KR102460922B1 - Display Device and Driving Method thereof - Google Patents

Abstract

A display device according to the present invention includes a display panel in which pixels to which data lines and gate lines are connected are disposed, and a driving circuit unit for displaying a preset standby mode image on a partial region of the display panel in standby mode. The driving circuit unit receives image data for the standby mode image, and extracts a fixed object that does not change in gradation for a preset reference time from the image data, and sequentially varies the gradation value of the fixed object in units of preset blocks. It includes a data modulator that

Description

Display Device and Driving Method thereof

The present invention relates to a display device for improving deterioration and a driving method thereof.

In the display device, data lines and gate lines are arranged to be perpendicular to each other, and pixels are arranged in a matrix form. A video data voltage to be displayed is supplied to the data lines, and a gate pulse is sequentially supplied to the gate lines. A video data voltage is supplied to pixels of a display line to which a gate pulse is supplied, and video data is displayed while all display lines are sequentially scanned by the gate pulse. Among them, the organic light emitting diode display has advantages of fast response speed, high luminance efficiency, and a large viewing angle.

The organic light emitting display device is also applied to mobile terminals such as mobile phones, smart phones, tablet computers, notebook computers, and wearable devices. The mobile terminal stops driving of the display device in order to reduce power consumption in the standby mode. Since the user restarts the mobile terminal when viewing simple information such as a watch, the on/off of the mobile terminal is frequently repeated. In order to reduce the user's inconvenience, an Alaways On Display (AOD) function that always displays information designated by the user, such as a clock and a calendar, on the screen is being added to the mobile terminal. Since the image displayed when the AOD function is operating displays only simple information, there is no long-term gradation change, and it is characterized by high luminance to improve the user's visibility on the background black screen. Accordingly, there is a problem in that deterioration of transistors and organic light emitting diodes belonging to specific pixels is accelerated as a fixed image pattern continuously emits light when the AOD function operates.

An object of the present invention is to provide a display device capable of improving deterioration of a transistor and an organic light emitting diode, and a driving method thereof.

A display device according to the present invention includes a display panel in which pixels to which data lines and gate lines are connected are disposed, and a driving circuit unit for displaying a preset standby mode image on a partial region of the display panel in standby mode. The driving circuit unit receives image data for the standby mode image, and extracts a fixed object that does not change in gradation for a preset reference time from the image data, and sequentially varies the gradation value of the fixed object in units of preset blocks. It includes a data modulator that

According to the present invention, deterioration of the organic light emitting diode and the driving transistor can be prevented by lowering the gray level value of a fixed object that does not change the gray level value in units of a predetermined time. In particular, according to the present invention, the user's visual discomfort due to the change in luminance of the fixed object can be minimized by synchronizing the time of lowering the grayscale value of the fixed object with the time of changing the image of the variable object. In addition, by writing diffusion data to adjacent pixels of the fixed object, the degree of change in luminance of the fixed object is less sensitive to the user.

1 and 2 are views showing a display device according to the present invention.
3 is a diagram illustrating an embodiment of an operation in an AOD mode.
4 is a diagram showing the configuration of a drive IC according to the present invention.
5 is a flowchart illustrating a method of driving a display device according to the present invention.
6 is a diagram illustrating an example of a fixed object.
7 to 11 are diagrams for explaining a data modulation method according to the first embodiment.
12 to 14 are diagrams for explaining a data modulation method according to the second embodiment.

Hereinafter, preferred embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Like reference numerals refer to substantially identical elements throughout. In the following description, if it is determined that a detailed description of a known function or configuration related to the present invention may unnecessarily obscure the gist of the present invention, the detailed description thereof will be omitted.

1 is a diagram schematically showing a display device according to an embodiment of the present invention, and FIG. 2 is a diagram showing an example of a pixel.

1 and 2 , the display device of the present invention includes a display panel PNL and a drive IC DIC for driving the display panel PNL.

The display portion AA of the display panel PNL is formed by data lines DL, gate lines GL orthogonal to the data lines DL, and data lines DL and gate lines GL. It includes pixels P in a defined matrix form. Each of the pixels P includes an organic light emitting diode (OLED), a driving transistor DT for controlling the amount of current flowing through the OLED, and a programming unit for controlling the operation of the driving transistor DT as shown in FIG. 2 . SC). The programming unit SC includes a combination of one or more transistors and one or more capacitors to control voltages of a main node, for example, a gate electrode and a source electrode of the driving transistor DT. For example, the programming unit SC writes a data voltage received from the data line D to the programming unit SC in response to a gate pulse applied from the gate line GL. The driving transistor DT supplies a driving current proportional to the size of the data voltage written in the programming unit SC to the organic light emitting diode OLED. The organic light emitting diode OLED emits light in proportion to the magnitude of the driving current supplied from the driving transistor DT. The organic light emitting diode (OLED) includes an anode (ANO), a cathode (CAT), and an organic compound layer interposed between the anode (ANO) and the cathode (CAT). The anode ANO is connected to the driving transistor DT.

The gate driver 120 may be formed in the display panel PNL. The gate driver 120 includes a shift register that outputs a gate pulse synchronized with a data signal in response to a gate timing control signal input through the drive IC (DIC). The gate timing control signal includes a start pulse and a shift clock. The shift register sequentially supplies the gate pulses to the gate lines GL by shifting the gate pulses according to the shift clock timing.

The TFTs T of the display panel PNL are turned on according to a gate pulse to select a line of the display panel PNL in which data of an input image is written. The shift register may be directly formed on the substrate of the display panel PNL in the same process as the TFT array of the pixel array.

The display unit AA displays preset information on the AOD area AA1 as shown in FIG. 3 in a standby mode such as the AOD mode. The information displayed on the AOD area may include a variable image AA12 in which an image is changed in units of a predetermined time, such as time information, and a fixed image AA11, in which an image does not change, such as a logo.

The drive IC DIC supplies the data signal of the input image to the data lines DL and supplies the gate timing control signal including the clock signals CLK to the gate driver 120 .

A demultiplexer (MUX) may be disposed between the drive IC (DIC) and the data lines (D).

4 is a diagram showing the configuration of a drive IC according to the present invention.

Referring to FIG. 4 , the drive IC (DIC) includes a power supply unit 10 , a timing signal generating unit 100 and a data driving unit 110 , and deterioration improving units 101 and 103 .

The power supply unit 10 generates DC power required for driving the display panel PNL by using a DC-DC converter.

The timing signal generator 100 transmits pixel data of an input image received from a host system (not shown) to the data driver 110 . The timing signal generator 100 receives a timing signal received in synchronization with pixel data, a data timing control signal for controlling the operation timing of the data driver 110 , and a data timing control signal for controlling the operation timing of the gate driver 120 . A gate timing control signal is generated. In this case, the timing signal generator 100 generates a MUX control signal for controlling a demultiplexer (MUX).

The data driver 110 receives the pixel data (digital data) of the input image from the timing signal generator 100 during the display period, latches it, and then performs a digital-to-analog converter (hereinafter referred to as "DAC"). ) is supplied. The DAC converts the pixel data into a gamma compensation voltage to generate a voltage of the data signal.

The timing signal generating unit 100 includes a deterioration improving unit for improving deterioration caused by a fixed image in the AOD mode. The deterioration improving units 101 and 103 include a fixed object extracting unit 101 and a data modulating unit 103 .

The fixed object extraction unit 101 extracts the fixed object FO from the AOD image shown in FIG. 3 when the AOD mode is operating. The fixed object (FO) refers to an image in which the gradation of image data does not change for a certain period of time among AOD images. The data modulator 103 changes the image data of the fixed object extracted by the fixed object extractor 101 . In particular, the data modulator 103 writes spread data proportional to the data of the fixed object FO in pixels P adjacent to the fixed object FO in addition to the image data of the fixed object FO itself. Accordingly, in the process of changing the image data to prevent deterioration, the user may not feel a visual objection due to the image change.

Hereinafter, the operation of the deterioration improving unit will be described in detail.

5 is a flowchart illustrating a method of driving a display device using a deterioration improving unit according to the present invention. 6 is a diagram illustrating an example of a fixed object to be subjected to data modulation. 7 to 11 are diagrams illustrating the operation of the data modulator according to the first embodiment.

A driving method of the organic light emitting display device according to the first embodiment will be described with reference to FIGS. 5 to 11 .

First, in the first step (S501), the fixed object extraction unit 101 extracts the fixed object (FO). To this end, first, the fixed object extraction unit 101 may detect an edge of an image. The fixed object extraction unit 101 may detect an edge, and may regard an area belonging to the detected edge as an image object.

In a method for the fixed object extractor 101 to detect an edge, an edge may be detected based on a difference in gradation between adjacent pixels P using a known mask. That is, the fixed object extraction unit 101 may regard a continuous boundary in which the grayscale difference between adjacent pixels P is equal to or greater than a threshold value as an edge of the image.

After the edge is extracted, the fixed object extraction unit 101 reads changes in image data belonging to the image object. That is, the fixed object extraction unit 101 reads changes in the image data belonging to the image object on a frame-by-frame basis, and when there is no change in the image data for a preset reference time, the image object is regarded as a fixed object (FO). do. The reference time for determining the fixed object FO may be set as the minimum time that may cause deterioration of the pixels P.

In addition, the fixed object extraction unit 101 may extract the fixed object FO by using preset AOD information. The AOD mode operates in a state in which preset information is stored in a memory (not shown). Accordingly, image information of the fixed object FO is separately stored in the memory among the AOD image information, and the fixed object extraction unit 101 can extract image information of the fixed object FO from the memory.

As such, the fixed object extraction unit 101 may extract the fixed object FO shown in FIG. 6 from the AOD image.

7 illustrates grayscale values written in pixels belonging to the fixed object FO area. That is, FIG. 7 shows an embodiment in which 255 gray levels are written in the fixed object FO.

In the second step ( S502 ), the data modulator 103 writes diffusion data into the pixels P adjacent to the fixed object FO. 8 shows an embodiment in which the data modulator writes spread data. The diffusion data may be written in pixels P surrounding the fixed object FO. Although FIG. 8 shows an embodiment in which diffusion data is written only in one row and one column adjacent to the fixed object FO, the area of the pixels P in which the diffusion data is written is not limited thereto.

The size of the diffusion data may be proportional to the grayscale value of the fixed object FO within a range smaller than the grayscale value of the fixed object FO. That is, when the grayscale value of the fixed object FO is large, the grayscale value of the diffusion data is set to be large, and when the grayscale value of the fixed object FO is small, the grayscale value of the diffusion data is also set to be small. 8 illustrates an embodiment in which the size of the diffusion data is set to about 50% of the fixed object (FO) grayscale value, but the size of the diffusion data is not limited thereto.

In the third step ( S503 ), the data modulator 103 generates the modulated data M_DATA in which the grayscale value of the fixed object FO is varied.

9 shows an embodiment in which the data modulator generates modulated data of a fixed object. The data modulator 103 may generate the modulated data M_DATA such that the size of the modulated data M_DATA is lower than the grayscale value of the input image data of the fixed object FO. For example, as shown in FIG. 8 , the data modulator 103 may generate modulated data to have a size of about 90% of the grayscale value of the fixed object FO.

In the fourth step (S504), the data modulator 103 divides the fixed object FO by region and changes data for each region in units of time.

10 and 11 show an embodiment in which the data modulator 103 varies the data of the fixed object FO for each block. In particular, in FIGS. 10 and 11 , the area in which the fixed object FO is displayed is configured to vary data of the i-th block BLi and the (i+1)-th block BL[i+1] among a plurality of blocks. Examples are shown. The first embodiment shows an embodiment in which the fixed object FO is divided into a plurality of blocks based on pixel lines. For example, each of the blocks may include four pixel lines HL as shown in FIGS. 10 and 11 .

As shown in FIG. 10 , the data modulator 103 changes the grayscale value of the modulated data of the fixed object FO belonging to the i-th block BLi at the first timing to decrease. Subsequently, as shown in FIG. 11 , the data modulator 103 lowers the grayscale value of the modulated data of the fixed object FO belonging to the (i+1)th block BL[i+1] at the second timing. At the second timing, the data modulator 103 restores the modulated data of the i-th block BLi changed at the first timing to its original state.

The interval between the first timing and the second timing may be arbitrarily set, but may be based on the image change time of the variable image AA12 belonging to the AOD area. For example, when the variable image AA12 is a digital watch in which an image displayed in units of minutes is different from that of FIG. 4 , the data modulator 103 performs the process of the fourth step S504 in units of one minute. can do. That is, the modulated data of the fixed object FO belonging to the i-th block BLi is changed at an arbitrary point in time, and the fixed object FO belonging to the (i+1)-th block BL[i+1] is changed after 1 minute. FO) modulated data can be varied. As such, the modulated data M_DATA varies the modulated data of the fixed object FO at the timing when the image of the variable image AA12 is changed, thereby slowing the user from recognizing the change in luminance of the fixed object FO. .

In the above-described first embodiment, it has been described that the fourth step (S504) of varying the grayscale value of the fixed object FO in blocks at regular time intervals is performed after the third step (S503). Therefore, in the fourth step (S504), the data belonging to the fixed object (FO) has been described based on the fact that it corresponds to the modulated data.

The fourth step (S504) according to the present invention may be performed separately from the second step (S502) and the third step (S503). Therefore, in the fourth step ( S504 ), the grayscale value of the fixed object (FO) area, which is varied at regular time intervals, is not the modulated data M_DATA shown in FIG. 9 but the input image data DATA shown in FIG. 7 . It may be a grayscale value.

12 to 14 are diagrams illustrating a method of driving a display device according to a second exemplary embodiment. The second embodiment is a modified embodiment of the fourth step (S504) described in the first embodiment, and a method of changing the image data of a fixed object in units of time in a state in which the image data of the fixed object is not generated as modulated data. is explaining In the second embodiment, it is shown that the fixed object is a circular clock face and a number indicating time. The hour hand, the minute hand, and the second hand SP correspond to a variable image in which the image moves at regular time intervals. In the second embodiment, the fixed object may divide the blocks BL in the form of an arc. A central angle of each of the first to twelfth blocks BL1 to BL12 corresponds to 30°. Each number from 1 to 12 belonging to a fixed object belongs to one block. For example, as shown in the drawing, the first block BL1 includes the number '1', and the second block BL2 includes the number '2'.

Referring to FIG. 12 , at a first timing, the data modulator 103 changes the grayscale value of the number '1', which is a fixed object belonging to the first block BL1. The data modulator 103 lowers the grayscale value of the number '1', which is a fixed object.

The data modulator 103 lowers the grayscale value of the fixed object belonging to the block for a predetermined period of time, for example, in seconds. Accordingly, the grayscale value of the number '1' of the first block BL1 is lowered, and after 1 second, the grayscale value of the number '2' of the first block BL1 is lowered.

As a result, 9 seconds after the time when the fixed object of the first block BL1 shown in FIG. 12 is lowered, as shown in FIG. 13 , the grayscale value of the number '10', which is the fixed object of the tenth block BL10, is lowered. Subsequently, after 11 seconds have elapsed from the first timing, as shown in FIG. 14 , the grayscale value of the number '12', which is a fixed object belonging to the twelfth block BL12, is lowered.

The data modulator 103 may synchronize the timing of lowering the grayscale value of the fixed object belonging to each block to the change time of the variable object. That is, the data modulator 103 lowers the grayscale value of the fixed object when the position of the second hand SP is changed according to the movement of the second hand SP, which is a variable object. A fixed object should be expressed with the same luminance in the normal image display process. Accordingly, since the operation of the data modulator 103 to lower the gray scale value of the fixed object is out of the general image display, the user may feel visually inconvenient. When there are several changes in the process of recognizing the image of the field of view, the user recognizes the largest image change first. That is, when the second hand SP, which is a variable object, moves, the user's gaze first senses the movement of the second hand SP, so that the grayscale change value of the fixed object cannot be easily recognized.

In the first and second embodiments, the degree to which the data modulator 103 lowers the grayscale value of the fixed object may be set in consideration of the user's visibility. This is because, even if the user reacts to the change of the variable object first, if the gray scale value of the fixed object changes excessively, the user may feel uncomfortable due to the change in the luminance of the fixed object.

As described above, according to the present invention, deterioration of the organic light emitting diode and the driving transistor can be prevented by lowering the grayscale value of the fixed object in units of a predetermined time. In particular, according to the present invention, the user's visual discomfort due to the change in luminance of the fixed object can be minimized by synchronizing the time of lowering the grayscale value of the fixed object with the time of changing the image of the variable object. In addition, by writing diffusion data to adjacent pixels of the fixed object, the degree of change in luminance of the fixed object is less sensitive to the user.

Those skilled in the art from the above description will be able to see that various changes and modifications are possible without departing from the technical spirit of the present invention. Accordingly, 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.

PNL: Display panel DIC: Drive IC
10: power supply unit 100: timing signal generating unit
101: fixed object extraction unit 103: data modulator
110: data driver 120: gate driver

Claims (10)

a display panel in which pixels to which data lines and gate lines are connected are disposed; and
and a driving circuit unit for displaying a preset standby mode image on a partial region of the display panel in standby mode,
The driving circuit
a fixed object extraction unit that receives image data for the standby mode image and extracts a fixed object having no grayscale change for a preset reference time from the image data; and
and a data modulator for sequentially varying the grayscale value of the fixed object in units of preset blocks;
The standby mode image further includes a variable image that changes every predetermined period, and the data modulator is synchronized with a change time of the variable image to change the grayscale value of the fixed object.
The method of claim 1,
The data modulator receives image data having a first grayscale value, and changes the image data to a second grayscale value that is lower than the first grayscale value.
delete 3. The method of claim 2,
The fixed object includes first and second blocks,
The data modulator
changing a first grayscale value of the image data belonging to the first block to the second grayscale value at a first timing;
A display device for changing a first grayscale value of the image data belonging to the second block to the second grayscale value at a second timing.
5. The method of claim 4,
The data modulator restores the grayscale value of the image data belonging to the first block to the second grayscale value at the second timing.
3. The method of claim 2,
The data modulator
A display device for writing diffusion data having a third grayscale value lower than the first grayscale value in pixels adjacent to the fixed object.
7. The method of claim 6,
The data modulator sets the third grayscale value to be smaller than the second grayscale value.
receiving image data written on a display panel and extracting a fixed object in which the image data does not change for a preset reference time; and
and sequentially varying the grayscale value of the fixed object in units of preset blocks;
The varying the gradation value of the fixed object is synchronized with a change time point of the variable image in which the gradation value is changed every predetermined period, thereby changing the gradation value of the fixed object.
delete 9. The method of claim 8,
The step of varying the gradation value of the fixed object includes:
varying a first grayscale value of image data belonging to a first block into a second grayscale value; and
and changing the first grayscale value of image data belonging to a second block to the second grayscale value and restoring the second grayscale value belonging to the first block to the first grayscale value. driving method.

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