WO2015198597A1 - 表示装置及びその駆動方法 - Google Patents
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- WO2015198597A1 WO2015198597A1 PCT/JP2015/003176 JP2015003176W WO2015198597A1 WO 2015198597 A1 WO2015198597 A1 WO 2015198597A1 JP 2015003176 W JP2015003176 W JP 2015003176W WO 2015198597 A1 WO2015198597 A1 WO 2015198597A1
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
- G09G3/3225—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix
- G09G3/3233—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/04—Structural and physical details of display devices
- G09G2300/0421—Structural details of the set of electrodes
- G09G2300/0426—Layout of electrodes and connections
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G2300/0809—Several active elements per pixel in active matrix panels
- G09G2300/0814—Several active elements per pixel in active matrix panels used for selection purposes, e.g. logical AND for partial update
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G2300/0809—Several active elements per pixel in active matrix panels
- G09G2300/0819—Several active elements per pixel in active matrix panels used for counteracting undesired variations, e.g. feedback or autozeroing
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G2300/0809—Several active elements per pixel in active matrix panels
- G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G2300/0809—Several active elements per pixel in active matrix panels
- G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
- G09G2300/0861—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2300/00—Aspects of the constitution of display devices
- G09G2300/08—Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
- G09G2300/0809—Several active elements per pixel in active matrix panels
- G09G2300/0842—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor
- G09G2300/0861—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes
- G09G2300/0866—Several active elements per pixel in active matrix panels forming a memory circuit, e.g. a dynamic memory with one capacitor with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes by means of changes in the pixel supply voltage
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0243—Details of the generation of driving signals
- G09G2310/0245—Clearing or presetting the whole screen independently of waveforms, e.g. on power-on
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/02—Addressing, scanning or driving the display screen or processing steps related thereto
- G09G2310/0262—The addressing of the pixel, in a display other than an active matrix LCD, involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependent on signals of two data electrodes
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2310/00—Command of the display device
- G09G2310/08—Details of timing specific for flat panels, other than clock recovery
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2320/00—Control of display operating conditions
- G09G2320/02—Improving the quality of display appearance
- G09G2320/0233—Improving the luminance or brightness uniformity across the screen
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G2330/00—Aspects of power supply; Aspects of display protection and defect management
- G09G2330/02—Details of power systems and of start or stop of display operation
- G09G2330/028—Generation of voltages supplied to electrode drivers in a matrix display other than LCD
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- H—ELECTRICITY
- H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
- H10K—ORGANIC ELECTRIC SOLID-STATE DEVICES
- H10K59/00—Integrated devices, or assemblies of multiple devices, comprising at least one organic light-emitting element covered by group H10K50/00
- H10K59/10—OLED displays
- H10K59/12—Active-matrix OLED [AMOLED] displays
- H10K59/131—Interconnections, e.g. wiring lines or terminals
Definitions
- the present invention relates to a display device having a plurality of pixels and a driving method thereof.
- a display device using an organic electroluminescence (EL) element As a display device using a current-driven light emitting element, a display device using an organic electroluminescence (EL) element is known.
- the organic EL display device using the self-emitting organic EL element does not require a backlight necessary for a liquid crystal display device, and is optimal for thinning the device. Moreover, since there is no restriction
- Patent Document 1 discloses a configuration in which a power line in an active matrix display device is improved to increase pixel definition.
- the present disclosure provides a display device that can suppress a decrease in display uniformity and a driving method thereof.
- One embodiment of a display device is a display device including a plurality of pixels, each of the plurality of pixels emitting light according to a supplied current and driving for supplying current to the light-emitting element.
- the display device includes a transistor and a storage capacitor connected between a gate and a source of the driving transistor.
- the display device causes the light-emitting element to emit light in some of the plurality of pixels and the voltage of the storage capacitor to be used in the other part.
- a control unit is provided that applies the drain voltage of the driving transistor of another part of the pixel independently of the drain voltage of the part of the pixel.
- the display device or the like in the present disclosure it is possible to suppress a decrease in display uniformity.
- FIG. 1 is a block diagram showing a schematic configuration of an organic EL display device according to an embodiment.
- FIG. 2 is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to the embodiment.
- FIG. 3 is a timing chart showing the operation of the pixel in the organic EL display device according to the embodiment.
- FIG. 4A is an explanatory diagram illustrating a state of a pixel in the Vth detection period illustrated in FIG.
- FIG. 4B is an explanatory diagram illustrating a state of the pixel in the light emission period illustrated in FIG. 3.
- FIG. 5 is a graph showing IV characteristics of the drive transistor. 6A and 6B are diagrams for explaining the display state of the organic EL display device according to the embodiment.
- FIG. 1 is a block diagram showing a schematic configuration of an organic EL display device according to an embodiment.
- FIG. 2 is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to the embodiment.
- FIG. 6A is a timing chart showing the operation of the organic EL display device.
- FIG. It is a figure which shows typically the state of the display area in the time t20.
- FIG. 7 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to a comparative example.
- FIG. 8 is an explanatory diagram showing the state of the pixels in the Vth detection period in the organic EL display device according to the comparative example.
- FIG. 9 is a diagram schematically showing the arrangement of the second VDD line and the RESET line in the organic EL display device according to the embodiment.
- FIG. 10 is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to the first modification.
- FIG. 10 is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to the first modification.
- FIG. 11 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to Modification 2.
- FIG. 12 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to Modification 3.
- FIG. 13 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to Modification 4.
- FIG. 14 is an external view of a thin flat TV incorporating the display device of the present disclosure.
- FIG. 1 is a block diagram showing a schematic configuration of the organic EL display device according to the present embodiment.
- FIG. 2 is a circuit diagram showing a circuit configuration of a pixel in the organic EL display device according to the present embodiment.
- the organic EL display device 1 shown in FIG. 1 includes a display area 2 and a control unit 3, and pixels 4 to be described later are arranged in a matrix in the display area 2.
- the control unit 3 performs various controls on the plurality of pixels 4 arranged in the display area 2, and includes a timing control circuit 5, a scanning line driving circuit 6, a signal line driving circuit 7, and a voltage control circuit 8. .
- the plurality of pixels 4 arranged corresponding to the same scanning line are appropriately referred to as “display lines”.
- the timing control circuit 5 performs, for example, synchronization between the scanning line driving circuit 6 and the signal line driving circuit 7, timing control of the operation of the organic EL display device 1 for each frame, and the like.
- the scanning line driving circuit 6 drives the scanning lines in the display area 2 based on the control signal from the timing control circuit 5. Specifically, the scanning line driving circuit 6 outputs the SCAN signal, the ENABLE signal, and the RESET1 signal to the RESET3 signal to each pixel 4 based on the vertical synchronizing signal and the horizontal synchronizing signal at least in display line units. In the pixel example shown in FIG. 2, these signals are output to the SCAN line 61, the ENABLE line 62, and the RESET lines 63 to 65, and are used to control on and off of the connection destination transistors (switches).
- the signal line drive circuit 7 drives the signal line (DATA line 71 in FIG. 2) in the display area 2 based on the control signal from the timing control circuit 5. More specifically, the signal line drive circuit 7 outputs a signal voltage DATA indicating the luminance of the pixel 4 to each pixel 4 based on the video signal and the horizontal synchronization signal. This signal voltage DATA is output to the DATA line 71 shown in FIG. 2 and used to indicate the luminance of the connection destination pixel 4.
- the voltage control circuit 8 supplies various power supply voltages to the display area 2.
- the various power supply voltages are VDD1 (positive power supply voltage), VDD2 (positive power supply voltage), VSS (negative power supply voltage), VREF, and VRST.
- the positive power supply voltage and the negative power supply voltage do not indicate the level of the voltage value with respect to GND, but indicate only the positive power supply voltage> the negative power supply voltage.
- the organic EL display device 1 includes, for example, a CPU (Central Processing Unit), a storage medium such as a ROM (Read Only Memory) storing a control program, a working memory such as a RAM (Random Access Memory), although not illustrated. And a communication circuit.
- the signal voltage DATA may be generated by the CPU executing a control program, for example.
- the pixel 4 includes an organic EL element 9 that emits light in response to the supplied current, a driving transistor Qd that supplies a current (pixel current) to the organic EL element 9, and a gate connected to the source of the driving transistor Qd.
- the organic EL element 9 emits light with a luminance corresponding to the signal voltage DATA supplied through the DATA line 71.
- the pixel 4 further includes a drive transistor Qd, a transistor Qscan, a transistor Qref, a transistor Qrst, a transistor Qenb (first switch), and a transistor Qdet (second switch).
- the SCAN line 61, the ENABLE line 62, the RESET line 63, the RESET line 64, the RESET line 65 (control line), and the DATA line 71 are connected to the pixel 4, and various power lines are provided.
- the VREF line 83, the first VDD line 81 (first power supply line), the VSS line 82 (common wiring), the VRST line 84, and the second VDD line 85 (second power supply line) are connected.
- the VREF line 83 is a power supply line for supplying a reference voltage VREF (for example, 3 V) which is a reference for detecting the threshold voltage of the drive transistor Qd.
- the first VDD line 81 is a power supply line that is supplied with a positive power supply voltage VDD1 (for example, 20 V) and supplies a current (pixel current) that causes the organic EL element 9 to emit light.
- the VSS line 82 is a power supply line to which a negative power supply voltage VSS (for example, 0 V) is supplied and connected to the cathode 92 of the organic EL element 9.
- the VRST line 84 is a power supply line that is supplied with a voltage VRST (for example, ⁇ 5 V) and resets the voltages of the organic EL element 9 and the storage capacitor Cs.
- the second VDD line 85 is a power supply line that is supplied with a positive power supply voltage VDD2 (for example, 20 V or 10 V) and supplies a current (threshold detection current) for detecting the threshold voltage of the drive transistor Qd.
- the organic EL display device 1 includes the first VDD line 81 and the second VDD line 85 as power supply lines for supplying a positive power supply voltage to the plurality of pixels 4.
- each of the first VDD line 81 and the second VDD line 85 is extended in the arrangement direction (row direction) of the pixel columns in the display region 2 so as to correspond to each display line, for example. That is, the plurality of first VDD lines 81 arranged in the display area 2 are arranged apart from each other in the display area 2. Similarly, the plurality of second VDD lines 85 arranged in the display area 2 are arranged apart from each other in the display area 2. The plurality of first VDD lines 81 and the plurality of second VDD lines 85 arranged in the display area 2 are arranged in parallel to each other. However, the arrangement of the first VDD line 81 and the second VDD line 85 outside the display area 2 is not questioned.
- the plurality of first VDD lines 81 arranged in the display area 2 may be connected to each other outside the display area 2 or may be arranged apart from each other outside the display area 2. The same applies to the plurality of second VDD lines 85 arranged in the display area 2.
- the plurality of first VDD lines 81 may be configured in a mesh shape.
- the voltage VDD1 of the first VDD line 81 and the voltage VDD2 of the second VDD line 85 are the saturation region operation when the maximum voltage of the gate of the drive transistor Qd is Vgpeak and the threshold voltage of the drive transistor Qd is Vth. To make it happen, it is set as follows.
- VDD1 Vgpeak-Vth
- VDD2 VREF-Vth
- VDD1> VDD2 from Vgpeak> VREF.
- the first VDD line 81 can supply a current (pixel current) in a light emitting operation described later.
- the second VDD line 85 can supply a current (threshold detection current) for detecting the threshold voltage of the drive transistor Qd in a threshold voltage compensation operation to be described later.
- the organic EL element 9 emits light with a light emission amount corresponding to the amount of current supplied from the drive transistor Qd.
- the cathode 92 is connected to the VSS line 82, and the anode 91 is connected to the source of the drive transistor Qd.
- the drive transistor Qd is a voltage-driven drive element that controls the amount of current supplied to the organic EL element 9, and causes the organic EL element 9 to emit light by flowing a current (pixel current) through the organic EL element 9.
- the gate of the drive transistor Qd is connected to the first electrode of the storage capacitor Cs, and the source is connected to the second electrode of the storage capacitor Cs and the anode 91 of the organic EL element 9. Therefore, the drive transistor Qd can pass a current (pixel current) through the organic EL element 9 with a current amount corresponding to the voltage held in the holding capacitor Cs. That is, the organic EL display device 1 can cause the organic EL element 9 to emit light with a luminance corresponding to the voltage held in the storage capacitor Cs by the light emitting operation.
- the threshold voltage of the drive transistor Qd may vary from pixel 4 to pixel 4 due to an initial distribution or a threshold voltage shift over time when a TFT substrate provided with the drive transistor Qd is formed.
- the influence can be suppressed by the threshold voltage compensation operation.
- This threshold voltage compensation operation is an operation of setting a voltage obtained by adding a voltage corresponding to the signal voltage DATA to a voltage corresponding to the threshold voltage of the corresponding driving transistor Qd to the storage capacitor Cs in each of the pixels 4.
- the holding capacitor Cs holds the threshold voltage of the driving transistor Qd, and further holds the signal voltage DATA in which the threshold voltage of the driving transistor Qd is compensated by the held threshold voltage and the signal voltage DATA supplied from the DATA line 71.
- the second electrode of the storage capacitor Cs is connected to a node where the source (VSS line 82 side) of the driving transistor Qd and the anode 91 of the organic EL element 9 are connected.
- the first electrode of the storage capacitor Cs is connected to the gate of the drive transistor Qd.
- the first electrode of the storage capacitor Cs is connected to the VREF line 83 via the transistor Qref.
- the transistor Qscan switches between conduction and non-conduction between the DATA line 71 for supplying the signal voltage DATA and the first electrode of the storage capacitor Cs.
- the transistor Qscan has one of the drain and the source connected to the DATA line 71, the other of the drain and the source connected to the first electrode of the storage capacitor Cs, and the gate connected to the SCAN line 61. It is a transistor.
- the transistor Qscan has a function for writing a voltage corresponding to the signal voltage DATA supplied via the DATA line 71 to the storage capacitor Cs.
- the transistor Qref switches between conduction and non-conduction between the VREF line 83 that supplies the reference voltage VREF and the first electrode of the storage capacitor Cs.
- the transistor Qref is a switching device in which one of the drain and the source is connected to the VREF line 83, the other of the drain and the source is connected to the first electrode of the storage capacitor Cs, and the gate is connected to the RESET line 63. It is a transistor.
- the transistor Qref has a function of applying the reference voltage (VREF) to the first electrode (gate of the driving transistor Qd) of the storage capacitor Cs.
- the transistor Qrst switches between conduction and non-conduction between the second electrode of the storage capacitor Cs and the VRST line 84. Specifically, in the transistor Qrst, one of the drain and the source is connected to the VRST line 84, the other of the drain and the source is connected to the anode 91 of the organic EL element 9 and the second electrode of the storage capacitor Cs, and the gate is RESET. A switching transistor connected to line 64. In other words, the transistor Qrst has a function of applying a reset voltage (VRST) to the anode 91 of the organic EL element 9 and the second electrode of the storage capacitor Cs (source of the driving transistor Qd).
- VRST reset voltage
- the transistor Qenb switches between conduction and non-conduction between the first VDD line 81 and the drain of the drive transistor Qd.
- the transistor Qenb has one of a drain and a source connected to the first VDD line 81 (VDD1), the other drain and the source connected to the drain of the driving transistor Qd, and a gate connected to the ENABLE line 62. Switching transistor.
- the transistor Qenb is turned on when the pixel 4 emits light, that is, when the drive transistor Qd supplies a current (pixel current) to the organic EL element 9, and thereby the first VDD line 81 and the drain of the drive transistor Qd Is made conductive.
- the transistor Qdet switches between conduction and non-conduction between the second VDD line 85 and the drain of the driving transistor Qd. Specifically, in the transistor Qdet, one of the drain and the source is connected to the second VDD line 85 (VDD2), the other of the drain and the source is connected to the drain of the driving transistor Qd, and the gate is connected to the RESET line 65. Switching transistor. The transistor Qdet is turned on when the threshold voltage compensation operation of the pixel 4 is performed, so that the second VDD line 85 and the drain of the driving transistor Qd are brought into conduction.
- the organic EL display device 1 can compensate the threshold voltage of the drive transistor Qd with high accuracy. Therefore, the organic EL display device 1 can suppress a decrease in display uniformity. This mechanism will be described in detail in the following operation description.
- the plurality of switching transistors constituting the pixel 4 will be described below as n-type TFTs, but are not limited thereto.
- the plurality of switching transistors may be p-type TFTs. Further, in the plurality of switching transistors, an n-type TFT and a p-type TFT may be mixedly used.
- FIG. 3 is a timing chart showing the operation of the pixel 4 in the organic EL display device 1 according to the present embodiment. Specifically, in the figure, in order from the top, the SCNA signal supplied to the SCAN line 61, the ENABLE signal supplied to the ENABLE line 62, the RESET1 signal supplied to the RESET line 63, and the RESET line 64 are supplied. The RESET2 signal and the RESET3 signal supplied to the RESET line 65 are shown.
- 4A is an explanatory diagram illustrating a state of the pixel 4 in the Vth (threshold) detection period illustrated in FIG.
- 4B is an explanatory diagram illustrating a state of the pixel 4 in the light emission period illustrated in FIG.
- EL reset period> In the EL reset period from time t10 to t11 shown in FIG. 3, only the voltage level of the RESET2 signal becomes HIGH, so that only the transistor Qrst becomes conductive.
- the charge held in the capacitive component CEL of the organic EL element 9 can be reset. That is, the source voltage of the drive transistor Qd is quickly set to the voltage VRST of the VRST line 84.
- the RESET2 signal rises at time t10, and the RESET1 signal rises at time t11. Even if the RESET2 signal rises at time t11 and the RESET1 signal rises at time t10, The charge held in the holding capacitor Cs can be reset.
- the gate-source voltage of the drive transistor Qd at time t12 is an initial value that can secure an initial drain current necessary for performing the threshold voltage compensation operation performed after the Cs reset period. It needs to be set to voltage. That is, the initial voltage needs to be higher than the threshold voltage Vth of the drive transistor Qd and not to cause the organic EL element 9 to emit light. Therefore, the potential difference between the voltage VREF on the VREF line 83 and the voltage VRST on the VRST line 84 is set to a voltage that is higher than the maximum threshold voltage of the drive transistor Qd (VREF ⁇ VRST> Vth). Further, the voltage VREF and the voltage VRST are set to voltages satisfying the following two expressions so that the organic EL element 9 does not emit light when the forward current threshold voltage of the organic EL element 9 is VEL.
- the voltage level of the RESET2 signal changes from HIGH to LOW, so that the transistor Qrst is turned off (off state).
- the threshold detection current i prog starts to flow from the drain side to the source side of the drive transistor Qd. That is, when the threshold detection current i prog starts to flow from the second VDD line 85 at time t13, charging of the storage capacitor Cs and the capacitance component CEL of the organic EL element 9 is started. Thereafter, as the storage capacitor Cs and the capacitor component CEL are charged, the source voltage of the drive transistor Qd increases. Specifically, the source voltage of the drive transistor Qd changes so that the gate-source voltage of the drive transistor Qd becomes the threshold voltage Vth of the drive transistor Qd.
- the voltage level of the RESET3 signal changes from HIGH to LOW, so that the transistor Qdet is turned off (off state), and the supply of the threshold detection current i prog is stopped.
- the threshold detection current i prog has a sufficiently small current level at time t14 and is smaller than the maximum value of the pixel current i pix during the light emission period. Therefore, Wd / L, which is the size parameter of Qenb and Qdet, may be smaller than Qenb, and the area required for the pixel circuit can be reduced.
- W is the channel width of the TFT
- L is the channel length of the TFT.
- the voltage level of the RESET1 signal changes from HIGH to LOW, so that the transistor Qref is turned off (off state), and the voltage of the storage capacitor Cs is held.
- the threshold voltage Vth of the drive transistor Qd detected during the period from time t14 to t15 is held as the voltage of the storage capacitor Cs.
- the organic EL display device 1 performs the threshold voltage compensation operation by turning off the transistors Qscan, Qenb, and Qrst and turning on the transistors Qref and Qdet.
- the organic EL display device 1 supplies the voltage VDD2 to the drain of the drive transistor Qd while fixing the gate voltage of the drive transistor Qd and keeping the source of the drive transistor Qd floating. The threshold voltage of Qd is detected.
- the threshold voltage detected by the threshold voltage compensation operation may differ from the original threshold voltage depending on various conditions (the length of the Vth detection period, the voltage drop of the power supply voltage, etc.). Therefore, in the following, there is a case where the threshold voltage detected by the threshold voltage compensation operation is distinguished as Vth_m and the original threshold voltage is classified as Vth_t.
- the original threshold voltage is determined by, for example, device parameters of the drive transistor Qd.
- the RESET1 signal may fall at the time t14, and the RESET3 signal may fall during the period from the time t14 to t15.
- the voltage level of the SCAN signal changes from HIGH to LOW, so that the transistor Qscan is turned off (off state).
- the potential difference between the signal voltage DATA (described as VDATA in the equation) and the voltage VREF of the VREF line 83 is stored in the storage capacitor Cs. capacity divided voltage is held at the capacitor C s of the capacitor component CEL of the capacitance C EL and the holding capacitor Cs of the EL element 9. That is, the gate-source voltage Vgs of the driving transistor is expressed by the following formula 1.
- the pixel current i pix at this time is expressed by the following Expression 2.
- the pixel current i pix is expressed by the following formula 3.
- ⁇ is a coefficient determined depending on the mobility ⁇ of the driving transistor Qd, the gate insulating film capacitance Cox, the channel length L, and the channel width W, and is expressed by the following Expression 4.
- the organic EL display device 1 compensates the threshold voltage of the drive transistor Qd with higher accuracy. Can emit light.
- the organic EL display device 1 can emit light by compensating the threshold voltage of the drive transistor Qd of each pixel 4.
- the threshold voltage Vth_m detected by the threshold voltage compensation operation needs to be as close as possible to the original threshold voltage Vth_t in order to emit light by accurately compensating the threshold voltage of the driving transistor.
- the threshold voltage Vth_m detected by the threshold voltage compensation operation may change depending on various conditions. In other words, the detection accuracy of the threshold voltage Vth_m may change. In such a case, even if the same signal voltage DATA is supplied to all the pixels 4, the display uniformity of the display area 2 may be reduced.
- the organic EL display device 1 suppresses a decrease in display uniformity by equalizing the detection accuracy of the threshold voltage Vth_m detected by the threshold voltage compensation operation.
- this mechanism will be described with reference to FIGS. 5 to 8 together with FIGS. 4A and 4B.
- FIG. 5 is a graph showing the IV characteristics of the drive transistor Qd.
- FIG. 6 is a diagram for explaining the display state of the organic EL display device 1 according to the present embodiment, and (a) is a timing chart showing the Vth detection and light emission operation of the organic EL display device 1.
- (B) is a figure which shows typically the state of the display area in the time t20 of (a).
- FIG. 7 is a circuit diagram illustrating a circuit configuration of the pixel 904 in the organic EL display device according to the comparative example.
- FIG. 8 is an explanatory diagram showing the state of the pixel 904 in the Vth detection period in the organic EL display device according to the comparative example.
- the organic EL display device according to the comparative example is substantially the same as the organic EL display device 1 according to the present embodiment, but without the second VDD line 85 and the transistor Qdet, in the threshold voltage compensation operation, the transistor Qenb However, the threshold detection current i prog is supplied by conducting the first VDD line 81 and the drain of the drive transistor Qd.
- FIG. 5 shows the drain current with respect to the gate-source voltage Vgs of the drive transistor Qd when the drain-source voltage Vds of the drive transistor Qd is Vds1 and when the Vds is Vds2 (where Vds2 ⁇ Vds1). Ids is shown.
- the drain current Ids of the drive transistor Qd not only depends on the gate-source voltage Vgs of the drive transistor Qd, but also depends on the drain-source voltage Vds of the drive transistor Qd.
- the threshold voltage Vth_m of the drive transistor Qd which is the voltage held in the storage capacitor Cs, is the end point of the Vth detection period (time t15 in FIG. 3). Is the gate-source voltage Vgs of the driving transistor Qd.
- the threshold voltage Vth_m detected in the Vth detection period depends on the drain-source voltage Vds of the driving transistor Qd. Therefore, in order to make the detection accuracy of the threshold voltage uniform in the display region 2, it is necessary to make the drain voltage of the drive transistor Qd in the threshold voltage compensation operation uniform in the display region 2.
- the organic EL display device 1 performs the light emission operation and the threshold voltage compensation operation in the display line sequence (row sequence). That is, the control unit 3 drives and scans the display area 2 in the display line sequence (row sequence).
- the organic EL display device 1 causes the organic EL element 9 to emit light in a part (partial display lines) of the plurality of pixels 4 (t17 in FIG. 3).
- the operation (light emission operation) is executed, and in the other part (other part of the display lines), the voltage of the storage capacitor Cs is changed to become the threshold voltage of the drive transistor Qd (FIG. 3).
- the voltage of the first VDD line 81 varies relatively greatly depending on the pixel current i pix flowing in the pixel 4 in the light emission period shown in FIG. 4B.
- the voltage of the first VDD line 81 varies relatively greatly due to a voltage drop caused by the pixel current i pix . Therefore, the pixel 904 in the comparative example shown in FIG.
- the detection accuracy of the threshold voltage Vth_m detected at this time is influenced by the drain voltage of the drive transistor Qd as described above.
- the drain of the drive transistor Qd is electrically connected to the first VDD line 81 in the Vth detection period. Therefore, the detection accuracy of the threshold voltage Vth_m is affected by the voltage of the first VDD line 81.
- the pixel 904 in the comparative example has a problem that the detection accuracy of the threshold voltage Vth_m varies relatively depending on the display pattern of the display area. Arise.
- control unit 3 causes the other part of the plurality of pixels 4 to perform the light emission operation and the other part to perform the threshold voltage compensation operation.
- the drain voltage of the drive transistor Qd of the pixel 4 is applied independently of the drain voltage of the partial pixel 4.
- the organic EL display device 1 can suppress a decrease in display uniformity.
- the organic EL display device 1 has a first VDD line 81 (first power line) and a second VDD line 85 (second line) for supplying a power voltage to the plurality of pixels 4.
- Power line Each pixel 4 includes a transistor Qenb (first switch) provided in a current path of a current (pixel current i pix ) supplied to the organic EL element 9 through the first VDD line 81, a second VDD line 85, A transistor Qdet (second switch) that switches between conduction and non-conduction with the drain of the drive transistor Qd;
- control unit 3 turns on the switch Qenb and turns off the switch Qdet in the partial pixel 4, and turns off the switch Qenb and turns on the switch Qdet in the other partial pixel 4.
- drain voltage of the drive transistor Qd of the other part of the pixels 4 is applied independently of the drain voltage of the part of the pixels 4.
- the drain voltage of the drive transistor Qd in the Vth detection period is applied independently of the voltage of the first VDD line 81 that is affected by the light emission operation (such as a voltage drop due to the pixel current i pix ). Therefore, the accuracy of the threshold voltage Vth_m detected by the threshold voltage compensation operation can be made uniform.
- the voltage is applied independently means that the fluctuation of one voltage hardly affects the fluctuation of the other voltage. For example, when one voltage changes from V11 to V12 (however, different from V11) by ⁇ V1, this means that the other voltage remains V21 and does not change. In this case, even if the other voltage changes from V21 to V22 by ⁇ V2, these timings only need to be different. That is, these timings may be irrelevant. Further, the relationship between V11 and V21 is not questioned and may be different from each other or may be equivalent.
- the organic EL display device 1 has a plurality of pixels 4, and each of the plurality of pixels 4 emits light according to the supplied pixel current i pix. It has an element 9 (light emitting element), a drive transistor Qd that supplies a pixel current i pix to the organic EL element 9, and a storage capacitor Cs connected between the gate and source of the drive transistor Qd.
- the organic EL element 9 emits light in some of the plurality of pixels 4, and the voltage of the storage capacitor Cs becomes the threshold voltage of the driving transistor Qd in the other part.
- a control unit 3 is provided that applies the drain voltage of the drive transistor Qd of another part of the pixels 4 independently of the drain voltage of the part of the pixels 4 in the changed display state.
- the organic EL display device 1 can suppress a decrease in display uniformity.
- the second VDD line 85 may be provided corresponding to each display line (row) of the plurality of pixels 4, and may be arranged as shown in FIG. 9, for example.
- FIG. 9 is a diagram schematically showing the arrangement of the second VDD line 85 and the RESET line 65 in the organic EL display device 1 according to the present embodiment.
- the second VDD line 85 is provided corresponding to each display line (each row) of the plurality of pixels 4, and the RESET line 65 (control line) corresponding to the display line. And may be arranged in parallel.
- the RESET line 65 is provided corresponding to each display line of the plurality of pixels 4 arranged in a matrix, and is a wiring for instructing the timing for switching between conduction and non-conduction of the switch Qdet (second switch). It is. That is, the RESET line 65 is supplied with a RESET3 signal for turning on and off the transistor Qdet. That is, the voltage of the RESET line 65 varies according to the HIGH and LOW of the RESET3 signal.
- the second VDD line 85 provided corresponding to the display line performing the threshold voltage compensation operation has a voltage level of HIGH to LOW or VTH detection period (time t13 to t14 in FIG. 3) of the display line.
- the Vth detection operations of the plurality of pixels connected to the second VDD line 85 are executed at different timings. Therefore, since the second VDD line 85 always supplies current, the voltage of the second VDD line 85 may not be stabilized. That is, in such a case, there is a possibility that display uniformity may be reduced.
- the second VDD line 85 in parallel with the RESET line 65, the pixels connected to the second VDD line 85 become a row unit during the Vth detection period, and at the end of the Vth detection period, the second VDD line 85 is The supplied current is reduced, the voltage of the second VDD line 85 is stabilized, and a decrease in display uniformity due to the threshold voltage compensation operation can be suppressed.
- the drive transistor Qd is an n-type transistor
- the organic EL element 9 has an anode 91 connected to the source of the drive transistor Qd and a cathode 92 common to at least some of the plurality of pixels 4. It is connected to a VSS line 82 which is a common wiring provided.
- the difference between the drain voltage (VDD2) of the drive transistor Qd in the threshold voltage compensation operation and the reference voltage (VSS) is the difference between the drive transistor Qd in the light emission operation. It may be smaller than the difference between the drain voltage (VDD1) and the reference voltage (VSS).
- FIG. 10 is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to the first modification.
- the drive transistor Qd is a p-type transistor
- the organic EL element 9 has an anode 91 connected to the drain of the drive transistor Qd via the transistor Qenb2 and a cathode 92 at least of the plurality of pixels 4. It is connected to a VSS line 82 which is a common wiring provided in part in common.
- a VSS line 82 first power line
- a VSS line 185 second power line
- VDD is supplied to the first VDD line 81 as a positive power supply voltage.
- the organic EL display device including such a pixel 104 performs the threshold voltage compensation operation by turning off the transistors Qscan, Qenb, and Qenb2 and turning on the transistors Qref, Qmrg, and Qdet. That is, in the organic EL display device, in the pixel 104 that is emitting light, the transistors Qenb and Qenb2 (first switch) are turned on and the transistor Qdet (second switch) is turned off to perform the threshold voltage compensation operation. In the pixel 104, by turning off the transistor Qenb2 and turning on the transistor Qdet, the drain voltage of the drive transistor Qd of the pixel 104 that is performing the threshold voltage compensation operation is independent of the drain voltage of the pixel 104 that is performing the light emission operation. Apply to.
- the organic EL display device has the same effect as the above embodiment. That is, a decrease in display uniformity can be suppressed.
- the drain voltage of the drive transistor Qd in the threshold voltage compensation operation depends on the voltage of the VSS line 82 (first power supply line).
- the voltage of the VSS line 82 varies relatively greatly depending on the pixel current i pix flowing in the pixel 104 during the light emission period. Therefore, there is a problem that the detection accuracy of the detected threshold voltage Vth_m is lowered due to the fluctuation of the drain voltage of the driving transistor Qd in the threshold voltage compensation operation.
- the organic EL display device includes the VSS line 185 (second power supply line) and the transistor Qdet, so that the drain voltage of the driving transistor Qd of the pixel 104 that is performing the threshold voltage compensation operation. Is applied independently of the drain voltage of the pixel 104 that is emitting light. Therefore, since the organic EL display device can make the detection accuracy of the threshold voltage Vth_m uniform, the organic EL display device can suppress a decrease in display uniformity.
- FIG. 11 is an example in which the transistor Qenb2 in Modification Example 1 is excluded using the diode characteristics of the organic EL element 9, and is a circuit diagram illustrating a circuit configuration of a pixel in the organic EL display device according to Modification Example 2.
- the drive transistor Qd is a p-type transistor
- the organic EL element 9 has an anode 91 connected to the drain of the drive transistor Qd and a cathode 92 shared by at least some of the plurality of pixels 4. It is connected to a VSS line 82 which is a common wiring provided.
- a VSS line 82 first power line
- a VSS line 185 second power line
- VDD is supplied to the first VDD line 81 as a positive power supply voltage.
- the organic EL display device including such a pixel 104A performs the threshold voltage compensation operation by turning off the transistors Qscan and Qenb and turning on the transistors Qref, Qmrg, and Qdet. That is, in the organic EL display device, in the pixel 104A that is performing the light emission operation, the transistor Qenb (first switch) is turned on and the transistor Qdet (second switch) is turned off to perform the threshold voltage compensation operation. Then, by turning off the transistor Qenb and turning on the transistor Qdet, the drain voltage of the driving transistor Qd of the pixel 104A performing the threshold voltage compensation operation is applied independently of the drain voltage of the pixel 104A performing the light emitting operation. To do.
- the organic EL display device has the same effect as the above embodiment. That is, a decrease in display uniformity can be suppressed.
- the drain voltage of the drive transistor Qd in the threshold voltage compensation operation depends on the voltage of the VSS line 82 (first power supply line).
- the voltage of the VSS line 82 varies relatively greatly depending on the pixel current i pix flowing in the pixel 104A during the light emission period. Therefore, there is a problem that the detection accuracy of the detected threshold voltage Vth_m is lowered due to the fluctuation of the drain voltage of the driving transistor Qd in the threshold voltage compensation operation.
- the organic EL display device includes the VSS line 185 (second power supply line) and the transistor Qdet so that the drain voltage of the drive transistor Qd of the pixel 104A performing the threshold voltage compensation operation. Is applied independently of the drain voltage of the pixel 104A that is emitting light. Therefore, since the organic EL display device can make the detection accuracy of the threshold voltage Vth_m uniform, the organic EL display device can suppress a decrease in display uniformity.
- the organic EL element 9 is in a reverse-biased state (anode voltage ⁇ cathode voltage), so that deterioration of the organic EL element 9 over time can be suppressed.
- the configuration of the pixel may be, for example, a configuration as shown in FIG.
- FIG. 12 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to Modification 3.
- the drive transistor Qd is an n-type transistor
- the organic EL element 9 has a cathode 92 connected to the drain of the drive transistor Qd and an anode 91 shared by at least some of the plurality of pixels 204. It is connected to a VSS line 82 which is a common wiring provided.
- a first VDD line 81 first power line
- a second VDD line 285 second power line
- the organic EL display device including such a pixel 204 performs the threshold voltage compensation operation by turning off the transistors Qscan and Qenb and turning on the transistors Qref, Qmrg, and Qdet, as in the second modification. Execute. In other words, in the organic EL display device, in the pixel 204 that is performing the light emitting operation, the transistor Qenb (first switch) is turned on and the transistor Qdet (second switch) is turned off to perform the threshold voltage compensation operation. Then, by turning off the transistor Qenb and turning on the transistor Qdet, the drain voltage of the driving transistor Qd of the pixel 204 that is performing the threshold voltage compensation operation is applied independently of the drain voltage of the pixel 204 that is performing the light emitting operation. To do.
- the organic EL display device according to this modification described above also has the same effect as the above embodiment. That is, a decrease in display uniformity can be suppressed.
- the drain voltage of the drive transistor Qd in the threshold voltage compensation operation depends on the voltage of the first VDD line 81 (first power supply line). To do. At this time, the voltage of the first VDD line 81 varies relatively greatly depending on the pixel current i pix flowing in the pixel 204 during the light emission period. Therefore, there is a problem that the detection accuracy of the detected threshold voltage Vth_m is lowered due to the fluctuation of the drain voltage of the driving transistor Qd in the threshold voltage compensation operation.
- the organic EL display device includes the second VDD line 285 (second power supply line) and the transistor Qdet, so that the drain of the drive transistor Qd of the pixel 204 that performs the threshold voltage compensation operation.
- the voltage is applied independently of the drain voltage of the pixel 204 that is emitting light. Therefore, since the organic EL display device can make the detection accuracy of the threshold voltage Vth_m uniform, the organic EL display device can suppress a decrease in display uniformity.
- the configuration of the pixel may be, for example, a configuration as shown in FIG.
- FIG. 13 is a circuit diagram illustrating a circuit configuration of a pixel in an organic EL display device according to Modification 4.
- the driving transistor Qd is a p-type transistor
- the organic EL element 9 has a cathode 92 connected to the source of the driving transistor Qd and an anode 91 shared by at least some of the plurality of pixels 304. It is connected to a first VDD line 81 which is a common wiring provided.
- a VSS line 82 first power line
- a VSS line 385 second power line
- VDD is supplied to the first VDD line 81 as a positive power supply voltage.
- the organic EL display device including such a pixel 304 performs threshold voltage compensation operation by turning off the transistors Qscan, Qenb, and Qrst and turning on the transistors Qref and Qdet. Execute. That is, in the organic EL display device, in the pixel 304 that is performing the light emitting operation, the transistor Qenb (first switch) is turned on and the transistor Qdet (second switch) is turned off to perform the threshold voltage compensation operation. Then, by turning off the transistor Qenb and turning on the transistor Qdet, the drain voltage of the driving transistor Qd of the pixel 304 performing the threshold voltage compensation operation is applied independently of the drain voltage of the pixel 304 performing the light emitting operation. To do.
- the organic EL display device according to this modification described above also has the same effect as the above embodiment. That is, a decrease in display uniformity can be suppressed.
- the drain voltage of the drive transistor Qd in the threshold voltage compensation operation depends on the voltage of the VSS line 82 (first power supply line).
- the voltage of the VSS line 82 varies relatively greatly with the pixel current i pix flowing through the pixel 304 of the light emission period. Therefore, there is a problem that the detection accuracy of the detected threshold voltage Vth_m is lowered due to the fluctuation of the drain voltage of the driving transistor Qd in the threshold voltage compensation operation.
- the organic EL display device includes the VSS line 385 (second power supply line) and the transistor Qdet, so that the drain voltage of the driving transistor Qd of the pixel 304 performing the threshold voltage compensation operation. Is applied independently of the drain voltage of the pixel 304 that is emitting light. Therefore, since the organic EL display device can make the detection accuracy of the threshold voltage Vth_m uniform, the organic EL display device can suppress a decrease in display uniformity.
- the difference between the drain voltage (VSS22) of the drive transistor Qd in the threshold voltage compensation operation and the reference voltage (VDD) is the difference of the drive transistor Qd in the light emission operation. It may be smaller than the difference between the drain voltage (VSS1) and the reference voltage (VDD).
- the organic EL display device including the organic EL element 9 as a light emitting element has been described as the display device according to the present disclosure.
- the present disclosure is not limited thereto, and the display device including a current driven light emitting element If it is.
- a method for driving a display device is a method for driving a display device having a plurality of pixels, and each of the plurality of pixels includes a light-emitting element that emits light according to a supplied current; A driving transistor that supplies current to the light emitting element, and a storage capacitor connected between the gate and source of the driving transistor.
- a driving method of the display device causes the light emitting element to emit light in some of the plurality of pixels.
- the drain voltage of the driving transistor of the other part of the pixel is changed to the drain voltage of the part of the pixel.
- the display device further includes a first power supply line and a second power supply line for supplying a power supply voltage to the plurality of pixels, and each of the plurality of pixels further includes the first power supply line via the first power supply line.
- the display device may include a first switch provided in a current path of a current supplied to the light emitting element, and a second switch that switches between conduction and non-conduction between the second power supply line and the drain of the driving transistor.
- a program for causing the computer to function as a characteristic control unit included in the display device or as a program for causing the computer to execute characteristic steps included in the driving method.
- Such a program can be distributed via a computer-readable non-transitory recording medium such as a CD-ROM (Compact Disc-Read Only Memory) or a communication network such as the Internet. .
- the present disclosure can be used for a display device, and in particular, for an FPD display device such as a television as shown in FIG.
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Abstract
Description
以下、本実施の形態に係る有機EL表示装置について、具体的に説明する。
まず、本実施の形態に係る有機EL表示装置の構成について、図1及び図2を用いて説明する。図1は、本実施の形態に係る有機EL表示装置の概要構成を示すブロック図である。図2は、本実施の形態に係る有機EL表示装置における画素の回路構成を示す回路図である。
次に、図2に示す画素4の回路構成について、説明する。
VDD2>VREF-Vth
次に、上述のように構成された有機EL表示装置1の動作について、図3、図4A及び図4Bを用いて説明する。なお、以下で説明する各動作は制御部3により実行される。図3は、本実施の形態に係る有機EL表示装置1における画素4の動作を示すタイミングチャートである。具体的には、同図には上から順に、SCAN線61に供給されるSCNA信号、ENABLE線62に供給されるENABLE信号、RESET線63に供給されるRESET1信号、RESET線64に供給されるRESET2信号、及び、RESET線65に供給されるRESET3信号が示されている。図4Aは、図3に示すVth(閾値)検出期間における画素4の状態を示す説明図である。図4Bは、図3に示す発光期間における画素4の状態を示す説明図である。
図3に示す時刻t10~t11のELリセット期間では、RESET2信号の電圧レベルのみがHIGHとなることにより、トランジスタQrstのみが導通状態となる。
次に、時刻t11において、RESET1信号の電圧レベルがLOWからHIGHに変化する。すなわち、時刻t11において、トランジスタQrefが導通状態(オン状態)となる。これにより、時刻t12までの時刻において、保持容量Csに保持された電荷をリセットすることができる。つまり、駆動トランジスタQdのゲート電圧がVREF線83の電圧VREFに設定される。
VREF<VSS+VEL+Vth
次に、時刻t13において、RESET3信号の電圧レベルがLOWからHIGHに変化する。すなわち、時刻t13において、トランジスタQdetが導通状態(オン状態)となる。
次に、時刻t15において、SCAN信号の電圧レベルがLOWからHIGHに変化することにより、トランジスタQscanが導通状態(オン状態)となる。これにより、保持容量Csの第1電極には、DATA線71から供給される信号電圧DATAが供給される。
次に、時刻t17において、ENABLE信号の電圧レベルがLOWからHIGHに変化することにより、トランジスタQenbが導通状態(オン状態)となる。これにより、図4Bに示すように、駆動トランジスタQdのドレイン側からソース側に向かって画素電流ipixが流れ始める。つまり、駆動トランジスタQdは、保持容量Csで保持された電圧に応じて、第1VDD線81から有機EL素子9に画素電流ipixを供給する。これにより、有機EL素子9が発光する。
上述したように、駆動トランジスタの閾値電圧を精度良く補償して発光するためには、閾値電圧補償動作によって検出される閾値電圧Vth_mが、本来の閾値電圧Vth_tにできるだけ近いことが必要である。しかしながら、閾値電圧補償動作によって検出される閾値電圧Vth_mは種々の条件によって変化する場合がある。言い換えると、当該閾値電圧Vth_mの検出精度が変化する場合がある。このような場合には、全ての画素4に同一の信号電圧DATAが供給された場合であっても、表示領域2の表示均一性が低下する虞がある。
図5には、駆動トランジスタQdのドレイン-ソース間電圧VdsがVds1の場合と、当該VdsがVds2の場合(ただし、Vds2<Vds1)とにおける、駆動トランジスタQdのゲート-ソース間電圧Vgsに対するドレイン電流Idsが示されている。
ここで、本実施の形態に係る有機EL表示装置1は、例えば、図6の(a)に示すように、表示ライン順次(行順次)に発光動作及び閾値電圧補償動作を実行する。つまり、制御部3は、表示領域2を、表示ライン順次(行順次)に駆動走査する。これにより、図6の(b)に示すように、有機EL表示装置1は、複数の画素4の一部(一部の表示ライン)では有機EL素子9を発光させる発光期間(図3のt17以降)の動作(発光動作)が実行され、他の一部(他の一部の表示ライン)では保持容量Csの電圧を駆動トランジスタQdの閾値電圧になるように変化させるVth検出期間(図3のt13~t14)の動作(閾値電圧補償動作)が実行される。言い換えると、有機EL表示装置1は、複数の画素4のうち一部(一部の表示ライン)は図4Bに示す状態となり、他の一部(他の一部の表示ライン)は図4Aに示す状態となる。
以上説明したように、本実施の形態に係る有機EL表示装置1は、複数の画素4を有し、当該複数の画素4の各々は、供給された画素電流ipixに応じて発光する有機EL素子9(発光素子)と、有機EL素子9に画素電流ipixを供給する駆動トランジスタQdと、駆動トランジスタQdのゲート-ソース間に接続された保持容量Csとを有する。ここで、当該有機EL表示装置1は、複数の画素4の一部では、有機EL素子9を発光させ、他の一部では、保持容量Csの電圧を駆動トランジスタQdの閾値電圧になるように変化させている表示状態において、他の一部の画素4の駆動トランジスタQdのドレイン電圧を、一部の画素4の当該ドレイン電圧と独立に印加する制御部3を備える。
なお、画素の構成は、上述した構成に限らず、閾値電圧補償動作において、駆動トランジスタQdのゲートの電圧が固定され、かつ、駆動トランジスタQdのソースがフローティングにされた状態で、駆動トランジスタQdがオンするような構成であればよく、例えば、図10に示すような構成であってもよい。図10は、変形例1に係る有機EL表示装置における画素の回路構成を示す回路図である。
また、図11に示すような構成であってもよい。図11は、有機EL素子9のダイオード特性を利用して変形例1におけるトランジスタQenb2を排除した例であり、変形例2に係る有機EL表示装置における画素の回路構成を示す回路図である。
また、画素の構成は、例えば、図12に示すような構成であってもよい。図12は、変形例3に係る有機EL表示装置における画素の回路構成を示す回路図である。
また、画素の構成は、例えば、図13に示すような構成であってもよい。図13は、変形例4に係る有機EL表示装置における画素の回路構成を示す回路図である。
以上、本開示に係る有機EL表示装置について説明したが、本開示は、上記の実施の形態及び各変形例に限定されるものではない。
2 表示領域
3 制御部
4、104、104A、204、304、904 画素
5 タイミング制御回路
6 走査線駆動回路
7 信号線駆動回路
8 電圧制御回路
9 有機EL素子
61 SCAN線
62 ENABLE線
63~65 RESET線
71 DATA線
81 第1VDD線
82、185、385 VSS線
83 VREF線
84 VRST線
85、285 第2VDD線
91 アノード
92 カソード
Cs、Cs1、Cs2 保持容量
CEL 容量成分
Qd 駆動トランジスタ
Qdet、Qenb、Qenb2、Qmrg、Qref、Qrst、Qscan トランジスタ
Claims (14)
- 複数の画素を有する表示装置であって、
前記複数の画素の各々は、
供給された電流に応じて発光する発光素子と、
前記発光素子に電流を供給する駆動トランジスタと、
前記駆動トランジスタのゲート-ソース間に接続された保持容量とを有し、
前記表示装置は、
前記複数の画素の一部では、前記発光素子を発光させ、他の一部では、前記保持容量の電圧を前記駆動トランジスタの閾値電圧になるように変化させている表示状態において、前記他の一部の画素の前記駆動トランジスタのドレイン電圧を、前記一部の画素の当該ドレイン電圧と独立に印加する制御部を備える
表示装置。 - 前記表示装置は、さらに、前記複数の画素に対して電源電圧を供給するための第1電源線及び第2電源線を有し、
前記複数の画素の各々は、さらに、
前記第1電源線を介して前記発光素子に供給される電流の電流経路に設けられた第1スイッチと、
前記第2電源線と前記駆動トランジスタのドレインとの導通及び非導通を切り換える第2スイッチとを有する
請求項1に記載の表示装置。 - 前記制御部は、前記表示状態において、前記一部の画素では、前記第1スイッチをオンかつ前記第2スイッチをオフさせ、前記他の一部の画素では、前記第1スイッチをオフかつ前記第2スイッチをオンすることにより、前記他の一部の画素の前記駆動トランジスタのドレイン電圧を、前記一部の画素の当該ドレイン電圧と独立に印加する
請求項2に記載の表示装置。 - 前記表示装置は、さらに、行列状に配置された前記複数の画素の行毎に対応して設けられ、前記第2スイッチの導通及び非導通を切り換えるタイミングを指示するための制御線を有し、
前記第2電源線は、前記複数の画素の行毎に対応して設けられ、当該行に対応する前記制御線と平行に配置されている
請求項2又は3に記載の表示装置。 - 前記第1スイッチ及び前記第2スイッチの各々は、薄膜トランジスタであり、
当該薄膜トランジスタのチャネル幅をW、当該薄膜トランジスタのチャネル長をLとした場合、W/Lは前記第1スイッチよりも前記第2スイッチの方が小さい
請求項2~4のいずれか1項に記載の表示装置。 - 前記駆動トランジスタはn型トランジスタであり、
前記発光素子は、アノードが前記駆動トランジスタのソースに接続され、カソードが前記複数の画素の少なくとも一部に共通に設けられた共通配線に接続されている
請求項1~5のいずれか1項に記載の表示装置。 - 前記駆動トランジスタはp型トランジスタであり、
前記発光素子は、カソードが前記駆動トランジスタのソースに接続され、アノードが前記複数の画素の少なくとも一部に共通に設けられた共通配線に接続されている
請求項1~5のいずれか1項に記載の表示装置。 - 前記共通配線の電圧を基準電圧とすると、前記表示状態において、前記他の一部の画素の前記駆動トランジスタのドレイン電圧と当該基準電圧との差分は、前記一部の画素の当該ドレイン電圧と当該基準電圧との差分より小さい
請求項6又は7に記載の表示装置。 - 前記駆動トランジスタはp型トランジスタであり、
前記発光素子は、アノードが前記駆動トランジスタのドレインに接続され、カソードが前記複数の画素の少なくとも一部に共通に設けられた共通配線に接続されている
請求項1~5のいずれか1項に記載の表示装置。 - 前記駆動トランジスタはn型トランジスタであり、
前記発光素子は、カソードが前記駆動トランジスタのドレインに接続され、アノードが前記複数の画素の少なくとも一部に共通に設けられた共通配線に接続されている
請求項1~5のいずれか1項に記載の表示装置。 - 前記表示装置は、さらに、前記複数の画素に対して電源電圧を供給するための第1電源線及び第2電源線を有し、
前記発光素子は、有機EL(Electro Luminescence)素子であり、
前記複数の画素の各々は、さらに、
前記第2電源線と前記駆動トランジスタのドレインとの導通及び非導通を切り換える第2スイッチを有し、
前記第1電源線と前記駆動トランジスタのドレインとは、前記有機EL素子を介して常時接続されている
請求項1に記載の表示装置。 - 前記制御部は、前記表示状態において、前記他の一部の画素では、前記発光素子のアノード電圧を当該発光素子のカソード電圧より低くする
請求項11に記載の表示装置。 - 複数の画素を有する表示装置の駆動方法であって、
前記複数の画素の各々は、供給された電流に応じて発光する発光素子と、前記発光素子に電流を供給する駆動トランジスタと、前記駆動トランジスタのゲート-ソース間に接続された保持容量とを有し、
前記表示装置の駆動方法は、
前記複数の画素の一部では、前記発光素子を発光させ、他の一部では、前記保持容量の電圧を前記駆動トランジスタの閾値電圧になるように変化させている表示状態において、前記他の一部の画素の前記駆動トランジスタのドレイン電圧を、前記一部の画素の当該ドレイン電圧と独立に印加する
表示装置の駆動方法。 - 前記表示装置は、さらに、前記複数の画素に対して電源電圧を供給するための第1電源線及び第2電源線を有し、
前記複数の画素の各々は、さらに、前記第1電源線を介して前記発光素子に供給される電流の電流経路に設けられた第1スイッチと、前記第2電源線と前記駆動トランジスタのドレインとの導通及び非導通を切り換える第2スイッチとを有し、
前記表示装置の駆動方法は、前記一部の画素において、
前記第1スイッチをオフかつ前記第2スイッチをオンした状態で、前記保持容量に前記駆動トランジスタの閾値電圧に対応した電圧を保持させる保持ステップと、
前記保持ステップの後、前記第1スイッチをオフかつ前記第2スイッチをオフした状態で、前記発光素子の輝度を示す信号電圧が前記閾値電圧によって補償された電圧を前記保持容量に保持させる書き込みステップと、
前記書き込みステップの後、前記第1スイッチをオンかつ前記第2スイッチをオフすることにより、前記発光素子を発光させる発光ステップとを含み、
前記保持ステップでは、前記他の一部の画素の前記駆動トランジスタのドレイン電圧を、前記一部の画素の当該ドレイン電圧と独立に印加する
請求項13に記載の表示装置の駆動方法。
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