KR20030018758A - liquid crystal device and driving method thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a driving method thereof are provided, which minimizes transition of image data transmitted to a data driving IC from a timing controller. CONSTITUTION: A liquid crystal display panel(1) includes a number of gate lines and data lines, and a common electrode receiving the common voltage with a switching device which is formed on a cross region of the gate line and the data line and is connected to each gate line and data line. A scan driving part(2) supplies the gate voltage to the gate line, and a data driving part(3) supplies gray voltage corresponding to the applied image data to the data line. And a timing control part(5) generates a digital signal to drive the data driving part and the scan driving part and transmits image data to the data driving part. And the timing control part converts image data into gray codes selectively and then transmits them to the data driving part.

Description

Liquid crystal display and driving method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (hereinafter referred to as "LCD") and a driving method thereof, and more particularly, to transmit digital data to a driving IC (integrated chip) that supplies a data voltage to a liquid crystal panel. It's about things.

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 that transmit scan signals and data lines that are formed to intersect the gate lines and transmit image data, and are formed in areas 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 data line and a switching element.

In the LCD, image data is applied to each pixel. First, a gate-on signal, which is a scan signal, is sequentially applied to gate lines to sequentially turn on a switching element connected to the gate line, and at the same time, the gate line. The image data (more specifically, the gray voltage) to be applied to the pixel row corresponding to 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.

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

On the other hand, as the resolution increases, the frequency of the image data increases and the increased frequency cannot be handled by a printed circuit board (PCB). Therefore, the number of data buses that transfer image data from the timing controller to the data driving IC is increased. Increase. Increasing the number of data buses increases the power consumption as well as Electro Magnetic Interference (EMI). Therefore, a method of transferring image data to a driving IC in a timing controller has become important.

Since the timing controller converts image data into 8-bit binary codes and transmits them to the driving IC via the data bus, code transitions of the current data and the next data are frequently generated. For example, when data of "0000000" corresponding to "00" is transmitted and then "11111111" corresponding to "FF" is transmitted, data transition occurs eight times. The power consumed during this data transfer is P = cV ² f (where c represents the capacitance of the PCB, V represents the swing width of the voltage, and f represents how frequently the image data transitions). When data is transmitted by code, data transition occurs frequently and power consumption is increased.

Therefore, an object of the present invention is to minimize the transition of image data transmitted from a timing controller to a data driving IC in a liquid crystal display device.

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

2 is an exemplary view for explaining a method of transmitting image data according to an embodiment of the present invention.

FIG. 3 is a diagram illustrating binary code changes and gray code changes of R, G, and B image data transmitted according to the transmission method illustrated in FIG. 2, and a toggle amount when each data is changed.

4 is a flowchart illustrating a data transmission method in a liquid crystal display according to an exemplary embodiment of the present invention.

5A to 5D are exemplary views showing a toggle amount distribution of test image data to be processed according to a data transmission method according to an embodiment of the present invention.

6 is a graph showing a result of processing the image data shown in FIGS. 5A to 5D according to a data transmission method according to an embodiment of the present invention.

According to an aspect of the present invention, a liquid crystal display device includes a plurality of gate lines and data lines, and is formed in an area where the gate lines and data lines cross each other, and are connected to the gate lines and data lines, respectively. A liquid crystal panel including a plurality of pixels having a switching element and a common electrode to which a common voltage is applied; A scan driver supplying a gate voltage to the gate line; A data driver which supplies a corresponding gray voltage to the data line according to the image data applied; And a timing controller configured to generate a digital signal for driving the data driver and the scan driver, and to transmit image data to the data driver, wherein the timing controller selectively converts image data into a gray code and transmits the data to the data driver. do.

In particular, the timing controller converts the image data into one of a binary code, a gray code, an inverted binary code, and an inverted gray code, and transmits the data to the data driver.

Specifically, the image data to be transmitted is converted into a binary code, a gray code, an inverted binary code, and an inverted gray code, and then a minimum transition occurs by comparing previously transmitted image data with image data converted to each code. The code to be selected is selected, the image data is converted into the selected code, and transmitted to the data driver.

At this time, the timing controller transmits a code signal indicating to which code the image data is converted, and a polarity signal indicating whether the polarity of the image data is inverted together with the image data to the data driver, so that the data driver The code and polarity status of the transmitted image data can be grasped.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display, including: a liquid crystal panel including a plurality of gate lines and data lines, and a plurality of pixels formed in an area where the gate lines and the data lines cross each other; A scan driver supplying a gate voltage to the gate line; A driving method of a liquid crystal display device including a data driver for supplying a corresponding gray voltage to the data line according to an applied data signal, the method comprising: selectively converting the image data into a gray code and transmitting the converted data to the data driver; Supplying a gate driving signal to a gate line for driving the switching device; And supplying a gray voltage corresponding to pixel data to the data line while driving signals are respectively applied to the gate line.

The image data transmitting step may include converting image data to be transmitted into a binary code, gray code, inverted binary code, and inverted gray code; Comparing the previously transmitted image data with the image data converted into respective codes, and selecting a code having a minimum transition; And converting the image data to be transmitted into a selected code and transmitting the converted image data to a data driver.

At this time, a code signal indicating to which code the image data is converted and a polarity signal indicating whether the polarity of the image data is inverted are transmitted to a data driver to determine the code state of the image data transmitted by the data driver. To help.

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

1 illustrates 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 an LCD panel 1, a scan driver 2, a data driver 3, a Von Voff Vcom generator 4, and a timing controller. 5 and a gray voltage generator 6, the signals from the data driver 3 and the gate driver 2 are applied to the LCD panel 1;

The data driver 3 is also called a source driver and serves to lower the voltage value transmitted to each pixel in the LCD panel 1 by one line. More specifically, the data driver 3 stores image data from the timing controller 5, which will be described later, in a shift register in the data driver, and instructs the LCD panel 1 to lower the data (LOAD signal). When the voltage corresponding to each data is selected, the voltage is transferred to the LCD panel 1.

The scan driver 2 is also referred to as a gate driver, and serves to open a road so that data from the data driver 3 can be transferred to the pixel. Each pixel of the LCD panel 1 is turned on or off by a TFT serving as a switch, which is turned on and off by applying a constant voltage (Von, Voff) to the gate of the TFT.

In this way, the Von voltage for turning on the gate and the Voff voltage for turning off the gate are generated by the Von Voff Vcom generating portion 4. Von Voff Vcom generating section 4 generates not only the above-mentioned Von and Voff voltages, but also Vcom voltages, which are references to data voltage differences in TFTs. The gray voltage generator 6 generates a gray voltage entering the data driver 3.

The timing controller 5 generates a digital signal for driving the data driver 3 and the scan driver 2. Specifically, the timing controller 5 generates a signal that enters the drivers 2 and 3, adjusts timing of data, and adjusts clock. And the like, and transfer image data provided from an image signal source to the data driver 3.

The timing controller 5 according to the embodiment of the present invention transmits the image data to the data driver 3 in order to minimize the transition of the image data as much as possible. : Unlike binary code, it transmits by converting two adjacent numbers in consecutive binary numbers so that only one digit is different. In addition, in order to further minimize the transition, the image data is transmitted in an inverted binary code or inverted gray code.

Specifically, the image data to be transmitted is converted into a binary code, a gray code, an inverted binary code, and an inverted gray code, respectively, and then a code having a minimum transition is selected by comparing each code with previously transmitted image data. To transfer the image data to the selected code.

Therefore, in addition to the image data, in addition to the image data, a code signal indicating whether the image data is a binary code or a gray code and a polarity signal indicating whether the image data is an inverted binary code or an inverted gray code are transmitted together. The data driver which receives the image data makes it possible to know the conversion state of the image data.

In the present embodiment, when the polarity signal is "0", it indicates that the image data is not inverted, and when the polarity signal is "1", it indicates that the image data is inverted, and when the code signal is "0". It indicates that the image data is a binary code, and when the code signal is "1", it indicates that the image data is a gray code, but is not limited thereto.

2 illustrates an example for explaining a method of transmitting image data according to an embodiment of the present invention, and FIG. 3 illustrates an example of R, G, and B image data transmitted in FIG. 2 transmitted according to an embodiment of the present invention. Binary code changes and gray code changes and the amount of toggle when each data changes are illustrated.

As shown in FIG. 2, for example, R, G, and B data (previous image data) transmitted to the current data driver are "10000100", "100000011", "10000001", respectively, and R, G, Let B data be "01110101", "01110110", and "01111010", respectively.

When the next R, G, and B data to be transmitted is transmitted as a binary code, the generated transition, that is, the toggle amount is "5" for "R" data, "6" for "G" data, and "6" for "B" data. 7 ", and the total toggle amount is" 5 + 6 + 7 = 18 ". In this case, the code signal G and the polarity signal I of the previous image data are also "00", respectively, and the code signal G and the polarity signal I of the R, G, and B data to be transmitted are also "00". Therefore, the toggle amount by the code signal and the control signal is "0".

On the other hand, when R, G, and B data to be transmitted are converted into inverted binary codes, they are "10001010", "10001001", and "10000101", respectively. In this way, when the R, G, and B data to be transmitted are inverted binary coded and transmitted, a toggle of "3" for "R" data, "2" for "G" data, and "1" for "B" data is performed. A quantity is generated, in which the code signal (G) and the polarity signal (I) are changed from "00" to "01", so that the total amount of the toggle amount "1" by the code signal and the polarity signal is "3+". 2 + 1 + 1 = 7 ".

In addition, when R, G, and B data to be transmitted are converted to gray codes instead of binary codes, they become "01001111", "01001101", and "01000111", respectively. In this way, when the next R, G, and B data to be transmitted are gray coded and transmitted, a toggle amount of "5" for "R" data, "5" for "G" data, and "4" for "B" data. In this case, since the code signal (G) and the polarity signal (I) are changed from "00" to "10", the toggle amount "1" by the code signal and the polarity signal is added, and the total toggle amount is "5 + 5". + 6 + 1 = 15 ".

Further, when the next transmitted R, G, and B data are converted into inverted gray codes, they are "10110000", "10110010", and "10111000", respectively. In this way, when the next R, G, and B data to be transmitted are inverted gray coded and transmitted, a toggle of "3" for "R" data, "3" for "G" data, and "4" for "B" data is performed. A quantity is generated, and in this case, the code signal G and the polarity signal I are changed from "00" to "11", so that the total amount of the toggle amount "2" by the code signal and the polarity signal is "3+". 3 + 4 + 1 = 12 ".

Thus, after transmitting the R, G, and B data of "10000100", "100000011", and "10000001", the R, G, and B data of "01110101", "01110110", and "01111010" to be transmitted next are transferred. Determine the amount of toggle that can be generated by converting to binary code, inverted binary code, gray code, and inverted gray code respectively, and then select the code with the least toggle amount among each code to select "01110101", "01110110" , R, G, B data of " 01111010 " are converted into the selected code and transmitted to the data driver.

Here, as described above, since the toggle amount is smallest when the next R, G, and B data to be transmitted is transmitted with an inverted binary code, the R, G, B of "01110101", "01110110", and "01111010" are the smallest. The data is converted into an inverted binary code of "10001010", "10001001", and "10000101", respectively, and transmitted.

Meanwhile, in the case of the third and fourth R, G, and B data shown in FIG. 2, the fourth R, G, and B data may be divided into binary code, inverted binary code, gray code, and inverted gray in the same manner as described above. When the code is converted to the inverted gray code, the amount of toggle is minimized. After the third R, G, and B data transmission, the fourth R, G, and B data is inverted gray coded and transmitted.

The state in which the image data, the code signal, and the polarity signal thus illustrated are transmitted is specifically illustrated in FIG. 3.

Next, a method of driving a liquid crystal display device having such a structure will be described.

The timing controller 5 generates various timing signals necessary for driving the liquid crystal, for example, a gate driving clock CPV and a horizontal synchronizing pulse STV, and generates an image signal Vs to be applied to the liquid crystal from a signal source (not shown). The image data is generated and provided to the data driver 3.

4 is a flowchart illustrating a method of transmitting data in a liquid crystal display according to an exemplary embodiment of the present invention.

The timing control section 5 compares the previous image data with the previous image data before converting the image data into a code issued by the transition with the minimum.

That is, as described above, the timing controller 5 converts the image data to be transmitted into binary code, inverted binary code, gray code, and inverted gray code, respectively (S100 to S140), and Toggle amount generated by comparing previously transmitted image data is calculated.

Next, the timing controller 5 determines which code has the minimum transition based on the amount of toggles calculated for each conversion code (S150 to S160), and transmits the image data to the data driver 3 with the code having the minimum transition. It transmits (S170).

At this time, the timing controller 5 transmits a polarity signal and a code signal indicating which polarity of the current image data has been converted to which code together with the image data, and transmits the image data transmitted by the data driver 3. Restore it and use it.

For example, when the image driver receives image data from the timing controller 5 via the data bus and receives a control signal "01" through the signal bus, the data driver 3 processes the image data into gray codes that are not inverted. The image data is reconstructed by a binary code after determining that it is in a state, and then, in conjunction with the gate driver 4, a gray scale voltage corresponding to the image data is provided to the liquid crystal panel 1.

In the exemplary embodiment of the present invention, when the various screens having the SXGA (super exyended graphics array) resolution are transmitted by the above-described method, it is tested how much the transition can be reduced, and the test results are shown in FIGS. 5 and 6. have.

5A to 5D show a toggle amount distribution of a test screen, and FIG. 6 illustrates a transition between a test screen, that is, a case in which image data is processed by a transmission method according to an exemplary embodiment of the present invention and a conventional transmission method. It is a graph comparing the decrease.

5A and 5B show a toggle amount distribution generated in image data D1 and D2 such as TV and multimedia, and FIGS. 5C and 5D show a toggle amount distribution generated in monitor image data. In particular, FIG. 5C is a toggle amount distribution generated from document image data D3 such as Hunmin Jeongeum and Korean. 5D is a toggle amount distribution generated in the window screen image data D4.

5A to 5D, it can be seen that the toggle is uniformly generated in the TV or the multimedia image data D1 and D2, while the transition is rapidly changed in the monitor image data D3 and D4. . Image data having this feature was processed according to the transmission method according to the embodiment of the present invention to obtain a result as shown in FIG.

As shown in Fig. 6, when each test image data is transmitted only by a binary code as in the conventional method (Bypass), and when the test data is transmitted by a DTM (data transition minimize) method (DTM), each test image data is only in gray code. Compared to the transmission (Gray), when the test image data is selectively processed according to an embodiment of the present invention by binary code or inverted binary code or gray code or inverted gray code and transmitted (Binary0Gray-DTM), a transition is performed. It can be seen that the decrease significantly. In particular, it can be seen that the amount of toggle can be reduced to less than half in image data D1 and D2 such as multimedia, and up to 10% or less in image data D3 and D4 such as a monitor.

On the other hand, the image data method according to an embodiment of the present invention can be applied to low voltage differential signaling (LVDS) and reduced swing differential signaling (RSDS).

As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, A various other deformation | transformation and a change are possible.

According to the present invention described above, it is possible to minimize the transition generated during image data transmission, and as a result, it is possible to reduce power consumption and to minimize the influence of EMI.

Claims (7)

A plurality of pixels having a plurality of gate lines and data lines, a switching element connected to the gate line and the data line, and having a common electrode to which a common voltage is applied; A liquid crystal panel; A scan driver supplying a gate voltage to the gate line; A data driver which supplies a corresponding gray voltage to the data line according to the image data applied; And A timing controller which generates a digital signal for driving the data driver and the scan driver, and transmits image data to the data driver. Including; And the timing controller selectively converts image data into a gray code and transmits the image data to the data driver. The method of claim 1, The timing controller And converting image data into one of a binary code, a gray code, an inverted binary code, and an inverted gray code, and transmitting the image data to a data driver. The method of claim 2, The timing controller After converting the image data to be transmitted to binary code, gray code, inverted binary code, and inverted gray code, compare the previously transmitted image data with the image data converted to each code to obtain a code having the least transition. And converting the corresponding image data into a selected code and transmitting the same to the data driver. The method of claim 2, The timing controller transmits a code signal indicating to which code the image data has been converted, and a polarity signal indicating whether the polarity of the image data is inverted together with the image data to the data driver so that the image driver transmits the image. A liquid crystal display device, which makes it possible to grasp the code and the polarity state of data. A liquid crystal panel including a plurality of gate lines and data lines, and a plurality of pixels formed in an area where the gate lines and the data lines cross each other; A scan driver supplying a gate voltage to the gate line; In the driving method of the liquid crystal display device including a data driver for supplying a corresponding gray voltage to the data line in accordance with the applied data signal, Selectively converting the image data into a gray code and transmitting the image data to the data driver; Supplying a gate driving signal to a gate line for driving the switching device; And Supplying a gray voltage corresponding to pixel data to the data line while driving signals are respectively applied to the gate line Driving method characterized in that. The method of claim 5, The image data transfer step, Converting the image data to be transmitted into a binary code, gray code, inverted binary code, inverted gray code; Comparing the previously transmitted image data with the image data converted into respective codes, and selecting a code having a minimum transition; And Converting the image data to be transmitted into a selected code and transmitting the image data to a data driver; The driving method further comprises. The method of claim 5, The step of transmitting the image data, A code signal indicating to which code the image data is converted, and a polarity signal indicating whether the polarity of the image data is inverted to a data driver, so that the data driver can grasp the code state of the image data transmitted. A drive method, characterized in that.