuit row can be lengthened, and appropriate IV characteristics can be measured. The sensing scanning line drive circuit 132 corrects the above timing deviation in a period after completion of sensing scanning of the Mth pixel circuit row and before sensing scanning of the first pixel circuit row.

In the example illustrated in FIG. 13, only one pixel circuit in the selected pixel circuit row is selected in one frame period to measure the IV characteristics. Alternatively, the sense line drive circuit 133 may sequentially select a plurality of pixel circuits and measure IV characteristics. This can shorten the time for IV characteristic measurement.

In the example illustrated in FIG. 13, the IV characteristics of the display pixel circuit are measured sequentially after the IV characteristics of the dummy pixel circuit are measured. Alternatively, the sense line drive circuit 133 may perform multiple IV characteristic measurements of the dummy pixel circuits in one pixel circuit row. Each time the IV characteristic measurement of a predetermined number of display pixel circuits is completed, the IV characteristic measurement of the dummy pixel circuit is performed. The predetermined number may be one or more. This can reduce the time difference between the measurement of the dummy pixel circuit and the measurement of the display pixel circuit.

In the example shown in FIG. 13, the transistor P4 is turned ON when IV characteristics are measured during the frame period. As a result, a current flows through the OLED element to emit light. For this reason, there is a possibility that light emission during characteristic measurement may be conspicuous in low-gradation display or the like. In order to reduce the influence of the IV characteristics measurement on such image display, it may be determined whether to measure the IV characteristics according to the frame image to be displayed.

The description with reference to FIG. 13 can also be applied to a circuit configuration different from that of FIG. 6, for example, the circuit configuration shown in FIG. 1 or 8, with a partial change if necessary.

Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above embodiments. A person skilled in the art can easily change, add, or convert each element of the above-described embodiments within the scope of the present disclosure. A part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment.

10 OLED display device 125 display area 220 dummy pixel circuit 131 display scanning line driving circuit 132 sensing scanning line driving circuit 133 sense line driving circuit 134 data line driving circuits 301, 501A, 501B selector circuits 303, 503A, 503B, 600, 650 difference calculation circuits 305, 505A, 505B AD converter 307 video control circuit 210 display pixel circuits SS1 to SSM sense scanning lines SLD, SL1 to SLN sense lines

Claims (13)

A display device,
a display pixel circuit including a display light emitting element;
a reference light emitting element;
a display drive circuit;
including
the display pixel circuit controls light emission of the display light emitting element based on a data signal corresponding to video data;
the reference light emitting element is removed from control according to the video data;
The display drive circuit is
obtaining a reference signal indicating current-voltage characteristics of the reference light-emitting element;
Acquiring a characteristic signal indicating current-voltage characteristics of the display light-emitting element;
generating a signal indicating the degree of deterioration of the display light-emitting element based on the difference between the reference signal and the characteristic signal;
display device. The display device according to claim 1,
the reference light emitting element is included in a dummy pixel circuit;
The dummy pixel circuit has the same circuit configuration as the display pixel circuit,
display device. The display device according to claim 1,
The display drive circuit displays an image according to the image data, sequentially selects all display pixel circuits having the same color as the reference light emitting element,
sequentially generating a signal indicating the degree of deterioration of the display light emitting element of the display pixel circuit based on the difference between the characteristic signal of the sequentially selected display pixel circuit and the reference signal;
display device. The display device according to claim 1,
including a plurality of pixel circuit lines,
each of the plurality of pixel circuit lines includes a dummy pixel circuit and a plurality of display pixel circuits connected to the same control line;
the dummy pixel circuit includes a reference light emitting element;
each of the plurality of display pixel circuits includes a display light emitting element;
The display drive circuit generates a signal indicating the degree of deterioration of each display light emitting element based on a difference between the reference signal of the reference light emitting element and the characteristic signal of each display light emitting element in each of the plurality of pixel circuit lines. ,
display device. The display device according to claim 4,
a plurality of sense lines for transmitting signals indicating current-voltage characteristics of the light-emitting element;
a plurality of sensing scanning lines for transmitting a selection signal for selecting a pixel circuit for measuring current-voltage characteristics of the light emitting element;
including
each sense line of the plurality of sense lines is connected to one pixel circuit column;
each sensing scanning line of the plurality of sensing scanning lines is connected to one pixel circuit row;
The pixel circuit lines are pixel circuit rows connected to the same sensing scanning line,
display device. The display device according to claim 1,
a plurality of pixel circuit lines;
a first dummy pixel circuit and a second dummy pixel circuit each including a reference light emitting element;
each of the plurality of pixel circuit lines includes a plurality of display pixel circuits connected to the same control line;
The display drive circuit is
degree of deterioration of each of the display light emitting elements of the first pixel circuit line group based on a difference between a reference signal of the reference light emitting element of the first dummy pixel circuit and a characteristic signal of each of the display light emitting elements of the first pixel circuit line group; perform a first process for generating a signal indicative of
degree of deterioration of each of the display light emitting elements of the second pixel circuit line group based on a difference between a reference signal of the reference light emitting element of the second dummy pixel circuit and a characteristic signal of each of the display light emitting elements of the second pixel circuit line group; perform a second process that generates a signal indicative of
the first process and the second process are executed in parallel;
display device. The display device according to claim 6,
the first dummy pixel circuit is connected to a control line of a first display pixel circuit line;
the second dummy pixel circuit is connected to a control line of a second display pixel circuit line;
display device. The display device according to claim 6,
a plurality of sense lines for transmitting signals indicating current-voltage characteristics of the light-emitting element;
a plurality of sensing scanning lines for transmitting a selection signal for selecting a pixel circuit for measuring current-voltage characteristics of the light emitting element;
including
each sense line of the plurality of sense lines is connected to one pixel circuit column;
each sensing scanning line of the plurality of sensing scanning lines is connected to one pixel circuit row;
The pixel circuit lines are pixel circuit columns connected to the same sense line,
display device. The display device according to claim 1,
a plurality of display pixel circuits;
a plurality of reference light emitting elements;
including
the display light-emitting elements of the plurality of display pixel circuits are composed of display light-emitting elements of different colors;
the plurality of reference light-emitting elements are composed of reference light-emitting elements of different colors;
The display driving circuit generates a signal indicating the degree of deterioration of the display light-emitting element based on the difference between the reference signal and the characteristic signal of the reference light-emitting element and the display light-emitting element of the same color.
display device. The display device according to claim 1,
The display driving circuit includes a correlated double sampling circuit that generates a signal indicating the degree of deterioration of the display light emitting element based on the difference between the reference signal and the characteristic signal.
display device. The display device according to claim 1,
The display driving circuit displays a frame image corresponding to the video data in a first period within one frame period, and displays a current of the reference light emitting element in a second period within the one frame period different from the first period. obtaining a reference signal indicating voltage characteristics or a characteristic signal indicating current-voltage characteristics of the display light-emitting element;
display device. The display device according to claim 11,
The display drive circuit obtains a characteristic signal indicating current-voltage characteristics of the display light-emitting elements of the plurality of display pixel circuits within the one frame period.
display device. The display device according to claim 11,
The display drive circuit acquires a characteristic signal indicating a current-voltage characteristic with respect to the reference light emitting element for each predetermined number of frame periods, and the display light emitting elements of the plurality of display pixel circuits for the predetermined number of frame periods. obtaining a characteristic signal indicative of the current-voltage characteristic;
display device.

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