KR102319311B1 - Display device and driving method thereof - Google Patents

Abstract

The present invention comprises the steps of comparing image data of a current frame (arbitrary n-th frame) input from the outside with image data of a previous frame (n-1 th frame) and dividing the image data into a moving picture display pixel row and a still image display pixel row; and driving the moving image display pixel row at a moving image frequency, and driving the still image display pixel row at a still image display frequency lower than the moving image frequency, wherein the plurality of still image display pixel rows includes at least two of the still images. A method of driving a display device driven at an image display frequency and a driving device of the display device are provided.

Description

DISPLAY DEVICE AND DRIVING METHOD THEREOF

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

A display device includes various types of flat panel display devices such as a liquid crystal display device, an organic light emitting display device, an electrophoretic display device, and a plasma display device. includes the system.

As the bandwidth of data transmission increases in the display field, high-speed data transmission between driving chips, boards, and systems is required. Accordingly, LVDS (Low Voltage Differential Signaling) has been widely used. When data is transmitted using the LVDS method, the operating speed can be improved, power consumption is reduced because a low voltage is used, and the EMI problem and manufacturing cost can be reduced.

The image displayed by the display device includes a moving image that largely changes every moment and a still image that is still for a certain period of 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, the PSR technology is applied only to a data transfer method in which bidirectional communication is possible.

In addition, as the display device becomes larger, the cases of using only a part of a screen are increasing, and even when a moving image is displayed only in the corresponding area and a still image is displayed in the remaining part, all pixels must be operated at a predetermined frequency. Therefore, there is a disadvantage that power consumption cannot be reduced even when a video is displayed only in a partial area.

An object of the present invention is to provide a method for driving a display device and a driving device for a display device that displays a moving image on only a part of the screen while displaying an image with a low frequency on the rest of the still image.

In order to solve this problem, in a method of driving a display device according to an embodiment of the present invention, image data of a current frame (arbitrary n-th frame) input from the outside is compared with image data of a previous frame (n-th frame). dividing a moving picture display pixel row and a still image display pixel row; and driving the moving image display pixel row at a moving image frequency, and driving the still image display pixel row at a still image display frequency lower than the moving image frequency, wherein the plurality of still image display pixel rows includes at least two of the still images. Drive at the video display frequency.

Among the plurality of still image display pixel rows, a pixel row adjacent to the moving image display pixel row may be driven at a higher frequency than that of a distant pixel row.

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

The step of comparing the image data of the current frame input from the outside with the image data of the previous frame and dividing the image data of the current frame into a moving image display pixel row and a still image display pixel row includes storing the image data of the current frame in the frame memory. outputting the image data of the 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 moving image is displayed for each pixel row.

The method may further include storing a result compared by the comparator 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 moving image.

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

In the step of driving the moving image display pixel row at the moving image frequency and the still image display pixel row at a still image display frequency lower than the moving image frequency, a gate-on voltage is transmitted to the gate line using an output enable signal. It can be screened as much as possible.

When the gate-on voltage is not applied, the data voltage may be screened using the output enable signal.

The driving of the still image display pixel row at a still image display frequency lower than the moving image frequency may include: identifying an optimal still image display frequency; identifying an upper still image display frequency in an upper still image display area positioned above the moving picture pixel row, and determining a lower still image display frequency in a lower still image display area positioned lower than the moving image pixel row may include the step of

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 optimal still image display frequency from a lookup table based on the calculated representative value.

The determining of the upper still image display frequency and the determining of the lower still image display frequency may 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 from the lookup table based on the calculated representative value.

The determining of the upper still image display frequency and the determining of the lower still image display frequency further include calculating a weight of the corresponding pixel row, and adding 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 from the lookup table based on the multiplication value.

A frequency may gradually increase from the upper still image display frequency and the lower still image display frequency to the moving image 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 moving image frequency.

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

A driving apparatus for a display device according to an embodiment of the present invention includes a still image/video determiner that divides image data input from the outside into a moving image 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 look-up table storing frequency values for the representative values, and a driving frequency determining unit determining whether a frequency determined in the look-up table is appropriate and determining the final driving frequency as a final driving frequency, wherein the moving picture display pixel row is a moving picture frequency and the still image display pixel rows are driven with a still image display frequency lower than the moving image frequency, and the plurality of still image display pixel rows are driven with at least two or more still image display frequencies.

The method may further include a weight calculating unit that multiplies the representative value and assigns a weight, and selects a frequency from the lookup table based on a value obtained by multiplying the representative value and the weight.

The method may further include an optimal still image display frequency extractor that calculates a representative value through the image pattern of the still image display pixel row and selects a corresponding optimal still image display frequency from the lookup table based on the calculated representative value.

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

The representative value may be one of an average value, a peak value, or a maximum grayscale value.

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

The weight may be calculated by calculating an area corresponding to the representative value, so that the larger the area, the greater the weight may be provided.

The display device may further include a position determining unit determining which pixel of the display panel to which continuously input image data is actually applied, and an output of the position determining unit may be transmitted to the still image/moving image determining unit.

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

As described above, it is possible to reduce power consumption by displaying the video on only some screens by using the display panel driving method and the driving device of the display panel to display the still image on some screens while displaying the image at a low frequency for the rest of the screen. have.

1 is a block diagram of a display device according to an exemplary embodiment of the present invention.
FIG. 2 is a diagram illustrating divided regions of the display screen when a moving picture is displayed only on a partial region of the 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 embodiment of the present invention.
6 is a graph illustrating a method of recognizing a video part according to a result stored in a line buffer memory according to an embodiment of the present invention.
7 is a diagram illustrating a screen display according to time according to an embodiment of the present invention.
8 is a diagram illustrating a graph of frequencies for each pixel row for setting a frequency for displaying an image and for displaying an image according to an embodiment of the present invention.
9 is a diagram illustrating a method of displaying an image according to a set frequency according to an embodiment of the present invention.
10 and 11 are diagrams showing graphs of frequencies for each pixel row for setting a frequency for displaying an image and displaying an image according to another 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 an embodiment of the present invention.

With reference to the accompanying drawings, the embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein.

In order to clearly express various layers and regions in the drawings, the thicknesses are enlarged. Throughout the specification, like reference numerals are assigned to similar parts. When a part of a layer, film, region, plate, etc. is said to be “on” another part, it includes not only cases where it is “directly on” another part, but also cases where there is another part in between. Conversely, when we say that a part is "just above" another part, we mean that there is no other part in the middle.

A display device according to an exemplary 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 includes 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 of the 300 , the display area 300 , the gate driver 400 , and the signal controller 600 controls the data driver 500 .

The display area 300 includes pixels PX arranged in a matrix form. Here, 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, for convenience of description, the display area 300 made of the liquid crystal display panel will be mainly described.

In the display area 300 , 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)) are formed in the display area 300 . 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. A control terminal of the thin film transistor is connected to one gate line, an input terminal of the thin film transistor is connected to one data line, and an 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 the 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 formed on the upper or lower side of the display panel 100 , is connected to a plurality of data lines extending in the vertical direction, and includes a plurality of data driver ICs 510 . The plurality of data lines are divided and connected to the data driving IC 510 . The data driving IC 510 selects a corresponding data voltage from among the gray voltages generated by the gray voltage generator (not shown) and applies it to the data line. The data driving IC 510 may be formed on a flexible printed circuit film (FPC) and attached to the display panel.

The gate driver 400 alternately applies a gate-on voltage and a 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 . Also, the plurality of gate driving 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 receiving a clock signal, a scan start signal, and a voltage such as a low voltage corresponding to a gate-off voltage, and sequentially applies a gate-on voltage to a plurality of gate lines. to authorize

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 the embodiment of the present invention analyzes the image data to be displayed to determine whether it is a still image or a moving image, divides an area in which to display a still image and an area in which to display a moving image, and displays the still image. It is possible to control to display an image by distinguishing the frequency to be used and the frequency to display the video. This will be described in detail below in FIG. 3 .

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

Hereinafter, when a moving image is displayed on a part of the display area 300 and a still image is displayed on the remaining area using FIG. 2 , the display area 300 will be described separately.

FIG. 2 is a diagram illustrating divided regions of the display screen when a moving picture is displayed only on a partial region of the display screen.

2 illustrates an example in which a moving image 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 moving image display area 302 and still image display areas 301-1, 301-2, and 301-3. First, the still image display regions 301-1 and 301-3 respectively positioned above and below the moving image display region 302 are display regions for displaying still images and are driven at a frequency lower than a normal driving frequency (eg, 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 rest of the 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, among them, the still image display area 301-2 disposed on the left and right sides of the moving picture display area 302 displays a still image because it shares a gate line with the moving image display area 302, but in reality It drives at the same frequency as the video display area 302 (hereinafter referred to as a 'video frequency'). That is, the still image display area 301 - 2 displays a still image when driven at 60 Hz, but is refreshed by applying a data voltage corresponding to a still image 60 times per second to each pixel. Accordingly, the still image display area 301 - 2 is also referred to as a refresh area. Here, the moving picture frequency may be the same as a normal operating frequency for displaying an image when both are moving images without distinction between still images and moving images.

Hereinafter, the still image display area 301-2 and the moving picture display area 302 sharing the gate line are also referred to as moving picture display pixel rows, and the pixel rows located above and below the moving picture display area 302 are the still image display images. It is also called succulent. In this case, the moving image display pixel row is driven at the moving image frequency, and the still image display pixel row is driven at a frequency lower than the moving image frequency. However, even when a still image is displayed, the still image display area 301 - 2 sharing the gate line with the moving image display area 302 is driven at the video frequency.

In order to drive as described above, the signal controller 600 needs to determine whether it is a moving image display region or a still image display region. This will be looked at 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 from the outside to the signal controller 600 .

First, when data is input from the outside to the signal controller 600 ( S10 ), data input to the current frame (an arbitrary n-th frame) is compared with data input to a previous frame (an n-th frame) ( S20 ) do. The frame memory 610 of FIG. 4 is required to store data input in the previous frame (n-1 th frame). In addition, the comparator 620 of FIG. 4 is also needed to compare data input to the current frame (an arbitrary n-th frame) with data input to a previous frame (an n-th frame). Referring to FIG. 4 , data input to the nth frame is input to the frame memory 610 and the comparator 620 , and data input to the n−1th frame, which is the previous frame, is stored in the frame memory 610 and then stored in the nth frame. It is transmitted to the comparator 620 in the second frame (the current frame). The comparator 620 compares the data input to the n-th frame with the data input to the n-1 th frame for each line/pixel to determine whether it is a moving image or a still image (S30). The comparator 620 outputs a result of determining whether it 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 consists of 2 bits (0 or 1), and in the comparator 620 according to the present embodiment, 0 means a still image and 1 means a moving picture. In FIG. 5 , a value according to one example stored in the line buffer memory 625 is shown by a dotted line on the left graph. The graph on the left of FIG. 5 shows the results of comparing images according to one embodiment, and a case in which the moving picture part exists in two places. Therefore, unlike the left graph of FIG. 5 , still images and moving images may exist in various combinations. In addition, according to an embodiment, 1 of the 2 bits stored in the comparator 620 may mean a still image, and 0 may mean a moving picture.

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

According to FIG. 5, the moving picture part divided by two dotted lines is identified as one moving picture area as shown in the graph on the right, and the remaining part displays a still image to display the image at a frequency lower than the moving picture frequency, and in the moving picture area, the moving picture frequency is displayed. Display the video. According to the embodiment of FIG. 5 , a still image display pixel row existing between two moving image display pixel rows is operated like a moving image display pixel row, so that only one moving image display pixel row group exists in the display area 300 . This is an embodiment in which the display operation is simplified by understanding that it is However, according to an exemplary embodiment, it may be divided into two moving picture display pixel row groups, and a still image display pixel row between them may display a still image.

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

6 is a graph illustrating a method of recognizing a video part according to a result stored in a line buffer memory according to an embodiment of the present invention, and FIG. 7 is a time division of a screen display according to an embodiment of the present invention It is a drawing shown.

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

Meanwhile, the method of controlling the data driver 500 is referred to FIG. 6 , and the data driver 500 transmits image data transmitted from the signal controller 600 only when the output enable (OE) signal has a low value. A data voltage is output as a data output, and when the output enable (OE) signal has a high value, it is screened so that the data voltage is not output. In the case of the data driver 500 , even when the output enable (OE) signal has a high value, even when the data voltage is output, the gate-on voltage is not transmitted to the pixel, so the voltage charged in the pixel does not change, but in this case, the data driver ( 500) has a disadvantage in that power consumption is generated due to the operation. Therefore, in the embodiment of FIG. 6 , power consumption is reduced by outputting the data voltage only when the output enable (OE) signal has a low value.

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

Meanwhile, in FIG. 6 , a period in which the output enable (OE) signal has all low values during one frame is illustrated in the leftmost frame and the rightmost frame. Since both the output enable (OE) signals have low values, this is a period in which both a moving image display pixel row and a still image display pixel row are displayed in a corresponding frame. According to the waveform diagram of FIG. 6 , it can be seen that display of a moving image and display of a still image are performed once every second according to an embodiment.

In order to make it easier to conceptually understand the case of displaying an image as shown in FIG. 6, it is illustrated as shown in FIG. 7 .

That is, in FIG. 7 , the frame displaying the entire image is displayed at a frequency of 1 Hz (once per second), and in the meantime, the video display pixel row is displayed at a frequency of 60 Hz (60 times per second) 59 times in total. is shown. Also, in Fig. 7, it is clearly shown that the moving image display pixel row includes not only the moving image display region 302 but also the still image display regions 301-2 arranged to the left and right of the moving image display region 302. . The still image display area 301 - 2 included in the moving picture display pixel row displays a still image, so it continuously displays the same screen and is simply refreshed.

In the embodiments of FIGS. 6 and 7 , an embodiment in which the moving image frequency is 60 Hz and the still image display frequency is fixed to 1 Hz has been described. 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 diagram illustrating a graph of frequencies for each pixel row for setting a frequency for displaying an image and for displaying an image according to an embodiment of the present invention.

In FIG. 8 , a graph is shown on the right side, and an axis in the vertical direction of the graph indicates a pixel row and is shown to correspond to the display area 300 shown on the left side. That is, the pixel rows corresponding to the moving picture display pixel rows 302 and 301-2 are indicated by dotted lines. On the other hand, the horizontal axis of the graph indicates the frequency, indicating a case where 60Hz is the video frequency. In addition, the optimal still image display frequency (Wall_Hz) means an optimal still image display frequency for analyzing data in the still image display area to have the minimum power consumption. The optimal still image display frequency (Wall_Hz) is determined according to the image pattern and the characteristics of the liquid crystal capacitor and the holding capacitor in the pixel. In some embodiments, it is possible to analyze the image pattern of the still image display pixel rows (corresponding to 301-1 and 301-3) and determine the optimal still image display frequency (Wall_Hz) from the lookup table (LUT) based on the result. have. The analysis of the image pattern will be described in more detail with reference to FIGS. 15 to 18 below.

In addition, in the present embodiment, a low frequency (U_Hz; hereinafter referred to as an upper still image display frequency) in the upper still image display area 301-1 of a moving picture display pixel row and a lower still image display area 301-3 in a moving picture display pixel row ) of the low frequency (L_Hz; hereinafter referred to as the lower still image display frequency), each low frequency is identified by analyzing the image pattern in each area. According to the embodiment, the image pattern of each still image display pixel row is analyzed and the still image display frequency (U_Hz) of the upper region and the still image display frequency (L_Hz) of the lower region are analyzed in the lookup table (LUT) based on the result. can figure out The analysis of the image pattern will be described in more detail with reference to FIGS. 15 to 18 below.

The optimal 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 pattern in the still image display area above and below the moving picture display pixel row ) may be arranged in various orders when shown in the graph of FIG. 8 . (Refer to FIGS. 12 and 13) However, in FIG. 8, if the frequencies are arranged in order of magnitude from small to large, the optimal still image display frequency (Wall_Hz), the still image display frequency of the upper region (U_Hz), and the still image of the lower region The case of the order of the display frequencies (L_Hz) is shown.

First, since the optimal still image display frequency (Wall_Hz) is an optimal frequency to represent the minimum power, if a frequency lower than this is used, a problem may occur in image quality. Therefore, a still image should not be displayed at a frequency lower than this. In FIG. 8, since both the still image display frequency (U_Hz) of the upper region and the still image display frequency (L_Hz) of the lower region are greater than the optimal still image display frequency (Wall_Hz), the still image display frequency (U_Hz) of the upper region and the lower region The image may be displayed according to the still image display frequency (L_Hz) of

At this time, as shown in the graph of FIG. 8 , the still image display frequency of the first pixel row and the last pixel row furthest from the moving picture display pixel row is set to the still image display frequency (U_Hz) of the upper region and the still image display frequency (U_Hz) of the lower region, respectively. L_Hz). Thereafter, the still image display frequency from the first and last pixel rows to the moving picture display pixel row is gradually increased and changed to be 60 Hz in the moving picture display pixel row. In the 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 displays a still image of the lower region. Driving at a frequency (L_Hz) may be ideal in terms of power consumption, but if the operating frequency is different for each pixel row in the still image display pixel row as shown in FIG. 8, moving image display that may occur around the moving image display pixel row and the still image display difference is not recognized.

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

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

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

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

However, in the embodiment of the present invention, even when a gate clock (CPV) signal is applied to all pixel rows, the actual gate clock ( As shown in FIG. 9 , the CPV′) signal is output only in the portion where the output enable (OE) signal has a low value and is not output in the remaining portions.

In FIG. 9 , in the output enable (OE) signal, the length of the period s having a low value varies for each frame. By changing the length of the low section s of the output enable (OE) signal, the still image display frequency is varied 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 increases from the left frame to the right frame. As a result, the number of pixel rows to which the data voltage is applied in the corresponding frame increases. That is, in the frame on the left, data voltage is applied only to the pixel row of the video display, but as the frame moves to the right, the data voltage is applied to the pixel row of the still image that exists above and below the pixel row of the video display so that it is refreshed. do. Further, the number of still image display pixel rows to which the data voltage is applied increases toward the right frame. In this way, since the moving picture display pixel row is displayed in every frame, the image is displayed at the moving picture frequency, and the still image display pixel row adjacent to the moving picture display pixel row is larger than the still image display pixel row far from the moving picture display pixel row. Since still images are displayed in many frames, it can be seen that the still image display frequency is larger.

In addition, if the length of the low section (s) of the output enable (OE) signal is adjusted to correspond to the frequency for each pixel row in the graph of FIG. 8, moving images and still images can be displayed at the display frequency according to the graph of FIG. make it possible

According to an embodiment, the still image display frequency may have a higher frequency by displaying a still image in more frames as it is closer to a moving picture display pixel row.

Also, according to an embodiment, in determining the still image display frequency, a predetermined pixel row may be divided into blocks and the still image frequency may be determined for each block.

Such an embodiment is shown in FIGS. 10 and 11 .

10 and 11 are diagrams showing graphs of frequencies for each pixel row for setting a frequency for displaying an image and displaying an image according to another 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, so a storage space (eg, LUT or memory) requires a large capacity.

Accordingly, in the embodiments of FIGS. 10 and 11 , an embodiment for reducing the storage space is illustrated.

First, FIG. 10 shows 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 corresponding 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.

The seven pixel row blocks of the upper region have different still image display frequencies, and all pixel rows within the same pixel row block display still images with 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 picture display pixel row, and have a value between the still image display frequency (U_Hz) of the upper region and the moving image display frequency (60 Hz).

The four pixel row blocks of the lower region have different still image display frequencies, and all pixel rows within the same pixel row block display still images with 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 picture display pixel row, and have a value between the still image display frequency (L_Hz) of the lower region and the moving image display frequency (60 Hz).

The pixel row blocks of the upper region and the lower region may each include the same number of pixel rows or may include different numbers 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 sets one of a still image display frequency (U_Hz), a moving image display frequency (60 Hz), and a plurality of predetermined still image display frequencies of the upper region as the maximum and minimum still image display frequencies, respectively. do. A still image display frequency is determined for each pixel row by interpolation for a pixel row belonging to a pixel row block in which the maximum value and the minimum value are determined. A still image display frequency displayed by each pixel row in one pixel row block may have a linearly increasing relationship.

Meanwhile, each pixel row block of the lower region sets one of a still image display frequency (L_Hz), a moving image display frequency (60 Hz), and a plurality of predetermined still image display frequencies of the lower region as the maximum and minimum still image display frequencies, respectively. do. A still image display frequency is determined for each pixel row by interpolation for a pixel row belonging to a pixel row block in which the maximum value and the minimum value are determined. A 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 is a preset value, the pixel row blocks are divided based on the pixel row displaying the predetermined still image display frequency, or the pixel row blocks are selected based on a specific predetermined pixel row. and then the still image display frequency of the corresponding pixel row may be used as it is.

Hereinafter, a graph of a display frequency for each pixel row according to another exemplary 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 optimal still image display frequency (Wall_Hz) is greater than the still image display frequency (U_Hz) of the upper region, when displaying a still image in the upper region, the still image is displayed at a frequency less than the optimal still image display frequency (Wall_Hz) I never do that. In FIG. 12 , a portion from the still image display frequency (U_Hz) of the upper region to the optimal still image display frequency (Wall_Hz) is shown with a dotted line, clearly indicating that the corresponding frequency is not used.

Meanwhile, in FIG. 12, in a state in which the frequency is set to increase in a curved form from the still image display frequency (U_Hz) of the upper region to the moving image frequency (60 Hz in this embodiment), all values less than the optimal still image display frequency (Wall_Hz) are This is an embodiment in which the optimum still image display frequency (Wall_Hz) is set.

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

Meanwhile, FIG. 13 illustrates a case in which the optimal still image display frequency (Wall_Hz) and the still image display frequency (U_Hz) of 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) of the upper region to the moving image frequency (60 Hz). (Refer to the curve ①) In addition, according to an embodiment, the same frequency may be maintained from the still image display frequency (U_Hz) of the upper region to a certain pixel row, and then the frequency may be set to increase in a curved form up to the moving image frequency. (Refer to curve ②)

In addition to FIGS. 8, 12, and 13, various graphs can be drawn by the calculated optimal 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 moving image frequency may vary, and the distance to the moving image display pixel row and the display panel It may change depending on characteristics, etc. In addition, information on the shape of an increasing curve or increasing values between pixel rows may be stored in the lookup table.

Hereinafter, the step of determining a frequency for a 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 shown in FIG. 14 shows the driving frequency determination unit 630 provided in the signal control unit 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 optimal still image display frequency extractor 631 to calculate the optimal still image display frequency (Wall_Hz). The optimal still image display frequency extraction unit 631 calculates a representative value through the image pattern of the still image display pixel rows 301-1 and 301-3, and selects the optimal value from the lookup table (LUT) based on the calculated representative value. Select the still image display frequency (Wall_Hz). 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 determining unit 630 is also input to the position determining unit 632 . The position determining unit 632 determines to which pixel of the display panel the continuously input image data is actually applied. Based on the determined result, data is divided for each pixel row, and the divided data of the pixel row is input to the still image/moving determiner 633 . The still image/moving determiner 633 compares the image data of the current frame (arbitrary nth frame) with the image data of the previous frame (n−1th frame) based on the pixel row to determine whether the image data is a still image, respectively. Determine if it is a video. The still image/video determiner 633 may compare with image data of a previous frame (n-1 th frame) including the frame memory 610 and the comparator 620 of FIG. 4 .

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, which part is the moving image display pixel row 302 in the display area 300, and which part is a still image display image Set whether or not

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

The calculated representative value and the weight are multiplied by each other, and then a driving frequency for each pixel row is selected from a lookup table (LUT) 637 using the multiplied result value, and in addition, the still image display frequency (L_Hz) of the lower region and the upper The still image display frequency (U_Hz) of the region is also selected. A lookup table (LUT) 637 stores a frequency value for a product of a representative value and a weight. According to an embodiment, the lookup table 637 may store a frequency value for a representative value.

As such, the optimal still image display frequency (Wall_Hz) selected from the lookup table 637, 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 determine the driving frequency. It is applied and corrected to the unit 638 to finally determine a driving frequency for each pixel row. 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 determined driving frequency is shown as a graph, it may be displayed as a graph as shown in FIGS. 8, 12, and 13 .

An 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 determined 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 for 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 an embodiment of the present invention.

First, FIG. 15 shows an example of calculating a representative grayscale value as a representative value.

15 is a graph showing the results of calculating the number of pixels (# of pxls) displaying each gray level in one pixel row or in a region for which a representative value is to be obtained. Among them, a value that can be selected as a representative value includes an average value (Avg), a peak value including the largest number of pixels (Peak), and a maximum grayscale value (Max) to be displayed. These are all gradation values.

Meanwhile, FIG. 16 shows that a luminance value (Lum.) instead of a grayscale value can be used as a representative value. As shown in FIG. 15 , when a representative grayscale (representative gray) value is determined, a luminance value according to the representative grayscale value is used as a representative value. The curve shown in FIG. 16 is a gamma curve.

Meanwhile, FIGS. 17 and 18 show examples of calculating a weight, respectively.

First, FIG. 17 shows an example in which a large weight is given when a representative gray value is an intermediate gray value, and a small weight is given when the representative gray value is close to the maximum or minimum value. Such a weight is an example for preventing a flicker from being recognized by a user. That is, when the luminance displayed by the pixel is low or high, the user can easily feel the luminance change according to the change in the luminance. It gives a lot of value to make a large value. In FIG. 17 , the weights are provided based on the representative grayscale values, but it is also possible to provide the weights based on the luminance values. In this case, when the luminance value has an intermediate luminance value, the weight is large, and when the luminance value is small or large, the weight is small.

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

Meanwhile, depending on the embodiment, both the weights of FIGS. 17 and 18 may be included and used, and in this case, a frequency may be selected based on a value obtained by multiplying a representative value by two weights, respectively.

As described above, various examples of representative values and weights have been reviewed in FIGS. 15 to 18 , and as the representative values and weights are changed, the reference value for selecting a frequency in the lookup table 637 is changed, and thus various representative values in the display device are changed. and weight may be selected and used.

According to an embodiment of the present invention, it is advantageous to reduce power consumption by operating the still image display pixel row at a frequency as low as possible. However, in such low-frequency driving, display quality may be deteriorated due to current leakage in the OFF state occurring in the thin film transistor included in the pixel. Therefore, it is necessary to display an image at a low frequency to the extent that there is no display quality according to the characteristics of the pixel, and this concept is included in the optimal still image display frequency (Wall_Hz). In addition, since the low-frequency driving is possible by reducing the current leakage in the off state in the thin film transistor, the thin film transistor formed in the pixel of the display device may use an oxide semiconductor as a channel layer. That is, since a thin film transistor using an oxide semiconductor as a channel layer has less leakage current in an OFF state, lower frequency driving may be possible compared to a case where amorphous silicon is used for the thin film transistor. However, even when a thin film transistor including amorphous silicon is used, low power consumption can be driven by appropriately adjusting a low frequency.

Meanwhile, according to an embodiment, the thin film transistor may use polysilicon as a channel layer.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

300: display area 301-1, 301-2, 301-3: still image display area
302: video display area 400: gate driver
410: gate driving IC 500: data driving unit
510: data driving IC 600: signal controller
610: frame memory 620: comparator
625: line buffer memory 630: driving frequency determining unit
631: display frequency extraction unit 632: position determination unit
633: still image / video judgment unit
634: video display pixel row setting unit
635: representative value calculation unit 636: weight calculation unit
637: lookup table 638: drive frequency determining unit

Claims (20)

a display panel;
The display panel is
A first still image display area, a moving image display area, and a second still image display area sequentially positioned from the top;
gate line and data line;
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/video determining unit that divides the image data input from the outside into a moving picture display pixel row or a still image display pixel row, and
a driving frequency determining unit for determining driving frequencies of the moving image display pixel row and the still image display pixel row;
Each of the first still image display area and the second still image display area includes a plurality of adjacent rows of the still image display pixels;
The video display area includes a plurality of adjacent video display pixel rows,
The lowest first lowest frequency among still image display frequencies for driving the first still image display region is different from the lowest second lowest frequency among still image display frequencies for driving the second still image display region,
A display device in which a pixel row adjacent to the moving image display region among the plurality of still image display pixel rows included in the first still image display region is driven at a higher still image display frequency than a pixel row farther away.
delete In claim 1,
The still image display frequency in the first still image display area gradually increases as it approaches the moving image display area.
In claim 3,
A display device in which a pixel row adjacent to the moving image display region among the plurality of still image display pixel rows included in the second still image display region is driven at a higher still image display frequency than a pixel row farther away.
In claim 4,
The still image display frequency in the second still image display area gradually increases as it approaches the moving image display area.
In claim 1,
The first still image display area is divided into a plurality of first blocks,
the still image display pixel rows belonging to different blocks among the plurality of first blocks are driven at different still image display frequencies;
The still image display pixel rows belonging to the same block among the plurality of first blocks are driven at the same still image display frequency.
display device.
In claim 6,
A display device driven with a higher still image display frequency as a block is closer to the moving picture display area among the plurality of first blocks.
In claim 7,
The second still image display area is divided into a plurality of second blocks,
the still image display pixel rows belonging to different blocks among the plurality of second blocks are driven at different still image display frequencies;
The still image display pixel rows belonging to the same block among the plurality of second blocks are driven at the same still image display frequency.
display device.
In claim 8,
A display device driven at a higher still image display frequency as a block is closer to the moving image display area among the plurality of second blocks.
In claim 1,
The video display pixel row is driven at a video frequency higher than the first lowest frequency and the second lowest frequency.
In a display device including a display panel,
Comparing the image data of the current frame (arbitrary nth frame) input from the outside with the image data of the previous frame (n-1st frame) and dividing the video display pixel row into a moving image display pixel row and a still image display pixel row, and
driving the moving image display pixel row and the still image display pixel row
including,
The display panel includes a first still image display area, a moving image display area, and a second still image display area sequentially positioned from above;
Each of the first still image display area and the second still image display area includes a plurality of adjacent rows of the still image display pixels;
The video display area includes a plurality of adjacent video display pixel rows,
The lowest first lowest frequency among still image display frequencies for driving the first still image display region is different from the lowest second lowest frequency among still image display frequencies for driving the second still image display region,
of the plurality of still image display pixel rows included in the first still image display region, a pixel row adjacent to the moving image display region is driven at a higher still image display frequency than a pixel row farther away.
delete In claim 11,
The still image display frequency in the first still image display region gradually increases as it approaches the moving image display region.
In claim 13,
of the plurality of still image display pixel rows included in the second still image display region, a pixel row adjacent to the moving picture display region is driven at a higher still image display frequency than a pixel row farther away.
15. In claim 14,
The still image display frequency in the second still image display area gradually increases as it approaches the moving image display area.
In claim 11,
The first still image display area is divided into a plurality of first blocks,
the still image display pixel rows belonging to different blocks among the plurality of first blocks are driven at different still image display frequencies;
The still image display pixel rows belonging to the same block among the plurality of first blocks are driven at the same still image display frequency.
A method of driving a display device.
17. In claim 16,
A method of driving a display device in which a block closer to the video display area among the plurality of first blocks is driven at a higher still image display frequency.
In claim 17,
The second still image display area is divided into a plurality of second blocks,
the still image display pixel rows belonging to different blocks among the plurality of second blocks are driven at different still image display frequencies;
The still image display pixel rows belonging to the same block among the plurality of second blocks are driven at the same still image display frequency.
A method of driving a display device.
In claim 18,
A method of driving a display device in which a block closer to the video display area among the plurality of second blocks is driven at a higher still image display frequency.
In claim 11,
The moving picture display pixel row is driven at a moving picture frequency higher than the first lowest frequency and the second lowest frequency.

Images