KR20200015645A - Display device and driving method thereof - Google Patents

Abstract

The present invention relates to a driving method of a display device and a driving device of a display device. The driving method capable of reducing the power consumption comprises the steps of: comparing image data of a current frame (a random n^th frame) input from the outside with image data of a previous frame (an (n-1)^th frame) and sorting a moving image display pixel row and a stopped image display pixel row; and driving the moving image display pixel row with a moving image frequency and driving the stopped image display pixel row with a stopped image display frequency lower than the moving image frequency. A plurality of the stopped image display pixel rows are driven with two or more stopped image display frequencies.

Description

Display device and driving method of display device {DISPLAY DEVICE AND DRIVING METHOD THEREOF}

The present invention relates to a display device and a method of driving the display device.

The display device has various kinds of flat panel display devices such as a liquid crystal display, an organic light emitting display, an electrophoretic display, and a plasma display. The display device includes a panel, a driving chip and a board on which the driving chip is mounted; It includes a system.

As the band width of data transmission increases in the display field, high-speed data transmission between driving chips, boards, and systems is required, and thus, low voltage differential signaling (LVDS) is widely used. In the case of LVDS data transmission, the operation speed can be improved, and the use of low voltage reduces power consumption, EMI problems and manufacturing costs.

The image displayed by the display device includes a moving image that changes greatly every moment and a still image that is stopped for a predetermined time. In the case of still images, in order to reduce power consumption, a technology that does not transmit data using PSR (Pixel Self Refresh) technology is used. However, PSR technology is applied only in the data transfer method capable of bidirectional communication.

In addition, as the display device increases in size, the use of only a part of an area of one screen is increasing, and even when a video is displayed only in a corresponding area and a still image is displayed in the remaining part, all pixels must be operated at a constant frequency. Therefore, there is a disadvantage in that power consumption cannot be reduced even when a video is displayed only in some areas.

An object of the present invention is to provide a driving method of a display device and a driving device of a display device in which a moving image is displayed on only a part of screens while the still image of the remaining part displays an image at a low frequency.

In order to solve this problem, the display device driving method according to an exemplary embodiment of the present invention compares the image data of the current frame (random nth frame) input from the outside with the image data of the previous frame (n-1th frame). Dividing the moving image display pixel row into a still image display pixel row; Driving the video display pixel row at a video frequency and driving the still image display pixel row at a still image display frequency lower than the video frequency, wherein the plurality of the still image display pixel rows are at least two or more of the still images. Drive at the video display frequency.

A pixel row close to the video display pixel row among the plurality of still image display pixel rows may be driven at a higher frequency than a distant pixel row.

The video display pixel row may include a video display area and a refresh area sharing a gate line with the video display area.

The step of dividing the image data of the current frame input from the outside into the image display pixel row and the still image display pixel row by comparing the image data of the previous frame with the previous data stored while storing the image data of the current frame in the frame memory. Outputting image data of a frame to a comparator; The comparator may include comparing the image data of the current frame with the image data of the previous frame.

The comparator may compare the image data of the current frame and the image data of the previous frame for each pixel row to compare whether a still image or a video is displayed for each pixel row.

The result compared in the comparator may further include storing in a line buffer memory.

Data output from the comparator and stored in the line buffer memory is 2-bit data, where 0 represents a still image and 1 represents a video.

When the still image display pixel row is present between the moving image display pixel rows displaying the moving image, the still image display pixel row existing between the still image display pixel rows may also be operated as the moving image display pixel row.

The video display pixel row is driven at a video frequency, and the still image display pixel row is driven at a still image display frequency lower than the video frequency. The gate-on voltage is transmitted to the gate line using an output enable signal. Can be screened as possible.

The output enable signal may be used to screen the data voltage when the gate on voltage is not applied.

The driving of the still image display pixel row at a still image display frequency lower than the video frequency may include: finding an optimal still image display frequency; Determining an upper still image display frequency in an upper still image display region located above the moving image pixel row, and a lower still image display frequency in a lower still image display region located below the moving image pixel row It may include the step.

The determining of the optimal still image display frequency may include calculating a representative value through an image pattern of a still image display pixel row, and selecting the optimum still image display frequency from a look-up table based on the calculated representative value.

Identifying the upper still image display frequency, and determining the lower still image display frequency include: calculating a representative value of a corresponding pixel row; The upper still image display frequency and the lower still image display frequency may be selected in the lookup table based on the calculated representative value.

Determining the upper still image display frequency, and determining the lower still image display frequency further include calculating a weight of the corresponding pixel row, and applying the weight to the representative value instead of the representative value. The upper still image display frequency and the lower still image display frequency may be selected in the lookup table based on the multiplied value.

A frequency may gradually increase from an upper still image display frequency and a lower still image display frequency to the video frequency.

The frequency may increase in a curved form from the upper still image display frequency and the lower still image display frequency to the video frequency.

When the upper still image display frequency or the lower still image display frequency is lower than the optimal still image display frequency, an operating frequency for displaying the pixel row may be operated at the optimum still image display frequency.

A driving device of a display device according to an exemplary embodiment of the present invention includes a still image / video determination unit for dividing image data input from the outside into a video display pixel row or a still image display pixel row, and a representative value for calculating a representative value for each pixel row. A calculation unit, a lookup table storing a frequency value with respect to the representative value, and a driving frequency determination unit determining whether the frequency determined in the lookup table is appropriate and determining the final driving frequency, wherein the video display pixel row is a video frequency. And the still image display pixel row is driven at a still image display frequency lower than the video frequency, and the plurality of still image display pixel rows are driven at least two or more of the still image display frequencies.

The apparatus may further include a weight calculator configured to multiply the representative value to give a weight, and select a frequency from the lookup table based on the product of the representative value and the weight.

The method may further include an optimum still image display frequency extracting unit configured to calculate a representative value through an image pattern of a still image display pixel row, and select a corresponding optimum still image display frequency from the lookup table based on the calculated representative value.

The representative value may be a gray value or a luminance value.

The representative value may be one of an average value, a peak value, and a maximum gray value.

The weight may provide the largest value as the weight when the middle gray level is provided and the smallest value as the weight when the maximum or minimum gray level is the weight.

The weight may calculate an area corresponding to the representative value to provide a larger weight as the area becomes larger.

The apparatus may further include a position determiner configured to determine to which pixel of the display panel the image data continuously input is actually applied, and the output of the position determiner may be transmitted to the still image / movie determiner.

The display apparatus may further include a moving image display pixel row setting unit configured to receive an output of the position determining unit and to set which pixel row is a moving image display pixel row in a display area and which pixel row is a still image display pixel row.

As described above, the video is displayed only on some screens, and the still image of the remaining parts can be displayed on only some screens by using a display panel driving method and a display device driving method to display an image at a low frequency, thereby reducing power consumption. have.

1 is a block diagram of a display device according to an exemplary embodiment of the present invention.
2 is a diagram illustrating regions of a display screen when a video is displayed only on a portion of a display screen.
3 and 4 are diagrams illustrating a data processing sequence according to an embodiment of the present invention.
5 is a diagram illustrating a waveform diagram for transmitting a signal according to an exemplary embodiment of the present invention.
6 is a graph illustrating a method of identifying a moving image part according to a result stored in a line buffer memory according to an exemplary embodiment of the present invention.
7 is a diagram illustrating a state in which a screen is displayed according to an embodiment of the present invention according to time.
8 is a graph illustrating a frequency for each pixel row for setting an image display frequency and displaying an image according to an exemplary embodiment of the present invention.
9 is a diagram illustrating a method of displaying an image according to a frequency set according to an embodiment of the present invention.
10 and 11 illustrate graphs of frequencies for each pixel row for setting a frequency for displaying an image and for displaying an image according to another exemplary embodiment of the present invention.
12 and 13 are graphs of frequencies for each pixel row displayed based on a frequency set according to another embodiment of the present invention.
14 is a diagram illustrating a step of setting a frequency for each pixel row according to an embodiment of the present invention.
15 to 18 are graphs illustrating examples of selecting representative values and weights according to embodiments of the present invention.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right over" but also when there is another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A display device according to an embodiment of the present invention will now be described in detail with reference to the drawings.

1 is a block diagram of a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a display panel according to an exemplary embodiment may include a display area 300 for displaying an image, a gate driver 400 for applying a gate voltage to a gate line of the display area 300, and a display area ( The data driver 500 applies a data voltage to the data line 300, and a signal controller 600 that controls the display area 300, the gate driver 400, and the data driver 500.

The display area 300 includes pixels PX arranged in a matrix. The display area 300 may be various flat panel display panels such as a liquid crystal display panel, an organic light emitting display panel, an electrophoretic display panel, an electrowetting display panel, and a plasma display panel. However, hereinafter, the display area 300 formed of the liquid crystal display panel will be described for convenience of description.

The display area 300 includes a plurality of gate lines (not shown as signal lines extending in the horizontal direction (first direction)) and a plurality of data lines (not shown as signal lines extending in the vertical direction (second direction)). And a plurality of gate lines and a plurality of data lines are insulated and crossed.

Each pixel PX includes a thin film transistor, a liquid crystal capacitor, and a storage capacitor. The control terminal of the thin film transistor is connected to one gate line, the input terminal of the thin film transistor is connected to one data line, and the output terminal of the thin film transistor is connected to one terminal of the liquid crystal capacitor and one terminal of the storage capacitor. The other terminal of the liquid crystal capacitor is connected to the common electrode, and the other terminal of the storage capacitor receives a sustain voltage Vcst applied from the signal controller 600.

In some embodiments, the channel layer of the thin film transistor may be amorphous silicon or polysilicon.

The plurality of data lines receive a data voltage from the data driver 500, and the plurality of gate lines receive a gate voltage from the gate driver 400.

The data driver 500 is connected to a plurality of data lines formed in an upper side or a lower side of the display panel 100 and extending in a vertical direction, and includes a plurality of data driver ICs 510. The plurality of data lines are divided and connected to the data driver IC 510. The data driver IC 510 selects a corresponding data voltage among the gray voltages generated by the gray voltage generator (not shown) and applies it to the data line. The data driver IC 510 may be formed on a flexible printed circuit film (FPC) and attached to a display panel.

The gate driver 400 alternately applies the gate on voltage and the gate off voltage to the plurality of gate lines, and the gate on voltage is sequentially applied to the plurality of gate lines. The gate driver 400 may include a plurality of gate driver ICs 410. In addition, the plurality of gate driver ICs 410 may be integrated on the left or right side of the display area 300 in the display panel. The gate driver 400 generates a gate voltage (gate on voltage and gate off voltage) by applying a voltage such as a clock signal, a scan start signal, and a low voltage corresponding to the gate off voltage, and sequentially gate-on voltages to the plurality of gate lines. Is applied.

The signal controller 600 controls the gate driver 400 and the data driver 500 by outputting a control signal, image data, and the like. In addition, the signal controller 600 according to an embodiment of the present invention analyzes the image data to be displayed to determine whether the image is a still image or a moving image, distinguishes an area for displaying a still image from an area for displaying a video, and displays a still image. The frequency to display and the frequency to display the video can be controlled to display the image. This will be described in detail below with reference to FIG. 3.

  In the above, the overall structure of the display device including the display panel 100 has been described.

Hereinafter, when a video is displayed in a part of the display area 300 and a still image is displayed in the remaining area using FIG. 2, the display area 300 is divided and described.

2 is a diagram illustrating regions of a display screen when a video is displayed only on a portion of a display screen.

2 illustrates an example in which a video is displayed in a portion of the display area 300 and a still image is displayed in the remaining portion. In this case, the display area 300 is largely divided into a video display area 302 and a still image display area 301-1, 301-2, and 301-3. First, the still image display regions 301-1 and 301-3 respectively positioned above and below the video display region 302 are display regions displaying still images, and are driven at a frequency lower than a general driving frequency (for example, 60 Hz). do. In one embodiment, the data voltage may be applied only once per frame and the applied voltage may be maintained for the remaining time. This is because the gate-on voltage applied to the gate line is controlled to be applied only once per frame. On the other hand, the still image display region 301-2 disposed on the left and right sides of the video display region 302 displays a still image because the gate line is shared with the video display region 302. Drive at the same frequency as the video display area 302 (hereinafter referred to as "video frequency"). That is, when the still image display area 301-2 is driven at 60 Hz, a still image is displayed, but a data voltage corresponding to 60 still images per second is applied to each pixel and refreshed. Accordingly, the still image display area 301-2 is also called a refresh area. Here, the video frequency may be the same as a general operating frequency for displaying an image in the case where both the still image and the moving image are moving images.

Hereinafter, the still image display area 301-2 and the moving image display area 302 sharing the gate line are also called moving image display pixel rows, and the pixel rows positioned above and below the moving image display area 302 are displayed on the still image display area. Also called an action. At this time, the video display pixel row is driven at a video frequency, and the still image display pixel row is driven at a frequency lower than the video frequency. However, even if the still image is displayed, the still image display region 301-2 sharing the gate line with the moving image display region 302 is driven at the moving image frequency.

In order to drive as described above, the signal controller 600 should determine whether the moving picture display area or the still image display area is present. This will be described with reference to FIGS. 3 to 5.

3 and 4 are diagrams illustrating a data processing sequence according to an embodiment of the present invention, and FIG. 5 is a diagram illustrating a waveform diagram for transmitting a signal according to an embodiment of the present invention.

3 and 4, it is determined whether the image is a still image by comparing data input to the signal controller 600 from the outside.

First, when data is input to the signal controller 600 from the outside (S10), the data input in the current frame (any n-th frame) and the data input in the previous frame (n-1 th frame) are compared (S20). do. The frame memory 610 of FIG. 4 is required to store data input to the previous frame (n-1 th frame). In addition, the comparator 620 of FIG. 4 is also required to compare the data input in the current frame (any n-th frame) and the data input in the previous frame (n-1th frame). Referring to FIG. 4, data input in the nth frame is input to the frame memory 610 and the comparator 620, and data input in the n−1 th frame, which is the previous frame, is stored in the frame memory 610, and then n The first frame (the current frame) is passed to the comparator 620. The comparator 620 compares the data input in the n-th frame and the data input in the n-1th frame for each line / pixel to determine whether the image is a moving image or a still image (S30). The comparator 620 outputs a result of determining whether the image is a moving image or a still image to the line buffer memory 625, and the line buffer memory 625 stores the result (S40). The output of the comparator 620 is composed of 2 bits (0 or 1). In the comparator 620 according to the present embodiment, 0 means a still image, and 1 means a video. In FIG. 5, values according to an example stored in the line buffer memory 625 are illustrated by dotted lines in the left graph. The left graph of FIG. 5 illustrates a result of comparing images according to an exemplary embodiment, in which two moving parts exist. Therefore, unlike the left graph of FIG. 5, the still image and the video may exist in various combinations. In addition, according to an embodiment, one of two bits stored in the comparator 620 may mean a still image, and 0 may mean a video.

The data driver 500 and the gate driver 400 are controlled based on the information thus identified to display a moving image and a still image (S50).

Referring to FIG. 5, a video portion divided by two dotted lines is identified as one video region as shown in the graph on the right, and the remaining portion displays a still image to display an image at a lower frequency than the video frequency. Display the video. According to the embodiment of FIG. 5, only one video display pixel row group exists in the display area 300 by operating the still image display pixel row existing between the two video display pixel rows in the same manner as the video display pixel row. The present invention is an embodiment in which the display operation is simplified in consideration of this. However, according to an exemplary embodiment, two moving image display pixel rows may be divided and a still image display pixel row therebetween may display a still image.

6 and 7 illustrate a method in which the signal controller 600 controls the data driver 500 and the gate driver 400 to display an image when the still image display pixel row and the video display pixel row are determined. Let's take a closer look at the example.

FIG. 6 is a graph illustrating a method of identifying a video part according to a result stored in a line buffer memory according to an exemplary embodiment of the present invention. FIG. 7 is a diagram illustrating a screen display according to an exemplary embodiment of the present invention. The figure is shown.

Referring to Figure 6 describes a method for controlling the gate driver 400 is as follows. In the case of having a moving picture frequency of 60 Hz, 60 images are displayed for 1 second (1 sec), and the vertical synchronization signal STV is generated 60 times. The period from one vertical sync signal STV until the next vertical sync signal STV is generated coincides with one frame, and a gate scan signal corresponding to the number of gate lines is generated during one frame. . The output enable (OE) signal controls the output of the gate scan signal. According to an embodiment of the present invention, when the output enable (OE) signal has a low value, the gate on voltage is output to the gate output, and the output enable (OE) signal is output. When the value is high, the gate-on voltage is not output.

Meanwhile, a method of controlling the data driver 500 will be described with reference to FIG. 6, and the data driver 500 may transmit the image data transmitted from the signal controller 600 only when the output enable signal OE has a low value. The data voltage is output to the data output, and screened so as not to output the data voltage when the OE signal has a high value. In the case of the data driver 500, even when the output enable OE signal has a high value, the gate-on voltage is not transmitted to the pixel even though the data voltage is output, but the voltage charged in the pixel does not change. There is a disadvantage in that power consumption occurs due to the operation of 500). Therefore, in the embodiment of FIG. 6, the power consumption is reduced by outputting the data voltage only when the output enable signal OE has a low value.

In FIG. 6, a section in which the output enable (OE) signal has a low value corresponds to a timing for operating the video display pixel row, and a section in which the output enable (OE) signal has a high value operates a still image display pixel row. Corresponds to the timing.

Meanwhile, in FIG. 6, sections in which the output enable OE signal has a low value for one frame are shown in the leftmost frame and the rightmost frame. Since the output enable signals all have a low value, this frame displays both the moving image display pixel row and the still image display pixel row. According to the waveform diagram of FIG. 6, it can be seen that the video display and the still image display are both performed once every second.

In order to make it easier to grasp conceptually the case of displaying an image as shown in FIG.

That is, in FIG. 7, the frame displaying the entire image is displayed at a frequency of 1 Hz (once per second), and the video display pixel rows are displayed 59 times at a frequency of 60 Hz (60 times per second). Is shown. 7 also clearly shows that the video display pixel row includes not only the video display region 302 but also the still image display region 301-2 disposed on the left and right sides of the video display region 302. . Since the still image display area 301-2 included in the moving image display pixel row displays a still image, the still image display area 301-2 continues to display the same screen, and is simply refreshed.

6 and 7 illustrate an embodiment in which a moving image frequency is 60 Hz and a still image display frequency is fixed at 1 Hz. However, according to an exemplary embodiment, the still image display frequency may be different or may vary for each still image display pixel row.

This will be described with reference to FIGS. 8 to 14.

8 is a graph illustrating a frequency for each pixel row for setting an image display frequency and displaying an image according to an exemplary embodiment of the present invention.

In FIG. 8, a graph is shown on the right side, and the axis in the vertical direction of the graph represents a row of pixels, and corresponds to the display area 300 shown on the left side. That is, the pixel rows corresponding to the video display pixel rows 302 and 301-2 are shown by dotted lines. On the other hand, the axis of the horizontal direction of the graph represents the frequency, and indicates that 60Hz is a video frequency. Also, the optimal still image display frequency Wall_Hz means an optimal still image display frequency for analyzing data in the still image display region to have a minimum power consumption. The optimum still image display frequency Wall_Hz is determined according to the image pattern and the characteristics of the liquid crystal capacitor and the sustain capacitor in the pixel. According to an exemplary embodiment, an image pattern of a still image display pixel row (corresponding to 301-1 and 301-3) may be analyzed, and the optimal still image display frequency Wall_Hz may be determined from the lookup table LUT based on the result. have. Analysis of the image pattern will be described in more detail with reference to FIGS. 15 to 18 below.

Also, in the present embodiment, the low frequency (U_Hz; hereinafter referred to as the upper still image display frequency) in the upper still image display region 301-1 of the moving image display pixel row and the lower still image display region 301-3 of the moving image display pixel row Low frequency (L_Hz) (hereinafter referred to as lower still image display frequency) is also analyzed for image patterns in each region to identify each low frequency. According to an exemplary embodiment, the image pattern of each still image display pixel row is analyzed and based on the result, the still image display frequency (U_Hz) and the still image display frequency (L_Hz) of the upper region in the lookup table (LUT). Can be identified. Analysis of the image pattern will be described in more detail with reference to FIGS. 15 to 18 below.

The optimum still image display frequency (Wall_Hz), the still image display frequency (U_Hz) of the upper region, and the still image display frequency (L_Hz) of the lower region calculated by analyzing the image patterns in the still image display region in the upper and lower portions of the moving image display pixel row. ) May be arranged in various orders. (Refer to FIGS. 12 and 13) However, in FIG. 8, when the frequency order is arranged from the smallest to the largest, the optimal still image display frequency (Wall_Hz), the still image display frequency (U_Hz) of the upper region, and the still image of the lower region are shown. The case of the display frequency L_Hz is shown.

First, since the optimal still image display frequency (Wall_Hz) is an optimal frequency to represent the minimum power, a problem may occur in the image quality when using a frequency lower than this. Therefore, do not display still images at lower frequencies. In FIG. 8, since the still image display frequency (U_Hz) of the upper region and the still image display frequency (L_Hz) of the lower region are both greater than the optimal still image display frequency (Wall_Hz), the still image display frequency (U_Hz) and the lower region of the upper region are shown in FIG. 8. An image may be displayed in accordance with the still image display frequency L_Hz.

At this time, as shown in the graph of FIG. 8, the still image display frequencies of the first pixel row and the last pixel row farthest from the moving image display pixel rows are respectively displayed as the still image display frequency (U_Hz) of the upper region and the still image display frequency of the lower region ( L_Hz). Thereafter, the still image display frequency from the first and last pixel row to the moving image display pixel row is gradually increased to vary to 60 Hz in the moving image display pixel row. In the exemplary embodiment of the present invention, the entire upper still image display region 301-1 is driven at the still image display frequency (U_Hz) of the upper region, and the entire lower still image display region 301-3 is displayed in the still image of the lower region. Although driving at the frequency (L_Hz) may be ideal in terms of power consumption, as shown in FIG. 8, when a different operating frequency is set for each pixel row even in a still image display pixel row, a video display that may occur around a video display pixel row And still image display difference has the advantage of not being visually recognized.

As described above, how to drive the still image display frequency for each still image display pixel row will be described with reference to FIG. 9.

9 illustrates a method of displaying an image according to a frequency set according to an embodiment of the present invention.

As shown in Fig. 9, this is realized by adjusting still image display pixel rows displayed for each frame by using an output enable (OE) signal.

That is, as shown in FIG. 9, the gate clock signal CPV is applied to all the pixel rows within one frame, which is a period after the generation of one vertical synchronization signal STV and before the next vertical synchronization signal STV. It is applied to output a gate-on voltage. Here, the gate clock (CPV) signal is used to generate the gate-on voltage in the gate driver 400.

However, in the exemplary embodiment of the present invention, even though the gate clock CPV signal is applied to all the pixel rows, the actual gate clock applied to the actual gate driver 400 may be screened by using the output enable (OE) signal. As shown in FIG. 9, the CPV ') signal is output only in the portion where the output enable signal OE has a low value and is not output in the remaining portion.

In FIG. 9, the length of the section s having a low value in each frame of the output enable OE signal is changed. By changing the length of the row section s of the output enable OE signal, the still image display frequency is changed for each still image display pixel row.

That is, in FIG. 9, the length of the row section s of the output enable OE signal is longer from the left frame to the right frame. As a result, more pixel rows are applied to the data voltage in the corresponding frame. That is, although the data voltage is applied only to the video display pixel row in the left frame, the data voltage is applied to the still image display pixel row above and below the video display pixel row to be refreshed as it moves to the right frame. do. In addition, the number of still image display pixel rows to which a data voltage is applied is increasing toward the right frame. In this way, since the video display pixel row is displayed in every frame, an image is displayed at the video frequency, and a still image display pixel row adjacent to the video display pixel row is more than a still image display pixel row far from the video display pixel row. Since the still image is displayed in many frames, it can be seen that the still image display frequency is larger.

In addition, when the length of the row section s of the output enable signal is adjusted to correspond to the frequency of each pixel row in the graph of FIG. 8, a video and a still image may be displayed at the display frequency according to the graph of FIG. 8. To be able.

According to an exemplary embodiment, the closer the still image display frequency is to the moving image display pixel row, the higher the frequency by displaying the still image in more frames.

Further, according to an exemplary embodiment, in determining a still image display frequency, predetermined pixel rows may be divided into blocks, and still image frequencies may be determined for each corresponding block.

This embodiment is illustrated in FIGS. 10 and 11.

10 and 11 illustrate graphs of frequencies for each pixel row for setting an image displaying frequency and displaying an image according to another exemplary embodiment of the present invention.

10 and 11 correspond to FIG. 8. In the embodiment of FIG. 8, since the still image display frequency is determined for each pixel row, the still image display frequency must be stored for each pixel row, and thus a large amount of storage space (eg, LUT or memory) is required.

10 and 11 illustrate embodiments for reducing storage space.

First, FIG. 10 illustrates an embodiment in which a pixel row in a display panel is divided into a plurality of blocks, and a still image display frequency in the block is set to a constant value.

In the embodiment of FIG. 10, the upper region is divided into seven pixel row blocks, and the lower region is divided into four blocks.

Seven pixel row blocks in the upper region have different still image display frequencies, and all pixel rows in the same pixel row block display still images at the same still image display frequency. The seven pixel row blocks have a higher still image display frequency as they are closer to the moving image display pixel rows, and have a value between the still image display frequency (U_Hz) and the moving image display frequency (60 Hz) of the upper region.

Four pixel row blocks in the lower region have different still image display frequencies, and all pixel rows in the same pixel row block display still images at the same still image display frequency. The four pixel row blocks have a higher still image display frequency as they are closer to the moving image display pixel rows, and have a value between the still image display frequency (L_Hz) and the moving image display frequency (60 Hz) of the lower region.

Each of the pixel row blocks of the upper region and the lower region may include the same number of pixel rows, or may include different number of pixel rows.

Meanwhile, in the embodiment of FIG. 11, a plurality of still image display frequencies are determined, and pixel row blocks are divided based on pixel rows corresponding to the still image display frequencies. Then, each pixel row block in the upper region causes one of the still image display frequency (U_Hz), the moving image display frequency (60 Hz) and the predetermined plurality of still image display frequencies of the upper region to be the maximum and minimum still image display frequencies, respectively. do. A pixel row belonging to a pixel row block having a maximum value and a minimum value determines a still image display frequency for each pixel row by interpolation. The still image display frequency displayed by each pixel row in one pixel row block may have a linearly increasing relationship.

On the other hand, each pixel row block of the lower region causes one of the still image display frequency (L_Hz), the video display frequency (60Hz) and the plurality of fixed still image display frequencies of the lower region to be the maximum and minimum still image display frequencies, respectively. do. A pixel row belonging to a pixel row block having a maximum value and a minimum value determines a still image display frequency for each pixel row by interpolation. The still image display frequency displayed by each pixel row in one pixel row block may have a linearly increasing relationship.

According to an exemplary embodiment, the plurality of still image display frequencies may be preset values, or may be divided into pixel row blocks based on pixel rows displaying a predetermined still image display frequency, or the pixel row blocks may be determined based on a specific specific pixel row. In this case, the still image display frequency of the corresponding pixel row may be used as it is.

Hereinafter, a graph of display frequency for each pixel row according to another embodiment will be further described with reference to FIGS. 12 and 13.

12 and 13 are graphs of frequencies for each pixel row displayed based on a frequency set according to another embodiment of the present invention.

In FIG. 12, when the still image display frequency (Wall_Hz) is greater than the still image display frequency (U_Hz) of the upper region and the still image is displayed in the upper region, the still image is displayed with a frequency less than the optimal still image display frequency (Wall_Hz). I never do that. In FIG. 12, the portion from the still image display frequency (U_Hz) to the optimum still image display frequency (Wall_Hz) in the upper region is shown by a dotted line, clearly indicating that the corresponding frequency is not used.

Meanwhile, in FIG. 12, all values below the optimal still image display frequency Wall_Hz are set while the frequency is increased in a curved form from the still image display frequency U_Hz in the upper region to the moving image frequency (60 Hz in this embodiment). In this embodiment, the optimal still image display frequency (Wall_Hz) is set.

However, according to an exemplary embodiment, the frequency may be set to increase in a curved form from the optimal still image display frequency Wall_Hz to the video frequency, unlike FIG. 12.

FIG. 13 illustrates a case where the optimum still image display frequency Wall_Hz and the still image display frequency U_Hz in the upper region have the same value. 13, the frequency is set to increase in a curved form from the still image display frequency (U_Hz) to the video frequency (60 Hz) of the upper region. In addition, according to an exemplary embodiment, the frequency may be set to be maintained at the same frequency from the still image display frequency U_Hz in the upper region to a certain pixel row, and then increase in a curved form until the video frequency. (See curve ②)

In addition to FIGS. 8, 12, and 13, various graphs may be drawn by the calculated still image display frequency (Wall_Hz), the still image display frequency (U_Hz) of the upper region, and the still image display frequency (L_Hz) of the lower region. . In particular, the still image display frequency L_Hz of the lower region may be smaller than the still image display frequency U_Hz of the upper region or smaller than the optimal still image display frequency Wall_Hz.

In addition, the shape of the curve increasing from the calculated still image display frequency (U_Hz) of the upper region and the still image display frequency (L_Hz) of the lower region to the video frequency may vary. It may vary depending on characteristics and the like. In addition, the lookup table may store information about an increasing value of a curved shape or an increasing value between pixel rows.

Hereinafter, the step of determining the frequency for the pixel row according to an embodiment of the present invention will be described more clearly with reference to FIG. 14.

14 is a diagram illustrating a step of setting a frequency for each pixel row according to an embodiment of the present invention.

The block diagram illustrated in FIG. 14 illustrates a driving frequency determiner 630 included in the signal controller 600.

First, when image data is input to the signal controller 600, the input image data is transferred to the driving frequency determiner 630. The image data input to the driving frequency determiner 630 is first transferred to the optimum still image display frequency extractor 631 to calculate the optimum still image display frequency Wall_Hz. The optimum still image display frequency extractor 631 calculates a representative value through the image patterns of the still image display pixel rows 301-1 and 301-3 and selects a corresponding optimal value from the lookup table LUT based on the calculated representative value. Select still image display frequency (Wall_Hz). Here, calculating the representative value will be described in more detail with reference to FIGS. 15 to 18 below.

The image data input to the driving frequency determiner 630 is also input to the position determiner 632. The position determiner 632 determines to which pixel of the display panel the image data continuously input is actually applied. Data is classified for each pixel row based on the result determined as described above, and the data of the divided pixel rows are input to the still image / video determination unit 633. The still image / movie determination unit 633 compares the image data of the current frame (any n-th frame) with the image data of the previous frame (n-1th frame) based on the pixel row, respectively, to determine whether the image data is a still image. Determine if the video is a video. The still image / video determination unit 633 may include the frame memory 610 and the comparator 620 of FIG. 4 to compare the image data of the previous frame (n−1 th frame).

The result of determining whether each pixel row is a still image or a moving image is applied to the moving image display pixel row setting unit 634 so that a portion of the display area 300 is a moving image display pixel row 302 and which portion is a still image display. Set whether this is an action.

When the specification of each pixel row is set as described above, the image data is transferred to the representative value calculator 635 and the weight calculator 636 to calculate the representative value and the weight for each pixel row.

The calculated representative value and the weight are multiplied with each other, and then, using the multiplied result value, the driving frequency for each pixel row is selected in the lookup table (LUT) 637, and in addition, the still image display frequency (L_Hz) and the upper portion of the lower region are selected. The still image display frequency (U_Hz) of the area is also selected. The lookup table (LUT) 637 stores frequency values for the product of the representative value and the weight. In some embodiments, the lookup table 637 may store frequency values for representative values.

The optimal still image display frequency (Wall_Hz), the driving frequency for each pixel row, the still image display frequency (L_Hz) of the lower region, and the still image display frequency (U_Hz) of the upper region are selected as the driving frequency. The driving frequency for each pixel row is determined by applying to the unit 638 to be modified. That is, the driving frequency determiner 638 determines whether the frequency determined in the lookup table is appropriate and determines the final driving frequency. When the driving frequency determined in this way is shown as a graph, it may be displayed as a graph as shown in FIGS. 8, 12, and 13.

The image is displayed by adjusting the size and timing of the row section of the output enable (OE) signal as shown in FIG. 9 according to the driving frequency for each pixel row.

In FIG. 14, the driving frequency is determined based on the representative value and the weight of each pixel row. Hereinafter, some representative examples of various embodiments of determining the representative value and the weight will be described.

15 to 18 are graphs illustrating examples of selecting representative values and weights according to embodiments of the present invention.

First, FIG. 15 shows an example of calculating the representative gradation value using the representative value.

In FIG. 15, the result of calculating the number of pixels (# of pxls) representing each gray level in one pixel row or an area for which a representative value is to be calculated is illustrated in a graph for easy viewing. Among the values that can be selected as the representative value, the average value Avg, the peak value including the largest number of pixels, the maximum gray level value Max, and the like are displayed. These are all gray scale values.

On the other hand, Fig. 16 shows that the luminance value (Lum.) Can be used as the representative value instead of the gradation value. As shown in FIG. 15, when a representative gray value is determined, the luminance value according to the representative gray value is used as the representative value. The curve shown in FIG. 16 is a gamma curve.

17 and 18 show examples of calculating weights, respectively.

First, FIG. 17 illustrates an example in which a weight is large when the representative gray value is an intermediate gray value, and a weight is small when the representative gray value is close to the maximum or minimum value. Such weight is an example to prevent flicker from being seen by the user. That is, when the luminance displayed by the pixel is low or high, the user can easily feel the luminance change as the gray scale changes, so the weight is reduced to make a small value to reduce the change. It gives a lot to make a large value. In FIG. 17, the weight is provided based on the representative gray value, but it is also possible to provide the weight based on the luminance value. At this time, the weight is large when the luminance value has an intermediate luminance value, and the weight is small when the luminance value is small or large.

18 illustrates an example in which more weight is provided as the area becomes larger after calculating an area corresponding to the representative value. Such an example provides a weight because there are many pixels corresponding to the representative value, and a large weight may be given when the number of pixels corresponding to the representative value is large.

Meanwhile, according to an exemplary embodiment, both weights of FIGS. 17 and 18 may be included and used. In this case, a frequency may be selected based on a value obtained by multiplying two representative weights by two weights.

As described above, various examples of the representative value and the weight have been described with reference to FIGS. 15 to 18, and the reference value for selecting the frequency in the lookup table 637 is changed as the representative value and the weight are changed. And weight may be selected and used.

According to the exemplary embodiment of the present invention, it is advantageous to operate the still image display pixel row at a low frequency as much as possible to reduce power consumption. However, in such low frequency driving, display quality may be deteriorated due to current leakage in an off state generated in the thin film transistor included in the pixel. Therefore, it is necessary to display an image at a low frequency in the absence of display quality in accordance with the characteristics of the pixel, and this concept is included in the optimum still image display frequency (Wall_Hz). In addition, when the current leakage in the off state is reduced in the thin film transistor, driving of the low frequency is possible, and thus, the thin film transistor formed in the pixel of the display device may use an oxide semiconductor as a channel layer. That is, since the thin film transistor using the oxide semiconductor as the channel layer has less leakage current in the off state than in the case of using the amorphous silicon as the thin film transistor, lower low frequency driving may be possible. However, even when the thin film transistor including amorphous silicon is used, low power consumption can be driven by appropriately adjusting the low frequency.

In some embodiments, the thin film transistor may use polysilicon as a channel layer.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

300: display area 301-1, 301-2, 301-3: still image display area
302: Video display area 400: Gate driver
410: gate driver IC 500: data driver
510: data driving IC 600: signal control unit
610: frame memory 620: comparator
625: line buffer memory 630: driving frequency determiner
631: display frequency extractor 632: position determiner
633: Still image / movie determination unit
634: Video display pixel row setting unit
635: representative value calculator 636: weight calculator
637: lookup table 638: driving frequency determination unit

Claims (20)

Comparing the image data of the current frame (random n-th frame) input from the outside with the image data of the previous frame (n-1th frame) and dividing the image data into a moving image display pixel row and a still image display pixel row; And
Driving the video display pixel row and the still image display pixel row
Including,
The video display pixel row is driven at a video frequency,
The video display pixel row includes a first video display pixel row and a second video display pixel row positioned in different pixel rows.
The still image display pixel row may include a first still image display pixel row positioned between the first video display pixel row and the second video display pixel row, and the first video display pixel row and the second video display pixel row. A second still image display pixel row not located between the rows;
The second still image display pixel row is driven at a still image display frequency lower than the video frequency;
The first still image display pixel row is driven at the video frequency.
Method of driving the display device. In claim 1,
And a plurality of second still image display pixel rows are driven at least two or more of the still image display frequencies. In claim 2,
And a pixel row adjacent to the video display pixel row among the plurality of second still image display pixel rows is driven at a higher frequency than a distant pixel row. In claim 1,
And the video display pixel row includes a video display area and a refresh area sharing a gate line with the video display area. In claim 1,
Comparing the image data of the current frame input from the outside with the image data of the previous frame to divide the video display pixel row and the still image display pixel row
Outputting the image data of the previous frame stored in the frame memory to the comparator while storing the image data of the current frame; And
And the comparator comparing the image data of the current frame with the image data of the previous frame. In claim 5,
And the comparator compares the image data of the current frame and the image data of the previous frame for each pixel row to display a still image or a video image for each pixel row. In claim 6,
And storing the result of the comparison in the comparator in a line buffer memory. In claim 7,
The data output from the comparator and stored in the line buffer memory are 2-bit data, 0 represents a still image, and 1 represents a moving image. In claim 1,
Driving the video display pixel row at a video frequency and driving the second still image display pixel row at a still image display frequency lower than the video frequency.
A method of driving a display device screening a gate-on voltage to be transmitted or not to a gate line using an output enable signal. In claim 9,
And screening the data enable signal so that no data voltage is applied when the gate-on voltage is not applied using the output enable signal. In claim 1,
The second still image display pixel row may be driven at a still image display frequency lower than the video frequency.
Determining a first still image display frequency for the minimum power consumption;
Determining an upper still image display frequency in an upper still image display region located above the moving image display pixel row, and
And determining a lower still image display frequency in a lower still image display area located below the moving image display pixel row. In claim 11,
Identifying the first still image display frequency
And a representative value is calculated through the image pattern of the still image display pixel row, and the first still image display frequency is selected from a lookup table based on the calculated representative value. In claim 12,
Identifying the upper still image display frequency, and determining the lower still image display frequency include: calculating a representative value of a corresponding pixel row; And
And selecting the upper still image display frequency and the lower still image display frequency in the lookup table based on the calculated representative value. In claim 13,
Determining the upper still image display frequency, and determining the lower still image display frequency further include calculating a weight of the corresponding pixel row.
And an upper still image display frequency and a lower still image display frequency in the lookup table based on a value obtained by multiplying the representative value by the weight instead of the representative value. In claim 11,
And a frequency gradually increasing from the upper still image display frequency and the lower still image display frequency to the moving image frequency. The method of claim 15,
And a frequency increasing in a curved form from the upper still image display frequency and the lower still image display frequency to the moving image frequency. In claim 11,
And the operation frequency for displaying the pixel row when the upper still image display frequency or the lower still image display frequency is lower than the first still image display frequency is operated at the first still image display frequency. Display area for displaying an image,
A gate line and a data line positioned in the display area;
A gate driver electrically connected to the gate line,
A data driver electrically connected to the data line, and
A signal controller for controlling the gate driver and the data driver;
The signal control unit,
A still image / movie determination unit for dividing image data input from the outside into a moving image display pixel row or a still image display pixel row, and
A driving frequency determiner configured to determine a final driving frequency of the moving image display pixel row and the still image display pixel row;
The video display pixel row is driven at a video frequency,
The video display pixel row includes a first video display pixel row and a second video display pixel row positioned in different pixel rows.
The still image display pixel row may include a first still image display pixel row positioned between the first video display pixel row and the second video display pixel row, and the first video display pixel row and the second video display pixel row. A second still image display pixel row not located between the rows;
The second still image display pixel row is driven at a still image display frequency lower than the video frequency;
The first still image display pixel row is driven at the video frequency.
Display device. The method of claim 18,
And a plurality of said second still image display pixel rows are driven at least two or more said still image display frequencies. The method of claim 19,
And a pixel row close to the video display pixel row among the plurality of second still image display pixel rows is driven at a higher frequency than a distant pixel row.

Images