Portable device

Abstract

To improve convenience for a vehicle occupant who carries a portable device.SOLUTION: A smart key 3 is carried by a vehicle occupant and includes a LF receiving antenna 22, a control unit 21, a primary battery 41, a storage battery 42, and a changeover switch 43. The primary battery 41 is configured to supply power to the control unit 21. The storage battery 42 is configured to supply power to the control unit 21. The changeover switch 43 is configured to switch the power supply to the control unit 21 so that when the value of a primary battery voltage Vbat is greater than the value of a storage battery voltage Vc, power is supplied from the primary battery 41 to the control unit 21, and when the value of the primary battery voltage Vbat is smaller than the value of the storage battery voltage Vc, power is supplied from the storage battery 42 to the control unit 21.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present disclosure relates to a portable device carried by a vehicle occupant. [Background technology]

[0002] Patent Document 1 describes a portable device that includes a vibration power generation unit that generates power when the portable device is vibrated, a power receiving unit that receives power wirelessly, and a power storage unit that stores the power generated by the vibration power generation unit and the power received by the power receiving unit. This makes it possible to suppress a voltage drop in a battery mounted on the portable device that wirelessly communicates with an in-vehicle device mounted on a vehicle. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-165043 A Summary of the Invention [Problem to be solved by the invention]

[0004] In a portable device equipped with a primary battery, a drop in the voltage of the primary battery can cause the vehicle occupant to be unable to unlock or lock the vehicle doors, resulting in a problem of reduced convenience for the occupant carrying the portable device.

[0005] The present disclosure aims to improve convenience for vehicle occupants who carry a portable device. [Means for solving the problem]

[0006] One aspect of the present disclosure is a portable device (3) carried by a vehicle occupant, comprising a receiving antenna (22), a control unit (21), a primary battery (41), a secondary battery (42), and a battery switching unit (43).

[0007] The receiving antenna is configured to receive a transmission signal transmitted from an on-board device (2) mounted on the vehicle. The control unit is configured to control the portable device. The primary battery is configured to supply power to the control unit. The secondary battery is configured to supply power to the control unit.

[0008] The battery switching unit is configured to compare a primary battery voltage value, which is the voltage of the primary battery, with a secondary battery voltage value, which is the voltage of the secondary battery, and switch the power supply to the control unit so that if the primary battery voltage value is greater than the secondary battery voltage value, power is supplied from the primary battery to the control unit, and if the primary battery voltage value is smaller than the secondary battery voltage value, power is supplied from the secondary battery to the control unit.

[0009] The portable device of the present disclosure configured in this manner can supply power to the control unit using the secondary battery instead of the primary battery when the voltage of the primary battery becomes low. Therefore, the portable device of the present disclosure can prevent the occurrence of a situation in which the vehicle occupant is unable to unlock or lock the vehicle doors due to a drop in the voltage of the primary battery, thereby improving convenience for the vehicle occupant who carries the portable device. [Brief description of the drawings]

[0010] [Figure 1] 1 is a block diagram showing a configuration of a vehicle communication system; [Diagram 2] FIG. 2 is a circuit diagram showing the configuration of a smart key. [Diagram 3] FIG. 2 is a block diagram showing the internal structure of a smart key. [Figure 4] 13 is a flowchart showing a reception stop process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. As shown in FIG. 1, a vehicle communication system 1 of this embodiment includes an on-board device 2 mounted on a vehicle, and a smart key 3 carried by a legitimate user of the vehicle.

[0012] The vehicle-mounted device 2 includes a control unit 11, an LF communication unit 12, and an RF communication unit 13. LF is an abbreviation for Low Frequency, and RF is an abbreviation for Radio Frequency. The control unit 11 is an electronic control device mainly composed of a microcomputer having a CPU 11a, a ROM 11b, a RAM 11c, etc. Various functions of the microcomputer are realized by the CPU 11a executing a program stored in a non-transient real recording medium. In this example, the ROM 11b corresponds to the non-transient real recording medium storing the program. Furthermore, the execution of this program executes a method corresponding to the program. Note that some or all of the functions executed by the CPU 11a may be configured in hardware form using one or more ICs, etc. Also, the number of microcomputers constituting the control unit 11 may be one or more.

[0013] The LF communication unit 12 has a function of transmitting a radio signal in the LF band to the outside of the vehicle. The RF communication unit 13 has a function of receiving a radio signal in the RF band transmitted from the outside of the vehicle. For example, a frequency band from 20 kHz to 200 kHz can be used as the LF band, and for example, a frequency band from 300 MHz to 400 MHz can be used as the RF band.

[0014] The smart key 3 includes a control unit 21, an LF receiving antenna 22, an RF transmitting antenna 23, a receiving circuit 24, and a transmitting circuit 25. The control unit 21 is an electronic control device mainly composed of a microcomputer including a CPU 21a, a ROM 21b, a RAM 21c, etc. Various functions of the microcomputer are realized by the CPU 21a executing a program stored in a non-transient real recording medium. In this example, the ROM 21b corresponds to the non-transient real recording medium storing the program. Furthermore, the execution of this program executes a method corresponding to the program. Note that some or all of the functions executed by the CPU 21a may be configured in hardware form using one or more ICs, etc. Also, the number of microcomputers constituting the control unit 21 may be one or more.

[0015] The LF receiving antenna 22 is an antenna for receiving radio signals in the LF band, and the RF transmitting antenna 23 is an antenna for transmitting radio signals in the RF band. The receiving circuit 24 demodulates the received signal input from the LF receiving antenna 22 .

[0016] The transmission circuit 25 modulates the transmission data input from the control unit 21 to generate a signal to be transmitted via the RF transmission antenna 23 . The vehicle-mounted device 2 has a function (so-called smart entry function) of executing control such as unlocking the vehicle doors when the smart key 3 held by the authorized vehicle user enters an unlocking area around the vehicle.

[0017] Specifically, the control unit 11 of the in-vehicle device 2 periodically transmits a start-up command as a wireless signal in the LF band to the LF communication unit 12. When the control unit 11 of the in-vehicle device 2 receives a reply command transmitted from the smart key 3 at the RF communication unit 13, it extracts the identification information contained in the reply command and executes a matching process. If the extracted identification information matches the identification information for smart entry, the in-vehicle device 2 unlocks the vehicle doors.

[0018] 2, the LF receiving antenna 22 includes a coil antenna 22a. That is, the LF receiving antenna 22 receives a wireless signal in the LF band by the coil antenna 22a. The coil antenna 22a is configured to generate power by receiving radio waves for power supply transmitted from the wireless charger 5.

[0019] The receiving circuit 24 includes a demodulation circuit 31, a rectifier circuit 32, switching elements 33 and 34, and a comparator 35. The demodulation circuit 31 is connected to the LF receiving antenna 22. The demodulation circuit 31 demodulates the received signal input from the LF receiving antenna 22, and outputs the demodulated signal generated by the demodulation to the control unit 21.

[0020] The rectifier circuit 32 converts the AC current input from the LF receiving antenna 22 into a DC current by full-wave rectification. The rectifier circuit 32 is a bridge circuit including four rectifying diodes 32a, 32b, 32c, and 32d.

[0021] The anode of the diode 32a is grounded, and the cathode of the diode 32a is connected to the anode of the diode 32b. The anode of the diode 32c is grounded, and the cathode of the diode 32c is connected to the anode of the diode 32d. The cathode of the diode 32b is connected to the cathode of the diode 32d.

[0022] The switching elements 33 and 34 are disposed on a current path between the LF receiving antenna 22 and the rectifier circuit 32. In this embodiment, the switching elements 33 and 34 are P-channel MOSFETs. Note that, although the switching elements 33 and 34 are MOSFETs in this embodiment, they may be other semiconductor elements such as bipolar transistors.

[0023] The source of the switching element 33 is connected to the first end of the coil antenna 22a. The drain of the switching element 33 is connected to the connection point between the diode 32a and the diode 32b.

[0024] The source of the switching element 34 is connected to the second end of the coil antenna 22a. The drain of the switching element 34 is connected to the connection point between the diode 32c and the diode 32d.

[0025] The comparator 35 has a first input terminal, a second input terminal, and an output terminal. When the voltage value applied to the first input terminal is greater than the voltage value applied to the second input terminal, the comparator 35 sets the voltage level of the output terminal to a high level. On the other hand, when the voltage value applied to the first input terminal is equal to or less than the voltage value applied to the second input terminal, the comparator 35 sets the voltage level of the output terminal to a low level. The output terminal of the comparator 35 is connected to the gates of the switching elements 33 and 34.

[0026] The smart key 3 further includes a primary battery 41, a storage battery 42, a change-over switch 43, a diode 44, a bandgap circuit 45, and a voltage divider circuit 46. The primary battery 41 is, for example, a coin battery. The positive electrode of the primary battery 41 is connected to the control unit 21, the receiving circuit 24, and the transmitting circuit 25 via the changeover switch 43. The negative electrode of the primary battery 41 is grounded.

[0027] The storage battery 42 is a chargeable and dischargeable secondary battery, and is a capacitor in this embodiment. The positive electrode of the storage battery 42 is connected to the connection point between the diode 32b and the diode 32d. The negative electrode of the storage battery 42 is grounded. The positive electrode of the storage battery 42 is connected to the control unit 21, the receiving circuit 24, and the transmitting circuit 25 via the changeover switch 43 and the diode 44.

[0028] The changeover switch 43 has a first connection terminal, a second connection terminal, and a third connection terminal (not shown). The first connection terminal is connected to the control unit 21, the receiving circuit 24, and the transmitting circuit 25. The second connection terminal is connected to the positive electrode of the primary battery 41. The third connection terminal is connected to the positive electrode of the storage battery 42 via a diode 44.

[0029] The changeover switch 43 is configured to switch between a first conductive state in which the first connection terminal and the second connection terminal are connected, and a second conductive state in which the first connection terminal and the third connection terminal are connected. The changeover switch 43 is configured to be in the first conductive state when the voltage of the second connection terminal is equal to or higher than the voltage of the third connection terminal. The changeover switch 43 is configured to be in the second conductive state when the voltage of the second connection terminal is lower than the voltage of the third connection terminal.

[0030] The diode 44 has an anode connected to the positive electrode of the storage battery 42 and a cathode connected to the third connection terminal of the changeover switch 43. The bandgap circuit 45 includes a bandgap input terminal and a bandgap output terminal, not shown. A power supply voltage Vop is applied to the bandgap input terminal. The bandgap circuit 45 generates a bandgap voltage Vgb from the power supply voltage Vop and outputs the bandgap voltage Vgb from the bandgap output terminal. The bandgap circuit 45 is a circuit that generates a stable reference voltage (i.e., bandgap voltage Vgb) that is not dependent on fluctuations in the power supply voltage Vop. The bandgap output terminal is connected to the second input terminal of the comparator 35. The power supply voltage Vop is a voltage applied to a first connection terminal of the changeover switch 43 (i.e., a voltage supplied to the control unit 21, the receiving circuit 24, and the transmitting circuit 25).

[0031] The voltage divider circuit 46 outputs a divided voltage aVop of the power supply voltage Vop to the first input terminal of the comparator 35 . As shown in FIG. 3, the smart key 3 further includes a housing 51, a charging magnet 52, a board 53, switch knobs 54, 55, and 56, and switches 57, 58, and 59.

[0032] The housing 51 accommodates therein the control unit 21, the coil antenna 22a, the RF transmitting antenna 23, the receiving circuit 24, and the transmitting circuit 25. The charging magnet 52 is housed inside a magnet housing portion 51a provided within the housing 51. The magnet housing portion 51a houses the charging magnet 52 such that the charging magnet 52 moves along a first movement direction D1 preset within the magnet housing portion 51a and a second movement direction D2 set to be opposite to the first movement direction D1.

[0033] The coil antenna 22a is disposed near the magnet housing portion 51a. Specifically, the coil antenna 22a is disposed at a position where the coil antenna 22a can generate electricity by electromagnetic induction between the coil antenna 22a and the charging magnet 52.

[0034] The substrate 53 is formed in a plate shape and installed within the housing 51. The substrate 53 mounts the above-described control unit 21, coil antenna 22a, RF transmission antenna 23, reception circuit 24, transmission circuit 25, and switches 57, 58, 59 on the front or back surface of the substrate 53.

[0035] The switch knobs 54, 55, 56 are installed on the surface of the housing 51 and are operated by a person holding the smart key 3. The switch knob 54 is operated, for example, when locking the vehicle door. The switch knob 55 is operated, for example, when unlocking the vehicle door. The switch knob 56 is operated, for example, when opening or closing the vehicle's back door.

[0036] The switches 57, 58, 59 each switch to an on state or an off state in conjunction with the switch knobs 54, 55, 56. That is, the switches 57, 58, 59 each become on when the switch knobs 54, 55, 56 are being operated and become off when the switch knobs 54, 55, 56 are not being operated.

[0037] In the smart key 3 configured in this manner, when the voltage Vbat of the primary battery 41 (hereinafter referred to as the primary battery voltage Vbat) is sufficiently high (i.e., when the divided voltage aVop is higher than the bandgap voltage Vgb), the coil antenna 22a and the rectifier circuit 32 are not electrically connected, so that the rectifier circuit 32 does not perform rectification operation and the coil antenna 22a functions only for communication.

[0038] When the primary battery voltage Vbat drops (i.e., when the divided voltage aVop becomes equal to or lower than the bandgap voltage Vgb), the coil antenna 22a and the rectifier circuit 32 are electrically connected, enabling the rectifier circuit 32 to perform rectification processing, and the coil antenna 22a functions for wireless charging and vibration charging.

[0039] Then, the alternating current flowing through the coil antenna 22a as a result of receiving power supply radio waves transmitted from the wireless charger 5, or the alternating current flowing through the coil antenna 22a as a result of electromagnetic induction generated between the coil antenna 22a and the charging magnet 52 due to vibration of the charging magnet 52, is converted into a direct current by the rectifier circuit 32, thereby charging the storage battery 42.

[0040] When the voltage Vc of the storage battery 42 (hereinafter, storage battery voltage Vc) becomes higher than the primary battery voltage Vbat, the changeover switch 43 switches so that the storage battery voltage Vc is used as the power supply voltage Vop.

[0041] When the storage battery 42 is sufficiently charged and the divided voltage aVop becomes higher than the bandgap voltage Vgb, the rectifier circuit 32 stops rectifying, and the coil antenna 22a functions only for communication. However, when the power supply voltage Vop drops again, the rectifier circuit 32 starts rectifying, and the coil antenna 22a functions for wireless charging and vibration charging.

[0042] Next, there will be described the procedure of the reception stop processing executed by the control unit 21 of the smart key 3. The reception stop processing is processing that is repeatedly executed while the control unit 21 is in operation. 4, when the reception stop process is executed, the CPU 21a of the control unit 21 determines in S10 whether or not a stop command has been received from the wireless charger 5. Note that, while transmitting radio waves for power supply, the wireless charger 5 is configured to transmit a wireless signal instructing the reception circuit 24 to stop as a stop command every time a preset transmission period elapses.

[0043] Here, if a stop command has not been received from the wireless charger 5, the CPU 21a proceeds to S40. On the other hand, if a stop command has been received from the wireless charger 5, the CPU 21a stops the receiving circuit 24 in S20. Specifically, the CPU 21a stops the receiving circuit 24 by, for example, instructing the demodulation circuit 31 to stop the demodulation process or by stopping the power supply to the receiving circuit 24.

[0044] In S30, the CPU 21a starts a stop timer provided in the RAM 21c, and proceeds to S40. The stop timer is a timer that increments, for example, every 1 ms, and when started, its value is incremented from 0 (that is, by adding 1).

[0045] When the process proceeds to S40, the CPU 21a judges whether the stop time has elapsed. Specifically, the CPU 21a judges whether the value of the stop timer is equal to or greater than the value corresponding to the stop time. If the stop time has not elapsed, that is, if the value of the stop timer is less than the value corresponding to the stop time, the CPU 21a ends the reception stop process.

[0046] On the other hand, when the stop time has elapsed, that is, when the value of the stop timer is equal to or greater than the value corresponding to the stop time, the CPU 21a starts up the receiving circuit 24 in S50. Specifically, the CPU 21a starts up the receiving circuit 24 by, for example, instructing the demodulation circuit 31 to start demodulation processing or by resuming power supply to the receiving circuit 24.

[0047] In S60, the CPU 21a stops incrementing the stop timer, and then resets the stop timer (that is, sets the value of the stop timer to 0), and ends the reception stop process. The smart key 3 configured in this manner is carried by a vehicle occupant, and includes an LF receiving antenna 22, a control unit 21, a primary battery 41, a storage battery 42, and a changeover switch 43.

[0048] The LF receiving antenna 22 is configured to receive a radio signal in the LF band transmitted from an on-board device 2 mounted on a vehicle. The control unit 21 is configured to control the smart key 3. The primary battery 41 is configured to supply power to the control unit 21. The storage battery 42 is configured to supply power to the control unit 21.

[0049] The changeover switch 43 is configured to compare the value of the primary battery voltage Vbat with the value of the storage battery voltage Vc, and switch the power supply to the control unit 21 so that if the value of the primary battery voltage Vbat is greater than the value of the storage battery voltage Vc, power is supplied from the primary battery 41 to the control unit 21, and if the value of the primary battery voltage Vbat is smaller than the value of the storage battery voltage Vc, power is supplied from the storage battery 42 to the control unit 21.

[0050] When the primary battery voltage Vbat becomes low, the smart key 3 can supply power to the control unit 21 using the storage battery 42 instead of the primary battery 41. Therefore, the smart key 3 can prevent a situation in which a vehicle occupant is unable to unlock or lock the vehicle doors due to a drop in voltage of the primary battery 41, thereby improving convenience for the vehicle occupant who carries the smart key 3.

[0051] The LF receiving antenna 22 is configured to receive LF band wireless signals using a coil antenna 22a configured to generate power by receiving power supply radio waves transmitted from the wireless charger 5. This allows the smart key 3 to charge the storage battery 42. Therefore, the smart key 3 can prevent the occurrence of a situation in which the vehicle occupant is unable to unlock or lock the vehicle doors due to a drop in voltage not only of the primary battery 41 but also of the storage battery 42, thereby further improving convenience for the vehicle occupant who carries the smart key 3.

[0052] The smart key 3 also includes a charging magnet 52 that is installed so as to vibrate inside the smart key 3 when the smart key 3 is moved. The coil antenna 22a is arranged in a position where the coil antenna 22a can generate power by electromagnetic induction between the coil antenna 22a and the charging magnet 52. This allows the smart key 3 to charge the storage battery 42 not only by the power supply radio waves from the wireless charger 5 but also by the vibration of the charging magnet 52. Therefore, the smart key 3 can prevent the occurrence of a situation in which the vehicle occupant cannot unlock or lock the vehicle door due to a voltage drop not only in the primary battery 41 but also in the storage battery 42, and can further improve the convenience of the vehicle occupant carrying the smart key 3. Furthermore, the smart key 3 can perform wireless charging and vibration charging using one coil antenna 22a, so that it is possible to prevent the size of the smart key 3 from increasing due to the provision of both the wireless charging function and the vibration charging function.

[0053] Furthermore, when the control unit 21 receives a stop command transmitted from the wireless charger 5 via the LF receiving antenna 22, it is configured to stop the receiving circuit 24, thereby stopping the receiving function of receiving LF band wireless signals via the LF receiving antenna 22. This enables the smart key 3 to prevent the vehicle from being stolen while it is being charged using the wireless charger 5.

[0054] The smart key 3 also includes a rectifier circuit 32, switching elements 33 and 34, a comparator 35, a bandgap circuit 45, and a voltage divider circuit 46. The rectifier circuit 32 is disposed on the current path between the coil antenna 22a and the storage battery 42, and is configured to perform a rectification process in which the AC current generated by the coil antenna 22a is rectified to convert it into a DC current and supplied to the storage battery 42.

[0055] The switching elements 33, 34, the comparator 35, the bandgap circuit 45 and the voltage divider circuit 46 are configured to switch the state of the rectifier circuit 32 between a rectification execution state in which the rectifier circuit 32 can perform a rectification process and a rectification stop state in which the rectifier circuit 32 cannot perform a rectification process.

[0056] The switching elements 33, 34, the comparator 35, the band gap circuit 45, and the voltage dividing circuit 46 are configured to switch the rectifier circuit 32 to a rectification execution state when a preset charging condition indicating that the primary battery voltage Vbat is low is satisfied, and to switch the rectifier circuit 32 to a rectification stop state when the charging condition is not satisfied. The charging condition in this embodiment is that the divided voltage aVop is equal to or lower than the band gap voltage Vgb. This allows the smart key 3 to cause the coil antenna 22a to function for communication when the charging condition is not satisfied, and to cause the coil antenna 22a to function for charging when the charging condition is satisfied.

[0057] In the embodiment described above, the smart key 3 corresponds to a portable device, the LF band wireless signal corresponds to a transmission signal, the LF receiving antenna 22 corresponds to a receiving antenna, and the storage battery 42 corresponds to a secondary battery.

[0058] Moreover, the primary battery voltage Vbat corresponds to the primary battery voltage, the storage battery voltage Vc corresponds to the secondary battery voltage, and the changeover switch 43 corresponds to the battery switching unit. Further, the coil antenna 22a corresponds to a charging coil, the stop command corresponds to a reception stop command, and the switching elements 33, 34, the comparator 35, the bandgap circuit 45 and the voltage divider circuit 46 correspond to a rectification switching unit.

[0059] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment and can be implemented in various modified forms. The control unit 21 and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor and a memory programmed to execute one or more functions embodied in a computer program. Alternatively, the control unit 21 and the method described in the present disclosure may be realized by a dedicated computer provided by configuring a processor with one or more dedicated hardware logic circuits. Alternatively, the control unit 21 and the method described in the present disclosure may be realized by one or more dedicated computers configured by a combination of a processor and a memory programmed to execute one or more functions and a processor configured with one or more hardware logic circuits. In addition, the computer program may be stored in a computer-readable non-transient tangible recording medium as instructions executed by a computer. The method for realizing the functions of each unit included in the control unit 21 does not necessarily need to include software, and all of the functions may be realized using one or more hardware.

[0060] In the above embodiments, multiple functions of one component may be realized by multiple components, or one function of one component may be realized by multiple components. Also, multiple functions of multiple components may be realized by one component, or one function realized by multiple components may be realized by one component. Also, part of the configuration of the above embodiments may be omitted. Also, at least part of the configuration of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0061] In addition to the above-described smart key 3, the present disclosure can also be realized in various forms such as a system including the smart key 3 as a component, a program for causing a computer to function as the smart key 3, a non-transitory tangible recording medium such as a semiconductor memory recording this program, and a control method.

Explanation of Signs

[0062] 2... vehicle-mounted device, 3... smart key, 21... control unit, 22... LF reception antenna, 41... primary battery, 42... storage battery, 43... changeover switch

Claims

1. A portable device (3) carried by a vehicle occupant, a receiving antenna (22) configured to receive a transmission signal transmitted from an on-board device (2) mounted on the vehicle; A control unit (21) configured to control the portable device; A primary battery (41) configured to supply power to the control unit; A secondary battery (42) configured to supply power to the control unit; a battery switching unit (43) configured to compare a primary battery voltage value, which is the voltage of the primary battery, with a secondary battery voltage value, which is the voltage of the secondary battery, and to switch the power supply to the control unit so that, when the primary battery voltage value is greater than the secondary battery voltage value, power is supplied from the primary battery to the control unit, and, when the primary battery voltage value is smaller than the secondary battery voltage value, power is supplied from the secondary battery to the control unit; A portable device comprising:

2. 2. The portable device according to claim 1, The receiving antenna is a portable device configured to receive the transmission signal using a charging coil (22a) configured to generate power by receiving power supply radio waves transmitted from a wireless charger (5).

3. 3. The portable device according to claim 2, The charging magnet (52) is arranged so as to vibrate inside the portable device when the portable device is moved, The portable device, wherein the charging coil is disposed in a position where the charging coil can generate power by electromagnetic induction between the charging coil and the charging magnet.

4. A portable device according to any one of claims 1 to 3, The secondary battery is a portable device including a capacitor.

5. A portable device according to any one of claims 1 to 3, The control unit is configured to stop a receiving function of receiving the transmission signal via the receiving antenna when a reception stop command transmitted from the wireless charger is received via the receiving antenna.

6. The portable device according to claim 2 or 3, further comprising: a rectifier circuit (32) arranged on a current path between the charging coil and the secondary battery, and configured to perform a rectification process of rectifying an AC current generated in the charging coil to convert it into a DC current and supplying the DC current to the secondary battery; a rectification switching unit (33, 34, 35, 45, 46) configured to switch a state of the rectification circuit between a rectification execution state in which the rectification circuit can execute the rectification process and a rectification stop state in which the rectification circuit cannot execute the rectification process, The portable device is configured such that the rectification switching unit switches the rectification circuit to the rectification execution state when a preset charging condition indicating that the primary battery voltage is low is satisfied, and switches the rectification circuit to the rectification stop state when the charging condition is not satisfied.

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