Indication device

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

[0001] The present disclosure relates to display devices, and in particular to measurement of luminance degradation of self-luminous elements. Background Art

[0002] Since an OLED (Organic Light-Emitting Diode) element is a current-driven self-luminous element, it eliminates the need for a backlight and has advantages such as low power consumption, wide viewing angle, and high contrast ratio, and thus is expected in the development of flat panel displays.

[0003] In a self-luminous device such as an OLED element, irreversible characteristic changes related to lighting lifetime occur. Specifically, problems such as burn-in or afterimage, in which traces of static display are constantly visible, occur. One example of a method for eliminating or reducing this problem is compensating for the luminance degradation of OLED elements. In this method, light emission control is performed to estimate the degree of degradation of each OLED element and correct luminance in accordance with the degree of degradation. This makes it possible to reduce the luminance difference between pixels caused by degradation of OLED elements. Prior Art Documents Patent Documents

[0004] Patent Document 1 US Patent Application Publication No. 2008 / 0012804 Patent Document 2 US Patent Application Publication No. 2020 / 0013358 Patent Document 3 US Patent Application Publication No. 2011 / 0134101 Summary of the Invention Problem to be Solved by the Invention

[0005] The brightness degradation of an OLED can be estimated from the change in its current-voltage characteristics. However, the change in the current-voltage characteristics of an OLED can be more influenced by environmental factors than by degradation over time. For example, the change in the current-voltage characteristics of an OLED due to temperature changes is much larger than the change in the current-voltage characteristics of an OLED due to degradation.

[0006] Therefore, measuring the current-voltage characteristics of self-luminescent elements requires handling a wide range of voltages (currents), making accurate measurement of current-voltage characteristics due to degradation more difficult. [Means for solving the problem]

[0007] A display device according to one aspect 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 the emission of light from the display light-emitting element based on a data signal corresponding to video data. The reference light-emitting element is excluded from the control corresponding to the video data. The display driving circuit acquires a reference signal indicating the current-voltage characteristics of the reference light-emitting element, acquires a characteristic signal indicating the current-voltage characteristics of the display light-emitting element, and generates a signal indicating the degree of degradation of the display light-emitting element based on the difference between the reference signal and the characteristic signal. [Effects of the Invention]

[0008] According to one aspect of this disclosure, the brightness degradation of an autoluminescent element can be measured. [Brief explanation of the drawing]

[0009] [Figure 1] A schematic example of the configuration of an OLED display device is shown. [Figure 2] A schematic diagram of the pixel circuit and sense line driving circuit configuration is shown. [Figure 3] This flowchart shows an example of the operation for measuring the current-voltage characteristics of an OLED element in a display pixel circuit. [Figure 4] This diagram schematically illustrates the changes in the current-voltage characteristics of an OLED element due to temperature and degradation. [Figure 5] The timing charts for the control signals are shown in the configuration examples in Figures 1 and 2. [Figure 6] A schematic example of the configuration of an OLED display device according to the second embodiment is shown. [Figure 7] The timing chart of the control signal for the second embodiment is shown. [Figure 8] A schematic example of the configuration of an OLED display device according to the third embodiment is shown. [Figure 9] The timing chart for the control signals is shown in the example configuration shown in Figure 8. [Figure 10] Other configuration examples of the difference calculation circuit are shown. [Figure 11] Other configuration examples of the difference calculation circuit are shown. [Figure 12] This diagram schematically illustrates the changes in the current-voltage characteristics of an OLED element due to temperature and degradation. [Figure 13] A schematic timing chart illustrating an example of measuring the brightness degradation of a self-luminescent element within a frame duration is shown. [Modes for carrying out the invention]

[0010] Embodiments of this disclosure will be described below with reference to the attached drawings. It should be noted that these embodiments are merely one example of how to implement this disclosure and do not limit the technical scope of this disclosure.

[0011] A display device according to one embodiment of this specification measures the brightness degradation of a self-luminous element. The brightness degradation of a self-luminous element can be estimated from the change in the current-voltage characteristics of the self-luminous element. However, the change in characteristics of a self-luminous element may be greater due to environmental changes than due to degradation over time. For example, the change in characteristics of an OLED (Organic Light-Emitting Diode) due to temperature changes is much greater than the change in characteristics of an OLED due to degradation.

[0012] Therefore, measurement of characteristic changes due to degradation requires handling a wide range of voltages (currents), which makes accurate measurement of characteristic changes due to degradation more difficult. In order to measure small changes over a wide fluctuation range, a high-resolution measurement circuit, for example, a high-resolution analog-to-digital converter, is required. For example, at 0°C to 85°C, the amount of change in the measurement voltage of an OLED element is approximately 1 V. On the other hand, the amount of change in measurement voltage due to degradation of an OLED element is approximately 0.1 V.

[0013] A display device according to an embodiment of the present specification measures characteristics of self-luminous elements in a display pixel circuit that performs video display based on characteristics of a reference light-emitting element excluded from video display. This enables accurate measurement of luminance degradation of self-luminous elements with a lower-resolution measurement circuit.

[0014] <First Embodiment> [Configuration of Display Device] Referring to Fig. 1, the configuration of a display device according to an embodiment of the present specification will be described. For ease of explanation, the dimensions and shapes of the illustrated elements may be exaggerated for description. Hereinafter, an OLED display device will be described as an example of the display device. The characteristic measurement of a light-emitting element according to the present disclosure can be applied to self-luminous elements different from OLED elements.

[0015] Fig. 1 schematically shows a configuration example of an OLED display device 10. The OLED display device 10 includes a display region 125 including a plurality of display pixel circuits 210 arranged on a substrate, and a dummy pixel circuit 220 arranged outside the display region 125 on the substrate.

[0016] The OLED element is sealed by a sealing structure (not shown). Display driving circuits are arranged around the display area 125. Specifically, a display scan line driving circuit 131, a sense scan line driving circuit 132, a sense line driving circuit 133, and a data line driving circuit 134 are arranged. The OLED display device 10 further includes a video control circuit 307. The video control circuit 307 is mounted, for example, on an anisotropic conductive film (ACF) connected to a substrate. The circuits for controlling these OLED display devices 10 may be mounted in any location.

[0017] The display pixel circuit 210 includes an OLED element (light-emitting element) and a TFT (Thin Film Transistor) circuit for controlling its light emission. The dummy pixel circuit 220 includes an OLED element and a TFT circuit. In one embodiment of this specification, the circuit configuration of the dummy pixel circuit 220 is the same as that of the display pixel circuit 210.

[0018] In the configuration example shown in Figure 1, the display area 125 is composed of M rows of display pixel circuits, each consisting of multiple display pixel circuits 210 arranged along the X-axis. The rows of display pixel circuits are arranged along the Y-axis. The display area 125 is also composed of N columns of display pixel circuits, each consisting of display pixel circuits 210 arranged along the Y-axis. The columns of display pixel circuits are arranged along the X-axis. The layout of the pixel circuits 210 and 220 can be arbitrarily determined according to the design. A row of display pixels or a column of display pixels is a display pixel line.

[0019] Each OLED element in the display pixel circuit 210 emits light in a specific color. For example, the light emitted by all display pixel circuits 210 may be white, or each display pixel circuit 210 may emit light of one of the following colors: red, green, or blue. The display pixel circuits 210 that constitute the display area 125 display images corresponding to external video data.

[0020] The dummy pixel circuit 220 includes a reference OLED element that is referenced to measure the brightness degradation of the display pixel circuit 210. The dummy pixel circuit 220 is used to measure the brightness degradation of the display pixel circuit 210 and is excluded from displaying the image corresponding to the image data. The dummy pixel circuit 220 may be hidden from view from the front by, for example, an occluding object not shown.

[0021] In the configuration example shown in Figure 1, there is one dummy pixel circuit 220 formed on the substrate, and it 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 color of the OLED element of the dummy pixel circuit 220 is the same as that of any of the display pixel circuits 210. In one embodiment of this specification, it is desirable that a dummy pixel circuit 220 containing an OLED element corresponding to each of the OLED elements of all colors in the display area 125 is located outside the display area 125. The dummy pixel circuit 220 is used to measure the brightness degradation of the display pixel circuits 210 containing OLED elements of the same color. This enables more accurate brightness degradation measurement than for each display pixel circuit 210.

[0022] Each row of display pixel circuits is connected to two common display scan lines WS and ES that extend along the X-axis. In Figure 1, for example, each scan line is indicated by the codes WS and ES. The display scan line drive circuit 131 is located outside the display area 125, along one side of the display area. The display scan line drive circuit 131 drives the display scan lines WS and ES and outputs signals to control the display pixel circuits 210 or dummy pixel circuits 220 connected to them.

[0023] As described later, scan line WS transmits a selection signal to select a pixel circuit row on which to write data signals that determine the brightness of the OLED element. Scan line ES transmits a light emission control signal to turn the supply of current to the OLED element ON / OFF. The dummy pixel circuit 220 is connected to the same scan lines WS and ES as the corresponding display pixel circuit row and is controlled by the signals they transmit.

[0024] Each row of display pixel circuits is connected to a common sense scan line. Figure 1 shows M sense scan lines SS1 to SSM extending along the X-axis, where M is an integer greater than 1. The sense scan line drive circuit 132 is located outside the display area 125, opposite the display scan line drive circuit 131. The sense scan line drive circuit 132 drives the sense scan lines SS1 to SSM and outputs signals to control the display pixel circuits 210 or dummy pixel circuits 220 connected to them.

[0025] As described later, the sensing scan line selects the pixel circuit row for which brightness degradation measurement is performed. The pixel circuit row includes a display pixel circuit 210 and a dummy pixel circuit 220, or consists only of the display pixel circuit 210. In the configuration example of Figure 1, the dummy pixel circuit 220 is connected to the same sensing scan line SS1 as the uppermost display pixel circuit row initially selected by the sensing scan line. If the display area 125 includes multiple OLED elements of different colors, for example, dummy pixel circuits containing OLED elements of each color are connected to the sensing scan line SS1.

[0026] Each display pixel circuit array is connected to a common data line DL that extends along the Y-axis. In Figure 1, one data line is indicated by the code DL as an example. The data line drive circuit 134 is located outside the display area 125, in a different position from the other display drive circuits. In the example in Figure 1, the data line drive circuit 134 is located along the top edge of the display area 125. The data line drive circuit 134 drives the data line DL and outputs a data signal to each data line DL that defines the luminescence brightness of the OLED element.

[0027] In the configuration example shown in Figure 1, the dummy pixel circuit 220 is connected to a data line DL that is not connected to any of the display pixel circuits 210. In one embodiment of this specification, no data signal is written to the dummy pixel circuit 220 from the data line DL. If there are multiple colored dummy pixel circuits, each may be connected to a different data line.

[0028] Figure 1 shows (N+1) sense lines SLD, SL1 to SLN extending along the Y-axis, where N is an integer greater than 1. The display scan lines, sense scan lines, and sense lines are control lines. The sense line drive circuit 133 is located outside the display area 125, opposite the data line drive circuit 134. The sense line drive circuit 133 drives the sense lines SLD, SL1 to SLN for characterization of the display pixel circuit 210 and receives signals indicating the characteristics of the OLED element from the display pixel circuit 210 or dummy pixel circuit 220 connected to them.

[0029] In the configuration example shown in Figure 1, the sense line SLD is connected to one dummy pixel circuit 220 and not to any of the other display pixel circuits 210. Sense lines SL1 to SLN are each connected to a row of display pixel circuits. The sense line transmits the characteristic signal of the pixel circuit selected as the sensing scan line to the sense line drive circuit 133.

[0030] The sense line driving circuit 133 includes a selector circuit 301, a difference calculation circuit 303, and an AD converter (ADC) 305. The selector circuit 301 selects the sense line from which to capture a signal. The difference calculation circuit 303 calculates the difference between the characteristic signals of the selected display pixel circuit and the dummy pixel circuit. The AD converter 305 converts the analog signal into a digital signal. Details of these circuit elements will be described later.

[0031] The video control circuit 307 generates data signals from external video data to display the corresponding video in the display area 125. , The video control circuit 307 controls the motion circuits 131 to 134. The video control circuit 307 acquires data from the sense line drive circuit 133 indicating the characteristics of the OLED elements in the display pixel circuit 210. Specifically, the video control circuit 307 acquires data indicating the difference between the characteristics of the reference OLED elements in the dummy pixel circuit 220 and the characteristics of the display OLED elements in the display pixel circuit 210. Based on this data, the video control circuit 307 determines the data signal to be supplied to the display pixel circuit 210.

[0032] Note that the layout of the display scan lines, sense scan lines, data lines, and sense lines is not limited to the example in Figure 1. In the configuration example in Figure 1, pixel circuits (display pixel circuits and dummy pixel circuits) connected to the same display scan line are connected to the same sense scan line. Alternatively, pixel circuits connected to the same display scan line may be connected to different sense scan lines. The dummy pixel circuit 220 may have a different circuit configuration from the display pixel circuit 210.

[0033] [Circuit Configuration] The display pixel circuit 210 includes a display OLED element, and the dummy pixel circuit 220 includes a reference OLED element. The pixel circuits 210 and 220 control the brightness of the OLED element by controlling the current supplied to the anode electrode of the OLED element. In the example described below, the display pixel circuit 210 and the dummy pixel circuit 220 are assumed to have the same circuit configuration. This allows for more accurate measurement of the degradation of the brightness characteristics of the OLED element in the display pixel circuit 210.

[0034] Figure 2 schematically shows an example configuration of the display pixel circuit 210 and the sense line driving circuit 133. The circuit configuration of the dummy pixel circuit 220 is the same as that of the display pixel circuit 210. The display pixel circuit 210 includes an OLED element E1, a driving transistor P1, a selection transistor P2 for display, an emission transistor P3, and a retaining capacitor C1. The display pixel circuit 210 further includes a selection transistor P4 for characterizing the OLED element E1. In the example configuration of Figure 2, the transistors are P-type TFTs.

[0035] The selection transistor P2 is a switch that selects the pixel circuit on which to write the data signal. The gate of selection transistor P2 is connected to the display scan line WS. The source is connected to the data line DL. The drain is connected to the gate of the drive transistor P1.

[0036] The drive transistor P1 is a drive transistor (driver TFT) for the OLED element E1. The gate of the drive transistor P1 is connected to the drain terminal of the selection transistor P2. The source of the drive transistor P1 is connected to the power 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 retaining capacitance C1 is formed between the gate and source of the drive transistor P1.

[0037] Emission transistor P3 is a switch that controls the supply and cessation of drive current to the OLED element E1. The gate of emission transistor P3 is connected to the display scan line ES. The source of emission transistor P3 is connected to the drain of drive transistor P1. The drain of emission transistor P3 is connected to the anode of OLED element E1. The cathode of OLED element E1 is connected to the cathode power supply potential. VEE It is given

[0038] The characteristic measurement selection transistor P4 is a switch that selects the pixel circuit to measure the characteristics of the OLED element E1. The gate of the characteristic measurement selection transistor P4 is connected to the sense scan line SS. The sense scan line SS refers to any one of the sense scan lines. 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. The sense line SLk refers to the k-th sense line.

[0039] Next, the operation of the display pixel circuit 210 for displaying images will be explained. The display scan line drive circuit 131 outputs a selection pulse to the scan line WS, turning on the selection transistor P2. The data voltage supplied from the data line drive circuit 134 via the data line DL is stored in the holding capacitor C1. The holding capacitor C1 holds the stored voltage throughout one frame period. The holding voltage causes the conductance of the drive transistor P1 to change analogously, and the drive transistor P1 supplies a forward bias current corresponding to the light emission gradation to the OLED element E1.

[0040] The emission transistor P3 is located on the drive current supply path. The display scan line drive circuit 131 outputs a control signal to the scan line ES to control the on / off state of the emission transistor P3. When the emission transistor P3 is ON, drive current is supplied to the OLED element E1. When the emission transistor P3 is OFF, this supply is stopped. By controlling the on / off state of the emission transistor P3, the illumination period (duty cycle) within one frame period can be controlled.

[0041] Next, the circuit configuration for measuring the characteristics of the OLED element E1 of the display pixel circuit 210 will be described. The selector circuit 301 includes a switch corresponding to each sense line. Figure 2 shows an example of an arbitrary switch SLkSW connected to the sense line SLk. The selector circuit 301 includes switches for all sense lines SLD, SL1 to SLN. The selector circuit 301 sequentially selects the sense line that transmits the signal of the OLED element E1 to be measured by sequentially selecting the switches. This reduces the number of difference calculation circuits 303 and AD converters 305.

[0042] The difference calculation circuit 303 includes a current source 310, switches SW1 and SW2, sample-and-hold circuits (S / H) 311 and 312, and a differential amplifier. circuit This includes an operational amplifier (Op-amp) 313. The sense line driving circuit 133 shown in Figure 2 measures the voltage of the sense line at a constant current (voltage detection method). This voltage represents the current-voltage characteristics of the OLED element.

[0043] [Measurement of display pixel circuit characteristics] Next, the operation for measuring the characteristics of the OLED element E1 of the display pixel circuit 210 will be explained. Figure 3 shows a flowchart of an example of the operation for measuring the current-voltage characteristics of the OLED element E1 of the display pixel circuit 210. The OLED display device 10 selects the dummy pixel circuit 220 using the sense scan line drive circuit 132 and the sense line drive circuit 133, detects the Vsense voltage in the sense line SLD, and holds it using the sample-and-hold circuit 311 (S11).

[0044] Next, the OLED display device 10 selects a display pixel circuit 210 using the sense scan line drive circuit 132 and the sense line drive circuit 133, detects the Vsense voltage on the sense line, and holds it using the sample-and-hold circuit 312 (S12).

[0045] Next, the OLED display device 10 measures the voltage difference Vout between the Vsense voltage of the dummy pixel circuit and the display pixel circuit using the differential amplifier circuit 313 (S13). Furthermore, the OLED display device 10 sequentially selects the display pixel circuit 210 using the sense scan line drive circuit 132 and the sense line drive circuit 133 and measures the voltage difference Vout (S14).

[0046] The video control circuit 307 calculates the change in Vout voltage from the initial state for each display pixel circuit, estimates the brightness degradation of each OLED element from that change, and performs brightness correction based on the estimated value (S15).

[0047] Let's explain the circuit operation in more detail. During the display operation, the characteristic measurement selection transistor P4 is kept OFF. Characteristic measurement of the OLED element E1 may be performed during periods other than the period in which video data is displayed (display period), for example, during the startup sequence or shutdown sequence of the display device 10.

[0048] To measure the characteristics of the OLED element E1, the sense scan line drive circuit 132 outputs a selection pulse to the sense scan line SS, turning on the selection transistor P4. This causes conduction between the sense line SLk and the OLED element E1. The sense line drive circuit 133 acquires a signal from the sense line SLk that indicates the characteristics of the OLED element E1.

[0049] The selector circuit 301 selects the sense line SLD of the dummy pixel circuit 220, that is, it turns on the switch for the sense line SLD and keeps the switches for the other sense lines OFF. The current source 310 supplies a constant current Is to the sense line SLD via its switch. The difference calculation circuit 303 closes switch SW1, supplying the voltage of the sense line SLD to the sample-and-hold circuit 311, and then opens switch SW1. Switch SW2 remains OFF. The sample-and-hold circuit 311 holds the voltage of the sense line SLD when switch SW1 is opened.

[0050] Next, the selector circuit 301 selects the sense line of the display pixel circuit 210 to be measured. Here, let's assume that the sense line SLk is selected. The selector circuit 301 turns on the switch SLkSW for the sense line SLk and keeps the switches of the other sense lines OFF. The current source 310 supplies a constant current Is to the sense line SLk via the switch SLkSW.

[0051] The difference calculation circuit 303 closes switch SW2, provides the voltage across the sense line SLk to the sample-and-hold circuit 312, and then opens switch SW2. Switch SW1 remains OFF. The sample-and-hold circuit 312 holds the voltage across the sense line SLk when switch SW2 is opened.

[0052] The differential amplifier circuit 313 outputs a signal Vout that is proportional to the difference (Vsense1-Vsense2) between the voltages held by the two sample-and-hold circuits 311 and 312. In other words, the differential amplifier circuit 313 outputs a signal proportional to the difference between the reference signal (Vsense1) that shows the current-voltage characteristics of the reference OLED element of the dummy pixel circuit 220 and the characteristic signal (Vsense2) that shows the current-voltage characteristics of the display OLED element of the display pixel circuit 210 being measured. The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value.

[0053] Note that the pixel circuit in Figure 2 is an example, and the pixel circuit may have other circuit configurations. The pixel circuit in Figure 2 uses a p-channel TFT, but the pixel circuit may also use an n-channel TFT. The switches of the selector circuit 301 and the difference calculation circuit 303 may be formed, for example, from the same type of TFT as the pixel circuit.

[0054] Figure 4 schematically shows the temperature-dependent and degradation-dependent changes in the current-voltage characteristics (IV characteristics) of an OLED element. In the graph in Figure 4, the horizontal axis represents the voltage of the OLED element, and the vertical axis represents the current. Figure 4 schematically shows the temperature-dependent and degradation-dependent changes in the voltage of the OLED element at a constant current Is. Specifically, Figure 4 shows the degradation-dependent changes in the current-voltage characteristics at temperatures of 85°C, 25°C, and 0°C. As the temperature decreases from 85°C to 0°C, the voltage of the OLED element at a constant current Is increases significantly. In comparison, the voltage change due to degradation at temperatures of 85°C, 25°C, or 0°C is small.

[0055] The OLED display device 10 of this embodiment can reduce the influence of temperature on the measured value of the current-voltage characteristics of the OLED element under measurement by referring to the difference between the current-voltage characteristics of a reference OLED element and the current-voltage characteristics of the OLED element under measurement. This makes it possible to reduce the resolution required for the AD converter 305, for example.

[0056] Figure 5 shows the timing chart of the control signals in the configuration example shown in Figures 1 and 2. Specifically, Figure 5 shows the time evolution of the control signals for the sense scan 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. The switches SLDSW and SL1SW to SLNSW are switches for the sense lines SLD and SL1 to SLN in the selector circuit 301, respectively.

[0057] The following describes the time variation of the control signal used to measure the current-voltage characteristics of the display pixel circuit 210. During the measurement of the current-voltage characteristics, transistors P2 and P3 in the pixel circuit are OFF.

[0058] At time T1, the signal of the sense scan line SS1 changes from High to Low. This selects the pixel circuit row connected to the sense scan line SS1. In other words, the selection transistor P4 in the pixel circuit turns ON. In addition to the display pixel circuit 210, a dummy pixel circuit 220 is connected to the sense scan line SS1. The signals of the other sense scan lines are High, and the selection transistors P4 in the pixel circuits connected to them remain OFF.

[0059] Furthermore, the control signal for switch SLDSW in selector circuit 301 changes from High to Low, and switch SLDSW turns ON. The other switches SL1SW to SLNSW remain OFF. In addition, the control signal for switch SW1 in difference calculation circuit 303 changes from High to Low, and switch SW1 turns ON. Switch SW2 remains OFF.

[0060] Since the selection transistor P4 of the dummy pixel circuit 220 is ON, and the switch SLDSW of the selector circuit 301 is ON, a constant current from the constant current source 310 of the difference calculation circuit 303 flows to the sense line SLD and the OLED element E1. Since the switch SW1 of the difference calculation circuit 303 is ON, the sample-and-hold circuit 311 acquires a signal indicating the voltage of the sense line SLD, that is, the voltage of the OLED element E1 of the dummy pixel circuit 220.

[0061] Next, at time T2, the control signal of switch SLDSW in selector circuit 301 changes from Low to High, and switch SLDSW turns OFF. Also, the control signal of switch SW1 in difference calculation circuit 303 changes from Low to High, and switch SW1 turns OFF. There are no changes to the other control signals. By switching the two switches, the signal indicating the voltage of OLED element E1 in dummy pixel circuit 220 is held in sample-and-hold circuit 311.

[0062] In one embodiment of this specification, switch SW1 is turned OFF immediately after switch SLDSW is turned OFF. This ensures that the correct sense line SLD signal is reliably held in the sample-and-hold circuit 311. This is similar to the control of other pairs of switches in the selector circuit 301 and the difference calculation circuit 303, and in other embodiments.

[0063] Next, at time T3, the control signal for switch SL1SW in selector circuit 301 changes from High to Low, and switch SL1SW turns ON. The other switches, SLDSW, SL2SW to SLNSW, remain OFF. In addition, the control signal for switch SW2 in difference calculation circuit 303 changes from High to Low, and switch SW2 turns ON. Switch SW1 remains OFF.

[0064] Next, at time T4, the control signal of switch SL1SW in selector circuit 301 changes from Low to High, and switch SL1SW turns OFF. Also, the control signal of switch SW2 in difference calculation circuit 303 changes from Low to High, and switch SW2 turns OFF. There are no changes to the other control signals. By switching the two switches, the signals indicating the voltage of the OLED element E1 of the display pixel circuit 210 connected to the sense scan line SS1 and sense line SL1 are held in the sample-and-hold circuit 312.

[0065] 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. This signal is proportional to the difference between a reference signal indicating the current-voltage characteristics of the reference OLED element of the dummy pixel circuit 220 and a characteristic signal indicating the current-voltage characteristics of the display OLED element of the display pixel circuit 210 selected by the sense scan line SS1 and switch SL1SW. The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value. The video control circuit 307 determines the brightness correction parameter of the display pixel circuit 210 based on the received data. In determining the correction parameter, the temperature detected by the temperature sensor may be referenced.

[0066] The process described above for switch SL1SW is also performed for the other sense line switches SL2SW to SLNSW. Characteristic signals from the display pixel circuits 210 connected to the sense scan line SS1 are sequentially taken up by 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.

[0067] Next, at time T5, the signal for the sense scan line SS1 changes from Low to High. This deselects the pixel circuit row connected to the sense scan line SS1. Also, the signal for the sense scan line SS2 changes from High to Low. This selects the pixel circuit row connected to the sense scan line SS2. No dummy pixel circuits are connected to the sense scan line SS2; only the display pixel circuit 210 is connected. The signals for the other sense scan lines are High, and the selection transistor P4 of the pixel circuits connected to them remains OFF.

[0068] Between time T5 and time T6, the signal of the sensing scan line SS2 is kept low. During this period, the characteristic signals of the display pixel circuits 210 selected by the sensing scan line SS2 are sequentially taken up by the sample-and-hold circuit 312 as described above. The sample-and-hold circuit 311 holds a reference signal that represents 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 scan line SS2 and the reference signal of the dummy pixel circuit 220 is supplied to the video control circuit 207.

[0069] Subsequently, the sensing scan lines SS3 to SSM are sequentially turned ON, and the processing described above is performed on the sensing scan line SS2. As a result, the current-voltage characteristics of all OLED elements in the display pixel circuit 210 are measured relative to the current-voltage characteristics of the OLED elements in the dummy pixel circuit 220.

[0070] As described above, dummy pixel circuits of different colors may be used. For example, red, green, and blue dummy pixel circuits may be connected to the sense scan line SS1. The OLED display device 10 may, for example, use the first-color dummy pixel circuit as a reference to measure each of the first-color display pixel circuits, use the second-color dummy pixel circuit as a reference to measure each of the second-color display pixel circuits, and use the third-color dummy pixel circuit as a reference to measure each of the third-color display pixel circuits.

[0071] <Second Embodiment> An OLED display device according to one embodiment of this specification will be described below. The differences from the OLED display device of the first embodiment will be mainly described below. Figure 6 schematically shows an example of the configuration of the OLED display device 10 according to this embodiment. Compared to the example configuration shown in Figure 1, each of the dummy pixel circuits D1 to DM is connected to the sense scan lines SS1 to SSM. The dummy pixel circuits D1 to DM are arranged at different positions on the Y axis.

[0072] The dummy pixel circuit Dk is selected by the sense scan line SSk, where k is any value from 1 to M. Each sense scan line SSk is connected to multiple display pixel circuits 210 and dummy pixel circuits Dk, and each pixel circuit row contains multiple display pixel circuits 210 and dummy pixel circuits Dk.

[0073] Dummy pixel circuits D1 to DM are connected to the sense line SLD. The signal from dummy pixel circuit Dk, selected by one sense scan line SSk, is taken up by the sense line SLD and then into the sense line drive circuit 133. In one embodiment of this specification, the circuit configuration of all dummy pixel circuits is common and may be identical to that of the display pixel circuit 210.

[0074] It is desirable that each pixel circuit row includes a dummy pixel circuit containing an OLED element E1 of a different color. For example, three dummy pixel circuits, each containing a red, green, and blue OLED element, are connected to each sense scan line. By arranging multiple dummy pixel circuits at different positions, the degradation of the display pixel circuit can be measured more appropriately according to the temperature distribution in the Y-axis direction of the substrate surface. Note that some sense scan lines do not need to have dummy pixel circuits connected to them.

[0075] Figure 7 shows the timing chart of the control signals in this embodiment. The differences from the timing chart in Figure 5 will be explained below. The operation from time T1 to just before T5 is the same as the timing chart in Figure 5, except that the dummy pixel circuit D1 is selected.

[0076] At time T5, the signal of the sensing scan line SS2 changes from High to Low. This selects the pixel circuit row connected to the sensing scan line SS2. In other words, the selection transistor P4 in the pixel circuit turns ON. In addition to the display pixel circuit 210, a dummy pixel circuit D2 is connected to the sensing scan line SS2. The signals of the other sensing scan lines are High, and the selection transistors P4 in the pixel circuits connected to them remain OFF.

[0077] Furthermore, the control signal for switch SLDSW in selector circuit 301 changes from High to Low, and switch SLDSW turns ON. The other switches SL1SW to SLNSW remain OFF. In addition, the control signal for switch SW1 in difference calculation circuit 303 changes from High to Low, and switch SW1 turns ON. Switch SW2 remains OFF.

[0078] Since the selection transistor P4 of the dummy pixel circuit D2 is ON, and the switch SLDSW of the selector circuit 301 is ON, a constant current from the constant current source 310 of the difference calculation circuit 303 flows to the sense line SLD and the OLED element E1. Since the switch SW1 of the difference calculation circuit 303 is ON, the sample-and-hold circuit 311 acquires a signal indicating the voltage of the sense line SLD, that is, the voltage of the OLED element E1 of the dummy pixel circuit D2.

[0079] Next, at time T7, the control signal of switch SLDSW in selector circuit 301 changes from Low to High, and switch SLDSW turns OFF. Also, the control signal of switch SW1 in difference calculation circuit 303 changes from Low to High, and switch SW1 turns OFF. There are no changes to the other control signals. By switching the two switches, the signal indicating the voltage of OLED element E1 in dummy pixel circuit D2 is held in sample-and-hold circuit 311.

[0080] Next, at time T8, the control signal for switch SL1SW in selector circuit 301 changes from High to Low, and switch SL1SW turns ON. The other switches, SLDSW, SL2SW to SLNSW, remain OFF. In addition, the control signal for switch SW2 in difference calculation circuit 303 changes from High to Low, and switch SW2 turns ON. Switch SW1 remains OFF.

[0081] Next, at time T9, the control signal of switch SL1SW in selector circuit 301 changes from Low to High, and switch SL1SW turns OFF. Also, the control signal of switch SW2 in difference calculation circuit 303 changes from Low to High, and switch SW2 turns OFF. There are no changes to other control signals. By switching the two switches, the signals indicating the voltage of the OLED element E1 of display pixel circuit 210 connected to the sense scan line SS2 and sense line SL1 are held in sample-and-hold circuit 312.

[0082] 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. This signal is proportional to the difference between the reference signal, which shows the current-voltage characteristics of the reference OLED element of the dummy pixel circuit D2, and the characteristic signal, which shows the current-voltage characteristics of the display OLED element of the display pixel circuit 210 selected by the sense scan line SS2 and switch SL1SW. The AD converter 305 converts the analog signal from the differential amplifier circuit 313 into a digital value.

[0083] The process described above for switch SL1SW is also performed for the other sense line switches SL2SW to SLNSW. Characteristic signals from the display pixel circuits 210 connected to the sense scan line SS2 are sequentially taken up by 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.

[0084] Next, at time T6, the signal of the sense scan line SS2 changes from Low to High. This deselects the pixel circuit row connected to the sense scan line SS2. Also, the signal of the next sense scan line SS3 (not shown in Figure 7) changes from High to Low. This selects the pixel circuit row connected to the sense scan line SS3. The process described above for the sense scan line SS2 is then performed for the sense scan line SS3.

[0085] Subsequently, the sensing scan lines SS4 to SSM are sequentially turned ON, and the processing described above is performed on the sensing scan line SS2. As a result, the current-voltage characteristics of all OLED elements in the display pixel circuit 210 are measured relative to the current-voltage characteristics of the OLED elements in the dummy pixel circuits D1 to DM.

[0086] <Third Embodiment> An OLED display device according to one embodiment of this specification will be described below. The differences from the OLED display device of the first embodiment will be mainly described below. Figure 8 schematically shows an example of the configuration of the OLED display device 10 according to this embodiment. In place of the dummy pixel circuit 220 in the example configuration shown in Figure 1, dummy pixel circuits DC1 and DC2 are arranged on the upper side of the display area 125.

[0087] Dummy pixel circuits DC1 and DC2 are , se It is connected to the sense scan line SSD. No other display pixel circuits 210 are connected to the sense scan line SSD. In the sequential selection of the sense scan line, the sense scan line SSD is selected first. Dummy pixel circuit DC1 is connected to sense line SL1, and dummy pixel circuit DC2 is connected to sense line SLN / 2+1. Here, N is an even number.

[0088] As described later, dummy pixel circuit DC1 provides a reference characteristic signal for measuring the characteristics of the display pixel circuit connected to sense lines SL1 to SLN / 2. Dummy pixel circuit DC2 provides a reference characteristic signal for measuring the characteristics of the display pixel circuit connected to sense lines SLN / 2+1 to SLN. Dummy pixel circuits DC1 and DC2 are located 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.

[0089] The OLED display device 10 includes a sense line driving circuit 135 instead of the sense line driving circuit 133 in Figure 1. The sense line driving circuit 135 includes two sets of circuits for measuring the characteristics of the OLED elements of the display pixel circuit 210. One set includes a selector circuit 501A, a difference calculation circuit 503A, and an AD converter 505A. The other set includes a selector circuit 501B, a difference calculation circuit 503B, and an AD converter 505B.

[0090] One circuit set measures the characteristics of the display pixel circuits connected to sense lines SL1 to SLN / 2, while the other circuit set measures the characteristics of the display pixel circuits connected to sense lines SLN / 2+1 to SLN. These two circuit sets perform processing (first and second processing) in parallel. This allows for a longer selection time per pixel circuit, or enables high-speed processing.

[0091] Selector circuits 501A and 501B include switches for each sense line they are responsible for, as shown in selector circuit 301 in Figure 2. As shown in Figure 9, selector circuit 501A includes switches SL1SW to SLN / 2SW for connecting / disconnecting sense lines SL1 to SLN / 2, and selector circuit 501B includes switches SLN / 2+1SW to SLNSW for connecting / disconnecting sense lines SLN / 2+1 to SLN.

[0092] The difference calculation circuits 503A and 503B include a constant current source, two switches, and a sample-and-hold circuit, as shown in the difference calculation circuit 303 in Figure 2. As shown in Figure 9, the difference calculation circuit 503A includes switches SW11 and SW12, and the difference calculation circuit 503B includes switches SW21 and SW22.

[0093] Figure 9 shows the timing chart of the control signals in the configuration example shown in Figure 8. Specifically, Figure 9 shows the time evolution of the control signals for the sense scan lines SSD, SS1 to SSM, the control signals for switches SL1SW to SLN / 2SW in selector circuit 501A, and the control signals for switches SLN / 2+1SW to SLNSW in selector circuit 501B. Switches SL1SW to SLNSW are switches for the sense lines SL1 to SLN, respectively.

[0094] Figure 9 further shows the time variation of the control signals for switches SW11 and SW12 in the difference calculation circuit 503A, and the control signals for switches SW21 and SW22 in the difference calculation circuit 503B. Switches SW11 and SW12 switch the connection / disconnection between the corresponding sample-and-hold circuit and the selector circuit 501A, respectively. Switches SW21 and SW22 switch the connection / disconnection between the corresponding sample-and-hold circuit and the selector circuit 501B, respectively.

[0095] At time T11, the signal of the sense scan line SSD changes from High to Low. This selects the pixel circuit row connected to the sense scan line SSD, i.e., the two dummy pixel circuits DC1 and DC2. The signals of the other sense scan lines remain High and are in a deselected state.

[0096] Furthermore, the control signal for switch SL1SW in selector circuit 501A changes from High to Low, and switch SL1SW turns ON. The other switches in selector circuit 501A, SL2SW to SLN / 2SW, remain OFF.

[0097] In addition, the control signal for switch SLN / 2+1SW in selector circuit 501B changes from High to Low, and switch SLN / 2+1SW turns ON. The other switches in selector circuit 501B, SLN / 2+2SW to SLNSW, remain OFF.

[0098] Additionally, the control signals for switch SW11 in the difference calculation circuit 503A and switch SW21 in the difference calculation circuit 503B change from High to Low, causing switches SW11 and SW21 to turn ON. Switches SW12 and SW22 remain OFF.

[0099] The first sample-and-hold circuit of the difference calculation circuit 503A acquires the reference characteristic signal of the reference OLED element E1 of the dummy pixel circuit DC1 from the sense line SL1 via switches SL1SW and SW11. The first sample-and-hold circuit of the difference calculation circuit 503B acquires the reference characteristic signal of the reference OLED element E1 of the dummy pixel circuit DC2 from the sense line SLN / 2+1 via switches SLN / 2+1SW and SW21.

[0100] Next, at time T12, the control signal for switch SL1SW of selector circuit 501A changes from Low to High, and switch SL1SW turns OFF. Also, the control signal for switch SLN / 2+1SW of selector circuit 501B changes from Low to High, and switch SLN / 2+1SW turns OFF.

[0101] Furthermore, the control signal of switch SW11 in the difference calculation circuit 503A changes from Low to High, and switch SW11 turns OFF. Also, the control signal of switch SW21 in the difference calculation circuit 503B changes from Low to High, and switch SW21 turns OFF. There are no changes to the 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.

[0102] Subsequently, sense lines SL2 to SLN / 2 and SLN / 2+2 to SLN are selected in sequence. Since only dummy pixel circuits DC1 and DC2 are connected to the sense scan line SSD, the signals from either pixel circuit are not held in the second sample-and-hold circuits of the difference calculation circuits 503A and 503B. Note that the operation of the sense scan line SSD after time T12 may be omitted.

[0103] Next, at time T13, the signal of the sense scan line SSD changes from Low to High, and the signal of the sense scan line SS1 changes from High to Low. As a result, the pixel circuit row connected to the sense scan line SS1 is selected. The signals of the other sense scan lines are High and are in a deselected state.

[0104] Furthermore, the control signal for switch SL1SW in selector circuit 501A changes from High to Low, and switch SL1SW turns ON. The other switches in selector circuit 501A, SL2SW to SLN / 2SW, remain OFF.

[0105] In addition, the control signal for switch SLN / 2+1SW in selector circuit 501B changes from High to Low, and switch SLN / 2+1SW turns ON. The other switches in selector circuit 501B, SLN / 2+2SW to SLNSW, remain OFF.

[0106] Additionally, the control signals for switch SW12 in the difference calculation circuit 503A and switch SW22 in the difference calculation circuit 503B change from High to Low, causing switches SW12 and SW22 to turn ON. Switches SW11 and SW21 remain OFF.

[0107] The second sample-and-hold circuit of the difference calculation circuit 503A acquires the characteristic signal of the display OLED element E1 of the display pixel circuit 210 from the sense line SL1 via switches SL1SW and SW12. The second sample-and-hold circuit of the difference calculation circuit 503B acquires the characteristic signal of the display OLED element E1 of the display pixel circuit 210 from the sense line SLN / 2+1 via switches SLN / 2+1SW and SW22.

[0108] Next, at time T14, the control signal for switch SL1SW of selector circuit 501A changes from Low to High, and switch SL1SW turns OFF. Also, the control signal for switch SLN / 2+1SW of selector circuit 501B changes from Low to High, and switch SLN / 2+1SW turns OFF.

[0109] Furthermore, the control signal of switch SW12 in the difference calculation circuit 503A changes from Low to High, and switch SW12 turns OFF. Also, the control signal of switch SW22 in the difference calculation circuit 503B changes from Low to High, and switch SW22 turns OFF. There are no changes to the 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.

[0110] The difference calculation circuit 503A outputs data showing 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 showing 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.

[0111] The signal of the sense scan line SS1 is kept low until time T15. Between times T14 and T15, the selector circuit 501A sequentially selects sense lines SL2 to SLN / 2. The difference calculation circuit 503A acquires the characteristic signal of the OLED element of the display pixel circuit 210 from the selected sense line to the second sample-and-hold circuit, and outputs data showing the difference between the dummy pixel circuit DC1 and the acquired characteristic signal of the display pixel circuit 210 to the video control circuit 307.

[0112] Similarly, the selector circuit 501B sequentially selects the sense lines SLN / 2+2 to SLN. The difference calculation circuit 503B acquires the characteristic signal of the OLED element of the display pixel circuit 210 from the selected sense line to the second sample-and-hold circuit, and outputs data showing the difference between the dummy pixel circuit DC2 and the acquired characteristic signal of the display pixel circuit 210 to the video control circuit 307.

[0113] Subsequently, the sensing scan lines SS2 to SSM are selected sequentially, and the processing described above is performed on the sensing scan line SS1. As a result, the current-voltage characteristics of all OLED elements in the display pixel circuit 210 are measured relative to the current-voltage characteristics of the OLED elements in the dummy pixel circuit DC1 or DC2.

[0114] In the sequence diagram shown in Figure 9, the duration for which each switch is ON is approximately twice the duration in the sequence diagram shown in Figure 5. In the example described with reference to Figure 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 Figure 5.

[0115] The configuration example described with reference to Figures 8 and 9 uses two dummy pixel circuits and two circuit sets for degradation measurement. In other examples, three or more dummy pixel circuits and three or more circuit sets for degradation measurement may be used. Each pixel circuit array includes a dummy pixel circuit, and the current-voltage characteristics of the dummy pixel circuit and the display pixel circuit of each pixel circuit array may be compared, as in the second embodiment. A pixel circuit array is a pixel circuit line. Multiple dummy pixel circuits may be connected to different sense lines from the display pixel circuit, as described with reference to Figure 1.

[0116] Multiple dummy pixel circuits may each be located in a different pixel circuit row. For example, a first dummy pixel circuit may be connected to the sense scan line SS1, and a second dummy pixel circuit may be connected to the sense scan line SSM / 2+1.

[0117] The current-voltage characteristics of the display pixel circuits connected to the sense scan lines SS1 to SSM / 2 are measured relative to the current-voltage characteristics of the first dummy pixel circuit. The current-voltage characteristics of the display pixel circuits connected to the sense scan lines SSM / 2+1 to SSM are measured relative to the current-voltage characteristics of the second dummy pixel circuit. The measurement relative to the characteristics of the first dummy pixel circuit and the measurement relative to the characteristics of the second dummy pixel circuit are performed in parallel, as explained with reference to Figures 8 and 9.

[0118] <Fourth Embodiment> The following describes other configuration examples of the difference calculation circuit. Figure 10 shows another configuration example of the difference calculation circuit. The differences from the configuration example shown in Figure 2 will be mainly explained. The difference calculation circuit 600 generates 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 using a correlated double sampling circuit. The correlated double sampling circuit includes an operational amplifier 601, a capacitive element CS, a capacitive element CF, and a switch 61.

[0119] 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 the node between the inverting input of the operational amplifier 601 and the capacitive element CS, and the output of the operational amplifier 601. A current source 310 is connected to the node between the capacitive element CS and the selector circuit 301.

[0120] When switch SW61 is ON, the signal Vsense1 from the dummy pixel circuit is sampled and held. Then, when switch SW61 is OFF, the signal Vsense2 from the display pixel circuit is input. The output Vout of op-amp 601 is (Cs / Cf*(Vsense1-Vsense2)).

[0121] Figure 11 shows another example configuration of the difference calculation circuit. The main difference from the example configuration shown in Figure 2 will be explained. 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 Figure 2. The current-voltage conversion circuit 651 supplies voltage to the OLED element E1 via SLkSW and selection transistor P4, and converts the current signal (Isense) flowing through the sense line to the OLED element into a voltage signal.

[0122] The signal from the dummy pixel circuit, which has been converted from current to voltage, is held in the sample-and-hold circuit 311, and the signal from the display pixel circuit, which has also been converted from current to voltage, is held in the sample-and-hold circuit 312. As explained with reference to Figure 2, the differential amplifier circuit 313 outputs its voltage difference Vout to the ADC. It is also possible to connect the correlated double sampling circuit shown in Figure 10 to the output of the current-to-voltage conversion circuit 651 and use it with respect to the difference calculation circuit 650.

[0123] The difference calculation circuit 650 measures the current of the OLED element at a constant voltage. Figure 12 schematically shows the temperature-dependent and degradation-dependent changes in the current-voltage characteristics (IV characteristics) of the OLED element. In the graph of Figure 12, the horizontal axis represents the voltage of the OLED element, and the vertical axis represents the current. Figure 12 schematically shows the temperature-dependent and degradation-dependent changes in the current of the OLED element at a constant voltage Vs.

[0124] Specifically, Figure 12 shows the changes due to degradation of the current-voltage characteristics at temperatures of 85°C, 25°C, and 0°C. As the temperature decreases from 85°C to 0°C, the current of the OLED element at a constant voltage Vs increases significantly. In comparison, the current change due to degradation at temperatures of 85°C, 25°C, or 0°C is small.

[0125] By referencing the difference between the current-voltage characteristics of a reference OLED element and the current-voltage characteristics of the OLED element being measured, the influence of temperature on the measured current-voltage characteristics of the OLED element being measured can be reduced. This allows, for example, to reduce the resolution required for the AD converter 305.

[0126] <Fifth Embodiment> This embodiment measures the IV characteristics during the video display period. This enables measurements that are in line with the current situation. The video display period is the period during which each pixel circuit row of the display area 125 displays an image according to external video data. The video display period consists of multiple consecutive frame periods. For example, the frame periods of different pixel circuit rows have the same length. Since the pixel circuit rows are selected sequentially and given data signals, the start times of the frame periods of different pixel circuit rows are shifted according to the selection order of the pixel circuit rows.

[0127] In this embodiment, a period for IV characteristic measurement (IV sense) is inserted during one frame period, and the IV characteristics of the OLED element are measured during that period. In the example described below, the OLED display device 10 is assumed to have the configuration example shown in Figure 6. During the IV sense period, the pixel circuit does not perform light emission control according to the data signal, so this period is a period during which the frame image in the video is not displayed.

[0128] The sensing scan line driving circuit 132 sequentially selects pixel circuit rows, and the sensing line driving circuit 133 sequentially selects the pixel circuits of the selected pixel circuit rows to measure the IV characteristics. The IV characteristics are measured within a single frame period, but the light emission control corresponding to the data signal is performed for a period different from the frame image display period. The IV characteristics of unselected pixel circuits are not measured.

[0129] Figure 13 shows the timing chart of the control signals in this embodiment. Figure 13 shows the consecutive frame periods of the Y-1 pixel circuit row, the Y pixel circuit row, and the Y+1 pixel circuit row. For example, the first frame period and the second frame period of the Y pixel circuit row are indicated by reference numerals 701 and 702, respectively. The start time of the first frame period of the Y-1 pixel circuit row is predetermined time earlier than the start time of the first frame period 701, and the start time of the first frame period of the Y+1 pixel circuit row is predetermined time later than the start time of the first frame period 701. The length of the frame periods is common to all.

[0130] In the example shown in Figure 13, the Y pixel circuit row is selected for IV characteristic measurement. In the first frame period 701, the X display pixel circuit row is selected for IV characteristic measurement, and in the next second frame period 702, the X+1 display pixel circuit row is selected for IV characteristic measurement. In the example shown in Figure 13, only one pixel circuit is selected for IV characteristic measurement within a single frame period, and different pixel circuits are sequentially selected as the frame period progresses.

[0131] The Y-1 pixel circuit row is selected for IV characteristic measurement immediately before the Y pixel circuit row, and the Y+1 pixel circuit row is selected for IV characteristic measurement after the Y pixel circuit row. As described above, the pixel circuits of the selected pixel circuit rows are measured in consecutive different frames. period In this process, pixels are sequentially selected for IV characteristic measurement. 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 in Figure 13, the IV characteristics of the dummy pixel circuit of the Y pixel circuit row have been measured before the X frame period from the first frame period 701.

[0132] The first frame period 701 consists of a frame image display period 711 and the subsequent IV sense period 712 of the X pixel circuit sequence. The pixel circuit selected for IV characteristic measurement emits light from the OLED element at a brightness corresponding to the data signal during the frame image display period 711 and performs operations for IV characteristic measurement during the IV sense period 712.

[0133] In other words, during the frame image display period 711, transistor P3 is ON and transistor P4 is OFF. During the IV sense period 712, transistor P3 is OFF and transistor P4 is ON.

[0134] As shown in Figure 2, the display scan line drive circuit 131 sequentially selects pixel circuit rows using the scan line ES. Transistor P3 of the selected pixel circuit row is ON, and transistor P3 of the unselected pixel circuit row is OFF. In this example, the pulse width of the scan signal transmitted by the scan line ES is common for all pixel circuit rows. Therefore, pixel circuit rows and pixel circuits that are 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.

[0135] Transistor P4 is controlled ON / OFF by the selection signal transmitted by the sense scan line. In the example shown in Figure 13, the width (Low period) of the selection pulse 722 of the sense scan line SSY is longer than the width of the selection pulse 721 of the sense scan line SSY-1 and the selection pulse 723 of the sense scan line SSY+1.

[0136] The sense scan line drive circuit 132 sequentially outputs pulses 721, 722, and 723 to the sense scan lines SSY-1, SSY, and SSY+1. The sense scan line drive circuit 132 can adjust the width of the selected pulse output to each sense scan line by controlling the clock signal that shifts the pulses.

[0137] The selection pulse 721 for the sense scan line SSY-1 is output during the first half of the image hiding period for the Y-1 pixel circuit row, and the selection pulse 723 for the sense scan line SSY+1 is output during the second half of the image hiding period for the Y+1 pixel circuit row. The selection pulses for the sense scan lines preceding (preceding) the sense scan line SSY are output at the same timing as the selection pulse 721 for the sense scan line SSY-1. Similarly, the selection pulses for the sense scan lines following (sequentially) the sense scan line SSY are output at the same timing as the selection pulse 723 for the sense scan line SSY+1. Here, the width of all selection pulses except for selection pulse 722 may be the same.

[0138] 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 increased, enabling proper IV characteristic measurement. The sensing scan line drive circuit 132 corrects the above timing shift during the period after the sensing scan of the Mth pixel circuit row is completed and before the sensing scan of the first row of pixel circuit rows.

[0139] The example illustrated in Figure 13 measures the IV characteristics by selecting only one pixel circuit in a selected row of pixel circuits during a single frame period. In contrast, the sense line driving circuit 133 may sequentially select multiple pixel circuits to measure their IV characteristics. This can reduce the time required for IV characteristic measurement.

[0140] The example illustrating Figure 13 measures the IV characteristics of the dummy pixel circuit, and then sequentially measures the IV characteristics of the display pixel circuit. In contrast, the sense line driving circuit 133 may perform multiple IV characteristic measurements of dummy pixel circuits in a single pixel circuit row. After a predetermined number of display pixel circuit IV characteristic measurements are completed, the IV characteristic measurement of the dummy pixel circuit is performed. The predetermined number may be 1 or a larger number. This reduces the time difference between the measurement of the dummy pixel circuit and the measurement of the display pixel circuit.

[0141] In the example shown in Figure 13, transistor P4 is turned ON when IV characteristic measurement is performed during the frame period. As a result, current flows to the OLED element, causing it to emit light. Therefore, the light emitted during characteristic measurement may be noticeable in low-gradation displays. To reduce the impact of IV characteristic measurement on image display, it may be possible to determine whether or not to perform IV characteristic measurement depending on the frame image being displayed.

[0142] The explanation with reference to Figure 13 can also be applied to circuit configurations different from those in Figure 6, such as those shown in Figures 1 or 8, with some modifications as necessary.

[0143] While embodiments of the present disclosure have been described above, the present disclosure is not limited to the embodiments described above. Those skilled in the art can easily modify, add to, and transform each element of the above embodiments within the scope of the present disclosure. It is possible to replace parts of the configuration of one embodiment with the configuration of another embodiment, and to add the configuration of another embodiment to the configuration of one embodiment. [Explanation of Symbols]

[0144] 10 OLED display device 125 Display area 220 Dummy Pixel Circuit 131 Display Scan Line Driving Circuit 132 Sense scan line drive circuit 133 Sense Line Drive Circuit 134 Data Line Drive Circuit 301, 501A, 501B Selector Circuit 303, 503A, 503B, 600, 650 difference calculation circuit 305, 505A, 505B AD converters 307 Video control circuit 210 Display Pixel Circuit SS1~SSM Sense scan lines SLD, SL1~SLN Sense Lines

Claims

1. A display device, A display pixel circuit including a display light-emitting element, A dummy pixel circuit including a reference light-emitting element, Display drive circuit and Includes, The display pixel circuit controls the emission of light from the display light-emitting element based on a data signal corresponding to the video data. The aforementioned display pixel circuit is A first drive transistor that drives the indicator light-emitting element, A first selection transistor connected to the node between the anode of the indicator light-emitting element and the first drive transistor, Includes, The aforementioned dummy pixel circuit is A second drive transistor that drives the aforementioned reference light-emitting element, A second selection transistor connected to the node between the anode of the reference light-emitting element and the second drive transistor, Includes, The aforementioned reference light-emitting element is removed from control according to the video data. The aforementioned display drive circuit is The second selection transistor is switched from the off state to the on state to apply current or voltage to the reference light-emitting element without passing through the second drive transistor, thereby obtaining a reference signal that shows the current-voltage characteristics of the reference light-emitting element. The first selection transistor is switched from the off state to the on state to apply current or voltage to the indicator light-emitting element without passing through the first drive transistor, thereby obtaining a characteristic signal that indicates the current-voltage characteristics of the indicator light-emitting element. Based on a signal proportional to the difference between the reference signal and the characteristic signal, a signal indicating the degree of degradation of the display light-emitting element is generated. Display device.

2. A display device according to claim 1, The dummy pixel circuit has the same circuit configuration as the display pixel circuit. Display device.

3. A display device according to claim 1, The display driving circuit displays an image corresponding to the video data and sequentially selects all display pixel circuits of the same color as the reference light-emitting element. Based on a signal proportional to the difference between the characteristic signal of the sequentially selected display pixel circuit and the reference signal, a signal indicating the degree of degradation of the display light-emitting element of the display pixel circuit is sequentially generated. Display device.

4. A display device according to claim 1, Includes multiple pixel circuit lines, Each of the plurality of pixel circuit lines includes the dummy pixel circuit and the plurality of display pixel circuits connected to the same control line. The display driving circuit generates a signal indicating the degree of degradation of each display light-emitting element in each of the plurality of pixel circuit lines, based on a signal proportional to the difference between the reference signal of the reference light-emitting element and the characteristic signal of each display light-emitting element. Display device.

5. A display device according to claim 4, Multiple sense lines that transmit signals indicating the current-voltage characteristics of the light-emitting element, Multiple sense scan lines that transmit a selection signal for selecting a pixel circuit to measure the current-voltage characteristics of the light-emitting element, Includes, Each of the aforementioned plurality of sense lines is connected to a single pixel circuit array, Each of the aforementioned plurality of sense scan lines is connected to a single pixel circuit row, The aforementioned pixel circuit line is a pixel circuit row connected to the same sense scan line. Display device.

6. A display device according to claim 1, Multiple pixel circuit lines, It includes a first dummy pixel circuit and a second dummy pixel circuit, each including a reference light-emitting element, Each of the aforementioned plurality of pixel circuit lines includes a plurality of display pixel circuits connected to the same control line. The aforementioned display drive circuit is A first process is performed to generate a signal indicating the degree of degradation of each display light-emitting element in the first pixel circuit group, based on a signal proportional to the difference between the reference signal of the reference light-emitting element of the first dummy pixel circuit and the characteristic signal of each display light-emitting element in the first pixel circuit line group. A second process is performed to generate a signal indicating the degree of degradation of each display light-emitting element in the second pixel circuit group, based on a signal proportional to the difference between the reference signal of the reference light-emitting element of the second dummy pixel circuit and the characteristic signal of each display light-emitting element in the second pixel circuit line group. The first and second processes are executed in parallel. Display device.

7. A display device according to claim 6, The first dummy pixel circuit is connected to the control line of the first display pixel circuit line, The second dummy pixel circuit is connected to the control line of the second display pixel circuit line. Display device.

8. A display device according to claim 6, Multiple sense lines that transmit signals indicating the current-voltage characteristics of the light-emitting element, Multiple sense scan lines that transmit a selection signal for selecting a pixel circuit to measure the current-voltage characteristics of the light-emitting element, Includes, Each of the aforementioned plurality of sense lines is connected to a single pixel circuit array, Each of the aforementioned plurality of sense scan lines is connected to a single pixel circuit row, The aforementioned pixel circuit line is a series of pixel circuits connected to the same sense line. Display device.

9. A display device according to claim 1, Multiple display pixel circuits, Multiple reference light-emitting elements, Includes, 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 degradation of the display light-emitting element based on a signal proportional to the difference between the reference signal and characteristic signal of a reference light-emitting element of the same color and a display light-emitting element. Display device.

10. A display device according to claim 1, The display driving circuit includes a correlated double sampling circuit that generates a signal indicating the degree of degradation of the display light-emitting element based on a signal proportional to the difference between the reference signal and the characteristic signal. Display device.

11. A display device according to claim 1, The display driving circuit displays a frame image corresponding to the video data during a first period within a frame period, and acquires a reference signal indicating the current-voltage characteristics of the reference light-emitting element or a characteristic signal indicating the current-voltage characteristics of the display light-emitting element during a second period within the frame period that is different from the first period. Display device.

12. A display device according to claim 11, The display driving circuit acquires characteristic signals indicating the current-voltage characteristics of the display light-emitting elements of a plurality of display pixel circuits within the one-frame period. Display device.

13. A display device according to claim 11, The display driving circuit acquires a reference signal indicating the current-voltage characteristics of the reference light-emitting element at predetermined frame intervals, and acquires characteristic signals indicating the current-voltage characteristics of the display light-emitting elements of a plurality of display pixel circuits during the predetermined frame intervals. Display device.

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