KR101126348B1 - Oled - Google Patents

Abstract

The present invention relates to a line load compensation device and a compensation method of an organic light emitting display device for preventing degradation due to the line load of a data line generated in a large organic light emitting display device.

The present invention provides a line load correction unit for correcting a received image signal according to a luminance value according to a line load of a data line, and converts a data pulse for inputting the corrected image signal to a data line of an organic light emitting diode. A line load compensation device of an organic light emitting display device having a data driver applied to a data line of an element is provided.

Accordingly, the data signal value is corrected without changing the panel structure or the process conditions of the organic light emitting display device, thereby preventing deterioration of image quality due to line load.

Description

Line load compensation device and compensation method of organic light emitting display device

1 is a schematic plan view of a typical active matrix organic light emitting display device.

2 is an equivalent circuit diagram of the pixel circuit of FIG.

3 is a block diagram of a line load compensation device of an organic light emitting display device according to an embodiment of the present invention;

4 is a conceptual diagram illustrating luminance measurement in a data line of an organic light emitting display device;

5 is a flowchart illustrating a line load compensation method of an organic light emitting display device according to an embodiment of the present invention.

The present invention relates to a line load compensation device and a compensation method of an organic light emitting display device for preventing degradation due to line load of data lines generated in a large organic light emitting panel.

An organic light emitting device (OLED) is a self-light emitting device that emits a fluorescent material by recombination of electrons and holes. The organic light emitting display device using the same is faster than the passive light emitting device requiring a separate light source, such as a liquid crystal display device, the response speed is fast, the DC driving voltage is low and ultra-thin film is possible to be applied to the wall-mounted or portable.

Such an organic light emitting diode is divided into a passive matrix organic light emitting diode (PMOLED) and an active matrix organic light emitting diode (AMOLED) using TFTs as a method of driving an OLED light emitting cell. Can be. A simple matrix type organic light emitting diode (PMOLED) is formed so that an anode and a cathode are orthogonal, and a line is selected and driven, whereas an active matrix type organic light emitting diode (AMOLED) connects a TFT and a capacitor to each ITO pixel electrode to form a capacitor. It is a driving method to maintain the voltage by the capacitance.

1 is a schematic plan view of a typical active matrix organic light emitting display device.

Referring to FIG. 1, a general active matrix type organic light emitting display device has a plurality of pixel circuits 11 formed in an OLED panel 10. The OLED panel 10 is electrically connected to the scan driver 12 and the data driver 14.

The scan driver 12 sequentially outputs the selection signals through the scan lines S1, S2, S3, S4 ..... Sn, and the data driver 14 outputs the data lines D1, D2, D3 ... Dn. A data voltage representing an image signal is outputted through < RTI ID = 0.0 > 1, < / RTI >

That is, the OLED panel 10 is branched from the data driver 14 to a plurality of data lines D1, D2, D3,..., Dn and branched from the scan driver 12 to select images. A plurality of scanning lines S1, S2, S3, ..., Sn for transmitting? Are arranged so as to cross each other, and a pixel circuit 11 is formed at each intersection point of the scanning line and the data line.

FIG. 2 is an equivalent circuit diagram of the pixel circuit of FIG. 1.

Referring to FIG. 2, in the pixel circuit 11 of the organic light emitting display device, an image signal is transmitted to a data line Dn branched from the data driver 14, and a scan line Sn branched from the scan driver 12. The selection signal is transmitted to The second thin film transistor M2 transfers data to the capacitor Cst according to the selection signal of the scan line Sn, and the capacitor Cst stores and stores the applied data. The first thin film transistor M1 supplies the current from the power supply line Vdd to the organic light emitting diode OLED according to the data applied to the capacitor Cst, thereby emitting the organic light emitting diode OLED.

The operation of the pixel circuit 11 of the organic light emitting display device described above will be described in detail. When the second thin film transistor M2 is turned on by a selection signal applied to the gate of the first thin film transistor M1, The data voltage Vdata is applied to the gate of the first thin film transistor M1 through the data line Vdata. In addition, a current flows through the first thin film transistor M1 to the organic light emitting diode OLED in response to the data voltage Vdata applied to the gate, thereby emitting light.

At this time, the voltage Vgs_n between the source and gate of the first thin film transistor M1 becomes the difference between the voltage Vdd of the power line and the data voltage Vn transferred through the second thin film transistor M2, and the first thin film transistor ( M1) supplies a current corresponding to the square of the difference between the voltage between the source-gate and the threshold voltage Vth of the transistor, to the OLED. This may be expressed as Equation 1 below.

I _OLED = β (Vgs_n-Vth) ²

Here, I _OLED is a current flowing through the organic light emitting diode, Vgs_n is a voltage between the source and the gate of the transistor M1, Vth is a threshold voltage of the first thin film transistor M1, and β is a constant value. Where Vgs_n is Vdd-Vn.

As shown in Equation 1, according to the pixel circuit 11 shown in FIG. 2, the current I _OLED corresponding to the applied data voltage Vn is supplied to the organic light emitting diode OLED, and the supplied current. In response to this, the organic light emitting diode OLED emits light.

On the other hand, each power line voltage Vdd varies depending on the number of turned-on first thin film transistors M1, so that a voltage difference occurs between the pixels connected to the power lines, and even if the pixel voltages are the same, due to unevenness in the manufacturing process. Due to variations in the threshold voltage (Vth) of the TFT, the amount of current supplied to the organic light emitting diode OLED is changed, so that the emission luminance is changed.

In particular, when the panel of the organic light emitting display device becomes large, the line resistance of the scan line and the data line increases, and thus the gate voltage decreases toward the end of the line, thereby decreasing luminance. That is, there is a problem in that the shape of the panel deteriorates vertically due to a decrease in luminance of pixels near the end of the scan line or the data line. In this way, when the load increases, the line resistance is increased to reduce the luminance of the pixel.

In order to reduce the line load, a method of controlling Vgs by differentially applying line material or resistance characteristics according to line length in order to reduce line resistance during thin film transistor or electrode line processing has been proposed. However, in this method, the larger the area of the organic light emitting display device is, the more the resistance loss that needs to be compensated for in the process of the thin film transistor or the electrode line becomes larger. There was a problem in that, the number of processes.

In order to solve the above problems, the present invention provides a line load compensation of the organic light emitting display device that can prevent the degradation of the image quality due to the line load without changing the panel structure or the process conditions of the organic light emitting display device It is an object of the present invention to provide an apparatus and a method of compensating the same.

In order to achieve the above object, the present invention provides a line load correction unit for correcting the received image signal according to the luminance value according to the line load of the data line, and input the corrected image signal to the data line of the organic light emitting device. A line load compensation device for an organic light emitting display device having a data driver for converting data pulses and applying them to data lines of an organic light emitting device.

In this case, the compensation coefficient to be subtracted from the luminance value measured by the line load correction unit may be "a measured luminance value / minimum luminance value".

In addition, the gamma correction unit may further have a gamma correction unit for correcting the image signal before the image signal is corrected by the line load correction unit.

The apparatus may further include a half toning unit for half-toning the image signal corrected by the line load correction unit by using error diffusion or dithering and inputting the image signal to the data driver.

In another aspect, the present invention, the video signal receiving step of receiving a video signal, a line load correction step of correcting the received video signal according to the luminance value according to the line load of the data line, and the corrected video signal A line load compensation method of an organic light emitting display device having a data input step of converting a data pulse to be input to a data line of an electroluminescent device and applying the data pulse to a data line of the organic light emitting device is provided.

At this time, in the line load correction step, the compensation coefficient to be subtracted from the measured luminance value may be "a measured luminance value / minimum luminance value".

In addition, before the image signal is corrected in the line load correction step, a gamma correction step of gamma correction of the image signal may be further included.

In addition, the data input step may further include a half toning step of inputting data by half-toning the image signal corrected in the line load correction step by using error diffusion or dithering.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

3 is a block diagram of a line load compensation device of an organic light emitting display device according to an embodiment of the present invention, and FIG. 4 is a conceptual diagram of luminance measurement in a data line of the organic light emitting display device.

Referring to FIG. 3, the line load compensating device 20 of the organic light emitting display device according to an embodiment of the present invention may include a luminance measuring unit 22, a gamma correction unit 24, a line load compensating unit 26, The half toning unit 28, the memory unit 30, the data alignment unit 32, and the data driver 34 are provided.

3 and 4, the luminance measuring unit 22 transmits a data signal A _{1 to a} data line D ₁ , D ₂ , D ₃ ..., D _N-2 , D _N-1 , D _N. , A ₂ , A ₃ .... A _N-2 , A _N-1 , A _N ) or actual luminances when a data voltage pulse is applied (La ₁ , La ₂ , La ₃ .... L _{N- 2} , L _N-1 , L _N ) is measured. Due to the line load of the scan line, the actual measured luminance values are reduced in the order of La ₁ > La ₂ > La ₃ > ... L _N-2 > L _N-1 > L _N.

The gamma correction unit 24 gamma corrects the data signal value input to the data line. That is, gamma correction is to exponentiate the data signal value as in Equation (2).

y = α (x / 255) ^2.2

Where y is the gamma correction value of the data signal value, x is the data signal value, 255 is the highest data signal value, and α is a constant.

The line load correction unit 26 calculates a compensation coefficient by using the luminance values of the data signals A ₁ , A ₂ , A ₃ ... A _N-2 , A _N-1 , A _N. The data signal value is corrected using the compensation coefficient.

That is, the line load correction unit 26 converts the data signal value as shown in Equation 3 below.

y = {α-β} (x / 255) ^2.2

y, x, 255, and α are the same as Equation 2, and β is the compensation coefficient.

This compensation coefficient β is obtained using the measured luminance value. That is, the compensation coefficient β of each signal data is actual luminances La ₁ , La ₂ , La ₃ .... L _N-2 , L _N-1 , L _N measured by the luminance measuring unit 22. the linearly or non-linearly proportional to the value obtained by dividing the minimum luminance value of L _N. This compensation coefficient β is determined linearly or nonlinearly according to the constant α used in equations (2) and (3).

The half toning unit 28 half-tons the data signal corrected by the line load correction unit 26 using the memory unit 30 by at least one of error diffusion or dithering. do. That is, the half toning unit 28 halftons a decimal value of a data signal value corrected by Equation 3 consisting of an integer value and a decimal value, for example, 2.6 (2 is an integer value and 0.6 is a decimal value). Reflected in the constant of the next data signal value.

For example, when three data signal values corrected by Equation 3 are 3.2, 2.9, and 2.6, the first data signal value takes an integer value 3 and the decimal value 0.2 is passed to the next data signal value. The next data signal value takes the passed decimal value and takes the integer value 3 out of 2.9 + 0.2 = 3.1 and passes the decimal value to the next data signal value. In this manner, since the decimal value of the previous data signal value is passed to the next data signal value, the decimal value of the data signal can be reflected in the next data signal value without discarding it.

Since the half toning unit 28 half-tons the corrected data signal value, the data distortion can be prevented from occurring.

The data sorter 32 arranges the data in time according to the panel of the organic light emitting display device.

Finally, the data driving section 34 receives the time of collation by the collation part 32, the data lines _{(D 1, D 2, D} 3 .... D N-2, D N-1, D _N ) and finally corrected data values (A ₁ ^' , A ₂ ^' , A ₃ ^' .... A _N-2 ^' , A _N-1 ^' , A _N ^' ) The electroluminescent element is driven.

5 is a flowchart illustrating a line load compensation method of an organic light emitting display device according to an embodiment of the present invention.

3 and 5, in the line load compensation method of an organic light emitting display device according to an embodiment of the present invention, first, the actual luminance according to the data signal is measured, and then the gamma data signal is gamma-expressed using Equation 3 below. The line load correction is performed using the correction and the compensation coefficient according to the luminance value (S10 to S12).

Next, half-toning takes only an integer value among the corrected data values and passes the remaining decimal value to the next data value, and then aligns the data in time to apply a data driving pulse suitable for the data line to the data line. Emit light (S13 to S15).

As described above, since the data signal is corrected using the line load compensation method of the organic light emitting display device according to the exemplary embodiment of the present invention, the organic light emitting panel of the organic light emitting panel is improved without improving the data structure or the panel structure or manufacturing process of the thin film transistor. It is possible to prevent the line load caused by the large area.

As mentioned above, although an embodiment of the present invention has been described with reference to the drawings, the present invention is not limited thereto.

In the above embodiment, it has been described that gamma correction is performed before the data signal value is line loaded, but since the gamma correction part 24 does not exist, the line load compensation part 26 directly loads the data signal value without gamma correction. You can also correct it. That is, the data signal value may be line loaded using the compensation coefficient obtained by using the luminance value actually measured without indexing the data signal value. For example, the data signal values are A ₁ , A ₂ , A ₃ .... A _N-2 , A _N-1 , A _N , and the measured luminance values are La ₁ , La ₂ , La ₃ . ... L _N-2 , L _N-1 , L _N , the line load corrected data signal values (A ₁ ^' , A ₂ ^' , A ₃ ^' .... A _N-2 ^' , A _N-1 ^' , A _N ^' ) are luminance values of actual measurement of data signal values (A ₁ , A ₂ , A ₃ .... A _N-2 , A _N-1 , A _N ) as shown in Equation 4. The values La ₁ , La ₂ , La ₃ ... L _N-2 , L _N-1 , L _N may be obtained by subtracting the values by the minimum luminance value L _N.

A _K ^' = A _K -L _K / L _N

In Equation 4, K is 1 to n, and L _N is the measured minimum luminance value, which is the luminance value of the last data line.

In addition, in the above embodiment, it has been described that the line load correction unit 26 half-tons the half-toning unit 28 to prevent data distortion after the line load correction of the data signal value. The data signal value may be input to the data driver 32 without halftoning.

In the above embodiment, the compensation coefficient is obtained by using the luminance values actually measured by the line load correction unit 26, and the data signal value is corrected using the compensation coefficient. However, the present invention is not limited thereto. .

As described above, it is to be understood that the technical structure of the present invention can be embodied in other specific forms without departing from the spirit and essential characteristics of the present invention.

Therefore, the embodiments described above are to be understood as illustrative and not restrictive in all respects, and the scope of the present invention is indicated by the following claims rather than the detailed description, and the meaning and scope of the claims and All changes or modifications derived from the equivalent concept should be interpreted as being included in the scope of the present invention.

As described above, the present invention corrects the data signal value without changing the panel structure or the process conditions of the organic light emitting display device, thereby preventing deterioration of image quality due to line load.

Accordingly, the present invention has an effect of making the organic light emitting panel large in area.

Claims (9)

A luminance measuring unit for measuring actual luminance of a data signal applied to a data line to derive a luminance value according to a line load; A line load correction unit obtaining a compensation coefficient using the luminance value and correcting the received image signal using the compensation coefficient; And And a data driver converting the corrected image signal into a data pulse to be input to a data line of the organic light emitting diode and applying the data signal to a data line of the organic light emitting diode. And a compensation coefficient to be subtracted by the line load correction unit according to the luminance value is a "measured luminance value / minimum luminance value". delete The method of claim 1, And a gamma compensator for gamma correcting the video signal before the video signal is corrected by a line load corrector. The method of claim 1, And a half toning unit for half-toning the corrected image signal by one of error diffusion or dithering and inputting the corrected image signal to the data driver. delete delete delete delete The method of claim 4, wherein And the data driver further comprises a data alignment unit for aligning the half-toned data signal in time with a panel of the organic light emitting display device.

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