Abstract:
A connection apparatus to which an electronic device having a rechargeable power unit and capable of charging the rechargeable power unit in plural charge modes, can be connected, the connection apparatus including; a connector to which the electronic device can be connected and to which are connected an electric signal line used for exchanging electric signals with the electronic device and a power supply line used for charging the rechargeable power unit in the plural charge modes; and a signal output module for delivering to the connector a simulated reconnection signal for causing the electronic device to detect a temporary interruption of an electrical connection between the electronic device and the connector and a subsequent restoration of the temporarily interrupted electrical connection after a prescribed time interval, and a charge mode selection signal which the electronic device refers to, after having received the simulated reconnection signal, in selecting one of the charge modes.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present application claims priority to Japanese Patent Application No. 2009-186299 filed on Aug. 11, 2009, the disclosure of which is hereby incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to a connection apparatus to which is connected an electronic device that has a rechargeable power unit and is capable of charging the rechargeable power unit in plural charge modes. 
         [0004]    2. Description of the Related Art 
         [0005]    Portable electronic devices like PDAs and mobile phones, which each incorporate therein a rechargeable power unit such as a battery, have recently become more popular. Of such portable electronic devices are known those devices which can charge the batteries by selecting one of plural charge modes. When a portable electronic device of this kind is connected to a peripheral device for power supply, the device selects its own charge mode according to the type of the peripheral device, and initiates charging. 
         [0006]    Known techniques for charging the batteries of portable electronic devices are disclosed in JP2000-354218A and JP2008-193783A, for example. JP2000-354218A discloses a charging device that varies the charging voltage depending on the type of digital camera. JP2008-193783A discloses a method for switching the current values of the charging current according to the status of the battery of a mobile phone. 
         [0007]    These techniques, however, have shown little ingenuity in the way of switching the charge modes of a portable electronic device having plural charge modes. This issue is not limited only to portable electronic devices, but in general common to electronic devices with rechargeable power units. 
       SUMMARY 
       [0008]    An object of the present invention, which has been made to solve the problem described above, is to provide a technique capable of switching the charge modes of an electronic device automatically. 
         [0009]    In order to solve the above mentioned problem, this invention can be embodied in the following modes of practice or examples of application. 
       First  Example  Of Application  
       [0010]    According to a first example of application, there is provided A connection apparatus to which an electronic device having a rechargeable power unit and capable of charging the rechargeable power unit in plural charge modes, can be connected, the connection apparatus including; a connector to which the electronic device can be connected and to which are connected an electric signal line used for exchanging electric signals with the electronic device and a power supply line used for charging the rechargeable power unit in the plural charge modes; and a signal output module for delivering to the connector a simulated reconnection signal for causing the electronic device to detect a temporary interruption of an electrical connection between the electronic device and the connector and a subsequent restoration of the temporarily interrupted electrical connection after a prescribed time interval, and a charge mode selection signal which the electronic device refers to, after having received the simulated reconnection signal, in selecting one of the charge modes. 
         [0011]    When the electronic device is connected to the connector of the connection apparatus, the electronic device selects its own charge mode according to the status of the connection apparatus. Once the electronic device selects a charge mode, the selected charge mode is maintained until the electronic device is disconnected from the connector. Therefore, according to the first example of application of the invention, the electronic device can detect the temporary interruption of the electrical connection between the electronic device and the connector and the subsequent restoration of the temporarily interrupted electrical connection after the prescribed time interval. Thus, in the event of a change of the status of the connection apparatus, the charge mode of the electronic device may be switched automatically. Throughout this specification, the term “power unit” is meant to refers to batteries, secondary cells, capacitors, and similar rechargeable devices capable of repeated cycles of charge and discharge of electrical energy. 
       Second  Example  Of Application   
       [0012]    According to a second example of application of the present invention, there is provided the connection apparatus as described in the first example of application, wherein the connector has a terminal receiving the simulated reconnection signal from the signal output module, and the simulated reconnection signal is equivalent to the state where, for the prescribed time interval, a floating potential is developed at the terminal. 
         [0013]    According to the second example of application of the present invention, the simulated reconnection signal may correspond to a high impedance developed between the terminal and a ground line, for the prescribed time interval. 
         [0014]    The electronic device detects its connection with the connector on the basis of the state of the terminal of the connector of the connection apparatus. Therefore, according to the second example of application, the electronic device can detect the temporary interruption of the electrical connection between the electronic device and the connector and the subsequent restoration of the temporarily interrupted electrical connection after the prescribed time interval. As a result, the charge mode of the electronic device can be changed automatically. 
       Third  Example  Of Application   
       [0015]    According to a third example of application of the invention, there is provided the connection apparatus as described in the first or second example of application, wherein the connection apparatus can be connected to a computer, and the signal output module changes a level of the charge mode selection signal when power supply voltage supplied to the connection apparatus from the computer changes. 
         [0016]    According to the third example of application, the charge mode of the electronic device can be changed in accordance with the level change in the power supply voltage supplied from the computer. 
       Fourth  Example  Of Application   
       [0017]    According to a fourth example of application of the present invention, there is provided the connection apparatus as described in the third example of application, wherein the signal output module outputs the simulated reconnection signal when power supply voltage supplied to the connection apparatus from the computer changes. 
         [0018]    According to the fourth example of application, if the level of the power supply voltage supplied from the computer changes, the electronic device can detect the temporary interruption of the electrical connection between the electronic device and the connector and the subsequent restoration of the temporarily interrupted electrical connection after the prescribed time interval. As a result, the charge mode of the electronic device can be changed automatically. 
       Fifth  Example  Of Application   
       [0019]    According to a fifth example of application of the present invention, there is provided the connection apparatus as described in the first through fourth example of application, further comprising a charge mode indicating module for notifying a user of a type of the charge mode of the electronic device. 
         [0020]    According to the fifth example of application, the user can detect the type of the charge mode of the electronic device. 
         [0021]    The present invention can be realized in various modes of practice. Examples of such modes include a method and a device for connecting an electronic device and a computer; a connection system; an integrated circuit for accomplishing the function of such a method or device; a computer program; or a storage medium having the computer program recorded therein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0022]      FIG. 1  illustrates the configuration of a cradle with USB hub function and peripheral devices according to an embodiment of the present invention; 
           [0023]      FIG. 2  schematically shows the circuit configuration of the cradle; 
           [0024]      FIG. 3  is a timing chart showing the waveforms of the signals appearing at several points within the cradle; 
           [0025]      FIG. 4  is an illustration for explaining the state transitions of the cradle; 
           [0026]      FIG. 5  illustrates the configuration of a cradle according to a second embodiment; and 
           [0027]      FIG. 6  is a flowchart for explaining the operation of the cradle according to the second embodiment. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Modes of Practice of the Invention 
     A. First Embodiment 
       [0028]      FIG. 1  illustrates the configuration of a cradle  100  with USB hub function and its peripheral devices according to an embodiment of the present invention. The cradle  100  is so designed that a personal digital assistant (PDA)  150  can be attached to it, and is connected to a computer  200  via a USB port  12  to which a USB cable  10  is connected. The cradle  100  has a connector  18  to be connected with the PDA  150 , and USB ports  13 ,  14 ,  15  to be connected with USB peripheral devices. That is, the cradle  100  also functions as a USB hub. The cradle  100  is connected via a power terminal  16  to an AC/DC adapter  17  which supplies the cradle  100  with a DC power supply voltage Vc of 5V. 
         [0029]    The PDA  150  has a display  154  and control buttons  156  on the front side thereof, and a battery  158  as the power unit inside it. The display  154  can display information that is stored in a storage medium (not shown) incorporated in the PDA  150 . The user can operate the PDA  150  with the control buttons  156  while viewing information displayed on the display  154 . 
         [0030]    The PDA  150  is provided with a dedicated connector  152  on the lower periphery thereof, and when the PDA  150  is attached to the cradle  100 , the connector  152  connects to the connector  18  of the cradle  100 . Via the connector, the PDA  150  can exchange data with the computer  200  and also charge the battery  158  provided therein. 
         [0031]    The PDA  150  can charge the battery  158  in plural charge modes. In the present embodiment, the PDA  150  has two charge modes, i.e. “Charge Mode A” and “Charge Mode B”. The “Charge Mode A” is a mode in which data communication with the computer  200  is enabled while the battery  158  is being charged. The “Charge Mode B”, on the other hand, is a mode in which data communication with the computer  200  is disabled although the battery  158  can be charged faster with current density greater than that in the “Charge Mode A”. 
         [0032]    The cradle  100  has two power supply modes (“Power Supply Mode A” and “Power Supply Mode B”) which correspond to the two charge modes of the PDA  150 , and can switch from one power supply mode to the other to charge the battery  158  of the PDA  150 . 
         [0033]    As will be discussed later, when the computer  200  is powered on and the cradle  100  is connected to the computer  200  via the USB cable  10 , the cradle  100  enters the “Charge Mode A”. On the other hand, when the computer  200  is turned off or when the cradle  100  is not connected with the computer  200 , e.g. when the USB cable  10  is unplugged from the USB port  12 , the cradle  100  enters the “Charge Mode B”. 
         [0034]    The cradle  100  is also furnished with an LED indicator  20  for indicating which power supply mode it is in. The LED indicator  20  may emit lights of different colors corresponding to the different power supply modes. This enables the user of the cradle  100  to ascertain the power supply mode of the cradle  100  from the color of the LED indicator  20 . The LED indicator  20  may be omitted however. 
         [0035]    When a peripheral device is connected to the connector  152 , the PDA  150  determines whether the peripheral device is capable of data communications during charging, or capable of charging alone. In the present embodiment, when the PDA  150  is attached to the cradle  100 , the PDA  150  determines the power supply mode of the cradle  100 . The PDA  150  then sets its own charge mode according to the power supply mode of the cradle  100 . In other words, if the PDA  150  is attached to the cradle  100  when the cradle  100  is in the “Power Supply Mode A”, the PDA  150  enters the “Charge Mode A”. On the other hand, if the PDA  150  is attached to the cradle  100  when the cradle  100  is in the “Power Supply Mode B”, the PDA  150  enters the “Charge Mode B”. 
         [0036]    Once the PDA  150  establishes its own charge mode, the established charge mode is maintained until the connector  152  of the PDA  150  is disconnected from the power supply device even if the power supply mode of the power supply device subsequently changes. In other words, if the power supply device is in the “Power Supply Mode A” when the PDA  150  is connected to the power supply device, the PDA  150  enters the “Charge Mode A”. If the power supply mode of the power supply device subsequently switches from “Power Supply Mode A” to “Power Supply Mode B”, the PDA  150  maintains its own charge mode, i.e. “Charge Mode A”. Thus, in order to switch the charge mode of the PDA  150  from “Charge Mode A” to “Charge Mode B”, it is necessary for the user to disconnect the connector  152  of the PDA  150  from the connector of the power supply device, and then to reconnect the connector  152  of the PDA  150  with the connector of the power supply device. A similar procedure must be followed to switch the power supply device from “Power Supply Mode B” to “Power Supply Mode A”. Therefore, the cradle  100  according to the present embodiment is so designed as described below that when the power supply mode of the cradle  100  changes, the charge mode of the PDA  150  changes automatically without the user having to attach the PDA  150  to or detach it from the cradle  100 . 
         [0037]      FIG. 2  schematically shows the circuit configuration of the cradle  100 . The cradle  100  includes the USB ports  12 ,  13 ,  14 ,  15 , the power supply terminal  16 , the connector  18 , the LED indicator  20 , a USB hub controller  22  and a simulated reconnection circuit  30 . 
         [0038]    The cradle  100  is supplied with a power supply voltage Vc from the AC/DC adapter  17  through the power supply terminal  16 , and the constituents of the cradle  100  are in turn supplied with the power supply voltage Vc as operating power through a power supply line VL 1 . 
         [0039]    The USB hub controller  22  is connected to the USB port  12  via a USB power supply line VL 2  and a USB data line DL 1 . The USB hub controller  22  sends the data received from the USB data line DL 1 , to the connector  18  and to the USB ports  13 ,  14 ,  15 , through UBS data lines DL 2  to LD 5 . Actually, a data line according to the USB standard is composed of a pair of signal lines, but for convenience the pair of signal lines is described as a single signal line. This convention applies also to the terminals connected to the ends of the data lines. 
         [0040]    Two voltage-dividing resistors R 1 , R 2  are connected in series between the power supply line VL 1  and the ground GND. A branch line BL extends from the intermediate point between the voltage-dividing resistor R 1  and the voltage-dividing resistor R 2 . Accordingly, the voltage Vx applied to the branch line BL is equivalent to the voltage obtained by stepping down the power supply voltage Vc in accordance with the ratio of the resistance values of the voltage-dividing resistors R 1 , R 2 . The branch line BL connects to a switch SW 2  in the simulated reconnection circuit  30 . 
         [0041]    The description now turns to the connector  18  of the cradle  100 . The connector  18  is provided with many terminals; of these, a power supply terminal a 1 , a peripheral device type identification terminal a 2 , and a data terminal a 3  are discussed here. 
         [0042]    The power supply terminal a 1  is a terminal for supplying power to the PDA  150  (and the battery  158 ). As will be discussed later, the PDA  150  can determine whether a peripheral device is connected to the connector  152  by detecting whether the power source voltage is being applied to the power supply terminal a 1  or whether the terminal a 1  is at floating potential. 
         [0043]    The peripheral device type identification terminal a 2  is a terminal that allows the PDA  150  to identify the type of a peripheral device connected to the connector  152 . To be concrete, when that terminal on the side of the connector  152  which corresponds to the peripheral device type identification terminal a 2  is connected to the peripheral device type identification terminal a 2  and when the peripheral device type identification terminal a 2  is at the ground potential GND, the PDA  150  senses that a device capable of data communications in addition to charging (i.e. the cradle  100  in the “Power Supply Mode A”) is connected to the connector  152 . 
         [0044]    On the other hand, when the corresponding terminal of the connector  152  is connected to the peripheral device type identification terminal a 2  and when the peripheral device type identification terminal a 2  is at a prescribed voltage (in the present embodiment, voltage Vx), the PDA  150  senses that a device only capable of charging (i.e. the cradle  100  in the “Power Supply Mode B”) is connected to the connector  152 . 
         [0045]    If the cradle  100  is in the “Power Supply Mode A”, the data terminal a 3  is used to transfer data between the computer  200  and the PDA  150 . 
         [0046]    A switch SW 1  is provided between the power supply terminal a 1  and the power supply line VL 1 . The switch SW 2  is located between the peripheral device type identification terminal a 2  and the branch line BL. Another switch SW 3  is provided between the peripheral device type identification terminal a 2  and the ground GND. That is, the switch SW 2  and the switch SW 3  are arranged in parallel with each other. Through the operation of the switches SW 2  and SW 3 , the peripheral device type identification terminal a 2  can be connected to either the branch line BL or the ground GND. 
         [0047]    The simulated reconnection circuit  30  has a control circuit  31  therein, and the USB power supply line VL 2  is connected to the control circuit  31 . The control circuit  31  opens and closes the switches SW 1  to SW 3  according to the USB power supply voltage Vbus. The operations of the switches SW 2 , SW 3  are discussed below while the operation of the switch SW 1  is discussed later. 
         [0048]    The control circuit  31  switches the connection of the peripheral device type identification terminal a 2  according to the voltage level of the USB power supply voltage Vbus of the USB power supply line VL 2 . In other word, if the USB power supply voltage Vbus is being supplied, the control circuit  31  opens the switch SW 2  and closes the switch SW 3 , thereby connecting the peripheral device type identification terminal a 2  to the ground potential GND. The cradle  100  thus enters the “Power Supply Mode A” where the cradle  100  can send and receive data to and from the PDA  150  and power supply is also available. 
         [0049]    On the other hand if the USB power supply voltage Vbus is not being supplied, the control circuit  31  closes the switch SW 2  and opens the switch SW 3 , thereby connecting the peripheral device type identification terminal a 2  to the branch line BL. The cradle  100  thus enters the “Power Supply Mode B” in which the cradle  100  cannot send and receive data to and from the PDA  150 , but can enable fast charging. 
         [0050]    While the difference between “Power Supply Mode A” and “Power Supply Mode B”, of the cradle  100  is simply that the peripheral device type identification terminal a 2  is connected differently through switching. In this case, however, since the PDA  150  detects these two states as the connections to different types of power supply devices, these states are termed “Power Supply Mode A” and “Power Supply Mode B” for convenience. 
         [0051]    The LED assembly  20  is composed of a red-light emitting element  20 R that emits red light and a green-light emitting element  20 G that emits green light. The red-light emitting element  20 R is connected to the power supply line VL 1 , and the green-light emitting element  20 G is connected to the USB power supply line VL 2 . Accordingly, when the cradle  100  is in the “Power Supply Mode B”, only the red-light emitting element  20 R is lit, and the LED indicator  20  emits red light. On the other hand, when the cradle  100  is in the “Power Supply Mode A”, the green-light emitting element  20 G is lit in addition to the red-light emitting element  20 R, and the red and green colors mix so that the LED indicator  20  emits yellow light. Thus the user can distinguish between the power supply modes of the cradle  100  by the color emitted by the LED indicator  20 . As will be discussed later, in the present embodiment, when the power supply mode of the cradle  100  changes, the charge mode of the PDA  150  also changes automatically. Thus, the user can distinguish between the charge modes of the PDA  150  by the color emitted by the LED indicator  20 . 
         [0052]      FIG. 3  shows various time-varying signal waveforms appearing in the circuit of the cradle  100 . In  FIG. 3  are shown the USB power supply voltage Vbus on the USB power supply line VL 2 , the signal that appears on the power supply terminal a 1 , the signal that appears on the peripheral device type identification terminal a 2 , and the signal that appears on the data terminal a 3  at the end of the data line DL 2 . 
         [0053]    During the time interval α for which the USB power supply voltage Vbus is at its H level, the computer  200  is powered on and the USB power supply voltage Vbus is applied to the cradle  100  via the USB cable  10 . During this interval □, since the switch SW 2  is open and the switch SW 3  is closed, the ground potential GND appears on the peripheral device type identification terminal a 2 . That is, the cradle  100  is in the “Power Supply Mode A”. Also, during the interval □, data transfer takes place via the data terminal a 3 . 
         [0054]    On the other hand, during the interval β, since the computer  200  is not powered on, or the USB cable  10  is not connected with the cradle  100 , then the USB power supply voltage Vbus is not applied to the cradle  100 . During this interval β, the switch SW 2  is closed and the switch SW 3  is open, so that the voltage Vx appears on the peripheral device type identification terminal a 2 . That is, the cradle  100  is in the “Power Supply Mode B”. During the interval β, data transfer does not take place at the data terminal a 3 . 
         [0055]    When the connector  152  is connected to the connector  18  of the cradle  100  and when the PDA  150  receives the supply of power from the power supply terminal al (i.e. when the rising edge of the voltage at the power supply terminal a 1  is detected), the PDA  150  detects the voltage level at the peripheral device type identification terminal a 2 , and decides whether the computer  200 , which requests data communications, is connected to the data terminal  3   a  according to the voltage level at the peripheral device type identification terminal a 2 . As mentioned above, if the peripheral device type identification terminal a 2  is at the ground potential GND, the PDA  150  decides that the cradle  100  is in the “Power Supply Mode A” and sets itself to the “Charge Mode A”. On the other hand, if the peripheral device type identification terminal a 2  is at the voltage Vx, the PDA  150  decides that the cradle  100  is in the “Power Supply Mode B” and sets itself to the “Charge Mode B”. 
         [0056]    However, as mentioned previously, once the PDA  150  establishes its own charge mode, the PDA  150  maintains the established charge mode until the connector  152  of the PDA  150  is unplugged from the connector of the power supply device, even if the power supply device changes its power supply mode. Accordingly, in order that the charge mode of the PDA  150  may be changed automatically in response to the change in the power supply mode of the cradle  100  without unplugging the connector  152  of the PDA  150  from the connector  18  of the cradle  100 , the control circuit ( FIG. 2 ) operates in the following manner. 
         [0057]    The control circuit  31  detects the rising edge and falling edge of the USB power supply voltage Vbus, and opens the switch SW 1  for a prescribed time interval after having detected these edges. The control circuit  31  then closes the switch SW 1  after the prescribed time interval has passed. Consequently, during a prescribed time interval after the rising edge and the falling edge of the USB power supply voltage Vbus, the power supply terminal a 1  is at a floating potential (assumes a floating state). Herein, the operation in which the switch SW 1  is opened for a prescribed time interval and then closed is also termed “simulated reconnection operation”, and the floating state of the power supply terminal a 1  for the prescribed time interval is also termed “simulated reconnection signal”. 
         [0058]    From the voltage level at the power supply terminal a 1 , the PDA  150  decides whether a peripheral device is connected to the connector  152 . Thus, if the power supply terminal a 1  assumes the floating state, the PDA  150  decides that the connector  152  is unplugged from the connector  18  of the cradle  100 . When the switch SW 1  is then closed again after the prescribed time interval, the PDA  150  determines that the connector  152  is connected to the connector  18  of the cradle  100 , and establishes its own charge mode in response to the power supply mode of the cradle  100 . 
         [0059]    In other words, if the power supply terminal a 1  assumes the floating state and if the power supply voltage Vc reappears at the power supply terminal a 1  after the prescribed time interval, this means that the power supply mode of the cradle  100  has already changed and the voltage level at the peripheral device type identification terminal a 2  is also changed. Consequently, when the power supply mode of the cradle  100  changes, the charge mode of the PDA  150  is automatically changed without unplugging and plugging the PDA  150  from and to the cradle  100 . 
         [0060]      FIG. 4  illustrates the state transitions of the cradle  100 . When the cradle  100  is supplied with the power supply voltage Vc from the AC/DC adapter  17 , the cradle  100  enters the “Initial Mode”. In this Initial Mode, the switch SW 1  is open. Upon entering the “Initial Mode”, the cradle  100  decides whether the USB power supply voltage Vbus is being supplied from the USB port  12 . If the USB power supply voltage Vbus is being supplied, the cradle  100  shifts to the “Power Supply Mode A”. If the USB power supply voltage Vbus is not being supplied, the cradle  100  shifts to the “Power Supply Mode B”. After the cradle  100  has shifted from the “Initial Mode” to the “Power Supply Mode A” or “Power Supply Mode B”, the switch W 1  is closed. 
         [0061]    In the “Power Supply Mode A”, the cradle  100  checks whether or not the USB power supply voltage Vbus is being supplied, and if the USB power supply voltage Vbus is not being supplied, the cradle  100  shifts to the “Power Supply Mode B”. Immediately after the cradle  100  has shifted from “Power Supply Mode A” to “Power Supply Mode B”, the connection between the PDA  150  and the cradle  100  is temporarily interrupted and thereafter the cradle  100  supplies to the PDA  150  the signal (simulated reconnection signal) which causes the PDA  150  to detect the restoration of the temporarily interrupted connection. Thus, since the PDA  150  detects the temporary interruption of its connection with the cradle  100  and the subsequent restoration of the interrupted connection, the PDA  150  can set its own charge mode to the “Charge Mode B”. 
         [0062]    In the “Power Supply Mode B”, on the other hand, the cradle  100  checks whether or not the USB power supply voltage Vbus is being supplied, and when the supply of the USB power supply voltage Vbus is initiated, the cradle  100  shifts to the “Power Supply Mode A”. Immediately after the cradle  100  has shifted from “Power Supply Mode B” to “Power Supply Mode A”, the cradle  100  supplies a simulated reconnection signal to the PDA  150 . Thus, once the PDA  150  detects the temporary interruption of its connection with the cradle  100  and the subsequent restoration of the interrupted connection, the PDA  150  can set its own charge mode to the “Charge Mode A”. 
         [0063]    In this way, according to the first embodiment, when the power supply mode of the cradle  100  is changed, the power supply terminal a 1  assumes a floating state for a prescribed time interval. Accordingly, when the power supply mode of the cradle  100  is changed, the charge mode of the PDA  150  can be changed automatically without the user unplugging and reconnecting the PDA  150  from and to the cradle  100 . 
         [0064]    Consequently, even if the computer  200  is first turned off and then turned on while the PDA  150  remains connected to the cradle  100 , data communication can be initiated between the PDA  150  and the computer  200  without the user unplugging and reconnecting the PDA  150  from and to the cradle  100 . 
         [0065]    On the other hand, if the computer  200  is first turned on and then turned off, the battery  158  of the PDA  150  can be quickly charged without the user unplugging and reconnecting the PDA  150  from and to the cradle  100 , and the time required to charge the battery  158  can be markedly reduced. The user of the PDA  150  can thereby be provided with a cradle  100  having markedly improved ease of use. 
       B. Second Embodiment 
       [0066]      FIG. 5  schematically shows the configuration of a cradle  100   b  according to a second embodiment. The difference of this embodiment from the first embodiment shown in  FIG. 2  is the provision of a CPU  50  which issues commands to the LED indicator  20  and the control circuit  31 . The rest of the configuration is the same as in the first embodiment. 
         [0067]      FIG. 6  is a flowchart for the operation of the CPU  50  of the cradle  100   b.  In Step S 10 , power supply voltage Vc is supplied to the cradle  100   b.  Upon being supplied with power supply voltage Vc, in Step S 20 , the CPU  50  outputs to the control circuit  31  a command to open the switch SW 1 , placing the cradle  100   b  in the “Initial Mode”. 
         [0068]    In Step S 30 , the CPU  50  decides whether the USB power supply voltage Vbus is being supplied to the cradle  100   b.  If the USB power supply voltage Vbus is being supplied, the CPU  50  outputs to the control circuit  31  a command to connect the peripheral device type identification terminal a 2  to ground potential GND, thereby setting the cradle  100   b  to the “Power Supply Mode A” (Step S 40 ). On the other hand, if USB power supply voltage Vbus is not supplied, the CPU  50  outputs to the control circuit  31  a command to connect the peripheral device type identification terminal a 2  to the branch line BL, thereby setting the cradle  100   b  to the “Power Supply Mode B” (Step S 50 ). 
         [0069]    After placing the cradle  100   b  in the “Power Supply Mode A” or “Power Supply Mode B”, the CPU  50  monitors the USB power supply voltage Vbus (Step S 60 ). If a state transition occurs in the USB power supply voltage Vbus (Step S 70 : Yes), the CPU  50  decides whether the USB power supply voltage Vbus is being supplied to the cradle  100   b  (Step S 80 ). On the other hand, if the state transition of the USB power supply voltage Vbus does not occur (Step S 70 : No), the CPU  50  returns to the step of monitoring the USB power supply voltage Vbus (Step S 60 ). 
         [0070]    In Step S 80 , if the USB power supply voltage Vbus is being supplied to the cradle  100   b,  the CPU  50  outputs a command to the control circuit  31  to set the cradle  100   b  in the “Power Supply Mode A” (Step S 90 ). On the other hand, if the USB power supply voltage Vbus is not being supplied to the cradle  100   b,  the CPU  50  outputs a command to the control circuit  31  to set the cradle  100   b  in the “Power Supply Mode B” (Step S 100 ). 
         [0071]    Once the cradle  100   b  is set in the “Power Supply Mode A” or the “Power Supply Mode B”, in Step S 110 , the CPU  50  outputs to the control circuit  31  a command to carry out the simulated reconnection operation. Thus, the PDA  150  detects the temporary interruption of its connection with the cradle  100  and the subsequent restoration of the temporarily interrupted connection so that the PDA  150  can change its charge mode in response to the power supply mode of the cradle  100   b  established subsequent to the power supply mode transition thereof. 
         [0072]    The CPU  50  can select between the LEDs in the LED indicator  20  to light up in response to the power supply mode of the cradle  100   b.  In the present embodiment, if the cradle  100   b  is in the “Power Supply Mode A”, the green-light emitting element  20 G is lit, or if the cradle  100  is in the “Power Supply Mode B”, the red-light emitting element  20 R is lit. 
         [0073]    In this way, in addition to the fact that the cradle  100   b  of the second embodiment can have the same advantage as the first embodiment, the CPU  50  is involved in the decision of the power supply mode of the cradle  100  so that parameters such as, for example, the timings at which the switches SW 1  to SW 3  are opened and closed can be adjusted finely and that various different operating conditions can be set. Moreover, new functions can be added to the cradle  100   b  by updating the firmware. 
       C. Modifications 
       [0074]    The present invention is not limited to the embodiments described above, but may be practiced in various other ways without departing from the spirit thereof. Modifications such as the following ones are possible, for example. 
       C1. Modification 1: 
       [0075]    In the preceding embodiments, the LED indicator  20  includes the red and green LEDs to allow the user to differentiate between the power supply modes of the cradle  100   b  (and the charge modes of the PDA  150 ). However, the LEDs in the LED indicator  20  may have different combinations of colors. Alternatively, a single LED of a color may be used and continuously lit or flashed to enable the user to differentiate between the power supply modes of the cradle  100 . Other light sources besides LEDs, such as EL (electroluminescence) elements, may also be used. The cradle  100  may also be provided with a voice generating module in place of the LED indicator  20 , enabling the user to differentiate between the power supply modes of the cradle  100  (and the charge modes of the PDA  150 ) through voices. 
       C2. Modification 2: 
       [0076]    In the preceding embodiments, the cradle  100  is provided with the USB ports  13 ,  14 , and  15 , but these may be omitted. The present invention may be embodied as a connection device of cable form having a connector for the PDA  150  and a connector for the computer  200 . 
       C3. Modification 3: 
       [0077]    In the preceding embodiments, the control circuit  31  opens and closes the switches SW 1  to SW 3  on the basis of the USB power supply voltage Vbus, but the switches SW 1  to SW 3  may be opened and closed on the basis of whether or not there is data transfer via the data terminal  3   a,  rather than on the basis of the USB power supply voltage Vbus. 
         [0078]    To be concrete, if data is being transferred via the data terminal  3   a,  the control circuit  31  sets the cradle  100  in the “Power Supply Mode A”, or if data is not being transferred via the data terminal  3   a,  the control circuit  31  sets the cradle  100  in the “Power Supply Mode B”. In fact, when data transfer is initiated or it ceases, the control circuit  31  has only to output a simulated reconnection signal. 
       C4. Modification 4: 
       [0079]    In the preceding embodiments, the PDA  150  determines the type (the power supply mode) of the power supply device connected to the connector  152  on the basis of the voltage at the peripheral device type identification terminal a 2 . Alternatively, however, the PDA  150  may determine the type (the power supply mode) of the power supply device connected to the connector  152  on the basis of whether or not there is data transfer via the data terminal  3   a.  Further, the cradle  100  may be so designed that the voltage at the data terminal a 3  takes different values according as data communication with the computer  200  takes place or not. Accordingly, the PDA  150  may be so designed as to determine the type (the power supply mode) of the power supply device connected to the connector  152  on the basis of the voltage value at this data terminal. 
       C5. Modification 5: 
       [0080]    In the preceding embodiments, the PDA  150  is described as an example of an electronic device having plural charge modes, but the electronic device may be any type of device such as, for example, a mobile phone, a portable game device, a digital camera, a portable television, a portable radio, or a portable music player, if it has plural charge modes. 
       C6. Modification 6: 
       [0081]    The circuit configurations described in the preceding embodiments may be composed of semiconductor circuits using switching elements such as transistors. Where the switches SW 1  to SW 3  are composed of transistors, the “simulated reconnection signal” corresponds to a high impedance developed between the peripheral device type identification terminal a 2  and the ground for a prescribed time interval. The CPU  50 , the USB hub controller  22 , and the simulated reconnection circuit  30  in the second embodiment may be integrated in the form of a one-chip CPU or the like. 
       C7. Modification 7: 
       [0082]    In the preceding embodiments, the AC/DC adapter  17  is provided separately from the cradle  100 , but the AC/DC adapter  17  may be integrated with the cradle  100 . 
       C8. Modification 8: 
       [0083]    Part of the functions implemented through hardware in the preceding embodiments may instead be implemented through software, and conversely part of the functions implemented through software in the preceding embodiments may instead be implemented through hardware.