Abstract:
The present invention discloses a driving system and the method thereof for a display system, and particularly for the display system with a bi-stable display. The driving system of the present invention has the advantage of requiring less memory capacity than that of traditional driving systems. The driving system of the present invention reads one frame data at one time and will clear the current frame before displaying a new frame. Owing to the current frame being cleared before a new frame being updated, the driving system needs not to record the difference of gray level between the two frames and thereby reduces the requirement of memory capacity.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This present application claims priority to TAIWAN Patent Application Serial Number 099139433, filed on Nov. 16, 2010, which are herein incorporated by reference. 
       TECHNICAL FIELD 
       [0002]    The present invention relates to a display driving system, and particularly to a driving system and a driving method for an electronic paper display system. 
       BACKGROUND OF THE RELATED ART 
       [0003]    Nowadays, electronic papers are more and more popular. With respect to the traditional electronic paper (hereinafter called E-paper), as shown in  FIG. 1 , an electronic paper includes a memory system  111   112 , a waveform output unit  120  and a bi-stable display  130 . In general, when traditional E-papers  10  would like to update a new frame, they need to compare the data of the new frame with the current frame. Therefore, the prior art of an E-paper  10  requires larger memory capacity to store at least two frame data, the current and the new frame. 
         [0004]    For one example, as shown in  FIG. 1 , the traditional display driving system for E-papers includes memory_ 1   111  to store the current frame data and memory_ 2   112  to store the new frame data. The waveform output unit  120  reads the data from both memory_ 1   111  and memory_ 2   112  and compares the difference of the gray level of each pixel between two frames. According to a look-up table (LUT)  122 , in which each of different output conditions is mapped onto each of different gray levels, the waveform output unit  120  will send out the respective control signal for each pixel to show a new frame on a bi-stable display  130 . 
         [0005]    Given that a frame has N gray levels, the waveform output unit  120  needs to store N×N output conditions in the look-up table (LUT), as shown in  FIG. 2 . While the traditional E-paper would like to show a new frame, the comparison unit  121 , as shown in  FIG. 1 , will compare the gray level of each pixel between the current frame and the new frame and map each of the compared results onto each of output conditions in the look-up table (LUT)  122 . After that the waveform output unit  120  transmits the respective control signal to each pixel in the bi-stable display  130  in accordance with the output condition of each pixel in the look-up table (LUT)  122 . Hence, provided that the number of gray level in a frame is doubled (i.e., 2N), the storage space in the waveform output unit  120  will become 4 times because the look-up table (LUT)  122  needs to store 2N×2N output conditions. Obviously, the storage space in the waveform output unit  120 , i.e., memory cost, will become unacceptable huge if the resolution of an E-paper increase rapidly due to the market demand. 
         [0006]    Therefore, the prior art of an E-paper  10  not only needs larger memory to store at least two frame data, but requires larger storage space to store N×N output conditions in the look-up table (LUT)  122 . Nevertheless, the driving system of the present invention needs to store no more than one frame data and to keep lesser output conditions (i.e., 2N), and consequently the memory capacity of the driving system of the present invention can be reduced tremendously. 
       SUMMARY 
       [0007]    The present invention discloses a driving system for display, and the system needs less memory capacity than the prior art. The driving system of the present invention includes: A frame data input unit for inputting a frame data, a storage device storing the frame data in sequence from the frame data input unit, a waveform generation unit receiving the frame date from the storage device, wherein the waveform generation unit further comprises a look-up table (LUT) selector and a LUT output unit. After receiving the frame data from the storage device, the waveform generation unit, via the LUT selector, informs the LUT output unit of outputting a control signal. The driving system further includes a display unit receiving the control signal from the LUT output unit and displaying a frame corresponding to the frame data on the display unit. 
         [0008]    The storage device includes the storage device include DRAM, SRAM, Flash memory, and the other storage devices being capable of reading the frame data successively and/or randomly from the frame data input unit. One of the improvements of the present invention is that the capacity of the storage device can be reduced to a critical capacity less than the size of storing two frame data, even not more than the size of storing one frame in a good design. 
         [0009]    The LUT output unit in the waveform generation unit further includes a displaying LUT output device and a clearing LUT output device, wherein the displaying LUT output device and the clearing LUT output device are electrically coupled to the display unit and output the control signal corresponding to the frame data to the display unit. The displaying LUT output device sends out the control signal to show a frame corresponding to the frame data on the display unit, and the clearing LUT output device sends out the control signal to clear a current frame on the display unit. In the condition that a frame with N gray levels, the displaying LUT output device only needs to store N displaying output conditions and the clearing LUT output device only needs to store N clearing output conditions. 
         [0010]    In one embodiment, the display unit of the present invention includes a symmetric bi-stable display, which substantially has symmetric characteristic, so that the LUT output unit is replaced by a flip flop device and the LUT selector is simplified to be a LUT unit. Hence, the waveform generation unit includes a LUT unit and a flip flop device. The flip flop device can output a clearing control signal or a displaying control signal to clear or show the frame, respectively, on the symmetric bi-stable display. Besides, the displaying control signal and the clearing control signal are substantially symmetric and complementary. Both the displaying control signal and the clearing control signal include a DC voltage or a switching waveform with equivalent DC voltage. The duration of an active state of the DC voltage or the equivalent DC voltage is manipulated to control the gray levels of the display. In the condition that a frame with N gray levels, the LUT unit only needs to store N output conditions. 
         [0011]    In one embodiment, a position DC voltage or a positive equivalent DC voltage (hereinafter called a first voltage) and a negative DC voltage or a negative equivalent DC voltage (hereinafter called a second voltage) are employed to control the gray levels. The longer duration of the first voltage is, the more darkness of the display unit shows, and the shorter duration of the first voltage is, the more brightness of the display unit shows. On the contrary, the longer duration of the second voltage is, the more brightness of the display unit shows, and the shorter duration of the first voltage is, the more darkness of the display unit shows. The relationship between the voltage vales and the darkness or brightness of the display depends on the characteristic of the display. In another embodiment, it can be that the longer duration of the first voltage is, the more brightness of the display unit shows, and whereas the longer duration of the second voltage is, the more darkness of the display unit shows 
         [0012]    The present invention further discloses a method of driving a display. The method applied on the above-mentioned driving system includes: When the display unit would like to update a new frame, the waveform generation unit first reads the frame data of a current frame from the storage device. Thereupon the waveform generation unit, via the LUT selector, informs the LUT output unit of outputting the control signal to clear the current frame on the display unit. After reading a new frame data from the frame data input unit, the storage device sends the new frame data to the waveform generation unit. The LUT selector informs the LUT output unit of sending the control signal to update the new frame on the display unit. 
         [0013]    In one embodiment, the method applied on the above-mentioned driving system includes: When the symmetric bi-stable display would like to update a new frame, the waveform generation unit first reads the frame data of a current frame from the storage device. Thereupon the LUT unit informs the flip flop device of outputting the control signal to clear the current frame on the symmetric bi-stable display. After reading a new frame data from the frame data input unit, the storage device sends the new frame data to the waveform generation unit. The LUT unit informs the flip flop device of sending the control signal to update the new frame on the symmetric bi-stable display. 
         [0014]    The storage device in the embodiment can be reduced to a critical capacity less than the size of storing two frame data, even not more than the size of storing one frame in a well design. Furthermore, provide that a frame with N gray levels, the output conditions in the LUT unit is reduce to N instead of 2N. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]    The above objects, and other features and advantages of the present invention will become more apparent after reading the following detailed description when taken in conjunction with the drawings, in which: 
           [0016]      FIG. 1  illustrates the prior art of driving system for E-paper. 
           [0017]      FIG. 2  illustrates the prior art will need to store N×N output conditions, if a frame has N gray levels. 
           [0018]      FIG. 3  illustrates the driving system architecture of the present invention. 
           [0019]      FIG. 4(   a ) illustrates the driving system of present invention only needs to store N clearing output conditions, if a frame has N gray levels. 
           [0020]      FIG. 4(   b ) illustrates the driving system of present invention only needs to store N displaying output conditions, if a frame has N gray levels. 
           [0021]      FIG. 5(   a ) illustrates the displaying control signals for a bi-stable display. 
           [0022]      FIG. 5(   b ) illustrates the clearing control signals for a bi-stable display. 
           [0023]      FIG. 6  illustrates switching waveforms used to be output control signals. 
           [0024]      FIG. 7  illustrates a driving system architecture of the present invention includes a symmetric bi-stable display. 
       
    
    
     DETAILED DESCRIPTION 
       [0025]    The present invention will be described in detail by using the following embodiments and it will be recognized that those descriptions and examples of embodiments are used to illustrate but not to limit the claims of the present invention. Hence, other than the embodiments described in the following, the present invention may be applied to the other substantially equivalent embodiments. 
         [0026]    The present invention discloses a driving system for display, and particularly for an electronic paper (E-paper), hereinafter called E-paper, system or the other display systems containing bi-stable display. As shown in  FIG. 3 , the driving system of the present invention includes a frame data input  200  used to input frame data, a storage device  210  used to the store frame data from the frame data input  200 . In one embodiment, the storage device  210  includes dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, hard disk, or the other storage devices which can be stored/read data successively and randomly. The storage device  210  can read frame data from the frame data input  200  successively or randomly, and certainly the larger the size of the storage device  210  has, the more frame data can be stored. Nevertheless, one of improvements of the present invention is that the required memory size of the present invention is much less than that of the prior art. In one embodiment, the memory capacity of the driving system  20  of the present invention can be reduced to a critical size to store the data of less than two frames. In one embodiment, due to a well design, the critical size of the memory can be reduced to store only one or no more than one frame data. 
         [0027]    As shown in  FIG. 3 , a waveform generation unit  220 , which includes a look-up table (LUT), hereinafter called LUT, selector  221  and a LUT output unit  222 , reads frame data from a storage device  210 , and then outputs control signals to a bi-stable display  230  after the comparison processing of frame data is accomplished internally. 
         [0028]    In one embodiment, the LUT output unit  222  includes a displaying LUT output device  222 _ 1  and a clearing LUT output device  222 _ 2 . The LUT output unit  222  issues displaying control signals from the displaying LUT output device  222 _ 1  to the bi-stable display  230  for updating a new frame or issues clearing control signals from the clearing LUT output device  222 _ 2  to the bi-stable display  230  for clearing a current frame. 
         [0029]    In one embodiment, provided that the bi-stable display  230  is showing a current frame, wherein the data of the current frame is kept in the storage device  210  concurrently. Provided that the driving system  20  would like to update a new frame, before the storage device  210  reads the new frame data from the frame data input  200 , the waveform generation unit  220  first reads the current frame data from the storage device  210  and the LUT selector  221  selects the clearing LUT output device  222 _ 2  to send out clear signals to clear the current frame on the bi-stable display  230  after the right clearing output condition generated from the clearing LUT output device  222 _ 2  is selected. After that the new frame data is read from the frame data input  200  into the storage device  210  and is sent to the waveform generation unit  220 . In the meantime, the LUT selector  221  selects the displaying LUT output device  222 _ 1  to send out display signals to update the new frame on the bi-stable display  230  after the right displaying output condition generated from the displaying LUT output device  222 _ 1  is selected. 
         [0030]    In one embodiment, given that the current frame has N gray levels, it will need to store N clearing output conditions (Cond. c(1) ˜Cond. c(N) ) in the clearing LUT output device  222 _ 2 , as exemplified in  FIG. 4(   a ). Similarly, as exemplified in  FIG. 4(   b ), provided that a new frame has N gray levels as well, it only needs N displaying output conditions (Cond. n(1) ˜Cond. n(N) ), which map onto respective displaying control signals to the bi-stable display  230 , being stored in the displaying LUT output device  222 _ 1  because the current frame is cleared already. Accordingly, the LUT output unit  222  only needs to keep 2N output conditions so that not only the storage space in the waveform generation unit can save with a large amount but the operation speed of the waveform generation unit  220  can increase because of the output conditions in the LUT output unit  222  being decreased with a large amount. The storage space for storing 2N output conditions is not limited to be in the LUT output unit  222 . In one embodiment, the above-mentioned storage space can be in the LUT selector  221  or be distributed in the waveform generation unit  220 . 
         [0031]    The bi-stable display  230  used in the driving system  20  has two stable states and has the characteristics that if the longer duration of a first voltage is applied to the bi-stable display  230 , the more darkness the bi-stable display  230  shows and, on the contrary, if the longer duration of a second voltage is applied, the more brightness the bi-stable display  230  shows. The first voltage and the second voltage are symmetrical voltage with respect to a reference voltage. For one example, provided that the reference voltage is 0V and the first voltage is 5V, the second voltage should be −5V. 
         [0032]    In one embodiment, as shown in  FIG. 5 , the first and the second voltages are the positive voltage (V pos ) and the negative voltage (V neg ), respectively, and the displaying LUT output device  222 _ 1  generates displaying control signals  41  to control gray levels of the bi-stable display  230 . As shown in  FIG. 5  ( a ), the control signal G C1  with the shortest duration of positive state  42  causes the bi-stable display  230  to exhibit the most brightness, while the control signal G CN  with the longest duration of positive state  42  causes the bi-stable display  230  to exhibit the most darkness. Accordingly, the duration of the positive state  42  between the shortest and the longest can manipulate the gray level of the bi-stable display  230 . 
         [0033]    The clearing LUT output device  222 _ 2  generates clearing control signals  51 , which act like the inverse signal of displaying control signals  41 , to control gray levels of the bi-stable display  230 . As shown in  FIG. 5  ( b ), the control signal G n1  with the shortest duration of negative state  52  causes the bi-stable display  230  to exhibit the most darkness, while the control signal G nN  with the longest duration of negative state  52  causes the bi-stable display  230  to exhibit the most brightness. Accordingly, the duration of the positive state  52  between the shortest and the longest can manipulate the gray level of bi-stable display  230 . In other words, in order to erase the current frame on the bi-stable display  230 , clearing control signals  51  (G nx(x=1, 2 . . . n)  generated by the clearing LUT output device  222 _ 2  are similar to the complementary signals of displaying control signals  41  generated by the displaying LUT output device  222 _ 1 . 
         [0034]    The positive state  42  of displaying control signals  41  and the negative state  52  of and clearing control signals  51  are not limited to be DC voltages. In one embodiment, as shown in  FIG. 6 , displaying and clearing control signals can behave like the switching waveform_ 1   61  changing voltages up and down, or the switching waveform_ 2   62  changing voltages within three levels. However, the equivalent DC voltage of either the switching waveform_ 1   61  or the switching waveform_ 2   62  can also control the gray level of a bi-stable display  230 . 
         [0035]    In one embodiment, given that a bi-stable display owns substantially symmetric characteristic, called symmetric bi-stable display, the displaying LUT output device  222 _ 1  and the clearing LUT output device  222 _ 2  are substantially symmetrical and complementary. Therefore, the driving system of the present invention can be modified to the architecture as shown as in  FIG. 7 . The waveform generation unit  220  as shown as in  FIG. 3  can be altered to be the waveform generation unit  720 , shown in  FIG. 7 , which only contains a LUT unit  721  and a flip flop device  722 . The flip flop device  722  can generate both displaying control signals and clearing control signals, which of them are substantially symmetrical and complementary, to display or clear a frame on the symmetric bi-stable display  730 . 
         [0036]    In one embodiment, given that a displaying control signal with a duration of positive state  42 , the clearing control signal would have the negative state  52  with the same duration as the positive state  42 . In other words, clearing control signals are inverse signals of displaying control signals. 
         [0037]    In one embodiment, as shown in  FIG. 6 , displaying and clearing control signals can behave like the switching waveform_ 1   61  changing voltages up and down, or the switching waveform_ 2   62  changing voltages within three levels. However, the equivalent DC voltage of either the switching waveform_ 1   61  or the switching waveform_ 2   62  can also control the gray level of a symmetric bi-stable display, and equivalent DC voltages of displaying control signals and clearing control signals are mutually inverse and symmetrical. Furthermore, compared to the waveform generation unit  220  as shown as in  FIG. 3 , the storage space for storing output conditions in the waveform generation unit  720 , shown in  FIG. 7 , can be reduced to the half. 
         [0038]    Although some embodiments of the present invention have been described, it will be understood by those skilled in the art that the present invention should not be limited to the described preferred embodiments. Rather, various changes and modifications can be made within the spirit and scope of the present invention, as defined by the following Claims.