Patent Publication Number: US-2012043931-A1

Title: Device housing a battery and charging apparatus for contactless charging

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a device housing a battery (batteries) such as a battery pack or mobile telephone, and to a charging apparatus that transmits power by magnetic induction to the device housing a battery to charge the battery inside. 
     2. Description of the Related Art 
     A contactless charging pad (charging stand, charging cradle) has been developed to charge a battery inside a device housing a battery such as a battery pack or a notebook computer. Battery charging is performed by transmitting power from a power supply coil (transmitting coil, primary coil) to an induction coil (receiving coil, secondary coil) by magnetic induction (refer to Japanese Laid-Open Patent Publication 2005-110409). 
     JP 2005-110409-A cites a configuration with a contactless charging pad that houses a power supply coil driven by an alternating current (AC) power source, and a device housing a battery such as a battery pack or a notebook computer that contains an induction coil, which magnetically couples with the power supply coil. The contactless charging pad disposes the power supply coil opposite the induction coil in the device housing a battery enabling the internal battery to be charged. 
     It turns out there are devices housing a battery equipped with charging terminals to connect a charging adapter and charge the internal battery without necessarily depending on the contactless charging pad. If this type of device is placed on the contactless charging pad while connected to the charging adapter, the internal battery is charged by both the charging adapter and the contactless charging pad. However, the contactless charging pad is designed to independently charge the internal battery with optimal current and voltage, and the charging adapter as well is designed to independently charge the internal battery with optimal current and voltage. Consequently, if the internal battery is charged by both the contactless charging pad and the charging adapter, the battery cannot be charged normally. 
     To resolve this drawback, a charging system has been developed that suspends charging by the charging adapter when the charging adapter is connected to a device housing a battery that is being charged by the contactless charging pad. 
     Refer to U.S. Pat. No. 4,435,788. 
     The charging system of U.S. Pat. No. 4,435,788 detects battery charging current induced from the contactless charging pad to determine if the internal battery is being charged by the contactless charging pad. If the charging adapter is connected to the device housing a battery when it is, being charged by the contactless charging pad, the charging circuit that charges the internal battery from the charging adapter does not perform charging. Therefore, when the device housing a battery is placed on the contactless charging pad, the internal battery is charged only by the contactless charging pad. 
     The charging system described above does not simultaneously charge the device battery with both the contactless charging pad and the charging adapter. However, since charging by the charging adapter is halted when contactless charging pad battery charging current is detected, rapid charging of the internal battery under optimal conditions may not always be possible. For example, the system has the drawback that even under conditions where the internal battery can be rapidly charged by the charging adapter, charging with the charging adapter may not be possible. 
     The present invention was developed with the object of correcting the drawbacks described above. Thus, it is a primary object of the present invention to provide a device housing a battery and charging apparatus that detect the charging status of both a charging adapter and the charging apparatus, which is an apparatus such as a contactless charging pad that charges the device battery without wire contact, and select optimum charging apparatus and charging adapter charging to consistently enable internal battery charging under favorable conditions. 
     SUMMARY OF THE INVENTION 
     The device housing a battery and charging apparatus of the present invention are provided with a device housing a battery  50 ,  150 , and a charging apparatus  10 ,  110  that performs contactless charging by magnetically coupling with a device housing a battery  50 ,  150  placed on the charging apparatus  10 ,  110 . The device housing a battery  50 ,  150  has an internal battery  52 ,  152 , charging terminals  72 ,  172  that connect with a charging adapter  80 ,  180  to charge the internal battery  52 ,  152 , and a contactless charging section  60  for contactless charging of the internal battery  52 ,  152  by magnetically coupling with the charging apparatus  10 ,  110 . The device housing a battery  50 ,  150  is provided with a charging apparatus detection section  61  that detects placement on the charging apparatus  10 ,  110 , an adapter detection section  62  that detects charging adapter  80 ,  180  connection or charging, and a charging selection section  63  that selects internal battery  52 ,  152  charging by either the charging apparatus  10 ,  110  or the charging adapter  80 ,  180  according to signals from the charging apparatus detection section  61  and the adapter detection section  62 . When the device housing a battery  50 ,  150  is placed on the charging apparatus  10 ,  110  and the charging adapter  80 ,  180  is connected, the charging selection section  63  controls either the charging apparatus  10 ,  110  or the charging adapter  80 ,  180  to charge the internal battery  52 ,  152 . 
     The device housing a battery and charging apparatus described above has the characteristic that both contactless charging apparatus and charging adapter charging or connection are detected, and optimum contactless charging apparatus and charging adapter charging is selected to consistently enable internal battery charging under favorable conditions. This is because the device housing a battery detects contactless charging and charging adapter charging and charges the internal battery in an optimal manner. 
     In the device housing a battery and charging apparatus of the present invention, when the device housing a battery  50 ,  150  is placed on the charging apparatus  10 ,  110  and the charging adapter  80 ,  180  is connected, the charging selection section  63  can charge the internal battery  52 ,  152  with only the charging adapter  80 ,  180  output. This device housing a battery has the characteristic that when it is placed on the contactless charging apparatus with the charging adapter connected, the internal battery can be rapidly charged under favorable conditions while limiting heat generation. 
     In the device housing a battery and charging apparatus of the present invention, the device housing a battery  50 ,  150  can be provided with a charging apparatus detection section  61  equipped with a microcomputer  64  that is operated by power output from the contactless charging section  60  to control contactless charging of the internal battery  52 ,  152 . With the microcomputer  64  in the operating state due to power supplied from the charging apparatus  10 ,  110 , the charging status of the charging apparatus  10 ,  110  can be detected by the charging apparatus detection section  61 . In this device housing a battery, the microcomputer, which is provided in the charging apparatus detection section to control internal battery charging, is not operated by the internal battery. Specifically, the charging status of the charging apparatus can be detected with a simple circuit structure while reducing unnecessary internal battery power consumption. This is because the microcomputer is operated by power supplied via magnetic coupling with the charging apparatus to detect the charging status of the charging apparatus. 
     In the device housing a battery and charging apparatus of the present invention, the adapter detection section  62  can detect charging adapter  80 ,  180  connection or charging when contactless charging is halted and at least one of the following parameters is detected: voltage of a switching device  78 A, which is a protection device  78  for the internal battery  52 ,  152  inside the device housing a battery  50 ,  150 ; voltage of the internal battery  52 ,  152 ; voltage of a temperature sensor  59  inside the device housing a battery  50 ,  150 ; signal input from the charging adapter  80 ,  180 ; voltage rise in the internal battery  52 ,  152 ; and temperature rise in the internal battery  52 ,  152 . In this device housing a battery, when contactless charging is halted and the voltage drop across the switching device exceeds a set value, the adapter detection section can judge that the charging adapter is connected. This is because charging current from the charging adapter flows through the switching device generating a voltage drop. When contactless charging is halted, the adapter detection section can detect internal battery voltage. If internal battery voltage drops, the adapter detection section can judge that the charging adapter is not connected, and if internal battery voltage does not drop, the adapter detection section can judge that the charging adapter is connected. This is because the voltage of the internal battery rises when it is being charged. Further, the adapter detection section can detect the voltage of the temperature sensor in the device housing a battery to judge charging adapter connection. This is because voltage is applied to the temperature sensor from the charging adapter when it is connected. Further, the adapter detection section can input a (charging) signal from the charging adapter to judge charging adapter connection. Further, since internal battery voltage rises when it is being charged, the adapter detection section can judge charging adapter connection from internal battery voltage rise. Further, since internal battery temperature rises when it is being charged, the adapter detection section can judge charging adapter connection from internal battery temperature rise. 
     In the device housing a battery and charging apparatus of the present invention, the device housing a battery  50 ,  150  can be provided with a timer  67  to set a time period to halt charging by the charging apparatus  10 ,  110 , and the adapter detection section  62  can detect charging adapter  80 ,  180  connection or charging during the set time period. In this device housing a battery, since contactless charging is temporarily halted with the device housing a battery placed on the charging apparatus, charging adapter connection can be reliably detected during that time period when contactless charging is halted. This is because parameters such as internal battery voltage, current, temperature, and temperature sensor voltage change depending on whether or not charging is being performed by the charging adapter. 
     In the device housing a battery and charging apparatus of the present invention, the adapter detection section  62  can be provided with a first charging current detection circuit  68  that detects internal battery  52 ,  152  charging current, and a second charging current detection circuit  69  that detects charging current output from the charging apparatus  10 ,  110 . Further, the adapter detection section  62  can detect charging by the charging adapter  80 ,  180  from the difference between the charging current detected by the first charging current detection circuit  68  and the second charging current detection circuit  69 . This device housing a battery can reliably determine if the charging adapter is connected by the current difference between the first charging current detection circuit and the second charging current detection circuit. 
     The device housing a battery and charging apparatus of the present invention can be provided with a diode  75  between the charging adapter  80 ,  180  and the internal battery  52 ,  152 , and the adapter detection section  62  can detect the adapter-side diode  75  voltage to detect charging by the charging adapter  80 ,  180 . This device housing a battery can reliably detect charging from the charging adapter with a simple circuit structure. 
     In the device housing a battery and charging apparatus of the present invention, the adapter detection section  62  can detect charging adapter  80 ,  180  connection or charging, and send a signal to the charging apparatus  10 ,  110  to halt charging, or stop internal battery  52 ,  152  charging by the contactless charging section  60 . In this device housing a battery, since power transmission from the charging apparatus can be stopped when the charging adapter is connected and charging the internal battery, unnecessary power consumption can be reduced and the internal battery can be efficiently charged. Further, when not charging the internal battery, charging apparatus power transmission can be stopped to prevent heat generation due to magnetic induction in the device housing a battery and the internal battery. 
     In the device housing a battery and charging apparatus of the present invention, the adapter detection section  62  (equivalent to an external power source detection section  242 ) is provided with an adapter detection circuit  242 C activated by voltage applied by connecting the charging adapter  80  (equivalent to an external power source  220 ), and the adapter detection circuit  242 C issues a connection signal to the adapter detection section  62  to detect charging adapter  80  connection. This device housing a battery can detect charging adapter  80  connection with a simple structure. 
     In the device housing a battery and charging apparatus of the present invention, the adapter detection circuit  242 C has a switching device SW connected between the adapter detection section  62  (equivalent to the external power source detection section  242 ) input port I and ground, and the switching device SW is activated by voltage applied by connecting the charging adapter  80  (equivalent to the external power source  220 ). Voltage application due to charging adapter  80  connection puts the switching device SW in a conducting state, and a LOW voltage level is applied as a connection signal at the input port I to detect charging adapter  80  connection. This device housing a battery can detect charging adapter  80  connection with a simple structure. The above and further objects of the present invention as well as the features thereof will become more apparent from the following detailed description to be made in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an oblique view of a device housing a battery and charging apparatus for an embodiment of the present invention; 
         FIG. 2  is an abbreviated oblique view showing the internal structure of the charging apparatus shown in  FIG. 1 ; 
         FIG. 3  is a horizontal cross-section view showing the internal structure of the charging apparatus shown in  FIG. 1 ; 
         FIG. 4  is a lengthwise vertical cross-section view of the charging apparatus shown in  FIG. 3 ; 
         FIG. 5  is a widthwise vertical cross-section view of the charging apparatus shown in  FIG. 3 ; 
         FIG. 6  is a circuit diagram showing one example of a charging apparatus position detection controller; 
         FIG. 7  is a block diagram of a device housing a battery and charging apparatus for an embodiment of the present invention; 
         FIG. 8  is a circuit diagram of the device housing a battery shown in  FIG. 7 ; 
         FIG. 9  is a waveform diagram showing an example of an echo signal output from the induction coil excited by a position detection signal; 
         FIG. 10  is a graph showing oscillation frequency as a function of the relative positional offset of the power supply coil and the induction coil; 
         FIG. 11  is an oblique view of a device housing a battery and charging apparatus for another embodiment of the present invention; 
         FIG. 12  is an abbreviated cross-section view illustrating charging of the battery in the device housing a battery shown in  FIG. 11 ; 
         FIG. 13  is a block diagram of the device housing a battery and charging apparatus shown in  FIG. 11 ; 
         FIG. 14  is a circuit diagram showing the position detection controller of the charging apparatus shown in  FIG. 11 ; 
         FIG. 15  is a block diagram of a battery pack for an embodiment of the present invention; and 
         FIG. 16  is a block diagram showing a battery pack placed on a charging pad for an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENT(S) 
     The following describes embodiments of the present invention based on the figures. However, the following embodiments are merely specific examples of a device housing a battery and charging apparatus representative of the technology associated with the present invention, and the device housing a battery and charging apparatus of the present invention are not limited to the embodiments described below. Further, components indicated in the appended claims are in no way limited to the components indicated in the embodiments. 
       FIGS. 1-7  show structural overviews and diagrams illustrating the operating principles of the charging apparatus  10 . As shown in  FIGS. 1 ,  2 , and  7 , a device housing a battery  50  is placed on top of the charging apparatus  10  and power is transmitted by magnetic induction to charge the internal battery  52 . The device housing a battery  50  is provided with an internal battery  52 , charging terminals  72  that connect with a charging adapter  80  that charges the internal battery  52 , and a contactless charging section  60  that charges the internal battery  52  in a contactless manner by magnetic coupling. The contactless charging section  60  is provided with an induction coil  51  that magnetically couples with a power supply coil  11  in the charging apparatus  10 , and the internal battery  52  is charged by power induced in the induction coil  51 . 
       FIG. 8  shows a circuit diagram of the device housing a battery  50 . 
     The device housing a battery  50  contains a battery pack  70  as the internal battery  52 , and the battery pack  70  is housed in a removable manner. The battery pack  70  in the device housing a battery  50  holds the contactless charging section  60  that charges the internal battery  52  in a contactless manner. The contactless charging section  60  is provided with the induction coil  51  that magnetically couples with the charging apparatus  10  power supply coil  11 , a rectifying circuit  53  that rectifies AC induced in the induction coil  51 , and a control circuit  54  that controls internal battery  52  charging with output from the rectifying circuit  53 . In addition, the device housing a battery  50  contains a charging circuit  71  that charges the battery pack  70  internal battery  52  with the external charging adapter  80  connected through the charging terminals  72 . Although the device housing a battery  50  described above is configured with an internal battery  52  that is a removable battery pack  70 , a fixed internal battery can also be contained in the device housing a battery in a non-removable manner. In that case, the device housing a battery holds the induction coil in the contactless charging section, the internal battery, and the control circuit. 
     The control circuit  54  is provided with a charging apparatus detection section  61  that detects placement of the device housing a battery  50  on the charging apparatus  10 , an adapter detection section  62  that detects connection or charging by the charging adapter  80  that connects to the device housing a battery  50  to charge the internal battery  52 , and a charging selection section  63  that selects internal battery  52  charging by either the charging apparatus  10  or the charging adapter  80  according to signals from the charging apparatus detection section  61  and the adapter detection section  62 . 
     When the device housing a battery  50  is placed on the charging apparatus  10  and the charging adapter  80  is also connected, the charging selection section  63  of the control circuit  54  controls internal battery  52  charging by either the charging apparatus  10  or the charging adapter  80 . In the case where the device housing a battery  50  is placed on the charging apparatus  10  and the charging adapter  80  is connected, namely, when the internal battery  52  can be charged by either the charging apparatus  10  or the charging adapter  80 , the control circuit  54  preferably charges the internal battery  52  only with power supplied from the charging adapter  80  and not with power transmitted from the charging apparatus  10 . However, when the device housing a battery  50  is placed on the charging apparatus  10  and the charging adapter  80  is connected, the internal battery  52  can also be charged only with power transmitted from the charging apparatus  10  and not with power supplied from the charging adapter  80 . 
     The control circuit  54  is equipped with a microcomputer  64  and switches  65 ,  66  that are switched ON and OFF by the microcomputer  64 . The charging apparatus detection section  61 , the adapter detection section  62 , and the charging selection section  63  are implemented by the microcomputer  64  control circuit  54 . The microcomputer  64  charging apparatus detection section  61  detects placement of the device housing a battery  50  on the charging apparatus  10 , or charging by the charging apparatus  10 . As its power supply voltage, the microcomputer  64  operates by power output from the rectifying circuit  53 , which converts induction coil  51  output to direct current (DC), and does not operate by power supplied from the internal battery  52 . Specifically, the microcomputer  64  does not consume operating power from the internal battery  52 , but rather operates on power supplied by magnetic induction from the charging apparatus  10 . Accordingly, when the device housing a battery  50  is placed on the charging apparatus  10 , the microcomputer  64  is activated and becomes operational. The charging apparatus detection section  61  detects placement of the device housing a battery  50  on the charging apparatus  10  by detecting microcomputer  64  activation. This charging apparatus detection section  61  can detect placement on the charging apparatus  10  with a simple circuit structure. However, the present invention is not limited to a charging apparatus detection section with this circuit structure. This is because, for example, a signal can be received from charging apparatus to also detect placement on the charging apparatus. 
     The adapter detection section  62  detects charging adapter  80  connection or internal battery  52  charging by the charging adapter  80 . The adapter detection section  62  detects charging adapter  80  connection or charging while contactless charging is in a halted state. Contactless charging is halted by switching OFF the switch  65  connected between the rectifying circuit  53  and the internal battery  52 . The control circuit  54  microcomputer  64  holds the switch  65  OFF to halt contactless charging for the time period when charging adapter  80  connection or charging is being detected. 
     With contactless charging in the halted state, the adapter detection section  62  detects charging adapter  80  connection to, or charging of the device housing a battery  50  by detecting any one of the following conditions (1)-(6), or by detecting a plurality of those conditions. The time period for detection of charging adapter  80  connection or charging is set by a timer  67 . The timer  67  is provided in the control circuit  54  and stores the time period for detection of charging adapter  80  connection or charging. Charging adapter  80  connection or charging is detected during the set time period of the timer  67 . 
     (1) The voltage drop across a battery pack  70  protection device  78  is detected to detect charging adapter  80  charging. To protect the internal battery  52  from over-current during charging and discharging, a switching device  78 A such as a field effect transistor (FET) or bipolar transistor is connected between the internal battery  52  and the load  79  of the device housing a battery  50 . When the charging adapter  80  is connected and the internal battery  52  is being charged by the charging adapter  80 , charging current flows through the switching device  78 A generating a voltage drop. When the charging adapter  80  is not connected, no charging current flows in through the switching device  78 A and no voltage drop is generated. The voltage drop due to charging current flow is proportional to product of the ON-resistance of the switching device  78 A and the charging current. Accordingly, with contactless charging halted, when the voltage drop across the switching device  78 A implementing the protection device  78  exceeds a set value, the adapter detection section  62  judges that the internal battery  52  is being charged from the charging adapter  80 . 
     (2) The internal battery  52  voltage is detected to detect charging adapter  80  charging. The voltage of the internal battery  52  is higher when it is being charged than when it is not being charged. Consequently, the adapter detection section  62  can determine whether or not the charging adapter  80  is charging the internal battery  52  by detecting the internal battery  52  voltage. In particular, charging by the charging adapter  80  can be determined more accurately by detecting internal battery  52  voltage while switching contactless charging ON and OFF. When the internal battery  52  is being charged by the charging adapter  80 , the internal battery  52  is continuously charged and there is little change in the voltage even if contactless charging is switched ON and OFF. In contrast, when the internal battery  52  is not being charged by the charging adapter  80  and contactless charging is switched ON and OFF, the internal battery  52  switches between a state of charging and a state of no charging, and there is a large change in voltage. Consequently, if internal battery  52  voltage rises when contactless charging is switched from OFF to ON and drops when contactless charging is switched from ON to OFF, the adapter detection section  62  judges that the charging adapter  80  is not charging. Conversely, if there is little internal battery  52  voltage change when contactless charging is switched ON and OFF, the adapter detection section  62  judges that charging is being performed by the charging adapter  80 . 
     (3) Charging adapter  80  connection is detected by voltage in a temperature sensor  59  that detects internal battery  52  temperature. When the charging adapter  80  is connected to the device housing a battery  50 , voltage rises in the temperature sensor  59  that detects internal battery  52  temperature. This is because the temperature sensor  59  connects to a power supply  74  through a pull-up resistor  73  when the charging adapter  80  is connected. When the charging adapter  80  is not connected, the temperature sensor  59  is not connected to the power supply  74  through the pull-up resistor. Specifically, when the charging adapter  80  is not connected, temperature sensor  59  voltage is approximately 0V, and when the charging adapter  80  is connected, the temperature sensor  59  connects to the power supply  74  through the pull-up resistor and its voltage rises. Therefore, the adapter detection section  62  can detect charging adapter  80  connection and charging by detecting temperature sensor  59  voltage. 
     (4) Charging adapter  80  connection can be determined by detecting a signal input from the charging adapter  80 . In this circuit configuration, the charging adapter  80  outputs a specified signal, the adapter detection section  62  receives that signal, and charging adapter  80  connection or charging is detected. 
     (5) Internal battery  52  voltage rise is detected to detect internal battery  52  charging by the charging adapter  80 . When the internal battery  52  is charged by the charging adapter  80 , its voltage gradually rises. Accordingly, the adapter detection section  62  can detect charging adapter  80  charging by detecting the rate of internal battery  52  voltage rise. When the charging adapter  80  is not charging the internal battery  52 , there is no internal battery  52  voltage rise. When the internal battery  52  is being charged by the charging adapter  80 , the rate of voltage rise increases. Consequently, the adapter detection section  62  can detect charging by the charging adapter  80  by detecting the rate of internal battery  52  voltage rise in a unit time period. 
     (6) The rate of internal battery  52  temperature rise is detected to detect internal battery  52  charging by the charging adapter  80 . When the internal battery  52  is charged by the charging adapter  80 , its temperature gradually rises. Accordingly, the adapter detection section  62  can detect charging adapter  80  charging by detecting the rate of internal battery  52  temperature rise. When the charging adapter  80  is not charging the internal battery  52 , there is little internal battery  52  temperature rise. When the internal battery  52  is being charged by the charging adapter  80 , the rate of temperature rise increases. Consequently, the adapter detection section  62  can detect charging by the charging adapter  80  when contactless charging is halted by detecting the rate of internal battery  52  temperature rise. 
     In addition, the adapter detection section  62  can detect charging by the charging adapter  80  without halting contactless charging. This adapter detection section  62  is provided with a first charging current detection circuit  68  that detects internal battery  52  charging current, and a second charging current detection circuit  69  that detects charging current output from the charging apparatus  10 . Charging by the charging adapter  80  is detected from the difference between charging current detected by the first charging current detection circuit  68  and the second charging current detection circuit  69 . 
     Since the first charging current detection circuit  68  detects internal battery  52  charging current, it detects charging current that is the sum of charging current from the charging apparatus  10  and charging current from the charging adapter  80 . In contrast, the second charging current detection circuit  69  detects only charging current from the charging apparatus  10 . Accordingly, when the internal battery  52  is charged only by the charging apparatus  10 , current detected by the first charging current detection circuit  68  becomes the same value as the current detected by the second charging current detection circuit  69 . Consequently, when the same current is detected by the first charging current detection circuit  68  and the second charging current detection circuit  69 , it is judged that the internal battery  52  is only being charged by the charging apparatus  10  and not by the charging adapter  80 . When both the charging apparatus  10  and the charging adapter  80  are charging the internal battery  52 , current detected by the first charging current detection circuit  68  becomes greater than that detected by the second charging current detection circuit  69 . Under these conditions, it can be judged that the internal battery  52  is being charged by the charging adapter  80 . 
     Further, the device housing a battery  50  is provided with a diode  75  between the charging adapter  80  and the internal battery  52 , and the adapter detection section  62  can detect charging adapter  80  charging by detecting the adapter-side diode  75  voltage. In the device housing a battery  50  of  FIG. 8 , an output line from the rectifying circuit  53  connects with an output line from the charging circuit  71  at a connection node  76  on the positive output-side of the internal battery  52 . The diode  75  is connected on the charging circuit  71  side of the switch  66  between the connection node  76  and the charging circuit  71 . The diode  75  is connected with a polarity that passes current from the charging circuit  71  to the internal battery  52 . The adapter detection section  62  can detect the charging status of the charging adapter  80  by detecting whether or not there is a voltage on the charging circuit  71  side of the diode  75 . This is because no voltage is detected at the charging circuit  71  side of the diode  75  when the charging adapter  80  is not connected and the charging circuit  71  is not charging the internal battery  52 , but voltage is detected when the charging adapter  80  is connected and power is supplied to the internal battery  52  from the charging circuit  71 . This configuration can also detect charging by the charging adapter  80  with a simple circuit structure and without halting contactless charging. In the device housing a battery  50  of  FIG. 8 , the diode  75  is connected on the charging circuit  71  side of the switch  66 . However, the diode can also be connected on the connection node-side of the switch or between the charging circuit and the charging terminal. 
     An adapter detection section  62 , which detects charging by the charging adapter  80  while charging with both the charging apparatus  10  and the charging adapter  80 , temporarily charges the internal battery  52  with both the charging apparatus  10  and the charging adapter  80 . In this situation, the internal battery  52  cannot be charged under favorable conditions. Therefore, the time period for detecting charging by the charging adapter  80  with the internal battery  52  charged by both the charging apparatus  10  and the charging adapter  80  is set as short as possible. This set time period is stored in the timer  67 . During the set time period of the timer  67 , the adapter detection section  62  determines charging by the charging adapter  80 , and subsequently the charging selection section  63  controls internal battery  52  charging only by the charging adapter  80 . 
     When the control circuit  54  charging apparatus detection section  61  detects placement on the charging apparatus  10  and the adapter detection section  62  detects charging adapter  80  connection or charging, the charging selection section  63  sends a halt-charging-signal to the charging apparatus  10  to halt charging by the charging apparatus  10 , and charges the internal battery  52  with the charging adapter  80 . When the device housing a battery  50  is not placed on the charging apparatus  10  and the charging adapter  80  is connected, the control circuit  54  charges the internal battery  52  with the charging adapter  80 . The control circuit  54  charging apparatus detection section  61  and adapter detection section  62  are provided to prevent charging by both the charging apparatus  10  and the charging adapter  80 . When the device housing a battery  50  is not placed on the charging apparatus  10 , there is no need to detect charging adapter  80  connection or charging with the adapter detection section  62 . This is because the internal battery  52  can be charged under ideal conditions by the charging adapter  80 . Since the adapter detection section  62  only detects charging adapter  80  connection or charging when the device housing a battery  50  is placed on the charging apparatus  10 , it is not necessary for the adapter detection section  62  to detect charging adapter  80  connection or charging when the device housing a battery  50  is not placed on the charging apparatus  10 . Accordingly, a device housing a battery  50  that operates the control circuit  54  microcomputer  64  with power transmitted from the charging apparatus  10  only activates the microcomputer  64  to detect charging adapter  80  connection and charging. However, the control circuit  54  charging apparatus detection section  61  and adapter detection section  62  can also be continuously operated to detect placement on the charging apparatus  10  and charging adapter  80  connection and charging. In that case, when the device housing a battery  50  is placed on the charging apparatus  10  and the charging adapter  80  is not connected, the control circuit  54  charges the internal battery  52  from the charging apparatus  10 , and when the device housing a battery  50  is not placed on the charging apparatus  10  and the charging adapter  80  is connected, the control circuit  54  charges the internal battery  52  from the charging adapter  80 . 
     The control circuit  54  in  FIG. 8  holds a signal switch  57 , which is connected in series with a parallel capacitor  56  connected in parallel with the induction coil  51 , ON to send a halt-charging-signal to the charging apparatus  10 . The charging apparatus  10  detects connection of the parallel capacitor  56  to the induction coil  51  and stops delivering AC to the power supply coil  11 . The control circuit  54  can also switch the signal switch  57  ON and OFF in a prescribed manner (instead of holding it in the ON state) to convey connection of the charging adapter  80  to the charging apparatus  10 . In that case, the charging apparatus  10  detects ON and OFF switching of the signal switch  57  to detect charging adapter  80  connection and stops delivering AC to the power supply coil  11 . A system that stops the charging apparatus  10  from charging the internal battery  52  by halting the input of AC to the power supply coil  11  not only reduces unnecessary power consumption, but also prevents detrimental heating of the device housing a battery  50  and battery pack  70  by power output from the power supply coil  11 . However, when charging adapter  80  connection or charging is detected, AC output to the power supply coil  11  does not necessarily have to be stopped, and the control circuit  54  in the battery pack  70  can also turn OFF the switch  65  to cut-off charging current to the internal battery  52  and stop charging by the charging apparatus  10 . 
     The rectifying circuit  53  rectifies AC power induced in the induction coil  51  and outputs the rectified power to the control circuit  54 . The device housing a battery  50  of the figures has a series capacitor  55  connected between the induction coil  51  and the rectifying circuit  53 , and AC power induced in the induction coil  51  is input to the rectifying circuit  53  through that series capacitor  55 . The series capacitor  55  forms a series resonant circuit with the induction coil  51  to efficiently input AC power induced in the induction coil  51  to the rectifying circuit  53 . Accordingly, the capacitance of the series capacitor  55  is selected to combine with the induction coil  51  inductance for an overall impedance having a minimum near the frequency of the induced AC power. In addition, the device housing a battery  50  of the figures has an electrolytic capacitor  58  connected at the output-side of the rectifying circuit  53  to smooth ripple current in the rectifying circuit  53  output. 
     As shown in  FIGS. 1-7 , the charging apparatus  10  is provided with the power supply coil  11  connected to an AC power source  12  to induce electromotive force (emf) in the induction coil  51 , and a case  20  housing the power supply coil  11  and having a top plate  21  where a device housing a battery  50  is placed. The power supply coil  11  magnetically couples with the induction coil  51  to transmit power. The device housing a battery  50  induction coil  51  and the power supply coil  11  are positioned to magnetically couple the coils and transmit power from the power supply coil  11  to the induction coil  51 . The power supply coil  11  can be made large to increase the effective area for induction coil  51  placement and transmission of power from the power supply coil  11  to the induction coil  51 . A preferable charging apparatus  10  implementation moves the power supply coil  11  to the position of the induction coil  51  in the device housing a battery  50  placed on the case  20 . This charging apparatus  10  can efficiently transmit power from the power supply coil  11  to the induction coil  51 . 
     As shown in the figures, a charging apparatus  10  that moves the power supply coil  11  to the position of the induction coil  51  is provided with a moving mechanism  13  housed in the case  20  that moves the power supply coil  11  along the inside surface of the top plate  21 , and a position detection controller  14  that detects the position of the device housing a battery  50  placed on the top plate  21  and controls the moving mechanism  13  to move the power supply coil  11  in close proximity to the induction coil  51  in the device housing a battery  50 . The charging apparatus  10  described above houses the power supply coil  11 , the AC power source  12 , the moving mechanism  13 , and the position detection controller  14  inside the case  20 . 
     The charging apparatus  10  charges the battery  52  inside a device housing a battery  50  in the following manner. 
     (1) When a device housing a battery  50  is placed on the top plate  21  of the case  20 , the position detection controller  14  detects its position.
 
(2) The position detection controller  14 , which has detected the position of the device housing a battery  50 , controls the moving mechanism  13  to move the power supply coil  11  along the inside of the top plate  21  and position it in close proximity to the induction coil  51  of the device housing a battery  50 .
 
(3) The power supply coil  11 , which has been moved close to the induction coil  51 , is magnetically coupled to the induction coil  51  and transmits AC power to the induction coil  51 .
 
(4) The device housing a battery  50  converts the induction coil  51  AC power to DC and charges the internal battery  52  with that DC power.
 
     The charging apparatus  10 , which charges the battery  52  in the device housing a battery  50  by the procedure described above, houses the power supply coil  11  connected to the AC power source  12  inside the case  20 . The power supply coil  11  is disposed beneath the top plate  21  of the case  20  in a horizontal orientation that allows it to move along the inside of the top plate  21 . The efficiency of power transmission from the power supply coil  11  to the induction coil  51  is improved by narrowing the gap between the power supply coil  11  and the induction coil  51 . With the power supply coil  11  moved into close proximity with the induction coil  51 , the gap between the power supply coil  11  and the induction coil  51  is preferably less than or equal to 7 mm. Therefore, the power supply coil  11  is disposed under the top plate  21  and positioned as close as possible to the top plate  21 . Since the power supply coil  11  is moved close to the induction coil  51  of the device housing a battery  50  placed on the top plate  21 , the power supply coil ills disposed in a manner that allows it to move along the inside surface of the top plate  21 . 
     The case  20  that houses the power supply coil  11  is provided with a planar top plate  21  where a device housing a battery  50  can be placed. The charging apparatus  10  of  FIGS. 1 and 2  has a top plate  21  that is entirely planar and disposed horizontally. The top plate  21  is made large enough to allow placement of devices housing a battery  50  having different sizes and shapes. For example, the top plate  21  can have a rectangular shape with a side having a length of 5 cm to 30 cm. However, the top plate  21  can also have a circular shape with a diameter of 5 cm to 30 cm. The charging apparatus  10  of  FIGS. 1 and 2  has a large top plate  21  that allows simultaneous placement of a plurality of devices housing a battery  50 . Here, a plurality of devices housing a battery  50  can be placed on the top plate  21  at the same time to allow sequential charging of their internal batteries  52 . Further, the top plate can also be provided with side-walls or other barriers around its perimeter, and devices housing a battery can be placed inside the side-walls to charge the internal batteries. 
     The power supply coil  11  is wound in a plane parallel to the top plate  21 , and radiates AC magnetic flux above the top plate  21 . This power supply coil  11  emits AC magnetic flux perpendicular to, and beyond the top plate  21 . The power supply coil  11  is supplied with AC power from the AC power source  12  and radiates AC magnetic flux above the top plate  21 . 
       FIG. 7  is a circuit diagram showing connection of the AC power source  12  to the power supply coil  11 . The AC power source  12  in this figure is provided with a switching power supply  16  that converts input commercial power  81  to DC, a switching device  18  that converts DC output from the switching power supply  16  to AC supplied to the power supply coil  11 , and a switching circuit  19  that controls the switching device  18 . 
     The power supply coil  11  is moved in close proximity to the induction coil  51  by the moving mechanism  13 . The moving mechanism  13  of  FIGS. 2-5  moves the power supply coil  11  along the inside of the top plate  21  in the X-axis and Y-axis directions to position it close to the induction coil  51 . The moving mechanism  13  of the figures rotates threaded rods  23  via servo motors  22  controlled by the position detection controller  14  to move nut blocks  24  that are threaded onto the threaded rods  23 . The nut blocks  24  are moved to move the power supply coil  11  close to the induction coil  51 . The servo motors  22  are provided with an X-axis servo motor  22 A to move the power supply coil  11  in the X-axis direction, and a Y-axis servo motor  22 B to move the power supply coil  11  in the Y-axis direction. The threaded rods  23  are provided with a pair of X-axis threaded rods  23 A to move the power supply coil  11  in the X-axis direction, and a Y-axis threaded rod  23 B to move the power supply coil  11  in the Y-axis direction. The pair of X-axis threaded rods  23 A are disposed parallel to each other, and are connected via belts  25  to rotate together when driven by the X-axis servo motor  22 A. The threaded nut blocks  24  are provided with a pair of X-axis nut blocks  24 A that are threaded onto each X-axis threaded rod  23 A, and a Y-axis nut block  24 B that is threaded onto the Y-axis threaded rod  23 B. Both ends of the Y-axis threaded rod  23 B are connected to the X-axis nut blocks  24 A in a manner allowing the rod to rotate. The power supply coil  11  is mounted on the Y-axis nut block  24 B. 
     Further, the moving mechanism  13  of the figures has a guide rod  26  disposed parallel to the Y-axis threaded rod  23 B to move the power supply coil  11  in the Y-axis direction while retaining it in a horizontal orientation. The guide rod  26  is connected at both ends to the X-axis nut blocks  24 A and moves together with the pair of X-axis nut blocks  24 A. The guide rod  26  passes through a guide block  27  attached to the power supply coil  11  to allow power supply coil  11  movement along the guide rod  26  in the Y-axis direction. Specifically, the power supply coil  11  is moved with horizontal orientation in the Y-axis direction via the Y-axis nut block  24 B and guide block  27  that move along the parallel disposed Y-axis threaded rod  23 B and guide rod  26 . 
     When the X-axis servo motor  22 A rotates the X-axis threaded rods  23 A of this moving mechanism  13 , the pair of X-axis nut blocks  24 A moves along the X-axis threaded rods  23 A to move the Y-axis threaded rod  23 B and the guide rod  26  in the X-axis direction. When the Y-axis servo motor  22 B rotates the Y-axis threaded rod  23 B, the Y-axis nut block  24 B moves along the Y-axis threaded rod  23 B to move the power supply coil  11  in the Y-axis direction. Here, the guide block  27  attached to the power supply coil  11  moves along the guide rod  26  to maintain the power supply coil  11  in a horizontal orientation during movement in the Y-axis direction. Consequently, rotation of the X-axis servo motor  22 A and Y-axis servo motor  22 B can be controlled by the position detection controller  14  to move the power supply coil  11  in the X-axis and Y-axis directions. However, the charging apparatus of the present invention is not limited to a moving mechanism with the configuration described above. This is because any configuration of moving mechanism can be used that can move the power supply coil in the X-axis and Y-axis directions. 
     The position detection controller  14  detects the position of a device housing a battery  50  that is placed on the top plate  21 . The position detection controller  14  of  FIGS. 2-5  detects the position of the induction coil  51  housed in the device housing a battery  50 , and moves the power supply coil  11  close to the induction coil  51 . 
     The position detection controller  14  controls the moving mechanism  13  to position the power supply coil  11  in close proximity to the induction coil  51 . As shown in  FIG. 6 , the position detection controller  14  is provided with a plurality of position detection coils  30  fixed to the inside of the top plate  21 , a detection signal generating circuit  31  that supplies position detection signals to the position detection coils  30 , a receiving circuit  32  that receives echo signals from the position detection coils  30  resulting from excitation of the induction coil  51  by position detection signals supplied to the position detection coils  30  from the detection signal generating circuit  31 , and a discrimination circuit  33  that determines induction coil  51  position from the echo signals received by the receiving circuit  32 . 
     The position detection coils  30  are made up of a plurality of coils in rows and columns. The plurality of position detection coils  30  is fixed with specified intervals between each coil on the inside surface of the top plate  21 . The position detection coils  30  are provided with a plurality of X-axis detection coils  30 A that detect induction coil  51  position on the X-axis, and a plurality of Y-axis detection coils  30 B that detect induction coil  51  position on the Y-axis. Each X-axis detection coil  30 A is a long narrow loop extending in the Y-axis direction, and the X-axis detection coils  30 A are fixed to the inside of the top plate  21  at specified intervals. The interval (d) between adjacent X-axis detection coils  30 A is smaller than the outside diameter (D) of the induction coil  51 , and preferably the interval (d) between X-axis detection coils  30 A is from ¼ times to 1 times the induction coil  51  outside diameter (D). The position of the induction coil  51  on the X-axis can be detected more accurately by reducing the interval (d) between X-axis detection coils  30 A. Each Y-axis detection coil  30 B is a long narrow loop extending in the X-axis direction, and the Y-axis detection coils  30 B are also fixed to the inside of the top plate  21  at specified intervals. In the same manner as the X-axis detection coils  30 A, the interval (d) between adjacent Y-axis detection coils  30 B is smaller than the outside diameter (D) of the induction coil  51 , and preferably the interval (d) between Y-axis detection coils  30 B is from ¼ times to 1 times the induction coil  51  outside diameter (D). The position of the induction coil  51  on the Y-axis can also be detected more accurately by reducing the interval (d) between Y-axis detection coils  30 B. 
     The detection signal generating circuit  31  issues pulse signals, which are the position detection signals, with a specified timing. A position detection coil  30 , in which a position detection signal has been input, excites a nearby induction coil  51  via the position detection signal. The induction coil  51 , which has been excited by a position detection signal, outputs an echo signal, which is generated by the energy of the induced current flow, and that echo signal is detected by the position detection coil  30 . Specifically, as shown in  FIG. 9 , following a given delay time after a position detection signal has been input, the induction coil  51  generates an echo signal, and that echo signal is induced in the position detection coil  30  near the induction coil  51 . In the previously described device housing a battery  50 , the signal switch  57  is switched ON during position detection signal input to connect the parallel capacitor  56  to the induction coil  51  and form a parallel resonant circuit. This has the characteristic that the amplitude can be increased for the echo signal output from the induction coil  51  corresponding to position detection signal input. Accordingly, induction coil  51  position can be detected more accurately. The echo signal induced in the position detection coil  30  is sent from the receiving circuit  32  to the discrimination circuit  33 . The discrimination circuit  33  uses the echo signal input from the receiving circuit  32  to determine if the induction coil  51  is close to the position detection coil  30 . When echo signals are induced in a plurality of position detection coils  30 , the discrimination circuit  33  determines that the position detection coil  30  with the largest amplitude echo signal is closest to the induction coil  51 . 
     The position detection controller  14  shown in  FIG. 6  connects each position detection coil  30  to the receiving circuit  32  via a switching matrix  34 . Since this position detection controller  14  can connect a plurality of position detection coils  30  by sequential switching, echo signals from a plurality of position detection coils  30  can be detected with one receiving circuit  32 . However, a receiving circuit can also be connected to each position detection coil to detect the echo signals. 
     In the position detection controller  14  of  FIG. 6 , the discrimination circuit  33  controls the switching matrix  34  to sequentially switch each of the position detection coils  30  for connection to the receiving circuit  32 . Since the detection signal generating circuit  31  is connected outside the switching matrix  34 , it outputs position detection signals to each position detection coil  30 . The amplitude of the position detection signals output from the detection signal generating circuit  31  to the position detection coils  30  is extremely large compared to the echo signals from the induction coil  51 . The receiving circuit  32  has a diode connected to its input-side that forms a voltage limiting circuit  35 . Position detection signals input to the receiving circuit  32  from the detection signal generating circuit  31  are voltage limited by the limiting circuit  35 . Low amplitude echo signals are input to the receiving circuit  32  without voltage limiting. The receiving circuit  32  amplifies and outputs both position detection signals and the echo signals. An echo signal output from the receiving circuit  32  is a signal that is delayed from the position detection signal by a given delay time such as several μsec to several hundred μsec. Since the echo signal delay time from the position detection signal is constant, a signal received after the constant delay time is assumed to be an echo signal, and the proximity of a position detection coil  30  to the induction coil  51  is determined from the amplitude of that echo signal. 
     The receiving circuit  32  is an amplifier that amplifies echo signals input from the position detection coils  30 . The receiving circuit  32  outputs each position detection signal and echo signal. The discrimination circuit  33  determines if the induction coil  51  is placed next to a position detection coil  30  from the position detection signal and echo signal input from the receiving circuit  32 . The discrimination circuit  33  is provided with an analog-to-digital (A/D) converter  36  to convert the signals input from the receiving circuit  32  to digital signals. Digital signals output from the ND converter  36  are processed to detect the echo signals. The discrimination circuit  33  detects a signal that is delayed from the position detection signal by a given delay time as an echo signal, and determines if the induction coil  51  is close to the position detection coil  30  from the amplitude of the echo signal. 
     The discrimination circuit  33  controls the switching matrix  34  to sequentially connect each of the plurality of X-axis detection coils  30 A to the receiving circuit  32  to detect the position of the induction coil  51  along the X-axis. For each X-axis detection coil  30 A connected to the receiving circuit  32 , the discrimination circuit  33  outputs a position detection signal to that X-axis detection coil  30 A and determines if the induction coil  51  is close to that X-axis detection coil  30 A by detection or lack of detection of an echo signal after a given delay time from the position detection signal. The discrimination circuit  33  connects each one of the X-axis detection coils  30 A to the receiving circuit  32 , and determines if the induction coil  51  is close to any of the X-axis detection coils  30 A. If the induction coil  51  is close to one of the X-axis detection coils  30 A, an echo signal will be detected when that X-axis detection coil  30 A is connected to the receiving circuit  32 . Consequently, the discrimination circuit  33  can determine the position of the induction coil  51  along the X-axis from the X-axis detection coil  30  that outputs an echo signal. When the induction coil  51  straddles a plurality of X-axis detection coils  30 , echo signals can be detected by a plurality of X-axis detection coils  30 A. In that case, the discrimination circuit  33  determines that the induction coil  51  is closest to the X-axis detection coil  30 A that detects the strongest echo signal, which is the echo signal with the largest amplitude. The discrimination circuit  33  controls the Y-axis detection coils  30 B in the same manner to determine the position of the induction coil  51  along the Y-axis. 
     The discrimination circuit  33  controls the moving mechanism  13  according to the detected X-axis position and Y-axis position to move the power supply coil  11  close to the induction coil  51 . The discrimination circuit  33  controls the X-axis servo motor  22 A to move the power supply coil  11  to the induction coil  51  position on the X-axis. Further, the discrimination circuit  33  controls the Y-axis servo motor  22 B to move the power supply coil  11  to the induction coil  51  position on the Y-axis. 
     The position detection controller  14  moves the power supply coil  11  to a position close to the induction coil  51  in the manner described above. The position detection controller  14  moves the power supply coil  11  close to the induction coil  51 , and subsequently power is transmitted from the power supply coil  11  to the induction coil  51  to charge the internal battery  52 . However, the charging apparatus can further refine the position of the power supply coil  11  and move it still closer to the induction coil  51  and subsequently transmit power and charge the internal battery  52 . A position detection controller  15  that can accurately detect induction coil  51  position has an AC power source  12  that is a self-excited oscillator circuit. The position detection controller  15  controls the moving mechanism  13  to move the power supply coil  11  to a position accurately determined by the oscillating frequency of the self-excited oscillator circuit. The position detection controller  15  controls the moving mechanism  13  X-axis servo motor  22 A and Y-axis servo motor  22 B to move the power supply coil  11  along the X and Y-axes while detecting the AC power source  12  oscillating frequency. Self-excited oscillator circuit oscillating frequency characteristics are shown in  FIG. 10 . This figure shows the oscillating frequency as a function of the relative offset (displacement) between the power supply coil  11  and the induction coil  51 . As shown in this figure, the oscillating frequency of the self-excited oscillator circuit has a maximum where the power supply coil  11  and induction coil  51  are closest, and the oscillating frequency drops off as the two coils become separated. The position detection controller  15  controls the moving mechanism  13  X-axis servo motor  22 A to move the power supply coil  11  along the X-axis, and stops the power supply coil  11  where the oscillating frequency reaches a maximum. Similarly, the position detection controller  15  controls the Y-axis servo motor  22 B in the same manner to move the power supply coil  11  along the Y-axis, and stops the power supply coil  11  where the oscillating frequency reaches a maximum. The position detection controller  15  can move the power supply coil  11  in the manner described above to a position that is closest to the induction coil  51 . 
     When an echo signal is detected, the charging apparatus  10  discrimination circuit  43  can recognize and distinguish that an induction coil  51  of a device housing a battery  50  has been placed on the charging apparatus. When a waveform is detected and determined to be different from an echo signal waveform, an object other than the induction coil  51  of a device housing a battery  50  (for example, a metal foreign object) is assumed to be on the charging apparatus and the supply of power can be terminated. In addition, when no echo signal waveform is detected, it is assumed that no device housing a battery  50  induction coil  51  has been placed on the charging apparatus and power is not supplied. 
     The charging apparatus  10  position detection controller  14 ,  15  controls the moving mechanism  13  to move the power supply coil  11  close to the induction coil  51 . In this state, AC power is supplied to the power supply coil  11  from the AC power source  12 . AC power from the power supply coil  11  is transmitted to the induction coil  51  and used to charge the battery  52 . When full-charge of the battery  52  is detected in the device housing a battery  50 , charging is stopped and a full-charge signal is sent to the charging apparatus  10 . 
     The device housing a battery  50  can output a full-charge signal to the induction coil  51 , and the full-charge signal can be sent from the induction coil  51  to the power supply coil  11  to transmit full-charge information to the charging apparatus  10 . The device housing a battery  50  can output an AC signal to the induction coil  51  with a frequency different from that of the AC power source  12 , and the charging apparatus  10  can receive that AC signal with the power supply coil  11  to detect full-charge. Or, the device housing a battery  50  can output a full-charge signal to the induction coil  51  that is a modulated carrier wave with a specified frequency, and the charging apparatus  10  can receive the carrier wave of specified frequency and demodulate that signal to detect the full-charge signal. Further, the device housing a battery can wirelessly transmit a full-charge signal to the charging apparatus to send the full-charge information. In that case, the device housing a battery contains a transmitter to send the full-charge signal, and the charging apparatus contains a receiver to receive the full-charge signal. The charging apparatus  10  shown in  FIG. 7  contains a full-charge detection circuit  17  to detect full-charge of the internal battery  52 . This full-charge detection circuit  17  detects a full-charge signal sent from the device housing a battery  50  to detect battery  52  full-charge. 
     Turning to  FIGS. 11-13 , an example of another device housing a battery and charging apparatus is shown. The device housing a battery  150  shown in the figures is an electric vehicle  150 A driven by an electric driving motor  177 . The electric vehicle  150 A, which is the device housing a battery  150 , carries a driving battery  170  on-board to power the driving motor  177 . The electric vehicle  150 A shown in the figures is an electric automobile (electric car, electric vehicle, EV). However, the electric vehicle can also be any vehicle, which is driven by an electric driving motor and carries an internal battery charged in a contactless manner by a charging apparatus, such as an electric wheel chair, an electric go-cart, or an electric fork-lift. In the embodiment described below, structural elements that are the same as in the previously described device housing a battery  50  and charging apparatus  10  are labeled with the same number and their detailed description is omitted. 
     The driving battery  170  powers the driving motor  177  that drives the electric vehicle. The driving battery  170  has many battery cells  170 A connected in series to increase output voltage and supply high power to the driving motor  177 . Nickel-hydride batteries or lithium ion rechargeable batteries are used as the battery cells  170 A. However, any battery that can be charged such as nickel-cadmium batteries can be used as rechargeable battery cells. 
     Further, the electric vehicle  150 A, which is the device housing a battery  150 , is provided with a contactless charging section  60  that charges the internal battery  152 , which is the driving battery  170 , in a contactless manner. The contactless charging section  60  is provided with an induction coil  51  that magnetically couples with a power supply coil  11  in the charging apparatus  110 , a rectifying circuit  53  that rectifies AC induced in the induction coil  51 , and a control circuit  54  that controls charging of the internal battery  152  in the device housing a battery  150  with output from the rectifying circuit  53 . The internal battery  152  is charged by power transmitted from the charging apparatus  110  power supply coil  11  to the induction coil  51  by magnetic induction. 
     As shown in  FIGS. 11-13 , the charging apparatus  110  is provided with the power supply coil  11  connected to an AC power source  112  to induce electromotive force (emf) in the induction coil  51 , a charging cart  120  that houses the power supply coil  11  and moves along the surface of the device housing a battery  150  holding the induction coil  51 , and a position detection controller  114  that detects the position of the induction coil  51  in the electric vehicle  150 A parked in a set location and moves the charging cart  120  power supply coil  11  to the position of the induction coil  51 . As shown in  FIGS. 11 and 12 , this charging apparatus  110  is disposed under the electric vehicle  150 A to charge the driving battery  170  installed in the electric vehicle  150 A. The charging apparatus  110  detects induction coil  51  location with the position detection controller  114 , moves the charging cart  120  housing the power supply coil  11 , and moves the power supply coil  11  to the position of the induction coil  51 . With the power supply coil  11  moved to a position that magnetically couples it with the induction coil  51 , the charging apparatus  110  transmits power from the power supply coil  11  to the induction coil  51  to charge the internal battery  152  in a contactless manner. This charging apparatus  110  can move the power supply coil  11  to the position of the induction coil  51  in an electric vehicle  150 A parked in a designated parking area  185  and can efficiently transmit power from the power supply coil  11  to the induction coil  51 . 
     The power supply coil  11  is a planar coil wound in a plane parallel to the upper surface of the charging cart  120  to radiate AC magnetic flux upward from the charging cart  120 . This power supply coil  11  emits AC magnetic flux perpendicular to, and above the upper surface of the charging cart  120 . The power supply coil  11  is supplied with AC power from the AC power source  112  and radiates AC magnetic flux above the upper surface of the charging cart  120 . 
     The charging cart  120  is controlled by the position detection controller  114  to move the power supply coil  11  to the position of the induction coil  51 . The power supply coil  11  is connected to the AC power source  112  and housed in a horizontal disposition under the upper surface of the charging cart  120 . The charging cart  120  moves along the under-surface of the electric vehicle  150 A to position the power supply coil  11  in close proximity to the induction coil  51  housed inside the under-surface of the electric vehicle  150 A. The charging cart  120  of the figures is provided with wheels  123  to move the charging cart  120 , motors  122  to drive the wheels  123 , and a moving mechanism  113  to control the motors  122 . 
     The position detection controller  114  detects the position of the induction coil  51  housed in an electric vehicle  150 A parked in the designated parking area  185 , and controls the charging cart  120  moving mechanism  113  to position the power supply coil  11  in close proximity to the induction coil  51 . As shown in  FIGS. 11 and 14 , the position detection controller  114  has a plurality of position detection coils  130  fixed to the inside of a position detection plate  121 . The position detection coils  130  are provided with a plurality of X-axis detection coils  130 A that detect induction coil  51  position on the X-axis, and a plurality of Y-axis detection coils  130 B that detect induction coil  51  position on the Y-axis. Each X-axis detection coil  130 A is a long narrow loop extending in the Y-axis direction, and the X-axis detection coils  130 A are fixed to the inside of the position detection plate  121  at specified intervals. Each Y-axis detection coil  130 B is a long narrow loop extending in the X-axis direction, and the Y-axis detection coils  1308  are also fixed to the inside of the position detection plate  121  at specified intervals. 
     The position detection controller  114  supplies position detection signals from a detection signal generating circuit  31  to the position detection coils  130 , receives echo signals output from the induction coil  51  excited by detection signal pulses, and detects induction coil  51  position from the received echo signals with a discrimination circuit  33 . The discrimination circuit  33  detects the position of the induction coil  51  on the X-axis from echo signals detected by the X-axis detection coils  130 A, and detects the position of the induction coil  51  on the Y-axis from echo signals detected by the Y-axis detection coils  130 B. 
     When the position detection controller  114  detects the position of the induction coil  51 , it moves the charging cart  12  to put the power supply coil  11  in proximity with the induction coil  51 . The position detection controller  114  controls the motors  122  via the moving mechanism  113  to drive the wheels  123  and move the charging cart  120  freely in any direction. The position of the freely moving charging cart  120  can be determined, for example, by issuing a pulse from the power supply coil  11  and receiving that pulse with the position detection coils  130 . Specifically, while detecting charging cart  120  position, the position detection controller  114  controls the rotation of the motors  122  that drive the wheels  123  of the charging cart  120  to move the power supply coil  11  to the induction coil  51 . However, the mechanism by which the position detection controller moves the charging cart is not limited to that described above. 
     The charging apparatus  110  can transmit power to charge the internal battery  152  after accurately controlling the power supply coil  11  to a position in close proximity to the induction coil  51 . A position detection controller  115  that can accurately detect induction coil  51  position has an AC power source  112  that is a self-excited oscillator circuit. This position detection controller  115  accurately detects power supply coil  11  location from the oscillating frequency of the self-excited oscillator circuit and controls the moving mechanism  113 . The position detection controller  115  controls the charging cart  120  moving mechanism  113  to move the power supply coil  11  while detecting the AC power source  112  oscillating frequency. As described previously, if the oscillating frequency of self-excited oscillator circuit is set to have a maximum (or minimum) where the power supply coil  11  and induction coil  51  are closest, the oscillating frequency will drop off (or increase) as the two coils become separated. Accordingly, the position detection controller  115  can move the power supply coil  11  to a position that is closest to the induction coil  51  by controlling the moving mechanism  113  to move the charging cart  120  and stop it at a position where the oscillating frequency is highest (or lowest). Further, the induction coil  51  can continuously send data indicating charging conditions to the charging apparatus  110  by connecting and disconnecting the parallel capacitor  56 , and by simply comparing charging conditions for improvement or deterioration, the power supply coil  11  can also be moved to an optimum position. 
     With the charging apparatus  110  moving mechanism  113  controlled by the position detection controller  114 ,  115  to put the power supply coil  11  in close proximity to the induction coil  51 , AC power is supplied to the power supply coil  11  from the AC power source  112 . Power supply coil  11  AC power is transmitted to the induction coil  51  and used to charge the internal battery  152 . When full-charge of the battery  152  is detected in the device housing a battery  150 , charging is stopped and a full-charge signal is sent to the charging apparatus  110 . 
     The charging apparatus  110  charges the battery  152  inside an electric vehicle  150 A, which is the device housing a battery  50 , in the following manner. 
     (1) The electric vehicle  150 A is stopped in a specified position in the designated parking area  185 . For example, the electric vehicle  150 A is stopped with its left and right wheels  187  in contact with left and right wheel chocks  186  disposed in the designated parking area  185 .
 
(2) The location of the induction coil  51  in the electric vehicle  150 A parked in the specified position is determined by the position detection controller  114 . The position detection controller  114  detects induction coil  51  position with the position detection coils  130  inside the position detection plate  121  disposed under the electric vehicle  150 A.
 
(3) The position detection controller  114 , which has detected the position of the induction coil  51 , controls the moving mechanism  113  to move the charging cart  120 , and position the power supply coil  11  housed in the charging cart  120  in close proximity with the induction coil  51  housed inside the under-surface of the electric vehicle  150 A.
 
(4) The power supply coil  11 , which has been moved close to the induction coil  51 , is magnetically coupled to the induction coil  51  and transmits AC power to the induction coil  51 .
 
(5) The contactless charging section  60  of the electric vehicle  150 A converts induction coil  51  AC power to DC and charges the internal battery  152 , which is the driving battery  170 , with that DC power.
 
     Efficiency of the power transmission from the power supply coil  11  to the induction coil  51  can be improved by narrowing the gap between the power supply coil  11  and the induction coil  51 . Therefore, when the charging cart  120  is moving below the under-surface of the electric vehicle  150 A, the gap between the power supply coil  11  and the induction coil  51  is a narrow gap that does not contact the upper surface of the charging cart  120  with the under-surface of the electric vehicle  150 A. Preferably, the gap between the upper surface of the charging cart  120  and the under-surface of the electric vehicle  150 A is less than or equal to 5 cm. However, when the wheels of the charging cart are being driven and the charging cart is moving under the electric vehicle, the upper surface of the charging cart and the under-surface of the electric vehicle can be non-contacting with a gap having some margin. Further, when power is transmitted from the power supply coil to the induction coil, a lift-mechanism can raise the power supply coil to put it in closest proximity with the induction coil for power transmission. When this charging cart completes internal battery charging, the power supply coil is lowered by the lift-mechanism prior to driving the wheels of the charging cart. 
     The electric vehicle  150 A described above, which is the device housing a battery  150 , is configured to allow charging from a charging adapter  180  in addition to contactless charging from the charging apparatus  110 . The device housing a battery  150  electric vehicle  150 A of the figures is provided with charging terminals  172  to connect the charging adapter  180  and charge the driving battery  170 , which is the internal battery  152 . A charging adapter  180  plug  183  provided at the end of a charging cable  182  is inserted in the electric vehicle  150 A charging terminals  172  to charge the driving battery  170  in the electric vehicle  150 A. 
     In the same manner as the previously described device housing a battery  50 , when this device housing a battery  150  electric vehicle  150 A is in position over the charging apparatus  110  and the charging adapter  180  is connected, the internal battery  152  is charged by either the charging apparatus  110  or the charging adapter  180 . Specifically, the device housing a battery  150  has a control circuit  54  provided with a charging apparatus detection section  61  that detects the device housing a battery  150  positioned over the charging apparatus  110 , an adapter detection section  62  that detects connection or charging by the charging adapter  180  that connects to the device housing a battery  150  to charge the internal battery  152 , and a charging selection section  63  that selects internal battery  152  charging by either the charging apparatus  110  or the charging adapter  180  according to signals from the charging apparatus detection section  61  and the adapter detection section  62 . When the device housing a battery  150  is positioned over the charging apparatus  110  and the charging adapter  180  is connected, the control circuit  54  preferably charges the internal battery  152  only with power supplied from the charging adapter  180  and not with power transmitted from the charging apparatus  110 . However, when the device housing a battery  150  is positioned over the charging apparatus  110  and the charging adapter  180  is connected, the internal battery  152  can also be charged only with power transmitted from the charging apparatus  110  and not with power supplied from the charging adapter  180 . 
     The charging apparatus  110  described above is provided with a charging cart  120  housing the power supply coil  11 , and a position detection plate  121  housing the position detection coils  130  that make up the position detection controller  114 . This charging apparatus  110  does not hold the position detection section and the power supply coil in a case or other housing such as in the previously described charging apparatus  10 , but rather is made up of a thin position detection plate  121  and a roving charging cart  120  housing the power supply coil  11 . Accordingly, the charging apparatus  110  has the characteristic that the position detection plate  121  is a simple, easy to move structure that can be easily set up in the electric vehicle  150 A designated parking area  185 , and the self-propelled charging cart  120  can be moved freely to put the power supply coil  11  in close proximity with the induction coil  51 . However, the charging apparatus can also have an external case that houses the position detection plate and power supply coil and is disposed in the vehicle parking area. Or, the charging apparatus can be buried in a fixed location below the surface of the parking area. In a charging apparatus buried in the parking area, an elevated region is established in a fixed position in the parking area and the position detection controller and power supply coil are housed in the elevated region. When the electric vehicle is parked in a specified position over the elevated region, the power supply coil is moved by the moving mechanism under the induction coil for contactless charging. 
     The following describes a device housing a battery that is a battery pack  210  provided with an output connector. Structural components that are the same as those described previously are assigned the same name and their description is abbreviated. The battery pack  210  is placed on a charging apparatus  10  (charging pad) having a transmitting coil  11  that transmits power by magnetic induction. As shown in  FIG. 15 , the battery pack  210  is provided with a receiving coil  205  that receives power transmitted from the transmitting coil  11 , an internal battery  201  that is charged by power induced in the receiving coil  205 , an output connector  208  that externally outputs internal battery  201  power as a power supply, a circuit board (not illustrated) that carries a charging circuit  250  that charges the internal battery  201  with power induced in the receiving coil  205 , and a casing that holds the circuit board, the receiving coil  205 , and the internal battery  201 . In addition, the battery pack  210  houses a sub-charging circuit  257  that charges the internal battery  201  by connection to an external power source  220 . 
     The circuit structure of the battery pack  210  shown in  FIGS. 15 and 16  is well-known technology, and the battery pack  210  is housed in a plastic casing (not illustrated). Although not illustrated, the receiving coil  205  is disposed inside the bottom surface of the casing to allow it to be put in close proximity with the transmitting coil  11 . 
     (The Receiving Coil as an Induction Coil) 
     The receiving coil  205  is a planar coil with wire wound spirally in a plane. The planar receiving coil  205  is wound as a single spiral layer or as a plurality of spiral layers, has an overall disk-shape, and has a circular outline. 
     (Output Connector and Input Connector) 
     As shown in  FIGS. 15 and 16 , the battery pack  210  is provided with an output connector  208  to supply power to a mobile electronic device  230 . The battery pack  210  of the figures has a universal serial bus (USB) connector  208 A as the output connector  208 . The USB connector  208 A, which is the output connector  208 , is a standard USB connector. A push-button switch  216  in an operating section (user interface) is pressed to output power. However, the output connector is not limited to a USB connector. Any type output connector besides a USB connector that can supply power to an externally connected mobile electronic device can be used. For example, a connector that connects to mobile phone (cell phone) power supply terminals can also be used as the output connector. In addition, the battery pack  210  of the figures is provided with an input connector  218  to charge the internal battery  201 . The output connector  208  and input connector  218  of the figures are mounted in fixed positions on the circuit board. 
     As shown in  FIG. 15 , the circuit board carries a charging circuit  250  that converts receiving coil  205  AC to DC to charge the internal battery  201 , a sub-charging circuit  257  (equivalent to the charging circuit  71  in the previous embodiment) that charges the internal battery  201  with power input from an external power source  220 , a DC/DC converter  258  to stabilize and output a constant voltage from the charged internal battery  201 , and a control circuit  240  (equivalent to the microcomputer  64  in the previous embodiment) to control internal battery  201  charging conditions and output connector  208  discharging conditions. 
     (Control Circuit) 
     The charging circuit  250  is provided with a rectifying circuit  251  that rectifies AC induced in the receiving coil  205  converting it to DC, a smoothing circuit  252  that is a smoothing capacitor  252 A that smoothes ripple current in the DC rectified by the rectifying circuit  251 , and a charging control circuit  253  that charges the internal battery  201  with DC smoothed by the smoothing circuit  252 . The charging circuit  250  charges the internal battery  201  with appropriate voltage and current. The charging circuit  250  in a battery pack  210  with a lithium ion internal battery  201  has a charging control circuit  253  that is a constant voltage-constant current circuit for charging the internal battery  201  with a constant voltage and a constant current. The charging control circuit in a battery pack with an internal battery such as a nickel hydride battery or alkaline battery is a constant current circuit. 
     (Sub-Charging Circuit [Equivalent to the Charging Circuit  71  in the Previous Embodiment]) 
     The sub-charging circuit  257  charges the internal battery  201  with power input from the external power source  220 . In a battery pack with a lithium ion internal battery  201 , the sub-charging circuit  257  charges the internal battery  201  via constant voltage-constant current charging. In a battery pack with an internal battery that is a nickel hydride or nickel cadmium battery, the sub-charging circuit charges the internal battery with constant current charging. Further, when the sub-charging circuit  257  detects full-charge of the internal battery  201 , it halts charging. The battery pack  210  of the figures is provided with an input connector  218  to input power from the external power source  220  to the sub-charging circuit  257 . The input connector  218  shown in the figures is a mini- or micro-USB connector  218 A. However, an input connector that can input power from an external power source other than a mini- or micro-USB connector can also be used. For example, a connector such as the power receptacle for an adapter jack connected to an AC adapter can also be used. 
     When the external power source  220  (equivalent to the charging adapter  80  in the previous embodiment) is connected to the input connector  218 , the sub-charging circuit  257  can detect that connection from input current or voltage. This is because power is supplied from the external power source  220  to the battery pack  210  when the external power source  220  is connected. When power is input from the external power source  220 , the sub-charging circuit  257  charges the internal battery  201  with power from the external power source  220 . However, instead of providing a special-purpose input connector dedicated to battery charging, the output connector can serve both to input external power and to output power to the outside. For example, this type of battery pack has the output connector connected to the sub-charging circuit and the DC/DC converter through switches, and the output connector is connected to either the sub-charging circuit or the DC/DC converter by controlling the switches. 
     When an external power source  220  is connected to the input connector  218  and the battery pack is placed on the charging apparatus  10 , the battery pack is configured to charge the internal battery  201  by either the external power source  220  or the charging apparatus  10 . The control circuit  240  in  FIG. 15  is provided with a charging pad detection section  241  (equivalent to the charging apparatus detection section  61  in the previous embodiment) that detects placement of the battery pack  210  on the charging apparatus  10 , an external power source detection section  242  (equivalent to the adapter detection section  62  in the previous embodiment) that detects connection or charging by an external power source  220 , and a charging selection section  243  (equivalent to the charging selection section  63  in the previous embodiment) that selects internal battery  201  charging by either the charging apparatus  10  or the external power source  220  according to signals from the charging pad detection section  241  and the external power source detection section  242 . 
     When the battery pack  210  is placed on the charging apparatus  10  and the external power source  220  is also connected, the control circuit  240  through the charging selection section  243  controls internal battery  201  charging with either the charging apparatus  10  or the external power source  220 . In the case where the battery pack  210  is placed on the charging apparatus  10  and the external power source  220  is connected, namely, when the internal battery  201  can be charged by either the charging apparatus  10  or the external power source  220 , the control circuit  240  preferably charges the internal battery  201  only with power supplied from the external power source  220  and not with power transmitted from the charging apparatus  10 . However, when the battery pack  210  is placed on the charging apparatus  10  and the external power source  220  is connected, the internal battery  201  can also be charged only with power transmitted from the charging apparatus  10  and not with power supplied from the external power source  220 . In that case, the switch  244  is controlled OFF to cut-off power from the sub-charging circuit  257 . 
     The control circuit  240  charging pad detection section  241  detects placement of the battery pack  210  on the charging apparatus  10 , or charging by the charging apparatus  10 . As its power supply voltage, the control circuit  240  operates by power output from the rectifying circuit  251 , which converts receiving coil  205  output to DC, and does not operate by power supplied from the internal battery  201 . Specifically, the control circuit  240  does not consume operating power from the internal battery  201 , but rather operates on power supplied by magnetic induction from the charging apparatus  10 . Accordingly, when the battery pack  210  is placed on the charging apparatus  10 , the control circuit  240  is activated and becomes operational. The charging pad detection section  241  detects placement of the battery pack  210  on the charging apparatus  10  by detecting control circuit  240  activation. This charging pad detection section  241  can detect placement on the charging apparatus  10  with a simple circuit structure. However, the charging pad detection section can also receive a signal from charging pad to detect placement on the charging pad. 
     The external power source detection section  242  detects external power source  220  connection or internal battery  201  charging by the external power source  220 . The external power source detection section  242  detects external power source  220  connection or charging while contactless charging is in a halted state. Contactless charging is halted by switching OFF the switch  245  connected between the charging circuit  250  and the internal battery  201 . The control circuit  240  holds the switch  245  OFF to halt contactless charging for the time period when external power source  220  connection or charging is being detected. The following describes the details of detecting external power source  220  connection with the external power source detection section  242 . The external power source detection section  242  (equivalent to the adapter detection section  62  in the previous embodiment) is provided with an adapter detection circuit  242 C. The adapter detection circuit  242 C is activated by voltage applied by connecting the external power source  220 , which is the charging adapter, and issues a connection signal to the external power source detection section  242 . The adapter detection circuit  242 C has a switching device SW connected between the external power source detection section  242  input port I and ground, and the switching device SW is activated by voltage applied by connecting the external power source  220 . Voltage application due to external power source  220  connection puts the switching device SW in a conducting state, and a LOW voltage level is applied as a connection signal at the input port I of the external power source detection section  242 . Specifically, as shown in  FIG. 15 , an npn bipolar transistor Tr has its base connected through a current-limiting resistor R to a positive-side line from the external power source  220 , its emitter grounded, and its collector connected to the input port I of the external power source detection section  242 . In this configuration, when the external power source  220  is connected, a HIGH voltage level is applied to the base of the transistor Tr, the transistor Tr conducts between its collector and emitter, and the potential at the input port I changes from a HIGH level to a LOW level. This LOW voltage level at the input port is transmitted to the external power source detection section  242  as a connection signal, and the external power source detection section  242  detects that signal to detect external power source  220  connection. 
     When the control circuit  240  charging pad detection section  241  detects placement on the charging apparatus  10  and the external power source detection section  242  detects external power source  220  connection or charging, the charging selection section  243  sends a halt-charging-signal to the charging apparatus  10  to halt charging by the charging apparatus  10 , and charges the internal battery  201  with the external power source  220 . When the battery pack  210  is not placed on the charging apparatus  10  and the external power source  220  is connected, the control circuit  240  charges the internal battery  201  with the external power source  220 . When the battery pack  210  is not placed on the charging apparatus  10 , there is no need to detect external power source  220  connection or charging with the external power source detection section  242 . This is because the internal battery  201  can be charged under ideal conditions by the external power source  220 . Since the external power source detection section  242  only detects external power source  220  connection or charging when the battery pack  210  is placed on the charging apparatus  10 , it is not necessary for the external power source detection section  242  to detect external power source  220  connection or charging when the battery pack  210  is not placed on the charging apparatus  10 . Accordingly, a battery pack  210  that operates the control circuit  240  with power transmitted from the charging apparatus  10  only activates the control circuit  240  to detect external power source  220  connection and charging. However, the control circuit  240  charging pad detection section  241  and external power source detection section  242  can also be continuously operated to detect placement on the charging apparatus  10  and external power source  220  connection and charging. When this battery pack  210  is placed on the charging apparatus  10  and the external power source  220  is not connected, the control, circuit  240  charges the internal battery  201  from the charging apparatus  10 , and when the battery pack  210  is not placed on the charging apparatus  10  and the external power source  220  is connected, the control circuit  240  charges the internal battery  201  from the external power source  220 . 
     The control circuit  240  in  FIG. 15  holds a signal switch  255 , which is connected in series with a parallel capacitor  254  connected in parallel with the receiving coil  205 , ON to send a halt-charging-signal to the charging apparatus  10 . The charging apparatus  10  detects connection of the parallel capacitor  254  to the receiving coil  205  and stops delivering AC to the transmitting coil  11 . The control circuit  240  can also switch the signal switch  255  ON and OFF in a prescribed manner (instead of holding it in the ON state) to convey connection of the external power source  220  to the charging apparatus  10 . In that case, the charging apparatus  10  detects ON and OFF switching of the signal switch  255  to detect external power source  220  connection and stops delivering AC to the transmitting coil  11 . A system that stops the charging apparatus  10  from charging the internal battery  201  by halting the input of AC to the transmitting coil  11  not only reduces unnecessary power consumption, but also prevents detrimental heating of the battery pack  210  by power output from the transmitting coil  11 . However, when external power source  220  connection or charging is detected, AC output to the transmitting coil  11  does not necessarily have to be stopped, and the control circuit  240  in the battery pack  210  can also turn OFF the switch  245  to cut-off charging current to the internal battery  201  and stop charging by the charging apparatus  10 . 
     The rectifying circuit  251  rectifies AC power induced in the receiving coil  205  and outputs the rectified power to the control circuit  240 . The battery pack  210  of the figures has a series capacitor  256  connected between the receiving coil  205  and the rectifying circuit  251 , and AC power induced in the receiving coil  205  is input to the rectifying circuit  251  through that series capacitor  256 . The series capacitor  256  forms a series resonant circuit with the receiving coil  205  to efficiently input AC power induced in the receiving coil  205  to the rectifying circuit  251 . Accordingly, the capacitance of the series capacitor  256  is selected to combine with the receiving coil  205  inductance for an overall impedance having a minimum near the frequency of the induced AC power. 
     (DC/DC Converter) 
     The DC/DC converter  258  stabilizes and outputs a constant voltage from the charged internal battery  201 . In the circuit diagram of  FIG. 15 , a discharge switch  246  connected between the internal battery  201  and the DC/DC converter  258  is mounted on the circuit board (not illustrated). The discharge switch  246  is controlled ON and OFF by the control circuit  240 . The control circuit  240  switches the discharge switch  246  ON and OFF according to signals from the push-button switch  216 , which is the operating section (user interface). When an ON signal is input from the push-button switch  216  for a given length of time, the control circuit  240  switches the discharge switch  216  ON to output power from the internal battery  201  to the DC/DC converter  258 . At that time, the DC/DC converter  258  is activated and supplies stabilized power to the output connector  208  connected to its output-side. If a mobile electronic device connected to the output connector  208  is disconnected from the output connector  208 , the control circuit  240  detects disconnection by the output current. This is because output current drops to 0 A when the mobile electronic device is disconnected. 
     Further, as shown in  FIG. 15 , a protection circuit  247  that controls internal battery  201  charging and discharging is mounted on the circuit board (not illustrated). The protection circuit  247  detects battery temperature and voltage and controls battery charging and discharging. Battery temperature is detected by a temperature sensor  219  attached in a thermally coupled manner to the surface of the internal battery  201 . The temperature sensor  219  is connected to the protection circuit  247 . The protection circuit  247  is provided with memory  248  that stores data for limiting battery charging and discharging current according to temperature. Memory  248  stores allowable current corresponding to battery temperature. Allowable current is the maximum current allowed to flow at a given temperature, and an operating current lower than that current is used. The protection circuit  247  protects the battery by controlling battery charging and discharging current below the allowable current corresponding to battery temperature. In addition, the protection circuit  247  can store the maximum and minimum temperatures for battery charging and discharging, and can control charging and discharging to allow operation between the maximum and minimum temperatures. The maximum and minimum temperatures are set to the most appropriate values for the type of battery. For example, for a lithium ion battery, the maximum temperature can be approximately 60° C. to 70° C. and the minimum temperature can be approximately −10° C. to 0° C. 
     Further, the protection circuit  247  can control charging and discharging by detecting the voltage of the internal battery  201 . The protection circuit  247  stops charging when battery voltage rises to a maximum voltage, and stops discharging when battery voltage drops to a minimum voltage. 
     If the protection circuit  247  shown in  FIG. 15  detects abnormal battery temperature or voltage, it controls the control circuit  240  to stop charging the internal battery  201  and controls the discharge switch  246  OFF to stop discharging the internal battery  201 . 
     The battery pack shown in  FIG. 15  also houses a remaining capacity detection circuit  249  to detect the remaining capacity of the internal battery  201 . The remaining capacity detection circuit  249  computes remaining capacity from internal battery  201  voltage and current, and indicates the remaining capacity by the illumination color or the number of devices illuminated in a display of light emitting diodes (LEDs)  217 . When an ON signal is received from the push-button switch  216 , the remaining capacity detection circuit  249  illuminates the LEDs  217  for a given time period to indicate the remaining capacity. 
     The push-button switch  216  can also switch the DC/DC converter  258  to the operating state. In a battery pack  210  where both remaining capacity is indicated and the DC/DC converter  258  is switched to the operating state by push-button switch  216  ON and OFF signals, remaining capacity can be indicated by pressing the push-button switch  216  for a short period and the DC/DC converter  258  can be switched to the operating state by pressing the push-button switch  216  for a longer period. If the signal input from the push-button switch  216  is judged to be longer than a set period, the DC/DC converter  258  is switched to the operational state. Since the DC/DC converter  258  remains in an inactivated state if the push-button switch  216  is not held pressed for a long period, unnecessary battery power consumption can be prevented in a battery pack  210  with no mobile electronic device  230  connected to the output connector  208 . This is because the DC/DC converter  258  consumes power in the operational state even when no mobile electronic device  230  is connected as a load. 
     Further, the control circuit detects full-charge of the internal battery  201  and stops internal battery  201  charging. When full-charge of the internal battery  201  is detected, a signal indicating full-charge is sent to the charging apparatus  10 . The charging apparatus  10  detects the full-charge signal and halts charging. 
     It should be apparent to those with an ordinary skill in the art that while various preferred embodiments of the invention have been shown and described, it is contemplated that the invention is not limited to the particular embodiments disclosed, which are deemed to be merely illustrative of the inventive concepts and should not be interpreted as limiting the scope of the invention, and which are suitable for all modifications and changes falling within the spirit and scope of the invention as defined in the appended claims. The present application is based on Application No. 2010-183218 filed in Japan on Aug. 18, 2010 and Application No. 2011-132742 filed in Japan on Jun. 14, 2011, the content of which is incorporated herein by references.