KR102417424B1 - Tiled display and luminance compensation method thereof - Google Patents

Abstract

The present invention relates to a tiled display and a luminance compensation method thereof, and a first degradation measurement representative of a degradation level of the first display panel based on a result of sensing electrical characteristics of each pixel disposed on the first display panel A second degradation measurement value representing the degradation level of the second display panel is calculated based on the value and the sensing result of the electrical characteristics of each of the pixels disposed on the second display panel, and the first and second degradation selecting a larger degradation measurement value among the measurement values; A target luminance defining the maximum luminance of the first and second display panels is selected according to the selected deterioration measurement value. Pixel data to be written in each of the pixels of the first display panel is modulated with a first compensation value limited by the target luminance. Pixel data to be written in each of the pixels of the second display panel is modulated with a second compensation value limited by the target luminance. When the target luminance is lowered, the maximum values of the first and second compensation values are lowered.

Description

Tiled display and its luminance compensation method

The present invention relates to a tiled display for realizing a large screen using a plurality of display panels and a luminance compensation method thereof.

Digital signage reproduces visual information on a large screen in a commercial space. Digital signage is a large-screen display known as multi-vision or video wall using a tiled display.

A tiled display includes a plurality of display panels bonded to a large screen. In order to increase the image quality of digital signage, the bezel of the display panels should be minimized so that the boundary between the display panels is minimized, and there should be no difference in image quality between the display panels. Since digital signage can be installed outdoors, it requires the reliability of a display panel suitable for harsh external environments and requires high luminance to provide a clear screen even in sunlight.

Even if the display panels constituting the tiled display have the same luminance characteristics at the time of shipment, a difference may occur in the degree of deterioration between the display panels due to a difference in an input image between the display panels and a difference in ambient temperature during driving. A difference in the degree of deterioration between the display panels causes a difference in luminance between the display panels. When any one of the display panels constituting the tiled display breaks down or has expired, the display panel may be replaced. In this case, a difference in luminance may occur between a display panel that has been greatly deteriorated and a new display panel that has been replaced.

Accordingly, the present invention provides a tiled display capable of automatically compensating for a luminance difference between display panels and a luminance compensation method thereof.

A tiled display of the present invention includes a first display panel driver for driving a first display panel; a first degradation compensator for compensating for pixel data to be written in each of the pixels of the first display panel based on a result of sensing an electrical characteristic of each of the pixels disposed on the first display panel; a second display panel driver for driving the second display panel; and a second degradation compensator for compensating for pixel data to be written in each of the pixels of the second display panel based on a result of sensing the electrical characteristics of each of the pixels disposed on the second display panel.
The first degradation compensator calculates a first degradation measurement value representing the degradation level of the first display panel, and transmits it to the second degradation compensator. The second degradation compensator calculates a second degradation measurement value representing the degradation level of the second display panel and transmits the calculated second degradation compensator to the first degradation compensator.
The first degradation compensator selects a first compensation value limited by a target luminance defining the maximum luminance of the first and second display panels, and applies the selected first compensation value to each of the pixels of the first display panel. The pixel data to be written is modulated, and the maximum value of the first compensation value is lowered when the target luminance is lowered.
The second degradation compensator selects a second compensation value limited by the target luminance, modulates pixel data to be written in each of the pixels of the second display panel with the selected second compensation value, and reduces the target luminance. When the maximum value of the second compensation value is lowered.

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The method of compensating for the luminance of the tiled display may include: calculating a first measurement value of deterioration representative of a deterioration level of the first display panel based on a result of sensing electrical characteristics of each of the pixels disposed on the first display panel; calculating a second degradation measurement value representing a degradation level of the second display panel based on a result of sensing electrical characteristics of each of the pixels disposed on the second display panel; selecting a larger degradation measurement value among the first and second degradation measurements; selecting a target luminance defining maximum luminance of the first and second display panels according to the selected deterioration measurement value; selecting a first compensation value limited by the target luminance and modulating pixel data to be written in each of the pixels of the first display panel with the selected first compensation value; selecting a second compensation value limited by the target luminance and modulating pixel data to be written in each of the pixels of the second display panel with the selected second compensation value; and lowering the maximum values of the first and second compensation values when the target luminance is lowered.

According to the present invention, the deterioration measurement value DM of the display panels is shared among the deterioration compensation units of each of the display panels driving the tiled display, and the maximum luminance of the display panels is limited based on the largest deterioration measurement value. As a result, the tiled display of the present invention can realize uniform image quality without a difference in luminance between display panels.

1 is a diagram schematically showing a tiled display screen according to an embodiment of the present invention.
2 is a view showing a rear surface of a tiled display.
3 is a block diagram illustrating a display panel and a display panel driver.
4 is a circuit diagram illustrating a deterioration compensator.
5A and 5B are circuit diagrams detailing an example of a pixel circuit and a deterioration compensator.
6 is a block diagram illustrating a compensation unit in detail.
7 is a diagram illustrating a compensation lookup table.
8 is a diagram illustrating a luminance lookup table.
9 is a diagram illustrating an example in which deterioration measurement values are shared between timing controllers.
10 is a diagram illustrating an example in which a target luminance is selected by comparing deterioration measurement values of display panels in an integrated control box of a tiled display.
11 is a diagram illustrating an example in which deterioration measurement values are compared in each of timing controllers mounted on control boards of a tiled display to select a target luminance.

Advantages and features of the present invention and methods of achieving them will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. The present invention is not limited to the embodiments disclosed below, but will be implemented in various different forms, and only the embodiments allow the disclosure of the present invention to be complete, and those of ordinary skill in the art to which the present invention pertains It is provided to fully understand the scope of the invention, and the present invention is only defined by the scope of the claims.

The shape, size, ratio, angle, number, etc. disclosed in the drawings for explaining the embodiment of the present invention are exemplary, and therefore the present invention is not limited to the matters shown in the drawings. Like reference numerals refer to substantially identical elements throughout. In addition, in describing the present invention, if it is determined that a detailed description of a related known technology may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

When "includes", "includes", "having", "consisting 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, it may be interpreted as the plural unless otherwise explicitly stated.

In interpreting the components, it is construed as including an error range even if there is no separate explicit description.

In the case of a description of the positional relationship, for example, when the positional relationship between two components is described as 'on One or more other elements may be interposed between those elements in which 'directly' or 'directly' are not used.

1st, 2nd, etc. may be used to distinguish the components, but the functions or structures of these components are not limited to the ordinal number or component name attached to the front of the component.

The following embodiments can be partially or wholly combined or combined with each other, and technically various interlocking and driving are possible. Each of the embodiments may be implemented independently of each other or may be implemented together in a related relationship.

The tiled display of the present invention senses or automatically adjusts the luminance of other display panels based on the luminance of the most deteriorated display panel based on a value measured or sensed about the deterioration of the display panel. The tiled display of the present invention may be implemented based on an organic light emitting diode display (OLED Display) capable of compensating for luminance by sensing deterioration of the display panel, but is not limited thereto.

An active matrix type organic light emitting diode display reproduces an input image using an organic light emitting diode (hereinafter, referred to as "OLED") that emits light on each sub-pixel by itself. It is fast and has a large luminous efficiency, luminance, and viewing angle. Since the organic light emitting diode display can express the black gradation as complete black, the image can be reproduced at a superior level in contrast ratio and color gamut.

A pixel circuit of an organic light emitting diode display includes transistors that drive an OLED, which is a light emitting device. The transistors may be implemented as TFTs having a metal oxide semiconductor field effect transistor (MOSFET) structure. The transistor may be implemented as a thin film transistor (TFT) having substantially the same structure as a transistor formed in the pixel array. The transistors may be implemented as one or more of a low temperature polysilicon (LTPS) TFT, oxide TFT, and a-Si TFT. A transistor is a three-electrode device including a gate, a source, and a drain. The source is an electrode that supplies a carrier to the transistor. In the transistor, carriers begin to flow from the source. The drain is an electrode through which carriers exit the transistor. In a transistor, the flow of carriers flows from source to drain. In the case of an n-channel transistor (NMOS), since carriers are electrons, the source voltage has a voltage lower than the drain voltage so that electrons can flow from the source to the drain. In an n-channel transistor (NMOS), the direction of current flows from the drain to the source. In the case of a p-channel transistor (PMOS), since carriers are holes, the source voltage is higher than the drain voltage so that holes can flow from the source to the drain. In a p-channel transistor (PMOS), 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 the transistor are not fixed. For example, the source and drain may be changed according to an applied voltage. Accordingly, 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 of the transistor swings between a gate on voltage and a gate off voltage. The gate-on voltage is set to a voltage at which the transistor is turned on, and the gate-off voltage is set to a voltage at which the transistor is turned off. In the case of an n-channel transistor (NMOS), the gate-on voltage may be a gate high voltage (VGH), and the gate-off voltage may be a gate low voltage (VGL) lower than the gate high voltage (VGH). have. In the case of the p-channel transistor PMOS, the gate-on voltage may be the gate low voltage VGL, and the gate-off voltage may be the gate high voltage VGH.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following embodiments, the electroluminescent display device of the present invention will be mainly described with respect to an example to which an external compensation circuit is applied.

1 and 2 , a tiled display according to an embodiment of the present invention includes a plurality of display panels PNL1 to PNL12. The display panels PNL1 to PNL12 implement a large screen.

The tiled display of the present invention includes an integrated control box (hereinafter referred to as “SET”, 200 ) and a plurality of control boards 204 .

The SET 200 includes a host system, an interface for connecting external peripheral devices to the host system, and a main power supply for generating main power. The host system converts the pixel data of the input image to a resolution of each of the display panels PNL1 to PNL12 and distributes the pixel data to the control boards 204 corresponding to the display panels PNL1 to PNL12 1:1. The host system integrally manages the control boards 204 of the display panels PNL1 to PNL12. As shown in FIG. 10 , the host system may select a target luminance by comparing deterioration measurement values received from timing controllers mounted on the control boards 204 .

The SET 200 is connected to the control boards 204 via cables. The SET 200 distributes the pixel data of the input image distributed by the host system to the control boards 204 . The SET 200 controls the synchronization of the control boards 204 so that the images reproduced on the display panels PNL1 to PNL12 are synchronized.

Each of the control boards 204 controls one display panel and a display panel driver driving the display panel. For example, the N-th control board (N is a natural number) is in charge of the N-th display panel PNL(N) and the N-th display panel driver driving the N-th display panel PNL(N). The N-th control board supplies the pixel data of the input image received from the SET 200 to the N-th display panel driver. The N-th display panel driver writes pixel data into the pixels of the N-th display panel PNL(N). The N-th display panel driver senses the electrical characteristics of each of the pixels of the N-th display panel PNL(N) to sense the deterioration of the pixels, and based on the sensing result, the deterioration of the N-th display panel PNL(N) Calculate the level. The deterioration measurement values calculated from the display panel drivers in this way are shared between the control boards 204 through a wired/wireless interface or transmitted to the SET 200 and shared through the SET 200 .

Each of the control boards 204 compares the measured deterioration value of the display panel in charge of the display panel with the deterioration measured value of the surrounding display panels, and based on the display panel having the largest deterioration measurement value (DM), a target luminance (target). luminance) and compensates the luminance of the pixel data based on the target luminance. The display panel having the largest deterioration measurement value is the display panel in which pixel deterioration is the most severe among the display panels, and the display panel has the lowest luminance when the same data voltage is applied. The target luminance indicates the maximum luminance of the display panel after deterioration. In order to improve the lifespan of the display panel, the target luminance is set to decrease as the deterioration of the display panel increases. The luminance of the display panels PNL1 to PNL12 is automatically adjusted according to the target luminance of the display panel with the greatest deterioration by the control boards 204 . Accordingly, even if there is a difference in deterioration level or crossing of the display panels PNL1 to PNL12 constituting the tiled display of the present invention, the luminance of all the display panels PNL1 to PNL12 is automatically equal.

In the tiled display according to an embodiment of the present invention, a first display panel driver driving a first display panel, and pixel data to be written in pixels of the first display panel based on a result of sensing deterioration of the first display panel pixel data to be written in the pixels of the second display panel based on the first deterioration compensator compensating for and a second deterioration compensator for compensating. The deterioration compensators may be installed in the display panel driver as shown in FIGS. 3 and 4 . The first degradation compensator calculates a first measurement value of deterioration representing the degradation level of the first display panel and transmits it to the second degradation compensator, and the second degradation compensator generates a second degradation value representing the degradation level of the second display panel The measured value is calculated and transmitted to the first degradation compensator. Accordingly, deterioration measurement values are shared among the deterioration compensators.

The first deterioration measurement value is an average value of sensing data obtained from all sub-pixels of the first display panel. The second deterioration measurement value is an average value of sensing data obtained from all sub-pixels of the second display panel. Each of the first and second degradation compensators defines the maximum luminance of the first and second display panels based on a larger degradation measurement value among the first and second degradation measurement values. As the deterioration measurement value selected by the first and second deterioration compensators increases, the target luminance decreases.

The first degradation compensator selects a compensation value limited by the target luminance, and modulates pixel data to be written in the pixels of the first display panel with the selected compensation value to compensate for the degradation of the pixels. Similarly, the second degradation compensator selects a compensation value limited by the target luminance and modulates pixel data to be written in the pixels of the second display panel with the selected compensation value to compensate for the degradation of the pixels. The compensation value may be a gain multiplied by pixel data. The larger the sensed data, the larger the compensation value. These features of the present invention will be described in detail in the following examples.

3 is a block diagram illustrating a display panel and a display panel driver. 4 is a circuit diagram illustrating a deterioration compensator.

3 and 4 , the screen AA of the N-th (N is a natural number) display panel PNL(N) includes a pixel array displaying an input image. The pixel array has a plurality of data lines 102, a plurality of gate lines 104 crossing the data lines 102, a plurality of sensing lines 103 in parallel with the data lines 102, and a matrix form. Includes pixels to be placed.

Each of the pixels includes a plurality of sub-pixels 101 having different colors for realizing color. The sub-pixels 101 may be divided into a red sub-pixel, a green sub-pixel, and a blue sub-pixel. Each of the pixels may further include a white sub-pixel. Each of the sub-pixels 101 includes a pixel circuit 101A.

The N-th display panel driver includes a normal driving mode for displaying an input image on a screen, and a sensing mode for sensing electrical characteristics of sub-pixels for each sub-pixel using the deterioration compensator as shown in FIG. 4 . ) works as In the normal driving mode, the N-th display panel driver transmits the pixel data of the input image to the pixels of the N-th display panel PNL(N) under the control of a timing controller (hereinafter, referred to as “TCON”) 130 . write in In the sensing mode, the display panel driver senses electrical characteristics of the driving device for each sub-pixel under the control of the TCON 130 , and selects a compensation value according to the sensing result to compensate for deterioration of each of the sub-pixels.

The N-th display panel driver includes a data driver 110 and a gate driver 120 . A multiplexer (hereinafter, referred to as “MUX”) 112 disposed between the data driver 110 and the data lines 102 may be disposed in the sensing mode under the control of the TCON 130 . The data line 102 and the sensing line 103 connected to the deterioration compensator are selected.

The data driver 110 uses a digital-to-analog converter (hereinafter, referred to as “DAC”) as shown in FIG. 4 to generate pixel data (digital) of an input image received from the TCON 130 in every frame period. data) into a gamma compensation voltage to output a data voltage (Vdata). The data voltage Vdata is applied to the pixels through the MUX 112 and the data line 102 . As shown in FIG. 4 , the DAC and the sensing unit 111 of the degradation compensator may be integrated in an integrated circuit (IC) of the data driver 110 .

The gate driver 120 outputs a gate signal (or a scan signal) to the gate lines 104 under the control of the TCON 130 . The gate signal may include, but is not limited to, a first scan signal SCAN1 , a second scan signal SCAN2 , and an emission signal EM as shown in FIG. 4 . The gate signals SCAN1 , SCAN2 , and EM are synchronized with the data voltage Vdata output from the data driver 110 . The gate signals SCAN1 , SCAN2 , and EM may be generated as pulses swinging between the gate high voltage VGH and the gate low voltage VGL. The transistors of the pixel circuit 101A may be turned on according to the gate high voltage VGH of the gate signals SCAN1 , SCAN2 , and EM. The gate driver 120 may be implemented as a gate in panel (GIP) circuit that is directly formed on a bezel area of the display panel 100 together with the TFT array of the screen AA.

The N-th display panel driving unit further includes a display module power supply unit. The display module power unit receives main power from the SET 200 to generate driving power for the N-th display panel driver and analog power for the display panel PNL(N). For example, the display module power supply includes the N-th display panel driver and the driving power of the TCON, a gamma reference voltage, a reference voltage (hereinafter referred to as “VPREO”), and a gate high voltage (VGH). A power such as a gate low voltage VGL is output. The gamma reference voltage is divided by the voltage divider circuit, is converted into a gamma compensation voltage corresponding to the grayscale voltage of the pixel data, and is supplied to the data driver 110 . VPREO is set to a voltage greater than or equal to the turn-on voltage of the OLED in order to measure the degradation level of the OLED for each sub-pixel. VPREO can be set to the same voltage in all pixels. The display module power supply unit includes a charge pump, a regulator, a buck converter, a boost converter, and the like.

The TCON 130 controls the operation timing of the N-th display panel driver in a normal driving mode and a sensing mode. The TCON 130 receives the pixel data of the input image and a timing signal synchronized with the pixel data from the SET 200 . The TCON 130 transmits the pixel data of the input image from the SET 200 to the data driver 110 . The TCON 130 generates timing control signals for controlling the operation timing of the display panel driver using the timing signal received from the SET 200 to control the operation timing of the display panel driver.

The TCON 130 may include the compensating unit 131 of the degradation compensator shown in FIG. 4 .

The degradation compensator senses each of the sub-pixels of the N-th display panel PNL(N), and compensates for pixel data to be written in each of the sub-pixels based on the sensing result of the sub-pixels. The degradation compensator compares the degradation measurement values DM of the N-th display panel PNL(N) and the adjacent display panels PNL(N-1) and PNL(N+1) thereto. (DM) determines the target luminance as a measurement value of deterioration of the display panel with the largest value. The target luminance defines the maximum luminance of the N-th display panel PNL(N). The larger the degradation measurement value DM, the lower the target luminance. The maximum luminance in all pixels of the N-th display panel PNL(N) is limited by the target luminance. The target luminance is a value that is inversely proportional to a degradation measure (DM) of the display panel in order to prevent a reduction in lifetime due to deterioration of pixels. The target luminance is implemented as a look-up table and stored in a memory connected to the TCON 130 .

A degradation measurement value (DM) is a value representative of the degradation level of the display panel. It is calculated as an average value of sensing data obtained from all sub-pixels of the display panel in each of the display panels when deterioration is sensed in the sensing mode. The deterioration measurement value DM is updated every time deterioration is sensed and stored in a memory connected to the TCON 130 . The deterioration compensator compensates for deterioration of each of the sub-pixels by adjusting a gain of pixel data in each sub-pixel in order to compensate for the level of deterioration based on the sensed data of the sub-pixels based on the target luminance selected according to the deterioration measurement value of the display panel. . The deterioration compensating unit may be performed for every power-on sequence in which power is started to be generated in the display panel driver, and may be performed at a predetermined time period within a period in which an image is displayed.

As shown in FIG. 4 , the degradation compensator includes the sensing line 103 connected to the pixel circuit 101A in each of the sub-pixels 101 , the sensing unit 111 , and sensing data (digital data) from the sensing unit 111 . and a compensation unit 131 for receiving The compensator 131 may be built in the TCON 130 .

The memory connected to the TCON 130 stores OLED sensing values in each of the sub-pixels at the time of product shipment, that is, before deterioration. The sensing unit 111 senses the voltage of the OLED at each of the sub-pixels through the sensing line 103 when the deterioration is sensed in the sensing mode, and uses an analog-to-digital converter (hereinafter referred to as “ADC”). The OLED sensing value is converted into sensing data (digital data) and transmitted to the compensation unit 131 . The compensator 131 may determine the degree of deterioration of the OLED in each of the sub-pixels by comparing the sensed value of the OLED after deterioration with the initial sensed value before deterioration. As the deterioration progresses, the sensing voltage of the OLED increases. Therefore, the larger the sensing data of the OLED, the greater the deterioration of the OLED, so the compensation value of the pixel data, that is, the gain is determined to be a larger value.

The compensator 131 calculates the deterioration measurement value DM of the N-th display panel PNL(N) based on the sensing result for each sub-pixel, and the peripheral display panels PNL received from the other TCONs 130 . The measured deterioration values DM of (N-1), PNL(N+1)) are compared with the measured deterioration values DM of the N-th display panel PNL(N). The compensator 131 selects the target luminance corresponding to the largest deterioration measurement value DM. The compensator 131 compensates for the luminance of the pixel data by limiting a gain so that the luminance of the pixel is not increased beyond the selected target luminance.

5A and 5B are circuit diagrams illustrating in detail an example of a pixel circuit and a deterioration compensator.

5A and 5B , the pixel circuit 101A is supplied with a pixel driving voltage (hereinafter referred to as “VDD”) and a low-potential power supply voltage (hereinafter referred to as “VSS”). VPREO for turning on the OLED is supplied to the pixel circuit 101A when the deterioration is sensed in the sensing mode.

The pixel circuit 101A includes an OLED, a plurality of transistors T1 to T5 and DT, and a capacitor Cst. The transistors T1 to T5 and DT may be implemented as a p-channel transistor PMOS.

The OLED emits light with a current generated according to the gate-source voltage Vgs of the driving transistor DT that varies according to the data voltage Vdata. The OLED includes an organic compound layer formed between an anode and a cathode. The organic compound layer includes a hole injection layer (HIL), a hole transport layer (HTL), an emission layer (EML), an electron transport layer (ETL), an electron injection layer (Electron Injection layer, EIL) and the like, but is not limited thereto. The anode of the OLED is connected to the fourth and fifth transistors T4 and T5, and the cathode of the OLED is connected to a VSS node to which a low potential power voltage (hereinafter, referred to as “VSS”) is applied.

The first transistor T1 is turned on according to the first scan signal SCAN1 to connect the data line 102 to the first electrode of the capacitor Cst to supply the data voltage Vdata to the capacitor Cst. . The first transistor T1 has a gate connected to the first gate line 1041 to which the first scan signal SCAN1 is applied, a first electrode connected to the data line 102 , and a first electrode connected to the capacitor Cst. and a second electrode.

The second transistor T2 is turned on according to the second scan signal SCAN2 to connect the gate and the second electrode of the driving transistor DT. The second transistor T2 has a gate connected to the second gate line 1042 to which the second scan signal SCAN2 is applied, and the second transistor T2 connected to a node between the second electrode of the capacitor Cst and the gate of the driving transistor DT. It includes a first electrode and a second electrode connected to a node between the second electrode of the second driving transistor DT and the first electrode of the fourth transistor T4 .

The third and fourth transistors T3 and T4 are turned on in the normal driving mode to form a current path between VDD and the OLED, while maintaining an off state in the sensing mode. The third transistor T3 is turned on according to the emission signal EM to connect a node between the first electrode of the first transistor T1 and the first electrode of the capacitor Cst to the sensing line 103 . The third transistor T1 has a gate connected to the third gate line 1043 to which the light emitting signal EM is applied, and a node connected between the first electrode of the first transistor T1 and the first electrode of the capacitor Cst. It includes a first electrode and a second electrode connected to the sensing line 103 .

The fourth transistor T4 is turned on according to the light emission signal EM to connect a node between the second electrode of the driving transistor DT and the second electrode of the second transistor T2 to the anode of the OLED. The fourth transistor T4 has a gate connected to the third gate line 1043 , a first electrode connected to a node between the second electrode of the driving transistor DT and the second electrode of the second transistor T2 , and the OLED and a second electrode connected to the node between the anode and the second electrode of the fifth transistor T5.

The fifth transistor T5 is turned on according to the second scan signal SCAN2 to connect the sensing line 103 to the anode of the OLED. The fifth transistor T5 has a gate connected to the second gate line 1042 , a first electrode connected to the sensing line 103 , and a second electrode connected to a node between the anode of the OLED and the second electrode of the fourth transistor T4 . Includes 2 electrodes.

The driving transistor DT supplies a current to the OLED according to the gate-source voltage Vgs. The driving transistor DT includes a gate connected to a node between the first electrode of the capacitor Cst and the first electrode of the second transistor T2 , a second electrode connected to the VDD line to which VDD is applied, and a second transistor T2 . ) and a second electrode connected to a node between the second electrode of the fourth transistor T4 and the first electrode of the fourth transistor T4.

The deterioration sensing method in the sensing mode includes an OLED light emitting step and an OLED voltage sensing step. The sensing unit 111 operates in a sensing mode.

The sensing unit 111 includes first to third switch elements SCS, PRE, and SEN, a capacitor Cs, and an ADC. The first switch SCS is used when sensing is divided by color of the sub-pixel. When the OLED deterioration of the red sub-pixels is sensed, the first switch SCS connected to the red sub-pixels is turned on in the OLED light emitting step, while the first switch SCS connected to the sub-pixels of a color other than red is turned on. ) is turned off in the OLED light emitting stage. When the OLED deterioration of the green sub-pixels is sensed, the first switch SCS connected to the green sub-pixels is turned on in the OLED light emitting step, while the first switch SCS connected to the sub-pixels of a color other than green ) is turned off in the OLED light emitting stage. When the OLED deterioration of the blue sub-pixels is sensed, the first switch SCS connected to the blue sub-pixels is turned on in the OLED light emitting step, while the first switch SCS connected to the sub-pixels of a color other than blue ) is turned off in the OLED light emitting stage. All of the first switches SCS are turned off in the OLED voltage sensing step.

The second switch PRE is turned on in the OLED light emitting stage to supply VPREO to the OLED. The second switch PRE is turned off in the OLED voltage sensing step.

The third switch SEN is turned off in the OLED light emitting step. The third switch SEN is turned on in the OLED voltage sensing step to charge the capacitor Cs with the voltage of the capacitor Cps of the sensing line 103 . In the sensing step, the ADC converts the voltage of the capacitor Cs, that is, the voltage of the OLED, into digital data and outputs the sensed data.

The multiplexer 112 includes a first transistor M1 connecting the sensing unit 111 to the sensing line 103 , and a second transistor M2 connecting the sensing unit 111 to the data line 102 . . The first transistor M1 is turned on according to the first MUX signal SMUX to connect the sensing unit 111 to the sensing line 103 . The second transistor M2 is turned on according to the second MUX signal DMUX to connect the sensing unit 111 to the data line 102 .

FIG. 5A shows the current path of the sensing unit 111 and the pixel circuit 101A in the OLED light emission stage of the sensing mode. 5B illustrates current paths of the sensing unit 111 and the pixel circuit 101A in the sensing step of the sensing mode. In the OLED emitting phase, VPREO is applied to the anode of the OLED to turn on the OLED. At this time, current flows through the OLED. If the OLED is not deteriorated, the charge charged in the capacitor Cps of the sensing line 103 is small because the amount of current flowing through the OLED in the OLED light emission stage is large. On the other hand, when the OLED is deteriorated, the resistance of the OLED increases, so that the amount of current flowing through the OLED between VPREO and VSS in the OLED light emitting stage decreases and the amount of charge charged in the capacitor Cps of the sensing line 103 increases. . Accordingly, as the deterioration of the OLED increases, the voltage of the capacitor Cps increases. In the sensing step, the capacitor Cs of the sensing unit 111 is charged with the voltage charged in the capacitor Cps of the sensing line 103 . As the deterioration of the OLED increases, the voltage of the capacitor Cs increases. Therefore, the sensing data obtained through the ADC increases as the deterioration of the OLED increases.

6 is a block diagram showing the compensation unit 131 in detail. 7 is a diagram illustrating a compensation look-up table (LUT1). 8 is a diagram illustrating a luminance lookup table LUT2.

Referring to FIG. 6 , the compensator 131 includes a target luminance determiner 72 and a pixel data compensator 74 .

The pixel data compensator 74 receives the target luminance of the luminance lookup table LUT1 from the target luminance determination unit 72 and sensing data from the sensing unit 111 . The pixel data compensator 74 determines whether to compensate the pixel data for each sub-pixel based on the sensing data for each sub-pixel. In order to compensate for the pixel data, the pixel data compensator 74 inputs the sensing data to the compensation lookup table LUT2 and multiplies the gain output from the compensation lookup table LUT2 by the pixel data to lower the luminance of the pixel data. compensate for In FIG. 6 , “DATA” is pixel data before compensation, and “DATA′” is pixel data after compensation output from the pixel data compensation unit 74 . After compensation, the pixel data DATA' is transmitted to the data driver 110 .

The pixel data compensator 74 selects a gain curve of the compensation lookup table LUT2 according to the luminance lookup table LUT1 selected by the target luminance determination unit 72 , and compensates the pixel data with the selected gain curve. As shown in FIG. 7 , the compensation lookup table LUT2 is set as a gain curve in which a gain increases as the sensed data increases. As described above, as the deterioration of the OLED increases, the sensing data has a larger value. The gain of the compensation lookup table LUT2 is limited according to the target luminances TL1 and TL2 as shown in FIG. 7 . The lower the target luminance, the lower the maximum gain value. For example, the maximum gain value is lower when the target luminance is TL2 than the maximum gain value when the target luminance is TL1. Accordingly, the compensation lookup table LUT2 is set with a plurality of gain curves having different maximum gain values according to the target luminance.

Meanwhile, the target luminance at the time of product shipment is stored in the memory as a default value. When a deterioration measurement value (DM) is calculated based on the deterioration sensing result in the first frame period after product shipment, the target luminance is updated with the deterioration measurement value (DM) is updated in real time. The target luminance stored in the memory in the power-off sequence is read in the next power-on sequence.

The pixel data compensator 74 is an average value of the sensed data for all sub-pixels of the N-th display panel PNL(N), and a deterioration measurement value DM(N) for the N-th display panel PNL(N). ) is calculated. The deterioration measurement value DM(N) of the N-th display panel PNL(N) represents the average luminance after deterioration of the N-th display panel PNL(N).

The target luminance determination unit 72 may generate deterioration measurement values DA(N-1) and DM(N+1) indicating average luminance after deterioration of the peripheral display panels PNL(N-1) and PNL(N+1). ) and a deterioration measurement value PNL(N) for the N-th display panel PNL(N) from the pixel data compensator 74. The target luminance determination unit 72 receives the deterioration measurement values DM (N-1), DM(N), DM(N+1)) is compared to select the largest deterioration measurement value DM The target luminance determination unit 72 determines the largest deterioration measurement value DM Target luminance is selected by inputting it into the luminance lookup table LUT1, in which the target luminance having an inverse relationship with the luminance measurement value DM is set in the luminance lookup table LUT1 as shown in Fig. 8. As described above , since the luminance measured value DM represents the average luminance after deterioration of the display panel, the larger the luminance measured value DM, the more severe the deterioration of the display panel. The luminance is set to a smaller value as the deterioration measurement value is larger The target luminance defines the maximum luminance of pixels Therefore, the maximum luminance of the pixel data compensated by the pixel data compensator 74 is limited by the target luminance. As described above, the target luminance is determined by the target luminance determining unit 72 based on a comparison result of deterioration measurement values of the display panels PNL(N-1), PNL(N), and PNL(N+1).

The compensator 131 may be disposed on the TCON 130 of each of the display panels. Accordingly, as shown in FIG. 9 , deterioration measurement values DM(N-1), DM(N), DM(N+1)) is shared. The TCONs TCON(N-1), TCON(N), and TCON(N+1) may be mounted 1:1 on the control board 204 shown in FIG. 2 . For example, the Nth TCON(TCON(N)) is mounted on the Nth control board 204 corresponding to the Nth display panel PNL(N).

10 is a diagram illustrating an example in which a target luminance is selected by comparing deterioration measurement values of display panels in a SET 200 of a tiled display.

Referring to FIG. 10 , the TCONs (TCON(N-1), TCON(N), and TCON(N+1)) mounted on the control boards 204 are the deterioration measurement values DM(N-1), DM (N), DM(N+1)) may be calculated and transmitted to the SET 200 . The SET 200 compares the deterioration measurement values DM(N-1), DM(N), DM(N+1) received from the control boards 204 to obtain the largest value in the luminance lookup table LUT1. The target luminance indicated by the deterioration measurement value is selected. The SET 200 transmits the target luminance selected according to the degradation measurement value to the TCONs TCON(N-1), TCON(N), and TCON(N+1) of the control boards 204 . In this embodiment, the luminance lookup table LUT1 is stored in the memory of the SET 200 , and there is no need to store the luminance lookup table LUT1 in the memory of the control boards 204 .

11 is a diagram illustrating an example in which deterioration measurement values are compared in each of timing controllers mounted on control boards of a tiled display to select a target luminance.

Referring to FIG. 11 , a deterioration measurement value is calculated from each of the TCONs (TCON(N-1), TCON(N), and TCON(N+1)) mounted on the control boards 204 and transmitted to another TCON. , the deterioration measurement values (DM(N-1), DM(N), DM(N+1)) in each of the TCONs (TCON(N-1), TCON(N), TCON(N+1)) By comparison, the target luminance corresponding to the largest degradation measurement value is selected. In this embodiment, the luminance lookup table LUT1 should be stored together with the compensation lookup table LUT2 in the memory of the control boards 204 . Since this embodiment does not need to support the target luminance selection function in the SET 200, it can be implemented with an existing SET board.

Those skilled in the art from the above description will be able to see that various changes and modifications are possible without departing from the technical spirit of the present invention. Accordingly, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims.

72: target luminance determining unit 74: pixel data compensating unit
110: data driving unit 111: sensing unit
120: gate driving unit 131: compensating unit
130, TCON, TCON(N-1), TCON(N), TCON(N+1): Timing controller
200: integrated control box (SET) 202: cable
204: control board DM: deterioration measurement value
PNL1~PNL12, PNL(N-1), PNL(N), PNL(N+1) : Display panel

Claims (9)

a first display panel driver for driving the first display panel;
a first degradation compensator for compensating for pixel data to be written in each of the pixels of the first display panel based on a result of sensing an electrical characteristic of each of the pixels disposed on the first display panel;
a second display panel driver for driving the second display panel; and
and a second degradation compensator for compensating for pixel data to be written in each of the pixels of the second display panel based on a result of sensing the electrical characteristics of each of the pixels disposed on the second display panel;
The first degradation compensator calculates a first degradation measurement value representing the degradation level of the first display panel and transmits it to the second degradation compensator;
The second degradation compensator calculates a second degradation measurement value representing the degradation level of the second display panel and transmits it to the first degradation compensator;
The first degradation compensator selects a first compensation value limited by a target luminance defining the maximum luminance of the first and second display panels, and applies the selected first compensation value to each of the pixels of the first display panel. modulates pixel data to be written, and lowers the maximum value of the first compensation value when the target luminance is lowered;
The second degradation compensator selects a second compensation value limited by the target luminance, modulates pixel data to be written in each of the pixels of the second display panel with the selected second compensation value, and reduces the target luminance. when the tiled display lowers the maximum value of the second compensation value. The method of claim 1,
The first deterioration measurement value is an average value of sensing data obtained from all sub-pixels of the first display panel;
The second degradation measurement value is an average value of sensing data obtained from all sub-pixels of the second display panel. The method of claim 1,
Each of the first and second degradation compensators selects the target luminance based on a larger degradation measurement value among the first and second degradation measurement values. 3. The method of claim 2,
The tiled display is configured to decrease the target luminance as the first and second measurement values of deterioration increase. delete delete 3. The method of claim 2,
A tiled display in which the first and second compensation values increase as the sensed data increases. calculating a first degradation measurement value representing a degradation level of the first display panel based on a result of sensing electrical characteristics of each of the pixels disposed on the first display panel;
calculating a second degradation measurement value representing a degradation level of the second display panel based on a result of sensing electrical characteristics of each of the pixels disposed on the second display panel;
selecting a larger degradation measurement value among the first and second degradation measurements;
selecting a target luminance defining maximum luminance of the first and second display panels according to the selected deterioration measurement value;
selecting a first compensation value limited by the target luminance and modulating pixel data to be written in each of the pixels of the first display panel with the selected first compensation value;
selecting a second compensation value limited by the target luminance and modulating pixel data to be written in each of the pixels of the second display panel with the selected second compensation value; and
and lowering maximum values of the first and second compensation values when the target luminance is lowered. delete

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