KR100878273B1 - LCD and its driving method - Google Patents

Abstract

The present invention relates to a liquid crystal display and a driving method thereof.

The liquid crystal display according to the present invention includes a plurality of gate lines, a plurality of data lines insulated from and intersecting the plurality of gate lines, and are formed in an area where the plurality of data lines and the gate lines intersect, respectively. A liquid crystal panel including a plurality of pixels having a switching element connected to a line; A gate driver supplying a gate voltage to the gate line; At least one data driver for supplying a data voltage corresponding to the image data applied to the data line; And a timing controller for comparing the image data of the n-th frame applied from the outside with the stored image data of the n-th frame, and selectively providing the n-th image data to the data driver according to a comparison result.

According to the present invention, since image data transmission between the timing controller and the data driver can be minimized, power consumption at the time of switching the image data can be reduced.

LCD, image data transmission, power consumption reduction

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND A DRIVING METHOD THEREOF}

1 is an overall structural diagram of a liquid crystal display according to an exemplary embodiment of the present invention.

2 is a structural diagram of a timing controller according to an embodiment of the present invention.

3 is a flowchart illustrating an operation of a timing controller according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (LCD) and a driving method thereof, and more particularly, to an apparatus and a method for driving a liquid crystal display.

Recently, display devices are also required to be lighter and thinner in accordance with the light weight and thickness of personal computers and televisions, and according to such demands, flat displays such as liquid crystal displays (LCDs) instead of cathode ray tubes (CRTs) are required. Panel-type displays are being developed.

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 controlling the amount of light transmitted through the substrate by adjusting the intensity of the electric field. Such LCDs are typical of portable flat panel displays, and among them, TFT-LCD using a thin film transistor (TFT) as a switching element is mainly used.

In general, an LCD includes a plurality of gate lines for transmitting a scan signal and data lines intersecting the gate lines, and data lines for transmitting image data. The LCD is formed in an area surrounded by the gate lines and the data lines, respectively. It includes a plurality of pixels in the form of a matrix connected through a switching element.

As a method of applying image data to each pixel in such an LCD, first, a gate-on signal, which is a scanning signal, is sequentially applied to gate lines to sequentially turn on a switching element connected to the gate line, and simultaneously to the gate line. Image data (more specifically, a gray voltage) to be applied to the corresponding pixel row is supplied to each data line. Then, the image data supplied to the data line is applied to each pixel through the turned-on switching element. At this time, the gate-on signal is sequentially applied to all the gate lines during one frame period to apply the image data to all the pixel rows, thereby eventually displaying the image of one frame.

Here, the image data is transmitted from the timing controller which controls the overall operation of the liquid crystal display to the data driver IC, which applies the transmitted image data to the pixel as described above.

In such a liquid crystal display, since the timing controller converts image data into 8-bit binary codes and transmits the data to the driver IC through the data bus, a code transition between the current data and the next data is frequently generated to generate power. Consumption increases.

That is, since power P = cV ² f (where c denotes the capacitance of the PCB, V denotes the swing width of the voltage, and f denotes how frequently the image data transitions) is consumed. As data transition occurs frequently during data transmission, power consumption increases.

In particular, in the liquid crystal display device used in the portable information device, reducing the power consumption is an important problem above all.

Therefore, the technical problem to be achieved by the present invention is to reduce the power consumption generated when transmitting image data in the liquid crystal display device.

 In accordance with an aspect of the present invention, a liquid crystal display device includes a plurality of gate lines, a plurality of data lines insulated from and intersecting the plurality of gate lines, and an area in which the plurality of data lines and the gate lines cross each other. A liquid crystal panel formed on and including a plurality of pixels each having a switching element connected to the gate line and the data line; A gate driver supplying a gate voltage to the gate line; At least one data driver for supplying a data voltage corresponding to the image data applied to the data line; And a timing controller for comparing the image data of the n-th frame applied from the outside with the image data of the n-th frame stored therein and selectively providing the n-th image data to the data driver according to a comparison result. .

The timing controller may include: a first memory in which image data of the n−1 th frame is stored; A second memory in which image data of the nth frame is stored; A comparison unit for comparing the image data of the n-th frame stored in the first memory with the image data of the n-th frame stored in the second memory and selectively outputting the n-th image data according to a comparison result; And a controller configured to provide image data selectively output from the comparison unit to the data driver.

In this case, when the image data of the n-th frame stored in the first memory and the image data of the n-th frame stored in the second memory are the same, the comparator stops outputting the image data of the n-th frame. The controller controls the image data of the n-th frame when the image data of the n-1th frame stored in the first memory and the image data of the nth frame stored in the second memory are not the same. To provide an image display.

The timing controller may further include a counter for counting the number of times the image data of the nth frame that is identical to the image data of the n−1th frame is continuously input. In this case, when the image data of the n-th frame and the image data of the n-th frame are the same, the comparator provides the n-th image data to the controller when the value counted by the counter is equal to or larger than a set value. Image display is performed.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, wherein the plurality of gate lines, a plurality of data lines insulated from and cross the plurality of gate lines, and are formed in a region where the plurality of data lines and the gate lines cross each other. A driving method of a liquid crystal display device comprising a plurality of pixels each having a switching element connected to the gate line and the data line, the method comprising: a) supplying a data voltage according to image data applied to the data line; And b) supplying a gate voltage to the gate line so that the data voltage is applied to the pixel, wherein step a) is performed by the image data of the previously provided n-1th frame and the currently provided nth frame. Comparing image data; If the image data of the n-th frame and the image data of the n-th frame are the same, not providing a data voltage corresponding to the n-th image data to the data line; And when the image data of the n-th frame and the image data of the n-th frame are not the same, providing a data voltage corresponding to the n-th image data to the data line.

Here, the step a) includes the steps of counting the number of consecutive inputs of the image data of the n-th frame identical to the image data of the n-th frame; And providing a data voltage corresponding to the nth image data to the data line even when the image data of the n-th frame and the image data of the n-th frame are the same when the counted value is greater than or equal to a set value. It may further include.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram schematically illustrating a structure of a liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel 1, a gate driver 2, a data driver 3, a driving voltage generator 4, and a timing controller 5. ) And the gray voltage generator 6.

The liquid crystal panel 1 includes two substrates (eg, a TFT substrate and a color filter substrate), and a plurality of data lines and a plurality of gate lines cross each other on one substrate, and one gate line and one data line. Pixels are formed in each of these intersecting regions. Each pixel includes a TFT which is a switching element in which a gate electrode, a source electrode, and a drain electrode are respectively connected to a gate line, a data line, and a pixel electrode.

The timing controller 5 is an R (red), G (green), B (blue) data signal, a vertical synchronization signal (Vsync) that is a frame discrimination signal, and a row discrimination signal from a graphic controller (not shown) outside the LCD module. The digital synchronization signal Hsync and the main clock signal CLK are received to output a digital signal for driving the gate driver 2 and the data driver 3.

The timing signal output from the timing controller 5 to the gate driver 2 includes a vertical start signal Vstart for instructing the gate on voltage to be applied to the gate line, and the gate on voltage. A gate clock signal (CPV signal) for sequentially applying to each gate line and a gate on enable signal OE for enabling the output of the gate driver 2 are provided.

The timing signal output from the timing controller 5 to the data driver 3 includes digital data signals R (0: N) and G (0: N) from an external data source (e.g., a graphics controller). ), A horizontal start signal (Hstart) for instructing B (0: N)] to be input to the data driver 3, and a signal for instructing the panel to apply an analog data signal in the data driver (3) ( Hereinafter referred to as " LOAD signal " and a horizontal clock signal HCLK for data shift in the data driver 3, and the like.

In particular, in the embodiment of the present invention, the timing controller 5 provides the digital data signals [R (0: N), G (0: N), B (0: N) provided from an external data source to reduce power consumption. ) Is optionally provided to the data driver 3.

The data driver 3 is also called a source driver and serves to lower the voltage value transmitted to each pixel in the liquid crystal panel 1 by one line. More specifically, the data driver 3 stores the digital data from the timing controller 5 in the shift register in the data driver 5 and selects a voltage corresponding to each data when the LOAD signal is received, into the liquid crystal panel 1. It serves to carry this voltage.

The gate driver 2 is also called a scan driver, and serves to open a way for data from the data driver 3 to be transferred to the pixel. Each pixel of the liquid crystal panel 1 is turned on or off by a TFT serving as a switch, and the TFT is turned on or off by applying a constant voltage (Von, Voff) to a gate. The gate driver 2 receives the CPV signal and the 0E signal output from the timing controller 5, and applies gate-on voltages G1, G2,..., Gn to the gate line in synchronization with the two signals CPV, OE. Apply sequentially.

The gray voltage generator 6 generates a gray voltage equally divided according to the number of bits of RGB data provided from a graphic controller (not shown) and provides it to the data driver 3. The data driver 3 is driven by a signal output from the timing controller 5 to apply the data voltages D1, D2,..., Dm to all data lines in synchronization with the driving of the gate driver 2. Assuming that the data voltages D1, D2, ..., Dm are not significantly affected by the delay of the data line, the data voltages D1, D2, ..., Dm are applicable during the period in synchronization with the high period of the gate-on voltages G1, G2, ..., Gn. The pixel is charged.

On the other hand, the Von voltage for turning on the gate of the TFT and the Voff voltage for turning off the gate are generated by the driving voltage generator 4. The driving voltage generator 4 generates not only the above-mentioned Von and Voff voltages but also a Vcom voltage which is a reference for the data voltage difference in the TFT, and the Vcom voltage is provided to the common electrode of each pixel.

In the liquid crystal display according to the embodiment of the present invention having such a structure, the n-th frame image data (hereinafter referred to as "n-th image data") provided from an external graphic controller (not shown) and previously provided When the image data of the n-1th frame (hereinafter referred to as "nth image data") is compared, and the two image data are the same, the timing controller does not transmit the image data to the data driver. For example, the liquid crystal display outputs image data at 1/60 sec so that a continuous natural screen can be recognized by the user's eyes, and when the same image data is continuously output, the image data is about 1-2 frames. You can't recognize it without printing. Therefore, in the embodiment of the present invention, when the same image data is continuously input using this, the image data output, that is, the image display is not performed.

On the other hand, when the two image data are not the same, the n-th image data currently input is provided to the data driver so as to display an image corresponding to the n-th image data.

In this manner, by selectively providing the image data to the data driver in accordance with whether the n-th image data and the n-th image data are the same, power consumption due to image data transmission can be reduced.

Fig. 2 shows the structure of the timing control section for such image data transmission briefly.

As shown in FIG. 2, the timing controller according to an exemplary embodiment of the present invention stores a first memory 51 in which n−1th image data previously applied from the outside is stored, and nth image data currently input. The second memory 52 to be compared, and the comparator 53 for comparing the n-th image data with the n-th image data and selectively outputting the n-th image data according to the comparison result, and the same as the n-th image data. A counter 54 for counting the number of times n-th image data is continuously input, and a controller 55 for providing the n-th image data selectively output from the comparator 53 to the data driver 3.

Here, the comparator 53 does not output the n-th image data input to the control unit 55 when the n-th image data and the n-th image data are the same, and the n-th image data and the n-th image data. If is not the same, the input n-th image data is output to the controller 55 so as to be provided to the data driver 3.

Since the default value of the comparator 53 is set such that the nth image data and the n-1th image data are not the same, the image data input initially is provided to the controller 55 as it is, and the data driver 3 Is provided. In addition, the count value of the counter 54 is set to "0" by default.

On the other hand, the controller 55 processes the n-th image data selectively provided from the comparator 53 and provides it to the data driver 3. The controller 55 does not perform only the above-described functions, but processes and generates various control signals for driving the general liquid crystal display, and processes the input image data. The description is omitted here because it is a technology.

Based on this structure, the operation of the liquid crystal display according to the exemplary embodiment of the present invention will be described.

 When image data, a vertical synchronizing signal Vsync as a frame discrimination signal, a horizontal synchronizing signal Hsync as a row discrimination signal, and a main clock signal CLK are provided from a graphic controller (not shown) external to the LCD module, The comparison unit 53 of the timing controller 5 first determines whether to transmit the input image data.

3 sequentially illustrates the operation of the timing controller according to the embodiment of the present invention.                     

As shown in FIG. 3, image data of the current frame, that is, n-th image data, is input from the graphic controller and stored in the second memory 52 (S100), and the comparator 53 receives the second memory 52. ) And the n-th image data, i.e., the n-th image data, of the previous frame stored in the first memory 51 (S110 to S120).

When the nth image data and the n-1th image data are the same, the comparator 53 determines that the image data does not need to be transmitted in order to reduce power consumption, and provides the result to the counter 54.

As a result, the counter 54 increases the count value, that is, the value for measuring the number of times image data identical to the image data of the frame stored in the first memory 51 is +1 (S130 to S140).

Next, the comparator 53 compares the count value of the counter 54 with the set value and determines whether the number of times that the same data is continuously input exceeds the set value. If the count value is smaller than the set value, the n th image data currently input is not output. Therefore, since the controller 55 does not output the image data from the comparator 53, the controller 55 cannot provide the image data for image display even with the data driver 3, and as a result, image display is not performed (S150 to S160). ).

On the other hand, when the count value of the counter 54 is greater than or equal to the set value, the comparator 53 recognizes that the user is not currently displaying the image because the same data is continuously input and the number of times that the image is not performed is large. In this case, the n-th image data is output to the control unit 55 for the image display even though the n-th image data and the n-1th image data are the same.

Specifically, the comparator 53 resets the count value (S170), and then stores the n th image data currently input in the first memory 51 (S180), and stores the n th image data in the controller 55. Output to (S190).

Therefore, the controller 55 provides the image data provided from the comparator 53 to the data driver 3, and various timing signals necessary for driving the liquid crystal, for example, a gate clock signal CPV and a horizontal sync pulse STV. ), A horizontal start signal (Hstart), a load signal, and the like are generated and output to the data driver 3 and the gate driver 2 so that image display is performed.

Accordingly, the data driver 3 converts the n-th image data into corresponding data voltages in synchronization with the horizontal start signal Hstart, and then applies them to the source electrodes of the TFTs of the liquid crystal panel 1 in accordance with the applied load signal. The gate driver 2 applies a gate-on voltage to the gate electrode of the TFT in synchronization with the gate clock signal output from the timing controller 5, and as a result, the data voltage applied to the source electrode is charged in the pixel electrode.

Therefore, the alignment state of the liquid crystal is changed according to the potential difference between the data voltage supplied to the common electrode and the pixel electrode, and accordingly, the amount of light transmitted is changed to display a desired image.

On the other hand, in step S130, when the n-th image data and the n-th image data are not the same, the comparison unit 53 stores the n-th image data currently input in the first memory 51. and outputting the nth image data to the control unit 55, whereby the control unit 55 outputs various control signals and the nth image data to the data driver 3 as described above, corresponding to the nth image data. Image display is performed (S180 to S190).

As described above, when the data driving unit has a plurality of methods for selectively providing the image data to the data driving unit 3 by the timing controller 5 according to whether the n-th image data and the n-1 th image data match. The same can be applied to.

The invention is susceptible to various modifications and implementations without departing from the scope of the following claims. For example, even in a liquid crystal display of a chip on glass (COG) type in which a data driver is directly mounted on a thin film transistor substrate and the data driver is connected to a printed circuit board through a transmission film, the timing according to the above-described embodiment Selective image data transmission between the controller and the data driver can be made. In addition, the image data transmission according to the above embodiment may also be applied to a structure in which the data driver is mounted on a flexible printed circuit (FPC) provided between the printed circuit board and the thin film transistor substrate.

In addition, the image data transmission according to the above-described embodiments may be applied to a liquid crystal display device which transmits image data by low voltage differential signaling (LVDS) or reduced swing differential signaling (RSDS).                     

Since this can be easily carried out by those skilled in the art based on the above embodiments, detailed description thereof will be omitted.

As described above, according to the exemplary embodiment of the present invention, since image data transmission between the timing controller and the data driver can be minimized, power consumption during image data switching can be reduced.

Claims (6)

A plurality of gate lines, a plurality of data lines insulated from and intersecting the plurality of gate lines, and a switching element formed in an area where the plurality of data lines and the gate lines intersect, and connected to the gate lines and the data lines, respectively. A liquid crystal panel including a plurality of pixels; A gate driver supplying a gate voltage to the gate line; At least one data driver for supplying a data voltage corresponding to the image data applied to the data line; And And a timing controller for comparing the image data of the n-th frame applied from the outside with the stored image data of the n-1-th frame, and selectively providing the n-th image data to the data driver according to a comparison result. The timing controller A first memory in which image data of the n−1 th frame is stored; A second memory in which image data of the nth frame is stored; A comparison unit for comparing the image data of the n-th frame stored in the first memory with the image data of the n-th frame stored in the second memory and selectively outputting the n-th image data according to a comparison result; A control unit for providing image data selectively output from the comparison unit to the data driver; And A counter for counting the number of times image data of the n-th frame that is identical to the image data of the n-th frame is continuously input; If the image data of the n-th frame and the image data of the n-th frame are the same, the comparison unit provides the n-th image data to the controller to display an image when the value counted by the counter is equal to or larger than a set value. Liquid crystal display device to be made. delete The method of claim 1, The timing controller, The comparison unit, even if the image data of the n-th frame stored in the first memory and the image data of the n-th frame stored in the second memory is the same, if the counted value is less than the set value, the image of the n-th frame The output of the data is stopped so that image display is not performed, and when the image data of the n-1th frame stored in the first memory and the image data of the nth frame stored in the second memory are not the same, the nth A liquid crystal display device for providing an image display by providing the image data of the frame to the control unit. delete A plurality of gate lines, a plurality of data lines insulated from and intersecting the plurality of gate lines, and a switching element formed in an area where the plurality of data lines and the gate lines intersect, and connected to the gate lines and the data lines, respectively. In the driving method of a liquid crystal display device comprising a plurality of pixels, a) supplying a data voltage according to the image data applied to the data line; And b) supplying a gate voltage to the gate line to apply the data voltage to the pixel; Including; Step a) Comparing the image data of the n-th frame provided previously with the image data of the n-th frame currently provided; As a result of the comparison, if the image data of the n-th frame and the image data of the n-th frame are the same, the number of times the image data of the n-th frame identical to the image data of the n-th frame is continuously input is counted. Doing; Not providing a data voltage corresponding to the nth image data to the data line when the counted value is less than a set value; And If the counted value is equal to or greater than a set value, providing a data voltage corresponding to the n-th image data to the data line even when the image data of the n-th frame and the image data of the n-th frame are the same. Method of driving a liquid crystal display comprising a. The method of claim 5, Step a) If the image data of the n-th frame and the image data of the n-th frame are not the same, providing a data voltage corresponding to the n-th image data to the data line. The driving method of the liquid crystal display device further comprising.

Images