Abstract:
The present invention relates to a portable digital device. According to an embodiment, the method comprises a main unit including a display provided on the main unit and a terminal insertion portion; and an auxiliary unit including a terminal portion configured to be electrically connectable to the terminal insertion portion to allow communication between the main unit and the auxiliary unit, the auxiliary unit being configured to control operation of the main unit when being mounted to the main unit, the auxiliary unit being capable of independently reproducing audio and/or video data when being separated from the main unit.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application is related to, and claims priority to, Korean patent application 10-2007-0090122, filed on Sep. 5, 2007, the entire contents of which are hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a portable digital device, and more particularly, to a portable digital device having an auxiliary unit that is separable from a main unit to be portable. 
         [0004]    2. Description of the Related Art 
         [0005]    Along with the development of multimedia technology, the demand on devices for playing back multimedia content is recently increased. Also, in order to easily utilize and appreciate various contents, there are recently proposed various portable devices capable of storing various kinds of multimedia data such that users may play back and utilize such multimedia data anytime at any place. 
         [0006]    An MP3 player, which is a representative example of such devices, plays back music from received audio data. The MP3 player stores music data in a semiconductor memory, so that it can have a small size and also provide sound quality on a level with a CD. 
         [0007]    Meanwhile, in order to cope with users&#39; increased demand for multimedia contents, portable multimedia devices capable of playing back moving picture data such as AVI and MPEG as well as audio data such as MP3 are recently put on the market. A so-called portable multimedia player (PMP) is a representative example of the portable multimedia device. Unlike conventional MP3 players, the PMP may not only play back moving picture data as well as digital audio data such as MP3 but also have a large capacity storage therein, thereby being usefully utilized as a portable storage device. 
         [0008]    However, such a conventional portable multimedia device has the following problems. 
         [0009]    Due to the international trend of digital convergence technology in recent years, products in which various functions of an MP3 player or a PMP are mixed to a single portable digital device come out, but these products cause unexpected inconvenience to users in actual usage because of the increased size or heavy weight of the products. 
         [0010]    In fact, a limit of battery capacity causes battery power to be consumed too early in a portable digital device capable of playing back MP3 or moving picture if its audio and video (A/V) functions are used unrestrictedly. 
         [0011]    In addition, in case of PMP, which is spotlighted as the most advanced mobile device due to strong audio and video functions, it cannot catch up with a MP3 player from the viewpoint of portability. 
         [0012]    Also, a user who desires to use only an MP3 player function on occasions should carry the heavy PMP, which causes large inconvenience from the viewpoint of use. 
       SUMMARY OF THE INVENTION 
       [0013]    The present invention is conceived to solve the aforementioned problems in the prior art. An object of the present invention is to provide a portable digital device, which has an auxiliary unit used not only as a configuration for manipulating the portable digital device but also as a configuration for supporting the portable digital device, wherein the auxiliary unit can be separated from the portable digital device to improve portability thereof. 
         [0014]    According to an aspect of the present invention for achieving the objects, there is provided a portable digital device, which includes a main unit having a display for displaying an operation state provided on one surface thereof and a pivoting portion pivotally installed to one side thereof, wherein the pivoting portion is provided with a terminal insertion portion; and an auxiliary unit coupled to the pivoting portion to rotate together therewith, the auxiliary unit being provided with a terminal portion to be electrically connected to the terminal insertion portion, wherein the auxiliary unit controls operation of the main unit when being mounted thereto and is independently used when being separated from the main unit. 
         [0015]    The terminal insertion portion provided in the pivoting portion may be electrically connected to a main board provided in the main unit. 
         [0016]    The auxiliary unit may be provided with an input portion for controlling operation of the main unit so that the input portion is exposed in the same direction as the display when the auxiliary unit is mounted to the main unit, wherein the auxiliary unit has an earphone hole provided at a side opposite to the terminal portion to output a voice signal to the outside. 
         [0017]    A touch pad may be provided in the input portion to selectively control operation of the main unit or the auxiliary unit. 
         [0018]    A support may be provided at one side surface of the main unit to support the auxiliary unit at a position farthest from a pivot center of the auxiliary unit. 
         [0019]    The support may be made of an elastically deformable material. 
         [0020]    A concave portion and a protrusion inserted into the concave portion may be respectively formed in corresponding surfaces of the support and a body of the auxiliary unit that are in contact with each other. 
         [0021]    An edge of a lower end of the body supported by the support may be formed to be round, and a friction member may be provided at the lower end of the body. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0022]      FIG. 1  is a perspective view showing a preferred embodiment of a portable digital device according to the present invention. 
           [0023]      FIG. 2  is a plan view showing the portable digital device according to the present invention. 
           [0024]      FIGS. 3   a  and  3   c  are perspective views showing operation states of the portable digital device according to the preferred embodiment of the present invention. 
           [0025]      FIGS. 4 and 5  are perspective views showing another embodiment of the portable digital device according to the present invention. 
           [0026]      FIG. 6  is a block diagram of a main unit and an auxiliary unit of the portable digital device according to the present invention. 
           [0027]      FIG. 7  is a flowchart illustrating that the main unit is controlled by the auxiliary unit in the embodiment of the present invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0028]    Hereinafter, preferred embodiments of a portable digital device according to the present invention will be described in detail with reference to the accompanying drawings. 
         [0029]      FIG. 1  is a perspective view showing a preferred embodiment of a portable digital device according to the present invention, and  FIG. 2  is a plan view showing the portable digital device according to the present invention. 
         [0030]    According to the figures, the portable digital device of this embodiment generally includes a main unit  10  and an auxiliary unit  30 . 
         [0031]    The main unit  10  has a function of a PMP widely used in these days. Unlike the auxiliary unit having only a music playback function, the main unit  10  may also play back a moving picture and has a large capacity storage to be usefully utilized as a portable storage device. 
         [0032]    A case  12  defining an external appearance of the main unit  10  has a substantially hexahedral shape. The case  12  is provided with components required for operating the device, such as various memories (ROM and RAM), an interrupt controller and a battery. 
         [0033]    A display  14  having a substantially tetragonal shape is provided in a front surface of the case  12 . The display  14  has a liquid crystal display (LCD) panel and the like provided in the case  12 , and a portion thereof is transparent such that contents displayed on the LCD panel may be viewed on the front of the case  12 . The display  14  displays an operational state of the portable digital device or an image played by the execution of a multimedia file. 
         [0034]    The main unit  10  may have an additional input portion for controlling the operation of the main unit  10 . This input portion may include a touch pad or a button array having buttons for manipulation, and the display  14  may also be used as the input portion. For example, the display  14  may include a touch screen for controlling the operation of the main unit  10 . Generally, a touch screen is configured by providing an LCD panel to a rear surface of a touch glass with electrodes printed or vacuum deposited on a surface thereof. Such a touch screen module may be easily configured by those skilled in the art, so that detailed descriptions thereon will be omitted. 
         [0035]    A speaker  16  is provided at one side of the case  12 . The speaker  16  serves to output a played music or a sound of a moving picture to the outside. Thus, a user may output a voice data through the speaker  16  without any additional voice output device such as an earphone. 
         [0036]    A pivoting portion  18  is rotatably provided at one side of the case  12 . In order to rotate the pivoting portion  18  with respect to the case  12 , certain force should be applied thereto. The auxiliary unit  30 , which will be described later, is connected to the pivoting portion  18 . 
         [0037]    The pivoting portion  18  is connected to the case  12  by a hinge structure using a hinge pin (not shown). Also, the pivoting portion  18  is electrically connected to a main board (not shown) provided in the main unit  10 . For example, a wire for signal connection between a component mounted in the case  12  and a terminal insertion portion (not shown) to be described later passes through the hinge pin. A configuration capable of controlling the rotation of the pivoting portion  18  may be provided in surfaces where the case  12  and the pivoting portion  18  are in contact with each other. 
         [0038]    The terminal insertion portion (not shown) is provided in the pivoting portion  18  such that a terminal portion  34  to be described later may be inserted in the terminal insertion portion. That is, the auxiliary unit  30  is supported by the pivoting portion  18 , and the terminal portion  34  is inserted into the terminal insertion portion to communicate electric signals. 
         [0039]    The terminal insertion portion may include various kinds of interfaces to communicate electric signals, but an interface of universal serial bus (USB) standards generally used in the art will be described as an example thereof in this embodiment. The USB interface may be easily configured by those skilled in the art, so that descriptions thereof will be omitted. 
         [0040]    A support  20  is provided at one side surface of the case  12 . The support  20  is formed at one end opposite to the pivoting portion  18  on the one side surface of the case  12 . The support  20  supports the auxiliary unit  30  connected to the pivoting portion  18 . That is, the support  20  supports one end of the auxiliary unit  30 , which is farthest from the pivoting portion  18  that is a pivot center of the auxiliary unit  30 . The support  20  is preferably provided to be elastically deformable with respect to the case  12 . 
         [0041]    The auxiliary unit  30  is detachably coupled to the pivoting portion  18 . The auxiliary unit  30 , which is a unit for receiving audio data and playing back it as music, stores music data using a semiconductor memory. 
         [0042]    A body  32  configures a framework of the auxiliary unit  30 . The body  32  has a substantial rectangular hexahedral shape and is mounted to the side surface of the main unit  10  to define a part of the external appearance of the main unit  10 . That is, the auxiliary unit  30  is coupled with the main unit  10  to define a part of the external appearance of the portable digital device. The body  32  corresponds to the pivoting portion  18  in size and shape. The body  32  is partially inserted into the pivoting portion  18 . 
         [0043]    The components required for operating the device, such as a battery and a board (PCB) having various memories (ROM and RAM) mounted thereon, are provided in the body  32 . An edge of the body  32  is preferably formed to be round so that a contact surface of the body  32  with the ground can be changed according to an angle of the auxiliary unit  30  when the auxiliary unit  30  is inserted into the main unit  10  to form a standing structure. A friction member with large friction coefficient, such as rubber, may be provided on a lower end of the body  32  to prevent the body  32  from sliding. 
         [0044]    In addition, the lower end of the body  32  is supported by the support  20 . A concave portion  32 ′ and a protrusion  20 ′ inserted thereinto may be elastically deformably provided at corresponding surfaces of the support  20  and the body  32 , which are in contact with each other. This configuration would not allow the body  32  to be easily separated from the support  20 . That is, certain external force should be applied to separate the body  32  from the support  20 . 
         [0045]    The terminal portion  34  is provided at a upper end of the body  32 . The terminal portion  34  is inserted into the terminal insertion portion and then electrically connected to the main board provided in the main unit  10 . The terminal portion  34  includes an interface capable of communicating electric signals in correspondence with the terminal insertion portion, and a USB interface generally used in the art is used as the terminal portion  34  in this embodiment. 
         [0046]    An input portion  36  is provided at one surface of the body  32 . The input portion  36  is exposed in the same direction as the display  14  when the auxiliary unit  30  is mounted to the main unit  10 . The input portion  36  is a portion for controlling the operation of the main unit  10  and the auxiliary unit  30  and receives various instructions for operating the portable digital device. The input portion  36  may include buttons for controlling input or output, but preferably include a touch pad for a light and compact design of the device. 
         [0047]    The input portion  36  selectively controls the operation of the main unit  10  and the auxiliary unit  30 . That is, the input portion  36  controls the operation of the main unit  10  when the auxiliary unit  30  is connected to the main unit  10 , whereas the input portion  36  controls the operation of the auxiliary unit  30  when the auxiliary unit  30  is separated from the main unit  10 . The main unit  10  may include the display  14  of a touch screen type as a separate input means for controlling the operation of the main unit  10 , as described above. 
         [0048]    An earphone hole (not shown) is formed in the lower end of the body  32 , which is opposite to the terminal portion  34 . An earphone jack (not shown) is inserted into the earphone hole so that a voice data or a voice signal of an image data is transmitted to a user. 
         [0049]    Hereinafter, the operation of the portable digital device so configured according to the present invention will be described in detail. 
         [0050]      FIGS. 3   a  and  3   c  are perspective views showing operation states of the portable digital device according to the preferred embodiment of the present invention. 
         [0051]    First, a process of mounting and detaching the auxiliary unit  30  to and from the main unit  10  will be described. The pivoting portion  18  of the main unit  10  is connected to the case  12  in a hinge manner, thereby being rotatable. 
         [0052]    As shown in  FIG. 3   a,  a user rotates the pivoting portion  18  by a predetermined angle clockwise or counterclockwise with respect to the support  20 . The body  32  provided with the terminal portion  34  is arranged so that its upper end is directed to the pivoting portion  18 , and then the upper end is inserted into the pivoting portion  18  in a direction of an arrow A, so that the terminal portion  34  is connected to the terminal insertion portion of the pivoting portion  18 . At this time, a part of the body  32  is completely inserted into the pivoting portion  18 , and the terminal portion  34  is connected to the terminal insertion portion and transmits electric signals thereto. 
         [0053]      FIG. 3   b  shows that the body  32  is partially inserted into the pivoting portion  18 . As such, in a state where the auxiliary unit  30  is connected to the pivoting portion  18 , the auxiliary unit  30  is rotated together with the pivoting portion  18  toward the support  20 . 
         [0054]    If the auxiliary unit  30  is rotated and comes into contact with the protrusion  20 ′, the support  20  starts to be elastically deformed. At this time, the auxiliary unit  30  rotates while overcoming the elastic force of the support  20 , and the protrusion  20 ′ is inserted into the concave portion  32 ′ formed in the auxiliary unit  30 . The auxiliary unit  30  is finally positioned between the pivoting portion  18  and the support  20 . If the body  32  which is inserted into the pivoting portion  18  is supported by the support  20 , the auxiliary unit  30  is fixed to the main unit  10 . Such a state is shown in  FIG. 3   c.    
         [0055]    A user may control the operation of the main unit  10  by manipulating the input portion  36  provided in the auxiliary unit  30 . That is, in a case where the auxiliary unit  30  is connected to the main unit  10 , the operation of the main unit  10  is controlled by the input portion  36  provided in the auxiliary unit  30 . In addition, when only the auxiliary unit  30  is used, the auxiliary unit  30  may be separated from the main unit  10  and then can be potable. When the auxiliary unit  30  is used independently, the operation of the auxiliary unit  30  is also controlled by the input portion  36 . 
         [0056]    In order to separate the auxiliary unit  30 , the auxiliary unit  30  should be rotated. At this time, the protrusion  20 ′ formed on the support  20  comes out of the concave portion  32 ′ formed in the body  32 . In this state, if the auxiliary unit  30  is rotated continuously, the lower end of the body  32  is separated from the support  20 . Also, force is applied in a direction opposite to the arrow A to separate the auxiliary unit  30  from the pivoting portion  18 . 
         [0057]    Such a portable digital device outputs a desired data by modulating various multimedia signals such as voice or image into digital signals, and a user may generally use the device when moving by vehicle such as bus or electric railway. However, as practical use of portable digital devices is increased, a portable digital device may be used in a standing state on a table at home or office for a user to watch a moving picture lecture or inquire information. 
         [0058]    The portable digital device of this embodiment can be used in a standing state using the auxiliary unit  30  when a user watches a broadcast or the like, which will be described below. 
         [0059]    In order to stand the main unit  10  having the auxiliary unit  30  mounted thereto at an optimal angle, the lower surface of the case  12  provided with the support  20  is placed to contact with the ground, as shown in  FIG. 3   c.    
         [0060]    In this state, if the auxiliary unit  30  is rotated together with the pivoting portion  18  clockwise, the support  20  is elastically deformed, and the protrusion  20 ′ comes out of the concave portion  32 ′ formed in the body  32 . In this state, if the auxiliary unit  30  is rotated continuously, the lower end of the auxiliary unit  30  is separated from the support  20  while overcoming the elastic force of the support  20 . 
         [0061]    The auxiliary unit  30  the lower end of which is separated from the support  20  is rotated to make a suitable angle with respect to the main unit  10 . In order to rotate the pivoting portion  18  with respect to the case  12 , certain force should be applied thereto. Thus, if the pivoting portion  18  is rotated, the pivoting portion  18  is not rotated by the self weight of the main unit  10  or the auxiliary unit  30 . 
         [0062]    If the portable digital device is placed on the horizontal plane while the auxiliary unit  30  makes a predetermined angle with respect to the main unit  10  as mentioned above, the main unit  10  is supported by the auxiliary unit  30  as shown in  FIG. 3   b.    
         [0063]    In such a standing state, a user may utilize functions of the main unit  10  by manipulating the input portion  36  provided in the auxiliary unit  30 . The portable digital device having such a standing structure by the auxiliary unit  30  as mentioned above does not need any space for installing am additional support and also ensures convenient manipulations. 
         [0064]    Now, another embodiment of the portable digital device according to the present invention will be described in detail with reference to the accompanying drawings. 
         [0065]      FIGS. 4 and 5  are perspective views showing the other embodiment of the portable digital device according to the present invention. 
         [0066]    In this embodiment, a structure for mounting an auxiliary unit to a main unit is different from the previous embodiment. Detailed description of components identical with those of the embodiment shown in  FIGS. 1 and 2  will be omitted. In this embodiment, reference numerals increased by one hundred are given to the same elements as the previous embodiment 
         [0067]    According to the figures, a portable digital device of this embodiment generally includes a main unit  110  and an auxiliary unit  130 . 
         [0068]    A case  112  defining an external appearance of the main unit  110  has a substantially hexahedral shape. The case  112  is provided with circuit components required for operating the device, such as various memories (ROM and RAM), an interrupt controller and a battery. 
         [0069]    A display  114  having a substantially tetragonal shape is provided in a front surface of the case  112 . The display  114  has an LCD panel and the like provided in the case  112 , and a portion thereof is transparent such that contents displayed on the LCD panel may be viewed on the front of the case  112 . The display  114  displays an operational state of the portable digital device or an image played by the execution of a multimedia file. 
         [0070]    The main unit  110  may have an additional input portion for controlling the operation of the main unit  110 . This input portion may include a touch pad or a button array having buttons for manipulation, and the display  114  may also be used as the input portion. For example, the display  114  may include a touch screen for controlling the operation of the main unit  110 . Generally, a touch screen is configured by providing an LCD panel to a rear surface of a touch glass with electrodes printed or vacuum deposited on a surface thereof. Such a touch screen module may be easily configured by those skilled in the art, so that detailed descriptions thereon will be omitted. 
         [0071]    An insertion space  116  is formed in a lower portion of the case  112  so that the insertion space  116  is open toward the front surface of the case  112 . An entrance  116 ′ is formed in one side of the lower portion of the case  112  where the insertion space  116  is formed. The entrance  116 ′ is formed corresponding to the auxiliary unit  130  to be described later in size and shape so that the auxiliary unit  130  may be inserted therein. 
         [0072]    A display window  117  is formed in the front surface of the case  112  where the insertion space  116  is formed. The display window  117  is formed on an extension plane of the display  114 , thereby communicating with the insertion space  116 . When the auxiliary unit  130  is inserted into the insertion space  116 , an input portion  136  that is formed on a body  132  to be described later is exposed to the outside through the display window  117 . 
         [0073]    A terminal insertion portion  118  is provided at the other side of the lower portion of the case  112  where the insertion space  116  is formed. The terminal insertion portion  118  is electrically connected to a main board (not shown) provided in the main unit  110 . The terminal insertion portion  1   18  may include various kinds of interfaces to communicate electric signals, but an interface of USB standards generally used in the art will be described as an example thereof in this embodiment. A terminal portion (not shown) of the auxiliary unit  130  to be described later is inserted into the terminal insertion portion  118 . 
         [0074]    A fixing slot  120  is elongatedly formed in one side of the case  112  opposite to the terminal insertion portion  118 . The fixing slot  120  communicates with the insertion space  116 . A region of the case  112  around the fixing slot  120  is made of an elastically deformable material. A catching portion  138 , which will be described later, is inserted into the fixing slot  120 . 
         [0075]    An input portion  136  is provided at the body  132  defining an external appearance of the auxiliary unit  130 . When the auxiliary unit  130  is mounted to the main unit  110 , the input portion  136  is exposed to the outside through the display window  117  so that the input portion  130  is oriented in the same direction as the display  114 . The input portion  136  is a portion for controlling the operation of the main unit  110  and the auxiliary unit  130  and receives various instructions for operating the portable digital device. The input portion  136  may include buttons for controlling input or output, but preferably include a touch pad for a light and compact design of the device. 
         [0076]    The terminal portion (not shown) is provided at one end of the body  132  in correspondence to the terminal insertion portion  118 . The terminal portion is inserted into the terminal insertion portion  118  and communicates electric signals between the main unit  110  and the auxiliary unit  130 . 
         [0077]    The catching portion  138  is formed to protrude on one side of the body  132  corresponding to the fixing slot  120 . Both elongated sides of the catching portion  138  are formed with a predetermined slope to form a chamfer  138 ′. The chamfer  138 ′ serves to guide the catching portion  138  into the fixing slot  120  when the body  132  is inserted into the insertion space  116 . Of course, the chamfer  138 ′ also guides the catching portion  138  to be separated from the fixing slot  120  when the body  132  is drawn out of the insertion space  116 . The catching portion  138  serves to fix the body  132  so that the auxiliary  130  may not be easily drawn out of the insertion space  116 . When the auxiliary unit  130  is drawn out of the insertion space  116 , a region around the fixing slot  120  is elastically deformed, so that the body  132  may be separated from the insertion space  116 . 
         [0078]    An earphone hole  140  is formed in the body  132  at a position adjacent to the catching portion  138 . An earphone jack (not shown) is inserted into the earphone hole so that a voice data or a voice signal of an image data is transmitted to a user. 
         [0079]    Hereinafter, the operation of the portable digital device so configured according to the present invention will be described in detail. 
         [0080]    The body  132  of the auxiliary unit  130  is inserted into the open insertion space  116  formed in the main unit  110  through the entrance  116 ′. That is, the end of the body  132  having the terminal portion is inserted into the insertion space  116  opened in the side of the case  112 . 
         [0081]    At this time, the region of the case  112  around the fixing slot  120  is elastically deformed due to the insertion of the body  132 , and the catching portion  138  is guided by the chamfer  138 ′ and inserted into the fixing slot  120 . 
         [0082]    If the catching portion  138  is inserted into the fixing slot  120 , the body  132  is fixed in the insertion space  116 . If the body  132  is completely inserted into the insertion space  116 , the terminal portion is inserted into the terminal insertion portion  118  to communicate electric signals. 
         [0083]    A user may control the operation of the main unit  110  by manipulating the input portion  136  provided in the auxiliary unit  130 . That is, in a case where the auxiliary unit  130  is connected to the main unit  110 , the operation of the main unit  110  is controlled by the input portion  136  provided in the auxiliary unit  130 . In addition, when only the auxiliary unit  130  is used, the auxiliary unit  130  may be separated from the main unit  110  and then can be potable. When the auxiliary unit  130  is used solely, the operation of the auxiliary unit  130  is also controlled by the input portion  136 . 
         [0084]    In order to separate the auxiliary unit  130 , force should be applied to the auxiliary unit  130  in a direction opposite to the inserting direction of the body  132 . At this time, the region around the fixing slot  120  is elastically deformed, and the catching portion  138  is separated from the fixing slot  120 . 
         [0085]    In addition, if the terminal portion is separated from the terminal insertion portion  118 , the main unit  110  and the auxiliary unit  130  are electrically disconnected from each other. The auxiliary unit  130  is finally separated from the insertion space  116  and drawn out. 
         [0086]    A user may carry only the auxiliary unit  130  separated from the main unit  110  and outputs voice data from the auxiliary unit  130 . Since the auxiliary unit  130  may be used as being separated from the main unit  110  having a large capacity battery for playback of an image, there is an advantage in that portability is improved. Of course, if playback of image data is needed, the auxiliary unit  130  may also be used as being mounted to the main unit  110 . 
         [0087]    As described above, in a state where the main unit  10  or  110  is connected to the auxiliary unit  30  or  130 , the auxiliary unit  30  or  130  controls the operation of the main unit  10  or  110 . Hereinafter, a process of controlling the main unit  10  or  110  by the auxiliary unit  30  or  130  will be described in detail with reference to the accompanying drawings. 
         [0088]      FIG. 6  is a block diagram of the main unit and the auxiliary unit of the portable digital device according to the present invention, and  FIG. 7  is a flowchart illustrating that the main unit is controlled by the auxiliary unit in the embodiment of the present invention. 
         [0089]    According to the figures, the main unit  10  or  110  includes a main display  210 , a first controller  220 , a PC I/O interface  225 , a first storage  230 , a first power source  240 , a first input portion  250 , a detection portion  260 , a speaker  270 , and first and second I/O interfaces  280  and  290 . In addition, the auxiliary unit  30  or  130  includes an auxiliary display  310 , a second controller  320 , a second storage  330 , a second power source  340 , a second input portion  350 , a detection portion  360   a,  a switching portion  360   b,  an audio output portion  370 , and a second I/O interface  380 . 
         [0090]    In a state the auxiliary unit  30  or  130  is coupled to the main unit  10  or  110 , the main display  210  of the main unit  10  or  110  displays a list of files to be played back in connection with the second input portion  350 , and also displays a moving picture to a user. An LCD is generally used as the main display  210 . 
         [0091]    The first controller  220  controls playback of various music or moving picture files in a state where the main unit  10  or  110  is separated from the auxiliary unit  30  or  130 . The first storage  230  stores large capacity multimedia data such as text, music, movie files. Such multimedia data are downloaded from a PC  400  through the second I/O interface  290 , which will be described later. 
         [0092]    The first power source  240  corresponds to a main battery of the portable digital device. Thus, the main unit  10  or  110  is driven by the first power source  240  when the auxiliary unit  30  or  130  is coupled to the main unit  10  or  110 , while the second power source  340  independently supplies the auxiliary unit  30  or  130  with power when the auxiliary unit  30  or  130  is separated from the main unit  10  or  110 . 
         [0093]    In addition, a user makes key input through the first input portion  250 , and the detection portion  260  detects whether the auxiliary unit  30  or  130  is coupled or separated. Also, the speaker  270  takes charge of outputting voice signals. 
         [0094]    The first and second I/O interfaces  280  and  290  serve to allow various control signals and power lines for control of the main unit  10  or  110  to be received from and transmitted to the auxiliary unit  30  or  130  and the PC  400  through the I/O interfaces. 
         [0095]    Then, the auxiliary display  310  displays a music file or the like to be played back by the auxiliary unit  30  or  130 . An LCD is generally used as the auxiliary display  310 . 
         [0096]    The second controller  320  allows a file to be played back or audio data to be output to the main unit  10  or  110  through the second I/O interface  380  in a state where the auxiliary unit  30  or  130  is coupled with the main unit  10  or  110 . Of course, in a state where the auxiliary unit  30  or  130  is separated from the main unit  10  or  110 , the second controller  320  controls the playback of a file in the auxiliary unit  30  or  130 . 
         [0097]    The second storage  330  stores audio files, programs related to initialization of the portable digital device and various application programs unlike the first storage  230  with a large capacity. 
         [0098]    The second power source  340  supplies power to the auxiliary unit  30  or  130  in a state where the auxiliary unit  30  or  130  is separated from the main unit  10  or  110 . 
         [0099]    A user makes key input through the second input portion  350 . In addition, the detection portion  360   a  and the switching portion  360   b  serve to detect the connection between the main unit  10  or  110  and the auxiliary unit  30  or  130 . If the auxiliary unit  30  or  130  is separated from the main unit  10  or  110 , the detection portion  360   a  and the switching portion  360   b  detect the separation and transmits a corresponding signal to the second controller  320  and are also supplied with necessary power from any one of the power sources  240  and  340 . 
         [0100]    Meanwhile, the audio output portion  370  outputs an audio data file stored in the second storage  330 . That is, the audio output portion  370  outputs an audio data file when the auxiliary unit  30  or  130  is separated. 
         [0101]    According to such a configuration, the detection portion  360   a  of the auxiliary unit  30  or  130  detects whether the main unit  10  or  110  is connected (Step S 10 ). According to the detection of the detection portion  360   a,  the switching portion  360   b  informs the second controller  320  of whether the auxiliary unit  30  or  130  is connected to the main unit  10  or  110 . 
         [0102]    If the detection portion  360   a  detects the connection to the main unit  10  or  110 , a user is allowed to make key input through the second input portion  350  (S 20 ). The information input through the second input portion  350  should be not used for operating the auxiliary unit  30  or  130  but transmitted to the main unit  10  or  110 . That is, the second controller  320  transmits an audio data or the like of the second storage  330  to the main unit  10  or  110  through the second I/O interface  380  (Step S 30 ). 
         [0103]    Information of audio data or the like is transmitted to the first I/O interface  280  through the second I/O interface  380 , and the audio data transmitted to the first I/O interface  280  is output through the speaker  270 . In addition, if a stop instruction is input to the second input portion  350  by a user, the second controller  320  outputs the stop instruction to the main unit  10  or  110  through the first and second I/O interfaces  280  and  380 , thereby making the speaker  270  stop its outputting operation (Step S 40 ). 
         [0104]    If the detection portion  360   a  of the auxiliary unit  30  or  130  detect that the main unit  10  or  110  is not detected (Step S 10 ), the user is allowed to make key input through the second input portion  350  (Step S 50 ). Then, the second controller  320  outputs an audio data or the like of the second storage  330  through the audio output portion  370  (Step S 60 ). 
         [0105]    According to the embodiment, the auxiliary unit can be separated from the main unit, which is large in weight and volume due to a large capacity battery, and then used alone as required, so that there is an advantage in that portability is improved. 
         [0106]    In addition, the portable digital device of the embodiment, in which the auxiliary unit is rotatably coupled to the main unit, may allow the auxiliary unit to be rotated together with the pivoting portion connected to the main unit and thus can stand on a table or the like, thereby enhancing convenience to a user. 
         [0107]    The scope of the embodiment is not limited to the embodiments described above but is defined by the appended claims. It will be apparent that those skilled in the art can make various modifications and changes thereto within the scope of the invention defined by the claims.