Patent Abstract:
An active matrix type display apparatus includes a display panel, a horizontal display driver and a controller. The horizontal display driver includes m (m is an integer larger than 1) horizontal driving sections to drive the display panel based on m display data sets in response to an output clock signal, respectively. The controller generates the output clock signal from an input clock signal, and carries out sampling of input data to produce display data for a horizontal line of the display panel. Also, the controller sequentially stores the display data and outputs the stored display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively.

Full Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an active matrix type display apparatus, in which a display panel can be efficiently driven. 
     2. Description of the Related Art 
     An active matrix display represented by a TFT liquid crystal display is typically composed of a display panel, a drive circuit for driving the display panel, and a controller for sending display data to the drive circuit. The operating frequency of the drive circuit is set to be lower than that of the controller. The controller reduces the transfer rate of the display data in accordance with the operating frequency of the driving circuit to transfer the display data to the drive circuit. 
     Technique for reducing the transfer rate of display data is disclosed in Japanese Laid Open Patent Applications (JP-A-Showa 64-13193, JP-A-Heisei 6-18844 and JP-A-Heisei 10-207434). 
     In the technique of Japanese Laid Open Patent Application (JP-A-Showa 64-13193), a data signal is divided into an odd-numbered data signal and an even-numbered data signal in order to drive an EL panel. The odd-numbered data signal and the even-numbered data signal are transferred in parallel with each other in synchronism with a half of the frequency of a reference clock signal so as to carry out the display control pixel by pixel. This technique does not consider the drive of an active matrix display such as a liquid crystal panel. The pixel-by-pixel drive control can be carried out under the presumption that the EL panel is driven. However, it is difficult to use the pixel-by-pixel drive control for the drive control of the active matrix type display apparatus. 
     In the technique of Japanese Laid Open Patent Application (JP-A-Heisei 6-18844), the bit of a display data signal is doubled. The doubled display data is transferred in synchronism with a half frequency of a reference clock signal. 
     In the technique of Japanese Laid Open Patent Application (JP-A-Heisei 10-207434), a source driver of a display panel is divided into a first half portion and a second half portion, and a line memory is similarly divided into two portions. Two data stored in the line memory are simultaneously supplied to the first and second portions of the source driver in synchronism with a half frequency of a reference clock signal. In this reference, display data required for the display of one line is stored in the line memory. After the completion of storing of the display data in the line memory, the display data for one line is simultaneously supplied to the display panel. In other words, this technology requires a line memory to have a capacity enough to store the display data for one line. 
     In this way, in the conventional active matrix type display apparatus, the operating clock of the drive circuit for driving the display panel can be set to be a half frequency of the reference clock signal. However, in order to perform frequency division of the clock, the arrangement of elements inevitably becomes complicated and a large capacity of memory is required. The large capacity of memory is equivalent to the memory having a capacity large enough to store display data for one line, for example, as in the technology disclosed in Japanese Laid Open Patent Application (JP-A-Heisei 10-207434). 
     SUMMARY OF THE INVENTION 
     Therefore, an object of the present invention is to provide an active matrix type display apparatus in which the storage capacity of a memory for temporarily storing display data can be significantly reduced. 
     Another object of the present invention is to provide an active matrix type display apparatus having good EMI characteristics. 
     In order to achieve an aspect of the present invention, an active matrix type display apparatus includes a display panel, a horizontal display driver and a controller. The horizontal display driver includes m (m is an integer larger than 1) horizontal driving sections to drive the display panel based on m display data sets in response to an output clock signal, respectively. The controller generates the output clock signal from an input clock signal, and carries out sampling of input data to produce display data for a horizontal line of the display panel. Also, the controller sequentially stores the display data and outputs the stored display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively. 
     Here, the controller may include a clock signal generating section which generates the output clock signal from the input clock signal. In this case, a frequency of the output clock signal is larger than that of the input clock signal. 
     Also, the output clock signal may include n (n is an integer larger than 1) clock signals, each of the m horizontal driving sections may include n driving sections, and the display data set may include n display data portions. At this time, the n driving sections drive the display panel based on the n display data portions of the display data set corresponding to the n driving sections in response to the n clock signals, respectively. In this case, n may be 2. In this case, the output clock signal may include first and second clock signals which are different in phase from each other by 180 degrees. 
     Also, the controller may include a dual port memory which sequentially stores the display data and outputs the stored display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively. In this case, it is desirable that the dual port memory operates in a first-in and first-out manner. 
     In order to achieve another aspect of the present invention, an active matrix type display apparatus includes a display panel, a horizontal display and a controller. The horizontal display driver includes m (m is an integer larger than 1) horizontal driving sections to drive the display panel based on m display data sets in response to an output clock signal, respectively. The controller generates the output clock signal from an input clock signal, and a frequency of the output clock signal is larger than that of the input clock signal. Also, the controller carries out sampling of input data to produce display data for a horizontal line of the display panel, and outputs the display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively. 
     Here, the output clock signal may include n (n is an integer larger than 1) clock signals, each of the m horizontal driving sections may include n driving sections, and the display data set may include n display data portions. At this time, the n driving sections drive the display panel based on the n display data portions of the display data set corresponding to the n driving sections in response to the n clock signals, respectively. In this case, n may be2. In this case, the output clock signal may include first and second clock signals which are different in phase from each other by 180 degrees. 
     Also, the controller may include a dual port memory which sequentially stores the display data and outputs the stored display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively. In this case, it is desirable that the dual port memory operates in a first-in and first-out manner. 
     In order to achieve still another aspect of the present invention, an active matrix type display apparatus includes a display panel, a horizontal display driver and a controller. The horizontal display driver set includes m (m is an integer larger than 1) horizontal driving sections to drive the display panel at different timings based on m display data sets in response to an output clock signal, respectively. The controller generates the output clock signal from an input clock signal, and a frequency of the output clock signal being larger than that of the input clock signal. Also, the controller carries out sampling of input data to produce display data for a horizontal line of the display panel, and outputs the display data to the m horizontal driving sections at the different timings in units of display data sets in response to the output clock signal, respectively. 
     Here, the output clock signal may include n (n is an integer larger than 1) clock signals, each of the m horizontal driving sections may include n driving sections, and the display data set may include n display data portions. At this time, the n driving sections drive the display panel based on the n display data portions of the display data set corresponding to the n driving sections in response to the n clock signals, respectively. In this case, n may be 2. In this case, the output clock signal may include first and second clock signals which are different in phase from each other by 180 degrees. 
     Also, the controller may include a dual port memory which sequentially stores the display data and outputs the stored display data to the m horizontal driving sections in units of display data sets in response to the output clock signal, respectively. In this case, it is desirable that the dual port memory operates in a first-in and first-out manner. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows the structure of an active matrix type display apparatus according to an embodiment of the present invention; 
     FIGS. 2A and 2B are timing charts showing an operation of a memory section of the present invention; and 
     FIGS. 3A to  3 D are timing charts showing another operation of the memory section of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, an active matrix type display apparatus of the present invention will be described below detail with reference to the attached drawings. 
     FIG. 1 shows the structure of an active matrix type display apparatus according to an embodiment of the present invention. The active matrix type display apparatus  1  shown in FIG. 1 is an example of a TFT liquid crystal display apparatus. The active matrix type display apparatus  1  is composed of a controller  2 , a drive circuit  3 , and a liquid crystal display panel  4 . The controller  2  is composed of a sampling section  21 , a memory section  22 , a clock (CLK) generating section  23 , and a data output section  24 . The drive circuit  3  is composed of first to fourth horizontal (H) drivers  101  to  104 . In this embodiment, each of the first to fourth horizontal drivers  101  to  104  is composed of a two-port driver having a port A and a port B. Of a group of input display data, odd-numbered input display data are supplied to the port A and even-numbered display data are supplied to the port B. 
     The sampling section  21  is composed of a logic circuits of flip-flop circuits and carries out the sampling of input display data DATA in synchronism with a reference clock CLK of the display apparatus  1 . The sampling section  21  outputs the sampled display data to the memory section  22 . The memory section  22  is composed of a dual port memory or first to fourth FIFO memories (not shown) for temporarily storing the input display data DATA sampled by the sampling section  21 . The memory section  22  carries out an input operation and an output operation in a first-in first-out (FIFO) manner. In this embodiment, the storage capacity of the memory section  22  is set to be less than the data quantity for one line of the display panel. 
     The clock generating section  23  is composed of a frequency divider for dividing the frequency of the reference clock CLK to ½. The clock generating section  23  generates a first frequency-division clock signal HCK-A and a second frequency-division clock signal HCK-B, which are different in phase from each other by 180 degree. The data output section  24  is composed of a gate circuit which transfers data outputted from the memory section  22  in synchronism with the first frequency-division clock signal HCK-A or the second frequency-division clock signal HCK-B. The data output section  24  outputs first output display data HDATA-A and second output display data HDATA-B. The first output display data HDATA-A is outputted from the memory section  22  in synchronism with the first frequency-division clock signal HCK-A. The second output display data HDATA-B is outputted from the memory section  22  in synchronism with the second frequency-division clock signal HCK-B. 
     The first frequency-division clock signal HCK-A and the first output display data HDATA-A are supplied to the first and third horizontal drivers  101  and  103  (odd-numbered horizontal drivers) of a first horizontal driver group. The second frequency-division clock signal HCK-B and the second output display data HDATA-B are supplied to the second and fourth horizontal drivers  102  and  104  (even-numbered horizontal drivers) of a second horizontal driver group. 
     The liquid crystal panel  4  is supposed to be composed of a display panel having 1280×1024 pixels. In this case, one line is composed of a row of 3840 dots (3840 color bits), if three dots for a red (R) dot, a green (G) dot, and a blue (B) dot are regarded as one pixel. When one horizontal driver drives 384 dots as a set of display data dots, ten horizontal drivers are provided. A first horizontal driver  101  drives a first group of 384 dots on the line, and the second horizontal driver  102  drives a second group of 384 dots on the line. Also, the third horizontal driver  103  drives a third group of 384 dots on the line, and the fourth horizontal driver  103  drives a fourth group of 384 dots on the line. Sequentially, groups of dots to be driven are allocated for fifth to tenth horizontal drivers (not shown). 
     Next, the operation of the active matrix type display apparatus of the present invention will be described below with reference to FIGS. 2A and 2B. In the following description, a set of display data is supposed to be for 128 pixels. 
     The sampling section  21  carries out the sampling of input display data in synchronism with the falling timing of the reference clock signal CLK shown in FIG.  2 A. Thus, the sampled display data are obtained as shown in FIG.  2 B. The sampled display data are supplied to the memory section  22 . In this case, the first 256 display data are supplied to the first FIFO memory of the memory section  22 , and the second 256 display data are supplied to the second FIFO memory of the memory section  22 . Also, the third 256 display data are supplied to the third FIFO memory of the memory section  22 , and the fourth 256 display data are supplied to the fourth FIFO memory of the memory section  22 . Then, the fifth 256 display data are supplied to the first FIFO memory of the memory section  22  again. 
     More specifically, when the sampled display data DATA are composed of first data D 1  to 128th data D 128 , the first port data A is composed of the first data D 1 , the third data D 3 , . . . , and the 127th data D 127 . In addition, the second port data B is composed of the second data D 2 , the fourth data D 4 , . . . , and the 128th data D 128 . The first FIFO memory of the memory section  22  stores the first data D 1  to the 128th data D 128  in sequence. 
     When the sampled display data DATA are composed of a 129th data D 129  to a 256th data D 256 , the first port data A is composed of the 129th data D 129 , the 131st data D 131 , . . . , and the 255th data D 255 . The second port data B is composed of the 130th data D 130 , the 132nd data D 132 , . . . , and the 256th data D 256 . The second FIFO memory of the memory section  22  stores the first data D 129  to the 256th data D 256  in sequence. 
     The sampling section  21  continues to carry out the sampling of the input display data in synchronism with the falling timing of the reference clock signal CLK. After the sampling of the 256th data D 256 , the sampling section  21  outputs the 257th data D 257  and subsequent data. At this time, the sampled display data are supplied to the third and fourth FIFO memories of the memory section  22  sequentially. 
     After the sampling section  21  carries out the sampling of the 3840th data D 3840 , the whole display data for one line of the liquid crystal display panel  4  is provided. Thus, an image for one line corresponding to the input display data can be displayed on the display panel  4 . 
     Next, the output operation of the display data from the memory section  22  will be described below with reference to FIGS. 3A to  3 D. 
     When the third FIFO memory of the memory section  22  stores the 257th data D 257 , the first FIFO memory of the memory section  22  outputs the first data D 1  to the data output section  24 , as shown in FIG.  3 C. When the third FIFO memory of the memory section  22  stores the 258th data D 258 , the second FIFO memory of the memory section  22  outputs the 129th data D 129  to the data output section  22 , as shown in FIG.  3 D. When the third FIFO memory of the memory section  22  stores the 259th data D 259 , the first FIFO memory of the memory section  24  outputs the second data D 2  to the data output section  24 , as shown in FIG.  3 C. When the third FIFO memory of the memory section  22  stores the 260th data D 260 , the second FIFO memory of the memory section  22  outputs the 130th data D 130  to the data output section  24 , as shown in FIG.  3 D. 
     The first and third FIFO memories of the memory section  22  carry out the output operation of the display data to the data output section  24  in synchronism with the rising timing of the first frequency-division clock signal HCK-A shown in FIG.  3 A. Thus, the first display data HDATA-A composed of the first port data and the second port data are supplied to the first and third horizontal drivers  101  and  103 , respectively, as shown in FIG.  3 C. For example, the first port data are composed of the first data D 1 , the third data D 3 , and the fifth data D 5  to the 127th data D 127 , and the second port data are composed of the second data D 2 , the fourth data D 4 , and the sixth data D 6  to the 128th data D 128 . 
     The second and fourth FIFO memories of the memory section  22  carry out the output operation of the display data to the data output section  24  in synchronism with the rising timing of the second frequency-division clock signal HCK-B shown in FIG.  3 B. Thus, the second display data HDATA-B composed of the first port data and the second port data are supplied to the second and fourth horizontal drivers  102  and  104 , respectively, as shown in FIG.  3 D. For example, the first port data are composed of the 129th data D 129 , the 131st data D 131 , and the 133rd data D 133  to the 383rd data D 383 , and the second port data are composed of the 130th data D 130 , the 132nd data D 132 , and the 134th data D 134  to the 512th data D 512 . 
     The data output section  24  outputs the first port data composed of the first data D 1 , the third data D 3 , and the fifth data D 5  to the 127th data D 127  to the port A of the first horizontal driver  101 . The first horizontal driver  101  receives the first port data in synchronism with the first frequency-division clock signal HCK-A. Also, the data output section  24  outputs the second port data composed of the second data D 2 , the fourth data D 4 , and the sixth data D 6  to the 128th data D 128  to the port B of the first horizontal driver  101 . The first horizontal driver  101  receives the second port data in synchronism with the first frequency-division clock signal HCK-A. 
     The data output section  24  outputs the first port data composed of the 129th data D 129 , the 131st data D 131 , and the 133rd data D 133  to the 255th data D 255  to the port A of the second horizontal driver  102 . The second horizontal driver  102  receives the first port data in synchronism with the second frequency-division clock signal HCK-B. Also, the data output section  24  outputs the second port data composed of the 130th data D 130 , the 132nd data D 132 , and the 134th data D 134  to the 256th data D 256  to the port B of the second horizontal driver  102 . The second horizontal driver  102  receives the second port data in synchronism with the second frequency-division clock signal HCK-B. 
     After the completion of outputting of the 256th data D 256 , the data output section  24  receives the 257th data D 257  and subsequent data from the third and fourth FIFO memories of the memory section  22  to output to the third and fourth horizontal drivers  103  and  104 . 
     As described above, the display apparatus  1  repeats the same processing while driving the two horizontal drivers as one unit during the same output cycle. The controller  2  can carry out the processing without causing any trouble in the storage of new data, if the memory section  22  having a capacity necessary to drive the two horizontal drivers is provided. 
     Since there is a phase difference of 180 degrees between the first frequency-division clock signal HCK-A and the second frequency-division clock signal HCK-B, the output timing of the first display data HDATA-A differs from the output timing of the second display data HDATA-B. The phase difference or timing difference allows the number of concurrently changing signals to be decreased. The decrease in the number of the concurrently changing signals leads to reduction in the occurrence of EMI. 
     The present invention is not limited to the above embodiments. For example, when the timings of input and output to and from the memory section  22  are more finely controlled, it is possible to reduce the capacity of the memory section  22  to the capacity necessary to drive one horizontal driver. Moreover, the number of horizontal drivers may be determined depending on the ratio of frequency division of the clock signal generating section  23  and the number of pixels of the liquid crystal panel. 
     In the active matrix type display apparatus according to the present invention, the storage region of the memory can be used with efficiency. As a result, the capacity of the memory can be significantly reduced, as compared with the conventional example in which the memory capacity necessary to store display data for one line is required. 
     Also, in the active matrix display according to the present invention, there is a difference between the timings of transferring data to a pair of horizontal drivers. Thus, the number of signals changing at one time can be reduced. As a result, the occurrence of EMI can be reduced.

Technology Classification (CPC): 6