KR20170081090A - Organic Light Emitting diode Display and Driving Method thereof - Google Patents

Abstract

An organic light emitting diode display apparatus according to the present invention includes a display panel, a gamma compensation operation unit, and a data driver. Pixels including organic light emitting diodes are arranged on a display panel. The gamma compensation operation unit receives input image data from the host and outputs voltage data indicating a voltage value corresponding to the gradation of the input image data. The data driver generates a data voltage indicated by the voltage data, and supplies the data voltage to the data line. The gamma compensation operation unit calculates the magnitude of the data voltage by substituting the grayscale value of the input image data into the grayscale-voltage relation expressing the relationship between the grayscale value of the input image data and the data voltage, and outputs the voltage data directly indicating the magnitude of the data voltage .

Description

[0001] The present invention relates to an organic light emitting diode (OLED) display device and a method of driving the same,

The present invention relates to an organic light emitting diode display and a driving method thereof.

2. Description of the Related Art Flat panel displays (FPDs) are widely used not only for monitors of desktop computers but also for portable computers such as notebook computers and PDAs, as well as mobile phone terminals, because they are advantageous in downsizing and light weight. Such a flat panel display device includes a liquid crystal display (LCD) (LCD), a plasma display panel (PDP), a field emission display (FED) and an organic light emitting diode display (OLED).

Among these organic light emitting diode display devices, the organic light emitting diode display device has a high response speed, high luminance efficiency, and a large viewing angle. In general, an organic light emitting diode display device applies a data voltage to a gate electrode of a driving transistor by using a switching element transistor turned on by a scan signal, and by using the data voltage supplied to the driving transistor, . That is, the current supplied to the organic light emitting diode is controlled by the data voltage applied to the gate electrode of the driving transistor.

Ideally, all pixels of the display panel respond to the same data voltage to represent the same gray level. However, a process error may occur in the process of manufacturing the display panel, or characteristic deviations of the pixels may occur after the display panel fabrication is completed. Accordingly, even if the pixels receive the same data voltage, there is a problem that the luminance difference occurs and the image quality is distorted.

The present invention provides an organic light emitting diode display device and a method of driving the same, which can effectively compensate image quality deviations of pixels.

An organic light emitting diode display apparatus according to the present invention includes a display panel, a gamma compensation operation unit, and a data driver. Pixels including organic light emitting diodes are arranged on a display panel. The gamma compensation operation unit receives input image data from the host and outputs voltage data indicating a voltage value corresponding to the gradation of the input image data. The data driver generates a data voltage indicated by the voltage data, and supplies the data voltage to the data line. The gamma compensation operation unit calculates the magnitude of the data voltage by substituting the grayscale value of the input image data into the grayscale-voltage relation expressing the relationship between the grayscale value of the input image data and the data voltage, and outputs the voltage data directly indicating the magnitude of the data voltage .

Since the present invention stores only the gamma parameters in the memory in order to compensate the image data, the image data can be compensated by using a small amount of information. Therefore, even when the image data of each pixel is individually compensated, it is not necessary to store a large amount of information in the memory.

The present invention allows the pixels to emit light at a brightness corresponding to a desired input image data, without performing the conventional deterioration compensation, external compensation, and optical compensation separately.

In addition, since the gamma parameter of the present invention is calculated using the luminance-voltage relation based on the gamma curve, it is not influenced by the gamma curve.

1 is a view showing an organic light emitting diode display device according to the present invention.
2 is a diagram showing a pixel structure of the present invention;
3 is a flow chart showing a method of calculating a gamma parameter according to the present invention;
4 is a schematic diagram showing a process of calculating a voltage-luminance relation.
5 is a schematic diagram showing a method of calculating a voltage-gradation relation.
6 is a diagram showing an example of data in a line unit;

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Like reference numerals throughout the specification denote substantially identical components. In the following description, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 1 is a view showing a configuration of an organic light emitting diode display device according to the present invention, and FIG. 2 is a diagram showing a pixel structure of the present invention. The organic light emitting diode display device of the present invention will be described with reference to FIGS. 1 and 2. FIG.

The organic light emitting diode display device according to the present invention includes a display panel 10, a timing controller 11, a data driver 12, and a gate driver 13 in which pixels P are arranged in a matrix.

The display panel 10 includes a plurality of pixels P and is for displaying an image based on the gradation displayed by each of the pixels P. [ A plurality of pixels P are arranged in a matrix form in the display panel 10 by arranging a plurality of pixels on the first to m-th pixel lines at regular intervals.

The data lines DL correspond to n (n is a positive integer) pixel columns, and include n data voltage supply lines 14A_1 to 14A_n and n reference voltage lines 14B_1 to 14B_n. The gate lines GL include m scan lines 15A_1 to 15A_m and m sense lines 15B_1 to 15B_m corresponding to m (n is a positive integer) pixel lines HL1 to HLm .

The pixels P are supplied with the high potential driving voltage ELVDD and the low potential driving voltage ELVSS from the voltage supplier 500. [ The pixels P arranged in the first column are connected to the first data voltage supply line 14A_1 and the first reference voltage line 14B_1 and the pixels P arranged in the second column are connected to the second data voltage supply line 14A_2 And the second reference voltage line 14B_2. Similarly, the pixels P arranged in the i-th column (i is a natural number of n or less) are connected to the i-th data voltage supply line 14A_i and the i-th reference voltage line 14B_i.

The pixels P arranged in the first pixel line HL1 are connected to the first scan line 15A_1 and the first sense line 15B_1 and the pixels P arranged in the second pixel line HL2 are connected to the 2 scan line 15A_2 and the second sense line 15B_2. Similarly, the pixels P arranged in the pixel line HLj of j (j is a natural number of m or less) connect to the j-th scan line 15A_j and the j-th sense line 15B_j.

The timing controller 11 controls the driving timings of the data driver 12 and the gate driver 13. The timing controller 11 controls the operation timing of the data driver 12 based on the timing signals such as the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the dot clock signal DCLK and the data enable signal DE And a gate control signal GDC for controlling the operation timing of the gate driver 13. The gate control signal GDC for controlling the operation timing of the gate driver 13,

The timing controller 11 generates voltage data MDATA compensating the input image data DATA by using the gamma parameter Gpara stored in the memory 16. [ The gamma parameter Gpara refers to a coefficient of a relational expression indicating a correspondence relationship between the gradation and the voltage and the relation between the gradation and the voltage of the display panel 10 is obtained by measuring the light emission luminance of the display panel 10 according to the voltage . Details of the gamma parameter (Gpara) will be described later.

The data driver 12 converts the voltage data MDATA input from the timing controller 11 into an analog data voltage based on the data control signal DDC and supplies the analog data voltage to the data lines DL. The data driver 12 also includes an analog-to-digital converter (ADC) for converting a sensing voltage for sensing a threshold voltage Vth of the organic light emitting diode OLED fed back from each pixel P into sensing data, Converter (ADC).

The data driver 12 supplies a predetermined data voltage to the pixels P and drives the pixels P through the reference voltage lines 14B_1 to 14B_m when driving the threshold voltage compensation of the organic light emitting diode OLED. The input sensing voltages may be converted into digital values and supplied to the timing controller 11. [

The data driver 12 is connected to the pixel P via the data voltage supply line 14A and the reference voltage line 14B.

The gate driver 13 generates the scan signal SCAN and the sense signal SENSE using the gate control signal GDC supplied from the timing controller 11. [ The gate control signal GDC includes a gate start pulse GSP indicating a start scan line at which a scan is started, a gate shift clock GSC for sequentially shifting a gate start pulse GSP, And a gate output enable (GOE) for indicating the output of the gate driver.

As shown in FIG. 2, each of the pixels P includes an organic light emitting diode OLED, a driving transistor DT, a scan transistor ST1, a sense transistor ST2, and a storage capacitor Cst.

In the organic light emitting diode OLED, the anode electrode is connected to the second node N2, and the cathode electrode is connected to the low potential power source ELVSS.

The driving transistor DT controls the current Ioled flowing in the organic light emitting diode OLED according to the gate-source voltage Vgs. The driving transistor DT has a gate electrode connected to the first node N1, a drain electrode connected to the high potential power supply ELVDD, and a source electrode connected to the second node N2.

The storage capacitor Cst is connected between the first node N1 and the second node N2.

The scan transistor ST1 is switched in accordance with the scan signal SCAN and supplies a voltage data voltage MVdata compensated for a data voltage or a threshold voltage change of the organic light emitting diode OLED to the data voltage supply line 14A, (N1). The scan transistor ST1 has a gate electrode connected to the scan line 15A, a drain electrode connected to the data voltage supply line 14A, and a source electrode connected to the first node N1.

The sense transistor ST2 is switched according to the sense signal SENSE and applies the initialization voltage Vref supplied from the reference line 14B to the second node N2. The sense transistor ST2 is also switched according to the sense signal SENSE to provide the threshold voltage sensing voltage of the organic light emitting diode OLED to the ADC. The gate electrode of the sense transistor ST2 is connected to the second gate line 15B, the drain electrode is connected to the second node N2, and the source electrode is connected to the reference line 14B.

The pixel structure shown in FIG. 2 represents one embodiment, and the present invention can be applied to an organic light emitting diode display device having another pixel structure.

3 is a flow chart illustrating a method of computing a gamma parameter of the present invention stored in a memory. The gamma parameter Gpara refers to a parameter of a relational expression when expressing a gray level in a relation including a voltage value.

In order to calculate the gamma parameter Gpara, the luminance (L) of the pixels P corresponding to the data voltage is measured to calculate the voltage-luminance relation.

The voltage-luminance relation is an expression representing the luminance change with the voltage change. The voltage in the voltage-luminance relationship refers to the data voltage input to the gate electrode of the driving transistor DT shown in Fig. The luminance in the voltage-luminance relation represents the light emission luminance of the pixel P when the data voltage is applied to each pixel P to cause the organic light emitting diode OLED to emit light.

The light emission luminances of the pixels P are obtained through an image of the display panel 10 using a charge coupled device camera (CCD). The light emission luminance is obtained in units of pixels (P).

For example, the luminance change of the first pixel P1 and the second pixel P2 according to the voltage V in the display panel 10 may be as shown in FIG.

Referring to FIG. 4, the first pixel P1 emits light at a first luminance L1 corresponding to a first voltage V1 and emits light at a second luminance L2 corresponding to a second voltage V2 . The second pixel P emits light at the first luminance L1 'corresponding to the first voltage V1 and emits at the second luminance L2' corresponding to the second voltage V2.

After obtaining the light emission luminances corresponding to the plurality of voltages as described above, the luminance corresponding to the voltage levels not measured is interpolated by the pre-regression method to calculate the luminance relation corresponding to the mode voltage.

The voltage-luminance relation can be expressed in the form of an exponential function as shown in Equation (1) below.

In this case, VpreR means a gamma value and may be greater than 1 and smaller than 2.5, for example, 2.2. (S301)

The voltage-luminance relationship can be obtained separately for a plurality of pixels P, for example, all the pixels P. [

The inverse function of the expression (1) expressing the luminance by the voltage is obtained and the voltage is represented by the luminance. That is, the voltage can be expressed by a relational expression with A and B being the parameter Gpara (hereinafter, gamma parameter). Then, the inverse function of Equation (1) is matched with the relation between the preset gradation and the luminance. This will be described with reference to FIG.

FIG. 5A is a graph showing the relationship between the gradation and the luminance, and FIG. 5B is a graph showing an inverse function of the expression (1). That is, the luminance-voltage relation represented as shown in FIG. 5 (b) is matched with the luminance item of the gradation-luminance relation expressed as shown in FIG. 5 (a) Voltage relationship expressing the relationship between the voltages can be obtained. That is, in FIG. 5C, the gray level value is represented by a relational expression including the gamma parameter Gpara in Equation (1). The memory 16 stores the gradation-voltage relation gamma parameter Gpara expressed as (c) in FIG. In particular, the memory 16 may store the gamma parameters Gpara of all the pixels P. [ For example, the memory 16 may store gamma parameters of Gpara [1,1] to Gpara [n, m]. Here, Gpara [i, j] refers to the gamma parameter of the pixel located in the jth column of the i-th row. (S302.S303)

Then, the gamma compensation operation unit 100 performs an algorithm of the gradation-voltage relationship expressed as (c) in FIG.

A gamma compensation method of the gamma compensation operation unit 100 will be described below.

The gamma compensation operation unit 100 receives input image data (DATA) on a line-by-line basis from the host 5. The input image data (DATA) may be a grayscale value having a range from 0 to 255. [

6 is a diagram showing input image data (DATA) of the i-th horizontal line. 6, the input image data DATA of the i-th line is input to the pixel P [i, 1] located in the n-th column from the gray level value DATA [i, 1] of the pixel P [i, [i, n]) of the gray level data [i, n].

The gamma compensation operation unit 100 calculates the voltage data MDATA by using the gray-scale voltage relation expressed as (c) in FIG. 5 and the gamma parameter Gpara stored in the memory 16. The voltage data MDATA is digital data representing a voltage value.

The gamma compensation operation unit 100 substitutes the gray level value DATA [i, 1] of the first pixel P [i, 1] of the i-th row into the gray- ). At this time, the gamma compensation operation unit 100 uses the gamma parameter Gpara [i, 1] of the first pixel P [i, 1] of the i-th row stored in the memory 16 to calculate voltage data MDATA [i , 1]).

In this way, the gamma compensation operation unit 100 calculates the voltage data MDATA [i, 1] to MDATA [i, n] of the first pixel P [i, ).

The voltage data MDATA calculated by the gamma compensation calculation unit 100 is transferred to the data driver 12 and the data driver 12 generates an analog data voltage of a magnitude indicated by the voltage data MDATA and supplies it to the data line DL .

Since the present invention stores only the gamma parameter Gpara in the memory 16 in order to compensate the image data DATA, the image data DATA can be compensated using a small amount of information. Therefore, the present invention does not need to store a large amount of information in the memory 16 even when the image data (DATA) of each pixel P is individually compensated.

In addition, since the present invention uses a gray-to-voltage relationship that reflects the luminance emitted based on the data voltage supplied to each pixel P, there is no need to perform additional compensation in the process of displaying an image by the pixels P .

In general, compensation methods for improving image quality include degradation compensation, external compensation, and optical compensation. Compensation for deterioration is a process for compensating for a change in luminance according to deterioration of the organic light emitting diode (OLED). The external compensation is a process for compensating for the luminance change due to the threshold voltage deviation of the driving transistor DT of the pixel P and the optical compensation is a process for compensating the luminance unevenness region due to the stain or the like of the display panel 10. [ These conventional pixel-image compensation methods have to be individually compensated for each cause.

On the other hand, the voltage data MDATA calculated by the gamma compensation associative part of the present invention can be used for the pixel P because the pixel P reflects the luminance actually emitted at a specific data voltage, And so on. Accordingly, the present invention allows the pixels P to emit light at a brightness corresponding to a desired input image data (DATA) without performing the conventional deterioration compensation, external compensation, and optical compensation separately.

Also, in the related art, there is a problem that the accuracy is lowered due to the deviation of the gamma curve in the process of compensating the smear of the display panel 10. This is because the gamma curve can be set using a different gamma value for each panel, because the smoothing compensation method simply compensates for the gradation of the image data in order to improve the luminance unevenness of the display panel 10. [

On the other hand, the gamma parameter Gpara of the present invention is not influenced by the gamma curve since it is calculated using the luminance-voltage relation based on the gamma curve.

The gamma compensation operation unit 100 of the present invention can be applied to the display panel 10 having a special array structure without fail. For example, in order to compensate the color uniformity through optical compensation in a WRGB type display panel, a data voltage for displaying a specific color is written in each pixel P, and the distribution of the stains is confirmed by visual observation or camera photographing. However, the WRGB type display panel differs from the general RGB type display panel in the data writing method of pixels. For example, the WRGB method mixes colors such as RB or GB in addition to the W pixel in order to express full white. Thus, it is difficult to grasp whether the unevenness occurring on the display panel 10 when displaying full white is due to a data voltage displaying full white or a data voltage displaying a specific color.

On the other hand, since the luminance-voltage relation is calculated on a pixel-by-pixel basis, the present invention can also calculate and reflect the distribution of stains on a pixel-by-pixel basis, thereby performing optical compensation functions such as image compensation more efficiently.

In the embodiment of the present invention, gamma parameters are calculated on a pixel-by-pixel basis. As described above, since the gamma parameter corresponds to a parameter and is small-sized data, the memory can store the gamma parameter of all the pixels. Of course, in order to reduce the memory capacity, gamma parameters may be stored for pixels of a predetermined interval, and parameters generated using spatial interpolation may be applied to pixels whose gamma parameters do not match.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Therefore, 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.

10: Display panel 11: Timing controller
12: Data driver 13: Gate driver
14: data line section 15: gate line section
100: gamma compensation operation section

Claims (7)

A display panel in which pixels including an organic light emitting diode are arranged;
A gamma compensation operation unit receiving input image data from a host and outputting voltage data indicating a voltage value corresponding to a gray level of the input image data; And
And a data driver for generating a data voltage indicated by the voltage data and supplying the data voltage to the data line,
The gamma compensation calculation unit
The gray level value of the input video data is substituted into the gray level-voltage relation expressing the relation between the gray level value of the input video data and the data voltage to calculate the size of the data voltage, and voltage data for directly indicating the size of the data voltage is generated The organic light emitting diode display device. The method according to claim 1,
The gray-to-voltage relationship
A voltage-luminance relation is calculated by measuring the luminance of the pixels corresponding to the data voltages of a plurality of voltage levels,
And calculating the voltage-luminance relation by matching the preset gray-scale luminance relation with the voltage-luminance relation. The method according to claim 1,
The gradation-voltage relation expresses the gradation as a function of the voltage with the gamma parameter as a parameter,
Wherein the gamma parameter is stored in a memory. The method of claim 3,
Wherein the gamma parameter is set in pixel units,
Wherein the gamma compensation operation unit generates the voltage data using the gamma parameter for a predetermined pixel. 3. The method of claim 2,
Wherein the voltage-luminance relationship is calculated using a gamma curve having a gamma value of greater than 1 and less than 2.5. 3. The method of claim 2,
Wherein the voltage-luminance relationship is calculated based on an exponential function. A method of driving a display device in which a plurality of pixels including organic light emitting diodes are arranged,
Receiving input image data from a host;
Voltage relationship expressing the relation between the gray-level value of the input video data and the data voltage is previously stored, the gray-level value of the input video data is substituted into the gray-scale voltage relation to calculate the data voltage magnitude, Generating voltage data that directly indicates the magnitude of the voltage; And
Generating a data voltage indicated by the voltage data, and supplying the data voltage to the pixels.

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