Abstract:
The present invention discloses a function extending apparatus detachably connected to an electronic apparatus to enhance functions of the electronic apparatus, the function extending apparatus including a connection control part controlling a connection between a battery and a charging part in accordance with a result of detection of docking to the electronic apparatus so as to supply power from the electronic apparatus to the battery.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention generally relates to function extending apparatuses, electronic apparatuses and electronic systems, and more particularly to a function extending apparatus, an electronic apparatus and an electronic system in which functions of the electronic apparatus are enhanced by attaching the function extending apparatus thereto. 
     Recently, as computers are being developed quickly and becoming widespread, it is more preferable to produce minimized and lightweight portable computers and to realize an increased variety of functions. In other words, in general, in a case of using a part of a computer system as a portable machine, just the most essential functions and minimized lightweight portability are required. On the other hand, in a case of using the same computer as a desktop, it is required that the computer system can realize a maximum variety of functions by a function extending apparatus. 
     To realize the above-mentioned computer system, a portable personal computer (PC) which has just the most essential needed functions, such as a notebook computer, and a function extending apparatus extending the PC&#39;s functions by attaching to the portable PC are provided. 
     The extended station requires a large power consumption when the extended station is attached to the portable PC in order to extend functions. In this case, internal batteries mounted in the portable PC are not enough to operate the extended station and enhance functions. Thus, when the extended station is needed, external power is required. 
     2. Description of the Related Art 
     FIG.1 shows a diagram illustrating an example of a construction of a conventional electronic system. 
     Conventionally, an electronic system  1  such as an information processor system includes a notebook PC  10  having essential functions and an extended station  20  that is used with the notebook PC  10  to enhance its functions. 
     The extended station  20  is mounted to a bottom surface of the notebook PC  10  by connecting a connector  21  with a connector  11  of the notebook PC  10 . The extended station  20  includes a floppy disk drive  22  to record or read data stored in a floppy disk  30  and a CD-ROM drive  23  to read data from a CD-ROM  40 . The notebook PC  10  does not include any of a floppy disk drive, a CD-ROM drive and a stereo speaker  24 , which require much power consumption. The notebook PC  10  however extends its functions to operate the floppy disk drive  22 , the CD-ROM drive  23  and a stereo speaker  24  by attaching to the extended station  20 . 
     In this case, power for both of the notebook PC  10  and the extended station  20  is supplied by using an AC adapter  50  or an internal battery pack  12  mounted in the notebook PC  10 . 
     In the conventional electronic system  1 , when the extended station  20  is connected to the notebook PC  10 , power is supplied and then the functions of the notebook PC  10  are enhanced. In this case, when the notebook PC  10  supplies power only by the internal battery pack  12 , the extended station  20  consumes power quickly. Thus, a total operating time is shortened. The internal battery pack  12  can not practically supply power for a whole computer system. Thus, it is required to use the AC adapter  50  as a main power supplier, which limits usage of the electronic system. 
     In addition, the extended station  20  itself without the notebook PC  10  does not have any effective function. 
     SUMMARY OF THE INVENTION 
     It is a general object of the present invention to provide a function extending apparatus, an electronic apparatus and an electronic system in which the above-mentioned problems are eliminated. 
     A more specific object of the present invention is to provide a function extending apparatus, an electronic apparatus and an electronic system in which functions of the electronic apparatus can be enhanced, power can be supplied to the electronic apparatus, and batteries mounted in the function extending apparatus and the electronic apparatus can be charged by the supplied power. 
     The above objects of the present invention are achieved by a function extending apparatus detachably connected to an electronic apparatus to enhance functions of the electronic apparatus, the function extending apparatus including: an area for accommodating a battery supplying power to the electronic apparatus; a charging part receiving external sources, one of which comes from the electronic apparatus, and charging the battery; a docking detecting part detecting a connection to the electronic apparatus; and a connection control part controlling a connection between the battery and the charging part in accordance with a result of detection by the docking detection part so as to supply power from the electronic apparatus to the battery. 
     According to the present invention, it is possible to charge the battery by connecting the charging part with the battery when the function extending apparatus is not attached to the electronic apparatus. Moreover, it is possible to supply power from the battery to the electronic apparatus when the function extending apparatus is attached to the electronic apparatus. 
     Further, the above objects of the present invention are achieved by an electronic apparatus detachably connected to a function extending apparatus that is used to enhance functions of the electronic apparatus, the electronic apparatus including: an area for accommodating a first battery; and a charging part receiving power from the function extending apparatus, and charging the first battery. 
     According to the present invention, it is possible to charge the first battery mounted in the electronic apparatus by supplying power form the function extending apparatus when the electronic apparatus is attached to the function extending apparatus. 
     Furthermore, the above objects of the present invention are achieved by an electronic system in which functions of an electronic apparatus are enhanced by attaching the electronic apparatus to a function extending apparatus providing more functions, the electronic system including: a first battery supplying power to the electronic apparatus, the first battery detachably connected to the electronic apparatus; and a second battery supplying power to the function extending apparatus, the second battery detachable connect to the function extending apparatus, wherein the first battery and the second battery are interchangeable. 
     According to the present invention, it is possible to substitute the second battery for the first battery and the reverse is also true. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings, in which: 
     FIG. 1 shows a diagram illustrating an example of a construction of a conventional electronic system; 
     FIG. 2 shows a diagram illustrating an electronic system according to the embodiment of the present invention; 
     FIG. 3 shows a perspective diagram illustrating the notebook PC of the electronic system according to the embodiment of the present invention; 
     FIG. 4 shows a diagram illustrating an example of an operation state display part of the electronic system according to the embodiment of the present invention; 
     FIG. 5A shows a left side view of the notebook PC of the electronic system according to the embodiment of the present invention and FIG. 5B shows a right side view of the notebook PC of the electronic system according to the embodiment of the present invention; 
     FIG. 6A shows a rear elevation of the notebook PC of the electronic system according to the embodiment of the present invention and FIG. 6B shows a bottom view of the notebook PC of the electronic system according to the embodiment of the present invention; 
     FIG. 7 is a perspective view from a front side of an extended station according to the embodiment of the present invention; 
     FIG. 8 is a perspective view from a rear side of the extended station according to the present invention; 
     FIG. 9A is a perspective view of a bottom surface of a battery pack in a look-up direction, according to the embodiment of the present invention and FIG. 9B is a perspective view of the battery pack that is turned over, according to the embodiment of the present invention; 
     FIG. 10 is a perspective view of the battery pack according to the embodiment of the present invention; 
     FIG. 11 shows a diagram for explaining how the battery pack is mounted and removed, according to the embodiment of the present invention; 
     FIG. 12 shows a diagram for explaining the operation of mounting the notebook PC  101  on the extended station  102 , according to the embodiment of the present invention; 
     FIG. 13 shows a diagram for explaining an operation when extended functions are used according to the embodiment of the present invention; 
     FIG. 14 shows a diagram for explaining the operation of detaching the notebook PC from the extended station, according to the embodiment of the present invention; and 
     FIG. 15 shows a diagram illustrating a circuit construction of a power supply system according to the embodiment of the present invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 2 shows a diagram illustrating an electronic system according to an embodiment of the present invention. 
     The electronic system  100  according to the embodiment of the present invention includes a notebook PC  101  corresponding to the electronic apparatus in the claims, an extended station  102  corresponding to the function extending apparatus in the claims, a battery pack  103  corresponding to the first battery or the second battery in the claims, a compact bay  104 , and an external floppy disk drive unit  105 . Moreover, the electronic system  100  is connectable to a color CRT display  106 , a printer  107 , an extended keyboard  108  and a mouse  109 . Also, the electronic system  100  is connectable to a PC card that is in conformity to the PCMCIA standard such as an SCSI card  110 , an IC memory card  111 , a LAN card  112  or the like. 
     The notebook PC  101  will now be explained with reference to FIGS. 3,  4 ,  5 A,  5 B,  6 A and  6 B. 
     FIG. 3 shows a perspective diagram illustrating the notebook PC of the electronic system according to the embodiment of the present invention. 
     FIG. 4 shows a diagram illustrating an example of an operation state display part of the electronic system according to the embodiment of the present invention. 
     FIG. 5A shows a left side view of the notebook PC of the electronic system according to the embodiment of the present invention. FIG. 5B shows a right side view of the notebook PC of the electronic system according to the embodiment of the present invention. 
     FIG. 6A shows a rear elevation of the notebook PC of the electronic system according to the embodiment of the present invention. FIG. 6B shows a bottom view of the notebook PC of the electronic system according to the embodiment of the present invention. 
     In FIG. 5A, the notebook PC  101  includes a base unit  113  and a flat-panel display  114  that is pivotable in an A 1  direction or an A 2  direction. The flat-panel display  114  is pivoted in the A 1  direction to a closed position when the notebook PC  101  is carried. As shown in FIG. 5B, the flat-panel display  114  attaches to the base unit  113  so that the notebook PC  101  becomes handy to carry. 
     When the notebook PC  101  is used, the flat-panel display  114  is pivoted in the A 2  direction to an opened position so that the base unit  113  and the flat-panel display  114  become available for use as shown in FIG.  5 A. 
     In a state of being available for use as shown in FIG. 5A, a keyboard  115  and a pointing device  116  are positioned on the top surface of the base unit  113 , as shown in FIG. 3, so that a pointer P on the flat-panel display  114  can be operated by the pointer device  116  and a command or data can be input from the keyboard  115 . In addition, an operation state display  117  is positioned at an upper-most position on the surface of the base unit  113 . 
     The operation state display  117  shows an operation state of the notebook PC  101 . 
     The operation state display  117  is composed of an LCD (Liquid Crystal Display). As shown in FIG. 4, the operation state display  117  includes a SUS/RES display  117   a , an AV adapter  117   b , battery pack mounting state displays  117   c  and  117   d , battery charging state displays  117   e  and  117   f , battery capacity displays  117   g  and  117   h , a CD-ROM drive access display  117   i , a hard disk access display  117   j , a floppy disk access display  117   k , a PC card access display  117   m , a number lock display  117   n , a caps lock display  117   o , and a scroll lock display  117   p.    
     The SUS/RES display  117   a  is turned on when the notebook PC  101  operates, blinked when the notebook PC  101  is suspended, and turned off when the notebook PC  101  is turned off. 
     The AC adapter display  117   b  is turned on when power is supplied from the AC adapter. 
     The battery pack mounting state display  117   c  is turned on when the internal battery pack  103  is mounted in the base unit  113 . Also, the battery pack mounting state display  117   d  is turned on when the internal battery pack  103  is mounted in the extended station  102  or the compact bay  104 . 
     The battery charging state display  117   e  is turned on when the battery pack  103  mounted in the base unit  113  is being charged. Also, the battery charging state display  117   f  is turned on when the battery pack  103  mounted in the extended station  102  or the compact bay  104  is being charged. 
     The battery capacity display  117   g  indicates available capacity of the battery pack  103  mounted in the base unit  113 . The battery capacity display  117   h  indicates available capacity of the battery pack  103  mounted in the extended station  102  or the compact bay  104 . 
     The CD-ROM drive access display  117   i  is turned on when a CD-ROM drive  149  mounted in the extended station  102  or the compact bay  104  is accessed. 
     The hard disk access display  117   j  is turned on when an internal hard disk built in the base unit  113  or the hard disk mounted in the compact bay  104  is accessed. 
     The floppy disk access display  117   k  is turned on when the external floppy disk drive unit  105 , an internal floppy disk drive mounted in the extended station  102  or a hard disk mounted in the compact bay  104  is accessed. 
     The PC card access display  117   m  is turned on when a PC card, which is inserted in a PC card slot  126  provided in the base unit  113 , is accessed. 
     The number lock display  117   n  is turned on when the keyboard is set in a ten-key mode. The caps lock display  117   o  is turned on when all letters are set to be capital. The scroll lock display  117   p  is turned on when a scroll lock key is operated. 
     A power switch  118  is provided at the left side of the base unit  113  as shown in FIG.  5 A. The operation of the notebook PC  101  is turned on when the power switch is turned “ON”. 
     In addition, a sound volume control  119 , a headphone jack  120 , a microphone jack  121 , a line-in jack  122 , a burglarproof lock  123 , a modular connector  124 , a PC card lock  125 , the PC card slot  126 , and a PC card lock  127  are provided on the right side of the base unit  113  as shown in FIG.  5 B. 
     Sound volume is adjusted by operating the sound volume control  119 . 
     A headphone is connected to the headphone jack  120 . 
     A microphone is connected to the microphone jack  121 . 
     A sound input connector is connected to the line-in jack  122  so as to input sound signals from an external device. 
     A burglarproof cable is connected to the burglarproof lock  123 . 
     A telephone line connector jack is connected to the modular connector  124 . 
     A PC card such as the SCSI card  110 , the IC memory card  111  or the LAN card  112  is connected to the PC card slot  126 . 
     A PC card inserted in the PC card slot  126  is locked by the PC card lock  127 . 
     On the rear side of the base unit  113  as shown in FIG. 6A, an infrared communication port  128 , a USB connector  129 , a connector  130  for the extended keyboard or the mouse, a floppy disk unit connector  131 , a serial connector  132 , a parallel interface connector  133 , a CRT interface connector  134  and a DC-IN connector  135  are provided. 
     The infrared communication port  128  is an interface between infrared communication and the notebook PC  101 . 
     A peripheral device, which is in conformity to the USB (Universal Serial Bus) standard, is connected to the USB connector  129 . 
     The extended keyboard  108  or the mouse  109  is connected to the connector  130 . 
     The floppy disk drive unit  105  is connected to the floppy disk unit connector  131 . 
     A device, which connector is in conformity to the RS232C standard, is connected to the serial connector  132 . 
     The printer  107  is connected to the parallel interface connector  133 . 
     The color CRT display  106  is connected to the CRT connector  134 . 
     The AC adapter  50  is connected to the DC-In connector  135 . 
     Moreover, on the bottom surface of the notebook PC  101  as shown in FIG. 6B, a connector cover  136 , an extended unit connector  137 , an extended RAM module slot  138 , an internal battery pack lock  139 , an unlock button  140 , an internal battery pack slot  141  and an internal hard disk slot  142  are provided. 
     The above-mentioned connectors in FIG. 6A are covered with the connector cover  136 . 
     The extended station  102  or the compact bay  104  is connected to the extended unit connector  137 . 
     An extended RAM module is set in the extended RAM module slot  138 . 
     The internal battery pack lock  139  locks the internal battery pack  103  in the battery pack slot  141  when the internal battery pack  103  is set therein. 
     When the unlock button  140  is pushed, the internal battery pack lock  139  is unlocked. 
     The internal battery pack  103  is mounted in the internal battery pack slot  141 . 
     The internal hard disk unit  143  is mounted in the internal hard disk slot  142 . 
     A liquid crystal display  144  is provided on the inside of the flat-panel display  114  so as to face the base unit  113 . 
     In order to process information, the base unit  113  includes a CPU, a RAM, a ROM, interface circuits, and communication circuits. 
     The extended station  102  will now be explained. 
     FIG. 7 is a perspective view from a front side of the extended station according to the embodiment of the present invention. FIG. 8 is a perspective view from a rear side of the extended station according to the present invention. 
     As shown in FIG. 7, on the top side, the front side and the right side, the extended station  102  includes an internal battery pack slot  145 , an internal battery pack lock  146 , a connector  147 , a connector lock  148 , a CD-ROM drive  149 , an eject button  150 , a detach button  151 , a detach permission lamp  152 , a floppy disk drive  153 , a floppy disk eject button  154 , a PC card slot  155  and a detach lever  156 . 
     The battery pack  103  is mounted into the internal battery pack slot  145 . The internal battery pack lock  146  locks the battery pack  103  in the internal battery pack slot  145 . 
     The connector  147  is connected to the extended unit connector  137  provided on the bottom surface of the base unit  113 . The connector lock  148  is engaged with an engaging member that is provided on the bottom surface of the base unit  113 . Thus, the base unit  113  is mechanically engaged with the extended station  102 . 
     The CD-ROM  157  is set in the CD-ROM drive  149 . Then, the CD-ROM drive  149  operates the CD-ROM  157  to read information recorded thereon. The CD-ROM  157  is ejected from the CD-ROM drive  149  by pushing the eject button  150 . 
     By pushing the detach button  151 , the extended station  102  is detached from the notebook PC  101 . The detach permission lamp  152  is composed of an LED so that the detach permission lamp  152  is ‘ON’ when the notebook PC  101  is ready to detach the extended station  102 . The detach lever  156  is operated to detach the extended station  102  from the notebook PC  101 . The notebook PC  101  is mechanically disconnected from the extended station  102  by the detach lever  156 . 
     The floppy disk  158  is set in the floppy disk drive  153 . The floppy disk drive  153  operates the floppy disk  158  to write and/or read information recorded thereon. By pushing the floppy disk eject button  154 , the floppy disk  158  is ejected from the floppy disk drive  153 . 
     The PC card  159  is set in the PC card slot  155 . 
     As shown in FIG. 8, on the rear side and the left side, the extended station  102  includes a burglarproof lock  160 , a security lock  161 , a LAN connector  162 , an USB connector  163 , an extended keyboard connector  164 , a mouse connector  165 , a serial connector  166 , a sound output terminal  167 , an image output terminal  168 , a parallel connector  169 , a CRT connector  170 , a DC-IN connector  171 , and a ventilating hole  172 . 
     A burglarproof cable is connected to the burglarproof lock  160 . The security lock  161  locks the burglarproof lock  160  to the burglarproof cable when the burglarproof cable is fixed to the burglarproof lock  160 . 
     A LAN cable is connected to the LAN connector  162 . A peripheral, which interface is in conformity to the USB standard, is connected to the USB connector  163 . 
     The extended keyboard connector  164  is used to connect the extended keyboard  108 . The mouse connector  165  is used to connect the mouse  109 . 
     The serial connector  166  is used to connect a device which interface is in conformity to the RS-232C standard. 
     The sound output terminal  167  is used to connect a sound speaker or the like in order to output stereo sound. 
     The image output terminal  168  is used to connect a television set or the like in order to display an image. 
     The parallel connector  169  is used to connect a peripheral, which has a parallel port, such as a printer or the like. 
     The CRT connector  170  is used to connect the CRT display  106 . 
     The DC-IN connector  171  is used to connect an AC adapter in order to externally supply power. 
     The ventilating hole  172  ventilates heat generated inside of the extended station  102 . 
     The extended station  102  according to the embodiment supplies power from the AC adapter and also supplies power from the battery pack  103  mounted in the internal battery pack slot  145 . In addition, while the extended station  102  is supplying power, the battery pack  103  mounted in the internal battery pack slot  145  can be charged. 
     The battery pack  103  will now be explained with reference to FIGS. 9A and 9B. 
     FIG. 9A is a perspective view of a bottom surface of the battery pack in a look-up direction, according to the embodiment of the present invention. FIG. 9B is a perspective view of the battery pack that is turned over, according to the embodiment of the present invention. 
     As shown in FIGS. 9A and 9B, the battery pack  103  has a rectangular board shape and a cut-off portion  173 . On a side surface indicated by a Y 1  direction, a terminal  174  is provided so as to electrically connect with the notebook PC  101 , the extended station  102 , or the compact bay  104 . On the side surface indicated by the Y 1  direction and a side surface indicated by a Y 2  direction, engaging members  175  and  176  in FIG.  9 A and engaging members  177 ,  178 ,  179  in FIG. 9B are provided. The engaging members  175 ,  176 ,  177 ,  178  and  179  are brought into engagement with the battery slot  141  or  145  when the battery pack  103  is mounted in the notebook PC  101 , the extended station  102  and the compact bay  104  so that the battery pack  103  is electrically connected with the battery slot  141  or  145 . 
     FIG. 10 is a perspective view of the battery pack  103  according to the embodiment of the present invention. 
     Both of the battery slots  141  and  145  for the notebook PC  101 , the extended station  102  and the compact bay  104  fit the shape of the battery pack  103 . 
     As shown in FIG. 10, each of the battery slots  141  and  145  includes a recess portion  180 , a contact portion  181 , a plurality of engaging members  182 , and the internal battery locks  139  and  146 . 
     The recess portion  180  is formed on a top surface or a bottom surface of the notebook PC  101 , the extended station  102  and the compact bay  104  and also has the same shape as the battery pack  103 . 
     The contact portion  181  is connected with the terminal  174  of the battery pack  103  when the battery pack  103  is mounted in the recess portion  180 . 
     The plurality of engaging members  182  are provided at two positions on the side surface indicated by the Y 1  direction and at three positions on the other side surface indicated by the Y 2  direction. Accordingly, the five engaging members  182  are brought into engagement with the engaging members  175 ,  176 ,  177 ,  178  and  179 , respectively, when the battery pack  103  is mounted in the recess portion  180 . The engaging members  182  lock or unlock the battery pack  103  by operating the internal battery lock  139  and  146  in an X 1  direction or in an X 2  direction. When the battery pack  103  is unlocked, that is, when the engaging members  182  are brought out of engagement with the engaging members  175 ,  176 ,  177 ,  178  and  179 , the battery pack  103  can be removed from the battery pack slot  141  or  145 . 
     FIG. 11 shows a diagram for explaining how the battery pack  103  is mounted and removed, according to the embodiment of the present invention. 
     In order to insert the battery pack  103  into the battery pack slot  141  or  145 , the battery pack  103  is inserted from a direction indicated by an arrow  183  such that a side surface of the battery pack  103 , on which the cut-off portion  173  is provided, fits a corresponding side surface of the recess portion  180 . 
     While the side surface having the cut-off portion  173  of the battery pack  103  fits the corresponding side surface of the recess portion  180 , the other side of the battery pack  103  is pushed into the recess portion  180  in a direction indicated by an arrow  184 . 
     An operation of mounting the notebook PC  101  on the extended station  102  will now be explained. 
     FIG. 12 shows a diagram for explaining the operation of mounting the notebook PC  101  on the extended station  102 , according to the embodiment of the present invention. 
     When the notebook PC  101  is mounted in the extended station  102 , as shown in FIG. 12, the notebook PC  101  is pushed in a direction  185  so as to position a front side of the notebook PC  101  at a topmost position of a front side of the extended station  102  and then a bottom surface of the notebook PC  101  is attached to the extended station  102  in a direction  186 . When the notebook PC  101  is attached to the extended station  102 , the connector lock  148  of the extended station  102  is brought into engagement with the notebook PC  101  and also the connector  137  of the notebook PC  101  is connected to the connector  147  of the extended station  102 . 
     When attachment of the notebook PC  101  to the extended station  102  is completed, the notebook PC  101  automatically recognizes functions enhanced by the extended station  102 , such as the CD-ROM drive  149 , the floppy disk drive  153  and the PC card slot  155 . Thus, the notebook PC  101  can access the enhanced functions provided by the extended station  102  as if the enhanced functions are provided by the notebook PC  101  itself. 
     FIG. 13 shows a diagram for explaining an operation when the enhanced functions are used according to the embodiment of the present invention. 
     As shown in FIG. 13, by attaching the notebook PC  101  to the extended station  102 , for example, when the eject button  150 , which is provided for the CD-ROM drive  149  of the extended station  102 , is pushed, a tray  189  is pushed out from the front of the extended station  102  in a direction B 1  so that the CD-ROM  157  may be put on the tray  189  and then the CD-ROM  157  is mounted in the CD-ROM drive  149  by pushing the tray  189  into the CD-ROM drive  149  in a direction B 2 . In a condition in which the CD-ROM  157  is mounted, the notebook PC  101  can read information recorded on the CD-ROM  157  by executing a read instruction to the CD-ROM  157  as if the operation of the CD-ROM drive  149  is a part of functions of the notebook PC  101 . 
     An operation of detaching the notebook PC  101  from the extended station  102  will now be explained. 
     FIG. 14 shows a diagram for explaining the operation of detaching the notebook PC from the extended station, according to the embodiment of the present invention. 
     Referring to FIG. 4, by pushing the detach button  151  provided on the extended station  102 , a detaching process is executed by the notebook PC  101 . After executing the detaching process, the detach permission lamp  152  is turned on. 
     The end of the detach lever  156  is fixed to the extended station  102  and another end of the detach lever  156  is free to push and pull. After the detach permission lamp  152  is turned on, when the end of the detach lever  156  is pulled in a direction c, the connector lock  148 , which is provided on the extended station  102  as shown in FIG. 12, is brought out of engagement with the notebook PC  101 . 
     After the connector lock  148  is brought out of engagement with the notebook PC  101 , when the rear side of the notebook PC  101  is lifted up in a direction  188 , the extended unit connector  137  provided on the bottom of the notebook PC  101  in FIG. 6B is released from the connector  147  provided on the extended station  102  in FIG.  7 . Consequently, the notebook PC  101  is detached from the extended station  102 . 
     FIG. 15 shows a diagram illustrating a circuit construction of a power supply system according to the embodiment of the present invention. 
     The power supply system of the notebook PC  101  is constructed of a charging circuit  201 , an internal power source  202 , an IC chip  203 , switches  204 ,  205  and  206 , a battery selector  207 , a voltage detecting circuit  208 , and reverse-blocking diodes D 1 , D 2  and D 3 . 
     The charging circuit  201  is connected to the DC-IN connector  135  in FIG.  6 A. The charging circuit  201  generates a first charging voltage and a second charging voltage from a power source which the AC adapter  50  in FIG. 2 supplies to the DC-IN connector  135  in FIG.  6 A. The charging circuit  201  is also connected to the IC chip  203  that controls charging of or discharge a battery pack  103   a  or  103   b  sequentially or simultaneously. The IC chip  203  supplies a charge-on signal or a charge-off signal to the charging circuit  201 . 
     When the charge-on signal is supplied to the charging circuit  201  from the IC chip  203 , the charging circuit  201  generates and outputs the first charging voltage and the second charging voltage. When the charge-off signal is supplied to the charging circuit  201  from the IC chip  203 , the charging circuit  201  stops generating and outputting the first charging voltage and the second charging voltage. 
     The internal power source circuit  202  connects to the DC-IN connector  135  through the reverse-blocking diode D 1 . Power is also supplied to the internal power source circuit  202  from the battery pack  103   a  mounted in the notebook PC  101  through the diode D 2 , and the battery pack  103   b  mounted in the extended station  102  through the diode D 3 , and further supplied from an AC adapter  50  of the extended station  102  through the connector  137  as shown in FIG.  6 B. The internal power source circuit  202  is operated in accordance with a direct voltage from the AC adapter  50  or from the battery packs  103   a  and  103   b . Then, the notebook PC  101  is operated. 
     The IC chip  203  connects to a voltage detecting terminal Vsense 1  of the battery pack  103   a  mounted in the notebook PC  101  and a voltage detecting terminal Vsense 2  of the battery pack  103   b  mounted in the extended station  102 . The IC chip  203  supplies a charge-off signal to the charging circuit  201  when voltage of the voltage detecting terminal Vsense 1  or Vsense 2  is greater than a predetermined voltage. Conversely, when the voltage of the voltage detecting terminal Vsense 1  or Vsense 2  is less than the predetermined voltage, the IC chip  203  supplies the charge-on signal to the charging circuit  201 . Moreover, when the IC chip  203  outputs the charge-on signal, the IC chip  203  also outputs a charge-discharge type signal to the battery packs  103   a  and  103   b  in order to control a serial charging/discharging or a parallel charging/discharging. The charge-discharge type signal is defined beforehand. The charge-discharge type signal, which is output from the IC chip  203 , is supplied to the battery selector  207 . 
     Supply of battery voltages of the battery packs  103   a  and  103   b  is turned on and off by internal switches sw 1  and sw 2  provided in the battery packs  103   a  and  103   b , respectively. The internal switches sw 1  and sw 2  are controlled by control terminals Scont 1  and Scont 2 . Switches  204  and  205  control supply of the first charging voltage and the second charging voltage from the charging circuit  201  to the battery packs  103   a  and  103   b . The selector  207  connects to the control terminals Scont 1  and Scont 2  and also connects to the switches  204  and  205 . Accordingly, the battery selector  207  controls the internal switches sw 1  and sw 2  of the battery packs  103   a  and  103   b , and the switches  204  and  205  in accordance with the charge-discharge type signal supplied by the IC chip  203 . 
     When the charge-discharge type signal supplied by the IC chip  203  indicates ‘serial’, the battery selector  207  turns on the internal switch sw 1  of the battery pack  103   a  and the switch  204  controlling supply of the first charging voltage. Simultaneously, the battery selector  207  turns off the internal switch sw 2  of the battery pack  103   b  and the switch  205  controlling supply of the second charging voltage. Accordingly, power is supplied to the battery pack  103   a  until the battery selector  207  receives a next control signal the IC chip  203 . When the next control signal is supplied to the IC chip  203 , the battery selector  207  turns off the internal switch sw 1  of the battery pack  103   a  and the switch  204 . Simultaneously, the battery selector  207  turns on the internal switch sw 2  of the battery pack  103   b  and the switch  205 . Accordingly, power is supplied to the battery pack  103   b . In this manner, power is sequentially supplied to the battery pack  103   a  first and the battery pack  103   b  next. 
     The battery selector  207  includes a flag F that defines a priority order of batteries to charge or discharge power. For example, when the flag F is ‘ON’, the battery selector  207  controls switches to supply power to the battery pack  103   a  first and then the battery pack  103   b  next. And, in this case, the battery pack  103   b  is discharged first and then the battery pack  103   a  is discharged next. Conversely, when the flag F is ‘OFF’, the battery selector  207  controls switches to supply power to the battery pack  103   b  first and then the battery pack  103   a  next. And, in this case, the battery pack  103   a  is discharged first and then the battery pack  103   b  is discharged next. In this embodiment, the flag F is set to ‘ON’ beforehand. Alternately, for example, it may be modified such that the flag F can be selectively set at setup by a user. 
     When the charge-discharge type signal supplied by the IC chip  203  indicates ‘parallel’, the battery selector  207  turns on the internal switch sw 1  of the battery pack  103   a , the internal switch sw 2  of the battery pack  103   b  and the switches  204  and  205  at the same time. Thus, power is supplied to the battery packs  103   a  and  103   b  simultaneously. Further, the battery selector  207  turns off the internal switches sw 1  and sw 2  and the switches  204  and  205  at the same time so that the battery packs  103   a  and  104   b  are ready to discharge. 
     A charge-discharge terminal BATT 1  of the battery pack  103   a  is connected to the internal power source circuit  202  through the diode D 2  and supplies the first charging voltage of the charging circuit  201 . Also, a charge-discharge terminal BATT 2  of the battery pack  103   b  is connected to the internal power source circuit  202  through the diode D 3  and supplies the second charging voltage of the charging circuit  201 . 
     In a case in which power is supplied only from the DC-IN connector  171  of the extended station  102 , the voltage detecting circuit  208  detects a voltage indicating that power is being supplied to the internal power source circuit  202  from the DC-IN connector  171  of the extended station  102 . In accordance with the detected voltage, the voltage detecting circuit  208  controls the switch  206  provided between the internal power source circuit  202  and the charging circuit  201 . When voltage supplied to the internal power source circuit  202  is higher than 13V, that is, when voltage supplied to the internal power source circuit  202  is high enough to charge the battery packs  103   a  and  103   b , the voltage detecting circuit  208  turns on the switch  206  so that the battery packs  103   a  and  103   b  are charged. 
     The power supply system of the extended station  102  will now be explained. 
     The power supply system of the extended station  102  is constructed of a docking detect circuit  211 , a charging circuit  212 , an internal power source circuit  213 , an IC chip  214 , switches  215 ,  216  and  217 , and a reverse-blocking diode D 4 . 
     Referring to FIG. 15, the docking detecting circuit  211  outputs a high or low level signal in accordance with a state of connection between the connector  137  and the connector  147 . When the connector  137  of the notebook PC  101  is connected with the connector  147  of the extended station  102 , voltage Vcc dropped by a resistor R is grounded at the notebook PC  101  through the connector  137  and  147 . Thus, an OFF-state voltage is applied to the switches  215 ,  216  and  217  so as to switch them off. Conversely, when the connector  137  of the notebook PC  101  is not connected with the connector  147  of the extended station  102 , the voltage Vcc dropped by the resistor R is applied as an ON-state voltage to the switches  215 ,  216  and  217  so as to switch them on. 
     The AC adapter  50  is connected to the DC-IN connector  171 . The charging circuit  212  is connected to the DC-IN connector  171  so that the charging circuit  212  generates a charging voltage in accordance with a dc voltage supplied from the AC adapter  50 . 
     The charging voltage generated by the charging circuit  212  is supplied to the charging terminal BATT 2  of the battery pack  103   b  through the switch  215 . Moreover, the charging circuit  212  is connected to the IC chip  214  and is controlled in accordance with charge-on/charge-off signals supplied by the IC chip  214 . The charging circuit  212  outputs the charging voltage when a charging-on signal is supplied to the charging circuit  212  by the IC chip  214  and the charging circuit  212  stops outputting the charging voltage when a charging-off signal is supplied to the charging circuit  212  by the IC chip  214 . 
     Further, the IC chip  214  is connected to the voltage detecting terminal Vsense 2  through the switch  216 . That is, when the switch  216  turns on, the IC chip  214  recognizes a voltage of the voltage detecting terminal Vsense 2  of the battery pack  103   b . Then, the IC chip  214  supplies a charging-off signal to the charging circuit  212  when the voltage of the voltage detecting terminal Vsense 2  of the battery pack  103   b  is higher than a predetermined voltage. On the other hand, the IC chip  214  supplies a charging-on signal to the charging circuit  212  when the voltage of the voltage detecting terminal Vsense 2  of the battery pack  103   b  is lower than the predetermined voltage. 
     The charging-on and the charging-off signals generated by the IC chip  214  are supplied to the internal switch sw 2  of the battery pack  103   b  and a charging indicator LED  218 . When the IC chip  214  outputs the charging-on signal, the charging-on signal is supplied to the charging indicator LED  218  and then the charging indicator LED  218  emits light. Thus, a state of charging is indicated. 
     The switches  215 ,  216  and  217  are off while the extended station  102  is connected with the notebook PC  101 . Accordingly, the IC chip  214  and the charging circuit  212  are not operated. Thus, the battery pack  103   b  is not charged by the extended station  102  itself. On the other hand, the switches  215 ,  126  and  217  are on while the extended station  102  is disconnected from the notebook PC  101 . Accordingly, the IC chip  214  and the charging circuit  212  are operated. Thus, the battery pack  103   b  can be charged by the extended station  102  itself. 
     When the internal power source circuit  213  of the extended station  102  is connected to the DC-IN connector  171  via the reverse-blocking diode D 4 , the internal power source circuit  202  of the notebook PC  101  can be supplied via the connectors  137  and  147 . 
     That is, by dc power from the AC adapter  50  connecting to the DC-IN connector  171  or from the internal power source circuit  202  of the notebook PC  101 , the internal power source circuit  213  can be supplied with enough power to operate the enhanced functions, such as the CD-ROM drive  149 , the floppy disk drive  153  or the like. 
     As mentioned above, in a state in which the notebook PC  101  is attached to the extended station  102 , when the AC adapter  50  is connected to the DC-IN connector  135  or  171 , the battery pack  103   a  mounted in the battery pack slot  141  of the notebook PC  101  and the battery pack  103   b  mounted in the battery pack slot  145  of the extended station  102  can be charged sequentially or simultaneously. On the other hand, in this state, when the AC adapter  50  is not connected to any of the DC-IN connectors  135  and  171 , the notebook PC  101  and the extended station  102  receive power from the batteries  103   a  and  103   b  so that the operating time can be increased. 
     Further, in a state in which the notebook PC  102  is detached from the extended station  102 , when the AC adapter  50  is connected to the DC-IN connector  171  of the extended station  102 , the extended station  102  can charge the battery pack  103   b . The battery packs  103   a  and  103   b  have the same shape that fits into the battery pack slots of the notebook PC  101 , the extended station  102  and the compact bay  104 . Hence, for example, the battery pack  103   b  charged in the extended station  102  can be mounted into the notebook PC  101  or compact bay  104 . Therefore, it is possible to utilize the extended station  102  as a charger. 
     The present invention is not limited to the specifically disclosed embodiments, variations and modifications, and other variations and modifications may be made without departing from the scope of the present invention. 
     The present application is based on Japanese priority application No. 10-260599 filed on Sep. 14, 1998, the entire contents of which are hereby incorporated by reference.