Abstract:
A mobile LCD device controls a common voltage signal VCOM to effectively display a landscape mode image instead of using a separate integrated chip (IC). The LCD device utilizes a method of displaying a landscape mode image including selecting a video frame from M video frames received from an external source where M is greater than or equal to 2. The selected video frame is stored in a video memory. The selected video frame is masked so as not to display the selected video frame while the selected video frame is stored. The stored video frame is displayed a predetermined number of times while the selected video frame is not stored thereby effectively displaying the landscape mode image.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This U.S. non-provisional patent application claims priority under 35 USC §119 of Korean Patent Application No. 2006-51759 filed on Jun. 9, 2006 the entire contents of which are hereby incorporated by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to displaying landscape mode images. More particularly, embodiments of the invention relate to a method of effectively managing the display of a landscape mode image utilizing a timing controller and a mobile liquid crystal display (LCD) device. 
     2. Discussion of Related Art 
     Liquid crystal display (LCD) devices have been utilized in desktop computers and mobile devices such as cellular phones and palmtop computers. LCDs used in mobile devices (hereinafter referred to as a “mobile LCD device”) have low manufacturing costs and require low power consumption. Mobile LCD devices are also designed to optimize the display of a portrait mode image rather than a landscape mode image. 
       FIG. 1  is a timing diagram illustrating a set of signals used when a conventional mobile LCD device displays a single video frame. A set of signals needed when a single video frame is displayed includes a vertical synchronization signal VSYNC, a horizontal synchronization signal HSYNC and a data enable signal DE. The vertical synchronization signal VSYNC  110  is used for representing a starting point of the single video frame. The mobile LCD device displays the single video frame when the vertical synchronization signal VSYNC is active. Horizontal synchronization signal HSYNC  120  is used for representing a starting point of a single horizontal line of the single video frame. The mobile LCD device displays the single horizontal line when the horizontal synchronization signal HSYNC is active. When the vertical synchronization signal VSYNC  110  is generated once, a plurality of horizontal synchronization signals HSYNCs are generated. Data enable signal DE  130  is used for representing a starting point of data transmission in the single horizontal line. Data corresponding to the single horizontal line is transmitted to the mobile LCD when the data enable signal DE is active. 
       FIG. 2  is a diagram for illustrating a procedure where a video frame is read from or written to a video memory when a mobile LCD device displays a landscape mode image. First, when a portrait mode image is written into video memory  210 , the image is written in horizontal direction  230 . When a landscape mode image is written into video memory  210 , the image is written in a vertical direction  220 . This is because the mobile LCD device is optimized for supporting the portrait mode. When the portrait mode image is read from video memory  210 , the image is read in a horizontal direction  230 . Similarly, when the landscape mode image is read from video memory  210 , the image is also read in horizontal direction  230 . Thus, the mobile LCD device reads the video frame in a horizontal direction  230  from video memory  210  regardless of whether the image mode is portrait or landscape. 
       FIG. 3  is a timing diagram illustrating a set of signals used when a conventional mobile LCD device displays a landscape mode image. A set of signals used when the mobile LCD device displays a landscape mode image includes a vertical synchronization signal VSYNC  310 , an external data enable signal EXTERNAL_DE  320 , an internal data enable signal INTERNAL_DE  330 , a display output signal DO  340  and a common voltage signal VCOM  350 . Vertical synchronization signal VSYNC  310  is used for representing a starting point of a single video frame. The mobile LCD device displays the single video frame when the vertical synchronization signal VSYNC is active. For example, the mobile LCD device may receive 60 vertical synchronization signals VSYNCs per second. A horizontal synchronization signal HSYNC (not illustrated) is used for representing a starting point of a single horizontal line of the single video frame. The mobile LCD device displays the single horizontal line when the horizontal synchronization signal HSYNC is active. When the vertical synchronization signal VSYNC  310  is generated once, a plurality of horizontal synchronization signals HSYNCs are generated. 
     External data enable signal EXTERNAL_DE  320  is used for representing a starting point of data transmission in the single horizontal line. Data corresponding to the single horizontal line is transmitted to the mobile LCD device when the external data enable signal EXTERNAL_DE is active. Internal data enable signal INTERNAL_DE  330  is used for representing a starting point of data storage in the single horizontal line. The data is stored into the video memory when the internal data enable signal INTERNAL_DE  330  is active. For example, when four external data enable signals EXTERNAL_DEs are generated, one internal data enable signal INTERNAL_DE may be generated. That is, the mobile LCD device receives the four frame data and may select one of the four frame data to store the selected one. Display output signal DO  340  represents a starting point of outputting of the video frame. The video frame is read from the video memory when the display output signal DO  340  is active. However, display output signal DO  340  is masked when internal data enable signal INTERNAL_DE  320  is active. Common voltage signal VCOM  350  is used for updating a display in the mobile LCD device. The mobile LCD device displays the video frame when the common voltage signal VCOM  350  is changed from a high voltage to a low voltage or from a low voltage to a high voltage. 
     In general, a period of common voltage signal VCOM  350  is equal to that of display output signal DO  340 . Common voltage signal VCOM  350  is changed 80 times per second in order for the mobile LCD device to display 60 video frames per second. This is because the video frame is masked when internal data enable signal INTERNAL_DE  330  is active. However, if common voltage signal VCOM  350  is changed while internal data enable signal INTERNAL_DE  320  is active, a display problem in the mobile LCD device occurs. 
       FIGS. 4A ,  4 B and  4 C are diagrams illustrating such a problem when a conventional mobile LCD device displays a landscape mode image.  FIG. 4A  represents an original video frame stored in the mobile LCD device.  FIGS. 4B and 4C  represent video frames that may occur if common voltage signal VCOM  350  is changed while internal data enable signal INTERNAL_DE  330  is active. The noise illustrated in  FIGS. 4B and 4C  occurs because the direction in which the video frame is written into the video memory is not the same as the direction in which the video frame is read from the video memory. Accordingly, there is a need for providing an LCD device for effectively displaying a landscape mode image. 
     SUMMARY OF THE INVENTION 
     Exemplary embodiments of the present invention are directed to a method of displaying a landscape mode image. In one exemplary embodiment, a mobile liquid crystal display (LCD) device is used to display a landscape mode image and includes a display panel, a source driver, a gate driver, a driving voltage generator and a timing controller. The display panel has a plurality of gate lines and a plurality of data lines. The source driver is coupled to the display panel and configured to drive the data lines. The gate driver is coupled to the display panel and is configured to drive the gate lines of the display panel. The driving voltage generator is coupled to the gate driver and the display panel and is configured to provide a common voltage signal to the display panel. The driving voltage generator is further configured to provide a control voltage to the gate driver. The timing controller is configured to control a drive timing of the source driver, the gate driver and the driving voltage generator. The timing controller has a video memory configured to store a video frame that is selected from a plurality of video frames received from an external source and a driver controller configured to control a common voltage signal so as not to display the video frame while the video frame is stored into the video memory. The timing controller repeatedly displays the video frame a predetermined number of times while the video frame is not stored. 
     In another exemplary embodiment, a method is used to display a landscape mode image and includes selecting a video frame from M video frames received externally where M is greater than or equal to 2. The method further includes storing the selected video frame into a video memory and masking only the selected video frame so as not to display the selected video frame while the selected video frame is stored. The method also further includes displaying the stored video frame a predetermined number of times while the selected video frame is not stored. 
     In still another exemplary embodiment, a timing controller is used to display a landscape mode image and includes a video memory and a driver controller. The video memory is configured to store a video frame selected from a plurality of video frames received from an external source. The driver controller is coupled to said video memory and is configured to control a common voltage signal so as not to display the video frame while the video frame is stored into said video memory, said driver controller further configured to repeatedly display the video frame a predetermined number of times while the video frame is not stored 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a timing diagram illustrating a set of signals used when a conventional mobile liquid crystal display (LCD) device displays a single video frame. 
         FIG. 2  is a diagram for illustrating a procedure where a video frame is read from/written to video memory when a mobile LCD device displays a landscape mode image. 
         FIG. 3  is a timing diagram illustrating a set of signals used when a conventional mobile LCD device displays a landscape mode image. 
         FIGS. 4A ,  4 B and  4 C are diagrams for illustrating a problem when a conventional mobile LCD device displays a landscape mode image. 
         FIG. 5  is a block diagram illustrating a configuration of a mobile LCD device according to an exemplary embodiment of the present invention. 
         FIG. 6  is a block diagram illustrating the timing controller in  FIG. 5 . 
         FIG. 7  is a timing diagram illustrating a set of signals used for one example operation of a timing controller. 
         FIG. 8  is a timing diagram illustrating a set of signals used for another exemplary operation of a timing controller. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     The present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which preferred embodiments of the invention are shown. This invention, however, may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, like numbers refer to like elements throughout. When an element is referred to as being “connected” or “coupled” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. 
       FIG. 5  is a block diagram illustrating a mobile liquid crystal display (LCD) device  500  including a timing controller  510  having video memory  520 , a driving voltage generator  530 , a source driver  540 , a gate driver  550  and a display panel  560 . Timing controller  510  receives a vertical synchronization signal VSYNC, a horizontal synchronization signal HSYNC, a data enable signal DE, a clock signal MCLK and video data RGB. Timing controller  510  controls driving voltage generator  530 , source driver  540  and gate driver  550  to display a video frame via display panel  560 . 
     Timing controller  510  receives video data RGB and generates the video frame based on video data RGB to store the generated video frame into video memory  520 . For example, timing controller  510  stores a specific video frame in video frames received externally into video memory  520 . Video memory  520  may be included in timing controller  510  or may be placed anywhere in the mobile LCD device. Driving voltage generator  530  receives a driving voltage generation control signal DC from timing controller  510 . Driving voltage generator  530  generates a gate on/off signal Von/Voff and common voltage signal VCOM to control gate driver  550  and display panel  560 . Common voltage signal VCOM is used for updating the video frame displayed in display panel  560 . Display panel  560  updates the video frame when common voltage signal VCOM is changed. 
     Source driver  540  receives single line DATA in the video frame and a source control signal SC from timing controller  510 , and outputs the single line DATA to display panel  560  according to source control signal SC. Gate driver  550  receives gate control signal GC from timing controller  510  and gate on/off signal Von/Voff from driving voltage generator  530 . Gate driver  550  controls display panel  560  so that the single line outputted from source driver  540  is sequentially outputted to each horizontal line of display panel  560 . In this manner, display panel  560  displays the video frame and is controlled by source driver  540 , gate driver  550  and driving voltage generator  530 . 
       FIG. 6  is a block diagram illustrating the timing controller  510  including counter  610 , first AND gate  620 , second AND gate  630 , clock generator  640 , red-green-blue (RGB) converter  650 , third AND gate  660 , driver controller  670  and video memory  520 . Counter  610  receives signal VSYNC to perform a count operation on the number of vertical synchronization signals. For example, counter  610  may perform a count operation on the number of the vertical synchronization signals VSYNCs to determine a time for storing the specified video frame. Assuming that 80 video frames are received per second and the mobile LCD device outputs the 80 video frames per second, one of four video frames may be stored and the other three may be displayed so that the mobile LCD device displays 60 video frames per second. In another example, assuming that 60 video frames are received per second and the mobile LCD device outputs 80 video frames per second, one of four video frames may be stored and four frames may be displayed so that the mobile LCD device displays 60 video frames per second. When a first of four video frames received externally is stored in video memory  520 , counter  610  outputs a logic high based on a multiple of 4. 
     The first AND gate  620  generates an internal data enable signal INERNAL_DE based on the signal outputted from counter  610  and a data enable signal DE received externally. For example, when the number of vertical synchronization signals VSYNCs counted corresponds to a multiple of 4 and the data enable signal DE is received, first AND gate  620  outputs the internal data enable signal INTERNAL_DE. Clock generator  640  receives clock MCLK externally and generates clocks CLK 1  and CLK 2  needed in timing controller  510 . For example, clock generator  640  generates clock CLK 1  for second AND gate  630  and clock CLK 2  for driver controller  670 . Clock CLK 1  is used as a control signal for storing a video frame into video memory  520  and clock CLK 2  is used for controlling driving voltage controller  530 , source driver  540  and gate driver  550 . 
     Second AND gate  630  receives internal data enable signal INTERNAL_DE from first AND gate  620  and clock CLK 1  from clock generator  640 . Second AND gate  630  outputs write enable signal WR_EN to video memory  520  such that second AND gate  630  informs video memory  520  of an amount of time for storing the video frame. RGB converter  650  receives video data RGB externally and generates the video frame from video data RGB. Third AND gate  660  receives the internal data enable signal INTERNAL_DE from first AND gate  620  and the video frame from RGB converter  650 , and outputs the video frame to video memory  520  based on internal data enable signal INTERNAL_DE. Video memory  520  receives write enable signal WR_EN from second AND gate  630  and the video frame from third AND gate  660 , and stores the video frame based on the write enable signal WR_EN. Video memory  520  also receives video data output signal VO from driver controller  670  and sequentially outputs a single line in the video frame to source driver  540 . 
     Driver controller  670  receives clock CLK 2 , vertical synchronization signal VSYNC, horizontal signal HSYNC and internal data enable signal INTERNAL_DE, and generates source control signal SC for controlling source driver  540 . Driver controller  670  also generates gate control signal GC for controlling gate driver  550 . Also, driver controller  670  generates video data output signal VO for controlling an output of video memory  520 . Driver controller  670  controls common voltage signal VCOM so that the video frame is not displayed in an interval where the video frame is stored and repeatedly displays the video frame a predetermined number of times in an interval where the video frame is not stored. For example, when driver controller  670  receives internal data enable signal INTERNAL_DE from first AND gate  620 , driver controller  670  controls the driving voltage generation control signal DC so that common voltage signal VCOM is not changed. When driver controller  670  does not receive the internal data enable signal INTERNAL_DE from first AND gate  620 , driver controller  670  controls the driving voltage generation control signal DC so that the common voltage signal VCOM is changed. Also, driver controller  670  outputs source control signal SC to source driver  540 , gate control signal GC to gate driver  550  and video data output signal DO to video memory  520  to output the video frame stored in video memory  520 . 
       FIG. 7  is a timing diagram illustrating a set of signals used for one exemplary operation of timing controller  510 . A set of signals includes a vertical synchronization signal VSYNC  710 , an external data enable signal EXTERNAL_DE  720 , an internal data enable signal INTERNAL_DE  730 , a display output signal DO  740  and a common voltage signal VCOM  750 . Vertical synchronization signal VSYNC  710  is used for representing a starting point of a single video frame, and the mobile LCD device displays the single video frame when the vertical synchronization signal VSYNC is active. For example, mobile LCD device receives 80 vertical synchronization signals VSYNCs per second so that a period of the vertical synchronization signal VSYNC is the same as that of display output signal DO  740 . Horizontal synchronization signal HSYNC (not illustrated) is used for representing a starting point of a single horizontal line of the single video frame, and the mobile LCD device displays the single horizontal line when the horizontal synchronization signal HSYNC is active. When the vertical synchronization signal VSYNC  710  is generated once, a plurality of horizontal synchronization signals HSYNCs are generated. 
     External data enable signal EXTERNAL_DE  720  is used for representing a starting point of data transmission in the single horizontal line, and data corresponding to the single horizontal line is transmitted to the mobile LCD when the external data enable signal EXTERNAL_DE  720  is active. Internal data enable signal INTERNAL_DE  730  is used for representing a starting point of data storage in the single horizontal line and the data is stored into the video memory when the internal data enable signal INTERNAL_DE  730  is active. 
     In order to generate internal data enable signal INTERNAL_DE counter  610  receives the vertical synchronization signal VSYNC  710  and performs a count operation thereon. When a first video frame of video frames received externally is stored in video memory  520 , counter  610  outputs a logic high based on a multiple of the number of video frames. For example, when four external data enable signals EXTERNAL_DE  720  are generated, the mobile LCD device may generate one internal data enable signal INTERNAL_DE  730 . That is, the mobile LCD device receives four video frames and selects one of the four video frames to store the selected one. First AND gate  620  generates the internal data enable signal INTERNAL_DE based on a determination result of counter  610  and data enable signal DE received externally. Display output signal DO  740  represents a starting point for outputting the video frame. The video frame is read from video memory  520  when display output signal DO  740  is active. However, display output signal DO  740  is masked when internal data enable signal INTERNAL_DE  720  is active. For example, an unmasked display output signal DO  740  may be generated 60 times per second. That is, display output signal DO  740  is masked so as not to display the video frame when the video frame is stored in video memory  520  and is outputted when the video frame is not stored. 
     Driver controller  670  determines the video frame based on a multiple of the number of video frames and outputs a blank video frame based on the result. For example, blank video frame  760  may correspond to black data outputted to display panel  560  or may correspond to a previous video frame. Common voltage signal VCOM  750  is used for updating a display in the mobile LCD device. The mobile LCD device displays the video frame when the common voltage signal VCOM  750  is changed. In addition, the mobile LCD device displays the blank video frame when common voltage signal VCOM  750  is not changed. 
     By way of example, assuming that 80 video frames are received per second and the mobile LCD device outputs the 80 video frames per second, one of four video frames may be stored and three thereof may be displayed so that the mobile LCD device displays 60 video frames per second. Timing controller  510  receives the 80 video frames externally and selects one of four video frames to store the selected one into video memory  520 . That is, counter  610  may perform a count operation on the video frames received externally and determines the video frame based on a multiple of 4. First AND gate  620  generates internal data enable signal INTERNAL_DE  730  based on the determination result of counter  610  and clock CLK 1  and stores the video frame into video memory  520 . When driver controller  670  receives internal data enable signal INTERNAL_DE from first AND gate  620 , driver controller  670  controls the driving voltage generation control signal DC so that the common voltage signal VCOM is not changed. When internal data enable signal INTERNAL_DE  730  is active, driver controller  670  controls the driving voltage generation control signal DC such that common voltage signal VCOM  750  is unchanged. In this manner, the mobile LCD device displays the blank video frame. 
     When internal data enable signal INTERNAL_DE  730  is not active, driver controller  670  controls driving voltage generation control signal DC for changing the common voltage signal VCOM  750  so that the mobile LCD device repeatedly displays the video frame three times. As a result, driver controller  670  controls driving voltage generator  530 , source driver  540  and gate driver  550  to display 60 video frames per second. 
       FIG. 8  is a timing diagram illustrating a set of signals used for an exemplary operation of timing controller  510 . The set of signals includes a vertical synchronization signal VSYNC  810 , an external data enable signal EXTERNAL_DE  820 , an internal data enable signal INTERNAL_DE  830 , a display output signal DO  840  and a common voltage signal VCOM  850 . Vertical synchronization signal VSYNC  810  is used for representing a starting point of a single video frame and the mobile LCD device displays the single video frame when the vertical synchronization signal VSYNC is active. For example, the mobile LCD device receives 80 vertical synchronization signals VSYNCs per second. A horizontal synchronization signal HSYNC (not illustrated) is used for representing a starting point of a single horizontal line of the single video frame. The mobile LCD device displays the single horizontal line when the horizontal synchronization signal HSYNC is active. When the vertical synchronization signal VSYNC  810  is generated once, a plurality of horizontal synchronization signals HSYNCs are generated. 
     External data enable signal EXTERNAL_DE  820  is used for representing a starting point of data transmission in the single horizontal line. Data in the single horizontal line is transmitted to the mobile LCD when the external data enable signal EXTERNAL_DE  820  is active. Internal data enable signal INTERNAL_DE  830  is used for representing a starting point of data storage in the single horizontal line. The data is stored into the video memory when the internal data enable signal INTERNAL_DE  830  is active. 
     In order to generate internal data enable signal INTERNAL_DE, counter  610  receives vertical synchronization signal VSYNC  810  and performs a count operation thereon. When a first video frame of video frames received externally has to be stored into video memory  520 , counter  610  outputs a logic high based on a multiple of the number of the video frames. For example, when four external data enable signals EXTERNAL_DE  820  are generated, the mobile LCD device may generate one internal data enable signal INTERNAL_DE  830 . That is, the mobile LCD device receives four video frames and selects one of the four video frames to store the selected one. First AND gate  620  generates the internal data enable signal INTERNAL_DE based on a determination of counter  610  and data enable signal DE. Display output signal DO  840  is used for representing a starting point of outputting of the video frame. The video frame is read from video memory  520  when display output signal DO  840  is active. However, display output signal DO  840  is masked when internal data enable signal INTERNAL_DE  820  is active. For example, an unmasked display output signal DO  840  may be generated 60 times per second. Display output signal DO  840  is masked so as not to display the video frame when the video frame is stored in video memory  520  and is outputted when the video frame is not stored. 
     Driver controller  670  determines the video frame based on a multiple of the number of the video frames and outputs a blank video frame based on the result. For example, blank video frame  860  may correspond to black data outputted to display panel  560 , or may correspond to a previous video frame. Common voltage signal VCOM  850  is used for updating a display in the mobile LCD device. The mobile LCD device displays the video frame when common voltage signal VCOM  850  is changed. In addition, the mobile LCD device displays the blank video frame when common voltage signal VCOM  850  is unchanged. 
     By way of another example, assuming that 60 video frames are received per second and the mobile LCD device outputs the 80 video frames per second, one of four video frames may be stored and four frames may be displayed so that the mobile LCD device displays 60 video frames per second. Timing controller  510  receives the 60 video frames externally, and selects one of four video frames to store the selected one in video memory  520 . Counter  610  may perform a count operation on the externally received video frames and determines the video frame based on a multiple of 4. First AND gate  620  generates internal data enable signal INTERNAL_DE  830  based on the determination result of counter  610  and clock CLK 1  to store the video frame into video memory  520 . When driver controller  670  receives internal data enable signal INTERNAL_DE  830  from first AND gate  620 , driver controller  670  controls the driving voltage generation control signal DC. In this manner, common voltage signal VCOM is unchanged. 
     When internal data enable signal INTERNAL_DE  830  is active, driver controller  670  controls driving voltage generation control signal DC. Common voltage signal VCOM  850  remains unchanged so that the mobile LCD device displays the blank video frame. When internal data enable signal INTERNAL_DE  830  is not active, driver controller  670  controls driving voltage generation control signal DC for changing the common voltage signal VCOM  850 , so that the mobile LCD device repeatedly displays the video frame four times. As a result, driver controller  670  controls driving voltage generator  530 , source driver  540  and gate driver  550  to display 60 video frames per second. 
     As described above, the mobile LCD device controls a common voltage signal VCOM to effectively display a landscape mode image instead of using a separate integrated chip (IC) for controlling the display of the landscape mode image. 
     Although the present invention has been described in connection with the embodiment of the present invention illustrated in the accompanying drawings, it is not limited thereto. It will be apparent to those skilled in the art that various substitution, modifications and changes may be thereto without departing from the scope and spirit of the invention.