KR102633412B1 - Organic light emitting display device - Google Patents

Abstract

The object of the present invention is to provide an organic light emitting display device that varies the alpha voltage supplied to the sensing line in an initialization period that comes after the sensing period during the blank period according to the black data voltage supplied to the data lines in the initialization period. is to provide.

Description

Organic light emitting display device {ORGANIC LIGHT EMITTING DISPLAY DEVICE}

The present invention relates to an organic light emitting display device, and particularly to an organic light emitting display device capable of performing external compensation through a sensing line.

Flat panel display devices (FPD) are used in various types of electronic products, including mobile phones, tablet PCs, and laptops. Flat panel displays include Liquid Crystal Display Devices (LCDs), Organic Light-Emitting Display Devices (OLEDs), and recently, Electrophoretic Display Devices (EPDs) are also widely used. It is being used.

Among these, organic light emitting displays (OLEDs) use self-luminous elements that emit light on their own, and thus have advantages such as fast response speed, high luminous efficiency, high luminance, and large viewing angle.

In organic light emitting display devices, differences in characteristics, such as the threshold voltage (Vth) and mobility of the driving transistor, occur for each pixel due to reasons such as process deviation and degradation. Accordingly, the amount of current driving each organic light emitting diode is different, which causes luminance differences between pixels.

In order to solve the above problem, Republic of Korea Patent Publication No. 10-2013-0066449 (hereinafter referred to as “prior art document”) compensates for changes in the characteristics of the driving transistor included in each pixel through correction of input image data. An external compensation method is disclosed.

Figure 1 is an example diagram showing the phenomenon in which the first line of a panel applied to a conventional organic light emitting display device is displayed darkly during the initialization period after the sensing period.

In a conventional organic light emitting display device, sensing for external compensation is performed during a blank period of one frame period. In particular, the sensing is performed during a sensing period of the blank period.

During the initialization period after the sensing period during the blank period, high-level Alfre voltages are supplied through sensing lines connected to the sensing transistor, and accordingly, a first node voltage is applied to the first node between the driving transistor and the organic light-emitting diode. This is approved. The first node is connected to the source of the driving transistor.

During the initialization period, a high-level black data voltage is supplied to the data lines. In this case, the first node voltage rises and then falls together with the black data voltage due to a kick-back phenomenon caused by the black data voltage.

When the voltage of the first node increases, the gate-source voltage (Vgs) of the driving transistor decreases. When the gate-source voltage (Vgs) of the driving transistor decreases, the amount of current supplied to the organic light emitting diode connected to the driving transistor decreases, and thus, the brightness of the organic light emitting diode decreases.

The phenomenon described above occurs in the first horizontal line 1HL provided at the top of the panel 10.

To elaborate, after the sensing period, during the initialization period, the brightness of subpixels arranged on the first horizontal line 1HL is reduced due to the kickback phenomenon. Accordingly, as shown in FIG. 1, a phenomenon occurs in which the first horizontal line provided in the display area 11 of the panel 10 appears dark.

The purpose of the present invention proposed to solve the above-mentioned problem is to reduce the Alfre voltage supplied to the sensing line in the initialization period that comes after the sensing period during the blank period to the black data voltage supplied to the data lines in the initialization period. To provide an organic light emitting display device that varies according to the.

An organic light emitting display device according to the present invention for achieving the above-described technical problem includes a panel having subpixels defined by gate lines and data lines, a data driver supplying data voltages to the data lines, and It includes a gate driver that supplies gate pulses to the gate lines and a control unit that controls the data driver and the gate driver. Each of the subpixels includes a switching transistor connected to a gate line and a data line; An organic light emitting diode that outputs light, a driving transistor that controls the size of the current output to the organic light emitting diode according to the data voltage transmitted through the switching transistor, and a first node between the driving transistor and the organic light emitting diode; It is connected to a sensing line, is turned on or off by a sensing pulse, and includes a sensing transistor that senses characteristics of the driving transistor during a sensing period during a blank period. The data driver supplies an alpha voltage to the sensing line during an initialization period issued after the sensing period during the blank period, and supplies a black data voltage to the data lines for a period shorter than the period during which the alpha voltage is supplied. supply. The data driver varies the alpha voltage according to the black data voltage.

Conventionally, the luminance of subpixels provided in the first horizontal line of the panel was reduced by the black data voltage supplied to the data lines during the initialization period that comes after the sensing period during the blank period. This phenomenon is called the kickback phenomenon.

However, according to the present invention, the kickback phenomenon can be prevented because the alpha voltage supplied to the sensing line connected to each subpixel varies depending on the black data voltage.

In particular, in the present invention, when the black data voltage rises, the Alfre voltage is polled and then rises. Accordingly, in each of the subpixels provided in the first horizontal line of the panel, the voltage of the first node between the driving transistor and the organic light emitting diode is not shaken by the black data voltage, and therefore, the voltage of the first node provided in the first horizontal line of the panel is not shaken by the black data voltage. The luminance of subpixels is not reduced.

To elaborate, when the black data voltage rises to a high level, the Alfre voltage is momentarily polled and then raised, so that the voltage of the first node does not fluctuate, and accordingly, the first node The luminance of subpixels provided in the horizontal line is not reduced.

Figure 1 is an example diagram showing the phenomenon in which the first line of a panel applied to a conventional organic light emitting display device is displayed darkly during the initialization period after the sensing period.
Figure 2 is an exemplary diagram schematically showing the configuration of an organic light emitting display device according to the present invention.
Figure 3 is an example diagram showing the arrangement structure of subpixels formed in a panel applied to an organic light emitting display device according to the present invention.
Figure 4 is an exemplary diagram showing the structure of a subpixel formed in a panel applied to an organic light emitting display device according to the present invention.
Figure 5 is an exemplary diagram showing the configuration of a control unit applied to the organic light emitting display device according to the present invention.
Figure 6 is an exemplary diagram showing the configuration of a data driver applied to the organic light emitting display device according to the present invention.
Figure 7 is an example diagram showing the waveforms of signals applied to the organic light emitting display device according to the present invention.

The advantages and features of the present invention and methods for achieving them will become clear by referring to the embodiments described in detail below along with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and will be implemented in various different forms. These embodiments only serve to ensure that the disclosure of the present invention is complete, and those skilled in the art It is provided to fully inform the person of the scope of the invention, and the present invention is only defined by the scope of the claims.

In this specification, it should be noted that when adding reference numbers to components in each drawing, the same components are given the same number as much as possible even if they are shown in different drawings.

The shapes, sizes, ratios, angles, numbers, etc. disclosed in the drawings for explaining embodiments of the present invention are illustrative, and the present invention is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. Additionally, in describing the present invention, if it is determined that a detailed description of related known technologies may unnecessarily obscure the gist of the present invention, the detailed description will be omitted. When 'includes', 'has', 'consists of', etc. mentioned in this specification are used, other parts may be added unless 'only' is used. When a component is expressed in the singular, the plural is included unless specifically stated otherwise.

When interpreting a component, it is interpreted to include the margin of error even if there is no separate explicit description.

In the case of a description of a positional relationship, for example, if the positional relationship of two parts is described as 'on top', 'on the top', 'on the bottom', 'next to', etc., 'immediately' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

In the case of a description of a temporal relationship, for example, if a temporal relationship is described as 'after', 'successfully after', 'after', 'before', etc., 'immediately' or 'directly' Unless used, non-consecutive cases may also be included.

The term ‘at least one’ should be understood to include all possible combinations from one or more related items. For example, 'at least one of the first item, the second item and the third item' means each of the first item, the second item or the third item, as well as two of the first item, the second item and the third item. It means a combination of all items that can be presented from more than one.

Although first, second, etc. are used to describe various components, these components are not limited by these terms. These terms are merely used to distinguish one component from another. Accordingly, the first component mentioned below may also be the second component within the technical spirit of the present invention.

Each feature of the various embodiments of the present invention can be partially or fully combined or combined with each other, various technical interconnections and operations are possible, and each embodiment can be implemented independently of each other or together in a related relationship. It may be possible.

Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. The present invention can be applied to various types of display devices that use external compensation. Below, for convenience of explanation, an organic light emitting display device is described as an example of the present invention.

Figure 2 is an exemplary diagram schematically showing the configuration of an organic light emitting display device according to the present invention, and Figure 3 is an exemplary diagram showing the arrangement structure of subpixels formed in a panel applied to the organic light emitting display device according to the present invention. , FIG. 4 is an exemplary diagram showing the structure of a subpixel formed in a panel applied to an organic light emitting display device according to the present invention.

Before explaining the present invention in detail, the purpose, configuration, and effects of the present invention are summarized as follows.

First, the purpose of the present invention is to prevent a decrease in luminance of the first horizontal line due to the kickback phenomenon by changing the waveform of the VRPRE supplied through the sensing line (SL). Hereinafter, a horizontal line refers to a line formed by subpixels 110 arranged along the gate line. Accordingly, the first horizontal line refers to a line formed by subpixels 110 arranged along the first gate line GL1 in FIG. 2.

For example, as shown in FIG. 1, in a conventional organic light emitting display device, a defect in which the luminance of the first horizontal line 1HL of the panel 10 decreases is caused by subpixels of the first horizontal line 1HL. This occurs because the gate-source voltage (Vgs) of the driving transistors provided in is smaller than the gate-source voltage (Vgs) of the driving transistors provided in the subpixels of other horizontal lines.

The reason why the gate-source voltage (Vgs) of the driving transistors of the first horizontal line becomes small is because the voltage of the first node between the driving transistor and the organic light-emitting diode fluctuates due to a kick-back phenomenon. am. The first node is connected to a sensing transistor that performs a sensing function for external compensation. The reason why the voltage of the first node fluctuates is because a kickback phenomenon occurs due to overlap capacitance between the sensing line to which the sensing transistor is connected and the data line.

As described above, the purpose of the present invention is to prevent or minimize the kickback phenomenon by changing the waveform of the VRPRE.

Second, in order to achieve the above object, the organic light emitting display device according to the present invention is configured to change the waveform of the VRPRE.

For example, in the present invention, when the black data voltage rises, the VRPRE is polled and then raised.

Accordingly, no overlap capacitance is generated due to the overlap of the data line DL and the sensing line SL. Accordingly, the kickback phenomenon due to overlap capacitance can be prevented or minimized.

Third, according to the present invention, the following effects can be expected.

By changing the waveform of the VRPRE, the overlap capacitance between the data line (DL) and the sensing line (SL) is not generated, and therefore, the kickback phenomenon due to the overlap capacitance can be prevented or minimized. there is. Accordingly, the shaking phenomenon of the first nodes provided in the subpixels of the first horizontal line due to the kickback phenomenon may not occur or be minimized. Accordingly, a phenomenon in which the luminance of subpixels of the first horizontal line is reduced can be prevented.

As shown in FIGS. 2 to 4, the organic light emitting display device according to the present invention is provided with subpixels 110 defined by gate lines (GL1 to GLg) and data lines (DL1 to DLd). a panel 100, a data driver 300 supplying data voltages Vdata to the data lines DL1 to DLd, and a gate driver 200 supplying gate pulses to the gate lines GL1 to GLg. , a control unit 400 that controls the data driver 300 and the gate driver 200, and a sensing unit that collects sensing data by performing sensing for external compensation on the subpixels. The sensing unit may be included in the data driver 300 or may be configured independently from the data driver 300. Hereinafter, an organic light emitting display device in which the sensing unit is provided in the data driver 300 will be described as an example of the present invention.

First, in the panel 100, as shown in FIG. 4, there are subpixels 110 and a signal that defines the area in which the subpixels 110 are formed and supplies a driving signal to the pixel driving circuit (PDC). Lines (DL, GL, PLA, PLB, SL, SPL) are formed.

A data voltage is supplied to the data line (DL), a gate pulse is supplied to the gate line (GL), a first driving power source (EVDD) is supplied to the first driving power line (PLA), and the first driving power line (PLA) is supplied. 2 The second driving power supply (EVSS) is supplied to the driving power line (PLB), the Alfre voltage (VRPRE) is supplied to the sensing line (SL), and the sensing transistor ( A sensing pulse (SP) that turns on or off Tsw2) is supplied.

At least three subpixels 110 form one unit pixel 120. In the following description, as shown in Figure 3, four subpixels 110 (red subpixel (R), white subpixel (W), green subpixel (G), and blue subpixel (B). The present invention will be explained by taking the case of forming this single unit pixel 120 as an example. In particular, Figure 3 shows two unit pixels 120 composed of a red subpixel (R), a white subpixel (W), a green subpixel (G), and a blue subpixel (B).

In this case, one sensing line SL may be commonly connected to the unit pixel 120. Accordingly, when d data lines (DL1 to DLd) are formed on the horizontal line of the panel 100, the number (k) of the sensing lines (SL) is d/4. However, the sensing line may be provided for each subpixel.

Each of the plurality of subpixels 110 may include a pixel driving circuit (PDC) and an organic light emitting diode (OLED), as shown in FIG. 4 .

For example, each of the subpixels 110 includes a switching transistor (Tsw1) connected to the gate line (GL) and the data line (DL), an organic light emitting diode (OLED) that outputs light, and the switching transistor (Tsw1) It includes a driving transistor (Tdr) and a sensing transistor (Tsw2) that control the size of the current output to the organic light emitting diode according to the data voltage (Vdata) transmitted through. The sensing transistor (Tsw2) is connected to the first node (n1) and the sensing line (SL) between the driving transistor (Tdr) and the organic light emitting diode (OLED), and is turned on or off by the sensing pulse (SP). The characteristics of the driving transistor are sensed during the sensing period during the blank period. The second node (n2) connected to the gate of the driving transistor is connected to the switching transistor (Tsw1). A storage capacitance (Cst) is formed between the second node (n2) and the first node (n1). Components other than the organic light emitting diode (OLED) form the pixel driving circuit (PDC).

In the above description, the structure of the subpixel 110 for performing external compensation has been described with reference to FIG. 4, but the subpixel 110 may be formed in various structures other than the structure shown in FIG. 4. . The specific structure of the subpixel for performing external compensation and the specific method of external compensation are beyond the scope of the present invention. Accordingly, an example of a subpixel for external compensation and an external compensation method will be briefly described or omitted with reference to FIGS. 3 and 4.

For example, the purpose of the present invention is to prevent a decrease in luminance of the first horizontal line due to a kickback phenomenon in an organic light emitting display device that performs external compensation. Accordingly, the structure of the subpixel for external compensation and the method of performing external compensation can be selected from various subpixel structures and various external compensation methods currently being proposed for external compensation. For example, the structure and method of the subpixel for external compensation and the method of performing external compensation may be applied to structures and methods published in a number of published patents, including Publication No. 10-2013-0066449. In addition, the inventions published in Application No. 10-2013-0150057 and Application No. 10-2013-0149213 filed by the present applicant may be applied.

Second, the gate driver 200 sequentially generates gate pulses in response to the gate control signal (GCS) supplied from the control unit 400 and sequentially supplies them to the gate lines (GL1 to GLg). The gate driver 200 may be formed directly on the panel 100 during the thin film transistor formation process of each subpixel 110, or may be formed in the form of an integrated circuit (IC) and mounted on the panel. The type in which the gate driver 200 is formed directly on the panel 100 is called a gate in panel (GIP: Gate In Panel) type.

Third, the control unit 400 generates a gate control signal (GCS) to control the operation of the gate driver 200 and drives the data driver 300 based on the timing synchronization signal (TSS) input from an external system. Generates a data control signal (DCS) to control each. The specific configuration and function of the control unit 400 will be described in detail with reference to FIG. 5.

Fourth, the data driver 300 is connected to the data lines DL1 to DLd and the sensing lines SL. The data driver 300 supplies the Alfre voltage (VRPRE) to the sensing line during an initialization period issued after the sensing period during the blank period, and operates for a period shorter than the period during which the Alfre voltage (VRPRE) is supplied. During this period, black data voltage is supplied to the data lines DL. Additionally, the data driver 300 performs a function of varying the VRPRE voltage according to the black data voltage. The specific configuration and function of the data driver 300 will be described in detail with reference to FIG. 6.

Fifth, the sensing unit performs a function of collecting sensing data by performing sensing for external compensation on the subpixels. The sensing unit is described with reference to FIG. 6.

Figure 5 is an exemplary diagram showing the configuration of a control unit applied to the organic light emitting display device according to the present invention.

The control unit 400 transmits the sensed image data to be supplied to the pixels formed in the horizontal line on which external compensation is performed to the data driver 300. Sensing for the external compensation is performed during a sensing period during the blank period. The control unit 400 calculates the external compensation value based on the sensing data (Sdata) provided from the sensing unit included in the data driver 300 during the sensing period in which the sensing is performed, and calculates the external compensation value. is stored in the storage unit 450.

In order to perform the above function, the control unit 400 uses the timing synchronization signal (TSS) transmitted from the external system, as shown in FIG. 5, to input image data (ID) transmitted from the external system. ) are rearranged using the external compensation value and supply the rearranged compensated image data (Data) to the data driver 300, and the gate control signal (GCS) is generated using the timing synchronization signal. and a control signal generator 420 for generating the data control signal (DCS) and the power control signal (PCS), and the sensing data (Sdata) transmitted from the sensing unit included in the data driver 300. a calculation unit 410 for calculating the external compensation value to compensate for changes in characteristics of the driving transistor formed in each of the pixels, a storage unit 450 for storing the external compensation value, and the compensation image. It includes an output unit 440 for outputting data and various control signals (DCS, GCS) to the data driver 300 or the gate driver 200. The calculation unit 410 may be formed in the control unit 400, or may be formed independently from the control unit 400. Hereinafter, the organic light emitting display device according to the present invention will be described, taking as an example the case where the calculation unit 410 is included in the control unit 400, as shown in FIG. 5.

Figure 6 is an exemplary diagram showing the configuration of a data driver applied to the organic light emitting display device according to the present invention.

The data driver 300 is connected to the data lines DL1 to DLd and the sensing lines SL1 to SLk. As shown in FIG. 4, when the data driver 300 includes the data voltage output unit 310 and the sensing unit 320, the data voltage output unit 310 is connected to the data line DL. and the sensing unit 320 is connected to the sensing lines SL.

The data voltage output unit 310 changes the compensated image data into the data voltage (Vdata) and outputs the data voltage to the data line.

The data driver 300, in particular, the sensing unit 320 supplies the Alfre voltage (VRPRE) to the sensing line (SL) during an initialization period that occurs after the sensing period during the blank period, and the The black data voltage is supplied to the data lines (DL1 to DLd) for a shorter period than the period during which the VRPRE is supplied. Additionally, the data driver 300, especially the sensing unit 320, varies the VRPRE voltage according to the black data voltage. In this case, the sensing unit 320 may vary the Alfre voltage (VRPRE) according to the data control signal (DCS) transmitted from the control unit 400.

Figure 7 is an exemplary diagram showing the waveforms of signals applied to the organic light emitting display device according to the present invention. Hereinafter, a method of driving an organic light emitting display device according to the present invention will be described with reference to FIGS. 2 to 7.

One frame period includes a display period in which an image is output through the panel 100 and a blank period in which an image is not output.

The blank period includes a sensing period (Sensing Period) in which the threshold voltage or mobility of the driving transistors (Tdr) is sensed, and an initialization period (Initial) formed between the sensing period and the display period.

First, during the display period, gate pulses are sequentially supplied to the gate lines (GL1 to Glg), and data voltages corresponding to one horizontal line are output to the data lines (DL1 to DLd). Accordingly, an image is output to the panel during the display period.

In this case, the Alfre voltage (VRPRE) having a high level may be output to the sensing line (SL). Accordingly, the voltage (Vn1) of the first node can be changed to various values.

Second, when the sensing period arrives during the blank period, sensing is performed on driving transistors (Tdr) provided in any one of the horizontal lines forming the panel. In this case, the mobility or threshold voltage of the driving transistors (Tdr) can be sensed. As described above, various currently used sensing methods may be applied to the sensing method performed during the sensing period.

During the sensing period, sensing data voltages (Sensing Data) may be supplied to the data lines. The Alfre voltage (VRPRE) having a low level is supplied to the sensing line (SL). In this case, the voltage (Vn1) of the first node may be 0V.

The control unit 400 calculates an external compensation value for each subpixel using the sensing data collected during the sensing period. During the frame period that comes after the sensing period, the control unit 400 converts input image data into compensated image data using the calculated external compensation values, and sends the compensated image data to the data driver 300. send to

Third, the data driver 300, especially the sensing unit 320, supplies a VRPRE voltage (VRPRE) to the sensing line in the initialization period issued after the sensing period during the blank period, and the Al A black data voltage (VBdata) is supplied to the data lines for a shorter period than the period during which the free voltage is supplied. In this case, the data driver 300, especially the sensing unit 320, varies the Alfrey voltage according to the black data voltage (VBdata).

For example, when the black data voltage (Vdata) rises, the data driver 300 polls the Alfre voltage and then causes it to rise, as in the area indicated by X1 in FIG. 7.

Accordingly, as shown in FIG. 7, during the initialization period, the voltage Vn1 of the first node does not increase instantaneously due to a kickback phenomenon, but is maintained constant.

Fourth, after the black data voltage (VBdata) is polled, the control unit 400 controls the data driver 300 and the gate driver 200 to output an image to the panel 100. That is, after the black data voltage VBdata is polled, the display period of another frame period begins.

When the black data voltage is polled, the data driver 300 may poll the VRPRE and then cause it to rise, as shown in the area indicated by X2 in FIG. 7 . By the above operation, the voltage Vn1 of the first node can be further stabilized, and the influence between the initialization period and the display period can be reduced.

By changing the waveform of the VRPRE, the overlap capacitance between the data line (DL) and the sensing line (SL) is not generated, and therefore, the kickback phenomenon due to the overlap capacitance can be prevented or minimized. there is. Accordingly, the shaking phenomenon of the first nodes provided in the subpixels of the first horizontal line due to the kickback phenomenon may not occur or be minimized. Accordingly, a phenomenon in which the luminance of subpixels of the first horizontal line is reduced can be prevented.

Those skilled in the art to which the present invention pertains will understand that the present invention can be implemented in other specific forms without changing its technical idea or essential features. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. The scope of the present invention is indicated by the claims described below rather than the detailed description above, and all changes or modified forms derived from the meaning and scope of the claims and their equivalent concepts should be construed as being included in the scope of the present invention. do.

100: panel 200: gate driver
300: data driver 400: timing controller
110: subpixel 120: unit pixel
410: Calculation unit 420: Control signal generation unit
430: data sorting unit 440: output unit
450: storage unit 310: data voltage output unit
320: Sensing unit

Claims (6)

A panel provided with subpixels defined by gate lines and data lines; a data driver that supplies data voltages to the data lines; a gate driver supplying gate pulses to the gate lines; and a control unit that controls the data driver and the gate driver,
Each of the subpixels includes a switching transistor connected to a gate line and a data line; Organic light-emitting diodes that output light; a driving transistor that controls the amount of current output to the organic light emitting diode according to the data voltage transmitted through the switching transistor; And a sensing transistor connected to a first node and a sensing line between the driving transistor and the organic light emitting diode, turned on or off by a sensing pulse, and detecting characteristics of the driving transistor during a sensing period of the blank period. do,
The data driver supplies an alpha voltage to the sensing line during an initialization period issued after the sensing period during the blank period, and supplies a black data voltage to the data lines for a period shorter than the period during which the alpha voltage is supplied. supply,
The data driver varies the alpha voltage according to the black data voltage,
The data driver is,
When the black data voltage rises, an organic light emitting display device polls the Alfre voltage and then rises it. delete According to claim 1,
The data driver is,
When the black data voltage is polled, an organic light emitting display device polls the alpha voltage and then rises it. According to claim 1,
An organic light emitting display device in which the voltage of the first node is maintained constant. According to claim 1,
After the black data voltage is polled, the control unit controls the data driver and the gate driver to output an image to the panel. According to claim 1,
The control unit,
Using the sensing data collected during the sensing period, an external compensation value for each subpixel is calculated, the input image data is converted into compensation image data using the calculated external compensation values, and the compensation image data is converted into the data. An organic light emitting display device that transmits data to a driver.

Images