KR20120033401A - Light emitting display device and method for driving the same - Google Patents

Abstract

PURPOSE: A light emitting display apparatus and a driving method thereof are provided to reduce usage capacity of a memory by eliminating a part of bits of image data. CONSTITUTION: A quantization part(QT) eliminates a part of bits which form image data of an n-th frame outputted from a system. The n is a natural number greater than one. An addition/renewal unit(ANU) creates addition image data by adding image data of a previous frame which is stored in a memory and the image data of the n-th frame in which partial bits are eliminated. The addition/renewal unit renews the image data of the previous frame to the addition image data by storing the addition image data in the memory. The image data of the previous frame is accumulated image data in which image data of a first frame to an (n-1)th frame are added.

Description

LIGHT EMITTING DISPLAY DEVICE AND METHOD FOR DRIVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light emitting display device, and more particularly, to a light emitting display device and a driving method thereof capable of reducing the use capacity of a memory.

As the driving time of the light emitting display device increases, the deterioration accelerates and the light emitting ability thereof decreases. Conventionally, in order to solve such a problem, image data applied to a light emitting device is accumulated in a memory every frame period, and the driving time of the light emitting device is converted based on the accumulated size of the image data, and based on the driving time. By modulating the size of the image data supplied to the light emitting device, the reduced light emitting ability of the light emitting device is compensated.

However, conventionally, since image data is continuously accumulated in this memory every frame period, a problem arises that the capacity of the accumulated image data is excessively increased after a predetermined time and the capacity of the memory is exceeded. In addition, there is a problem that the capacity of the memory must be considerably large in order to handle such a large amount of data.

For example, in the case of a Full HD display driven at a frequency of 60 Hz, 60 images of 1920 * 1080 are accumulated in memory every second. This is to accumulate a large amount of image data of 120MB per second in the memory.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and the present invention provides a light emitting display device capable of quantizing image data to reduce its size, and storing the reduced image data in the memory, thereby significantly reducing the use capacity of the memory. And its driving method.

A driving method of a light emitting display device according to the present invention for achieving the above object comprises the steps of sequentially outputting the image data for supplying a plurality of light emitting elements; Removing some bits of bits constituting the image data of the nth frame (n is a natural number of two or more): adding the image data of the nth frame from which the some bits are removed and the image data of the previous frame stored in the memory Generating additive image data; Storing the added image data in the memory to update the image data of the previous frame with the added image data; The image data of the previous frame may be accumulated image data obtained by adding all the image data of the first frame from which some bits are removed to the image data of the n-1-1 frame from which some bits are removed.

Reading the added image data from the memory; And generating modulated image data of the nth frame by modulating the image data of the intact nth frame in which the some bits are not removed based on the added image data read from the memory.

The generating of the modulated image data of the nth frame may include preparing a gain lookup table having gain values having different values according to cumulative gray scale values; Selecting a gain value corresponding to a cumulative gradation value of the added image data read from the memory; And generating modulated image data of the nth frame by calculating image data of an intact nth frame in which the selected gain value and the some bits are not removed.

And gamma correcting the modulated image data of the nth frame.

Inverse gamma correction of the sequentially output image data; And gamma correcting the modulated image data of the nth frame.

The image data are 8 bits of data; The some bits may be lower 3 bits.

In addition, a light emitting display device according to the present invention for achieving the above object, a system for sequentially outputting image data for supplying a plurality of light emitting elements; A quantization unit for removing some bits of the bits constituting the image data of the n-th frame (n is a natural number of two or more) output from the system: Image data and memory of the n-th frame from which some bits from the quantization unit are removed An add / update unit configured to add image data of a previous frame stored in the apparatus to generate added image data, store the added image data in the memory, and update the image data of the previous frame to the added image data; The image data of the previous frame may be accumulated image data obtained by adding all the image data of the first frame from which some bits are removed to the image data of the n-1-1 frame from which some bits are removed.

An image that reads the added image data from the memory and modulates the image data of the nth frame in which the partial bit is not removed based on the added image data read from the memory to generate modulated image data of the nth frame It further comprises a modulator.

The image modulator may include: a gain value selector configured to select a gain value corresponding to an accumulated gray scale value of the added image data read from the memory, from a gain lookup table; An operation unit configured to generate the modulated image data of the n-th frame by calculating the image data of the n-th frame in which the gain value selected from the gain value selector and the some bits are not removed; The gain lookup table may store gain values having different values according to cumulative gray values.

And gamma correction unit for gamma correcting the modulated image data of the nth frame.

An inverse gamma correction unit for inverse gamma correction of the sequentially output image data; And a gamma correction unit for gamma correcting the modulated image data of the nth frame.

The image data are 8 bits of data; The some bits may be lower 3 bits.

The light emitting display device and its driving method according to the present invention have the following effects.

In the present invention, rather than storing the image data in the memory as it is, as described above, by removing some bits of the image data, the size is reduced, and the size of the reduced image data is stored in the memory, the use capacity of the memory is considerably increased. Can be reduced. Therefore, when using the memory of the same capacity, the present invention can use the memory for more time than conventional.

1 is a view showing a light emitting display device according to an embodiment of the present invention;
2 is a diagram illustrating a detailed configuration of a pixel of FIG. 1;
3 is a detailed configuration diagram of a data correction unit according to a first embodiment of the present invention;
4 is a diagram showing a bit structure of image data;
5 illustrates a gain lookup table.
6 is a detailed configuration diagram of a data correction unit according to a second embodiment of the present invention.

1 is a diagram illustrating a light emitting display device according to an exemplary embodiment of the present invention, and FIG. 2 is a diagram illustrating a detailed configuration of a pixel of FIG. 1.

As illustrated in FIG. 1, a light emitting display device according to an exemplary embodiment of the present invention includes a display unit DSP, a system SYS, a gate driver GD, a data driver DD, a timing controller TC, and a data beam. Includes government (DA).

The display unit DSP includes a plurality of pixels PXL, a plurality of gate lines GL, a plurality of data lines DL, and a plurality of pixels for transmitting the various signals necessary for displaying the images. It includes the power supply lines (PL) of. These pixels PXL are arranged in the display portion DSP in a matrix form. The pixels PXL are divided into a red pixel PXL displaying red, a green pixel PXL displaying green, and a blue pixel PXL displaying blue. As shown in FIG. 2, each pixel PXL includes a light emitting element LED and a pixel circuit PC generating a driving current for emitting the light emitting element LED. The pixel circuit PC operates in response to the scan pulse from the gate line GL. At this time, the driving current is obtained by using the analog pixel voltage from the data line DL and the driving voltage from the power supply line PL. Create The generated driving current is supplied to the light emitting device (LED) to emit light of the light emitting device (LED). The light emitting device (LED) may use an organic light emitting diode (OLED).

The system SYS outputs the vertical synchronization signal, the horizontal synchronization signal, the clock signal, and the image data through the interface circuit through a low voltage differential signaling (LVDS) transmitter of the graphic controller. The vertical / horizontal synchronization signal and the clock signal output from this system SYS are supplied to the timing controller TC. The image data sequentially output from the system SYS is corrected through the data correcting unit DA and then supplied to the timing controller TC.

The timing controller TC generates a data control signal and a gate control signal by using the horizontal synchronizing signal, the vertical synchronizing signal, and the clock signal input thereto, and supplies the data control signal and the gate control signal to the data driver DD and the gate driver GD. The data control signal includes a dot clock, a source shift clock, a source enable signal, a polarity inversion signal, and the like. The gate control signal includes a gate start pulse, a gate shift clock, a gate output enable, and the like.

The data driver DD samples the image data according to the data control signal from the timing controller TC, and then, for each horizontal period, sampling images corresponding to one horizontal line for each horizontal period (1H, 2H, ...). The data are latched and the latched image data is supplied to the data lines DL. That is, the data driver DD converts the image data from the timing controller TC into the analog pixel PXL signal using the gamma voltage input from the power generator and supplies the image data to the data lines DL.

The gate driver GD has a shift register that sequentially generates scan pulses in response to a gate start pulse from the timing controller TC, and a level for shifting the scan pulses to a voltage level suitable for driving the pixel circuit PC. It includes a shifter. The gate driver GD sequentially supplies scan pulses to the gate lines GL in response to the gate control signal.

The data corrector DA modulates the image data supplied from the system SYS according to the cumulative size of the image data supplied to the light emitting device LED.

3 is a detailed configuration diagram of a data correction unit according to a first exemplary embodiment of the present invention, and FIG. 4 is a diagram illustrating a bit configuration of image data.

As shown in FIG. 3, the data correcting unit according to the first embodiment of the present invention includes an inverse gamma correction unit (RGM), a quantization unit (QT), an add / update unit (ANU), a memory (MEM), and image modulation. Minor (IMM), gain lookup table (GLUT), and gamma correction unit (GM).

The reverse gamma correction unit RGM is sequentially supplied with image data from the system SYS. The gamma information applied to the video data is removed. Image data from which gamma information is removed has linearity with respect to luminance. In other words, the inverse gamma conversion unit RGM removes gamma information from the image data so that the image data has linearity with respect to luminance. The reason for removing gamma information from these image data is to accurately calculate quantization and addition which will be described later.

The quantization unit QT removes some bits of bits constituting image data of the nth frame (n is a natural number of two or more) output from the inverse gamma correction unit RGM. For example, as shown in FIG. 4, each of the image data output from the system through the inverse gamma correction unit (RGM) is 8 bits, and the quantizer QT removes the lower 3 bits of the 8 bits. do. By doing so, the video data output from the quantization unit QT is modulated into 5-bit digital data. Each numerical value shown in FIG. 4 represents the degree to which each bit affects the degradation of the light emitting device, and the upper five bits have the greatest influence on the degradation of the light emitting device. That is, the upper 5 bits are about 97%, which affects the degradation of the light emitting device. The number of lower bits to be removed may vary depending on the number of bits of the image data.

The adder / updater ANU adds the image data of the n-th frame from which some bits from the quantizer QT are removed and the image data of the previous frame stored in the memory MEM to generate the added image data. The added image data is stored in the memory MEM to update the image data of the previous frame with the added image data.

The image data of the previous frame stored in the memory MEM means accumulated image data obtained by adding all the image data of the first frame from which some bits are removed to the image data of the n-1 frame from which some bits are removed. That is, the memory MEM includes the same number of cells as the number of pixels. In each cell, image data supplied to the corresponding pixel is accumulated in units of frames. For example, in the first frame of the memory MEM in the fifth frame period, the image data of the first frame, the image data of the second frame, and the first frame supplied to the light emitting element of the first pixel corresponding to the first cell. A value obtained by adding up image data of three frames, image data of a fourth frame, and image data of a fifth frame is stored. The second cell of the memory MEM includes image data of a first frame, image data of a second frame, image data of a third frame, and a second frame supplied to a light emitting element of a second pixel corresponding to the second cell. A value obtained by adding up image data of four frames and image data of a fifth frame is stored. Image data is accumulated and stored frame by frame in the same manner as the remaining cells. In particular, the present invention does not store the image data in the memory MEM, but removes some bits of the image data as described above to reduce the size thereof, and stores the reduced image data in the memory MEM. Therefore, the use capacity of the memory MEM can be significantly reduced. On the other hand, the value stored in each cell of this memory MEM may be initially set to 0 or any other arbitrary value.

The image modulator IMM reads the added image data from the memory MEM, and modulates the image data of the nth frame from the inverse gamma correction unit RGM based on the added image data read from the memory MEM. To generate the modulated image data of the nth frame. The video data of the nth frame provided from this inverse gamma correction unit RGM is intact video data in which some bits have not been removed. For example, the image modulator IMM generates the modulated image data of the n-th frame by modulating the 8-bit n-th frame image data on the basis of 5-bit addition image data.

To this end, the image modulator IMM includes a gain value selector GNS and a calculator CC.

The gain value selecting unit GNS selects a gain value corresponding to the gray scale value (cumulative gray scale value) of the added image data read from the memory MEM from the gain lookup table GLUT. The gain lookup table GLUT stores gain values having different values according to gray scale values (cumulative gray scale values).

The calculating unit CC generates the modulated image data of the n-th frame by calculating the gain value selected from the gain value selecting unit GNS and the image data of the n-th frame from the inverse gamma correction unit RGM. The operation unit CC may generate the modulated image data of the nth frame by multiplying the gain value by the image data of the intact nth frame.

The modulated image data of the nth frame output from the calculating unit CC is gamma-corrected through the gamma correction unit GM. That is, through the gamma correction unit GM, the modulated image data of the nth frame has gamma information that was previously removed.

The modulated image data of the gamma corrected nth frame from the gamma correction unit GM is supplied to a timing controller, and the timing controller rearranges these image data and controls their output timing.

The data driver selects analog pixel voltages corresponding to the modulated image data of the gamma corrected nth frame from the gamma correction unit GM according to control from a timing controller, and sets the analog pixel voltages in horizontal line units. Feed the fields.

5 is a diagram illustrating a gain lookup table GLUT.

The gain lookup table GLUT stores different gain values according to grayscale values (cumulative grayscale values). For example, as illustrated in FIG. 5, the numerical value located on the left side in the gain lookup table GLUT represents a sum value of the sum of gray values and difference values, and the numerical value located on the right side represents a gain value.

6 is a detailed block diagram of the data correction unit DA according to the second embodiment of the present invention.

In the data correcting unit DA according to the second exemplary embodiment of the present invention, image data from the system does not pass through an inverse gamma conversion unit, as shown in FIG. 6. That is, all of the image data from the system are image data to which gamma information is not added from the beginning, and these image data are directly supplied to the quantizer QT and the image modulator IMM without going through an inverse gamma converter.

The quantization unit QT, the add / update unit ANU, the memory MEM, the gain value selector GNS, the calculation unit CC, and the gain lookup table included in the data correction unit according to the second embodiment of the present invention. (GLUT) and gamma correction unit (GM) are the same as those described above in the first embodiment.

As described above, the present invention does not store the image data in the memory MEM, but removes some bits of the image data to reduce its size as described above, and stores the reduced image data in the memory MEM. As a result, the use capacity of the memory MEM can be considerably reduced.

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 general inventive concept as defined by the appended claims and their equivalents. Will be clear to those who have knowledge of.

RGM: Inverse Gamma Converter QT: Quantizer
ANU: Adder / Updater MEM: Memory
GNS: gain value selector CC: calculator
IMM: Image Modulation Division GM: Gamma Government
GLUT: Gain Lookup Table DA: Data Compensation

Claims (12)

Sequentially outputting image data for supplying a plurality of light emitting elements;
Removing some bits of bits constituting image data of an nth frame (n is a natural number of two or more):
Generating added image data by adding the image data of the n-th frame from which the some bits are removed and the image data of the previous frame stored in the memory;
Storing the added image data in the memory to update the image data of the previous frame with the added image data; And,
The image data of the previous frame is a driving method of the light emitting display device, characterized in that the image data of the first frame from which some bits are removed to the image data of the n-1 frame from which some bits are removed. . The method of claim 1,
Reading the added image data from the memory; And,
And generating modulated image data of the nth frame by modulating the image data of the nth frame in which the partial bit is not removed based on the added image data read from the memory. Driving method. The method of claim 2,
Generating modulated image data of the nth frame may include:
Preparing a gain lookup table having gain values having different values according to the cumulative gray scale values;
Selecting a gain value corresponding to a cumulative gradation value of the added image data read from the memory; And,
And generating the modulated image data of the nth frame by calculating the image data of the nth frame in which the selected gain value and the some bits are not removed. The method of claim 2,
And gamma correcting the modulated image data of the nth frame. The method of claim 2,
Inverse gamma correction of the sequentially output image data; And,
And gamma correcting the modulated image data of the nth frame. The method of claim 1,
The image data are 8 bits of data; And,
And some of the bits are the lower three bits. A system for sequentially outputting image data for supplying a plurality of light emitting elements;
A quantization unit for removing some of the bits constituting the image data of the n-th frame (n is a natural number of two or more) output from the system:
The image data of the n-th frame from which some bits from the quantizer are removed and the image data of the previous frame stored in the memory are added to generate the added image data, and the added image data is stored in the memory to store the image of the previous frame. An addition / update unit for updating data with the added image data; And,
And the image data of the previous frame is accumulated image data obtained by adding all the image data of the first frame from which some bits are removed to the image data of the n-1 frame from which some bits are removed. The method of claim 7, wherein
An image that reads the added image data from the memory and modulates the image data of the nth frame in which the partial bit is not removed based on the added image data read from the memory to generate modulated image data of the nth frame The display device further comprises a modulator. The method of claim 8,
The image modulator,
A gain value selection unit for selecting a gain value corresponding to a cumulative gradation value of the added image data read from the memory from a gain lookup table;
An operation unit configured to generate the modulated image data of the n-th frame by calculating the image data of the n-th frame in which the gain value selected from the gain value selector and the some bits are not removed; And,
And a gain value having different values stored in the gain lookup table according to the accumulated gray scale value. The method of claim 8,
And a gamma compensator for gamma correcting the modulated image data of the nth frame. The method of claim 8,
An inverse gamma correction unit for inverse gamma correction of the sequentially output image data; And,
And a gamma correction unit for gamma correcting the modulated image data of the nth frame. The method of claim 8,
The image data are 8 bits of data; And,
And some bits are lower 3 bits.

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