KR20080000340A - Appratus and method for driving lcd - Google Patents

Abstract

An apparatus for driving an LCD(Liquid Crystal Display) device and a driving method thereof are provided to improve motion blur by preventing flicker due to the double speed of frame frequency. An apparatus for driving an LCD(Liquid Crystal Display) device includes a frequency converting unit(210), a frame determining unit(220), a gray scale converting unit(230), and a selecting unit(240). The frequency converting unit converts frame frequency and outputs continuously the same frames. The frame determining unit determines whether an input frame is a still image or a moving image frame and outputs one of first and second selection signals based on the determination. The gray scale converting unit converts the gray scale values of pixels of frames from the frequency converting unit. The selecting unit outputs still image frames, which are inputted from the frequency converting unit, in response to the first selection signal or moving image frames, which are converted by the gray scale converting unit, in response to the second selection unit.

Description

Driving apparatus of liquid crystal display device and driving method thereof {Appratus and method for driving LCD}

1 is an equivalent circuit diagram of a pixel formed in a general liquid crystal display device.

2 is a configuration diagram of a general liquid crystal display device.

3 is a configuration diagram of a driving device of a liquid crystal display device according to an exemplary embodiment of the present invention.

4 is a gray scale conversion characteristic diagram in a driving device of a liquid crystal display device according to the present invention;

5 is a gray scale characteristic diagram of a still image frame in the driving apparatus of the liquid crystal display according to the present invention;

FIG. 6 is a configuration diagram of the frequency converter in FIG. 3. FIG.

7 is a configuration diagram of a frame discriminator in FIG. 3.

8 is a configuration diagram of a gradation converter in FIG. 3;

9 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 10 is a flowchart illustrating a frame frequency conversion process in FIG. 9 in detail. FIG.

FIG. 11 is a flowchart illustrating a process of converting grayscale values of frames in FIG. 9; FIG.

12 is a flowchart illustrating a process of generating a selection signal in FIG. 9 in detail.

Explanation of symbols on the main parts of the drawings

100: liquid crystal display device 110: liquid crystal display panel

120: data driver 130: gate driver

140: gamma reference voltage generator 150: backlight assembly

160: inverter 170: common voltage generator

180: gate driving voltage generator 190: timing controller

200: driving device of the liquid crystal display 210: frequency converter

220: frame discriminator 230: gradation converter

240: multiplexer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device. In particular, in a liquid crystal display device having a double frame frequency, the same still image frames having no gray level value are continuously driven within a predetermined time, and the same video frames having a gray level value are fixed. The present invention relates to a driving device and a driving method of a liquid crystal display device which can be driven continuously within time.

A liquid crystal display device displays an image by adjusting light transmittance of liquid crystal cells according to a video signal, and an active matrix type liquid crystal display device in which a switching element is formed for each liquid crystal cell enables active control of the switching element. This is advantageous for video implementation. As the switching element used in the active matrix liquid crystal display device, a thin film transistor (hereinafter referred to as TFT) is mainly used as shown in FIG. 1.

Referring to FIG. 1, an active matrix type liquid crystal display converts digital input data into an analog data voltage based on a gamma reference voltage and supplies it to the data line DL and simultaneously supplies scan pulses to the gate line GL. The liquid crystal cell Clc is charged.

The gate electrode of the TFT is connected to the gate line GL, the source electrode is connected to the data line DL, and the drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and one electrode of the storage capacitor Cst. Connected.

The common voltage Vcom is supplied to the common electrode of the liquid crystal cell Clc.

The storage capacitor Cst charges a data voltage applied from the data line DL when the TFT is turned on, thereby maintaining a constant voltage of the liquid crystal cell Clc.

When the scan pulse is applied to the gate line GL, the TFT is turned on to form a channel between the source electrode and the drain electrode so that the voltage on the data line DL is applied to the pixel electrode of the liquid crystal cell Clc. Supply. At this time, the liquid crystal molecules of the liquid crystal cell Clc modulate the incident light by changing the arrangement by the electric field between the pixel electrode and the common electrode.

A configuration of a general liquid crystal display device having pixels having such a structure will be described with reference to FIG. 2.

2 is a configuration diagram of a general liquid crystal display device.

Referring to FIG. 2, the liquid crystal display device 100 includes a thin film transistor TFT for driving data lines DL1 to DLm and gate lines GL1 to GLn and driving the liquid crystal cell Clc at an intersection thereof. A liquid crystal display panel 110 having a thin film transistor, a data driver 120 for supplying data to the data lines DL1 to DLm of the liquid crystal display panel 110, and a gate of the liquid crystal display panel 110. A gate driver 130 for supplying scan pulses to the lines GL1 to GLn, a gamma reference voltage generator 140 for generating a gamma reference voltage and supplying it to the data driver 120, and a liquid crystal display panel 110. ) Generates a backlight assembly 150 for irradiating light, an inverter 160 for applying an alternating voltage and current to the backlight assembly 160, and a common voltage Vcom to generate liquid crystals of the liquid crystal display panel 110. A common voltage generator 170 for supplying the common electrode of the cell Clc, A timing for controlling the gate driving voltage generator 180 for generating the high voltage VGH and the gate low voltage VGL and supplying the gate voltage 130 to the gate driver 130, and for controlling the data driver 120 and the gate driver 130. The controller 190 is provided.

In the liquid crystal display panel 110, liquid crystal is injected between two glass substrates. The data lines DL1 to DLm and the gate lines GL1 to GLn are orthogonal to the lower glass substrate of the liquid crystal display panel 110. TFTs are formed at intersections of the data lines DL1 to DLm and the gate lines GL1 to GLn. The TFT supplies the data on the data lines DL1 to DLm to the liquid crystal cell Clc in response to the scan pulse. The gate electrodes of the TFTs are connected to the gate lines GL1 to GLn, and the source electrodes of the TFTs are connected to the data lines DL1 to DLm. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc and the storage capacitor Cst.

The TFT is turned on in response to the scan pulse supplied to the gate terminal via the gate lines GL1 to GLn. When the TFT is turned on, video data on the data lines DL1 to DLm is supplied to the pixel electrode of the liquid crystal cell Clc.

The data driver 120 supplies data to the data lines DL1 to DLm in response to the data driving control signal DDC supplied from the timing controller 190, and digital video data supplied from the timing controller 190. After sampling and latching the RGB, the liquid crystal cell Clc of the liquid crystal display panel 110 is converted into an analog data voltage capable of expressing gray scale based on the gamma reference voltage supplied from the gamma reference voltage generator 140. Supply to the data lines DL1 to DLm.

The gate driver 130 sequentially generates scan pulses, that is, gate pulses, in response to the gate driving control signal GDC and the gate shift clock GSC supplied from the timing controller 190, thereby providing the gate lines GL1 to GLn. To feed. In this case, the gate driver 130 determines the high level voltage and the low level voltage of the scan pulse based on the gate high voltage VGH and the gate low voltage VGL supplied from the gate driving voltage generator 180.

The gamma reference voltage generator 140 receives a high potential power supply voltage VDD to generate a positive gamma reference voltage and a negative gamma reference voltage and output the same to the data driver 120.

The backlight assembly 150 is disposed on the rear surface of the liquid crystal display panel 110, and emits light by an AC voltage and a current supplied from the inverter 160 to irradiate light to each pixel of the liquid crystal display panel 110.

The inverter 160 converts the square wave signal generated therein into a triangular wave signal and compares the triangular wave signal with a DC power supply voltage (VCC) supplied from the system to generate a burst dimming signal proportional to the comparison result. . When a burst dimming signal determined according to an internal square wave signal is generated, a driving IC (not shown) for controlling the generation of AC voltage and current in the inverter 160 is supplied to the backlight assembly 150 according to the burst dimming signal. Control the generation of alternating voltage and current.

The common voltage generator 170 receives the high potential power voltage VDD to generate the common voltage Vcom and supplies the common voltage Vcom to the common electrodes of the liquid crystal cells Clc of each pixel of the liquid crystal display panel 110.

The gate driving voltage generator 180 receives the high potential power voltage VDD to generate the gate high voltage VGH and the gate low voltage VGL to supply the gate driver 130 to the gate driver 130. Here, the gate driving voltage generation unit 180 generates a gate high voltage VGH that is greater than or equal to the threshold voltage of the TFTs provided in each pixel of the liquid crystal display panel 110, and the gate low voltage that is less than or equal to the threshold voltage of the TFT. VGL). The gate high voltage VGH and the gate low voltage VGL generated in this way are used to determine the high level voltage and the low level voltage of the scan pulse generated by the gate driver 130, respectively.

The timing controller 190 supplies digital video data RGB, which is supplied from a digital video card (not shown), to the data driver 120, and also horizontal / vertical synchronization signals H and V according to the clock signal CLK. The data driving control signal DDC and the gate driving control signal GDC may be generated and supplied to the data driver 120 and the gate driver 130, respectively. The data driving control signal DDC includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, and a gate driving control signal GDC. ) Includes a gate start pulse (GSP) and a gate output enable (GOE).

The liquid crystal display device 100 having such a configuration and function is generally driven at 60 Hz, but in recent years, a technique for driving the liquid crystal display device 100 at 120 Hz has been developed in order to improve moving images.

When the liquid crystal display 100 is driven at 120 Hz, gray data conversion is performed while maintaining the average luminance of two frames the same as that of one frame when driven at 60 Hz. Flicker is visible to the naked eye due to the alternating display of low gray on the screen.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to continuously drive the same still image frames that are not converted to gray scale values within a predetermined time in a liquid crystal display device that doubles the frame frequency. The present invention provides a driving device and a driving method of a liquid crystal display device capable of continuously driving the same moving picture frames having a converted value within a predetermined time.

Disclosure of Invention An object of the present invention is to provide a driving device and a driving method of a liquid crystal display device capable of continuously driving the same still image frames within a predetermined time period without converting the gray level values of the still image frames in the liquid crystal display device that doubles the frame frequency. There is.

Disclosure of Invention An object of the present invention is to provide a flicker generated in a still image frame due to a double speed of a frame frequency by continuously driving the same still image frames within a predetermined time without converting the gray level values of the still image frames in a liquid crystal display device to double the frame frequency. It is to provide a driving device and a driving method of the liquid crystal display device that can be prevented.

The driving apparatus of the liquid crystal display device of the present invention for achieving the above object comprises: a frequency conversion means for continuously receiving the frame to convert the frame frequency to output the same frame continuously; Frame discriminating means for determining whether the input frame is a still image or a moving image frame and selectively outputting the first and second selection signals according to the determination result; Gradation converting means for converting gradation values of pixels of moving picture frames which are successively input from said frequency converting means; And outputting still image frames continuously input from the frequency conversion means in response to the first selection signal to a frame output terminal, or outputting video frames continuously input from the gray level conversion means in response to the second selection signal. Selecting means for outputting to.

The frequency converting means may include: a storage unit for temporarily storing an input frame; And a frequency conversion controller configured to temporarily store the input frame in the storage unit, double the first frame frequency to the second frame frequency, and continuously read and output the frame in the storage unit within a predetermined time.

The frame discrimination unit may include a storage unit for storing one or more previous frames of the input current frame; A frame discrimination controller configured to store the previous frame in the storage unit, and read out the previous frame as the current frame is input to control determination of an image state of the current frame; A system value calculation unit for calculating gray level difference values of corresponding pixels of the previous frame and the current frame under the control of the frame determination unit; An adder for adding the calculated gray level differences according to the control of the frame discrimination controller; And comparing the addition value added by the adding unit with a predetermined reference gradation value under the control of the frame discrimination control unit, and generating the first selection signal or the second selection signal according to a comparison result to the selection means. And a selection signal generator for outputting.

The selection signal generation unit may determine that the current frame is a still image frame and generate the first selection signal and output the generated selection signal to the selection means when the addition value is smaller than the predetermined reference gradation value.

The selection signal generator may determine the current frame as a moving picture frame and generate the second selection signal to output the selection means if the addition value is greater than the predetermined reference gray value.

The gray level value calculating unit may calculate gray level differences between the current frame and corresponding pixels of one previous frame.

The gradation value calculator may calculate gradation difference values of pixels corresponding to the current frame and at least two previous frames.

The gradation converting means may include: a gradation detector for detecting gradation values of pixels of the same frames continuously input from the frequency converting means within a predetermined time; A gray scale calculator for calculating a low gray scale conversion value and a high gray scale converted value to be converted by using the gray scale value detected by the gray scale detector and a predetermined reference gray scale value; And a gray scale converter for converting the gray scales of pixels of the odd and even frames among the inputted same frames to the calculated low gray scale conversion value and the high gray scale conversion value, respectively. The gray level converting means converts the gray levels of the pixels of the odd and even frames so that the luminance values of the pixels of the current frame remain the same.

The selecting means comprises: a multiplexer having a selection terminal connected to an output terminal of the frame discriminating means, an input terminal connected to an output terminal of the frequency converting means and an output terminal of the gradation converting means, and an output terminal connected to the frame output terminal. Include.

In the driving method of the liquid crystal display according to the present invention, when the current frame is input while the previous frame is stored, the same still image frames or video frames are continuously driven within a predetermined time by converting the first frame frequency into the second frame frequency. Generating them; Converting a gray value of pixels of the generated video frames to be driven at the second frame frequency; Determining whether the current frame is a still image or a moving image frame using the previous frame and generating a first selection signal or a second selection signal according to a determination result; And continuously outputting the generated still image frames in response to the first selection signal or continuously outputting the converted video frames in response to the second selection signal.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

3 is a configuration diagram of a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the driving device 200 of the liquid crystal display device of the present invention includes a frequency converter 210 for receiving a frame, converting a frame frequency to continuously output the same frames within a predetermined time, and an input frame A frame discriminator 220 for judging whether the image is a still image or a video frame and selectively outputting the first and second selection signals according to the determination result, and the gray level of the pixels of frames continuously input from the frequency converter 210. A gradation converter 230 for converting values, and outputting still image frames continuously input from the frequency converter 210 in response to the first selection signal, or continuously from the gradation converter 230 in response to the second selection signal. And a multiplexer 240 for outputting input video frames.

The frequency converter 210 temporarily stores the input frame, doubles the first frame frequency to the second frame frequency, and continuously reads the stored frame within a predetermined time, thereby adjusting the gray scale converter 230 and the multiplexer 240. Output to the input terminal of. Here, the frequency converter 210 doubles the frame frequency by a dynamic data insertion (DDI) method. More specifically, the frequency converter 210 temporarily stores the input current frame and reads it twice within a predetermined time to continuously read the same frame. Output it.

When the current frame is input through the frame input terminal, the frequency converter 210 converts the first frame frequency of 60 Hz to the second frame frequency of 120 Hz, but is not limited thereto. For example, the frequency converter 210 may be implemented to convert the first frame frequency of 50 Hz to the second frame frequency of 60 Hz.

The frame discriminator 220 stores the previous frame of the input current frame, reads the previous frame as the current frame is input, and calculates gray level differences between the previous frame and the corresponding pixels of the current frame. Subsequently, the frame discriminator 220 adds the calculated gradation difference values, compares the added value with a predetermined reference gradation value, and generates a first selection signal or a second selection signal according to a comparison result, and multiplexer 240. Will output

The gray scale converter 230 detects the gray scale values of the pixels of the same frames continuously input from the frequency converter 210 within a predetermined time, and then converts the gray scale values by using the detected gray scale value and a predetermined reference gray scale value. Calculate the converted value and the high gradation converted value. Subsequently, the gray scale converter 230 converts the gray scales by shifting the gray scales of the pixels of the odd and even frames to the low gray scale conversion value and the high gray scale conversion value, respectively. As shown in FIGS. 4A and 4B, the gray scale converter 230 converts the gray scale value 'DG' of the pixel of the inputted odd frame into the low gray scale converted value 'LG', and simultaneously The gray level value 'DG' of the input pixel of the even-th frame is converted into the high gray scale conversion value 'HG'.

The multiplexer 240 includes a selection terminal connected to the output terminal of the frame discriminator 220, an input terminal connected to the output terminal of the frequency converter 210 and an output terminal of the gradation converter 230, and an output terminal connected to the frame output terminal. Have

When the first selection signal '0' indicating the output of the still image from the frame discriminator 220 is input to the selection terminal, the multiplexer 240 outputs the frequency from the frequency converter 210 in response to the first selection signal '0'. Continuously input still image frames are output to the frame output terminal. In this case, as shown in FIGS. 5A and 5B, since the frequency converter 210 continuously outputs the same still image frame without converting the grayscale values of the pixels of the still image frame, the multiplexer 240 is the same. The odd-numbered and even-numbered frames having gray values are successively output to the frame output terminal.

When the second selection signal '1' indicating the output of the video from the frame discriminator 220 is input to the selection terminal, the multiplexer 240 continuously outputs the gray level converter 230 in response to the second selection signal '1'. Outputs video frames input to the frame output terminal. In this case, the multiplexer 240 continuously outputs the odd-numbered frame in which the gray value is converted as shown in (A) of FIG. 4 and the even-numbered frame in which the gray value is converted as in (B) of FIG. 4.

6 is a configuration diagram of the frequency converter in FIG. 3.

Referring to FIG. 6, the frequency converter 210 temporarily stores the input frame in the storage unit 211, temporarily stores the input frame in the storage unit 211, and stores the first frame frequency in the second frame. A frequency conversion control unit 212 is provided to output the frame of the storage unit 211 continuously at a predetermined frequency and output the same within a predetermined time.

The storage unit 211 may be implemented as a virtual memory as a memory device for storing frame information. The storage unit 211 temporarily stores the current frame written by the frequency conversion control unit 212.

When the current frame is input through the frame input terminal, the frequency conversion control unit 212 temporarily stores the current frame in the storage unit 211, reads out the frame of the storage unit 211 twice within a predetermined time, and continuously converts the gray scale converter ( By outputting to the input terminal 230 and the multiplexer 240, the first frame frequency is converted into a second frame frequency.

FIG. 7 is a configuration diagram of the frame discriminator in FIG. 3.

Referring to FIG. 7, the frame discriminator 220 stores a storage unit 221 for storing one or more previous frames of the input current frame, stores the previous frame in the storage unit 221, and inputs the current frame. The gray level difference value of the corresponding pixels of the previous frame and the current frame according to the control of the frame determination unit 222 and the frame determination unit 222 for controlling the determination of the image state of the current frame by reading the previous frame. An addition unit 224 for adding the tone difference values calculated by the even value calculation unit 223 under the control of the even-value calculation unit 223 and the frame discrimination control unit 222; According to the control of the frame discrimination controller 222, the addition value added by the adder 224 is compared with a predetermined reference gray value, and according to a comparison result, a first selection signal or a second selection signal is generated and a multiplexer ( Output to 240) And a selection signal generating section 225 for group.

The storage unit 221 stores one or more previous frames written by the frame determination controller 222.

The frame discrimination control unit 222 stores the previous frame in the storage unit 221 and then, when the current frame is input through the frame input terminal, reads one or more previous frames from the storage unit 221 to determine one or more previous frames and the current frame. The gradation value calculation unit 223 outputs the gradation value. When the gray scale difference values calculated from the gray scale calculator 223 are input, the frame determination controller 222 transfers the calculated gray scale difference values to the adder 224. When the added value added from the adder 224 is input, the frame discrimination controller 222 transfers the inputted added value to the selection signal generator 225.

Even if the current frame and the previous frame are input from the frame discrimination controller 222, the value calculating unit 223 calculates gray level differences between the pixels corresponding to the previous frame and the current frame and outputs the gray level differences to the frame discrimination controller 222. .

Although the present invention is implemented such that the value calculating unit 223 calculates the gray level difference values using one previous frame and the current frame, the present invention is not limited thereto. It may be implemented to calculate gray level differences using the frames and the current frame. In this case, the frame discrimination control unit 222 reads a plurality of previous frames from the storage unit 221 and transfers the previous frames to the value calculating unit 223.

When the gray level difference values calculated by the gray level calculation unit 223 are input, the adder 224 adds all of the gray level difference values and outputs the added value to the frame discrimination controller 222.

When the addition value added by the adder 224 is input, the selection signal generator 225 compares the addition value with a predetermined reference gray value and generates a first selection signal or a second selection signal according to a comparison result. And output to the multiplexer 240. As a result of the comparison, if the added value is smaller than the predetermined reference gradation value, the selection signal generator 225 determines the current frame as a still image frame, generates a first selection signal '0', and outputs the first selection signal '0' to the multiplexer 240. As a result of the comparison, if the added value is larger than the predetermined reference gray value, the selection signal generator 225 determines the current frame as the moving picture frame, generates a second selection signal '1', and outputs the second selection signal '1' to the multiplexer 240.

FIG. 8 is a configuration diagram of a gradation converter in FIG. 3.

Referring to FIG. 8, the gray scale converter 230 may include a gray scale detector 231 and a gray scale detector 231 for detecting gray scale values of pixels of the same frames that are continuously input from the frequency converter 230 within a predetermined time. A gray scale calculator 232 for calculating a low gray scale value and a high gray scale value to be converted using the gray scale value detected by the predetermined gray scale value and a predetermined reference gray scale value, and the gray scales of pixels of the odd and even frames. A gradation conversion section 223 for converting gradations by shifting the low gradation conversion value and the high gradation conversion value calculated by the gradation calculator 232, respectively, is provided.

The gray level detector 231 detects gray values of pixels of the same frames continuously input from the frequency converter 210 within a predetermined time period, and outputs the gray level values to the gray scale calculator 232.

The gray scale calculator 232 calculates a low gray scale converted value to be converted by subtracting a predetermined reference gray value from the gray scale value detected by the gray scale detector 231, and simultaneously detects the gray scale detected by the gray scale value detector 231. A predetermined reference gradation value is added to the value to calculate a high gradation conversion value to be converted. For example, when the gradation value detected by the gradation detector 231 is '50 gradation 'and the predetermined reference gradation value is' 8 gradation ', the gradation calculator 232 selects from the detected gradation value '50 gradation'. The reference gray scale value '8 gray scales' is calculated by subtracting the reference gray scale value' 8 gray scales', and the predetermined gray scale value '8 gray scales' is added to the detected gray scale value '50 gray scales'. 58 gradations' are calculated and output to the gradation converter 233.

The gray level converter 233 converts the grays of the pixels of the odd frame among the same frames continuously input within a predetermined time period to the low gray level conversion value calculated by the gray scale calculator 232, and converts them to low grays. At the same time, the gradation of the pixels of the even-numbered frame is shifted to the high gradation conversion value calculated by the gradation calculator 232, converted to high gradation, and output to the multiplexer 240. For example, when the gray level value of the pixel of the inputted odd frame is '50 gray level 'and the calculated low gray level conversion value is '42 gray level', the gray level converter 233 adjusts the gray level of the pixel of the inputted odd frame. Convert to 42 gradations. In addition, if the gray value of the pixel of the even-numbered frame is '50 gray 'and the calculated high gray level conversion value is '58 -gradation', the gray level converter 233 adjusts the gray level of the pixel of the input even-numbered frame to '58'. To 'gradation'.

The gray scale conversion method of the gray scale converter 233 will be described with reference to FIG. 4, and the gray scale converter 233 may adjust the gray scale value 'DG' of the pixel of the odd-numbered frame as shown in FIG. 4A. The gray scale value 'DG' of the pixel of the even-numbered frame inputted as shown in FIG. 4B is converted into the calculated high gray scale conversion value 'HG'.

The frame output terminal is connected to an input terminal of the timing controller 190 of the liquid crystal display device 100. Therefore, the frame output from the multiplexer 240 is input to the timing controller 190. Accordingly, the timing controller 190 continuously drives the odd-numbered and even-numbered still image frames, which are doubled from the frame frequency of 60 Hz to the frame frequency of 120 Hz and whose gradation values are not converted, within a predetermined period of time. Or the odd-numbered and even-numbered moving picture frames, which are doubled from a frame frequency of 60 Hz to a frame frequency of 120 Hz and whose gray levels are converted, are continuously driven to the liquid crystal display panel 110 within a predetermined time.

As described above, the present invention converts the grayscale values of the same moving picture frames that are continuously driven within a predetermined time after the frame frequency is assigned by the frequency converter 210, while the grayscales of the same still image frames that are continuously driven within the predetermined time are converted. By not converting the values, flicker generated in still image frames due to the double speed of the frame frequency can be prevented, thereby improving the motion blur.

A driving process of the liquid crystal display device of the present invention having the configuration and function as described above will be described with reference to a flowchart.

9 is a flowchart illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention. However, a process of processing the current frame while the previous frame is stored in the frame discriminator 220 will be described.

Referring to FIG. 9, when a current frame output from a scaler (not shown) included in a system such as a television receiver or a computer monitor is input through a frame input terminal (S810), the frequency converter 210 temporarily stores the current frame. After that, the first frame frequency is doubled to the second frame frequency to generate the same still image frames or video frames continuously driven within a predetermined time (S820). The gray level converter 230 converts the gray level values of the pixels of the frames generated by the frequency converter 210 to be driven at the second frame frequency as shown in FIG. 4 (S830).

In this case, the frame discriminator 220 determines whether the current frame is a still image or a video frame by using a previously stored previous frame and generates a first selection signal or a second selection signal according to the determination result (S840).

When the first selection signal '0' is generated, the multiplexer 240 continuously outputs still image frames generated by the frequency converter 210 in response to the first selection signal '0' (S850).

If the second selection signal '1' is generated, the multiplexer 240 continuously outputs the grayscale-converted video frames by the gray converter 230 in response to the second selection signal '1' (S860).

As described above, when the input frame is a still image frame, the same still image frames assigned frequency by the frequency converter 210 are continuously output within a predetermined time period through the multiplexer 240, so that the same still image is not converted. The image frames are continuously driven within a predetermined time. In the present invention, when the input frame is a video frame, only video frames are selectively output through the multiplexer 240 among the frames gray-scaled by the gray scale converter 230 after the frequency is doubled, so that the grayscale video frames are constant. To be driven continuously in time.

10 is a detailed flowchart illustrating a frame frequency conversion process of FIG. 9.

Referring to FIG. 10, when the current frame is input through the frame input terminal, the frequency converter 210 temporarily stores the current frame (S821). In this state, the frequency converter 210 continuously reads the current frame stored twice in a predetermined time in order to double the first frame frequency to the second frame frequency (S822), and the same still image is continuously driven within the predetermined time. Frames or video frames are generated (S823).

FIG. 11 is a flowchart illustrating a process of converting grayscale values of frames in FIG. 9.

Referring to FIG. 11, when frames generated by the frequency converter 210 are continuously input, the gray scale converter 230 detects grayscale values of pixels of the same frames input (S831).

After the gray scale value is detected, the gray scale converter 230 calculates a low gray scale conversion value to be converted by subtracting a predetermined reference gray value from the detected gray scale value, and simultaneously converts the predetermined gray scale value to the detected gray scale value. The high gray scale conversion value to be added and calculated is calculated (S832).

Subsequently, the gradation converter 230 converts the gradations of pixels of the odd frame among the same input frames to the calculated low gradation conversion value and converts them to low gradations, and simultaneously calculates the gradations of the pixels of the even-numbered frame. The high gradation conversion value is shifted to the high gradation value and output to the multiplexer 240 (S833).

12 is a flowchart illustrating a process of generating a selection signal in FIG. 9.

Referring to FIG. 12, when the current frame is input through the frame input terminal in a state in which the previous frame is stored, the frame discriminator 220 reads out the stored previous frame (S841), and the gray level of the pixels corresponding to the previous frame and the current frame is read. After calculating the difference values (S842), all the calculated gray level differences are added to obtain an addition value (S843).

Subsequently, the frame discriminator 220 compares the addition value with the predetermined reference gradation value and determines whether the addition value is smaller than the predetermined reference gradation value (S844). If it is determined that the addition value is smaller than the predetermined reference gray value, the frame discriminator 220 determines that the current frame is a still image frame and generates a first selection signal '0' (S845). As a result of the determination, if the added value is larger than the predetermined reference gray value, the frame discriminator 220 determines that the current frame is a video frame and generates a second selection signal '1' (S846).

As described above, the present invention provides the same still image without converting the gradation value of still image frames, unlike continuously driving the same moving image frames whose gradation values are converted within a predetermined time in a liquid crystal display market value that doubles the frame frequency. By continuously driving the frames within a predetermined time, it is possible to prevent the flicker generated in the still image frame due to the double speed of the frame frequency, thereby improving the motion blur.

Although the technical spirit of the present invention has been described in detail according to the above-described preferred embodiment, it should be noted that the above-described embodiment is for the purpose of description and not of limitation. In addition, those skilled in the art will understand that various embodiments are possible within the scope of the technical idea of the present invention.

Claims (17)

Frequency converting means for receiving the frame and converting the frame frequency to continuously output the same frames; Frame discriminating means for determining whether the input frame is a still image or a moving image frame and selectively outputting the first and second selection signals according to the determination result; Gradation converting means for converting gradation values of pixels of frames successively input from said frequency converting means; And Outputs still image frames continuously input from the frequency converting means to the frame output terminal in response to the first selection signal, or moves video frames converted by the gray level converting means to the frame output terminal in response to the second selection signal. Selection means for output Driving device of the liquid crystal display device comprising a. The method of claim 1, The frequency converting means, A storage unit for temporarily storing the input frame; And A frequency conversion controller for temporarily storing an input frame in the storage unit, double-speeding a first frame frequency to a second frame frequency, and continuously reading and outputting the frame in the storage unit within a predetermined time; Driving device of the liquid crystal display device comprising a. The method of claim 2, Wherein the first frame frequency is 60 Hz, and the second frame frequency is 120 Hz. The method of claim 1, The frame discrimination means, A storage unit for storing one or more previous frames of the input current frame; A frame discrimination controller configured to store the previous frame in the storage unit, and read out the previous frame as the current frame is input to control determination of an image state of the current frame; A system value calculation unit for calculating gray level difference values of corresponding pixels of the previous frame and the current frame under the control of the frame determination unit; An adder for adding the calculated gray level differences according to the control of the frame discrimination controller; And Under the control of the frame discrimination controller, the added value added by the adder and a predetermined reference gradation value are compared to generate the first selection signal or the second selection signal according to a comparison result, and output them to the selection means. Selection signal generator for Driving device of the liquid crystal display device comprising a. The method of claim 4, wherein And when the addition value is smaller than the predetermined reference gradation value, the selection signal generation unit determines the current frame as a still image frame, and generates the first selection signal and outputs the first selection signal to the selection means. Drive of the device. The method of claim 4, wherein The selection signal generator may determine the current frame as a moving picture frame and generate the second selection signal and output the second selection signal to the selection means when the addition value is larger than the predetermined reference gray scale value. Drive system. The method according to any one of claims 4 to 6, And the gradation value calculating unit calculates gradation difference values between corresponding pixels of the current frame and one previous frame. The method according to any one of claims 4 to 6, And the gray level value calculating unit calculates gray level differences between the current frame and corresponding pixels of at least two or more previous frames. The method of claim 1, The gradation converting means, A gray scale detector for detecting gray scale values of pixels of the same frames continuously input from the frequency converting means within a predetermined time; A gray scale calculator for calculating a low gray scale conversion value and a high gray scale converted value to be converted by using the gray scale value detected by the gray scale detector and a predetermined reference gray scale value; And A gray level conversion unit for converting the gray level of pixels of the odd and even frames among the same input frames to the calculated low gray level conversion value and the high gray level conversion value, respectively. Driving device of the liquid crystal display device comprising a. The method of claim 9, The gray scale calculator calculates the low gray scale conversion value by subtracting the predetermined gray scale value from the detected gray scale value, and simultaneously adds the predetermined gray scale value to the detected gray scale value to calculate the high gray scale converted value. A drive device for a liquid crystal display device, characterized in that. The method of claim 9, And the gray level converting means converts the gray levels of the pixels of the odd and even frames so that the luminance values of the pixels of the current frame are the same. The method of claim 1, The selection means, A multiplexer having a selection terminal connected to an output terminal of the frame discriminating means, an input terminal connected to an output terminal of the frequency converting means and an output terminal of the gradation converting means, and an output terminal connected to the frame output terminal Driving device of the liquid crystal display device comprising a. When the current frame is input while the previous frame is stored, converting the first frame frequency to the second frame frequency to generate the same still image frames or video frames continuously driven within a predetermined time; Converting a gray value of pixels of the generated video frames to be driven at the second frame frequency; Determining whether the current frame is a still image or a moving image frame using the previous frame and generating a first selection signal or a second selection signal according to a determination result; And Continuously outputting the generated still image frames in response to the first selection signal or continuously outputting the grayscale-converted video frames in response to the second selection signal. Method of driving a liquid crystal display device comprising a. The method of claim 13, The frame generation step, Temporarily storing the current frame when the current frame is input; And Reading out the stored current frame twice in a predetermined time so as to double the first frame frequency to the second frame frequency to generate the same still image frames or video frames continuously driven within a predetermined time; Method of driving a liquid crystal display device comprising a. The method of claim 14, Wherein the first frame frequency is 60 Hz, and the second frame frequency is 120 Hz. The method of claim 13, The gray value conversion step, Detecting a gray value of the generated pixels of the same frames; Calculate a low gradation value to be converted by subtracting a predetermined reference gradation value from the detected gradation value, and simultaneously calculate a high gradation conversion value to be converted by adding the predetermined reference gradation value to the detected gradation value. Making; And Converting the gradations of pixels of the odd frame among the generated same frames to the calculated low gradation conversion value and converting the gradations of pixels of the even frame to the calculated high gradation conversion value. Method of driving a liquid crystal display device comprising a. The method of claim 13, The selection signal generating step, Reading the stored previous frame when the current frame is input; Calculating gray level differences between the read previous frame and corresponding pixels of the current frame; Adding all the calculated gray level differences to obtain an added value; Comparing the added value with a predetermined reference gray value to determine whether the added value is smaller than the predetermined reference gray value; Determining that the current frame is a still image frame and generating the first selection signal if the addition value is smaller than the predetermined reference gray value as a result of the determination; And Determining that the current frame is a moving picture frame when the addition value is greater than the predetermined reference gray value, and generating the second selection signal. Method of driving a liquid crystal display device comprising a.

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