Patent Publication Number: US-2007120525-A1

Title: Electronic device with auxiliary unit that is usable detached from main unit of electronic device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
      This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2005-345910, filed Nov. 30, 2005, the entire contents of which are incorporated herein by reference.  
     BACKGROUND  
      1. Field  
      One embodiment of the invention relates to an electronic device with an auxiliary unit that is usable detached from the main unit of the device.  
      2. Description of the Related Art  
      Various battery-driven portable personal computers, such as notebook personal computers, have been developed. Further, in recent years, so-called detachable personal computers, which incorporate an auxiliary unit detachable (separable) from the main unit and usable in a detached state, have been proposed (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 11-212665). As well as detachable personal computers, other types of electronic devices, which incorporate an auxiliary unit detachable from the main unit and usable in a detached state, have been proposed (see, for example, Jpn. Pat. Appln. KOKAI Publication No. 11-327683).  
      In the conventional electronic devices as described in the above publications, a first rechargeable battery (first secondary battery) is mounted in the main unit. Further, a second rechargeable battery (second secondary battery) different from the first one is mounted in the auxiliary unit usable detached from the main unit. The second battery can be used independently of the first battery. The second battery enables the auxiliary unit to operate even if the unit is detached from the main unit of the electronic device.  
      The above publications do not describe the voltages of the first and second batteries. However, to operate the auxiliary unit regardless of whether the unit is attached to or detached from the main unit, the first and second batteries generally have the same cell structure for generating the same voltage. In this case, the electronic device main unit and auxiliary unit require first and second system power supplies and first and second recharging controllers for controlling the recharging of the first and second batteries, respectively.  
      When the auxiliary unit is used attached to the electronic device main unit, if a high-voltage power supply, such as an AC adaptor, is usable, the first and second system power supplies and the first and second recharging controllers are powered by a relatively high DC voltage generated by the high-voltage power supply. Accordingly, the first and second system power supplies must employ power supply ICs that can operate even if a high voltage is applied. Similarly, decoupling capacitors that can operate even if a high voltage is applied must be employed as the decoupling capacitors necessary for the first and second recharging controllers.  
      In the above electronic devices, it is difficult to reduce the size and width not only of the power supply circuit for the electronic device main unit, but also of the power supply circuit for the auxiliary unit that can be used detached from the main unit. Further, in the above electronic devices, the first and second batteries simultaneously discharge. Accordingly, when the auxiliary unit is used detached from the electronic device main unit, it is difficult to sufficiently use the capacity of the second battery mounted in the auxiliary unit. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
      A general architecture that implements the various features of the invention will now be described with reference to the drawings. The drawings and the associated descriptions are provided to illustrate an embodiment of the invention and not to limit the scope of the invention.  
       FIG. 1  is a perspective view illustrating an exemplary detachable notebook personal computer  10  according to an embodiment of the invention;  
       FIG. 2  is a block diagram illustrating an exemplary system configuration of the main unit of the computer appearing in  FIG. 1 ;  
       FIG. 3  is a block diagram illustrating an exemplary system configuration of the display unit appearing in  FIG. 1 ; and  
       FIG. 4  is a block diagram mainly illustrating an exemplary configurations of the power supply circuits of the computer main unit and display unit. 
    
    
     DETAILED DESCRIPTION  
      An embodiment according to the invention will be described hereinafter with reference to the accompanying drawings. In general, according to the embodiment, there is provided an electronic device. The electronic device comprises an electronic device main unit including a first system load, and an auxiliary unit permitted to be used attached to the electronic device main unit, and also permitted to be used detached from the electronic device main unit. The auxiliary unit includes a second system load. The electronic device main unit includes a first battery charged with a first voltage, and a first power supply circuit. The first power supply circuit includes a first recharging controller and first system power supply. The first recharging controller is configured to perform control for recharging the first battery to set the first battery at the first voltage. The first recharging controller is powered by a second voltage applied thereto by an AC adaptor. The second voltage is higher than the first voltage. The first system power supply is configured to apply a third voltage to the first system load. The third voltage is lower than the first voltage. The first system power supply is powered by the AC adaptor when the AC adaptor is used, and powered by the first battery when the AC adaptor is not used. The auxiliary unit includes a second battery set, by recharging, at a fourth voltage lower than the third voltage, and a second power supply circuit. The second power supply circuit includes a second recharging controller and second system power supply. The second recharging controller is configured to perform control for recharging the second battery to set the second battery at the fourth voltage. The second recharging controller is powered by the third voltage applied thereto by the first system power supply, when the auxiliary unit is attached to the electronic device main unit. The second system power supply is configured to apply a fifth voltage to the second system power supply. The second system power supply is powered by the first system power supply when the first system power supply is used, and powered by the second battery when the first system power supply is not used.  
      Referring first to FIGS.  1  to  4 , the configuration of an electronic device according to the embodiment will be described. This electronic device is realized as a detachable notebook personal computer  10  powered by a battery.  
       FIG. 1  is a perspective view illustrating the state in which the display unit of the detachable personal computer  10  is open. The computer (electronic device)  10  comprises a computer main unit (electronic device main unit)  11  and display unit  12 . The display unit  12  is an auxiliary unit as part of the computer  10 , and can be operated independently of the computer main unit  11 , detached therefrom.  
      The display unit  12  incorporates a display device formed of a liquid crystal display (LCD)  17 . The display screen of the LCD  17  is located at substantially the center of the display unit  12 . A touch panel  32  (see  FIG. 3 ) is provided on, for example, the front surface of the LCD  17 .  
      The display unit  12  is attached to the computer main unit  11  by hinges  18 A and  18 B so that it can pivot between an open position and closed position. Like an input board incorporated in the thin computer disclosed in the previously described publication, i.e., Jpn. Pat. Appln. KOKAI Publication No. 11-212665, the display unit  12  is detachable from the computer main unit  11 .  
      The computer main unit  11  has a case in a thin box shape, and incorporates, on its upper surface, a keyboard  13 , power button switch  14 , input operation panel  15  and touch pad  16 . The power button switch  14  is used to power on and power off the computer  10 . The input operation panel  15  includes a plurality of button switches for activating a plurality of functions, and serves as an input unit for inputting events corresponding to the button switches when they are pressed.  
       FIG. 2  is a block diagram illustrating the system configuration of the computer main unit  11 . As shown, the computer main unit  11  comprises a CPU  111 , north bridge  112 , main memory  113 , graphics controller  114  and south bridge  115 . The computer main unit  11  further comprises a BIOS-ROM  120 , hard disk drive (HDD)  130 , optical disk drive (ODD)  140 , LAN controller  151 , wireless LAN controller (W-LAN controller)  152 , card controller  153 , embedded-controller/keyboard-controller IC (EC/KBC)  160  and power supply circuit  170 .  
      The CPU  111  is a processor for controlling the entire operation of the computer  10 . The CPU  111  executes an operating system (OS) loaded from the HDD  130  as a boot device to the main memory  113 . The CPU  11  also executes various application programs. The CPU  11  further executes a basic input output system (BIOS) stored in the BIOS-ROM  120 . The BIOS is a program for controlling the hardware.  
      The north bridge  112  is a bridge device connecting the local bus of the CPU  111  to the south bridge  115 . The north bridge  112  contains a memory controller for controlling access to the main memory  113 . Further, the north bridge  112  has a function for executing communication with the graphics controller  114  via an accelerated graphics port (AGP) bus.  
      The graphics controller  114  is a display controller for controlling the LCD  17  that is used as the display monitor of the computer  10 . The graphics controller  114  is operable when the display unit  12  is used attached to the computer main unit  11 . The graphics controller  114  includes a video memory (VRAM)  114   a.  Based on display data written to the VRAM  114   a,  the graphics controller  114  generates a video signal for forming a display image to be displayed on the LCD  17 .  
      The south bridge  115  controls access to the BIOS-ROM  120 . The BIOS-ROM  120  is a rewritable nonvolatile memory, such as a flash ROM. As described above, the BIOS-ROM  120  stores the BIOS. The south bridge  115  controls disk drives (I/O devices), such as the HDD  130  and ODD  140 . The south bridge  115  is connected to a peripheral component interconnect (PCI) bus  2  and low pin count (LPC) bus  3 , and controls the devices on the PCI bus  2  and LPC bus  3 . The PCI bus  2  serves as a system bus.  
      The HDD  130  is a storage device for storing various types of software and data. The HDD  130  reads/writes data from/to a magnetic recording medium (magnetic disk), using a head (magnetic head). The HDD  130  prestores the OS. The OS is loaded to the main memory  113  in accordance with the BIOS stored in the BIOS-ROM  120 , and is executed by the CPU  111 .  
      The ODD  140  is a drive unit for driving (rotating) an optical record medium (optical disk), such as a compact disk (CD) or digital versatile disk (DVD), using a motor. The ODD  140  reads/writes data from/to an optical disk, using a head (optical head).  
      The PCI bus  2  is connected to the LAN controller  151 , W-LAN controller  152  and card controller  153 . The LAN controller  151  is a network controller for connecting the computer main unit  11  to a LAN (wired LAN). The W-LAN controller  152  is a network controller for connecting the computer main unit  11  to a wireless LAN. The card controller  153  controls a card device, such as a PC card or secure digital (SD) card, inserted in a card slot connected to the card controller  153 .  
      The EC/KBC  160  is a microcomputer formed of a single chip that comprises an embedded controller for power supply management, and a keyboard controller for controlling the keyboard (KB)  13  and touch pad  16 . The EC/KBC  160  cooperates with the power supply circuit  170  to realize a power supply control function for powering on and off the computer  10  in response to the operation of the power button switch  14  by a user. The power supply circuit  170  generates a system power supply voltage to be applied to each element of the computer main unit  11 . For generating the system power supply voltage, the power supply circuit  170  uses a DC power supply voltage supplied from a rechargeable battery (first battery)  171  or an AC adaptor  172  serving as a high-voltage power supply. The AC adaptor  172  converts an AC power supply voltage into the DC power supply voltage.  
       FIG. 3  is a block diagram illustrating the system configuration of the display unit  12 . As shown, the display unit  12  comprises, as well as the LCD  17  shown in  FIG. 1 , an LCD controller  31 , touch panel  32 , touch panel controller  33 , main controller  34 , flash ROM (FROM)  35 , synchronous DRAM (SDRAM)  36 , W-LAN controller  37 , power supply circuit  38  and battery  39 .  
      The LCD controller  31  is a display controller for controlling the LCD  17 . The LCD controller  31  is operable when the display unit  12  is used detached from the computer main unit  11 . The LCD controller  31  includes a video memory (VRAM)  310 . Based on display data written to the VRAM  310 , the LCD controller  31  generates a video signal for forming a display image to be displayed on the LCD  17 .  
      The touch panel  32  is an input surface for enabling a user to designate a position thereon when they touch it by their finger. The touch panel  32  is transparent and is located at, for example, the front surface of the LCD  17 . The touch panel controller  33  detects the position on the touch panel  32  touched by the finger. As a result, the user can directly designate, by their finger, various menus, for example, displayed on the LCD  17  by the LCD controller  31 . Instead of the touch panel  32  and touch panel controller  33 , a tablet (digitizer) capable of designating a position using, for example, a pen, and a tablet controller (digitizer controller) may be employed.  
      The main controller  34  controls the entire operation of the display unit  12 . The main controller  34  comprises, for example, a CPU and I/O controller, which are not shown. The CPU executes various programs stored in the FROM  35 . The I/O controller controls data input/output between the LCD controller  31 , touch panel controller  33  and W-LAN controller  37 . Part of the SDRAM  36  is used as a work area for the CPU of the main controller  34 . In the embodiment, the programs stored in the FROM  35  include a program for an Internet viewer, i.e., a so-called browser.  
      The W-LAN controller  37  is a network controller for connecting the display unit  12  to a wireless LAN. By virtue of the W-LAN controller  37 , the main controller  34  enables the display unit  12  to function as an independent Internet viewer, in accordance with the program for the Internet viewer. Further, the main controller  34  enables the display unit  12  to function as part of the computer  10 , by causing the W-LAN controller  37  to perform wireless communication with the W-LAN controller  152  of the computer main unit  11 .  
      Instead of wireless communication by the W-LAN controllers  37  and  152 , other wireless communication devices, such as super-wideband wireless controllers, can be used. Further, if the computer main unit  11  is electrically connected to the display unit  12  by a connector, communication can be performed between the computer main unit  11  and display unit  12  via, for example, the PCI bus  2  or LAN line.  
      The power supply circuit  38  generates a power supply voltage (system power supply voltage) for powering the elements in the display unit  12 . When the display unit  12  is attached to the computer main unit  11 , the power supply circuit  38  is powered by the system power supply voltage generated by the power supply circuit  170  of the computer main unit  11 . In contrast, when the display unit  12  is detached from the computer main unit  11 , the power supply circuit  38  is powered by the voltage generated by the battery  39 . The battery  39  is a rechargeable one, and generates a lower voltage than the battery  171  of the computer main unit  11 . In the embodiment, the battery  39  generates a voltage of +4V, and the battery  171  generates a voltage of +12V.  
       FIG. 4  is a block diagram mainly illustrating the power supply circuits  170  and  38  incorporated in the computer main unit  11  and display unit  12 , respectively. The power supply circuit (first power supply circuit)  170  of the computer main unit  11  comprises a recharging controller (first recharging controller)  41 , system power supply (first system power supply)  42  and diodes  43 ,  44  and  45 . The output (the output-side positive terminal) of the AC adaptor  172  is connected to the anode of the diode (first diode)  43 , and the cathode of the diode  43  is connected to the input of the recharging controller  41 . The AC adaptor  172  is formed of, for example, an AC-to-DC converter for converting the commercial AC voltage into a DC voltage of +15V.  
      Accordingly, when the AC power supply is connected to the computer main unit  11  via the AC adaptor  172 , the DC voltage of +15V output from the AC adaptor  172  is applied to the input of the recharging controller  41  via the diode  43 . When the DC voltage (second voltage) is applied to the recharging controller  41 , the recharging controller  41  performs control for recharging the battery  171  with, for example, +12V (first voltage).  
      The cathode of the diode  43  is connected to the anode of the diode  44  (second diode), as well as to the input of the recharging controller  41 . The positive terminal of the battery  171  is connected to the anode of the diode  45  (third diode), and the cathode of the diode  45  is connected to the cathode of the diode  44  and the input of the system power supply  42 .  
      This enables both the AC adaptor  172  and battery  171  to apply their DC voltages to the input of the system power supply  42 . Since the voltage (+15V) applied by the AC adaptor  172  is higher than the voltage (+12V) applied by the battery  171 , the system power supply  42  is powered by the voltage (+15V) applied by the AC adaptor  172 . At this time, the discharge of the battery  171  is suppressed.  
      In contrast, when the computer main unit  11  is not connected to the AC power supply, for instance, when the user carries the computer  10 , the system power supply  42  is powered by the battery  171 . The system power supply  42  is formed of a DC-to-DC converter. The system power supply  42  converts the applied voltage +12V into, for example, +5V. The voltage of +5V is used as a power supply voltage for a load (system load)  61  that includes the elements of the computer main unit  11 .  
      The diode  43  is a backflow preventing device, and prevents backflow of the current acquired when the DC voltage is applied by the AC adaptor  172 , with the polarity (+) or (−) of the voltage reversed. The diode  44  prevents backflow of a current to the recharging controller  41 . The diode  45  prevents the DC voltage from being directly applied to the battery  171  by the AD adaptor  172 .  
      On the other hand, the power supply circuit (second power supply circuit)  38  of the display unit  12  comprises a recharging controller (second recharging controller)  51 , system power supply (second system power supply)  52 , diodes  53 ,  54  and  55 , and switch  56 . When the display unit  12  is attached to the computer main unit  11 , the output (output-side positive terminal) of the system power supply  42  of the computer main unit  11  is connected to the anode of the diode  53  (fourth diode) via, for example, a power supply connector (not shown). The cathode of the diode  53  is connected to the input of the recharging controller  51 . In this structure, the system power supply  42  of the computer main unit  11  applies the DC voltage of +5V to the recharging controller  51  via the diode  53 . The recharging controller  51 , in turn, performs control for recharging the battery  39  with, for example, +4V.  
      Since the voltage (+5V) applied to the recharging controller  51  is lower than the voltage (+12V) applied to the recharging controller  41  of the computer main unit  11 , the decoupling capacitor necessary for the recharging controller  51  can be set to a lower withstand voltage than that necessary for the recharging controller  41 . Similarly, the power supply IC necessary for the system power supply  52  can be set to a lower withstand voltage than that necessary for the system power supply  42  of the computer main unit  11 . As a result, the power supply circuit  38  including the recharging controller  51  and system power supply  52  can be made compact and thin, and accordingly, the display unit  12  can be made more compact and thinner and hence be carried more easily.  
      The positive terminal of the battery  39  is connected to the anode of the diode  55  (fifth diode), and the cathode of the diode  55  is connected to the cathode of the diode  54  (fifth diode) and the input of the system power supply  54 . The anode of the diode  53  is connected to the anode of the diode  54  via the switch  56 .  
      By virtue of this structure, when the display unit  12  is attached to the computer main unit  11  and the switch  56  is closed, both the system power supply  42  of the computer main unit  11  and the battery  39  can apply their DC voltages to the input of the system power supply  52 . Since the voltage (+5V) applied by the system power supply  42  is higher than the voltage (+4V) applied by the battery  39 , the system power supply  52  is powered by the system power supply  42 . Namely, the switch  56  in the closed state is used as a selection switch that enables the system power supply  52  to be powered by the system power supply  42 .  
      When the system power supply  52  is powered by the system power supply  42 , the discharge of the battery  39  is suppressed. However, at this time, the voltage applied to the system power supply  52  is regulated to the lower one of the voltages applied by the system power supply  42  and battery  39 , i.e., the voltage (+4V) of the battery  39 . Namely, the system power supply  52  is powered by the voltage of +4V.  
      In contrast, when the display unit  12  is used singly, detached from the computer main unit  11 , the system power supply  52  is powered by the battery  39 . As described above, when the display unit  12  is attached to the computer main unit  11 , the system power supply  52  is powered by the system power supply  42  of the computer main unit  11 . In this state, the battery  39  of the display unit  12  does not discharge, i.e., the charge accumulated therein is not consumed. Therefore, when the display unit  12  is singly used detached from the computer main unit  11 , the capacity of the battery  39  can be sufficiently utilized, thereby enabling the display unit to be powered for a long time by the battery  39 .  
      The system power supply  52  is formed of a DC-to-DC converter. The system power supply  52  converts the applied voltage +4V into, for example, +3.3V. The voltage of +3.3V is used as a power supply voltage for a load (system load)  62  that includes the elements of the display unit  12 . It is a matter of course that if a power supply voltage for each element in the display unit  12  exceeds +4V, e.g., if it is +5V that is equal to the power supply voltage for each element in the computer main unit  11 , the applied voltage of +4V is boosted to +5V.  
      The diode  53  is a backflow preventing device, and prevents backflow of the current acquired when the DC voltage applied by the system power supply  42  has the reverse polarity. Further, the diode  54  prevents the voltage from being applied by the battery  39  to the system power supply  42 . The diode  55  prevents the DC voltage from being directly applied to the battery  39  by the system power supply  42 .  
      The anodes of the diodes  53  and  54  are connected to each other via the switch  56 . When the switch  56  is closed and the display unit  12  is attached to the computer main unit  11 , the system power supply  52  of the display unit  12  is powered by the system power supply  42  of the computer main unit  11 , as described above. Assume here that since, for example, the user carries the computer  10 , the computer main unit  11  is not connected to the AC power supply. In this case, the system power supply  42  of the computer main unit  11  is powered by the battery  171 . This means that the system power supply  52  of the display unit  12  is powered by the battery  171 . Namely, when the switch  56  is closed in a particular state in which the display unit  12  is attached to the computer main unit  11 , and the computer main unit  11  is disconnected from the AC power supply, the display unit  12  is powered by the battery  171  of the computer main unit  11 .  
      Assume here that the switch  56  is opened in the particular state. At this time, the battery  39  of the display unit  12  starts to discharge to power the system power supply  52  of the display unit  12 . Namely, the switch  56  in the open state is used as a selection switch that prevents the system power supply  52  from being powered by the system power supply  42 .  
      As described above, in the embodiment, when the switch  56  is closed in the above-described particular state, the display unit  12  can be powered by the battery  171  of the computer main unit  11 . Further, when the switch  56  is open in the above-described particular state, the display unit  12  can be powered by the battery  39  thereof. This being so, the display unit  12  can be operated for a longer time in the particular state.  
      While a certain embodiment of the invention has been described, it has been presented by way of example only, and is not intended to limit the scope of the invention. Indeed, the novel apparatus and method described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the apparatus and method described herein may be made without departing from the spirit of the invention. The accompanying claims and their equivalents are intended to cover such forms or modification as would fall within the scope and spirit of the invention.