KR20020044673A - Liquid Crystal Display device with a function of compensating a moving picture and driving apparatus and method thereof - Google Patents

Abstract

PURPOSE: An LCD having a motion picture correction function and an apparatus and a method for driving the same are provided to remove a stroboscopic motion by using a picture signal correction circuit. CONSTITUTION: A dynamic capacitance compensation circuit(400) is formed with a frame memory(420), a controller(430), and a data gradation signal converter(440). The dynamic capacitance compensation circuit(400) receives R, G, and B gradation signals of n bits from a data gradation signal source and outputs corrected gradation signals. The frame memory(420) is used for determining bits of gradation signals. The frame memory(420) receives gradation signals of m bits of a current frame and outputs gradation signals of m bits of a previous frame. The data gradation signal converter(440) receives(n-m) bits of the current frame, m bits of the current frame, and m bits of the previous frame and outputs a corrected gradation signal.

Description

Liquid crystal display device with a function of compensating a moving picture and driving apparatus and method

The present invention relates to a liquid crystal display device and a driving device and method thereof, and more particularly, to a liquid crystal display device and a driving device and method thereof for eliminating the screen drag phenomenon when a moving image is implemented.

In general, an LCD is a display device that obtains a desired image signal by applying an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and adjusting the intensity of the electric field to control the amount of light transmitted through the substrate. to be. Such LCDs are typical of portable flat panel displays, and among them, TFT LCDs using thin film transistors (TFTs) as switching devices are mainly used.

Recently, as TFT LCDs are widely used as display devices of televisions as well as display devices of computers, there is an increasing need to implement moving images. However, the conventional TFT LCD has a disadvantage in that it is difficult to implement moving images because of the slow response speed.

In order to improve the response speed problem, conventionally, an OCB (Optically Compensated Band) mode is used or a TFT LCD using a ferro-electric liquid crystal (FLC) material is used.

However, in order to use such an OCB mode or FLC, a conventional TFT LCD panel has a problem in that the structure must be changed.

Accordingly, an object of the present invention is to provide a liquid crystal display device having a moving picture correction function which eliminates the screen phenomena when a moving picture is implemented through image signal correction.

Another object of the present invention is to provide a driving device of the liquid crystal display device having the above-described moving image correction function.

Another object of the present invention is to provide a method of driving a liquid crystal display device having the above-described moving image correction function.

1 is a diagram illustrating an equivalent circuit of each pixel in a liquid crystal display.

2 is a diagram illustrating a data voltage and a pixel voltage applied by a conventional driving method.

3 is a diagram illustrating a transmittance of a liquid crystal display according to a conventional driving method.

4 is a diagram illustrating a model between a voltage and a dielectric constant of a liquid crystal display.

5 is a diagram illustrating a data voltage application method according to an embodiment of the present invention.

6 illustrates a transmittance of a liquid crystal display when a data voltage is applied according to an exemplary embodiment of the present invention.

7 is a diagram illustrating a transmittance of a liquid crystal display when a data voltage is applied according to another embodiment of the present invention.

8 illustrates a liquid crystal display according to an exemplary embodiment of the present invention.

9 is a view for explaining a first embodiment of the data gray level signal correcting unit according to the present invention.

10 is a diagram for explaining a general phenomenon of the LCD screen dragging.

FIG. 11 is a diagram illustrating a screen drag phenomenon through a moving rectangle.

12 is a diagram illustrating a transmittance of a liquid crystal display when a data voltage using a subframe is applied according to an exemplary embodiment of the present invention.

13A to 13B are diagrams for describing a second exemplary embodiment of the data gray signal correcting unit according to the present invention.

14A to 14C are diagrams for describing a third exemplary embodiment of the data gray level signal correcting unit according to the present invention.

A liquid crystal display device having a video correction function according to one feature for realizing the above object of the present invention,

The gradation data frame of the image signal provided from the data gradation signal source is divided into at least two subframes, and corrected by overshoot or undershoot driving according to the comparison of the gradation signal of the previous frame with the gradation signal of the current frame. A data gradation signal correction unit for outputting gradation data;

A data driver unit receiving the corrected grayscale data through the overshoot or undershoot driving to change the data voltage to a data voltage corresponding to the corrected grayscale data to output an image signal;

A gate driver unit sequentially supplying scan signals; And

A plurality of gate lines transferring the scan signal, a plurality of data lines transferring the image signal and insulated from and intersecting the gate lines, and formed in an area surrounded by the gate lines and the data lines, respectively; And a liquid crystal display panel including a plurality of pixels arranged in a matrix having switching elements connected to the data lines.

In addition, a driving device of a liquid crystal display device having a moving picture correction function according to one feature for realizing another object of the present invention is a liquid crystal for receiving the grayscale data of an image signal from a data grayscale signal source and outputting the grayscale data to a liquid crystal display module. In the driving device of the display device,

The gradation data frame of the image signal provided from the data gradation signal source is divided into at least two subframes, and corrected by overshoot or undershoot driving according to the comparison of the gradation signal of the previous frame with the gradation signal of the current frame. And a data gray signal corrector for outputting gray data to the liquid crystal display module to speed up the response speed of the liquid crystal.

In addition, a method of driving a liquid crystal display device having a moving image correction function according to another aspect of the present invention includes a plurality of gate lines and a plurality of data lines insulated from and intersecting the gate lines. And a plurality of pixels formed in a region surrounded by the gate line and the data line and connected to the gate line and the data line, respectively, and arranged in a matrix type having a switching element.

(a) sequentially supplying a scan signal to the gate line;

(b) dividing one picture frame provided from an external data gradation signal source into at least two subframes;

(c) comparing the gray level signal of the current frame with the gray level signal of the previous frame as a gray level signal of the current frame is input;

(d) If it is checked in step (c) that the gray level signal of the current frame is larger than the gray level signal of the previous frame, the overshoot driving is performed when the subframe located in the first half of the divided subframes is driven. Generating a data driving voltage and generating a second data driving voltage by driving down the overshooted value to a target value when driving the subframe positioned in the second half of the divided subframes;

(e) If it is checked in step (c) that the gray level signal of the previous frame is smaller than the gray level signal of the current frame, undershoot driving is performed when the subframe located in the first half of the divided subframes is driven. Generating a data driving voltage and generating a fourth data driving voltage by performing an up-driving of the undershooted value to a target value when driving the subframe positioned in the second half of the divided subframes;

(f) supplying the first to fourth data driving voltages generated in the step (c) and the step (d) to the data line, thereby increasing the response speed of the liquid crystal.

According to such a liquid crystal display device having a moving picture correction function, a driving device and a method thereof, a gray level signal of a current frame that is larger than a gray level signal of a previous frame by using two sub-frames time-divided into one frame in the moving picture representation of the liquid crystal display device. When is input, the overshoot driving is performed when the first subframe is driven and then down-driven to the target value when the second subframe is driven, thereby eliminating the screen drag when the LCD is implemented. .

Also, when the gray level signal of the current frame smaller than the gray level signal of the previous frame is input using two time-divided subframes, the undershoot driving is performed when the first subframe is driven, and then when the second subframe is driven. By driving up to the target level, the screen drag can be eliminated when the LCD is implemented.

Then, embodiments will be described so that those skilled in the art can easily implement the present invention.

In general, LCDs include a plurality of gate lines that transfer scan signals and data lines that cross and form a data voltage. In addition, the LCD is formed in an area surrounded by these gate lines and data lines, and includes a plurality of pixels in a matrix form connected to the gate lines and data lines and the switching elements, respectively.

In the LCD, each pixel may be modeled as a capacitor having a liquid crystal as a dielectric, that is, a liquid crystal capacitor. The equivalent circuit of each pixel in the LCD is illustrated in FIG. 1.

As shown in FIG. 1, each pixel of the liquid crystal display includes a TFT 10 having a source electrode and a gate electrode connected to a data line Dm and a gate line Sn, and a drain electrode and a common voltage Vcom of the TFT, respectively. ) And a storage capacitor (Cst) connected to the liquid crystal capacitor (Cl) connected to the drain electrode of the TFT.

In FIG. 1, when the gate on signal is applied to the gate line Sn and the TFT 10 is turned on, the data voltage Vd supplied to the data line is applied to each pixel electrode (not shown) through the TFT. . Then, an electric field corresponding to the difference between the pixel voltage Vp and the common voltage Vcom applied to the pixel electrode is applied to the liquid crystal (equivalently represented by the liquid crystal capacitor in FIG. 1), and thus transmittance corresponding to the intensity of the electric field. To allow light to pass through. At this time, the pixel voltage Vp should be maintained for one frame. In FIG. 1, the storage capacitor Cst is used to maintain the pixel voltage Vp applied to the pixel electrode.

On the other hand, since the liquid crystal has an anisotropic dielectric constant, there is a characteristic that the dielectric constant is different depending on the direction of the liquid crystal. That is, when the director of the liquid crystal changes as the voltage is applied, the dielectric constant also changes accordingly, and thus the capacitance value (hereinafter, referred to as liquid crystal capacitance) of the liquid crystal capacitor also changes. Once electric charge is supplied to the liquid crystal capacitor during the period in which the TFT is turned on, the TFT is turned off. Since Q = CV, when the liquid crystal capacitance changes, the pixel voltage Vp applied to the liquid crystal also changes.

Normally white mode TN (twisted Nematics) LCD, for example, when the pixel voltage supplied to the pixel is 0V, the liquid crystal capacitance is arranged in a direction parallel to the substrate, the liquid crystal capacitance is C (0V) = A / d. here, Denotes the permittivity when the liquid crystal molecules are arranged in a direction parallel to the substrate, that is, when the liquid crystal molecules are arranged in a direction perpendicular to the direction of the light, and A and d represent the area of the LCD substrate and the distance between the substrates, respectively. . If the voltage for realizing full black is 5V, when 5V is applied to the liquid crystal, the liquid crystal molecules are arranged in the direction perpendicular to the substrate, so that the liquid crystal capacitance is C (5V) = A / d. In the case of liquid crystal used in TN mode - > 0, the higher the pixel voltage applied to the liquid crystal, the larger the liquid crystal capacitance.

The amount of charge the TFT must charge to make full black in the nth frame is C (5V) × 5V. However, assuming full white (Vn-1 = 0V) in the n-1th frame, which is the previous frame, the liquid crystal capacitance becomes C (0V) since the liquid crystal does not respond during the turn-on time of the TFT. Therefore, even if the data voltage Vd of 5V is applied in the nth frame to make full black, the amount of charge charged in the actual pixel is C (0V) × 5V, and C (0V) <C (5V). The pixel voltage Vp supplied is applied with a pixel voltage less than 5V (for example, 3.5V), so that full black is not implemented. In addition, when the data voltage Vd is applied at 5V to implement full black in the next frame, the n + 1th frame, the amount of charge charged in the liquid crystal becomes C (3.5V) × 5V, which is eventually supplied to the liquid crystal. The voltage Vp is between 3.5V and 5V. If this process is repeated, the pixel voltage Vp reaches a desired voltage after several frames.

In other words, when the signal (pixel voltage) applied to an arbitrary pixel is changed from a low gray level to a high gray level (or from a high gray level to a low gray level), the gray level of the current frame is influenced by the gray level of the previous frame. Because it does not receive the desired gradation, it does not reach the desired gradation until a few frames have elapsed. Similarly, the transmittance of the pixel of the current frame is influenced by the transmittance of the pixel of the previous frame to obtain the desired transmittance after a few frames have elapsed.

On the other hand, if n-1 frame is full black, that is, the pixel voltage (Vp) is 5V, and a data voltage of 5V is applied to implement full black in n frame, the liquid crystal capacitance is C (5V), so C The amount of charges corresponding to (5V) x 5V is charged, so that the pixel voltage Vp of the liquid crystal is 5V.

As such, the pixel voltage Vp actually supplied to the liquid crystal is determined not only by the data voltage supplied to the current frame but also by the pixel voltage Vp of the previous frame.

2 is a diagram illustrating a data voltage and a pixel voltage when applied in a conventional driving method.

As shown in FIG. 2, the data voltage Vd corresponding to the target pixel voltage Vw is applied every frame without considering the pixel voltage Vp of the previous frame. Therefore, as described above, the pixel voltage Vp actually applied to the liquid crystal is lower or higher than the target pixel voltage by the liquid crystal capacitance corresponding to the pixel voltage of the previous frame. Therefore, the target pixel voltage is only reached after a few frames.

3 is a view showing transmittance of the liquid crystal display according to the conventional driving method.

As shown in FIG. 3, since the actual pixel voltage is lower than the target pixel voltage as described above, the target transmittance is not reached until a few frames have passed even when the response time of the liquid crystal is within 1 frame.

The embodiment of the present invention compares the image signal Sn of the current frame with the image signal Sn-1 of the previous frame to generate the following correction signal Sn 'and then corrects the image signal Sn'. Is applied to each pixel. Here, the image signal Sn refers to a data voltage in the analog driving method, but in the case of the digital driving method, since the binary gray level signal is used to control the data voltage, the correction of the voltage applied to the actual pixel is performed. Through the correction of

First, if the image signal (gradation signal or data voltage) of the current frame is the same as the image signal of the previous frame, no correction is performed.

Second, when the image signal (gradation signal or data voltage) of the current frame is higher than the gradation signal (data voltage) of the previous frame, a corrected gradation signal (data voltage) is output than the current gradation signal (data voltage). When the gray level signal (data voltage) of the current frame is lower than the gray level signal (data voltage) of the previous frame, the corrected gray level signal (data voltage) lower than the current gray level signal (data voltage) is output. In this case, the degree of correction is proportional to the difference between the current gray level signal (data voltage) and the gray level signal (data voltage) of the previous frame.

Third, only some bits of the gray level signal applied from the data gray level signal source are corrected to obtain a corrected gray level signal. At this time, the remaining bits that are not corrected are bypassed. That is, when an n-bit gray level signal is received from the data gray level signal source, a corrected gray level signal is obtained using only some bits m of the n-bit gray level signal. In this case, m bits are the remainder except n (i = 1, 2, ..., n-1) bits from LSB (Least Significant Bit) among the n-bit gray level signals. That is, m bits are (n-i) bits.

Hereinafter, a data voltage correction method according to an embodiment of the present invention will be described schematically.

FIG. 4 is a diagram for briefly modeling a relationship between a voltage and a dielectric constant of a liquid crystal display.

In FIG. 4, the horizontal axis represents pixel voltages, and the vertical axis represents dielectric constant at a specific pixel voltage v. ) And when the liquid crystals are arranged in a direction parallel to the substrate, that is, when the liquid crystal is perpendicular to the transmission direction of light ( ) Ratio.

In Figure 4, Of That is, the maximum of Of Is assumed to be 3, and Vth and Vmax are assumed to be 1V and 4V, respectively. Here, Vth and Vmax represent pixel voltages corresponding to full white and full black (or vice versa), respectively.

If the capacitance of the storage capacitor (hereinafter referred to as 'storage capacitance') is equal to the average value of the liquid crystal capacitance <Cst>, and the width of the LCD substrate and the distance between the substrates are A and d, respectively, the storage capacitance Cst is It can be represented by Equation 1 below.

+ 2 ) A / d = 5/3 A / d = 5/3 C0

Where C0 = A / d.

From FIG. 4, Of May be represented by Equation 2 below.

Of = 1/3 (2V + 1)

Since the total capacitance C (V) of the LCD is the sum of the liquid crystal capacitance and the storage capacitance, the capacitance of the LCD may be represented by the following equation (3) from equations (1) and (2).

A / d + 5/3 C0 = 1/3 (2V + 1) C0 + 5/3 C0

= 2/3 (V + 3) C0

Since the charge amount Q applied to the pixel is preserved, the following equation (4) holds.

Q = C (Vn) Vn = C (Vf) Vf

Here, Vn represents a data voltage to be applied to the current frame (absolute value of the data voltage in the case of the inversion driving type), and C (Vn-1) represents a capacitance corresponding to the pixel voltage of the previous frame (n-1 frame). C (Vf) represents a capacitance corresponding to the actual pixel voltage Vf of the current frame (n frame).

The following equation (5) can be derived from equations (3) and (4).

C (Vn-1) Vn = C (Vf) Vf = 2/3 (Vn-1 + 3) Vn = 2/3 (Vf + 3) Vf

Therefore, the actual pixel voltage Vf can be represented by the following equation (6).

As can be clearly seen from Equation 6 above, the actual pixel voltage Vf is determined by the data voltage Vn applied to the current frame and the pixel voltage Vn-1 applied to the previous frame.

On the other hand, if the data voltage applied to make the pixel voltage reach the target voltage Vn in n frames is Vn ', Vn' may be represented by the following equation (7).

(Vn-1 + 3) Vn '= (Vn + 3) Vn

Therefore, Vn 'may be represented by the following equation (8).

As such, when the data voltage Vn 'obtained by Equation 8 is applied in consideration of the target pixel voltage Vn of the current frame and the pixel voltage Vn-1 of the previous frame, the target pixel voltage Vn is applied. You can reach it right away.

Equation 8 is derived from the diagram shown in FIG. 4 and some basic assumptions, and the data voltage Vn 'applied to a general LCD may be represented by Equation 9 below.

Here, the function f is determined by the characteristics of the LCD. The function f basically has the following properties.

In other words, and In this case, f = 0, this Is greater than 0 if greater than this If less than f is less than zero.

The following describes a data voltage application method according to an embodiment of the present invention.

5 is a view showing a data voltage application method according to the present invention.

As shown in FIG. 5, in the first embodiment of the present invention, the data voltage Vn 'corrected in consideration of the target pixel voltage of the current frame and the pixel voltage (data voltage) of the previous frame is applied to the pixel voltage Vp. This is to reach the target voltage.

That is, in the first embodiment of the present invention, when the target voltage of the current frame and the pixel voltage of the previous frame are different, a first voltage (or lower voltage) higher than the target voltage of the current frame is applied as the corrected data voltage. After the target voltage level is reached directly in the frame, the target voltage is applied as the data voltage in subsequent frames. In this way, the response speed of the liquid crystal can be improved.

In this case, the corrected data voltage (charge amount) is determined in consideration of the liquid crystal capacitance determined by the pixel voltage of the previous frame. That is, according to the present invention, the charge amount Q is supplied in consideration of the pixel voltage level of the previous frame to reach the target voltage level immediately in the first frame.

6 is a diagram illustrating a transmittance of a liquid crystal display when a data voltage is applied according to the first embodiment of the present invention. As shown in Fig. 6, since the corrected data voltage is applied according to the first embodiment of the present invention, the target transmittance is directly reached in the current frame.

On the other hand, in the second embodiment of the present invention, the corrected voltage Vn 'slightly higher than the target voltage is applied as the pixel voltage. In this case, as shown in FIG. 7, the transmittance becomes smaller than the target value before about 1/2 of the response time of the liquid crystal, but after that, the transmittance becomes overcompensated and the average transmittance becomes equal to the target transmittance. .

Next, a liquid crystal display according to an exemplary embodiment of the present invention will be described.

8 is a diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention, and the liquid crystal display according to the exemplary embodiment of the present invention uses a digital driving method.

As shown in FIG. 8, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal display panel 100, a gate driver 200, a data driver 300, and a data gray level signal corrector 400. Include.

In the liquid crystal display panel 100, a plurality of gate lines S1, S2, S3,..., Sn for transmitting a gate-on signal are formed, and data lines D1, for transmitting a corrected data voltage. D2, ..., Dm) are formed. Each region surrounded by the gate line and the data line constitutes a pixel, and each pixel is connected to the thin film transistor 110 and the drain electrode of the thin film transistor 110 having a gate electrode and a source electrode connected to the gate line and the data line, respectively. The pixel capacitor Cl and the storage capacitor Cst are included.

The gate driver 200 sequentially applies a gate-on voltage to the gate line, thereby turning on the TFT to which the gate electrode is connected to the gate line to which the gate-on voltage is applied.

The data gray level signal corrector 400 receives n-bit data gray level signal Gn from a data gray level signal source (for example, a graphic controller), and then, as described above, the data gray level signal of the current frame of m bits The m-bit data gradation signal Gn 'is corrected in consideration of the data gradation signal of the previous frame of m-bits.

In this case, the gradation signal correction unit may exist as a stand-alone unit, or may be integrated into a graphic card or an LCD module.

The data driver 300 converts the corrected gradation signal Gn 'received from the data gradation signal correction unit 400 into a corresponding gradation voltage (data voltage) and applies them to the data lines, respectively.

9 is a view for explaining a first embodiment of the data gray level signal correcting unit according to the present invention.

As shown in FIG. 9, the first embodiment of the data correction signal correcting unit 400, that is, the image signal correction circuit (DCC) according to the present invention, includes a frame memory 410 and a controller ( 420, and a data gradation signal converter 430, and are corrected by receiving n-bit gradation signals Gn for R (red), G (green), and B (blue), respectively, from the data gradation signal source. The gray level signal Gn 'is output. Therefore, the gray level signal received by the data gray level signal corrector 430 is a total of (3 × n) bits. Here, one of ordinary skill in the art may allow a (3 × n) bit gray level signal to be simultaneously applied to the data gray level signal correcting unit 430 from the data gray level signal source, and sequentially apply n-bit R, G, and B gray level signals, respectively. You can do that.

In Fig. 9, the frame memory 410 determines the bits of the gradation signal to be corrected, m of n bits of gradation signals for R (red), G (green), and B (blue) received from the data gradation signal source. Only the bits are input, and the bits are stored at predetermined addresses corresponding to R, G, and B, and output to the data gray level signal converter 430 after one frame delay. That is, the frame memory 410 receives the m-bit gradation signal Gn of the current frame and outputs the m-bit gradation signal Gn-1 of the previous frame.

The data gradation signal converter 430 includes (nm) bits of the current frame Gn bypassed without correction among the n bits received from the data gradation signal source, and m of the current frame Gn received for correction. After receiving the bits and the m bits of the previous frame Gn-1 delayed by the frame memory 410, a corrected gradation signal Gn 'is generated considering the m bits of the current and previous frames.

Through the image signal correction circuit, the response time of the liquid crystal can be lowered within one frame, thereby completely eliminating the degradation of the active contrast ratio and the stroboscopic motion of the LCD panel.

However, although the retinal afterimage time is shortened in the LCD panel, the attraction phenomenon is still observed, and thus the attraction phenomenon or blurring of the edges cannot be completely eliminated.

Although the response time is much shorter than the retinal afterimage time, for example 40 ms, the reason why the attraction is still observed is explained as follows.

A moving picture implementation will be described taking an example of a rectangle moving across an LCD screen.

10 is a diagram for explaining a general phenomenon of the LCD screen dragging.

As shown in Fig. 10, when the black color of the rectangle moves from left to right on the LCD screen, the black color is maintained in the (n-1) th frame, but the A area of the black color rectangle in the nth frame is the background ( background) The color is changed from the foreground color to the foreground color, the B area of the black color rectangle remains in the foreground, and the C area of the black color rectangle is changed from the foreground to the background.

Therefore, while the B area continues to show black during the nth frame, the A and B areas show gray because white and black are mixed.

In the next frame, the (n + 1) th frame, the B 'area of the rectangle remains the same as the nth frame described above, and the rectangles A' and B 'are mixed with white and black. It will be grayed out.

If the observer sees a fixed spot on the LCD screen, these conversion areas (A, C) (A ', C') are not a big problem, but if there is a moving object on the screen, the observer's eye will follow the moving object. do. That is, the areas B, B ', B ", ... continue to be imaged at one fixed location on the retina, and similarly the areas A, A', A", ... are fixed at one location and become an image, The same applies to the C, C ', C ", ... regions.

When the LCD panel reacts in one frame as shown in Fig. 11A, the light projected on the retina for recognizing the respective portions A, B, and C of the rectangle is as shown in (b).

The observer's eye does not detect the change at a speed of about 16ms and recognizes the average value.

In FIG. 11B, the solid line portion is the response that is actually felt. Ideally, the area A should be full black and the area C should be full white, so a clear rectangle without blurring will be recognized on the screen. However, as shown in FIG. In the region, the maximum luminance is not reached. In order to reduce this error, the response speed of the liquid crystal should be faster.

For example, if a tolerance of about 5% is tolerated, the response time of the liquid crystal should be about one tenth of one frame. That is, when 60 frames / sec, the liquid crystal responds within 1.67 ms and within 30 frames / sec to 3.33 ms in order to recognize a clear screen without blurring on the screen.

However, Nematics liquid crystals that respond within such a fast time between all gray levels are currently undeveloped.

Next, an example for implementing an LCD screen without dragging through correction of an image signal will be described. To this end, as shown in FIG. 12, one image frame is driven by dividing into two subframes.

12 is a diagram illustrating a transmittance of a liquid crystal display when a data voltage using a subframe is applied according to an exemplary embodiment of the present invention.

As shown in FIG. 12, when the gray level signal of the current frame larger than the gray level signal of the previous frame is input, overshoot driving is performed in the first subframe n ⁺ of the divided image frames, and the second subframe is performed. (n ^-), it does the drive will pull said overshoot value to the original value of the desired target.

The overshoot of this method makes up for the amount of light lost during the response time of the liquid crystal, and the response speed of the liquid crystal is infinitely fast, so that the edge of the moving image is clearly recognized. The overshooting value is a function that depends on the gradation level of the current frame and the gradation level of the past frame.

In FIG. 12, when the gray level signal of the current frame is checked to be larger by comparing the gray level signal of the previous frame with the gray level signal of the current frame, overshoot driving is performed in the first subframe, and in the second subframe. Although driving down to a target value has been described as an example, the reverse is also possible.

That is, when the gray level signal of the current frame smaller than the gray level signal of the previous frame is input, the undershoot driving is performed in the first subframe, and the driving value is up driven to the target value in the second subframe. This can eliminate the screen drag that occurs during implementation.

13A to 13B are diagrams for describing a second exemplary embodiment of the data gray signal correcting unit according to the present invention. FIG. 13A is a diagram for explaining the data gray signal correcting unit according to the first subframe. FIG. 4 is a diagram for describing a data gray level signal correcting unit according to a second subframe. FIG.

As shown in FIGS. 13A to 13B, the second embodiment of the data correction signal correction unit 400, that is, the image signal correction circuit (DCC) according to the present invention, includes a synthesizer 410 and a frame memory unit. 420, a controller 430, a data gray level signal converter 442, and a separator 450, and a description overlapping with FIG. 11 will be omitted.

The frame memory unit 420 includes a first frame memory 422 and a second frame memory 424, and the gray level provided from the synthesizer 410 according to a control signal (write / read) provided from the controller 430. Storing the signal and outputting the gradation signal of the previous frame to the data gradation signal converter 442 or outputting the gradation signal of the current frame and the gradation signal of the previous frame already stored to the data gradation signal converter 442 Do this.

More specifically, the first memory 422 stores the gray level signal G _n of the current frame provided from the synthesizer 410 as a write signal write is input from the controller 430 when the first sub frame is driven. As the read signal read is input from the controller 430 when the second sub frame is driven, the gray level signal G _n of the current frame stored in advance is output to the data gray level signal converter 442.

As the read signal read is input from the controller 430 when the first subframe is driven, the second memory 424 outputs the pre-stored gray level signal G _n-1 to the data gray level signal converter 442. When a read signal read is input from the controller 430 when the second sub frame is driven, the gray level signal G _n-1 of the previous frame stored in advance is output to the data gray level signal converter 442.

The data gray level signal converter 442 is provided with the gray level signal G _n of the current frame provided from the synthesizer 410 and the current provided from the frame memory unit 420 according to the frame detection signal 431 provided from the controller 430. the service received tone signals (G _n-1) of the gray level signal of the frame (G _n) or the previous frame, the first correction gradation signal ( ) Or the second corrected gradation signal ( ) Is output to the separator 450.

In more detail, when the frame detection signal 431 provided from the controller 430 is checked as the first subframe, the gray level signal G _n of the current frame provided from the synthesizer 410 is received, and the frame memory unit is provided. The corrected gray level signal of the first subframe is received by receiving the gray level signal G _n-1 of the previous frame provided from the second frame memory 424 of 420. ) Is output to the separator 450.

In addition, when the frame detection signal 431 provided from the controller 430 is checked as the second sub frame, the gray level signal G _n of the current frame provided from the first frame memory 422 is received and the second frame is received. The corrected gray level signal of the second sub-frame is received by receiving the gray level signal G _n-1 of the previous frame provided from the memory 424. ) Is output to the separator 450.

As described above, in the second embodiment of the data gradation signal correcting unit according to the present invention, the gradation signal G _n of the current frame and the gradation signal G _n-1 of the previous frame output from the frame memory unit 420. ), In the first subframe n ⁺ , as shown in FIG. 13A, the first corrected gray level signal ( ), The output, and the second subframe (n ^- a) in the second, as shown in Figure 13b corrected gray level signal ( ) In this case, the first corrected gray level signal is an overshoot corrected gray level signal when the gray level signal of the current frame is larger than the gray level signal of the previous frame, and undershoot corrected when the gray level signal of the current frame is smaller than the gray level signal of the previous frame. It is a gradation signal.

In addition, when the gray level signal of the current frame is larger than the gray level signal of the previous frame, the second corrected gray level signal is a corrected gray level signal which downgraded the overshooted value to the original desired target value, and the gray level signal of the current frame is the previous frame. If it is smaller than the gray scale signal, the corrected gray scale signal is raised to the original desired target value.

As described in the second embodiment of the present invention, in the case of DVD or TV and other video signals using the interlaced scanning method in which the same picture is repeatedly output during two fields, the driving is 60field / sec but the content is 30frame / sec.

Therefore, in the present invention, a signal for notifying whether a frame has been changed or not, the controller provides a frame signal to the data gray level signal converter, and the data gray level signal converter is configured to drive the first subframe according to the frame signal provided from the controller. The corrected gray scale data or the corrected gray scale data according to the second sub-frame driving.

On the other hand, the operation of writing to the frame memory is performed only in the positive (+) frame, that is, the first subframe. That is, when the screen is changed, the data is recorded in the frame memory, the first grayscale data is output from the data gray signal converter, and the grayscale data of the second subframe is not recorded in the frame memory in the next subframe. Will print out and repeat this process.

In the second embodiment of the present invention, a video frame is time-divided into two sub-frames, and a moving picture correction operation is performed by comparing the gray level signals of the previous frame and the current frame when the time-divided first sub-frame and the second sub-frame are driven. Although the description has been made, the present invention will not be departed from the separation of three or more subframes. For example, when divided into three subframes, the first subframe may be used as one subframe, and the second and third subframes may be used as another subframe.

14A to 14C are diagrams for describing a third exemplary embodiment of the data gray level signal correcting unit according to the present invention.

As shown in FIGS. 14A to 14C, the third embodiment of the data correction signal correction unit 400, that is, the image signal correction circuit (DCC) according to the present invention, includes a synthesizer 410 and a frame memory unit. 420, a controller 430, a data gray level signal converter 444, and a separator 450, and a description overlapping with FIG. 11 will be omitted.

The frame memory unit 420 includes a first frame memory (A) 426, a second frame memory (B) 427, and a third frame memory (C) 428 to control the controller 430. Receives the gray level signal of the current frame from the synthesizer 410, and writes it to any one of the frame memories 426, 427, and 428, and the write operation is not performed as the gray level signal of the current frame is recorded. The gray level signal prestored in the two frame memories is output to the data gray level signal converter 444.

More specifically, as shown in FIG. 14A, as the gray level signal G _n of the current frame is recorded in the second frame memory 427, the first frame memory 426 may store the gray level signal of the previous two frames. G _n-2 ) is output to the data gradation signal converter 444, and the third frame memory 428 outputs the pre-stored gradation signal G _n-1 to the data gradation signal converter 444. .

In this case, when the frequency that can be used to perform the storage operation of each frame memory is 30 Hz, the frequency used to perform the output operation is 60 Hz, and when the storage operation frequency of each frame memory is 60 Hz, the output operation frequency Is 120 ms.

As described above, in the case of a computer video signal using a sequential scanning method in which the number of fields per second and the frame number coincide, the number of fields per second is doubled, and one frame is duplicated so that two fields are output. For example, in the case of 60 frames / sec, the LCD panel is driven at 120 Hz after generating 120 fields per second by duplicating every frame.

In this case, a total of three frame memories may be configured. In the first memory 426, an image signal input from the current frame is recorded at 60 Hz, and the second memory 427 stores an image signal recorded one frame earlier. The image signal recorded two frames before is stored in the third memory 428.

The controller 430 reads 120 ms (two times in one frame) from the second memory 427 and the third memory 428 in the current frame and outputs it to the data gradation signal converter 444, which is input in the next frame. The signal is received by the third memory 428, and the controller 430 reads out an image signal from the first and second memories 426 and 427 and outputs the image signal to the data gradation signal converter 444. In this manner, the first, second, and third memories 426 (427) 428 sequentially perform write and output operations. Here, the classified memory may be a memory divided into a physical concept or a memory divided into a logical concept.

As described above, regardless of whether the first subframe (n ⁺ ) or the second subframe (n ⁻ ) of the two subframes divided into one frame is input to the data gray level signal converter 444. The gray level signal is the same as the gray level signal G _n of the current frame and the gray level signal G _n-1 of the previous frame.

Therefore, according to the frame detection signal 431 output from the controller 430, determining which one of the two gray levels signals G _n and G _n-1 is to be output is one of the steps of the data gray level signal converter 444. You can go anywhere.

For example, the data gradation signal converter is separately configured as a data gradation signal converter for the positive (+) subframe and a data gradation signal converter for the negative (-) subframe to determine which path to receive and output the frame detection signal. And a method for outputting a corrected gray scale value along the specific path.

In addition, as an opposite example, a method of outputting two correction values simultaneously in one data gray level signal converter and selectively outputting the outputs according to a frame signal without configuring a separate data gray level signal converter may be used. One or two mixing methods may be used.

Although the above has been described with reference to a preferred embodiment of the present invention, those skilled in the art will be able to variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. It will be appreciated.

As described above, when the gray level signal of the current frame, which is larger than the gray level signal of the previous frame, is input by using two subframes time-divided into one frame in the moving picture representation of the liquid crystal display according to the present invention, the first subframe When driving, the overshoot driving is performed, and when the second sub-frame is driven, the down driving is performed to the target level, thereby eliminating the screen drag when the LCD is implemented.

In addition, when the gray level signal of the current frame smaller than the gray level signal of the previous frame is input using two time-divided subframes, the undershoot driving is performed when the first subframe is driven, and then when the second subframe is driven. By driving up to the target level, the screen dragging can be eliminated when the LCD is implemented.

Claims (21)

The gradation data frame of the image signal provided from the data gradation signal source is divided into at least two subframes, and corrected by overshoot or undershoot driving according to the comparison of the gradation signal of the previous frame with the gradation signal of the current frame. A data gradation signal correction unit for outputting gradation data; A data driver unit receiving the corrected grayscale data through the overshoot or undershoot driving to change the data voltage to a data voltage corresponding to the corrected grayscale data to output an image signal; A gate driver unit sequentially supplying scan signals; And A plurality of gate lines transferring the scan signal, a plurality of data lines transferring the image signal and insulated from and intersecting the gate lines, and formed in an area surrounded by the gate lines and the data lines, respectively; And a plurality of pixels arranged in a matrix form having switching elements connected to the data lines. Liquid crystal display having a video correction function comprising a. The data gradation signal correcting unit of claim 1, When the gray level signal of the current frame which is larger than the gray level signal of the previous frame is input, the first corrected gray level data is output through overshoot driving in the subframe located in the first half of the divided image frame, and the sub located in the second half. And a second corrected gray level data through down-driving the overshooted value to a target value in a frame. The data gradation signal correcting unit of claim 1, When the gray level signal of the current frame which is smaller than the gray level signal of the previous frame is input, the sub-frame positioned in the first half of the divided image frame outputs the third corrected gray level data by undershoot driving, and the sub-frame positioned in the second half. And a fourth corrected gray level data through the up-driving the undershooted value to a target value in a frame. The liquid crystal display of claim 1, wherein the data gray level signal correcting unit provides the corrected gray level data to the data driver using an interlaced scanning method. The data gradation signal corrector of claim 4, A controller configured to output a first control signal for writing and reading grayscale data when the first subframe is driven, and to output a second control signal for writing and reading grayscale data when the second subframe is driven; When the first control signal is input from the controller when the first sub frame is driven, the gray data of the current frame provided from the data gray scale source is stored, and when the second sub frame is driven, the gray data of the current frame is output. A first memory; A second memory configured to output grayscale data of a previous frame when a second control signal is input from the controller when driving the first subframe and the second subframe; And When driving the first subframe, the grayscale data of the current frame is received from the data grayscale signal source, the grayscale data of the previous frame is received from the second frame memory, and the corrected grayscale data is output. At the same time, a data gradation signal converter which receives the gradation data of the current frame from the first frame memory, receives the gradation data of the previous frame from the second frame memory, and outputs the corrected gradation data to the data driver. Liquid crystal display having a moving picture correction function, comprising a. The liquid crystal display of claim 1, wherein the data gray level signal correcting unit provides the corrected gray level data to the data driver using a sequential scanning method. The data gradation signal corrector of claim 6, Outputs the grayscale data of the (n-2) th frame pre-stored when driving the nth frame, stores the grayscale data of the (n + 1) th frame when driving the (n + 1) th frame, and stores the (n + 2) th A first memory configured to output grayscale data of a (n + 1) th frame pre-stored when driving the frame; Save grayscale data when driving nth frame, output grayscale data of previously stored nth frame when driving (n + 1) th frame, and output grayscale data of previously stored nth frame when driving (n + 2) th frame A second memory to output; Outputs the grayscale data of the (n-1) th frame pre-stored when driving the nth frame, and outputs the (n-1) th frame grayscale data pre-stored when the (n + 1) th frame is driven, and (n + 2) A third memory configured to store the grayscale data of the (n + 2) th frame when the second frame is driven; A controller for controlling the writing and reading of the gradation data of the first to third memories; And The grayscale data provided from the first and third memories is output when the nth frame is driven, and the corrected grayscale data is output. The grayscale data provided from the second and third memories is output when the (n + 1) th frame is driven. A data gradation signal converter for outputting the corrected gradation data by receiving the gradation data provided from the first and second memories when the (n + 2) th frame is driven. Liquid crystal display having a moving picture correction function, comprising a. The display apparatus of claim 6, wherein a storage frequency of the grayscale data stored in the first to third memories is stored as a first frequency, and an output frequency of the grayscale data output from the first to third memories is equal to or greater than that of the first frequency. It is a 2nd frequency of 2 times, The liquid crystal display device which has a moving image correction function characterized by the above-mentioned. The liquid crystal display device according to claim 5 or 7, wherein the memory is a frame memory. A driving device of a liquid crystal display device which receives grayscale data of an image signal from a data grayscale signal source and outputs the grayscale data to a liquid crystal display module. The gradation data frame of the image signal provided from the data gradation signal source is divided into at least two subframes, and corrected by overshoot or undershoot driving according to the comparison of the gradation signal of the previous frame with the gradation signal of the current frame. Data gradation signal correction unit for outputting gradation data to the liquid crystal display module to speed up the response speed of the liquid crystal A driving device of the liquid crystal display device having a moving image correction function comprising a. The data gradation signal corrector of claim 10, When the gray level signal of the current frame which is larger than the gray level signal of the previous frame is input, the first corrected gray level data is output through overshoot driving in the subframe located in the first half of the divided image frame, and the sub located in the second half. And a second corrected gray level data is output through the down-driving of the overshooted value to the target value in the frame. The data gradation signal corrector of claim 10, When the gray level signal of the current frame which is smaller than the gray level signal of the previous frame is input, the sub-frame positioned in the first half of the divided image frame outputs the third corrected gray level data by undershoot driving, and the sub-frame positioned in the second half. And a fourth corrected gray level data is output through the up-driving of the undershooted value to a target value in the frame. The driving apparatus of claim 10, wherein the data gray level signal correction unit provides the corrected gray level data to the liquid crystal display module using an interlaced scanning method. The data gradation signal corrector of claim 13, A controller configured to output a first control signal for writing and reading grayscale data when the first subframe is driven, and to output a second control signal for writing and reading grayscale data when the second subframe is driven; When the first control signal is input from the controller when the first sub frame is driven, the gray data of the current frame provided from the data gray scale source is stored, and when the second sub frame is driven, the gray data of the current frame is output. A first memory; A second memory configured to output grayscale data of a previous frame when a second control signal is input from the controller when driving the first subframe and the second subframe; And When driving the first subframe, the grayscale data of the current frame is received from the data grayscale signal source, the grayscale data of the previous frame is received from the second frame memory, and the corrected grayscale data is output. At the same time, a data gradation signal converter which receives the gradation data of the current frame from the first frame memory, receives the gradation data of the previous frame from the second frame memory, and outputs the corrected gradation data to the data driver. And a driving apparatus of the liquid crystal display device having a moving image correction function. The driving apparatus of claim 10, wherein the data gray level signal correction unit provides the corrected gray level data to the liquid crystal display module using a sequential scanning method. The data gray signal correcting unit of claim 15, Outputs the grayscale data of the (n-2) th frame pre-stored when driving the nth frame, stores the grayscale data of the (n + 1) th frame when driving the (n + 1) th frame, and stores the (n + 2) th A first memory configured to output grayscale data of a (n + 1) th frame pre-stored when driving the frame; Save grayscale data when driving nth frame, output grayscale data of previously stored nth frame when driving (n + 1) th frame, and output grayscale data of previously stored nth frame when driving (n + 2) th frame A second memory to output; Outputs the grayscale data of the (n-1) th frame pre-stored when driving the nth frame, and outputs the (n-1) th frame grayscale data pre-stored when the (n + 1) th frame is driven, and (n + 2) A third memory configured to store the grayscale data of the (n + 2) th frame when the second frame is driven; A controller for controlling the writing and reading of the gradation data of the first to third memories; And The grayscale data provided from the first and third memories is output when the nth frame is driven, and the corrected grayscale data is output. The grayscale data provided from the second and third memories is output when the (n + 1) th frame is driven. A data gradation signal converter for outputting the corrected gradation data by receiving the gradation data provided from the first and second memories when the (n + 2) th frame is driven. And a driving apparatus of the liquid crystal display device having a moving image correction function. 17. The apparatus of claim 16, wherein the storage frequency of the grayscale data stored in the first to third memories is stored as a first frequency, and the output frequency of the grayscale data output from the first to third memories is equal to the first frequency. 2. A drive device for a liquid crystal display device having a moving picture correction function, characterized in that it is a second frequency which is twice multiple. 17. The driving apparatus of the liquid crystal display device according to claim 14 or 16, wherein the memory is a frame memory. A matrix type having a plurality of gate lines, a plurality of data lines insulated from and intersecting the gate lines, a region surrounded by the gate lines and data lines, and connected to the gate lines and data lines, respectively, and having a switching element In the driving method of a liquid crystal display device comprising a plurality of arranged pixels, (a) sequentially supplying a scan signal to the gate line; (b) dividing one picture frame provided from an external data gradation signal source into at least two subframes; (c) comparing the gray level signal of the current frame with the gray level signal of the previous frame as a gray level signal of the current frame is input; (d) If it is checked in step (c) that the gray level signal of the current frame is larger than the gray level signal of the previous frame, the overshoot driving is performed when the subframe located in the first half of the divided subframes is driven. Generating a data driving voltage and generating a second data driving voltage by driving down the overshooted value to a target value when driving the subframe positioned in the second half of the divided subframes; (e) If it is checked in step (c) that the gray level signal of the previous frame is smaller than the gray level signal of the current frame, undershoot driving is performed when the subframe located in the first half of the divided subframes is driven. Generating a data driving voltage and generating a fourth data driving voltage by performing an up-driving of the undershooted value to a target value when driving the subframe positioned in the second half of the divided subframes; (f) supplying the first to fourth data driving voltages generated in the step (c) and the step (d) to the data line. And a method of driving a liquid crystal display device having a moving image correction function, which speeds up the response speed of the liquid crystal. 20. The method of claim 19, wherein in step (c), when it is checked that the magnitude of the gray level signal of the previous frame and the gray level signal of the current frame are the same, the uncorrected gray level signal is bypassed and corresponds to the bypassed gray level signal. And supplying a data driving voltage to the data line. The method of claim 19, wherein when the divided subframes are two, The subframe located in the first half is the first subframe, And a subframe positioned at the second half is a second subframe.