Abstract:
A drive circuit applicable to a display device includes a first signal path and a second signal path. The first signal path, configured to receive image data and transmit the image data in a first operation mode, includes a compression unit, a storage unit and a de-compression unit. In the first operation mode, the compression unit performs a compression procedure on the image data to generate compression data, the storage unit stores the compression data, and the de-compression unit receives the compression data and performs a de-compression procedure on the compression data to recover the image data. The second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation application of U.S. application Ser. No. 14/078,490, filed on Nov. 12, 2013, the contents of which are incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
       [0002]    The present invention relates to a data compression system for a liquid crystal display (LCD), and more particularly, to a data compression system and related power saving method capable of selecting a data transmission path according to an operation mode. 
       2. Description of the Prior Art 
       [0003]    The liquid crystal display (LCD), which has advantages of thin appearance, low power saving and low radiation, etc. has widely been applied in various electronic products such as a computer screen, mobile telephone, personal digital assistant (PDA), flat television, and other communication/entertainment equipment. The principle of LCD is to vary the arrangement of liquid crystal molecules in a liquid crystal layer by varying the voltage difference between two terminals of the liquid crystal layer. The transparency of the liquid crystal layer may change accordingly, which is further incorporated with the light source provided by a backlight module to display images. 
         [0004]    The LCD includes a drive chip. After data is transmitted from a host to the drive chip, the data may be compressed by a compression circuit and stored in a compression memory. The drive chip then utilizes a de-compression circuit to transmit the data to the display area. When the drive chip is operated in some particular modes, information related to complete color gamut may not be required. Thus, compressing the information data of complete color gamut via the compression circuit may generate unnecessary power consumption. 
       SUMMARY OF THE INVENTION 
       [0005]    It is therefore an objective of the present invention to provide a data compression system for a liquid crystal display (LCD), in order to reduce power consumption of the LCD. 
         [0006]    The present invention discloses a drive circuit applicable to a display device. The drive circuit comprises a first signal path and a second signal path. The first signal path, configured to receive image data and transmit the image data in a first operation mode, comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on the image data to generate compression data in the first operation mode. The storage unit, coupleable to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode. 
         [0007]    The present invention further discloses a data compression system applicable to a display device. The data compression system comprises a host and a drive circuit. The host is configured for outputting image data. The drive circuit, coupled to the host, comprises a first signal path and a second signal path. The first signal path, configured to receive image data from the host and transmit the image data in a first operation mode, comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on the image data to generate compression data in the first operation mode. The storage unit, coupled to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The second signal path is configured to receive image data from the host, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit in a second operation mode. 
         [0008]    The present invention further discloses a power saving method. The power saving method comprises conducting a first signal path in a first operation mode, wherein the first signal path comprises a compression unit, a storage unit and a de-compression unit. The compression unit is configured to perform a compression procedure on image data to generate compression data in the first operation mode. The storage unit, coupled to the compression unit, is configured to store the compression data in the first operation mode. The de-compression unit, coupled to the storage unit, is configured to receive the compression data and perform a de-compression procedure on the compression data to recover the image data in the first operation mode. The power saving method further comprises conducting a second signal path in a second operation mode, wherein the second signal path is configured to receive image data, transmit the image data to the storage unit so as to bypass the compression unit, and transmit the image data received from the storage unit to a display unit so as to bypass the decompression unit. 
         [0009]    The present invention further discloses a power saving method for a display device. The power saving method comprises performing a first signal processing procedure in a first operation mode. The first signal processing procedure comprises performing a compression procedure on image data to generate compression data in the first operation mode; storing the compression data in a storage device in the first operation mode; and performing a de-compression procedure on the compression data to recover the image data in the first operation mode. The power saving method further comprises performing a second signal processing procedure in a second operation mode. The second signal processing procedure comprises transmitting the image data to the storage unit so as to bypass the compression procedure; and transmitting the image data received from the storage unit to a display unit so as to bypass the decompression procedure. 
         [0010]    These and other objectives of the present invention will no doubt become obvious to those of ordinary skill in the art after reading the following detailed description of the preferred embodiment that is illustrated in the various figures and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a schematic diagram of a data compression system according to an embodiment of the present invention. 
           [0012]      FIG. 2A  and  FIG. 2B  are schematic diagrams of a data format according to an embodiment of the present invention. 
           [0013]      FIG. 2C  is a schematic diagram of compressed data according to an embodiment of the present invention. 
           [0014]      FIG. 3  and  FIG. 4  are timing diagrams of image data indifferent output terminals according to an embodiment of the present invention. 
           [0015]      FIG. 5  is a schematic diagram of a data compression system according to another embodiment of the present invention. 
           [0016]      FIG. 6  and  FIG. 7  are timing diagrams of image data indifferent output terminals according to an embodiment of the present invention. 
           [0017]      FIG. 8  is a schematic diagram of a process according to an embodiment of the present invention. 
           [0018]      FIG. 9  is a schematic diagram of a process according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0019]    Please refer to  FIG. 1 , which is a schematic diagram of a data compression system  10  according to an embodiment of the present invention. The data compression system  10  is utilized for a liquid crystal display (LCD). The data compression system  10  includes a host  100  and a drive circuit  120 . The host  100  is utilized for outputting image data Img_D in a data format frmt 1  or a data format frmt 2  according to an operation mode of the LCD. Preferably, the drive circuit  120  may be realized by a drive integrated circuit (IC). The drive circuit  120  includes an image data unit  121 , a compression unit  122 , switching units  123  and  126 , a storage unit  124 , a de-compression unit  125 , a display unit  127 , a bypass path L 1  and a complete data path L 2 . The switching units  123  and  126  are utilized for switching between the bypass path L 1  and the complete data path L 2 . The compression unit  122  is utilized for receiving the image data Img_D and performing a compression procedure on the image data Img_D according to the operation mode to generate a compression data Cmprs_D. The storage unit  124 , coupled to the compression unit  122  and the host  100 , is utilized for storing the compression data Cmprs_D and the image data Img_D. The storage unit  124  may preferably be a static random access memory (SRAM). The de-compression unit  125 , coupled to the storage unit  124 , is utilized for receiving the compression data Cmprs_D and performing a de-compression procedure on the compression data Cmprs_D to recover the image data Img_D according to the operation mode. The display unit  127  is utilized for displaying the image data Img_D. 
         [0020]    When the operation mode is a particular mode, the host  100  outputs the image data Img_D in a data format frmt 1 , and transmits the image data Img_D in the data format frmt 1  via the bypass path L 1 . When the operation mode is a general mode, the host  100  outputs the image data Img_D in a data format frmt 2 , and transmits the image data Img_D in the data format frmt 2  via the complete data path L 2 . Preferably, the image data in the data format frmt 1  has fewer bit numbers than the image data in the data format frmt 2 . In addition, the particular mode includes a color gamut reduction mode, a partial area display mode and a scale up display mode. In the particular mode, the full information of the color gamut is not necessary. For example, in the color gamut reduction mode, RGB color model may be reduced from 24 bits to 3 bits; in the partial area display mode, when the LCD is switched from 480×800 full screen display to 100×100 partial screen display, other area on the screen that does not display images may be replaced by a single color; in the scale up display mode, when the LCD is switched from 480×800 full screen display to 240×400 scale up display, only half data is required to fulfill 480×800 full screen display. Therefore, in the particular mode, the host  100  may output the image data Img_D in the data format frmt 1  with smaller data quantity, reduce the data quantity required to be stored in the storage unit  124 , and transmit the image data Img_D to the display unit  127  via the bypass path L 1  without undergoing the compression procedure and de-compression procedure. As a result, unnecessary power consumption will be prevented. 
         [0021]    Please refer to  FIGS. 2A, 2B and 2C .  FIG. 2A  is a schematic diagram of the data format frmt 2  according to an embodiment of the present invention;  FIG. 2B  is a schematic diagram of the data format frmt 1  according to an embodiment of the present invention;  FIG. 2C  is a schematic diagram of the compression data Cmprs_D according to an embodiment of the present invention. In  FIG. 2A , each pixel includes three sub-pixels R, G, B, and each sub-pixel may be represented by 8 bits. Therefore, each pixel includes 24 bits. In  FIG. 2B , each pixel only uses 3 bits to represent three sub-pixels R, G, B. In comparison, the data format frmt 1  has less data quantity than the data format frmt 2 . 
         [0022]    The operations of the data compression system  10  are detailed as follows. When the operation mode is the general mode, the host  100  outputs the image data Img_D in the data format frmt 2 . The image data Img_D in the data format frmt 2  may first be passed through the image data unit  121 , and then transmitted to the compression unit  122  via the complete data path L 2 . The compression unit  122  performs the compression procedure on the image data Img_D in the data format frmt 2  to generate the compression data Cmprs_D. The switching unit  123  selects the compression data Cmprs_D coming from the complete data path L 2 , and stores the compression data Cmprs_D in the storage unit  124 . The de-compression unit  125  then receives the compression data Cmprs_D, and performs the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D in the data format frmt 2 . The switching unit  126  transmits the image data Img_D in the data format frmt 2  to the display unit  127  via the complete data path L 2 . Finally, the display unit  127  displays the image data Img_D in the data format frmt 2 . When the operation mode is switched from the general mode to the particular mode, the host  100  re-transmits transmitted image data Prv_D 1  in the data format fmrt 1  in the next image frame after the switching, where the transmitted image data Prv_D 1  has been transmitted in the data format fmrt 2  when the operation mode is the general mode. When the host  100  re-transmits the image data Prv_D 1  in the data format fmrt 1 , the display unit  127  displays a black screen, in order to prevent an abnormal image from being displayed. When the operation mode is the particular mode, the host  100  outputs the image data Img_D in the data format frmt 1 . The image data Img_D in the data format frmt 1  first is passed through the image data unit  121 , and transmitted to the switching unit  123 , bypassing the compression unit  122  via the bypass path L 1 . The switching unit  123  selects the image data Img_D in the data format frmt 1  coming from the bypass path L 1 , and stores the image data Img_D in the data format frmt 1  in the storage unit  124 . The switching unit  126  then transmits the image data Img_D in the data format frmt 1  to the display unit  127  via the bypass path L 1 . Finally, the display unit  127  displays the image data Img_D in the data format frmt 1 . When the operation mode is switched from the particular mode back to the general mode, the host  100  re-transmits an image data Prv_D 2  in the data format fmrt 2  in next image frame after the switching, and the image data Prv_D 2  has been transmitted in the data format fmrt 1  when the operation mode is the particular mode. When the host  100  re-transmits the image data Prv_D 2  in the data format fmrt 2 , the display unit  127  displays a black screen, in order to prevent an abnormal image from being displayed. The operations after the operation mode returns to the general mode are illustrated above, and will not be narrated herein. Therefore, when the operation mode is the particular mode, the data compression system  10  transmits the image data Img_D in the data format fmrt 1  to the display unit  127  via the bypass path L 1  and omits the compression procedure and the de-compression procedure, in order to reduce power consumption. 
         [0023]    In addition, please refer to  FIG. 3  and  FIG. 4 .  FIG. 3  is a timing diagram of image data in different output terminals when the operation mode is switched from the general mode to the particular mode according to an embodiment of the present invention;  FIG. 4  is a timing diagram of image data in different output terminals when the operation mode is switched from the particular mode to the general mode according to an embodiment of the present invention. In  FIG. 3  and  FIG. 4 , the horizontal axis represents time, on which each time interval denotes a time period of an image frame. Details of  FIG. 3  and  FIG. 4  are illustrated above, and will not be narrated herein. 
         [0024]    Please refer to  FIG. 5 , which is a schematic diagram of a data compression system  50  according to another embodiment of the present invention. The data compression system  50  may be utilized in an LCD. The basic structures of the data compression system  50  are similar to those of the data compression system  10 ; hence data in the same output terminals are denoted by the same symbols. The data compression system  50  includes a host  500  and a drive circuit  520 . The host  500  is utilized for outputting an image data Img_D, which is in a data format fmrt 2 . Preferably, the drive circuit  520  may be realized by a driving IC. The drive circuit  520  includes an image data unit  521 , a compression unit  522 , switching units  523  and  527 , a storage unit  524 , a format conversion unit  525 , a de-compression unit  526 , a display unit  528 , a bypass path L 3  and a complete data path L 4 . The switching units  523  and  527  are utilized for switching between the bypass path L 3  and the complete data path L 4 . The compression unit  522  is utilized for receiving the image data Img_D and performing the compression procedure on the image data Img_D to generate the compression data Cmprs_D according to the operation mode. The storage unit  524 , coupled to the compression unit  522  and the host  500 , is utilized for storing the compression data Cmprs_D and the image data Img_D. Preferably, the storage unit  524  may be an SRAM. The format conversion unit  525 , coupled to the storage unit  524 , is utilized for performing a format conversion procedure to convert the image data Img_D into the data format frmt 1  or the data format frmt 2 . The de-compression unit  526 , coupled to the storage unit  524 , is utilized for receiving the compression data Cmprs_D and performing the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D according to the operation mode. The display unit  528  is utilized for displaying the image data Img_D. 
         [0025]    When the operation mode is the particular mode, the image data Img_D in the data format frmt 2  is transmitted to the storage unit  524  via the bypass path. The format conversion unit  525  reads the image data Img_D in the data format frmt 2  from the storage unit  524 , converts the image data Img_D in the data format frmt 2  into the data format frmt 1  with smaller amount of data, and stores the data back to the storage unit  524 , where the compression procedure and the de-compression procedure are both omitted. As a result, unnecessary power consumption may be prevented. 
         [0026]    The operations of the data compression system  50  are detailed as follows. When the operation mode is the general mode, the host  500  outputs the image data Img_D in the data format frmt 2 . The image data Img_D in the data format frmt 2  is first passed through the image data unit  521 , and transmitted to the compression unit  522  via the complete data path L 4 . The compression unit  522  performs the compression procedure on the image data Img_D in the data format frmt 2  to generate the compression data Cmprs_D. The switching unit  523  selects the compression data Cmprs_D from the complete data path L 4 , and stores the compression data Cmprs_D in the storage unit  524 . The de-compression unit  526  then receives the compression data Cmprs_D, and performs the de-compression procedure on the compression data Cmprs_D to recover the image data Img_D in the data format frmt 2 . The switching unit  527  transmits the image data Img_D in the data format frmt 2  to the display unit  528  via the complete data path L 4 . Finally, the display unit  528  displays the image data Img_D in the data format frmt 2 . When the operation mode is switched from the general mode to the particular mode, the host  500  outputs the image data Img_D in the data format frmt 2  to the image data unit  521 , and transmits the image data Img_D in the data format frmt 2  to the storage unit  524  via the bypass path L 3 . The format conversion unit  525  reads the image data Img_D in the data format frmt 2  from the storage unit  524  in the next image frame after the switching, and converts the image data Img_D from the data format frmt 2  into the data format frmt 1  and then stores the image data Img_D back to the storage unit  524 . When the format conversion unit  525  performs the format conversion procedure, the display unit  528  displays a black screen, in order to prevent an abnormal image from being displayed. When the format conversion procedure is accomplished, the display unit  528  may display the image data Img_D in the data format frmt 1 . When the operation mode is switched from the particular mode back to the general mode, the format conversion unit  525  reads the image data Img_D in the data format frmt 1  from the storage unit  524  in the next image frame after the switching, and converts the image data Img_D from the data format frmt 1  into the data format frmt 2  and then stores the image data Img_D back to the storage unit  524 . Similarly, when the format conversion unit  525  performs the format conversion procedure, the display unit  528  may display a black screen, in order to prevent an abnormal image from being displayed. When the format conversion procedure is accomplished, the display unit  528  may display the image data Img_D in the data format frmt 2 . The operations after the operation mode returns to the general mode are illustrated above, and will not be narrated herein. Therefore, when the operation mode is the particular mode, the data compression system  50  transmits the image data Img_D to the display unit  528  via the bypass path L 3 , and the compression procedure and the de-compression procedure are omitted, in order to reduce power consumption. Please note that, in comparison with the data compression system  10 , in the data compression system  50  the host  500  may not need to re-transmit, and the data format conversion is performed by the format conversion unit  525 . 
         [0027]    In addition, please refer to  FIG. 6  and  FIG. 7 .  FIG. 6  is a timing diagram of image data in different output terminals when the operation mode is switched from the general mode to the particular mode according to an embodiment of the present invention;  FIG. 7  is a timing diagram of image data in different output terminals when the operation mode is switched from the particular mode to the general mode according to an embodiment of the present invention. In  FIG. 6  and  FIG. 7 , the horizontal axis represents time, on which each time interval denotes a time period of an image frame. Details of  FIG. 6  and  FIG. 7  are illustrated above, and will not be narrated herein. 
         [0028]    The operations related to the data compression system  10  can be summarized into a process  80 , as shown in  FIG. 8 . The process  80 , which may be utilized in the data compression system  10  for power saving, includes the following steps: 
         [0029]    Step  800 : Start. 
         [0030]    Step  802 : Determine the operation mode. If the operation mode is the general mode, go to Step  804 ; if the operation mode is the particular mode, go to Step  806 . 
         [0031]    Step  804 : Output the image data Img_D in the data format fmrt 1 , and go to Step  808 . 
         [0032]    Step  806 : Output the image data Img_D in the data format fmrt 2 , and go to Step  810 . 
         [0033]    Step  808 : Transmit the image data Img_D in the data format fmrt 1  via the bypass path L 1 , and go to Step  816 . 
         [0034]    Step  810 : Transmit the image data Img_D in the data format fmrt 2  via the complete data path L 2 . 
         [0035]    Step  812 : Perform the compression procedure. 
         [0036]    Step  814 : Perform the de-compression procedure. 
         [0037]    Step  816 : Display the image data Img_D. 
         [0038]    According to the process  80 , when the operation mode is the particular mode, the data compression system  10  transmits the image data Img_D in the data format fmrt 1  via the bypass path L 1  and omits the compression procedure and the de-compression procedure, in order to reduce power consumption. When the operation mode is the general mode, the data compression system  10  performs the compression procedure and the de-compression procedure on the image data Img_D in the data format fmrt 2  via the complete data path L 2 . Detailed operations of the process  80  are illustrated above, and will not be narrated herein. 
         [0039]    The operations related to the data compression system  50  can be summarized into a process  90 , as shown in  FIG. 9 . The process  90 , which may be utilized in the data compression system  50  for power saving, includes the following steps: 
         [0040]    Step  900 : Start. 
         [0041]    Step  902 : Output the image data Img_D, wherein the image data Img_D has the data format frmt 2 . 
         [0042]    Step  904 : Determine the operation mode. If the operation mode is the general mode, go to Step  906 ; if the operation mode is the particular mode, go to Step  908 . 
         [0043]    Step  906 : Transmit the image data Img_D in the data format fmrt 2  via the bypass path L 3 , and go to Step  914 . 
         [0044]    Step  908 : Transmit the image data Img_D in the data format fmrt 2  via the complete data path L 4 . 
         [0045]    Step  910 : Perform the compression procedure. 
         [0046]    Step  912 : Perform the de-compression procedure, and go to Step  916 . 
         [0047]    Step  914 : Perform the format conversion procedure. 
         [0048]    Step  916 : Display the image data Img_D. 
         [0049]    According to the process  90 , when the operation mode is the particular mode, the data compression system  50  transmits the image data Img_D in the data format fmrt 2  via the bypass path L 3  and omits the compression procedure and the de-compression procedure, and performs the format conversion procedure to convert the image data Img_D from the data format fmrt 2  into the data format fmrt 1 . When the operation mode is the general mode, the data compression system performs the compression procedure and the de-compression procedure on the image data Img_D in the data format fmrt 2  via the complete data path L 4 . Detailed operations of the process  90  are illustrated above, and will not be narrated herein. 
         [0050]    To sum up, an embodiment of the present invention may determine a transmitting path of the image data (the bypass path or the complete data path) according to the operation mode. When the operation mode is the particular mode without full color information (the color gamut reduction mode, the partial area display mode and the scale up display mode), an embodiment of the present invention may transmit the image data in a data format with smaller amount of data or convert the image data into a data format with smaller amount of data to transmit the image data via the bypass path, wherein the compression procedure and the de-compression procedure are omitted, in order to achieve power saving. 
         [0051]    Those skilled in the art will readily observe that numerous modifications and alterations of the device and method may be made while retaining the teachings of the invention. Accordingly, the above disclosure should be construed as limited only by the metes and bounds of the appended claims.