KR20060112995A - Light emitting display device and control method thereof - Google Patents

Abstract

The present invention relates to a light emitting display device and a control method thereof, and an object of the present invention is to compensate for a decrease in luminance due to deterioration of a light emitting device. In particular, the present invention relates to a light emitting display device and a method of controlling the same, in which the memory of the lookup table is reduced and the hardware configuration is simplified by compensating luminance mainly for a portion that is likely to deteriorate in the pixel portion.

In the present invention, a pixel portion including a plurality of scan lines, a plurality of data lines, and a plurality of pixels electrically connected to the plurality of scan lines and the plurality of data lines, and a power supply unit for supplying power to the pixel portion via a power supply line. And a current measuring unit for dividing the pixel unit into a first region and a second region, and measuring a current flowing through each pixel included in the second region, and applying the current to the second region according to the current value measured by the current measuring unit. A data corrector for correcting corresponding video data, a data driver for transmitting a data signal corresponding to the corrected video data transmitted from the data corrector to the plurality of data lines, and applying a scan signal to the plurality of scan lines It includes a scan driver.

Description

LIGHT EMITTING DISPLAY AND CONTROL METHOD OF THE SAME}

1 is a view showing the structure of a conventional light emitting display device.

2 is a diagram illustrating a structure of a light emitting display device according to a first embodiment of the present invention.

3 is a diagram illustrating a structure of a light emitting display device according to a second embodiment of the present invention;

Cotton.

4 is a diagram illustrating an example of a data correction unit employed in the light emitting display device of FIGS. 2 and 3.

5 is a flowchart illustrating a control method of a light emitting display according to an exemplary embodiment of the present invention.

6A and 6B illustrate an example of a pixel employed in the light emitting display device of FIGS. 2 and 3.

*** Explanation of symbols for main parts of drawing ***

200: power supply unit 410: memory unit

300: current measuring unit 500: data driver

400: data correction unit

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display device and a control method thereof, and more particularly, to a light emitting display device and a method of controlling the same, which compensate for a decrease in luminance due to deterioration of a pixel.

Recently, various flat panel display devices having a lighter weight and a smaller volume than the cathode ray tube have been developed. In particular, a light emitting display device having excellent luminous efficiency, brightness, viewing angle, and fast response speed has been attracting attention.

Such light emitting displays include an organic light emitting display using an organic light emitting element and an inorganic light emitting display using an inorganic light emitting element. The organic light emitting diode is also called an organic light emitting diode (OLED), and includes an anode electrode, a cathode electrode, and an organic light emitting layer disposed between them to emit light by a combination of electrons and holes. The inorganic light emitting device is also referred to as a light emitting diode (LED), and unlike an organic light emitting diode, includes an inorganic light emitting layer, for example, a light emitting layer made of a PN bonded semiconductor.

1 is a view showing the structure of a conventional light emitting display device.

Referring to FIG. 1, the light emitting display device includes a pixel unit 10, a data driver 20, a scan driver 30, and a power supply unit 40.

The pixel portion 10 includes n × m pixels 5 each having a light emitting element (not shown), and n scan lines S1, S2,..., Sn formed in a row direction and transmitting scan signals. And m data lines D1, D2,..., Dm formed in a column direction to transfer data signals, and m first power lines L1 and second power lines L2 to transfer power. do. The pixel unit 10 emits a light emitting element (not shown) by the scan signal, the data signal, and the first power source ELVdd and the second power source ELVss to display an image. According to the drawing, the first power supply line L1 is arranged in the column direction in the pixel portion 10, but this may be arranged in the row direction. In addition, although the second power supply line L2 is arranged in the row direction in the pixel portion 10 according to the drawing, this represents an equivalent circuit, and the second power supply line L2 represents the entire region of the pixel portion 10. And may be electrically connected to each pixel 5.

The data driver 20 is connected to the data lines D1, D2,..., Dm and is a means for applying a data signal to the pixel unit 10.

The scan driver 30 is connected to the scan lines S1, S2,..., Sn and is a means for applying a scan signal to the pixel unit 10.

The power supply unit 40 serves to apply the first power source ELVdd and the second power source ELVss to each pixel 5.

The conventional light emitting display device having the above configuration has a problem in that the light emitting device deteriorates with time. That is, as time passes, the light emitting device deteriorates, thereby increasing the internal resistance of the light emitting device. Accordingly, even when the same data voltage is supplied to the pixel, the luminance of the pixel decreases with time.

Accordingly, an object of the present invention is to provide a light emitting display device and a method of controlling the same, which compensate for a decrease in luminance due to deterioration of a light emitting device.

As a technical means for achieving the above object, a first aspect of the present invention provides a pixel portion including a plurality of scan lines, a plurality of data lines, and a plurality of pixels electrically connected to the plurality of scan lines and the plurality of data lines. A power supply unit which supplies power to the pixel unit through a line, a current measuring unit which divides the pixel unit into a first region and a second region, and measures a current flowing through each pixel included in the second region, and the current measurement A data corrector for correcting video data corresponding to the second area according to a current value measured by the unit, and transmitting a data signal corresponding to the corrected video data transmitted from the data corrector to the plurality of data lines. A light emitting display device includes a data driver and a scan driver configured to apply a scan signal to the plurality of scan lines. Will.

According to a second aspect of the present invention, there is provided a method of controlling a light emitting display device including a pixel that emits light by a current corresponding to a data signal, the method comprising: (a) measuring a current flowing in a predetermined area among a plurality of areas of a pixel unit; b) determining a correction range by comparing the deviation between the current value measured in step (a) and the reference current value, and correcting the video data corresponding to the correction range; and (c) the corrected video data. The present invention provides a method of controlling a light emitting display device, the method comprising transmitting the data to the data driver.

Hereinafter, a light emitting display device according to an exemplary embodiment will be described with reference to FIGS. 2 to 6.

2 is a diagram illustrating a structure of a light emitting display device according to a first embodiment of the present invention.

Referring to FIG. 2, the light emitting display device according to the present invention includes a pixel unit 100, a power supply unit 200, a current measuring unit 300, a data correction unit 400, a data driver 500, and a scan driver. And 600.

The pixel portion 100 includes n x m pixels 50, n scan lines S1, S2, ..., Sn arranged in the row direction, and m data lines D1, D2 arranged in the column direction. .., Dm) and a first power supply line L1 and a second power supply line L2. Each pixel 50 is connected to the data lines D1, D2, ... Dm and the scan lines S1, S2, ... Sn, and is transmitted through the scan lines S1, S2, ... Sn. The image is displayed by supplying a current corresponding to the data signal selected by the scanning signal to a light emitting element (not shown). In addition, each pixel 50 is electrically connected to the first power line L1 and the second power line L2 to receive the first power source ELVdd and the second power source ELVss from the power supply unit 200. . According to the drawing, the first power supply line L1 is arranged in the column direction in the pixel portion 100, but this may be arranged in the row direction. In addition, although the second power supply line L2 is arranged in the row direction in the pixel portion 100 according to the drawing, this represents an equivalent circuit, and the second power supply line L2 represents the entire region of the pixel portion 100. And may be electrically connected to each pixel 50.

In addition, the pixel unit 100 may be divided into a first region in which deterioration is less likely because a high gray level is not expressed in a process of representing an image, and a second region in which deterioration is easily generated by mainly expressing a high gray scale. In this case, the first area and the second area may be classified differently according to the type of the image represented by the pixel unit 100. The pixel unit 100 may represent a moving picture, a still image, and the like. In the case of a moving picture, the center part of the pixel part 100 is most brightly expressed, and the outer part is less brightly expressed. When a still image such as a document is represented, a portion displaying an icon such as a symbol or a pattern may be called an icon portion, and the icon portion may be a portion expressing a specific color and brightness. In the case of a moving picture, the deterioration of the light emitting device included in the center proceeds quickly. Therefore, when the pixel unit 100 displays a video, the outer portion of the pixel unit 100 belongs to the first region and the center portion of the second region, and the pixel unit 100 displays the still image. Icon portion second area, and other parts belong to the first area. In this case, the first area and the second area may be selected as a plurality of areas.

The power supply unit 200 supplies the first power source ELVdd and the second power source ELVss to the pixel unit 100.

The current measuring unit 300 measures a current flowing through each of the n first power lines L1 when the display grayscale voltage is transmitted to one of the plurality of pixel rows included in the second area of the pixel unit 100. This is transmitted to the data correction unit 400. At this time, it is preferable to measure the current flowing through the pixels 50 in all the regions, but since it takes a long time and the memory becomes large, only the current value flowing through the pixels 50 in the second region that deteriorates quickly. Measure

The data corrector 400 corrects the video data input to the display device in response to the current value of each pixel 50 measured by the current measurer 300 in the second area, and corrects the corrected video data by the data driver. 500).

The data driver 500 distinguishes the image display period and the measurement period of the pixel unit 100 and outputs a first data signal and a second data signal, respectively.

The first data signal is a data signal supplied from the data driver 500 when the pixel 50 displays an image corresponding to the image display period, that is, the input video data. The second data signal transmits the display gray voltage and the black gray voltage to the pixel 50 during the measurement period, that is, during the calculation of the correction range for correcting the first data signal input to the data driver 500, thereby measuring the measured data. The data signal is corrected in correspondence with the reference current value. In addition, the second data signal divides the pixel unit 100 into a first region and a second region, and always transmits a black gray voltage to a first region where an image is not displayed. In the second region in which the image is displayed, one of the plurality of pixel rows is selected for one frame, and the display gray voltage is transmitted, and the black gray voltage is transmitted to the pixels included in the remaining rows. The display gray voltage is sequentially applied to each row of the pixel unit 100.

The scan driver 600 sequentially applies scan signals to the scan lines S1, S2,... Sn to select pixels and transmit the data signals to the selected pixels in order.

3 is a diagram illustrating a structure of a light emitting display device according to a second embodiment of the present invention;

Cotton.

In the light emitting display device according to the second embodiment of the present invention, other components except for the current measuring unit 300 and the data driver 500 are the same as the light emitting display device according to the first embodiment of the present invention. Detailed description thereof will be omitted. Referring to Figure 3,

The current measuring unit 300 receives a current flowing through the second power supply line L2 when the display grayscale voltage is transmitted to one of the plurality of pixels 50 included in the second area of the pixel unit 100. The measurement is transmitted to the data correction unit 400.

The data driver 500 distinguishes the image display period and the measurement period of the pixel unit 100 and outputs a first data signal and a second data signal, respectively.

The first data signal is a data signal supplied from the data driver 500 when the pixel 50 displays an image corresponding to the image display period, that is, the input video data. The second data signal transmits the display gray voltage and the black gray voltage to the pixel 50 during the measurement period, that is, during the calculation of the correction range for correcting the first data signal input to the data driver 500, and the measured data. The data signal is corrected corresponding to the reference current value. In addition, the second data signal divides the pixel unit 100 into a first region and a second region, and always transmits a black gray voltage to a first region that does not display an image. In the second area displaying the image, one of the plurality of pixels is selected for one frame to transmit the display gray voltage, and the other gray pixels are transmitted with the black gray voltage. The display gray voltage is sequentially applied to each pixel 50 of the pixel unit 100. As shown in FIG. 3, when the second power supply ELVss and the current measurement unit 300 are connected, when the first power supply ELVdd and the current measurement unit 300 are connected, the first power supply ELVdd is connected to the current measurement unit ( It is possible to overcome the problem that is lowered by 300).

According to the light emitting display device of FIGS. 2 and 3, the current measuring unit 300 does not measure the current of the entire pixel unit 100, but measures the current of a predetermined region based on a portion that is likely to deteriorate. By correcting the video data corresponding thereto, the size of the memory can be reduced, and the time consumed during the current measurement can be reduced.

4 is a diagram illustrating an example of a data correction unit employed in the light emitting display device of FIGS. 2 and 3.

Referring to FIG. 4, the data correction unit 400 includes a memory unit 410 including a lookup table 420 and an operation unit 430.

The memory unit 410 includes a lookup table 420, and the lookup table 420 actually displays reference current values, measured current values, and correction ranges of the respective pixels 50 included in the second area to correct the video data. Save it. The reference current value refers to the ideal current flowing in the pixel when the second data signal is input, and the measured current value substantially refers to the current measured by the current measurement unit when the second data signal is input, and the correction range is measured. When a deviation occurs between the current value and the reference current value, it means the range of video data corresponding to the deviation. In addition, the memory unit 410 stores respective reference current values and measured current values for all the pixels 50 included in the second area of the pixel unit 100. In this case, when the reference current value is determined as the measured current value in the previous step, the deviation between the reference current value and the measured current value is determined and the current value compensated for the deviation is stored in the reference current value storage area of the memory unit 410. Then, the correction range is calculated according to the deviation between the reference current value and the measured current value to create a lookup table 420.

The calculator 430 corrects the video data according to the information of the pixels 50 included in the second area stored in the lookup table 420 and transmits the corrected video data to the data driver 500.

Referring to the operation of the operation unit 430, for example, 4-bit video data, it is assumed that a reference current of 2 mA flows to a light emitting device (not shown) when the video data '1001' is input to the selected pixel 50. Then, a correction range for correcting 1 bit of video data per 0.1 mA of current is determined. When '1001' video data is input to the selected pixel 50, if the current flowing through the selected pixel is measured and only 1.9 mA of current flows without the current of 2 mA as the reference current value, 0.1 mA of current is applied to the selected pixel 50. Re-input the corrected video data to '1010' by adding 1 bit to compensate. Also, when the current value measured when the current value flowing through the selected pixel 50 is input by inputting '1001' video data is 2.1 mA, the video data corrected to '1000' subtracted by one bit is selected again. Input 50) and adjust so that the current can flow as much as 2mA, the reference current value. Such an operation occurs according to a reference current value designated for each pixel, and the data corrected by the data corrector 400 is transmitted to the data driver 500.

5 is a flowchart illustrating a control method of a light emitting display device according to an embodiment of the present invention.

Referring to FIG. 5, the method of controlling the light emitting display device according to the present invention may be shown in the first steps ST100 to the third steps ST120.

In the first step ST100, a black gray voltage is transmitted to a first region in which video data is not to be corrected, and a pixel 50 is selected by selecting one row of pixels 50 for one frame in a second region to correct video data. In this case, the display gray voltage is transmitted to the terminals, and the current value flowing through the first power line is measured. Alternatively, one pixel 50 is selected for one frame to transfer the display gray voltage to the selected pixel 50, and measure a current value flowing through the second power line.

The second step ST110 compares the current value measured in the second region with the reference current value through the first step ST110 and when the deviation between the measured current value and the reference current value occurs, the lookup table 420. If the measured current value is smaller than the reference current value, the video data is corrected by adding the difference. If the measured current value is larger than the reference current value, the video data is corrected by subtracting the difference. When there is no deviation between the measured current value and the reference current value in the second area, the video data is not corrected.

The third step ST120 transmits the corrected video data corresponding to the reference current value to the data driver 500.

6A and 6B illustrate an example of a pixel employed in the light emitting display device of FIGS. 2 and 3. 6A illustrates that the current measuring unit 300 is connected to each of the plurality of first power lines L1 according to the first embodiment, and FIG. 6B illustrates that the current measuring unit 300 is the second power source according to the second embodiment. It is connected to the line L2.

Referring to FIGS. 6A and 6B, the pixel 50 of the light emitting display device includes a light emitting device OLED, a first transistor M1, a capacitor Cst, and a second transistor M2.

The gate of the first transistor M1 is connected to the scan line Sn, the drain is connected to the gate of the second transistor M2, and the source is connected to the data line Dm. The first transistor M1 transmits a voltage corresponding to the data voltage applied to the data line Dm to the capacitor Cst in response to the scan signal applied to the scan line Sn.

The first power supply ELVdd is applied to the first terminal of the capacitor Cst, and the second terminal is connected to the gate of the second transistor M2. The capacitor Cst stores a voltage corresponding to the data voltage applied to the data line Dm in the period in which the first transistor M1 is on, and stores the voltage during the period in which the first transistor M1 is in the off state. It performs the function of maintaining.

The gate of the second transistor M2 is connected to the second terminal of the capacitor Cst, the first power source ELVdd is applied to the source, and the drain thereof is connected to the anode electrode of the light emitting element. The second transistor M2 generates a current corresponding to the stored voltage of the capacitor and the first power supply ELVdd, and supplies the current to the light emitting device OLED.

Although the technical spirit of the present invention has been described in detail according to the above preferred embodiment, it should be noted that the above embodiment is for the purpose of description and not of limitation. In addition, it will be understood by those skilled in the art that various modifications are possible within the scope of the technical idea of the present invention.

 According to the light emitting display device and the control method thereof according to the present invention, the luminance of the light emitting device is compensated for, and the luminance of the pixel portion is compensated mainly for the portion that tends to be degraded, thereby reducing the memory of the lookup table and simplifying the hardware configuration. There is an advantage to losing.

Claims (10)

A pixel portion including a plurality of scan lines, a plurality of data lines, and a plurality of pixels electrically connected to the plurality of scan lines and the plurality of data lines; A power supply unit supplying power to the pixel unit through a power line; A current measuring unit dividing the pixel unit into a first region and a second region and measuring a current flowing through each pixel included in the second region; A data corrector configured to correct video data corresponding to the second area according to a current value measured by the current measurer; A data driver for transmitting a data signal corresponding to the corrected video data transmitted from the data corrector to the plurality of data lines; And And a scan driver for applying a scan signal to the plurality of scan lines. The method of claim 1, The second area is a light emitting display device in which an icon is formed while driving a still image. The method of claim 1, The second area is a light emitting display device which is a central portion of the pixel portion when driving a video. The method of claim 1, The data signal is divided into a first data signal and a second data signal according to an image display period and a current measurement period, wherein the first data signal is used when the pixel unit displays an image corresponding to the externally input video data. A light emitting display device which is an output data signal. The method of claim 4, wherein The second data signal includes a black gray voltage and a display gray voltage, and the display gray voltage is transmitted only to the second region. The method of claim 5, In the second region, the display gray voltage is transmitted to one row of a plurality of pixel rows during one frame, and the black gray voltage is transmitted to the pixels included in the remaining rows. The display gray voltage is sequentially transmitted to each row of the pixel unit. The method of claim 6, The current measuring unit is connected to each of a plurality of first power lines. The method of claim 5, In the second region, one pixel is selected during one frame to transmit the display gray voltage, and the black gray voltage is transmitted to the remaining pixels. The display gray voltage is sequentially transmitted to each pixel of the pixel unit. The method of claim 8, The current measuring unit is connected to a second power line. A light emitting display device control method comprising a pixel that emits light by a current corresponding to a data signal, (a) measuring a current flowing in a predetermined region of the plurality of regions of the pixel portion; (b) comparing a deviation between the current value measured in step (a) and a reference current value to determine a correction range, and correcting video data corresponding to the correction range; And and (c) transferring the corrected video data to the data driver.

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