KR20240106259A - Display device and driving method thereof - Google Patents

Abstract

A display device according to an embodiment of the present specification includes a display panel including subpixels that are each connected to a plurality of power input lines and receive driving power including a reference voltage to display image data; a calculation unit that calculates a luminance change amount for each block by comparing the luminance difference between the image data of the current frame and the image data of the previous frame on a block basis; Based on the luminance change amount for each block, it is determined whether to perform compensation for the first blocks, which are blocks whose luminance does not change, and when compensation is decided, the location information of the second blocks, which are luminance change blocks, and the luminance change amount of the corresponding block are included. a detection unit that detects second block information; and generating a reference voltage compensation value for the reference voltage compensation according to the amount of change in luminance for each block, and generating data of the first blocks according to the distance between the first blocks and the second blocks and the amount of change in luminance of the second blocks. It includes a compensator that generates first compensation values for compensating for each voltage.

Description

Display device and its driving method {DISPLAY DEVICE AND DRIVING METHOD THEREOF}

This specification relates to a display device and its driving method.

Recently, organic light-emitting displays, which have been in the spotlight as display devices, use organic light-emitting diodes (OLEDs: Organic Light Emitting Diodes) that emit light on their own, resulting in faster response speeds and increased contrast ratio, luminous efficiency, brightness, and viewing angle. It has the advantage of being

This organic light emitting display device arranges subpixels including organic light emitting diodes (OLEDs) and driving transistors that drive them in a matrix form, and can display images by controlling the brightness of each subpixel according to the gradation of image data. . Each subpixel is supplied with a high-potential voltage (EVDD), a low-potential voltage (EVSS), and a reference voltage (Vref) for driving the organic light-emitting diode (OLED), and the voltage flowing to the organic light-emitting diode (OLED) is supplied using a driving transistor. Brightness can be controlled by controlling the amount of current.

However, the driving voltage supplied to each subpixel may vary depending on the distance from the power source, and the driving voltage may become unstable even when the luminance of the displayed image changes rapidly. This deviation in driving voltage causes luminance non-uniformity, which has the problem of deteriorating the quality of the image.

Embodiments disclosed in this specification are intended to solve the above-described problems, and provide a display device and a driving method that can improve screen luminance uniformity when displaying an image.

A display device according to an embodiment of the present specification includes a display panel including subpixels that are each connected to a plurality of power input lines and receive driving power including a reference voltage to display image data; a calculation unit that calculates a luminance change amount for each block by comparing the luminance difference between the image data of the current frame and the image data of the previous frame on a block basis; Based on the luminance change amount for each block, it is determined whether to perform compensation for the first blocks, which are blocks whose luminance does not change, and when compensation is decided, the location information of the second blocks, which are luminance change blocks, and the luminance change amount of the corresponding block are included. a detection unit that detects second block information; and generating a reference voltage compensation value for the reference voltage compensation according to the amount of change in luminance for each block, and generating data of the first blocks according to the distance between the first blocks and the second blocks and the amount of change in luminance of the second blocks. It includes a compensator that generates first compensation values for compensating for each voltage.

The detector may perform compensation for the first blocks when the total amount of luminance change for each block is greater than or equal to a reference luminance change.

a power supply unit located on one side of the display panel to apply the driving power; and a source-PCB that transmits the driving power output from the power supply unit to the plurality of power input lines.

The compensation unit may generate a second compensation value to compensate for the data voltage of the first block according to the distance between the input position of the power supply unit and the first block.

The compensation unit may generate a third compensation value to compensate for the data voltage of the first block according to the distance between the source-PCB and the first block.

The compensation unit may generate a second compensation value according to the X-axis distance between the power supply unit and the first block, and generate a third compensation value according to the Y-axis direction distance between the source-PCB and the first block. You can.

The compensation unit may input the reference voltage compensation value to the power supply unit to compensate for the reference voltage output from the power supply unit.

The compensation unit may generate the first compensation value by adding a compensation value according to the horizontal distance and a compensation value according to the vertical distance between the first block and the second block.

The compensation unit combines the first compensation value, a second compensation value generated according to the position of the power supply unit that applies the driving power and the distance between the first block, and the driving power output from the power supply unit to the plurality of The data voltage of the first block can be compensated by summing the third compensation value generated according to the position of the source-PCB transmitted to the power input line and the distance between the first block.

The compensation unit includes: a first LUT storing a reference voltage compensation value corresponding to the sum of the luminance changes for each block; a second LUT storing the first compensation value corresponding to the amount of change in luminance of the second block and the distance between the first block and the second block; a third LUT storing the sum of the luminance changes for each block and the second compensation value corresponding to the distance between the input position of the driving power and the first block; and a fourth LUT storing the sum of the luminance changes for each block and the third compensation value corresponding to the distance between the input position of the data voltage and the first block.

The compensation unit includes: a first LUT storing a reference voltage compensation value corresponding to the sum of the luminance changes for each block; and a second LUT storing the first compensation value corresponding to the amount of change in luminance of the second block and the distance between the first block and the second block.

In a method of driving a display device according to an embodiment of the present specification, a plurality of power input lines for applying driving power including a reference voltage and a plurality of data lines for applying a data voltage are arranged, and the power input lines and the data A method of driving a display device including a display panel including a plurality of subpixels connected to lines to display image data, comprising: comparing a luminance difference between image data of a current frame and image data of a previous frame for each block; determining compensation for first blocks, which are blocks whose luminance does not change, when the total amount of luminance change for each block is greater than or equal to a reference luminance change; When compensation performance is determined, detecting location information of second blocks that are luminance change blocks and the amount of luminance change of the corresponding blocks; generating a reference voltage compensation value for the reference voltage compensation according to the total amount of luminance change for each block; and generating first compensation values for compensating the data voltages of the first blocks according to the distance between the first blocks and the second blocks and the amount of change in luminance of the second blocks.

A method of driving a display device includes generating a second compensation value to compensate for the data voltage of the first block according to the location of the power supply unit that applies the driving power and the distance between the first block; And generating a third compensation value to compensate for the data voltage of the first block according to the distance between the first block and the location of the source-PCB that transmits the driving power output from the power supply to the plurality of power input lines. It may further include a step of doing so.

The method of driving a display device may further include compensating the data voltage of the first block by adding the first compensation value, the second compensation value, and the third compensation value.

The embodiments of this specification have the following effects.

Embodiments of the present specification can improve screen luminance uniformity when displaying an image.

The embodiment of the present specification compensates for the flicker (flicker) that occurs on the screen by compensating for image data in an area where luminance does not change according to the distance between an area where luminance changes rapidly and the surrounding area where luminance does not change when displaying a screen. Flicker and dim phenomena can be reduced.

The embodiment of the present specification compensates for image data by reflecting the position of the power supply unit that applies the driving power and the position of the source-PCB that transmits the driving power output from the power supply unit to the power input line, thereby reducing the flicker (flicker) that occurs on the screen. Flicker and dim phenomena can be reduced.

The effects according to the present specification are not limited to the contents exemplified above, and further various effects are included within the present specification.

1 is a block diagram schematically showing a display device.
FIG. 2 is a schematic configuration diagram of the subpixel shown in FIG. 1.
Figure 3 is a block diagram schematically showing a display device according to an embodiment of the present specification.
FIG. 4 is a circuit diagram illustrating the configuration of the subpixel shown in FIG. 3.
5 to 7 are diagrams for explaining a method of driving the subpixel of FIG. 4.
Figures 8 to 10 are diagrams to explain the screen deterioration phenomenon that occurs when the luminance of some areas changes.
Figure 11 is a block diagram schematically showing a display device according to an embodiment of the present specification.
Figures 12 and 13 are diagrams for explaining the control method of the calculation unit of Figure 11.
FIG. 14 is a diagram illustrating the configuration of LUTs stored in the compensation unit of FIG. 11.
FIG. 15 is a diagram for explaining a method of controlling the compensator of FIG. 11.
Figures 16 and 17 show test results of screen display results according to comparative examples and embodiments.

The advantages and features of the present specification 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 specification is not limited to the embodiments disclosed below and will be implemented in various different forms, but the present embodiments only serve to ensure that the disclosure of the present specification is complete, and that common knowledge in the technical field to which this specification pertains is provided. It is provided to fully inform those who have the scope of the invention, and this specification is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiments of the present specification are illustrative, and the present specification is not limited to the matters shown. Like reference numerals refer to like elements throughout the specification. When 'includes', 'has', 'consists of', etc. mentioned in the 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 between two parts is described as 'on top', 'on top', 'at the bottom', 'next to ~', 'right next to' Alternatively, there may be one or more other parts placed between the two parts, unless 'directly' is used.

First, second, etc. may be used to describe various components, but 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 be the second component within the technical idea of the present specification.

In addition, the pixel circuit and gate driver of the display device described below may include a plurality of transistors. Transistors can be implemented as Oxide TFT (Thin Film Transistor) containing an oxide semiconductor, LTPS TFT containing Low Temperature Poly Silicon (LTPS), etc. Each of the transistors may be implemented as a p-channel TFT or n-channel TFT.

A transistor is a three-electrode device including a gate, source, and drain. The source is an electrode that supplies carriers to the transistor. Within the transistor, carriers begin to flow from the source. The drain is the electrode through which carriers exit the transistor. In a transistor, the flow of carriers flows from the source to the drain. In the case of an n-channel transistor, because the carriers are electrons, the source voltage has a lower voltage than the drain voltage so that electrons can flow from the source to the drain. In an n-channel transistor, the direction of current flows from the drain to the source. In the case of a p-channel transistor (PMOS), since the carrier is a hole, the source voltage is higher than the drain voltage to allow holes to flow from the source to the drain. In a p-channel transistor, current flows from the source to the drain because holes flow from the source to the drain. It should be noted that the source and drain of a transistor are not fixed. For example, the source and drain may change depending on the applied voltage. Therefore, the invention is not limited by the source and drain of the transistor. In the following description, the source and drain of the transistor will be referred to as first and second electrodes.

The gate signal swings between Gate On Voltage and Gate Off Voltage. The gate-on voltage is set to a voltage higher than the threshold voltage of the transistor, and the gate-off voltage is set to a voltage lower than the threshold voltage of the transistor. The transistor is turned on in response to the gate-on voltage, while the transistor is turned-off in response to the gate-off voltage. For an n-channel transistor, the gate-on voltage may be a gate high voltage (Gate High Voltage, VGH), and the gate-off voltage may be a gate low voltage (VGL). The gate-on voltage of the p-channel transistor may be the gate low voltage (VGL), and the gate-off voltage may be the gate high voltage (VGH).

Each pixel of an electroluminescent display device includes a light emitting element and a driving element that drives the light emitting element by generating a pixel current according to a gate-source voltage. The light emitting device includes an anode electrode, a cathode electrode, and an organic compound layer formed between these electrodes. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), and an electron injection layer. EIL), etc. may be included, but are not limited thereto. When a pixel current flows through a light emitting device, holes passing through the hole transport layer (HTL) and electrons passing through the electron transport layer (ETL) move to the light emitting layer (EML), forming excitons, and as a result, the light emitting layer (EML) emits visible light. can do.

Like reference numerals refer to substantially like elements throughout the specification. Hereinafter, embodiments of the present specification will be described in detail with reference to the attached drawings. In the following description, if it is determined that a detailed description of a known function or configuration related to the present specification may unnecessarily obscure the gist of the present specification, the detailed description will be omitted.

The display device according to the present invention can be implemented in a television, video player, personal computer (PC), home theater, automobile electric device, smartphone, etc., but is not limited thereto. The display device according to the present invention may be implemented as a light emitting display device (LED), a quantum dot display device (QDD), a liquid crystal display device (LCD), etc. However, hereinafter, for convenience of explanation, a display device that directly emits light based on an inorganic light-emitting diode or an organic light-emitting diode is taken as an example.

FIG. 1 is a block diagram schematically showing a display device, and FIG. 2 is a configuration diagram schematically showing the subpixel shown in FIG. 1.

As shown in Figures 1 and 2, the display device includes an image supply unit 110, a timing controller 120, a gate driver 130, a data driver 140, a display panel 150, and a power supply unit 180. may include.

The image supply unit 110 may output various driving signals in addition to image data signals supplied from the outside or image data signals stored in internal memory. The image supply unit 110 may supply data signals and various driving signals to the timing controller 120.

The timing controller 120 includes a gate timing control signal (GDC) for controlling the operation timing of the gate driver 130, a data timing control signal (DDC) and a vertical synchronization signal for controlling the operation timing of the data driver 140, Various driving signals such as horizontal synchronization signals can be output. The timing controller 120 may supply the data signal DATA supplied from the image supply unit 110 to the data driver 140 along with the data timing control signal DDC. The timing controller 120 may compensate for image data or control various driving voltages to remove flicker, dim, etc. that occur when displaying image data. The timing controller 120 may be formed in the form of an integrated circuit (IC) and mounted on a printed circuit board, but is not limited to this.

The gate driver 130 may output a scan signal in response to a gate timing control signal (GDC) supplied from the timing controller 120. The gate driver 130 may supply a scan signal to the subpixels SP included in the display panel 150 through the gate lines GL1 to GLm. The gate driver 130 may be formed in the form of an IC or directly on the display panel 150 using a gate in panel method, but is not limited thereto.

The data driver 140 may convert the data signal DATA into an analog data voltage and output the data in response to the data timing control signal DDC supplied from the timing controller 120. The data driver 140 may supply a data voltage to the subpixels SP included in the display panel 150 through the data lines DL1 to DLn. The data driver 140 may be formed in the form of one or more source ICs (S-IC: Source Driver Integrated Circuit) and may be mounted on the display panel 150 or on a printed circuit board, but is not limited thereto.

The power supply unit 180 generates power to drive the display device based on an external input voltage supplied from the outside. For example, the power supply unit 180 may generate a high potential voltage (EVDD), a low potential voltage (EVSS), and a reference voltage (VREF) for driving the subpixel (SP) and output them to the corresponding power line. The power supply unit 180 provides not only the high potential voltage (EVDD) and the low potential voltage (EVSS), but also the voltage required to drive the scan driver 130 (e.g., a gate voltage including the gate high voltage and gate low voltage) or the data driver. The voltage required to drive (140) (drain voltage including drain voltage and half-drain voltage) can be generated and output. This power supply unit 180 may be implemented in the form of one or more ICs that generate power at a predetermined voltage level under the control of the timing controller 120.

Meanwhile, in the above description, the timing controller 120, gate driver 130, data driver 140, etc. were described as if they were individual components. However, depending on how the display device is implemented, one or more of the timing controller 120, gate driver 130, and data driver 140 may be integrated into one IC.

The display panel 150 can display images in response to driving signals including scan signals and data voltages, high potential voltage (EVDD), and low potential power supply (EVSS). Subpixels (SP) of the display panel 150 directly emit light. The subpixels SP may be composed of pixels containing red, green, and blue, or pixels containing red, green, blue, and white.

Referring to FIG. 2, one subpixel (SP) may include a pixel circuit (PC) consisting of a switching transistor, a driving transistor, a capacitor, an organic light emitting diode, etc. The subpixel (SP) receives the high potential voltage (EVDD), low potential power supply (EVSS), and reference voltage (Vref) for driving the organic light emitting diode, and is connected to the data line (DL) and gate line (GL). A driving signal including a scan signal and a data voltage can be input. The subpixel (SP) can receive a data voltage from the data line (DL) when the switching transistor (SW) connected to the gate line (GL) is turned on. The pixel circuit (PC) of the subpixel (SP) receives the high potential voltage (EVDD), low potential voltage (EVSS), and reference voltage (Vref), and operates an organic light emitting diode according to the data voltage input to the data line (DL). Brightness can be controlled by controlling the amount of current flowing through (OLED). The pixel circuit (PC) can be implemented in various forms, including a circuit for supplying driving current to an organic light emitting diode (OLED) and a compensation circuit for compensating for deterioration of a driving transistor, etc.

Figure 3 is a block diagram schematically showing a display device according to an embodiment of the present specification. The display device according to an embodiment of the present specification exemplifies the case where the gate driver 130 is implemented with a gate driver IC (G-IC) and the data driver 140 is implemented with a source driver IC (S-IC). there is.

A display device according to an embodiment of the present specification includes a display panel 150, a gate driving IC (G-IC), a source driving IC (S-IC), a source PCB (S-PCB), and a control PCB (C-PCB). Includes.

The display panel 150 includes a display area (AA) in which subpixels (SP) are arranged to display an image, and a gate driving IC (G-IC) arranged in a non-display area outside the display area (AA). The gate driving IC (G-IC) may be attached to the left, right, or both left and right sides of the display panel 150.

One or more source driving ICs (S-ICs) may be provided and arranged on one side of the display panel 150. The source driver IC (S-IC) is connected to the bonding pad of the display panel 150 using a tape automated bonding (TAB) method or a chip on glass (COG) method. It may also be placed directly on the display panel 150. For example, the source driving IC (S-IC) of FIG. 3 is implemented in a COF method, so that a plurality of source driving ICs (S-ICs) are attached in a row to the bottom of the display panel 150, and each source driving IC (S-IC) connects the display panel 150 and the source PCB (S-PCB) through pad connection. The source driving IC (S-IC) can transmit a driving signal including a data voltage provided from the control PCB (C-PCB) to the display panel 150.

The source PCB (S-PCB) is connected to the display panel 150 from the bottom of the display panel 150 through an FPCB and can be connected to the control PCB (C-PCB) through an FPC (Flexible Plat Cable) connection. This source PCB (S-PCB) is directly connected to the source driver IC (S-IC) and transmits the control signal applied from the control PCB (C-PCB) to the source driver IC (S-IC) and the gate driver IC (G-IC). IC).

The source PCB (S-PCB) may include a first power supply unit 180a that supplies power required to drive the display panel 150. The first power supply unit 180a of the source PCB (S-PCB) can generate driving power such as high potential voltage (EVDD) and reference voltage (Vref) according to the power control signal input from the timing controller 120. there is. The driving power generated by the power supply unit 180a may be applied to a plurality of power input lines to which subpixels (SP) are connected through a source PCB (S-PCB).

The control PCB (C-PCB) is placed at the bottom of the display panel 150 and can be connected to the source PCB (S-PCB) through a cable (FPC). This control PCB (C-PCB) may include a timing controller 120 and memory 125. The memory 125 can store various setting values or calculation data necessary for driving the display panel 150. Additionally, the memory 125 stores an algorithm for compensating image data, compensation data, and can store various setting values required for algorithm calculation and compensation.

In a display device including this configuration, each subpixel (SP) receives a high potential voltage (EVDD), a reference voltage (Vref), etc. from the first power supply unit 180a of the source PCB (S-PCB), and operates the source. It can emit light depending on the data voltage input from the IC (S-IC). However, since each subpixel (SP) has a different wiring distance from the first power supply unit 180a and the source PCB (S-PCB), there may be a difference in the power supplied during driving.

Since the first power supply unit 180a is provided on one side of the source PCB (S-PCB), one end of the source PCB (S-PCB) on which the first power supply unit 180a is mounted and the Depending on the distance between the other ends, the size of the driving power may vary. In addition, when applying driving power to a plurality of power input lines connected to subpixels (SP) on the source PCB (S-PCB), the longer the distance from the source PCB (S-PCB), the more unstable the power may become. . Accordingly, as the distance from the first power supply unit 180a and the source PCB (S-PCB) increases, image quality deterioration phenomena such as screen flicker and screen darkening may worsen. .

FIG. 4 is a circuit diagram illustrating the configuration of the subpixel SP shown in FIG. 3.

In the following description, the first electrode of the transistor may be one of the source electrode and the drain electrode, and the second electrode of the transistor may be the other one of the source electrode and the drain electrode.

One subpixel (SP) is supplied with a high potential voltage (EVDD), a low potential voltage (EVSS), and a reference voltage (Vref), and receives first and second scan signals (Scan1, Scan2), an emission signal (EM), and A data voltage signal (Vdata) can be input.

One subpixel (SP) includes OLED (Organic Light Emitting Diodes), a driving TFT (DT), a capacitor (Cst), a first light-emitting TFT (ET1), a second light-emitting TFT (ET2), and first to third switching TFTs. It may include (T1~T3).

The driving TFT (DT) and switching TFTs (ET1, ET2, T1 to T3) may be composed of n-type TFT, p-type TFT, or a combination of n-type TFT and p-type TFT. The subpixel (SP) according to an embodiment of the present specification exemplifies a subpixel (SP) composed only of p-type TFTs, but the type and number of TFTs are not limited to the disclosed embodiment.

OLED (OLED) emits light by the driving current supplied from the driving TFT (DT). The anode electrode of the OLED is connected to the fifth node (N5), and the cathode electrode of the OLED is connected to a wiring provided with a low potential voltage (EVSS).

The gate electrode of the driving TFT (DT) is connected to the second node (N2), the first electrode is connected to a wire provided with a high potential voltage (EVDD), and the second electrode is connected to the third node (N3). connected. The driving TFT (DT) can generate driving current in response to the data voltage signal (Vdata).

The first switching TFT (T1) applies the data voltage signal (Vdata) to the first node (N1) to which the first electrode of the capacitor (Cst) is connected. The first switching TFT (T1) has a gate electrode connected to the input line of the first scan signal (Scan1), a first electrode connected to the data line to which the data voltage signal (Vdata) is supplied, and a second electrode connected to the first node (N1). It may include electrodes. Accordingly, the first switching TFT (T1) responds to the first scan signal (Scan1) at the turn-on level and transmits the data voltage signal (Vdata) supplied to the data line to the first node ( Applies to N1).

The second switching TFT (T2) connects the third node (N3) to which the second electrode of the capacitor (Cst) and the drain electrode of the driving TFT (DT) are connected. The second switching TFT (T2) may include a gate electrode connected to the input line of the second scan signal (Scan2), a first electrode connected to the second node (N2), and a second electrode connected to the third node (N3). there is. Accordingly, the second switching TFT (T2) responds to the second scan signal (Scan2) at the turn-on level, and connects the third node (N3) to which the second electrode of the capacitor (Cst) and the drain electrode of the driving TFT (DT) are connected. Connect.

The third switching TFT (T3) is turned on together with the second switching TFT (T2) in response to the second scan signal (Scan2). During turn-on operation, the third switching TFT (T3) connects the fourth node (N4) to which the reference voltage (Vref) is connected and the fifth node (N5) to which the second light-emitting TFT (ET2) is connected. The third switching TFT (T3) may include a gate electrode connected to the input line of the second scan signal (Scan2), a first electrode connected to the fourth node (N4), and a second electrode connected to the fifth node (N5). there is.

The first light-emitting TFT (ET1) and the second light-emitting TFT (ET2) are used to control light emission of the OLED. The first light emitting TFT (ET1) and the second light emitting TFT (ET2) are simultaneously controlled on/off according to the light emitting signal (EM) simultaneously input to each gate electrode.

The first light-emitting TFT (ET1) is turned on by the light-emitting signal (EM) and may serve to transmit the reference voltage (Vref) to the first electrode of the capacitor (Cst). The first light emitting TFT (ET1) may include a gate electrode connected to the input line of the light emitting signal (EM), a first electrode connected to the first node (N1), and a second electrode connected to the fourth node (N4).

The second light emitting TFT (ET2) is turned on by the light emitting signal (EM) to connect the third node (N3) and the fifth node (N5). The second light emitting TFT (ET2) may include a gate electrode connected to the input line of the light emitting signal (EM), a first electrode connected to the third node (N3), and a second electrode connected to the fifth node (N5).

The capacitor (Cst) stores the data voltage (Vdata). One electrode of the storage capacitor Cst is connected to the first node N1, and the other electrode is connected to the second node N2.

The operation of the subpixel SP including the above configuration will be described with reference to FIGS. 5 to 7. FIG. 5 is a diagram showing the current flow during the emission period of the subpixel, FIG. 6 is a diagram showing the current flow during the subpixel initialization period, and FIG. 7 is a diagram showing the current flow that may occur during the subpixel initialization period. It is a drawing.

Referring to FIG. 5, during the emission period of the subpixel, the data voltage (Vdata) is sampled at the capacitor (Cst), the potential at both ends of the capacitor (Cst) is changed using the reference voltage (Vref), and coupling ( The amount of current applied to the OLED can be controlled using the driving TFT (DT) by reflecting the data voltage (Vdata) in the gate voltage of the driving TFT (DT) using the coupling phenomenon.

When the reference voltage (Vref) is applied to the first node (N1) to which the first electrode of the capacitor (Cst) is connected while the data voltage (Vdata) is charged in the capacitor (Cst), the first electrode of the capacitor (Cst) The voltage changes to Vref. Accordingly, the second electrode of the capacitor Cst is also coupled to the voltage of the first electrode, and the Vref voltage is reflected in the second node N2 to which the second electrode of the capacitor Cst is connected. The second node (N2) to which the second electrode of the capacitor (Cst) is connected is a node to which the gate electrode of the driving TFT (DT) is connected. Before coupling of the capacitor (Cst), it is maintained at EVDD-Vth, and the first node (N1) is connected to the second electrode of the capacitor (Cst). ) is reflected and changed to EVDD-Vth-(Vdata-Vref) voltage. Accordingly, the driving TFT (DT) can control the amount of current applied to the OLED according to the Vdata-Vref voltage.

Referring to FIG. 6, during the initialization period of the subpixel, the potential at both ends of the capacitor (Cst) storing the data voltage (Vdata) is initialized to the reference voltage (Vref). To this end, the first light-emitting TFT (ET1), the second light-emitting TFT (ET2), the second TFT (T2), and the third TFT (T3) are maintained in a turned-on state. The reference voltage Vref may be applied to the first node N1 to which the first electrode of the capacitor Cst is connected through the first light-emitting TFT ET1. The second node (N2), to which the second electrode of the capacitor (Cst) is connected, has a reference voltage ( Vref) may be approved. The third TFT (T3) connects the fourth node (N4) and the fifth node (N5) to which the reference voltage (Vref) is connected, and the second light-emitting TFT (ET2) connects the fifth node (N5) and the third node ( N3), and the second TFT (T2) connects the third node (N3) and the second node (N2), so that the reference voltage (Vref) can be applied to the second node (N2).

However, since the gate electrode of the driving TFT (DT) is also connected to the second node (N2), the gate electrode and the source electrode of the driving TFT (DT) are connected while applying the reference voltage (Vref) to the second node (N2). A potential difference (Vgs) may occur between the two and the driving TFT (DT) may be turned on.

FIG. 7 shows a state in which a short path is formed between the high potential voltage (EVDD) and the reference voltage (Vref) by the driving TFT (DT) during the subpixel initialization period. As a short path is formed between the high potential voltage (EVDD) and the reference voltage (Vref), the voltage of the high potential voltage (EVDD) may change by △EVDD, and the reference voltage (Vref) may also change by △Vref. As the change in screen luminance increases, the high potential voltage (EVDD) decreases and the reference voltage (Vref) moves toward increasing.

When the high potential voltage (EVDD) and reference voltage (Vref) change, a difference occurs in the potential between the gate node and source node of the driving TFT (DT) in the emission section and the sampling section, which causes V _GS and driving It may affect the driving current of the TFT (DT), causing flashing or flicker on the screen.

After the high potential voltage (EVDD) changes, in the section where the high potential voltage (EVDD) is maintained, the amount of change in the reference voltage (Vref) affects V _GS and the driving current of the driving TFT (DT), causing the screen to darken. It can cause a phenomenon, namely Dim.

This can be expressed in a formula as follows:

< V _GS of driving TFT when ELVDD and Vref do not change >

< V _GS of driving TFT when ELVDD and Vref are fluctuating >

< V _GS of driving TFT when maintained after ELVDD change >

Figures 8 to 10 show the results of an image quality experiment when the luminance of some areas of the entire screen changes to black and white and the luminance of other areas does not change.

Figure 8 shows the change in image quality according to the luminance change in the luminance change area, when the luminance of some areas of the entire screen changes to black and white and the luminance of other areas does not change, the classic image quality is shown in Figure 8. These are the results of an experiment measuring changes in the above voltage (EVDD) and reference voltage (Vref) and changes in screen luminance.

Referring to the experimental results of FIG. 8, it can be seen that when the luminance change area is alternately displayed as black and white, the high potential voltage (EVDD) and reference voltage (Vref) also change according to the luminance change. . When displaying a black image, the high potential voltage (EVDD) increases and the reference voltage (Vref) decreases. When displaying a white image, the high potential voltage (EVDD) falls and the reference voltage (Vref) rises.

In this way, as the high potential voltage (EVDD) and the reference voltage (Vref) change, flicker occurs in the still area, which is an area where the luminance does not change, and dims occur in the section that maintains the displayed image. You can check it. These flicker and dim phenomena may become more severe as the luminance change value of the luminance change area increases.

9 shows the distance (horizontal axis) from the first power supply unit 180a that generates the high potential voltage (EVDD) and the reference voltage (Vref), and the source PCB (S) that applies the reference voltage (Vref) to a plurality of power lines. This is the result of an experiment measuring flicker according to the distance (vertical axis) from the PCB.

Referring to FIG. 9, for the experiment, the screen area is divided into two areas and a pattern in which black and white flash alternately is displayed in the area where the distance from the first power supply unit 180a is relatively long. , an area that is relatively close to the first power supply unit 180a displays a white image as a still area. Afterwards, when the flicker occurring on the screen is measured, it can be seen that the flicker in the still area increases as the distance from the first power supply unit 180a increases. Additionally, it can be seen that flicker increases as the vertical distance from the source PCB (S-PCB) that applies the reference voltage (Vref) to the power line increases.

That is, it can be seen that the image quality of the still area deteriorates as the distance to the first power supply unit 180a and the vertical distance to the source PCB (S-PCB) increase.

Figure 10 shows the results of an experiment measuring the flicker of a still area according to the distance of the luminance change area.

Referring to Figure 10, for the experiment, a black and white sparkling pattern is displayed in the central area of the screen, and a gray image is displayed in the still area.

Afterwards, when the flicker occurring on the screen is measured, the flicker in the P1 area, which is the closest distance to the first power supply unit 180a, is measured as the smallest value of 1.17.

The P2 area has the same vertical distance to the source PCB (S-PCB) as the P1 area, but the distance to the first power supply unit 180a is greater, and the flicker was measured to have increased by about 0.04 compared to the P1 area.

The P3 area and P4 area are areas where both the distance to the first power supply unit 180a and the distance to the source PCB (S-PCB) are increased compared to the P1 area, and the flicker is measured to have increased by about 0.5 compared to the P1 area. Here, the P4 area has the same vertical distance between the P3 area and the source PCB (S-PCB), but the distance from the first power supply unit 180a is further away, and thus, it is measured to be about 0.03 more than the P3 area.

The P5 area is an area where the distance to the first power supply unit 180a and the vertical distance to the source PCB (S-PCB) are closer than the P4 area, but the distance to the sparkling pattern is shorter. The flicker of this P5 area is 2.1, which is measured to be about 0.5 more flicker than the P4 area. Therefore, it can be seen that the degree of flicker on the screen is more affected by the distance to the sparkling pattern than the distance between the first power supply unit 180a and the source PCB (S-PCB).

As described above, through the experimental results of FIG. 8, it can be seen that as the amount of luminance change in the luminance change area increases, the fluctuation range of the high potential voltage (EVDD) and the reference voltage (Vref) increases, causing flicker and dimming to become more severe. Through the experimental results of FIG. 9, it can be seen that the flicker becomes more severe as the distance between the first power supply unit 180a and the source PCB (S-PCB) increases. Through the experimental results of FIG. 10, the closer the distance to the luminance change area, the more severe the flicker, and the distance to the luminance change area deteriorates image quality more than the distance to the first power supply unit 180a and the source PCB (S-PCB). You can see that it has a big impact.

Accordingly, in order to improve the image quality deterioration of the still area that occurs when the brightness of the brightness change area changes, the embodiment of the present specification compensates for the reference voltage (Vref) to eliminate the dim phenomenon and adjusts the distance between the brightness change area and the unchanged area. The flicker phenomenon is reduced by compensating the data voltage (Vdata) according to the distance between the first power supply unit 180a and the source PCB (S-PCB).

Figure 11 is a block diagram schematically showing a display device according to an embodiment of the present specification. The display device according to an embodiment of the present specification divides one frame of image data displayed on the screen into a plurality of blocks, calculates the luminance difference between the previous frame and the current frame for each block, and determines whether to compensate the image. The reference voltage (Vref) and image data for each block can be compensated.

Referring to FIG. 11 , a display device according to an embodiment of the present specification includes a frame buffer 200, a calculation unit 210, a detection unit 220, and a compensation unit 230.

The frame buffer 200 stores video data input in frame units and provides previous frame data (Frame(n-1)) to the calculation unit 210.

The calculation unit 210 receives DBV (Display Brightness Value), which is a brightness adjustment value of the display, and current frame data (Frame(n)), and inputs previous frame data (Frame(n-1)) from the frame buffer 200. Receive. The calculation unit 210 divides the current frame data Frame(n) and the current frame data Frame(n) into a plurality of blocks and calculates the luminance change amount ΔLum for each block. The calculation unit 210 outputs the luminance change amount (ΔLum) for each calculated block to the detection unit 220. This calculation unit 210 may include a gamma-luminance converter 215 that calculates luminance according to the gamma value of image data. The video luminance converter 215 can convert the gamma value (Gray) of each block into luminance information (nit) according to the gamma characteristics of the display panel 150 that displays the image. The calculation method of the calculation unit 210 will be described in more detail later.

The detection unit 220 determines whether to perform compensation when displaying the current frame data (Frame(n)) based on the luminance change amount (△Lum) for each block calculated by the calculation unit 210. For example, the detector 220 may sum up the luminance change amount for each block (Σ△Lum) and determine that compensation should be performed if the sum value (Σ△Lum) is greater than or equal to the reference luminance change amount (△Lum_Threshold). . If it is determined that compensation must be performed, the detector 220 may provide the compensation unit 230 with luminance change block information along with a compensation flag and a sum of the luminance changes (Σ△Lum). The luminance change block information may include location information of a block whose luminance changes and information on the amount of luminance change (△Lum) of the block. Here, the detector 220 may include a block information detector 225 that acquires luminance change block information. The block information detector 225 can detect the location information of a block with a luminance change amount (△Lum), that is, a luminance change block, among all blocks.

When the compensation flag is received from the detection unit 220, the compensation unit 230 sets a reference voltage compensation value (△Vref Value) and compensation data for each block based on the sum of the luminance changes (Σ△Lum) and the luminance change block information. △Data) is generated and output. The reference voltage compensation value (△Vref Value) output from the compensation unit 230 is transmitted to the first power supply unit 180a and is reflected in the reference voltage (Vref) when displaying the current frame (Frame(n)). Compensation data (△Data) for each block may be reflected in the data voltage (Vdata) of blocks where flicker occurs due to the influence of the luminance change block. In this way, when the reference voltage (Vref) is compensated, the EVDD voltage fluctuation that appears when the luminance changes suddenly is V _GS of the driving TFT (DT). You can reduce screen flashing by preventing it from affecting the screen. Compensation data (△Data) applied for each block can reduce the dim phenomenon that appears differently in each screen area depending on changes in EVDD and reference voltage (Vref).

The compensator 230 may generate a reference voltage compensation value (ΔVref Value) according to the sum of the received luminance changes (ΣΔLum). The compensation unit 230 may include a Vref compensation LUT in which a reference voltage compensation value (ΔVref Value) according to the sum of luminance changes (ΣΔLum) is stored. Accordingly, the compensation unit 230 may obtain a reference voltage compensation value (△Vref Value) corresponding to the sum of the received luminance changes (Σ△Lum) from the Vref compensation LUT and provide it to the first power supply unit 180a. there is.

The compensation unit 230 may generate compensation data (ΔData) for blocks in which flicker occurs due to the influence of the luminance change block, based on the received luminance change block information. Compensation data (△Data) is based on the distance (△Distance) between the block to be compensated and the luminance change block, the distance (△Position_X, △Position_Y) from the first power supply unit 180a and the source PCB (S-PCB), etc. It can be calculated as follows.

The compensation unit 230 includes a distance compensation LUT in which a data voltage (Vdata) compensation value according to the distance (△Distance) to the luminance change block is stored in order to generate compensation data (△Data) for each block, and a first power supply unit (180a). Position_X compensation LUT, which stores the data voltage (Vdata) compensation value according to the horizontal distance (△Position_X) from the source PCB (S-PCB). May contain stored Position_Y compensation LUT. Accordingly, based on the received luminance change block information, the compensation unit 230 determines the distance (△Distance) from the luminance change block, the distance (△Position_X) from the first power supply unit 180a and the source PCB (S-PCB). , △Position_Y), compensation values can be obtained from the Distance compensation LUT, Position_X compensation LUT, and Position_Y compensation LUT respectively, and the obtained compensation values can be calculated to generate compensation data (△Data) for each block.

Here, the first power supply unit 180a is provided on one side of the source PCB (S-PCB) to generate driving power, and the driving power generated by the first power supply unit 180a is transmitted through the source PCB (S-PCB). Subpixels (SP) are applied to a plurality of connected power input lines.

Therefore, the distance from the first power supply unit 180a may be located on the rightmost or leftmost side of the bottom, so the compensation value can be set considering only the horizontal distance (△Position_X). there is.

Since the source PCB (S-PCB) inputs driving power to a plurality of power input lines connected to the subpixels (SP), the distance from the source PCB (S-PCB) is a compensation value considering only the vertical distance (△Position_Y) This can be set.

As described above, the compensation unit 230 determines the reference voltage compensation value (△Vref Value) corresponding to the sum of the received luminance changes (Σ△Lum), the distance (△Distance) between the luminance change blocks, and the first power supply unit. Compensation data (△Data) for each block calculated according to the horizontal distance (△Position_X) from (180a) and the vertical distance (△Position_Y) from the source PCB (S-PCB) can be generated.

In the above description, the case of compensating the data voltage (Vdata) on a block basis is exemplified, but after compensation performance is determined, if compensation block information (△Distance, △Position_X, △Position_Y) is generated on a pixel basis, the data is calculated on a per-pixel basis. It is also possible to compensate for voltage.

FIGS. 12 and 13 are diagrams for explaining the control method of the calculation unit 210 of FIG. 11. The calculation unit 210 receives the DBV, current frame data (Frame(n)), and previous frame data (Frame(n-1)), calculates the luminance change amount (△Lum) for each block, and calculates the luminance change amount (△Lum) for each block. The luminance change amount (△Lum) is output to the detection unit 220.

Referring to FIG. 12, frame data displayed in the display area (AA) can be divided into a plurality of blocks. In the embodiment of Figure 12, frame data is divided into M rows and N columns, and each block is displayed by dividing it into row and column numbers.

Blocks B25 and B26 represent luminance change blocks whose gray values change between 255 Gray and 0 Gray, and may be blocks whose luminance changes between black and white.

The B35 block and B36 block represent luminance change blocks whose gray values change between 255 Gray and 127 Gray, and may be blocks whose luminance changes between black and gray.

The B52 block and B53 block represent luminance change blocks whose gray values change between 255 Gray and 127 Gray, and may be blocks whose luminance changes between black and gray.

The B62 block and B63 block represent luminance change blocks whose gray values change between 255 Gray and 0 Gray, and may be blocks whose luminance changes between black and white.

Current frame data (Frame(n)) and previous frame data (Frame(n-1)) may include gray values for each block.

The calculation unit 210 obtains the luminance for each block using the gamma-luminance converter 215, and then obtains the luminance for each block of the current frame data (Frame(n)) and the previous frame data (Frame(n-1)). The luminance change amount (△Lum) can be calculated.

The gamma-luminance converter 215 obtains the luminance for each gray by referring to the gamma setting value of the corresponding display device according to the input DBV.

Figure 13 is a graph illustrating the luminance setting value for each gray according to DBV.

Referring to FIG. 13, when the DBV is 2047 (DBV=2047), the luminance of 255 Gray (white) can be set to 400 nit. If the DBV is 1617 (DBV=1617), the luminance of 255 Gray (white) can be set to 350 nit. The luminance setting value for each gray according to DBV can be set in advance according to the characteristics of the display device.

Accordingly, the gamma-luminance converter 215 refers to the luminance setting value for each gray of the corresponding display device according to the input DBV and converts the current frame data (Frame(n)) and the previous frame data (Frame(n-1)). The luminance of each block can be obtained. Here, when a DBV that has not been stored in advance is input, the gamma-luminance converter 215 can obtain luminance for each block by interpolating the settings of DBV values close to the input DBV.

For example, when the DBV value is 1832, the gamma-luminance converter 215 converts the gamma-luminance setting value when the DBV is 2047 (DBV=2047) and the gamma-luminance setting value when the DBV is 1617 (DBV=1617). Based on the luminance setting value, the gamma-luminance setting value when the DBV value is 1832 can be calculated. Therefore, if the DBV value is 1832, 0Gray can be calculated as 0nit, 127Gray can be calculated as 60nit, and 255Gray can be calculated as 375nit.

As described above, after obtaining the luminance for each block using the gamma-luminance converter 215, the calculation unit 210 calculates the current frame data (Frame(n)) and the previous frame data (Frame(n-1)). The luminance change amount (△Lum) for each block can be calculated.

For example, in the case of a block whose gray value changes between 255Gray and 0Gray, such as block B25 in FIG. 12, the luminance of the previous frame can be obtained as 375nit, which is the luminance set at 255Gray. The luminance of the current frame can be obtained as 0nit, which is the luminance set to 0Gray. Accordingly, the luminance change amount (ΔLum) of the B25 block can be calculated as 375. To summarize this briefly, it is as follows.

Calculating the luminance change (△Lum) of the B35 block in the same way is as follows.

The luminance change amount (△Lum) of the remaining blocks B26, B36, B52, B53, B62, and B63 can be calculated as follows.

The calculation unit 210 calculates the luminance change amount (ΔLum) for each block according to the above process and outputs it to the detection unit 220.

Afterwards, the detection unit 220 determines whether to perform compensation based on the luminance change amount (△Lum) for each block, and when compensation is determined, the detection unit 220 sends a compensation flag to the compensation unit 230. ) along with the luminance change amount (△Lum) and compensation block information can be provided to the compensation unit 230. The detector 220 may sum up the luminance change amount (△Lum) for each block, and determine that compensation should be performed if the sum of the luminance change amounts (Σ△Lum) is greater than or equal to the reference luminance change amount (△Lum_Threshold).

For example, in the case of the frame data of FIG. 12, the sum of the luminance changes (△Lum) of blocks B25, B26, B35, B36, B52, B53, B62, and B63 is 2760. It is calculated as Here, when the reference luminance change amount (△Lum_Threshold) is set to 2500, it can be determined that the frame data of FIG. 12 requires compensation. When it is determined that compensation must be performed, the detection unit 220 provides the compensation flag (Flag), the sum of the luminance changes (ΣΔLum), and the luminance change block information to the compensation unit 230. Here, the luminance change block information may include location information of blocks B25, B26, B35, B36, B52, B53, B62, and B63 and the amount of luminance change (△Lum) of each block.

FIGS. 14 and 15 are diagrams for explaining a control method of the compensator 230 of FIG. 11 . FIG. 14 is a diagram illustrating the configuration of the LUT stored in the compensation unit 230, and FIG. 15 is a diagram illustrating a method of generating compensation data of the B32 block.

The compensator 230 may generate a reference voltage compensation value (△Vref Value) according to the sum of the luminance changes (Σ△Lum). The reference voltage compensation value (ΔVref Value) according to the sum of the luminance changes (ΣΔLum) can be obtained from the Vref compensation LUT.

The compensation unit 230 calculates the sum of the luminance changes (Σ△Lum), the horizontal distance (△Position_X) from the first power supply unit 180a, and the vertical distance (△Position_Y) from the source PCB (S-PCB). , compensation data (△Data) for each block can be generated by obtaining compensation values according to the amount of luminance change (△Lum) and the distance (△Distance) between the compensation target block and the luminance change block. These compensation values can be obtained from a pre-stored LUT.

Referring to FIG. 14, the compensation unit 230 may include LUT1 to LUT4.

LUT1 is a Vref compensation LUT in which the Vref compensation gain according to the sum of luminance changes (Σ△Lum) is stored. The α value may be a Vref compensation gain according to the sum of the luminance changes (Σ△Lum).

LUT2 is a Position_X compensation LUT that stores a compensation value according to the sum of luminance changes (Σ△Lum) and the horizontal distance (△Position_X) from the first power supply unit 180a. The horizontal distance (△Position_X) can be measured by the number of blocks. The β value may be a data compensation gain according to the sum of the luminance changes (Σ△Lum) and the horizontal distance (△Position_X) from the first power supply unit 180a.

LUT3 is a Position_Y compensation LUT that stores compensation values according to the sum of luminance changes (Σ△Lum) and the vertical distance (△Position_Y) from the source PCB (S-PCB). The vertical distance (△Position_Y) can be measured by the number of blocks. The γ value may be a data compensation gain according to the sum of the luminance changes (ΣΔLum) and the vertical distance (ΔPosition_Y) from the source PCB (S-PCB).

LUT4 is a distance compensation LUT that stores compensation values according to the luminance change amount (△Lum) of the luminance change block and the distance (△Distance) from the luminance change block. The distance (△Distance) between the compensation target block and the luminance change block can be measured as the X-axis distance (△x) and the Y-axis distance (△y). The δ value may be a data compensation gain according to the luminance change amount (△Lum) and the X-axis direction distance (△x) of the luminance change block. The ε value may be a data compensation gain according to the luminance change amount (△Lum) and the Y-axis direction distance (△y) of the luminance change block.

Figure 15 is a diagram for explaining a method of generating compensation data for the B32 block.

The compensation data (△Data) of the B32 block is the sum of the luminance changes (Σ△Lum), the horizontal distance (△Position_X) from the first power supply unit 180a, and the vertical direction from the source PCB (S-PCB). It can be determined according to the distance (△Position_Y), the luminance change amount (△Lum) of the B32 block, and the distance (△Distance) from the luminance change blocks (B25, B26, B35, B36, B52, B53, B62, B63). Distances used when calculating compensation data (△Data) can be measured using the number of blocks.

The horizontal distance (△Position_X) between the B32 block and the first power supply unit (180a) can be measured as 5, which is the number of blocks in the X-axis direction between the B32 block and the first power supply unit (180a) (△Position_X=5). Accordingly, a compensation value of △Position_X=5 according to the sum of the luminance changes (Σ△Lum) can be obtained from the Position_X compensation LUT (LUT2).

The vertical distance (△Position_Y) between the B32 block and the source PCB (S-PCB) can be measured as 7, which is the number of blocks in the Y-axis direction between the B32 block and the source PCB (S-PCB) (△Position_Y=7) . Accordingly, a compensation value of △Position_Y=7 according to the sum of luminance changes (Σ△Lum) can be obtained from the Position_Y compensation LUT (LUT3).

The distance (△Distance) between the B32 block and the luminance change blocks (B25, B26, B35, B36, B52, B53, B62, B63) is measured by the number of blocks in the X-axis direction and the number of blocks in the Y-axis direction between the two blocks. It can be. For example, the X-axis distance between the B32 block and the B25 block can be measured as △x=3, and the Y-axis distance can be measured as △y=1. The distance in the X-axis direction between the B32 block and the B53 block can be measured as △x=1, and the distance in the Y-axis direction can be measured as △y=2. By measuring the distance to other luminance change blocks in the same way, the distance in the X-axis direction (△x) and the distance in the Y-axis direction (△y) can be measured for a total of 8 luminance change blocks, respectively. Accordingly, the compensation value of △x and △y according to the luminance change amount (△Lum) of the luminance change block can be obtained from the distance compensation LUT (LUT4).

The compensation unit 230 has a horizontal distance (△Position_X) from the first power supply unit 180a, a vertical distance (△Position_Y) from the source PCB (S-PCB), and a distance (△Distance) from the luminance change block. Compensation data (△Data) of the B32 block can be calculated by calculating the compensation values obtained according to .

For example, the compensation unit 230 may calculate the reference voltage compensation value (△Vref Value) and the compensation data (△Data32) of the B32 block in the following manner.

The compensator 230 may obtain the Vref compensation gain (α) from the Vref compensation LUT (LUT1) according to the sum of the luminance changes (Σ△Lum). Accordingly, the reference voltage compensation value (△Vref) can be calculated by multiplying the sum of the luminance changes (Σ△Lum) by the ref compensation gain (α) (△Vref = α*Σ△Lum).

The compensation unit 230 calculates a compensation gain (β) from the Position_ It can be obtained. Accordingly, the compensation value (△Data32 _{Position_X} ) of the B32 block according to the horizontal distance (△Position_X) can be calculated by multiplying the sum of luminance changes (Σ△Lum) by the compensation gain (β) (△Data32 _{Position _X} = β*Σ△Lum).

The compensation unit 230 calculates a compensation gain (γ) from the Position_Y compensation LUT (LUT3) according to the sum of the luminance changes (Σ△Lum) and the vertical distance (△Position_Y) between the B32 block and the source PCB (S-PCB). It can be obtained. Accordingly, the compensation value (△Data32 _{Position_Y} ) of the B32 block according to the vertical distance (△Position_Y) can be calculated by multiplying the sum of the luminance changes (Σ△Lum) by the compensation gain (γ) (△Data32 _{Position _Y} = γ*Σ△Lum).

The compensation value according to the distance (△Distance) between the B25 block, which is the luminance change block, and the B32 block, which is the compensation target block, can be obtained using the Distance Compensation LUT (LUT4). Data compensation gain (δ) according to the there is. Data compensation gain (ε) according to the Y-axis direction distance (△y) between the B25 block and B32 block can be obtained according to the luminance change amount (△Lum25) of the B25 block and the Y-axis direction distance (△y) from the B32 block. there is. Accordingly, the compensation value (△Data32 _{Block_25} ) according to the distance (△Distance) between the B25 block and the B32 block is the luminance change of the B25 block (△Lum25) plus the compensation gain (δ) of the distance in the X-axis direction (△x) and the Y-axis. It can be calculated by multiplying the sum of the compensation gain (γ) by the direction distance (△y) (△Data32 _{Block_25} = △Lum25(δ+ε)). In the same way, compensation values (△Data32 _{Block_26,} △Data32 _{Block _35,} △Data32 _{Block _36,} △Data32 _{Block _52,} △Data32 _{Block _53,} △Data32 _{Block_62,} △Data32 _{Block _ 63} ) can be calculated. Accordingly, the data compensation value for the distance (△Distance) between blocks of B32, the compensation target block, is 8 luminance change compensation values (△Data32 _{Block_25,} △Data32 _{Block _26,} △Data32 _{Block _35,} △Data32 _{Block _36,} △Data32 It can be calculated by adding up _{Block _52,} △Data32 _{Block_53,} △Data32 _{Block _62,} △Data32 _{Block _ 63} ).

Finally, the compensation data (△Data32) of the B32 block is the horizontal distance (△Position_X) between the first power supply units 180a, the vertical distance (△Position_Y) between the source PCBs (S-PCB), and the luminance change blocks It can be calculated by adding up all compensation values obtained according to the distance (△Distance). This can be expressed in a formula as follows:

Figures 16 and 17 show test results of screen display results according to comparative examples and embodiments.

Figure 16 is a diagram showing the results of measuring the luminance change of a still image when compensation conditions are different.

(a) shows the change in EVDD and Vref according to the change in screen luminance and the luminance measurement result of a still image when compensation is not performed. If compensation is not performed, you can see that flashing and dimming occur in still images.

(b) shows the change in EVDD and Vref according to the change in screen luminance and the luminance measurement result of the still image when only Vref is compensated. When only Vref is compensated, the flashing phenomenon is removed in still images, but the dimming phenomenon occurs.

(c) shows the change in EVDD and Vref according to the change in screen luminance and the luminance measurement result of a still image when both Vref and data for each block are compensated. When both Vref and block-specific data are compensated, it can be seen that the still image maintains a constant luminance without flashing or dimming.

Figure 17 shows the results of testing the screen display status when compensation was not performed and when compensation was performed.

(a) illustrates a case where when the luminance change area changes to black and white against a white screen, all areas display a white screen.

(b) shows the screen when the luminance change area changes from white to black with a white screen as the background without compensation. It can be seen that the luminance of the still image area changes as the luminance of the luminance change area changes rapidly. In particular, it can be seen that the luminance change in the area adjacent to the luminance change area is more severe, and that the longer the distance from the first power supply unit 180a and the source PCB (S-PCB), the more severe the luminance change.

(c) shows the screen when the luminance change area changes from white to black against a white screen when both Vref and data for each block are compensated. If both Vref and data for each block are compensated, it can be confirmed that the luminance of the still image area remains constant even if the luminance of the luminance change area changes suddenly.

Although the embodiments of the present specification have been described in more detail with reference to the accompanying drawings, the present specification is not necessarily limited to these embodiments, and various modifications may be made without departing from the technical spirit of the present specification. . Accordingly, the embodiments disclosed in this specification are not intended to limit the technical idea of the present specification, but rather to explain it, and the scope of the technical idea of the present specification is not limited by these embodiments. Therefore, the embodiments described above should be understood in all respects as illustrative and not restrictive. The scope of protection of this specification should be interpreted in accordance with the claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this specification.

110: video supply unit 120: timing controller
130: gate driver 140: data driver
150: display panel 180, 180a: power supply unit
200: frame buffer 210: calculation unit
215: Gamma-luminance converter 220: Detection unit
225: block information detector 230: compensation unit

Claims (14)

A display panel including subpixels that are each connected to a plurality of power input lines and receive driving power including a reference voltage to display image data;
a calculation unit that calculates a luminance change amount for each block by comparing the luminance difference between the image data of the current frame and the image data of the previous frame on a block basis;
Based on the luminance change amount for each block, it is determined whether to perform compensation for the first blocks, which are blocks whose luminance does not change, and when compensation is decided, the location information of the second blocks, which are luminance change blocks, and the luminance change amount of the corresponding block are included. a detection unit that detects second block information; and
Generates a reference voltage compensation value for the reference voltage compensation according to the amount of change in luminance for each block, and generates a data voltage of the first blocks according to the distance between the first blocks and the second blocks and the amount of change in luminance of the second blocks. a compensation unit that generates first compensation values to compensate for each;
A display device including a. According to paragraph 1,
The detection unit,
A display device that determines to perform compensation for the first blocks when the total amount of luminance change for each block is greater than or equal to a reference luminance change. According to paragraph 1,
a power supply unit located on one side of the display panel to apply the driving power; and
a source-PCB that transmits the driving power output from the power supply unit to the plurality of power input lines;
A display device further comprising: According to paragraph 3,
The compensation department,
A display device that generates a second compensation value to compensate for the data voltage of the first block according to the input position of the power supply unit and the distance between the first block and the first block. According to paragraph 3,
The compensation department,
A display device that generates a third compensation value to compensate for the data voltage of the first block according to the distance between the source-PCB and the first block. According to paragraph 3,
The compensation department,
Generate a second compensation value according to the distance in the X-axis direction between the power supply unit and the first block,
A display device that generates a third compensation value according to the Y-axis direction distance between the source-PCB and the first block. According to paragraph 3,
The compensation department,
A display device that inputs the reference voltage compensation value into the power supply unit to compensate for the reference voltage output from the power supply unit. According to paragraph 1,
The compensation department,
A display device that generates the first compensation value by adding a compensation value according to the horizontal distance and a compensation value according to the vertical distance of the first block and the second block. According to paragraph 1,
The compensation department,
The first compensation value, the second compensation value generated according to the position of the power supply that applies the driving power and the distance between the first block, and the driving power output from the power supply to the plurality of power input lines. A display device that compensates for the data voltage of the first block by adding a third compensation value generated according to the input position of the transmitting source-PCB and the distance between the first block. According to clause 9,
The compensation department,
a first LUT storing a reference voltage compensation value corresponding to the sum of the luminance changes for each block;
a second LUT storing the first compensation value corresponding to the amount of change in luminance of the second block and the distance between the first block and the second block;
a third LUT storing the sum of the luminance changes for each block and the second compensation value corresponding to the distance between the input position of the driving power and the first block; and
a fourth LUT storing the sum of the luminance changes for each block and the third compensation value corresponding to the distance between the input position of the data voltage and the first block;
A display device including a. According to paragraph 1,
The compensation department,
a first LUT storing a reference voltage compensation value corresponding to the sum of the luminance changes for each block; and
a second LUT storing the first compensation value corresponding to the amount of change in luminance of the second block and the distance between the first block and the second block;
A display device including a. A plurality of power input lines for applying driving power including a reference voltage and a plurality of data lines for applying a data voltage are arranged, and a plurality of subpixels are connected to the power input line and the data line to display image data. In a method of driving a display device including a display panel,
Comparing the luminance difference between the image data of the current frame and the image data of the previous frame for each block;
determining compensation for first blocks, which are blocks whose luminance does not change, when the total amount of luminance change for each block is greater than or equal to a reference luminance change;
When compensation performance is determined, detecting location information of second blocks that are luminance change blocks and the amount of luminance change of the corresponding blocks;
generating a reference voltage compensation value for the reference voltage compensation according to the total amount of luminance change for each block; and
generating first compensation values for compensating the data voltages of the first blocks according to the distance between the first blocks and the second blocks and the amount of change in luminance of the second blocks;
A method of driving a display device including. According to clause 12,
generating a second compensation value to compensate for the data voltage of the first block according to the location of the power supply unit that applies the driving power and the distance between the first block; and
A third compensation value is generated to compensate for the data voltage of the first block according to the distance between the input position of the source-PCB and the first block, which transmits the driving power output from the power supply to the plurality of power input lines. steps;
A method of driving a display device further comprising: According to clause 13,
A method of driving a display device further comprising compensating the data voltage of the first block by adding the first compensation value, the second compensation value, and the third compensation value.

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