Contactless battery charger, electronic device, battery pack, and contactless charging system

1. A contactless charger for charging, in a contactless manner, an electronic device using a secondary battery as a power source, the charger comprising:

a transceiving section configured to receives from the electronic device a full charge command indicating completion of recharging,

wherein the charger shifts,

upon receipt of the full charge command, to a charge stop state in which charging of the electronic device is not performed,

wherein the transceiving section is further configured to intermittently transmit, in the charge stop state, a load check signal for checking whether or not the electronic device is placed on the contactless charger in a rechargeable manner,

wherein the transceiving section is further configured to intermittently transmit, in the charge stop state, a charge restart check command for checking whether or not the electronic device requires recharging,

wherein the transceiving section is capable of transmitting the load check signal separately from the charge restart check command, and

wherein time intervals at which the charge restart check command is transmitted are larger than time intervals at which the load check signal is transmitted.

2. The contactless charger according to claim 1 , wherein

when it is ascertained by the load check signal that the electronic device is placed, the control section maintains the contactless charger in a charge stop state, and

when it is ascertained by the load check signal that the electronic device is not placed, the control section shifts the contactless charger to an initial state achieved immediately after activation of a power source.

3. The contactless charger according to claim 1 , wherein the transceiving section includes a coil that transmits power for recharging the electronic device; and the contactless charger further comprises a modulation section that superimposes the load check signal and the charge restart check command on power and that modulates the power.

4. The contactless charger according to claim 1 , wherein the transceiving section includes a coil that transmits power for recharging the electronic device; and the control section determines, based on a phase change in an electric current developing in the coil, that the electronic device is placed.

5. The contactless charger according to claim 1 , wherein the transceiving section includes a coil for transmitting power for charging the electronic device.

6. An electronic device that uses as a power source a secondary battery which can be charged by the contactless charger according to claim 1 .

7. The electronic device according to claim 6 , further comprising:

a control section that generates a full charge command configured to cause the contactless charger to shift to a charge stop state in which charging of the electronic device is not performed in response to completion of charge of the secondary battery; and

a transceiving section for transmitting the full charge command to the contactless charger,

wherein, when the transceiving section of the electronic device receives from the contactless charger the charge restart check command for checking whether or not the electronic device requests recharge in the charge stop state, the control section checks whether or not the secondary battery requests recharge; and, when the recharge is requested, the control section generates a recharge command indicating a request for recharge, and the transceiving section of the electronic device transmits the recharge command to the contactless charger.

8. An electronic device according to claim 6 , wherein the transceiving section includes a coil that receives from the contactless charger power for charging the secondary battery; and the electronic device further comprises a modulation section that superimposes the full charge command and the recharge command on an electric current generated by the electronic device and that modulates the electric current.

9. The electronic device according to claim 8 , wherein the modulation section differentiates the full charge command and the recharge command in terms of a difference in data sequence.

10. A contactless charging system including an electronic device and a contactless charger for charging the electronic device in a contactless fashion, wherein

the electronic device transmits a full charge command indicating that charge of the electronic device is completed;

the contactless charger configured to shift to a charge stop state in which charge of the electronic device is not performed, upon receipt of the full charge command;

the contactless charger configured to (1) intermittently generate, in the charge stop state, a load check signal for checking whether or not the electronic device is placed on the contactless charger in a state where the electronic device can be recharged, and (2) transmit the load check signal;

the contactless charger further configured to (1) generate, in the charge stop state, a charge restart check command for checking whether or not the electronic device requests recharge, and (2) transmit the charge restart check command separate from the load check signal; wherein

the contactless charger shifts to a power transfer state when it receives a recharge command indicating that the electronic device requests recharge in response to the charge restart check command, and remains in a charge stop state when it does not receive the recharge command in response to the charge restart check command; and

wherein time intervals at which the charge restart check command is generated are larger than time intervals at which the load check signal is generated.

11. The contactless charger of claim 1 , further comprising:

a modulation section configured to modulate a carrier wave with a load check signal modulated carrier or a charge restart check command modulated carrier; and

a control section configured to intermittently generate, in a charge stop state, the load check signal for checking whether or not the electronic device is on the contactless charger in a rechargeable manner.

12. The contactless charger of claim 11 , wherein the transceiving section is configured to transmit the load check signal modulated carrier separately from the charge restart check command modulated carrier, and

wherein time intervals at which the charge restart check command modulated carrier is transmitted are larger than time intervals at which the load check signal modulated carrier is transmitted.