Abstract:
A driving system for a liquid crystal display includes an analog driving circuit unit, a digital analog converter and a digital interface unit. The digital analog converter supplies an analog voltage for operating the analog driving circuit unit. The digital interface unit supplies a digital signal to the digital analog converter. The analog driving circuit units, the digital analog converter and the digital interface unit may be mounted on a single chip.

Description:
PRIORITY CLAIM  
       [0001]     This application claims the benefit of Korean Application No. 2003-99347, filed on Dec. 29, 2003. The disclosure of the above application is incorporated herein by reference.  
       BACKGROUND  
       [0002]     1. Technical Field  
         [0003]     The invention relates to a liquid crystal display (LCD), and more particularly, to a driving system for an LCD in which an analog driving circuit unit is controlled in a programmable manner.  
         [0004]     2. Related Art  
         [0005]     LCDs are used for a large number of information processing devices such as computers because of slim and lightweight designs and good performances as display devices. As demands for LCDs increase, it is required to improve an image quality of LCDs such as brightness, contrast ratio, etc.  
         [0006]      FIG. 1  illustrates a block diagram of an LCD module  1 . As shown in  FIG. 1 , the LCD module  1  includes a digital video card  10 , a controller  11 , a gate driver  12 , a data driver  13  and a liquid crystal panel  20 . The digital video card  10  converts analog image signals into digital image signals. The controller  11  receives digital image signals from the digital video card  10  and controls the gate driver  12  and the data driver  13 . The gate driver  12  turns on/off a thin film transistor (“TFT”), which is a switching element of a liquid crystal panel  20  by receiving scanning signals controlled by the controller  11 . The LCD module  1  further includes a gamma circuit  15 , which provides to the data driver  13  gamma voltages to change transmittance of liquid crystal used in the liquid crystal panel  20 . The data driver  13  provides gamma voltages corresponding to digital image signals from the controller  11  to a pixel area of the liquid crystal panel  20 . The LCD module  1  also includes a Vcom circuit  40  and an inverter controller  50 , which will be described in detail below in connection with  FIG. 2 .  
         [0007]     The LCD module  1  operates as follows. Digital image signals from the digital video card  10  are first transmitted to the controller  11 . The controller  11  synchronizes the digital image signals and provides synchronized signals to the data driver  13 . In addition, the controller  11  delivers to the gate driver  12  scanning signals for turning on/off the TFTs connected with the data lines. The data driver  13  converts digital image signals delivered from the controller  11  to analog image signals and sequentially transfers the analog signals to a plurality of data lines formed on the liquid crystal panel  20 . When the digital image signals are converted into the analog image signals, the gamma circuit  15  provides a gamma voltage for controlling the transmittance of the liquid crystal. Specifically, the gamma voltage provided by the gamma circuit  15  is divided into a plurality of tone voltages by resistor circuits disposed inside of the gamma circuit  15 . Each divided tone voltage corresponds to each digital image signal and is eventually outputted to the respective data line as analog image signals. Meanwhile, the gate driver  12  turns on/off the TFT by sequentially providing scanning signals to a plurality of gate lines formed on the liquid crystal panel  20 . Accordingly, the analog image signals delivered from the data lines are transferred to a respective pixel area.  
         [0008]      FIG. 2  is a circuit diagram showing an analog driving circuit unit  31  for an LCD according to the related art. Referring to  FIG. 2 , the analog driving circuit  31  includes a gamma circuit  15 , a Vcom circuit  40  and an inverter controller  50 . The Vcom circuit  40  provides a common reference voltage to a liquid crystal panel and an inverter controller  50  controls an inverter, which controls a backlight. The gamma circuit  15 , the Vcom circuit  40  and the inverter controller  50  are configured separately from one another as shown in  FIG. 2 .  
         [0009]     The gamma circuit  15  has a plurality of resistors R 1 , R 2 , . . . Rn, which are connected in series and divide a voltage. Each resistor R 1 , R 2 , . . . Rn is connected to a buffer  35  which includes an operational amplifier (“OP Amp”), respectively. Another resistors R 11  . . . Rnn are connected to an output terminal of the buffer so that the previously divided voltage may be divided again. The respective gamma voltage is outputted therefrom.  
         [0010]     The Vcom circuit  40  has the following construction. A plurality of resistors R 101 , R 102  . . . and a variable resistor VR 1  are connected in series and divide a voltage. Each divided voltage is transferred to a buffer  45  including an OP Amp. An output terminal of the buffer  45  outputs a Vcom voltage which is appropriate for a liquid crystal panel. The inverter controller  50  receives an analog voltage and converts the voltage by using resistors disposed therein (not shown). Consequently, the inverter controller  50  generates a control signal for driving an inverter of an LCD.  
         [0011]     The analog driving circuits  31  results in a large size and high manufacturing costs because each driving circuit needs to be separately manufactured. Further, because an output voltage is generated after the analog voltage is divided by multiple resistors, such voltage is not generated in a programmable manner. Specifically, once resistances of multiple resistors are determined, it is not possible to change output voltages generated by multiple resistors. Consequently, the analog driving circuits  31  cannot be controlled by a digital processor that processes digital image signals. There is a need for a driving circuit for an LCD that overcomes the foregoing drawbacks of the related art.  
       SUMMARY  
       [0012]     A driving system for an LCD is provided that includes an analog driving circuit unit, a digital analog converter and a digital interface unit. The digital analog converter supplies an analog voltage that operates the analog driving circuit unit. The digital interface unit supplies a digital signal to the digital analog converter. The analog driving circuit unit, the digital analog converter and the digital interface unit may be formed on a single chip. In one embodiment, an analog driving circuit unit includes a gamma circuit, a common circuit, and an inverter controller.  
         [0013]     A driving system for an LCD can improve a display quality by integrating the analog driving circuit unit with other circuit elements and controlling it with a control signal. A digital image signal processor and/or an EEPROM (Electronically Erasable Programmable Read Only Memory) generate and provide such control signal. Accordingly, the driving circuit can control the analog driving circuit unit in a programmable manner.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]     The invention can be better understood with reference to the following drawings and description. The components in the figures are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. Moreover, in the figures, like referenced numerals designate corresponding parts throughout the different views.  
         [0015]      FIG. 1  is a block diagram showing a related art LCD module;  
         [0016]      FIG. 2  is a circuit diagram showing an analog driving circuit unit according to the related art; and  
         [0017]      FIG. 3  is a block diagram showing one embodiment of an analog driving circuit unit. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0018]      FIG. 3  shows one embodiment of an analog driving circuit unit  100  for an LCD module. An LCD module including the analog driving circuit unit  100  has structures similar to that of the LCD module  1  as shown in  FIG. 1 . Specifically, the LCD module includes a digital video card, a controller, a gate driver, a data driver and a liquid crystal panel that may have structures and operations similar to those of the digital video card  10 , the controller  11 , the gate driver  12 , the data driver  13  and the liquid crystal panel  20 . Accordingly, detailed descriptions thereon are omitted here.  
         [0019]     Referring to  FIG. 3 , the analog driving circuit unit  100  includes a gamma circuit  105 , a Vcom circuit  107 , an inverter controller  109 , a digital/analog converter unit  103  and a digital interface unit  101 . The Vcom circuit  105  provides a common reference voltage on a liquid crystal panel and the inverter controller  109  generates a control signal for driving an inverter. A digital/analog converter (“DAC”) unit  103  provides analog signals to the gamma circuit  105 , and at least one of the Vcom circuit  107  and the inverter controller  109 , respectively. More preferably, the DAC unit  103  provides analog signals to the gamma circuit  105 , the Vcom circuit  107  and the inverter controller  109 . The digital interface unit  101  provides a digital control signal to the DAC unit  103 . The analog driving circuit unit  100  may integrate the gamma circuit  105 , the Vcom circuit  107  and the inverter controller  109  on a single chip. The DAC unit  103 , the digital interface unit  101 , a digital signal processor (“DSP”)  200  and EEPROM  300  may be also on a single chip as shown in  FIG. 3 .  
         [0020]     In operation, the DSP  200  receives a digital image signal from an input terminal  201 . The input terminal  201  of the DSP  200  may be disposed between a digital video card such as the digital video card  10  and a controller such as the controller  11 . Alternatively, the input terminal  201  may be disposed between a controller such as the controller  11  and a data driver such as the data driver  13 . The DSP  200  analyzes the digital image signal per frame and determines whether at least one image quality, for example, a brightness or a contrast ratio, needs to be adjusted. The EEPROM  300  stores various control signals as default values. The DSP  200  fetches a control signal that adjusts the image quality from the EEPROM  300  and provides it to the digital interface unit  101 . Alternatively, if the EEPROM  300  does not store a necessary control signal, the DSP  200  may generate such control signal. Then, the control signal is transmitted to the DAC unit  103  through the digital interface unit  101 . The DAC unit  103  converts the control signal into an analog signal and directly transmits it to the gamma circuit  105 , the Vcom circuit  107  and/or the inverter controller  109 .  
         [0021]     An example of the above operation is described. The DSP  200  analyzes an image data at frame  1 . The DSP  200  determines that a brightness of the image data should be adjusted because the image data is too dark. The DSP  200  verifies whether the EEPROM  300  stores a control signal that increases a brightness of a backlight. If the EEPROM  300  stores the control signal, the control signal is selected and transmitted to a digital interface unit  101 . If the EEPROM  300  does not store the control signal, the DSP  200  may generate a necessary control signal. The control signal from the EEPROM  300  is provided to the DAC  103  via the digital interface unit  101 . Subsequently, the DAC unit  103  converts this signal into an analog voltage and provides the same to the inverter controller  109 . Based on the received analog voltage, the inverter controller  109  controls an inverter that drives a backlight of a liquid crystal panel such as the liquid crystal panel  20 . The brightness of the backlight of the liquid crystal panel is increased and an image data at frame  2 , which is brighter than the image data at the frame  1 , is displayed.  
         [0022]     Alternatively, as a result of analyzing the image data, the DSP  200  may determine that a contrast ratio is required to be adjusted. Then, either the DSP  200  or the EEPROM  300  provides a control signal for changing a gamma voltage to the DAC unit  103  through the digital interface unit  101 . The DAC unit  103  converts this control signal into an analog signal and provides the same to the gamma circuit  105 . The gamma circuit  105  provides the analog signal to a liquid crystal panel through a data driver such as the data driver  13 . The analog voltage provided to the gamma circuit  105  is not divided by multiple resistors (as shown in  FIG. 2 ) but is controlled by the DSP  200 . As such, the gamma circuit  105  does not need multiple resistors. The construction of the gamma circuit  105  may require a buffer  105   a  and an output terminal. Alternatively, or additionally, It is possible to omit the buffer  105   a.  Accordingly, a circuit construction is substantially simplified.  
         [0023]     The Vcom circuit  107  may be configured in a manner that the gamma circuit  105  is configured as described above. Specifically, the DSP  200  analyzes an image data and determines that a reference voltage needs to be adjusted. A Vcom control signal in a digital signal format is provided to the DAC unit  103 . The DAC unit  103  converts the digital signal into an analog voltage and provides it to the Vcom circuit  107 . The Vcom circuit  107  provides the analog voltage to a liquid crystal panel. Because the Vcom circuit  107  does not require circuit elements such as resistors and variable resistors, a simple construction is possible. The analog voltage provided to the Vcom circuit  107  is controlled by the control signal provided from the EEPROM  300  or generated from the DSP  200 . Analog voltage is transmitted through a buffer  107   a  of the Vcom circuit  107 , but the buffer  107   a  may be omitted.  
         [0024]     The DSP  200  of the analog driving circuit unit  100  consistently analyzes a displayed image and preferably provides control signals to the gamma circuit  105 , the Vcom circuit  107  and/or the inverter controller  109 . As a result, a display quality is optimized. As a result, analog circuits are controlled by the DSP  200  in a programmable manner. Furthermore, the analog circuits can be arranged to be integrated on a single chip. This arrangement facilitates control of the analog circuits by the DSP  200  and reduces manufacturing costs and device sizes.  
         [0025]     While various embodiments of the invention have been described, it will be apparent to those of ordinary skill in the art that many more embodiments and implementations are possible within the scope of the invention. Accordingly, the invention is not to be restricted except in light of the attached claims and their equivalents.