KR101941446B1 - Organic light emitting diode display device and driving method the same - Google Patents

Abstract

The present invention relates to an organic light emitting diode display device capable of correcting luminance unevenness by measuring characteristics of each pixel at a high speed and a driving method thereof. In one embodiment, during each sensing frame belonging to a measurement mode, The number of pixels to be lit by the sensing image data gradually increases and the current measured through the power supply line of the display panel increases stepwise as the pixel data is sequentially supplied to one pixel, The number of pixels which are extinguished by the sensed image data gradually decreases and the current measured through the power supply line decreases step by step. The characteristic information of each pixel is acquired and stored by using an increment or a decrement between the current value measured in any pixel row driving period and the current value measured in the driving period of the previous pixel row, To compensate the image data.

Description

Technical Field [0001] The present invention relates to an organic light emitting diode (OLED) display device,

The present invention relates to an organic light emitting diode (OLED) display device and a method of driving the same, capable of correcting luminance unevenness by measuring characteristics of each pixel at a high speed.

The AMOLED display is a self-luminous device that emits an organic light-emitting layer by recombination of electrons and holes, and is expected to be a next-generation display device because of its high luminance, low driving voltage and ultra thin film.

Each of the plurality of pixels constituting the AMOLED display device includes an organic light emitting diode (OLED) composed of an organic light emitting layer between the anode and the cathode, and a pixel driving circuit for independently driving the OLED. The pixel driving circuit mainly includes a switching thin film transistor (hereinafter referred to as a TFT) and a capacitor and a driving TFT. The switching TFT charges the capacitor corresponding to the data signal in response to the scan pulse and controls the magnitude of the current supplied to the OLED according to the magnitude of the voltage charged in the capacitor to control the amount of light emitted from the OLED. The amount of light emission of the OLED is proportional to the current supplied from the driving TFT.

However, in OLED display devices, characteristics of TFTs such as a threshold voltage (Vth) and a process deviation (mobility, parasitic capacitance, channel width / length) factor of a driving TFT are uneven for each pixel for reasons of process variation and the like, The current, that is, the amount of OLED light emission, becomes non-uniform for each pixel, resulting in uneven luminance. To solve this problem, a data compensation method for reducing luminance unevenness by measuring characteristic parameters of a driving TFT of each pixel driving circuit and correcting input data according to a measurement result is used.

The characteristics of the driving TFT can be measured by measuring the current of the pixel according to different voltages. However, it is difficult to measure the current of many pixels at high speed as the size of the AMOLED display becomes larger. For example, U.S. Patent No. 7,161,566 discloses a method of measuring current flowing through a power supply line (ELVDD line or VSS line) of a display panel by lighting one pixel at a time, but the threshold voltage and process variation factor information In order to obtain the information, it is necessary to acquire and store the information of all the pixels of the display panel, so that it takes a long time for sensing and is not suitable for a large-area display device.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an organic light emitting diode (OLED) display device and a method of driving the same, capable of correcting luminance unevenness by measuring characteristics of each pixel at high speed.

In order to achieve the above object, in the organic light emitting diode display device according to the embodiment of the present invention, during each sensing frame belonging to the measurement mode, sensing image data is supplied to at least one pixel for each pixel row, The number of pixels turned on by the sensing image data gradually increases and the current measured through the power supply line of the display panel gradually increases or the number of pixels that are extinguished by the sensing image data gradually decreases The current measured through the power supply line decreases stepwise. The timing controller obtains and stores characteristic information of each pixel by using an increment or a decrement between a current value measured in a pixel row driving period and a current value measured in a driving period of a previous pixel row, The image data is compensated using the characteristic information.

The pixels to which the sensing image data is supplied in each sensing frame are pixels arranged in any one of the pixel columns or arranged in the diagonal direction. The pixels to which the sensing image data is supplied in each sensing frame period are at least one space in the horizontal direction Shifted.

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The present invention can light up the number of pixels corresponding to one column during one sensing frame period and acquire and store the information. Therefore, it is possible to correct the luminance unevenness by measuring the characteristics of each pixel at a high speed.

1 is a configuration diagram of an OLED display according to an embodiment.
2 is a configuration circuit diagram of the pixel cell 10 shown in FIG.
3A and 3B are diagrams illustrating a measurement mode period according to the embodiment.
4A and 4B are views for explaining sensing image data according to the first embodiment.
5A and 5B are views for explaining sensing image data according to the second embodiment.
6 is an ELVDD current waveform diagram according to an embodiment.
7 is an ELVDD current waveform diagram according to another embodiment.

Hereinafter, an organic light emitting diode (OLED) display device and a driving method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a configuration diagram of an OLED display according to an embodiment. And FIG. 2 is a circuit diagram of the pixel cell 10 shown in FIG.

The OLED display device shown in FIG. 1 includes a display panel 2, a data driver 4, a gate driver 6, a timing controller 8, a power supply unit 12, and a detector 14 Respectively. The OLED display device shown in Fig. 1 is divided into a measurement mode for measuring characteristic parameters of each pixel driving circuit 16 and a display mode for normal image display.

The display panel 2 includes a plurality of gate lines GL and a plurality of data lines DL. The gate line GL and the data line DL intersect each other to define a pixel region. Each pixel region is provided with a pixel cell 10 connected to a gate line GL and a data line DL. The display panel 2 is further provided with an ELVDD line ELVDDL and a VSS line (not shown) for applying ELVDD and VSS provided from the power supply unit 12 to the pixel cells 10.

Each of the pixel cells 10 receives a data signal supplied from the data line DL in response to a scan pulse supplied from the gate line GL and generates a light corresponding to the data signal. To this end, the pixel cell 10 includes an OLED and a pixel driving circuit 16 for driving the OLED, as shown in Fig.

The anode electrode of the OLED is electrically connected to the pixel driving circuit 16, and the cathode electrode is electrically connected to VSS. The OLED emits light in accordance with the current supplied from the pixel driving circuit 16 in accordance with the data signal.

The pixel driving circuit 16 includes a driving TFT T2 for supplying a current corresponding to the data signal to the OLED in accordance with the voltage between the gate electrode and the source electrode and a driving TFT T2 for supplying a current corresponding to the data signal to the data line DL in accordance with the scanning pulse supplied from the gate line GL. A switching TFT T1 connected between the gate and the source of the driving TFT T2 for supplying a voltage corresponding to a data signal supplied from the switching TFT T1 to the gate electrode of the driving TFT T2, And a capacitor Cst for storing the data. 2 is composed of 2T1C (two TFTs and one capacitor), and the TFT is of P type, but this is an example, and the present invention is applicable to various pixel driving circuits for driving an OLED Applicable.

The data driver 4 latches digital image data and sensing image data provided from the timing controller 8, and converts the latched data into a data signal using a gamma voltage. And supplies the converted data signal to the data line DL of the display panel 2. Here, the sensed image data is for sensing the deterioration of the pixel driving circuit 16 of the display panel 2 and the change of the operating characteristic according to the temperature change. The sensing image data according to the sensing image data includes a sensing pattern 18 having a constant luminance. Sensing image data will be described later in detail.

The gate driver 6 generates a scan signal based on the gate control signal supplied from the timing controller 8, and sequentially supplies the generated scan signal to the plurality of gate lines GL.

The power supply unit 12 generates ELVDD and VSS and supplies them to the ELVDD line and the VSS line of the display panel 2. [

The detection unit 14 operates in the measurement mode and measures the current or voltage of the ELVDD applied to the display panel 2 from the power supply unit 12 in operation. Then, the measured current or voltage is converted into digital data and supplied to the timing controller 8. Hereinafter, the detection unit 14 is described as measuring the current of the ELVDD.

The timing controller 8 generates digital image data by arranging the image signals input from the outside on a frame-by-frame basis, and supplies the digital image data to the data driver 4. The timing control unit 8 generates a data control signal and a gate control signal based on the timing synchronization signal, supplies the generated data control signal to the data driver 4, and supplies the generated gate control signal to the gate driver 6 .

The timing synchronization signal may include a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a data enable signal Data Enable, and a dot clock DCLK.

The data control signal may be a source start pulse, a source sampling clock, a source output enable, or the like. The gate control signal may be a gate start pulse, a gate shift clock, a gate output enable, or the like.

On the other hand, the timing controller 8 operates in the measurement mode in response to the user's control signal and the external control signal. That is, the timing controller 8 generates sensing image data when a user's control signal or an external control signal is input, and supplies the sensed image data to the data driver 4. The timing controller 8 acquires and stores the characteristic of the pixel from the ELVDD current supplied from the detector 14 and uses it to correct the digital image data to be supplied to the data driver 4. [ The ELVDD current supplied from the detection unit 14 to the timing control unit 8 changes in accordance with the lighting of the sensing pattern 18 in the sensing frame period (the frame in which the sensing video data is displayed) The threshold voltage of the corresponding pixel and the process deviation.

The measurement mode may be directly set according to a control signal of a user, and a period of operation may be variable according to a user's setting. For example, the measurement mode may be operated in a standby mode in which the display device is powered off as shown in FIG. 3A. In addition, the measurement mode can be operated at regular intervals after the power of the display device is turned on as shown in FIG. 3B. That is, the OLED display device according to FIG. 3A obtains and stores the characteristic information of the display panel 2 in advance in a waiting time when the user does not use the display device, and displays the characteristic information on the display panel 2 at a time when the user uses the display device. And compensates for the characteristic deviation of the image. In the OLED display according to FIG. 3B, a sensing frame is inserted at regular intervals between frames in which an image is displayed, so that deterioration of a pixel and change in characteristics due to use for a long time can be compensated. On the other hand, if the sensing frame is inserted at regular intervals between frames in which an image is displayed, the user can recognize the sensing frame as a residual image. To prevent this, a sensing frame may be inserted between display frames at random intervals.

In the OLED display according to the embodiment, at the time of lighting the pixels in the measurement mode, at least one pixel is turned on for each pixel row. And the pixels to be lighted are shifted at least one space in the horizontal direction every sensing frame period. For example, in the embodiment, only one pixel is turned on for each pixel row, and the pixels are shifted by one column in the horizontal direction for each sensing frame period. In this case, the number of pixels corresponding to one column during one sensing frame period can be lit, and information of these can be acquired and stored.

If the display panel 2 is driven by FHD (1920 * 1080) at 60 Hz, the conventional compensation method turns on one subpixel during one sensing frame period, so the required time is (1920 * 1080 * 3) / 60 seconds , It takes about 29 hours to sense all the pixels. However, since the present invention is lit as many as the number of pixels corresponding to one column during one sensing frame period, the required time is (1920 * 3) / 60 seconds, and it takes 96 seconds to sense all the pixels. That is, it can be seen that the compensation time is reduced 1080 times when the present invention is applied to the display panel 2 driven by FHD (1920 * 1080) and 60 Hz.

Hereinafter, the sensing image data according to the embodiment will be described as an example.

FIGS. 4A and 4B are views for explaining sensing image data according to the first embodiment, and FIGS. 5A and 5B are views for explaining sensed image data according to the second embodiment.

As shown in FIG. 4A, the sensing image data according to the first embodiment includes a sensing pattern 18 composed of pixels in one column arranged to be lit in the vertical direction among all the pixels. The sensing pattern 18 may have a maximum brightness (Max Gray), a middle brightness (Middle Gray), a minimum brightness (Low Gray), and other pixels except the pixels corresponding to the sensing pattern have a brightness of black .

The sensing pattern 18 according to the first embodiment is shifted in the horizontal direction every sensing frame period, as shown in Fig. 4B. For example, the sensing pattern 18 in the first sensing frame period may be a pattern in which the pixels arranged in the first column from the left side of the display panel 2 are lit. The sensing pattern 18 in the second sensing frame period may be a pattern in which the pixels arranged in the second column from the left side of the display panel 2 are lighted. And the sensing pattern 18 in the last sensing frame period may be a pattern in which pixels arranged in the last column from the left side of the display panel 2 are lit. The first embodiment is advantageous in that the circuit structure of the detector 14 for measuring the current of the ELVDD according to the sensing pattern 18 is simplified and is easily implemented.

As shown in FIG. 5A, the sensing image data according to the second embodiment includes a sensing pattern 18 composed of pixels arranged in a diagonal direction among all the pixels. The sensing pattern 18 may have a maximum brightness (Max Gray), a middle brightness (Middle Gray), a minimum brightness (Low Gray), and other pixels except the pixels corresponding to the sensing pattern have a brightness of black .

Referring to FIG. 5B, the sensing pattern 18 according to the second embodiment is shifted in the horizontal direction as in the first embodiment. In this second embodiment, not only one pixel is lit for each pixel row, but only one pixel is lit for each pixel column, so that interference between pixel columns can be minimized and pixel information can be obtained more accurately.

Hereinafter, a method of acquiring the characteristic information of the pixel in the measurement mode will be described.

Referring to FIG. 6, the ELVDD current increases in a stepwise manner as one pixel is lit for each pixel row. The detection unit 14 senses a change in the ELVDD current applied to the display panel 2 every one horizontal period when a data signal corresponding to the sensed image data is applied to the display panel 2. [ The detecting section 14 converts the increment of the ELVDD current, which increases every one horizontal period, into digital data and supplies it to the timing control section 8. [ At this time, the increment of the ELVDD current differs depending on the characteristics of the lit pixel, and the timing controller 8 analyzes the increment of the ELVDD current to acquire and store characteristic information of each lit pixel.

In the above description, the method of acquiring the characteristic information of the pixel is a method of sequentially lighting the sensing pattern 18 and sensing the increment of the ELVDD current accordingly, but it is also possible to acquire the characteristic information of the pixel by using the set sensing pattern 18 May be varied in various ways. For example, a method of acquiring the characteristic information of a pixel may be a method of sequentially extinguishing pixels sequentially and sensing the decrease of the ELVDD current as shown in FIG. It may also be a method of individually sensing the ELVDD current while sequentially turning on and off the pixels. Further, when the variation of the ELVDD current is small, the ELVDD current may be measured at a predetermined horizontal period.

As described above, the present invention can light up the number of pixels corresponding to one column during one sensing frame period, and can acquire and store the information. Therefore, the threshold voltage and process variation information of the TFT provided in the pixel can be measured at a high speed to correct the luminance unevenness.

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.

10: pixel cell 16: pixel driving circuit

Claims (10)

A display panel including a plurality of pixels;
A gate driver for driving gate lines of the display panel;
A data driver driving data lines of the display panel;
A timing controller for controlling driving of the gate driver and the data driver, generating sensing image data in a measurement mode, and supplying the sensed image data to the display panel through the data driver;
And a detection unit for measuring a current applied to a power supply line of the display panel from a power supply unit in the measurement mode, and digitizing the measured current to provide the measured current to the timing control unit;
The sensing image data is supplied to at least one pixel for each pixel row during each sensing frame belonging to the measurement mode, and as each pixel row is sequentially driven, the number of pixels illuminated by the sensing image data gradually increases The current measured through the detection unit increases stepwise or the number of pixels that are extinguished by the sensing image data gradually decreases to gradually decrease the current measured through the detection unit,
The timing control unit may acquire and store characteristic information of each pixel by using an increment or a decrease between the current value measured in the driving period of one pixel line provided from the detection unit and the current value measured in the driving period of the previous pixel line And compensates the image data using the characteristic information of each pixel, and supplies the compensated image data to the data driver. The method according to claim 1,
In the sensing frame, the pixels to which the sensing image data is supplied are pixels arranged in any one of the pixel columns, pixels arranged in the diagonal direction,
Wherein the pixels to which the sensing image data is supplied are shifted by at least one space in the horizontal direction for each sensing frame period. The method according to claim 1,
Wherein the measurement mode is set to operate between a power-on time, a power-off time, or between frames. delete delete During each sensing frame belonging to the measurement mode, sensing image data is supplied to at least one pixel for each pixel row, and as each pixel row is sequentially driven, the number of pixels turned on by the sensing image data gradually increases Measuring a current through the power supply line of the display panel or measuring a gradually decreasing current through the power supply line by gradually decreasing the number of pixels extinguished by the sensed image data;
Acquiring and storing characteristic information of each pixel by using an increase or decrease between a current value measured in a pixel row driving period and a current value measured in a driving period of a previous pixel row;
And compensating the image data using the characteristic information of each pixel. The method according to claim 6,
In the sensing frame, the pixels to which the sensing image data is supplied are pixels arranged in any one of the pixel columns, pixels arranged in the diagonal direction,
Wherein the pixels to which the sensing image data is supplied are shifted by at least one space in the horizontal direction for each sensing frame period. delete delete delete

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