Patent Publication Number: US-7711394-B2

Title: Display interface of mobile telecommunication terminal

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   Pursuant to 35 U.S.C.§119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2004-0027024, filed on Apr. 20, 2004, the contents of which is hereby incorporated by reference herein in its entirety. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to a mobile telecommunication terminal, and more particularly to a display interface of a mobile telecommunication terminal. 
   2. Discussion of the Related Art 
     FIG. 1  is a schematic view of a related art mobile telecommunication terminal.  FIG. 2  is a schematic view of a related art liquid crystal display interface.  FIG. 3  is a signal timing diagram according to the related art liquid crystal display interface. 
   Referring to  FIG. 1 , a folding type mobile telecommunication terminal  100  includes a main body  110  and a liquid crystal display (LCD)  120 . Using a 16-bit bus, data is transmitted between the main body  110  and the LCD  120 . Referring now to  FIG. 2 , the 16-bit bus includes a plurality of signal lines to control sixteen data lines used to transmit data. The control signals include a chip select (CS) signal, a write enable (WE) signal, an output enable (OE) signal, and an address (Add) signal. The CS signal is used to enable the LCD  120 . The WE signal is used to write data from the main body  110  to the LCD  120 . The OE signal is a read signal to read information from the main body  110 . The Add signal is an address signal to select a color signal (i.e., red (R), green (G), and blue (B)) (color signal information). As described above, the 16-bit bus LCD interface requires twenty signal lines. 
   In the 16-bit bus, the color information (R, G, and B) in a pixel of an LCD is transmitted by n-bits in a digital form. Therefore, a data width of 3×n is required for the transmission. When the required data width exceeds 16 bits, the data is divided and transmitted by units of 16 bits. For example, when using an LCD screen displaying 256k colors, 6 bits for each color R, G, and B are allotted, thereby requiring a data width of 18 bits. The 18-bit packed data is divided into a 16-bit data packet and a 2-bit data packet, to be transmitted to the LCD through the bus using two cycles, as shown in  FIG. 3 . 
   Therefore, when a 16-bit bus is used, twenty signal lines, including a data signal and a control signal are required to transmit the data. In the folding type mobile telecommunication terminal, the LCD  120  is connected to the main body  110  by a hinge  130 . The signal lines are connected to one another through a flexible printed circuit board (FPCB)  140 . The width of the FPCB  140  is limited due to structural limitations of such a connection. Furthermore, folding type communication devices are frequently opened and closed, which applies structural stress to the FPCB  140 . 
   In order to prevent a deficiency in the signal line from occurring, such as a break, the width of the signal line must be of at least some minimum width. In one such minimum pattern width, forty signal lines are used in the FPCB  140 . The forty signal lines are used as signal lines between the main body  110  and the LCD  120 , as well as to a receiver, a vibrating mechanism, a light emitting diode (LED), and a power source. Thus, additional signal lines are not available to perform other functions. Furthermore, by allotting a maximum number of signal lines into a limited width FPCB  140 , the reliability of each signal line may be decreased. 
   In addition, as the functions of the recently introduced mobile telecommunication terminals are becoming more diverse, consumers need to open and close the hinge  130  more often. Consumers now also demand more sophisticated designs and structures for the hinge  130 , such as those used in LCDs of camcorder type devices and slim type communication devices. Therefore, in order to satisfy these consumer demands, the width of the FPCB  140  needs to be reduced. However, since the 16-bit bus requires 20 signal lines, it is not possible to reduce the width of the FPCB  140 . 
   SUMMARY OF THE INVENTION 
   The present invention is directed to a display interface of a mobile telecommunication terminal that addresses one or more problems of the related art. 
   An object of the present invention is to provide a display interface of a mobile telecommunication terminal that may reduce the number of signal lines used. 
   Another object of the present invention is to provide a display interface of a mobile telecommunication terminal that may implement additional functions by using the surplus signal lines. 
   Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. 
   To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, the display interface (interface device) is preferably located in a mobile telecommunication terminal that includes a main body having a processor, and a display coupled to the main body. The processor is configured to implement mobile telecommunication terminal functions. The interface device includes a digital-to-analog converter configured to convert digital pixel information to an analog color signal. The digital pixel information may preferably be stored in a video buffer in the main body. The interface device also includes graphic signal lines operatively connected to the digital-to-analog converter, configured to carry the analog color signal to the display. The interface device also includes a clock line operatively connected to the digital-to-analog converter, configured to provide a timing reference used to sample the analog color signal. The interface device also includes a data enable line operatively connected to the digital-to-analog converter, configured to control transmission of the analog color signal through the graphic signal lines based on a selective switching operation. 
   The interface device may preferably include an analog-to-digital converter operatively connected to the graphic signal lines, configured to convert the analog color signal into digital data. The graphic signal lines may preferably be connected via a flexible printed circuit board (FPCB). The analog color signal may preferably include red-green-blue (RGB) color information. 
   The display may preferably be a liquid crystal display (LCD). The mobile telecommunication terminal may preferably be a folding type mobile telecommunication terminal, such as for example, a “flip-phone”. 
   In another embodiment, an interfacing method in a mobile telecommunication terminal having a main body and a display includes the steps of converting graphic data into an analog signal and transmitting the analog signal to the display. The graphic data may preferably be formed in the main body. The method also includes the steps of converting the analog signal to a digital signal, and storing the digital signal in a video buffer. The method may also preferably include the step of performing a switching operation to control the transmitting of the analog signal to the display. The step of performing a switching operation may preferably include transmitting a command signal. The step of performing a switching operation may also preferably include transmitting a data signal. The method may also include driving the display based on the digital signal stored in the video buffer. 
   As described above, in the display interface of a mobile telecommunication terminal, the number of signal lines may be reduced. Additionally, by maintaining FPCB width, the pattern width of each signal line may be increased to improve device reliability. Furthermore, surplus signal lines may be allotted to perform other device functions, thereby improving device functionality. Alternatively, the overall width of the FPCB may be reduced to accommodate sophisticated hinge designs and telecommunication terminal designs. 
   The present invention may be particularly suitable for transmitting and receiving data to and from the display using a flexible printed circuit board. The present invention uses an analog video signal to reduce the number of flexible printed circuit board signal lines, which may improve reliability. The display interface may also have a reduced signal line width between the main body and the display. Accordingly, the present invention may improve performance, functionality, and reliability in mobile telecommunication terminals. 
   It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. 
       FIG. 1  is a schematic view of a related art mobile telecommunication terminal. 
       FIG. 2  is a schematic view of a related art display interface. 
       FIG. 3  is a signal timing diagram according to a related art display interface. 
       FIG. 4  is a schematic view of a display interface, according to one embodiment of the present invention. 
       FIG. 5  is a signal timing diagram that corresponds to the display interface of  FIG. 4 , according to one embodiment of the present invention. 
       FIG. 6  is a signal timing diagram that corresponds to the display interface of  FIG. 4 , according to another embodiment of the present invention. 
       FIG. 7  is a flow diagram illustrating a method for interfacing a display of a mobile telecommunication terminal, according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
     FIG. 4  is a schematic view of a display interface  450  coupled to a processor  411  and a display screen  421 , according to one embodiment of the present invention. The display screen  421  may be, for example, a liquid crystal display (LCD) screen or other type of display screen. 
   Referring to  FIG. 4 , the display interface  450  includes a digital-to-analog converter (DAC)  460 , configured to convert graphic data into an analog signal (analog color signal). The display interface  450  also includes an analog-to-digital converter (ADC)  470  configured to convert the analog signal into graphic data. The display interface  450  also includes a video buffer  480  configured to store the graphic data. The DAC  460  is communicatively coupled to the ADC  470  via a plurality of graphic signal lines  485 . The DAC  460  is also communicatively coupled to the ADC  470  via a clock line (CLK)  487  and a data enable line (DE)  489 . Signal lines  483  include the graphic signal lines  485 , the clock line  487  and the data enable line  489 . In the embodiment depicted in  FIG. 4 , the DAC  460  and the processor  411  are located in a main body  410 . The DAC  460  and the processor  411  are communicatively coupled by a data bus (bus)  413 . In the embodiment depicted in  FIG. 4 , the ADC  470 , the video buffer  480 , and a display screen  421  are located in a display  420 . Thus, the display (display part)  420  includes the display screen  421 , as well as one or more other components. 
   Referring again to  FIG. 4 , the display interface  450  preferably includes five signal lines including graphic signal lines  485  (red (R), green (G), and blue (B)), configured to carry the analog signal used to drive pixels of the display  420 . The clock line  487  may preferably perform sample timing. The data enable line  489  may preferably select data and command signals. The digital-to-analog converter  460  is configured to convert graphic data into analog signals using the processor  411  and the data bus  413 . The analog-to-digital converter  470  is configured to convert the analog signals carried through the signal lines  483  into graphic data. 
   RGB color information (red (R), green (G), and blue (B)) used to drive a pixel of the display screen  421  is transmitted in an analog form (analog color signal). To this end, a command signal may be output to transmit the pixel information from the processor  411  to the video buffer  480 . The command signal may be configured to convert the pixel information into an analog signal. 
   In another embodiment, the display interface (interface device)  450  is located in a mobile telecommunication terminal that includes the main body  410  having the processor  411 , and the display  420  coupled to the main body  410 . The processor  411  is configured to implement mobile telecommunication terminal functions. In the embodiment, the interface device  450  includes the digital-to-analog converter  460  configured to convert digital pixel information to an analog color signal. The digital pixel information may preferably be stored in a video buffer in the main body  410 . The interface device  450  also includes the graphic signal lines  485  operatively connected to the digital-to-analog converter  460 , configured to carry the analog color signal to the display  420 . The interface device  450  also includes the clock line  487  operatively connected to the digital-to-analog converter  460 , configured to provide a timing reference used to sample the analog color signal. The interface device  450  also includes the data enable line  489  operatively connected to the digital-to-analog converter  460 , configured to control transmission of the analog color signal through the graphic signal lines  485  based on a selective switching operation. 
   The interface device may preferably include the analog-to-digital converter  470  operatively connected to the graphic signal lines  487 , configured to convert the analog color signal into digital data. The graphic signal lines may preferably be connected via a flexible printed circuit board (FPCB). The analog color signal may preferably include red-green-blue (RGB) color information. 
   The display may preferably be a liquid crystal display (LCD). The mobile telecommunication terminal may preferably be a folding type mobile telecommunication terminal, such as for example, a “flip-phone”. 
     FIG. 5  is a signal timing diagram that corresponds to the display interface  450  of  FIG. 4 , according to one embodiment of the present invention. 
   Referring to  FIG. 5 , the analog signal may preferably be transmitted to the display  420  through each color (R, G, and B) of the graphic signal lines  485  on a flexible printed circuit board (FPCB). The transmitted analog signal may preferably be directly coupled to a display drive circuit. Alternatively, the transmitted analog signal may preferably be converted into a digital data by the ADC  470  to be stored in the video buffer  480 . The clock  487  provides a timing reference used to sample the analog signal. The data enable signal  489 , which represents the data, is preferably maintained at a high state. A command signal is preferably transmitted when the DE signal is maintained at a low state. The graphic data is preferably transmitted when the DE signal is at a high state. 
   When transmitting a command to the display  420 , the DE signal  489  preferably identifies the command signal. The command signal is then transmitted in accordance with a corresponding protocol. Then, one or more of the red, green, and blue graphic signal lines  485  are used to transmit the analog color signal and corresponding data. If the command signal is transmitted in the same way as the analog color signal, the clock line  487  is preferably used to synchronize the signals. 
   In the embodiment depicted in  FIG. 5 , each of the graphic signal lines  485  is allocated to transmit graphic data (analog color signals). However, in order to insure a noise margin and/or to reduce quantization error of each analog color (R, G, and B) signal, the graphic signal line for each color (R, G, and B) may be heterogeneous. 
     FIG. 6  is a signal timing diagram that corresponds to the display interface  450  of  FIG. 4 , where the graphic signal lines  485  are heterogeneous, according to another embodiment of the present invention. 
   Referring to  FIG. 6 , display interface  450  includes eight signal lines. The eight signal lines may preferably include Red+, Red−, Green+, Green−, Blue+, and Blue− signal lines, the clock line  487 , and the data enable line  489 . 
     FIG. 7  is a flow diagram illustrating a method for interfacing a display of a mobile telecommunication terminal, according to one embodiment of the present invention. 
   Referring to  FIG. 7 , at step  710 , a digital-to-analog converter converts graphic data into analog signals (analog color signals) in accordance with a command signal provided by a processor within a main body. The graphic data converted into analog signals may preferably be transmitted to the display through a flexible printed circuit board (FPCB). At step  720 , a clock line provides a sampling timing, and a data enable signal is changed to a high state to enable transmission of the data. At step  730 , the graphic data converted into analog signals is converted into digital signals using an analog-to-digital converter (ADC). At step  740 , the digital signals are stored to a video buffer. Alternatively, the graphic data converted into analog signals is directly transmitted to a display screen. At step  750 , the display screen is driven according to the color information (digital signals) stored in the video buffer. 
   In another embodiment, an interfacing method in a mobile telecommunication terminal having a main body and a display includes the steps of converting graphic data into an analog signal and transmitting the analog signal to the display. The graphic data may preferably be formed in the main body. The method also includes the steps of converting the analog signal to a digital signal, and storing the digital signal in a video buffer. The method may also preferably include the step of performing a switching operation to control the transmitting of the analog signal to the display. The step of performing a switching operation may preferably include transmitting a command signal. The step of performing a switching operation may also preferably include transmitting a data signal. The method may also include driving the display based on the digital signal stored in the video buffer. 
   As described above, in the display interface of a mobile telecommunication terminal, the number of signal lines may be reduced. Additionally, by maintaining FPCB width, the pattern width of each signal line may be increased to improve device reliability. Furthermore, surplus signal lines may be allotted to perform other device functions, thereby improving device functionality. Alternatively, the overall width of the FPCB may be reduced to accommodate sophisticated hinge designs and telecommunication terminal designs. 
   The present invention may be particularly suitable for transmitting and receiving data to and from the display using a flexible printed circuit board. The present invention uses an analog video signal to reduce the number of flexible printed circuit board signal lines, which may improve reliability. The display interface may also have a reduced signal line width between the main body and the display. Accordingly, the present invention may improve performance, functionality, and reliability in mobile telecommunication terminals. 
   It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.