Patent Publication Number: US-7586475-B2

Title: Circuit for driving liquid crystal display device

Description:
This application claims the benefit of Korean Patent Application No. P2004-62404, filed on Aug. 9, 2004, which is hereby incorporated by reference as if fully set forth herein. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a liquid crystal display device, and more particularly, to a circuit for driving a liquid crystal display device. 
     2. Discussion of the Related Art 
     With the progress of information-dependent society, the demand for various display devices has increased. To meet such a demand, efforts have recently been made to research and develop flat panel display devices such as liquid crystal displays (LCDs), plasma display panels (PDPs), electro-luminescent displays (ELDs), vacuum fluorescent displays (VFDs), and the like. Some types of such flat panel display devices are being practically applied to various appliances for display purposes. 
     In particular, LCDs have been used as a substitute for cathode ray tubes (CRTs) in association with mobile image display devices owing to their characteristics and advantages of superior picture quality, lightness, thinness, and low power consumption. Thus, LCDs are currently most widely used. Various applications of LCDs are being developed in association with not only mobile image display devices such as monitors of notebook computers, but also monitors of TVs to receive and display broadcast signals, and monitors of laptop computers. 
     Therefore, the successful application of LCDs to diverse image display devices depends on the ability of LCDs to realize desired high picture quality including high resolution, high brightness, large display area, and the like, while maintaining desired characteristics of lightness, thinness, and low power consumption. 
     Such an LCD mainly includes a liquid crystal panel for displaying an image signal, and a driving circuit for applying a drive signal to the liquid crystal panel. 
     Although not shown in the drawings, the liquid crystal panel is comprised of two transparent substrates (glass substrates) bonded to each other so as to have a certain space therebetween, and a liquid crystal layer formed between the two transparent substrates. 
     In one of the two transparent substrates is formed a plurality of gate lines arranged at certain regular intervals, a plurality of data lines arranged perpendicularly to the gate lines for defining pixel areas, a plurality of pixel electrodes formed respectively in the pixel areas, and a plurality of thin film transistors formed respectively at intersections of the gate lines and the data lines and each serving to transfer a data signal on an associated one of the data lines to an associated one of the pixel electrodes in response to a gate signal on an associated one of the gate lines. 
     As a result, whenever a turn-on signal is sequentially applied to the gate lines, a data signal is applied to a pixel electrode of the corresponding gate line so as to display an image. 
     Here, the image displayed on the liquid crystal panel is composed of one frame when it is a still image, and a plurality of frames when it is a moving image in which a plurality of sequential still images are successively expressed. 
     In the case where the displayed image is a moving image, the liquid crystal varies successively with the magnitudes of data signals corresponding respectively to frames of the moving image. 
     That is, in order to express one moving image with five frames on the liquid crystal panel, the liquid crystal varies successively with the magnitudes of data signals corresponding respectively to the five frames because the magnitudes of the data signals are different. 
     The magnitude of the data signal of each frame is expressed on the liquid crystal layer as the level of a gray-scale voltage so as to vary the orientation of liquid crystal molecules of the liquid crystal layer. Because the liquid crystal molecules have dielectric anisotropy, permittivity thereof varies if the longer-axis direction thereof varies. Subsequently, the level of a gray scale voltage to the liquid crystal layer varies with the permittivity of the liquid crystal molecules of the liquid crystal layer, resulting in a significant reduction in response speed of the liquid crystal molecules. 
     Namely, in the case where the gray scale voltage to the liquid crystal is to be changed from a low level to high level (or vice versa), it can reach the desired level, not at once, but after the lapse of several frames from a current frame, because the gray scale voltage of a data signal of the current frame is influenced by the gray scale voltage of a data signal of a previous frame. 
     For example, in order to express one moving image composed of two successive frames, the liquid crystal must be changed to the level of a gray scale voltage corresponding to an image of the second frame at once after being maintained in a state changed to the level of a gray scale voltage corresponding to an image of the first frame. However, provided that the response speed of the liquid crystal molecules is reduced due to factors as mentioned above, the liquid crystal will be unable to express the level of the gray scale voltage corresponding to the image of the second frame within a period of one frame. 
     This phenomenon can be represented as the display of a vague latent image of the first frame of the previous period overlapping with the image of the second frame on the liquid crystal panel. 
     Accordingly, research has been conducted into a method for improving the response speed of the liquid crystal molecules by over-driving the magnitude of a gray scale voltage setting data signal to a value higher than the normal value. 
     A conventional liquid crystal display device with an over-driving circuit will hereinafter be described with reference to the annexed drawings. 
       FIG. 1  is a block diagram showing the configuration of a conventional liquid crystal display device with an over-driving circuit. 
     The conventional liquid crystal display device comprises, as shown in  FIG. 1 , a liquid crystal panel  11  having a plurality of gate lines G and a plurality of data lines D arranged perpendicularly to each other for defining pixel areas in the form of a matrix, and a driving circuit  12  for supplying a drive signal and a data signal to the liquid crystal panel  11 . 
     The driving circuit  12  includes an external storage unit  25  for storing a look-up table (LUT) for over-driving, and a direct current-direct current (DC-DC) converter  24  for receiving a voltage from a system through a connector  22 , stepping up or down the received voltage, outputting the resulting drive voltages Vcc and Vdd necessary to respective components, and outputting a gate low voltage signal V GL  and a gate high voltage signal V GH  in response to an enable signal from a timing controller  23 . The timing controller  23  is adapted to, upon power-on, read the LUT from the external storage unit (for example, an electrically erasable programmable read only memory (EEPROM))  25 , store the read LUT in an over-driving circuit (ODC)  31  provided therein, correct a video signal inputted from the system into a video signal Do for over-driving on the basis of the LUT, output the corrected video signal Do, and output the enable signal to the DC-DC converter  24 . The driving circuit further includes a gate driver  11   a  for generating a scan pulse in response to the gate high voltage signal V GH  and gate low voltage signal V GL , outputted from the DC-DC converter  24  in response to the enable signal from the timing controller  23 , and supplying the generated scan pulse sequentially to the gate lines G of the liquid crystal panel  11 , and a data driver  11   b  for receiving the corrected video signal Do outputted from the timing controller  23 , digital/analog-converting the received video signal into a corrected analog data signal and supplying the corrected data signal to each of the data lines D of the liquid crystal panel  11 . 
     The timing controller  23  further includes a power control generating logic block  32  for receiving the drive voltage and outputting the enable signal, and a protocol block  33  for providing an Inter IC bus (“I2C”) communication protocol when the timing controller  23  communicates with the external storage unit  25  in an I2C protocol manner to read a checksum of data of the look-up table stored in the external storage unit  25 . 
     Two active wires SCL(Clock) and SDA(Data) for the aforementioned communication are connected between the protocol block  33  and the external storage unit  25 . 
     An R, G, B video signal outputted from the system is inputted to the timing controller  23  through the connector  22  sequentially on a frame-by-frame basis. The ODC  31  compares a video signal of a current frame with a video signal of a previous frame on the basis of the look-up table and outputs a corrected video signal Do of a magnitude higher than that of the current frame video signal as a result of the comparison. 
     That is, in the look-up table, values corresponding to the video signal of the previous frame and the video signal of the current frame are arranged in an x-axis and a y-axis. Also, a value corresponding to the corrected video signal Do is defined at an intersection of the x-axis and y-axis. As a result, the timing controller  23  reads a value at a crossing point of the value of the inputted video signal of the previous frame and the value of the inputted video signal of the current frame from the look-up table and outputs the corrected video signal Do based on the read value. 
     Therefore, a pixel electrode which receives a corrected data signal, outputted from the data driver  11   b  on the basis of the corrected video signal Do, over-drives the liquid crystal with a higher gray scale voltage. 
     A more detailed description will hereinafter be given of the over-driving circuit  31  in the timing controller  23 . 
       FIG. 2  is a block diagram of the over-driving circuit in the conventional liquid crystal display device. 
     An R, G, B video signal outputted from the system is inputted to the timing controller (see  23  in  FIG. 1 ) through the connector (see  22  in  FIG. 1 ) sequentially on a frame-by-frame basis. 
     The over-driving circuit of the conventional liquid crystal display device includes, as shown in  FIG. 2 , an internal storage unit (for example, a static random access memory (SRAM))  31  for storing the look-up table (LUT) stored in the external storage unit  25 , first and second frame memories  33   a  and  33   b  for alternately storing the R, G, B video data sequentially inputted from the system on a frame-by-frame basis, and an FFD circuit  33   c  for receiving video data of a current frame inputted from the system and video data of a previous frame stored in the first or second frame memory  33   a  or  33   b , comparing the received video data of the two frames with each other and outputting a corrected video signal Do of the current frame video data according to the look-up table stored in the internal storage unit  31  as a result of the comparison. 
     The first and second frame memories  33   a  and  33   b  are adapted to alternately store data of one frame in a write mode and output the stored frame data in a read mode. That is, currently inputted R, G, B video data is stored in the first frame memory  33   a  and video data of a previous frame stored in the second frame memory  33   b  is read. Next, currently inputted R, G, B video data is stored in the second frame memory  33   b  and video data of a previous frame stored in the first frame memory  33   a  is read. This operation is repeated. 
     An over-driving operation of the conventional over-driving circuit with the above-stated configuration will hereinafter be described. 
     First, the manufacturer or user creates and stores the look-up table in the external storage unit  25 . That is, the look-up table is created by arranging values corresponding to a video signal of a previous frame and a video signal of a current frame in an x-axis and a y-axis, and inputting a value corresponding to a corrected video signal Do at an intersection of the x-axis and y-axis. 
     The look-up table is created in this manner and is then stored in the external storage unit  25 . 
     Under this condition, whenever power is turned on, the timing controller  23  reads the look-up table stored in the external storage unit  25  and stores it in the ODC  31 . 
     At the time that R, G, B data is inputted from the system, the timing controller  23  stores the inputted R, G, B data in the first frame memory  33   a  and reads data of a previous frame stored in the second frame memory  33   b . Next, the timing controller  23  stores currently inputted R, G, B data in the second frame memory  33   b  and reads data of a previous frame stored in the first frame memory  33   a.    
     Then, the FFD circuit  33   c  retrieves a value at a crossing point of the value of the video signal of the previous frame and the value of the video signal of the current frame from the look-up table and outputs a corrected video signal Do based on the retrieved value. Then, the data driver  11   b  applies the corrected video signal Do to each pixel electrode so as to over-drive the liquid crystal with a higher gray scale voltage. 
     On the other hand, a backlight unit is placed on the back of a liquid crystal panel of a transmissive liquid crystal display device or along the edge thereof to provide constant light for display under no influence of external light. Such backlight units may be roughly classified into an edge-type backlight unit wherein lamps are disposed along the edge of the liquid crystal panel to supply light to the panel, and a direct-backing type backlight unit wherein lamps are disposed directly on the back of the liquid crystal panel to supply light to the panel. 
     Recently, the liquid crystal display device has been requested to provide higher-brightness and higher-definition images. In order to meet such a request, high-brightness lamps are provided in the backlight unit. In addition, the lamps are supplied with high lamp current to emit high-brightness light. However, the magnitude of the lamp current to the lamps is in inverse proportion to the service life of the lamps. That is, if the lamp current is raised to obtain high brightness, the service life of the lamps is disadvantageously shortened. Conversely, if the lamp current is reduced to lengthen the service life of the lamps, the brightness of the lamps is disadvantageously lowered. Moreover, the higher the lamp current to the lamps, the larger the power consumption of the liquid crystal display device. 
     Accordingly, an adaptive brightness intensification backlight unit has been developed in order to solve the above problem. This adaptive brightness intensification backlight unit is characterized in that the luminance of video data is analyzed, a brightness control signal is generated according to the analyzed luminance, and the lamps are driven by an inverter in response to the generated brightness control signal. That is, the brightness of the lamps is controlled according to the gray scale of the video data, thereby lengthening the service life of the lamps and preventing unnecessary power consumption required to drive the lamps to generate the same brightness as that of a high gray scale image with respect to a low gray scale image. 
     Next, a description will be given of a conventional liquid crystal display device with an adaptive brightness intensification backlight unit with reference to the annexed drawings. 
       FIG. 3  is a block diagram showing the configuration of a conventional liquid crystal display device with an adaptive brightness intensification backlight unit. 
     As shown in  FIG. 3 , a driving circuit  12  includes an external storage unit  25   a  for storing data stretching values and backlight dimming control values for adaptive brightness intensification, and a DC-DC converter  24  for receiving a voltage from a system through a connector  22 , stepping up or down the received voltage, outputting the resulting drive voltages Vcc and Vdd necessary to respective components, and outputting a gate low voltage signal V GL  and a gate high voltage signal V GH  in response to an enable signal from a timing controller  23 . The timing controller  23  is adapted to, upon power-on, read data stored in the external storage unit (for example, an EEPROM)  25   a  and allow an adaptive brightness intensifier (AI) circuit  31   a  therein to analyze an inputted image and perform a data stretching function and a backlight dimming control function on the basis of the read data as a result of the image analysis to lower backlight brightness. The timing controller  23  is also adapted to receive a video signal from the system and output a control signal to drive a liquid crystal panel  11  of the liquid crystal display device. The driving circuit  12  further includes a gate driver  11   a  for generating a scan pulse in response to the gate high voltage signal V GH  and gate low voltage signal V GL , outputted from the DC-DC converter  24  in response to the enable signal from the timing controller  23 , and supplying the generated scan pulse sequentially to gate lines G of the liquid crystal panel  11 , and a data driver  11   b  for receiving a video signal outputted from the timing controller  23 , digital/analog-converting the received video signal into an analog video signal and supplying the converted analog video signal to each data line D of the liquid crystal panel  11 . The driving circuit  12  further includes an inverter  34  for driving a backlight lamp  35  in response to a control signal from the AI circuit  31   a . The remaining parts of the driving circuit  12  are the same as those illustrated in  FIG. 1 . 
     The AI circuit  31   a  analyzes the luminance of the inputted video data. The video data is usually inputted in the form of an RGB signal containing red, green and blue image information. This video data is composed of a YUV signal including a luminance signal Y and a chrominance signal (U,V), and the AI circuit  31   a  detects the luminance signal from the YUV signal. Then, the AI circuit  31   a  measures a luminance variation for every frame and outputs the resulting control signal to the inverter  34  to adjust the brightness of the backlight lamp  35 . 
     Here, for the convenience of description of communication between the external storage unit  25   a  and the AI circuit  31   a , the external storage unit  25   a  is expressed as a slave and the AI circuit  31   a  is expressed as a master. 
     A look-up table (LUT), the backlight dimming control values and the data stretching values are prestored in the external storage unit  25   a , which is the slave as aforementioned. When the liquid crystal display device is powered on, the DC-DC converter  24  generates and supplies various voltages for the driving of the display device. In particular, the DC-DC converter  24  supplies a drive voltage Vcc for data communication between the external storage unit  25   a  and the AI circuit  31   a.    
     At this time, the drive voltage Vcc from the DC-DC converter  24  is directly supplied to the external storage unit  25   a.    
       FIG. 4  is a circuit diagram of an external storage unit of a conventional over-driving circuit or adaptive brightness intensification backlight unit. 
     In  FIG. 4 , the external storage unit  25  or  25   a  of the conventional over-driving circuit (ODC) or adaptive brightness intensifier (AI) circuit may be, for example, an electrically erasable programmable read only memory (EEPROM). A desired look-up table is created and written in the EEPROM by a microcomputer so as to be used for over-driving or adaptive brightness intensification. 
     The look-up table is created in the following manner. 
     That is, the look-up table is created by arranging values corresponding to a video signal of a previous frame and a video signal of a current frame inputted from the system through the connector  22  in an x-axis and a y-axis, and inputting a value corresponding to a corrected video signal Do at an intersection of the x-axis and y-axis. 
     The conventional external storage unit, or EEPROM,  25  or  25   a  has a plurality of terminals (first to eighth terminals). 
     The EEPROM is connected to an external microcomputer in a write mode and to the driving circuit of the liquid crystal display device in a liquid crystal module drive mode. 
     The first to third terminals  1 ,  2  and  3  are no connection (NC) terminals which are spare terminals applied with no specific data or voltage. These first to third terminals  1 ,  2  and  3  are connected to a ground voltage VSS along with the fourth terminal  4 , which is a ground voltage terminal. In general, the first to third terminals  1 ,  2  and  3  can replace other terminals to which a power supply voltage or a data or clock signal is applied, when they fail. The first to third terminals  1 ,  2  and  3  are grounded regardless of the write mode and the liquid crystal module drive mode before replacing other terminals. 
     The fifth terminal  5  and the sixth terminal  6  receive a data signal SDA and a clock signal SCL from the microcomputer in the write mode, respectively, and receive a supply voltage VCC from an internal supply voltage generator  32  of the liquid crystal display device in the liquid crystal module drive mode. 
     The seventh terminal  7  is a write control (WC) terminal to which the ground voltage VSS is applied so that the EEPROM  25  or  25   a  is in a write enable state. This seventh terminal  7  is always applied with the ground voltage VSS regardless of the write mode and the liquid crystal module drive mode. 
     The eighth terminal  8  is connected to a supply voltage terminal VCC of a connector  40  in the write mode and to the supply voltage VCC in the liquid crystal module drive mode to maintain the EEPROM  25  or  25   a  in the enable state. 
     The above-mentioned conventional external storage unit, or EEPROM,  25  or  25   a  is always maintained in the write enable state because the write control terminal, or seventh terminal  7 , is grounded. For this reason, there is a risk that undesired data may be written in the EEPROM or data written in the EEPROM may be lost, due to external factors of a liquid crystal module (LCM), even in the liquid crystal module drive mode after the write mode is performed. 
       FIGS. 5A and 5B  are photographs showing image quality deteriorations which appear on the screen when a malfunction occurs in the write control terminal of the external storage unit. 
       FIGS. 5A and 5B  show poor display states resulting from the fact that undesired data is written into the EEPROM as the EEPROM is maintained in the enable state due to the grounding of the write control terminal of the EEPROM. 
     In particular, this problem occurs when the over-driving or adaptive brightness intensification is carried out on the basis of a look-up table containing the undesired data written in the EEPROM. 
     In other words, the above-described conventional liquid crystal display device has disadvantages as follows. 
     The EEPROM, which is the external storage unit, is always maintained in the write enable state because the write control terminal is always grounded. For this reason, there is a risk that undesired data may be written in the EEPROM due to external factors when the liquid crystal module is driven. 
     It is thus difficult to secure reliability of the EEPROM. 
     In addition, a poor display state may occur when the over-driving or adaptive brightness intensification is carried out on the basis of a look-up table containing the undesired data written in the EEPROM. Therefore a need exists to secure the reliability of the EEPROM. 
     SUMMARY OF THE INVENTION 
     A circuit for driving a liquid crystal display device having a write mode and a liquid crystal module drive mode includes a master that over-drives and provides adaptive brightness intensification, a slave that provides desired control data to the master, a writing circuit that controls writing of control data to the slave; a connector that connects the writing circuit with a plurality of terminals of the slave that write the control data into the slave. The circuit for driving the liquid crystal display also includes an internal power supply of a liquid crystal module that applies an internal supply voltage to the slave during the liquid crystal module drive mode, where the write mode does not occur during the liquid crystal module drive mode. 
     A circuit for driving a liquid crystal display device that has a write mode and a liquid crystal module drive mode includes a master for over-driving a liquid crystal module and provides adaptive brightness intensification and a slave for providing desired control data to the master. A connector is included for connecting external writing equipment with a plurality of terminals of the slave to write the control data into the slave; and an internal power supply of a liquid crystal module for applying an internal supply voltage to the slave, wherein the plurality of terminals of the slave include a write control terminal which is at or about a ground potential in a write mode, and at or about the potential of the internal power supply of the liquid crystal module in a liquid crystal module drive mode. 
     Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings: 
         FIG. 1  is a block diagram showing a configuration of a conventional liquid crystal display device with an over-driving circuit; 
         FIG. 2  is a block diagram of an over-driving circuit; 
         FIG. 3  is a block diagram of a configuration of a conventional liquid crystal display device with an adaptive brightness intensification backlight unit; 
         FIG. 4  is a circuit diagram of an external storage unit; 
         FIGS. 5A and 5B  are photographs of image quality deteriorations appearing on a screen; 
         FIG. 6  is a circuit diagram of an external storage unit and peripheral elements of an over-driving circuit or adaptive brightness intensification backlight unit where WC is directly to VCC; 
         FIG. 7  is a circuit diagram of an external storage unit with peripheral elements where WC is connected to VCC through a resistive ladder; 
         FIG. 8  is a circuit diagram of an external storage unit and peripheral elements where WP is connected to ground; 
         FIG. 9  is a circuit diagram of an external storage unit and peripheral elements where WP is connected to VCC and an external connector; and 
         FIG. 10  is a block diagram showing connections of an EEPROM in a write mode. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Reference will now be made in detail to the examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
       FIG. 6  is a circuit diagram of an external storage unit, or EEPROM, and peripheral elements of an over-driving circuit or adaptive brightness intensification backlight unit. 
     A driving circuit of a liquid crystal display device may include a gate driver and source driver for applying signals to gate lines and data lines of a liquid crystal panel, and a timing controller (not shown) for applying control signals to the drivers. 
     The driving circuit may include a master (not shown) (see the internal block of the timing controller in  FIGS. 1 and 3 ) for controlling the over-driving and adaptive brightness intensification. 
     As shown in  FIG. 6 , the driving circuit of the liquid crystal display device also may include an external storage unit, or EEPROM,  100  for providing control data (look-up table (LUT)) necessary to the control of the over-driving or adaptive brightness intensification by the timing controller, and a connector  110  for connecting external ROM writing equipment (not shown) with a plurality of terminals of the EEPROM  100  to write the control data into the EEPROM  100 . Among the terminals of the EEPROM  100 , the fifth terminal and the sixth terminal receive a data signal SDA and a clock signal SCL, respectively. The driving circuit further includes an internal power supply VCC of a liquid crystal module for applying an internal supply voltage VCC to the EEPROM  100 . Among the terminals of the EEPROM  100 , the seventh terminal is a write control terminal which is grounded in a write mode and connected to the internal power supply VCC of the liquid crystal module in a liquid crystal module drive mode. A diode  120  is connected between the internal power supply VCC of the liquid crystal module and the eighth terminal of the EEPROM  100 , which is a supply voltage terminal. A first resistor  131  is connected between the internal power supply VCC of the liquid crystal module and the SCL terminal (sixth terminal) of the EEPROM  100 , and a second resistor  132  is connected between the internal power supply VCC of the liquid crystal module and the SDA terminal (fifth terminal) of the EEPROM  100 . 
     The connection between the connector  110  and the EEPROM  100  may be made in the following manner. The first terminal (supply voltage terminal) of the connector  110  is connected with the eighth terminal of the EEPROM  100 , which receives the supply voltage from the internal power supply VCC of the liquid crystal module via the diode  120 . Namely, the eighth terminal of the EEPROM  100  is connected with the cathode of the diode  120  and the first terminal of the connector  110  is connected to a connection point of the eighth terminal of the EEPROM  100  and the cathode of the diode  120 . Therefore, by virtue of the diode  120 , the stable internal supply voltage VCC is applied to the eighth terminal of the EEPROM  100  and the first terminal of the connector  110 . 
     The second terminal of the connector  110  is connected with an SCL terminal of the external ROM writing equipment, and the third terminal of the connector  110  is connected with an SDA terminal of the external ROM writing equipment. 
     The fourth terminal of the connector  110  is a ground terminal which is grounded. This fourth terminal of the connector  110  is grounded together with the first to third terminals of the EEPROM  100 , which are spare terminals, and the fourth terminal of the EEPROM  100 , which is a ground terminal. 
     The operation of the EEPROM  100  in the driving circuit of the liquid crystal display device will hereinafter be described under the condition that it is classified into an operation in the write mode and an operation in the liquid crystal module drive mode. 
     In the write mode, the second terminal of the connector  110  is connected with the SCL terminal of the external ROM writing equipment, and the third terminal of the connector  110  is connected with the SDA terminal of the external ROM writing equipment. 
     The second and third terminals of the connector  110  are also connected with the sixth and fifth terminals of the EEPROM  100 . As a result, the external ROM writing equipment can communicate with the EEPROM  100  in an Inter-IC (“I2C”) communication bus protocol to write desired data into the EEPROM  100 . 
     The seventh terminal of the EEPROM  100 , which is the write control (WC) terminal, is opened and internally pulled down to ground in the EEPROM  100  in the write mode so that the EEPROM  100  can be maintained in the write enable state. 
     On the other hand, in the liquid crystal module drive mode, the EEPROM  100  functions as a memory containing a look-up table for the over-driving or adaptive brightness intensification. In this case, the write control terminal, or the seventh terminal of the EEPROM  100 , is directly connected with the internal power supply VCC of the liquid crystal module so as to be applied with a high signal therefrom. As a result, data (look-up table data) stored in the EEPROM  100  in the write mode can be stably protected. 
     Here, the write control terminal represents a write enable state when being applied with a low signal (ground voltage), and a write protecting state when being applied with a high signal (supply voltage). 
     In the driving circuit of the liquid crystal display device, as stated above, the supply voltage is applied to the write control terminal of the EEPROM in the liquid crystal module drive mode after the write mode is performed. Therefore, the writing of further different data can be prevented so that the data written in the EEPROM can be protected. 
       FIG. 7  is a circuit diagram of an external storage unit, or EEPROM, and peripheral elements of an over-driving circuit or adaptive brightness intensification backlight unit 
     A driving circuit of a liquid crystal display device may include an external storage unit, or EEPROM  101 , for providing control data, in a look-up table (“LUT”), necessary to the control of over-driving or adaptive brightness intensification by a timing controller, and a connector  111  for connecting external ROM writing equipment (not shown) with a plurality of terminals of the EEPROM  101  to write the control data into the EEPROM  101 . Among the terminals of the EEPROM  101 , the fifth terminal and the sixth terminal receive a data signal SDA and a clock signal SCL, respectively. The driving circuit further comprises an internal power supply VCC of a liquid crystal module for applying an internal supply voltage VCC to the EEPROM  101 . Among the terminals of the EEPROM  101 , the seventh terminal is a write control terminal which is grounded in a write mode and connected to the internal power supply VCC of the liquid crystal module in a liquid crystal module drive mode. The connector  111  has a plurality of terminals including a write terminal (second terminal) which is connected with the write control terminal of the EEPROM  101 . 
     The connector  111  has five terminals including the write terminal (second terminal), differently from the connector with the four terminals described in the previous example. The first terminal of the connector  111  is a supply voltage terminal, the third and fourth terminals thereof are connected with an SCL terminal and SDA terminal of the external ROM writing equipment, respectively, and the fifth terminal thereof is a ground terminal. 
     A first resistor  141  is connected between the internal power supply VCC of the liquid crystal module and the eighth terminal of the EEPROM  101 , which is a supply voltage terminal. A second resistor  142  is connected between the internal power supply VCC of the liquid crystal module and the write control terminal, or the seventh terminal of the EEPROM  101 . A third resistor  143  is connected between the internal power supply VCC of the liquid crystal module and the SCL terminal (sixth terminal) of the EEPROM  101 , and a fourth resistor  144  is connected between the internal power supply VCC of the liquid crystal module and the SDA terminal (fifth terminal) of the EEPROM  101 . 
     A fifth resistor  145  is connected between the write control terminal of the EEPROM  101  and the write terminal (second terminal) of the connector  111 . The fifth resistor  145  has a resistance much lower than that of the second resistor  142  (i.e., second resistor&gt;&gt;fifth resistor). For example, the second resistor  142  may be about 10 KΩ and the fifth resistor  145  may be about 100Ω, so that a low voltage (a voltage close to the ground voltage) can be applied to the write control terminal of the EEPROM  101  when the write terminal (second terminal) is connected with the write control terminal. 
     This connection between the write control terminal of the EEPROM  101  and the write terminal (second terminal) of the connector  111  means the write mode. The write control terminal is applied with the low voltage to represent a write enable state. On the other hand, in the liquid crystal module drive mode, the write terminal (second terminal) of the connector  111  is opened and the write control terminal (seventh terminal) of the EEPROM  101  is applied with the internal supply voltage VCC (high voltage), so that data written in the EEPROM  101  can be stably protected. 
     The operation of the EEPROM in the driving circuit of the liquid crystal display device will hereinafter be described under the condition that it is classified into an operation in the write mode and an operation in the liquid crystal module drive mode. 
     In the write mode, the third terminal of the connector  111  is connected with the SCL terminal of the external ROM writing equipment, and the fourth terminal of the connector  111  is connected with the SDA terminal of the external ROM writing equipment. 
     The third and fourth terminals of the connector  111  are also connected with the sixth and fifth terminals of the EEPROM  101 . As a result, the external ROM writing equipment can communicate with the EEPROM  101  in an I2C protocol manner to write desired data into the EEPROM  101 . 
     At this time, in the write mode, the seventh terminal of the EEPROM  101 , which is the write control (WC) terminal, is connected with the internal power supply of the liquid crystal module via the second resistor  142  and with the second terminal of the connector  111  via the fifth resistor  145 . As a result, a low signal (a voltage close to the ground voltage) is applied to the write control terminal so that the EEPROM  101  can be maintained in the write enable state. 
     On the other hand, in the liquid crystal module drive mode, the EEPROM  101  may function as a memory containing a look-up table for the over-driving or adaptive brightness intensification. In this case, the write terminal, or the second terminal of the connector  111 , is opened and the write control terminal, or the seventh terminal of the EEPROM  101 , is thus connected with the internal power supply VCC of the liquid crystal module via the second resistor  142  so as to be applied with a high signal therefrom. As a result, data (look-up table data) stored in the EEPROM  101  in the write mode can be stably protected. 
     In the driving circuit of the liquid crystal display device, as stated above, the supply voltage is applied to the write control terminal of the EEPROM in the liquid crystal module drive mode after the write mode is performed. Therefore, the writing of further different data can be prevented so that the data written in the EEPROM can be protected. 
       FIG. 8  is a circuit diagram of an external storage unit, or EEPROM, and peripheral elements of an over-driving circuit or adaptive brightness intensification backlight unit. 
     In a driving circuit of a liquid crystal display device, the connections between the EEPROM and the peripheral elements may be made in the same manner as those in the previous embodiment, with the exception that the first resistor  141  and fifth resistor  145  in the previous embodiment (see  FIG. 7 ) are omitted, the write control (WC) terminal, or the seventh terminal of the EEPROM, is not connected with the connector and the write terminal (second terminal) of the connector is directly connected with the lower end of a resistor formed between the supply voltage and the write control terminal, as shown in  FIG. 8 . 
     The driving circuit of the liquid crystal display device may include an external storage unit, or EEPROM,  102  for providing control data in a look-up table (LUT) that may be necessary for the control of over-driving or adaptive brightness intensification by a timing controller, and a connector  112  for connecting external ROM writing equipment (not shown) with a plurality of terminals of the EEPROM  102  to write the control data into the EEPROM  102 . Among the terminals of the EEPROM  102 , the fifth terminal and the sixth terminal receive a data signal SDA and a clock signal SCL, respectively. The driving circuit further includes an internal power supply VCC of a liquid crystal module for applying an internal supply voltage VCC to the EEPROM  102 . Among the terminals of the EEPROM  102 , the seventh terminal is a write control terminal which is grounded in a write mode and connected to the internal power supply VCC of the liquid crystal module in a liquid crystal module drive mode. The connector  112  has a plurality of terminals including a write terminal (second terminal) which is connected with the write control terminal of the EEPROM  102 . 
     The connector  112  has five terminals including the write terminal (second terminal), similarly to the embodiment of  FIG. 7 . In  FIG. 8 , the first terminal of the connector  112  is a supply voltage terminal, the third and fourth terminals thereof are connected with an SCL terminal and SDA terminal of the external ROM writing equipment, respectively, and the fifth terminal thereof is a ground terminal. 
     A first resistor  151  is connected between the internal power supply VCC of the liquid crystal module and the write control terminal, or the seventh terminal of the EEPROM  102 . A second resistor  152  is connected between the internal power supply VCC of the liquid crystal module and the SCL terminal (sixth terminal) of the EEPROM  102 , and a third resistor  153  is connected between the internal power supply VCC of the liquid crystal module and the SDA terminal (fifth terminal) of the EEPROM  102 . 
     The write terminal, or the second terminal of the connector  112 , is grounded in the write mode, and connected between the first resistor  151  and the write control terminal, or the seventh terminal of the EEPROM  102 , in the liquid crystal module drive mode so as to be applied with a supply voltage signal (a high signal close to VCC). Thus, the EEPROM can be maintained in the write enable state in the write mode and data written in the EEPROM can be stably maintained and protected in the liquid crystal module drive mode after the write mode is performed. 
     The operation of the EEPROM in the driving circuit of the liquid crystal display device will hereinafter be described under the condition that it is classified into an operation in the write mode and an operation in the liquid crystal module drive mode. 
     In the write mode, the third terminal of the connector  112  is connected with the SCL terminal of the external ROM writing equipment, and the fourth terminal of the connector  112  is connected with the SDA terminal of the external ROM writing equipment. 
     The third and fourth terminals of the connector  112  are also connected with the sixth and fifth terminals of the EEPROM  102 . As a result, the external ROM writing equipment can communicate with the EEPROM  102  in an I2C protocol manner to write desired data into the EEPROM  102 . 
     In the liquid crystal module drive mode, the write terminal, or the second terminal of the connector  112 , is connected between the first resistor  151  and the write control terminal, or the seventh terminal of the EEPROM  102 , so as to be applied with a supply voltage signal (a high signal close to VCC). 
     In this liquid crystal module drive mode, the EEPROM  102  functions as a memory containing a look-up table for the over-driving or adaptive brightness intensification. In this case, the write terminal, or the second terminal of the connector  112 , is connected with the lower end of the first resistor  151  so as to be applied with the supply voltage signal. As a result, data (look-up table data) stored in the EEPROM  102  in the write mode can be stably protected. 
     In the driving circuit of the liquid crystal display device, as stated above, the supply voltage is applied to the write control terminal of the EEPROM in the liquid crystal module drive mode after the write mode is performed. Therefore, the writing of further different data can be prevented so that the data written in the EEPROM can be protected. 
       FIG. 9  is a circuit diagram of another embodiment of an external storage unit, or EEPROM, and peripheral elements of an over-driving circuit or adaptive brightness intensification backlight unit. 
     In a driving circuit of a liquid crystal display device, the connections between the EEPROM and the peripheral elements are made in the same manner as those in the embodiment of  FIG. 6 , with the exception that the write terminal, or the second terminal of the connector, is connected with the external ROM writing equipment in the write mode so as to be operated under control of the external ROM writing equipment. 
     The driving circuit of the liquid crystal display device may include an external storage unit, or EEPROM,  103  for providing control data (in a look-up table (LUT)) necessary for the control of over-driving or adaptive brightness intensification by a timing controller, and a connector  113  for connecting external ROM writing equipment (not shown) with a plurality of terminals of the EEPROM  103  to write the control data into the EEPROM  103 . Among the terminals of the EEPROM  103 , the fifth terminal and the sixth terminal receive a data signal SDA and a clock signal SCL, respectively. The driving circuit further comprises an internal power supply VCC of a liquid crystal module for applying an internal supply voltage VCC to the EEPROM  103 . Among the terminals of the EEPROM  103 , the seventh terminal is a write control terminal which is grounded in a write mode and connected to the internal power supply VCC of the liquid crystal module in a liquid crystal module drive mode. The connector  113  has a plurality of terminals including a write terminal (second terminal) which is connected with the write control terminal of the EEPROM  103 . 
     The connector  113  has five terminals including the write terminal (second terminal), similarly to the embodiment of  FIG. 8 . The first terminal of the connector  113  is a supply voltage terminal, the third and fourth terminals thereof are connected with an SCL terminal and SDA terminal of the external ROM writing equipment, respectively, and the fifth terminal thereof is a ground terminal. 
     A first resistor  161  is connected between the internal power supply VCC of the liquid crystal module and the write control terminal, or the seventh terminal of the EEPROM  103 . A second resistor  162  is connected between the internal power supply VCC of the liquid crystal module and the SCL terminal (sixth terminal) of the EEPROM  103 , and a third resistor  163  is connected between the internal power supply VCC of the liquid crystal module and the SDA terminal (fifth terminal) of the EEPROM  103 . 
     In write mode, the write terminal, or the second terminal of the connector  113 , is connected with a specific terminal of the external ROM writing equipment so as to be operated in response to a command from the ROM writing equipment. In the liquid crystal module drive mode, the second terminal of the connector  113  is connected between the first resistor  161  and the write control terminal, or the seventh terminal of the EEPROM  103 , so as to be applied with a supply voltage signal (a high signal close to VCC). Thus, the EEPROM can be maintained in the write enable state in the write mode and data written in the EEPROM can be stably maintained and protected in the liquid crystal module drive mode after the write mode is performed. 
     In the driving circuit of the liquid crystal display device, in the liquid crystal module drive mode, the write terminal of the connector  113  is connected with the lower end of the first resistor  161  so as to be applied with the internal supply voltage. As a result, data written in the EEPROM  103  can be protected. 
     In the write mode, the write terminal of the connector  113  is connected with the ROM writing equipment so that the writing operation can be stably performed under no influence of leakage current. 
       FIG. 10  is a block diagram showing connections of an EEPROM in a write mode. The writing of the EEPROM may be performed through I2C protocol communication using a connector  200 . 
     At this time, external ROM writing equipment is connected with the connector  200 . The ROM writing equipment may include a microcomputer unit  212  for managing a series of control operations required for the writing of the EEPROM  201  or  220 , a memory  213  for sending and receiving data to/from the microcomputer unit  212 , a keypad  214  for applying a desired command to the microcomputer unit  212  in response to the user&#39;s operation, a battery  215  for applying a drive voltage to the microcomputer unit  212 , a power on/off unit  217  for applying a power on/off signal to the battery  215 , and a regulator  218  for regulating a supply voltage from the battery. The microcomputer unit  212  may be connected to an external host computer  210  via an interface  211 . 
     The microcomputer unit  212  also may control a start time and end time of signal application to the EEPROM  201  or  220  through a status  216  indicative of a start or end. 
     The EEPROM  201  or  220  may be connected, through predetermined pins, with a master in a timing controller  221 ,  222  or  223  in a liquid crystal display module. The master is an over-drive circuit that supplies an over gray scale voltage to data lines of a liquid crystal panel, and/or an AI circuit that adjusts backlight brightness according to a luminance variation of every frame of inputted video data. 
     The EEPROM acts as a slave that stores a look-up table (LUT) for over-driving or adaptive brightness intensification. The external ROM writing equipment is separated from the EEPROM  220  after performing the writing of the EEPROM. 
     As apparent from the above description, the driving circuit of the liquid crystal display device according to the embodiments has effects as follows. 
     Firstly, the write control pin of the EEPROM is grounded in the write mode so that the EEPROM can be maintained in the write enable state, and is connected with the internal supply voltage of the liquid crystal module in the liquid crystal module drive mode so that the data stored in the EEPROM can be protected. Therefore, the writing of further different data in the EEPROM can be prevented in the liquid crystal module drive mode, thereby making it possible to prevent a poor display state from occurring when the over-driving or adaptive brightness intensification is carried out on the basis of the look-up table in the EEPROM. 
     Secondly, the data written in the EEPROM can be protected, thereby reducing expenses resulting from processes conducted at the user&#39;s request caused by data loss. 
     Thirdly, the present invention is applicable to all models using the EEPROM as the look-up table. 
     It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.