Abstract:
A data driver has several gamma-voltage generating circuits and several driving channels. The gamma-voltage generating circuits are used to process gamma-voltages of different colors. Each two groups of the driving channels are correspondingly coupled with the gamma-voltage generating circuit that generates a single color and is separately disposed at either side of the corresponding gamma generating circuit for outputting the gamma-voltages of the same color to a display panel.

Description:
RELATED APPLICATIONS  
       [0001]     The present application is based on, and claims priority from, Taiwan Application Serial Number 95100638, filed Jan. 6, 2006, the disclosure of which is hereby incorporated by reference herein in its entirety.  
       BACKGROUND  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a data driver. More particularly, the present invention relates to a data driver used for a flat panel display.  
         [0004]     2. Description of Related Art  
         [0005]     With the rapid development in technology, flat panel displays (FPD) with their advantages of high image quality, compact size, light weight, low driving voltage and low power consumption have become very popular for incorporation into electrical devices and have become the mainstream display apparatus. For example, the FPD can be introduced into the portable TV, mobile phone, video recorder, computer monitor, and many other kinds of consumer electronics.  
         [0006]     The FPD is driven by several source drivers (i.e. data drivers) that can transform the digital data (image data) into analog voltages for a display unit of the FPD. For example, the gamma curve relationship between the light passing through the display units and the analog voltages applied on the display units is nonlinear. Therefore, data drivers have gamma-voltage generating circuits to correct the analog voltages applied on the display unit. The gamma-voltage generating circuits can make the analog voltages applied on the display unit correspond to the variation of gamma curve when the digital data is transformed into analog voltages.  
         [0007]      FIG. 1  is a functional block diagram depicting a traditional data driver. The traditional data driver  100  has several gamma-voltage generating circuits  130 ,  150  and  170 , two driving channel sets  140  and  160 , and a shift register  134 . The shift register  134  is used to save an input data temporarily, and the driving channels in the driving channel sets  140  and  160  get the gamma-voltage generated by the gamma-voltage generating circuits according to the input data. The gamma-voltage generating circuits  130 ,  150  and  170  are arranged to generate several gamma-voltages of different colors individually; for example, the gamma-voltage generating circuit  130  is arranged to generate gamma-voltages of red color, the gamma-voltage generating circuit  150  is arranged to generate gamma-voltages of green color, and the gamma-voltage generating circuit  170  is arranged to generate gamma-voltages of blue color.  
         [0008]     The driving channel sets  140  and  160  have several driving channels  131 ,  133 ,  151 ,  153 ,  171  and  173  to transmit gamma-voltages of different colors. Each driving channel has at least one digital-to-analog converter (not shown) connected to the gamma-voltage generating circuit and the shift register. The digital-to-analog converter gets the corresponding gamma-voltage generated by the gamma-voltage generating circuit according to the input data saved in the shift register  134  temporarily. One end of each driving channel is correspondingly connected to the gamma-voltage generating circuit of different colors individually; for example, the driving channels  131 ,  133  are correspondingly connected to the gamma-voltage generating circuit  130 , the driving channels  151 ,  153  are correspondingly connected to the gamma-voltage generating circuit  150 , and the driving channels  171 ,  173  are correspondingly connected to the gamma-voltage generating circuit  170 . Furthermore, the other end of each driving channel is correspondingly connected to the data line of different colors of the display panel.  
         [0009]     For example, the driving channels  131 ,  151  and  171  are correspondingly used for the data lines  191 ,  192  and  193  individually, and driving channels  133 ,  153  and  173  are correspondingly used for the data lines  194 ,  195  and  196  individually. The driving channel  131  is correspondingly connected to the gamma-voltage generating circuit  130  of red color (the connecting wire between the driving channel  131  and the gamma-voltage generating circuit  130  is not shown), and is correspondingly connected to the data line  191  of red color in the display panel  190 . The driving channel  151  is correspondingly connected to the gamma-voltage generating circuit  150  of green color, and is correspondingly connected to the data line  192  of green color in the display panel  190 . The driving channel  153  is correspondingly connected to the gamma-voltage generating circuit  170  of blue color, and is correspondingly connected to the data line  193  of blue color in the display panel  190 . By the same way, the ends of driving channels  133 ,  153  and  173  are correspondingly connected to the gamma-voltage generating circuit  130  of red color, the gamma-voltage generating circuit  150  of green color and the gamma-voltage generating circuit  170  of blue color individually. The other ends of driving channels  133 ,  153  and  173  are correspondingly connected to the data line  194  of red color, the data line  195  of green color and the data line  196  of blue color in the display panel  190 .  
         [0010]     Typically, the gamma-voltage generating circuit is used to generate several gamma-voltages for the digital-to-analog converter of the driving channel described previously. The gamma-voltage generating circuit is composed of resistor chains, and the gamma-voltage can be obtained from the node between resistors. In the traditional circuit layout, the gamma-voltage generating circuit  130 ,  150  and  170  are neighbors and configured at the center of the data driver  100 . The driving channel sets  140  and  160  are configured at the lateral sides of the centralized gamma-voltage generating circuits  130 ,  150  and  170 . This kind of circuit layout needs sufficient space to transmit the gamma-voltages of different colors to the corresponding driving channels. For example, the driving channel  151  used to transmit the gamma-voltages of green color has to stride over the gamma-voltage generating circuit  130  for connecting to the corresponding gamma-voltage generating circuit  150 . Therefore, the circuit layout of the gamma-voltage generating circuit  130  increases the length in the direction of arrow  101  to configure the connection between the driving channel  151  and the gamma-voltage generating circuit  150 . By the same way, the driving channel  153  used to transmit the gamma-voltages for green color has to stride over the gamma-voltage generating circuits  170  for connecting to the corresponding gamma-voltage generating circuits  150 . Therefore, the circuit layout of the gamma-voltage generating circuits  170  increases the length in the direction of arrow  101  to configure the connection between the driving channel  153  and the gamma-voltage generating circuit  150 . Otherwise, the farther the distance between the gamma-voltage generating circuit and the driving channel (such as the driving channels  131  and  173  at the far end of the lateral sides), the easier the problems of voltages decay and time delay occur. Therefore, a data driver is needed with a new circuit layout to reduce the chip size and reduce the problems of voltage decay and time delay.  
       SUMMARY  
       [0011]     It is therefore an aspect of the present invention to provide a data driver with new circuit layout, which has smaller chip size, more stable voltage and more precise timing.  
         [0012]     It is therefore another aspect of the present invention to provide a modulated data driver, of which each module has one gamma-voltage generating circuit and two driving channel sets to generate gamma-voltages of a single color.  
         [0013]     According to one preferred embodiment of the present invention, the data driver comprises a plurality of gamma-voltage generating circuits and a plurality of driving channel sets. The gamma-voltage generating circuits are arranged to generate a plurality of gamma-voltages of different colors. Each two driving channel sets are connected to the corresponding gamma-voltage generating circuit of a single color for outputting the gamma-voltages of a the single color to the display panel, and each two driving channel sets are configured at two sides of the corresponding gamma-voltage generating circuit separately, wherein the neighboring gamma-voltage generating circuits that generate the gamma-voltages of different colors are separated by two connecting driving channel sets of different colors.  
         [0014]     It is to be understood that both the foregoing general description and the following detailed description are examples and are intended to provide further explanation of the invention as claimed. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     These and other features, aspects, and advantages of the present invention will become better understood with regard to the following description, appended claims, and accompanying drawings where:  
         [0016]      FIG. 1  is a functional block diagram depicting a traditional data driver.  
         [0017]      FIG. 2  is a functional block diagram depicting one preferred embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0018]     Reference will now be made in detail to the present preferred embodiments of the invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers are used in the drawings and the description to refer to the same or like parts.  
         [0019]     This invention offers a data driver with new circuit layout and uses several driving channel sets to separate the gamma-voltage generating circuits of different colors. Therefore, the chip size is decreased and the problems of voltages decay and time delay are reduced.  
         [0020]      FIG. 2  is a functional block diagram depicting one preferred embodiment of the present invention. The data driver  200  of this preferred embodiment has a plurality of gamma-voltage generating circuits  230 ,  250 ,  270 , and a plurality of driving channel sets  235 ,  238 ,  255 ,  258 ,  275 ,  278 . The gamma-voltage generating circuits  230 ,  250  and  270  are arranged to generate a plurality of gamma-voltages of different colors. For example, the gamma-voltage generating circuit  230  is arranged to generate the gamma-voltages of red color, the gamma-voltage generating circuit  250  is arranged to generate the gamma-voltages of green color, and the gamma-voltage generating circuit  270  is arranged to generate the gamma-voltages of blue color.  
         [0021]     Each two driving channel sets are connected to the corresponding gamma-voltage generating circuit of a single color for outputting the gamma-voltages of a the single color to the display panel  290 , and each two driving channel sets are configured at two sides of the corresponding gamma-voltage generating circuit separately, wherein the neighboring gamma-voltage generating circuits that generate the gamma-voltages of different colors are separated by two connecting driving channel sets of different colors.  
         [0022]     The driving channel set in this embodiment has several driving channels used to output the gamma-voltages of the single color. For example, the driving channels of driving channel sets  235  and  238  are all used to transmit the gamma-voltages of red color generated by the gamma-voltage generating circuit  230 . The driving channels of driving channel sets  255  and  258  are all used to transmit the gamma-voltages of green color generated by the gamma-voltage generating circuit  250 . The driving channels of driving channel sets  275  and  278  are all used to transmit the gamma-voltages of blue color generated by the gamma-voltage generating circuit  270 . Each driving channel has at least one digital-to-analog converter (not shown) connected to the gamma-voltage generating circuit and the shift register. The digital-to-analog converter gets the corresponding gamma-voltage generated by the gamma-voltage generating circuit according to the input data saved in the shift register temporarily. In the traditional data driver  100  of  FIG. 1 , the driving channels used to transmit the gamma-voltages of different colors are configured in sequence. For example, the driving channels  131 ,  151  and  171  are used to transmit the gamma-voltages of red, green and blue colors in sequence. Therefore, the improvement of this preferred embodiment over the present invention is that each two driving channel sets used to transmit the gamma-voltages of same color are configured at two sides of the corresponding gamma-voltage generating circuit to form a module. The module is used to output the gamma-voltages with various gray-levels of the single color to shorten the conducting path and improve the problems of voltage decay and time delay. For example, compared with  FIG. 1 , the connection length between driving channel  231  and the gamma-voltage generating circuits  230  in  FIG. 2  is only about one-third of the connection length between driving channel  131  and the gamma-voltage generating circuits  130  of the traditional data driver  100  in  FIG. 1 ; and this configuration can reduce the problems of voltage decay and time delay.  
         [0023]     The gamma-voltage generating circuits  230 ,  250  and  270  are used to generate the gamma-voltages for the digital-to-analog converters of the driving channel sets  235 ,  238 ,  255 ,  258 ,  275  and  278  described previously. The gamma-voltage generating circuits are usually designed as voltage dividers but are not limited thereby. For example, the gamma-voltage generating circuit is composed of resistor chains, and the gamma-voltage can be obtained from the nodes between resistors.  
         [0024]     Furthermore, two driving channel sets used to transmit the gamma-voltages of the single color are configured symmetrically at and adjacent to the gamma-voltage generating circuit that is arranged to generate the gamma-voltages of the single color. For example, the driving channel sets  235  and  238  used to transmit the gamma-voltages of red color are configured symmetrically at and adjacent to the two sides of the gamma-voltage generating circuit  230 , and the quantity of driving channels of driving channel sets  235  and  238  are about equal. Therefore, the power loadings of two sides of the gamma-voltage generating circuit are balanced, and the longest conducting path is shortened.  
         [0025]     Otherwise, from  FIG. 2 , in the data driver  200  of this preferred embodiment, the neighboring gamma-voltage generating circuits that generate the gamma-voltages of different colors are separated by two connecting driving channel sets of different colors. For example, the gamma-voltage generating circuits  230  of red color and gamma-voltage generating circuits  250  of green color are separated by the driving channel sets  238  of red color and the driving channel sets  255  of green color.  
         [0026]     Each driving channel set has a plurality of driving channels connected to data lines of the display panel separately. For example, in the display panel  290 , the data line  291  is a red-color data line, the data line  292  is a green-color data line, and the data line  293  is a blue-color data line. The driving channel  231  of red color connects to the data line  291 , the driving channel  251  of green color connects to the data line  292 , and the driving channel  271  of blue color connects to the data line  293 .  
         [0027]     The data driver  200  of this preferred embodiment can be applied to the display panel that has to correct the analog voltages of display colors, such as in liquid crystal display panels, plasma display panels, organic light-emitting diode display panels and low temperature polysilicon thin film transistor display panels. Otherwise, the data driver of this preferred embodiment is used to correct three fundamental colors (red, green and blue) of a display panel. Even if the display colors of the display panel are not only three fundamental colors (such as red, green, blue and yellow), the data driver of this preferred embodiment can still be applied.  
         [0028]     The data driver  200  of this preferred embodiment further comprises a plurality of sets of shift registers  234 ,  254  and  274  connected to the driving channels, wherein the shift registers are arranged to save an input data temporally, and the driving channels get the gamma-voltages generated by the gamma-voltage generating circuits according to the input data. For example, the shift register  234  connects to the driving channel sets  235  and  238 , and the driving channels get the gamma-voltages generated by the gamma-voltage generating circuit  230  according to the input data.  
         [0029]     In the circuit layout of this preferred embodiment, the different color connections between the driving channels and the corresponding gamma-voltage generating circuits are independent. Therefore, space for configuring the connection between the driving channels and the corresponding gamma-voltage generating circuits does not need to be reserved. Compared with  FIG. 1 , the length along the direction of arrow  201  is only about one-third of the length along the direction of arrow  101  in  FIG. 1 . This configuration can make the chip size smaller and decrease the cost of this chip so as to improve productivity.  
         [0030]     The data driver of this embodiment is modular and the designer can design one kind of circuit layout for a gamma-voltage generating circuit by one gamma curve of one color. This kind of circuit layout can be duplicated for other colors. Therefore, this kind of circuit layout can save the time of design and wire routing and is convenient and flexible for testing and design change.  
         [0031]     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the present invention without departing from the scope or spirit of the invention. In view of the foregoing, it is intended that the present invention cover modifications and variations of this invention provided they fall within the scope of the following claims and their equivalents.