Abstract:
A flat panel display includes a panel assembly provided with a plurality of gate lines, a plurality of data lines and switching elements connected to the gate lines and the data lines; a signal controller synthesizing digital image data and control signals from an external device and generating synthesized signals and gate control signals; a column driver applying analogue data voltages corresponding to the digital image data to the data lines responsive to the synthesized signals; and a gate driver applying the gate control signals to the gate lines.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     (a) Field of the Invention  
         [0002]     The present invention relates to a column driver and a flat panel display having the same.  
         [0003]     (b) Description of Related Art  
         [0004]     Generally, flat panel displays (“FPDs”) convert digital image data such as R, G and B from a host computer into analogue data to display desired gray scale or color image.  
         [0005]      FIG. 1  is a block diagram of a conventional flat panel display.  
         [0006]     Referring to  FIG. 1 , the FPD  1000  includes a flat panel assembly  1100 , column drivers  1200 , gate drivers  1300  and a signal controller  1400 .  
         [0007]     When the flat panel assembly  1100  has, for example, resolution of XGA grade (1024×768), the flat panel assembly  1100  includes 3,072 (=1024×3) data lines (not shown),  768  gate lines (not shown), a plurality of switching elements (not shown) and a plurality of pixels (not shown). Such structure is generally referred to as an active matrix structure.  
         [0008]     The column drivers  1200  convert the digital image data from the signal controller  1400  to analogue data voltages which are transmitted to the pixels via the data lines. In  FIG. 1 , the column drivers  1200  have called a single bank structure formed on one side of the panel assembly  1100 .  
         [0009]     The gate drivers  1300  turn on the switching elements in a row simultaneously such that the analogue data voltages driven by the column drivers  1200  are applied to the pixels connected thereto.  
         [0010]     The signal controller  1400  receives the digital image data and control signals from a host computer (not shown). In detail, the signal controller  1400  receives the digital image data and the control signals from the host computer in a general digital interface scheme, e.g., a low voltage differential signaling (“LVDS”) scheme.  
         [0011]     Further, the signal controller  1400  includes an LVDS receiver  1410 , a timing generator  1420  and a reduced swing differential signaling (“RSDS”) transmitter  1430 .  
         [0012]     The LVDS receiver  1410  receives the digital image data and the control signals from an external device. The timing generator  1420  converts the control signals into a plurality of control signals suitable for the column drivers  1200  and the gate drivers  1300 . The RSDS transmitter  1430  converts the digital image data and the control signals of the LVDS scheme into those of the RSDS scheme for transmittance to the column drivers  1200 .  
         [0013]      FIG. 2  is a conventional operation timing chart and  FIG. 3  is a drawing to illustrate the formats of digital image data of an RSDS scheme.  
         [0014]     Referring to  FIGS. 2 and 3 , if the digital image data is signals of 6 bits, respectively, the signal controller  1400  transmit the digital image data and the control signals via three pairs of signal lines (not shown) for each of RGB and a pair of clock lines (not shown). In detail, the signal controller  1400  transmits them to the column drivers  1200  via nine pairs (=three pairs×RGB) of the signal lines and a pair of the clock lines.  
         [0015]      FIG. 4  is a detail block diagram of a column driver of an RSDS scheme.  
         [0016]     Referring to  FIG. 4 , the column drivers  1200  includes an RSDS receiver  1210 , a shift register  1220 , a data register  1230 , a data latch  1240 , a D/A converter  1250  and an output buffer  1260 .  
         [0017]     The RSDS receiver  1210  receives the digital image data of the RSDS scheme from the signal controller  1400 . The shift register  1220  gets the digital image data to be loaded from the data register  1230  to the data latch  1240  at a time. The signal controller  1400  transmits the digital image data to the column driver  1200  until all the latches of the data latch  1240  are filled with the data. The signal controller  1400  also transmits the digital image data to the column driver  1200  until all the row data are loaded. Subsequently, the column driver  1200  loads the digital image data loaded to the data latch  1240  to the D/A converter  1250 . The D/A converter  1250  converts the digital image data into the analogue data voltages. Thereafter, the output buffer  1260  applies the analogue data voltages to the respective data lines of the panel assembly  1100 .  
         [0018]     Typically, the FPD transmits the digital image data and the control signals via a plurality of signal lines and clock lines. Such form of transmission has problems that power consumption and electromagnetic interference (“EMI”) increase.  
       SUMMARY OF THE INVENTION  
       [0019]     An object of the present invention is to provide a flat panel display capable of decreasing power consumption and EMI.  
         [0020]     A flat panel display is provided, which includes a panel assembly provided with a plurality of gate lines, a plurality of data lines and switching elements connected to the gate lines and the data lines; a signal controller synthesizing digital image data and control signals from an external device and generating synthesized signals and gate control signals; a column driver applying analogue data voltages corresponding to the digital image data to the data lines responsive to the synthesized signals; and a gate driver applying the gate control signals to the gate lines.  
         [0021]     The synthesized signals may be generated responsive to a data output control signal.  
         [0022]     The synthesized signals may include a polarity control signal POL, a load signal LOAD and a horizontal synchronization start signal STH.  
         [0023]     The polarity control signal and the load signal may be transmitted via different data buses of the plurality of data buses. The polarity control signal and the load signal are preferably generated during a data blank interval.  
         [0024]     The polarity control signal may be generated based on a logic combination of the data output control signal and the digital image data. For example, the polarity control signal and the load signal may be generated when the data output control signal is in the logic state of low.  
         [0025]     The signal controller may operate in a current driving scheme.  
         [0026]     The signal controller outputs the synthesized signals to the column drivers that are arranged in symmetry with respect to central point of the panel assembly.  
         [0027]     Herein, the column driver may include a plurality of column driving elements and the column driving elements may be connected to each other by cascade connection.  
         [0028]     A flat panel display is provided, which includes a panel assembly provided with a plurality of gate lines, a plurality of data lines and switching elements connected to the gate lines and the data lines; a signal controller synthesizing digital image data and a first control signal from an external device and generating a synthesized signal, a second control signal and a gate signal; a column driver applying analogue data voltages corresponding to the digital image data to the data lines responsive to the synthesized signal and the second control signal; and a gate driver applying the gate signal to the gate lines.  
         [0029]     The second control signal may include a horizontal synchronization start signal STH and a load signal LOAD depending on a logic combination of a data enable signal DE.  
         [0030]     The horizontal synchronization start signal may be generated when the data enable signal is in the logic state of high and the second control signal is in the logic state of low and the load signal may be generated when the data enable signal is in the logic state of low and the second control signal is in the logic state of low.  
         [0031]     A column driver is provided, which includes a digital signal generator generating a horizontal synchronization start signal STH and a load signal LOAD responsive to a control signal from an external device; a shift register receiving the horizontal synchronization start signal; a data latch receiving the load signal; a D/A converter receiving a polarity control signal; and an output buffer.  
         [0032]     The digital signal generator may operate responsive to a logic combination of the control signal and a data enable signal DE.  
         [0033]     The horizontal synchronization start signal may be generated when the data enable signal is in the logic state of high and the control signal is in the logic state of low and the load signal may be generated when the data enable signal is in the logic state of low and the control signal is in the logic state of low. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]     The present invention will become more apparent by describing preferred embodiments thereof in detail with reference to the accompanying drawings in which:  
         [0035]      FIG. 1  is a block diagram of a conventional FPD;  
         [0036]      FIG. 2  is an operation timing chart of a conventional FPD;  
         [0037]      FIG. 3  is a drawing to illustrate the formats of digital image data of an RSDS scheme;  
         [0038]      FIG. 4  is a detail block diagram of a conventional column driver of an RSDS scheme;  
         [0039]      FIG. 5  is a block diagram of an FPD according to the first embodiment of the present invention;  
         [0040]      FIG. 6  illustrates the relation of the connection of the signals controller and the column driver shown in  FIG. 5 ;  
         [0041]      FIG. 7  is a detail circuit diagram of the column driver shown in  FIG. 5 ;  
         [0042]      FIG. 8  is an operation timing chart of the FPD shown in  FIG. 5 ;  
         [0043]      FIG. 9  is an operation timing chart of an FPD according to the second embodiment of the present invention;  
         [0044]      FIG. 10  is an operation timing chart of an FPD according to the third embodiment of the present invention; and  
         [0045]      FIG. 11  is a detail block diagram of the column driver shown in  FIG. 5   
     
    
     DETAILED DESCRIPTION OF EMBODIMENTS  
       [0046]     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the inventions invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein.  
         [0047]     In the drawings, the thickness of layers and regions are exaggerated for clarity. Like numerals refer to like elements throughout. It will be understood that when an element such as a layer, film, region, substrate or panel is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. In contrast, when an element is referred to as being “directly on” another element, there are no intervening elements present.  
         [0048]     Then, a column driver and a FPD having the same according to embodiments of the present invention will be described with reference to the drawings.  
         [0049]      FIG. 5  is a block diagram of an FPD according to the first embodiment of the present invention.  
         [0050]     Referring to  FIG. 5 , the FPD  5000  according to the first embodiment of the present invention includes a panel assembly  5100 , column drivers  5200 , gate drivers  5300  and a signal controller  5400 .  
         [0051]     The FPD  5000  may be a thin film transistor liquid crystal display (TFT-LCD) of an active matrix structure. However, the FPD  5000  is not limited to the TFT-LCD of an active matrix structure.  
         [0052]     The signal controller  5400  includes an LVDS receiver  5410 , a timing generator  5420  and a current driver  5430 .  
         [0053]     The LVDS receiver  5410  transmits digital image data such as R, G and B of an LVDS scheme and control signals such as Hsync, Vsync and CTR from a host computer (not shown) to the timing generator  5420 . The timing generator  5420  generates control signals required for the column drivers  5200  and the gate drivers  5300 . The current driver  5430  synthesizes the digital image data R, G and B of the LVDS scheme and the control signals in a current driving scheme for transmittance to the column drivers  5200 .  
         [0054]     The column drivers  5200  are comprised of a plurality of column driving elements  5210  to  5260  which are connected to each other by cascade connection. The column driving elements  5210  to  5260  are preferably arranged in symmetry with respect to the input from the signal controller  5400 . However, the FPD is not limited to the symmetrical structure and may be embodied in many different forms. Further, the FPD may employ digital interface of a voltage driving scheme or a current driving scheme.  
         [0055]     The gate drivers  5300  are comprised of a plurality of gate driving elements directly mounted on the panel assembly  5100 , which operate in a way that the adjacent gate driving element receives many kinds of control signals from the signal controller  5400  for transmittance to the subsequent gate driving element. Further, the gate drivers  5300  apply control signals for control of the switching elements to the gate lines. Such structure is typical a chip on glass (“COG”) type, the gate drivers  5300  may be, however, integrated together with the switching elements.  
         [0056]      FIG. 6  illustrates relation of connection of the signals controller  5400  and the column driving elements  5210  to  5260  shown in  FIG. 5 .  
         [0057]     Referring to  FIGS. 5 and 6 , a group of column driving elements  5210  to  5230  are connected to the signal controller  5400  sequentially and other group of column driving elements  5240  to  5260  are connected to the signal controller  5400  sequentially.  
         [0058]     The column driving element  5240  is supplied with a clock signal CLKR, a first control signal DIOR and data DataR from the signal controller  5400  and the column driving element  5210  is supplied with a clock signal CLKL, a first control signal DIOL and data DataL. The first control signal DIO is sometimes referred to as the data output control signal. In the preset embodiment, clock signals CLKR AND CLKL are the same clock signal derived from the clock signal CLK and are therefore denoted as clock signal CLK in  FIG. 5 . Similarly, the first control signal DIOR and DIOL are the same control signal and are therefore denoted as first control signal DIO in  FIG. 5 .  
         [0059]     The column driving elements  5240  and  5210  receive all the data related thereto and then transmit control signals and data corresponding to the subsequent column driving elements  5220  and  5250  from the signal controller  5400  thereto. The column driving elements  5220  and  5250  repeat such operations.  
         [0060]     Each column driving element  5210  to  5260  recognizes a HORIZONTAL SYNCHRONIZATION START SIGNAL and a load signal in response to the combination of a logic state of the first control signal and the data signals.  
         [0061]     The signal controller  5400  outputs a polarity control signal POL to other data bus during a predetermined interval. That is, the polarity control signal POL is transmitted to each column driving element  5210  to  5260  during an interval with no digital image data.  
         [0062]     Accordingly, the FPD  5000  according to the first embodiment of the present invention does not require signal lines for transmitting the polarity control signal POL and the load signal LOAD, and according thereto it is possible to reduce the number of the signal lines and current consumption and EMI, sequentially.  
         [0063]      FIG. 7  is a detail block diagram of the column driving element shown in  FIG. 5 .  
         [0064]     Referring to FIGS.  5  to  7 , each column driving element  5210  to  5260  is bidirectional. The column driving element  5210  transmits the control signals and the data to the column driving circuit  5220  which transmits them to the column driving circuit  5230 , sequentially. Further, the column driving elements  5240  to  5260  transmit the control signals and the data in the same manner.  
         [0065]     A detail block diagram of column driving element  5210  will be described in detail with reference to  FIG. 7 . The other column driving elements can have the same structure as the column driving element shown in  FIG. 7 .  
         [0066]     The column driving element  5210  includes a first transceiver  5211 , a first input buffer  5212 , a second transceiver  5213 , a second input buffer  5214 , a logic circuit  5215 , a data latch and selector  5216 , a D/A converter  5217  and an output buffer  5218 .  
         [0067]     Directions of transmitting signals of the first and the second input buffers  5212  and  5214  and the logic circuit  5215  are determined on the basis of logic states of control signals SHL and SHLB outputted from the signal controller  5400 .  
         [0068]      FIG. 8  is an operation timing chart of the FPD shown in  FIG. 5 .  
         [0069]     An operation of each column driving element  5120  to  5260  will be described with reference to FIGS.  5  to  8 .  
         [0070]     In interval A, the signal controller  5400  generates a clock signal CLK, a first control signal DIO, a second control signal and a polarity control signal POL.  
         [0071]     During the interval A, the signal controller  5400  transmits the clock signal CLK, the first control signal DIO in the logic state of low and the second control signal in the logic state of low to the first column driving element  5210  via a first data line D 00  of the plurality of data lines D 00  to Dxx. Further, the signal controller  5400  transmits the polarity control signal POL to the first column driving element  5210  via the second data line D 01 .  
         [0072]     The first input buffer  5212  enabled responsive to the control signal SHL transmits many signals such as CLK, DIO and DATAL from the first transceiver  5211  to the logic circuit  5215 . In this case, the second input buffer  5214  is disabled responsive to a control signal SHLB. The control signals SHL and SHLB are preferably complementary.  
         [0073]     In the interval A, the logic circuit  5215  recognizes a combination of the first control signal DIO and the second control signal in the logic state of low as a data start signal Load. The logic circuit  5215  receives and latches the polarity control signal POL. The polarity control signal POL is used as a signal for determining output polarity of the latched display data.  
         [0074]     During transmitting interval TD of the digital image data, the signal controller  5400  transmits the first control signal DIO in the logic state of high and the digital image data DATAL to the column driving element  5210  via the data lines D 00  to Dxx.  
         [0075]     The logic circuit  5215  transmits the digital image data DATAL to the data latch and selector  5216  which receives and latches the digital image data DATAL allocated to the column driving element  5210  synchronized with falling and rising edges of the clock signal CLK. The D/A converter  5217  converts the digital image data DATAL into analogue voltages according to corresponding gray voltages.  
         [0076]     Before the entire digital image data DATAL allocated to the column driving element  5210  are latched to the data latch and selector  5216 , the column driving element  5210  generates and transmits the first control signal DIO in the logic state of low to the adjacent column driving element  5220  via the first data line D 00  and transmits the latched polarity control signal POL thereto via the second data line D 01 , during the transmitting interval TD of the digital image data.  
         [0077]     Accordingly, the column driving element  5220  receives the first control signal DIO in the logic state of low and the second control signal in the logic state of low and thereafter is ready to receive the digital image data DATAL allocated thereto. The column driving element  5220  latches the digital image data DATAL allocated thereto synchronized with the rising and falling edges of the clock signal CLK.  
         [0078]     That is, the clock signal CLK is transmitted to the column driving element  5210 , and the column driving element  5210  generates and transmits the first control signal DIO to the column driving element  5220 . Moreover, the column driving element  5210  generates and transmits the second control signal to the column driving element  5220  via the first data line D 00 , and generates and transmits the polarity control signal POL to the column driving element  5220  via the second data line D 01 . Accordingly, the column driving element  5220  receives and latches the digital image data DATAL allocated thereto during the transmitting interval TD of the digital image data.  
         [0079]     The column driving elements  5210  to  5260  receives and stores the digital image data allocated thereto by the above-described operation during the transmitting interval TD of the digital image data.  
         [0080]     The column driving elements  5210  to  5260  according to the embodiment of the present invention store the digital image data synchronized with both the rising and the falling edges of the clock signal CLK.  
         [0081]     When all of the digital image data allocated to the respective column driving elements  5210  to  5260  are stored thereto, the signal controller  5400  transmits the first control signal DIO in the logic state of low and the second control signal in the logic state of high via any one of the data lines D 00  to Dxx to each column driving element  5210  to  5260 .  
         [0082]     The logic circuit  5215  of the each column driving element  5210  to  5260  generates a load signal LOAD based on the first control signal DIO in the logic state of low and the second control signal in the logic state of high.  
         [0083]     Therefore, each column driving element  5210  to  5260  drives the data lines on the panel assembly  5100  based on the digital image data in response to the polarity control signal POL and the load signal LOAD such that the digital image data are displayed on the panel assembly  5100 . The polarity control signal POL are latched in the logic circuit  5215  until new polarity control signal is inputted thereto.  
         [0084]     As described above, each column driving element  5210  to  5260  drives the data lines on the panel assembly  5100  in response to the polarity control signal POL and the load signal LOAD such that the digital image data are displayed on the panel assembly  5100 . The signal controller  5400  and the respective column driving elements  5210  to  5260  share transmission regulation of signals including the first and the second control signals and the polarity control signal POL and information about buses (or data lines) for transmitting the signals.  
         [0085]      FIG. 9  is an operation timing chart of an FPD according to a second embodiment of the present invention.  
         [0086]     Referring to  FIG. 9 , the signal controller  5400  outputs many kinds of control signals with high frequencies in order to reduce the time that it takes to drive a horizontal line. In detail, during interval B, the signal controller  5400  outputs control signals having driving intervals such as at least an interval of the horizontal synchronization start signal STH (2 clocks), an interval of the first data (0.5 clock), an interval of the last data and the load signal (16 clocks), an interval of the load signal (28 clocks) and an interval of the load signal and the horizontal synchronization start signal STH (4 clocks). As described above, the driving time of a horizontal line requires a total of 50.5 clocks.  
         [0087]     Therefore, the signal controller  5400  outputs the control signals with higher than existing frequencies using its own phase locked loop (“PLL”) circuit, thereby assuring enough driving margin in displaying data of a horizontal line.  
         [0088]      FIG. 10  is an operation timing chart of an FPD according to the third embodiment of the present invention.  
         [0089]     Referring to  FIG. 10 , the signal controller  5400  generates another control signal such as CS. In detail, the signal controller  5400  recognizes the horizontal synchronization start signal STH when the control signal CS is in the logic state of low and outputs data based on an internal specification. After outputting the last data, the signal controller  5400  outputs an interval of the load (the LOAD interval) to the data lines at the moment when the control signal CS is in the logic state of high. The column driving elements  5210  to  5260  recognize the control signal CS and the interval of the load (the LOAD interval) and operate based thereon. Accordingly, the FPD  5000  assures enough driving margin in displaying THE data of a line.  
         [0090]      FIG. 11  is a detail block diagram of column driving element  5240  according to an alternate embodiment of the present invention. The other column driving elements  5210  to  5230 ,  5250  and  5260  can have the same configurations as that shown in  FIG. 11 .  
         [0091]     Referring to  FIG. 11 , the column driving element  5240  includes a data controller  5241 , a digital signal generator  5242 , a shift register  5243 , a data register  5244 , a data latch  5245 , a D/A converter  5246  and an output buffer  5247 . The column driving element  5240  substantially has the same configuration as a typical column driving element, and further includes the digital signal generator  5242  relative thereto.  
         [0092]     The digital signal generator  5242  transmits a horizontal synchronization start signal STH to the shift register  5243  responsive to the control signal CS generated from the signal controller  5400  and also transmits the load signal LOAD to the data latch  5245  and the polarity control signal POL to the D/A converter  5246 . According thereto, the signal controller  5400  drives the column driving element  5240  without generating the horizontal synchronization start signal STH, the polarity control signal POL and the load signal LOAD. As a result, since a plurality of signal lines for transmitting the signals STH, POL and LOAD are not required and the number of the signals decreases, power consumption and EMI decrease.  
         [0093]     As described above, the FPD according to embodiments of the present invention reduces the number of the buses connected between the signal controller and the column driving elements. Accordingly, the currents that the FPD consumes are reduced as much as the number of buses is reduced. Further, the EMI that the FPD generates is decreased as well.  
         [0094]     It is possible to design the thickness and/or the intervals of the lines efficiently according to the reduced number of buses. According thereto, in case of an FPD using a current driving scheme, it is possible to improve performance thereof due to reduction of resistance of the lines.  
         [0095]     Furthermore, it is possible to assure enough driving margin by driving the FPD responsive to a separate control signal with higher frequency.  
         [0096]     While the present invention has been described in detail with reference to the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the sprit and scope of the appended claims.