Wireless charging device, wireless charging system, and power receiving device used therein

A power receiving device that receives power transmitted by wireless power transmission of a wireless charging device with a power receiving coil and performs charging of a secondary battery, the device comprising:

• a communication unit transmitting data to the wireless charging device;
• a temperature sensor;
• a rectifying/smoothing circuit generating a direct-current voltage from an induced current generated in the power receiving coil;
• and
• a charging control unit supplying the direct-current voltage that is input from the rectifying/smoothing circuit to the secondary battery,
• wherein the charging control unit acquires a temperature of the secondary battery by the temperature sensor, and transmits a quick charging request for performing quick charging with first transmission power to the wireless charging device through the communication unit until the temperature of the secondary battery reaches an upper limit temperature, and transmits a weak charging request for performing weak charging with transmission power that is lower than transmission power for maintaining the temperature of the secondary battery not to be higher than the upper limit temperature and is lower than the first transmission power of which a charging state is uninterrupted to the wireless charging device through the communication unit when the temperature of the secondary battery reaches the upper limit temperature.

A wireless charging device that includes a plurality of power transmitting coils and performs power transmission to a plurality of power receiving devices including a power receiving coil by wireless power transmission, the device comprising:

• a communication unit receiving data from the power receiving device;
• a plurality of power transmitting coil exciting circuits outputting an alternating-current voltage to each of the plurality of power transmitting coils;
• and
• a power transmitting control unit controlling the plurality of power transmitting coil exciting circuits to control transmission power that is transmitted by the plurality of power transmitting coils,
• wherein the power transmitting control unit acquires a temperature of a secondary battery of a charging target that is transmitted from the power receiving device through the communication unit, has control in each of the plurality of power transmitting coils such that quick charging is performed with first transmission power until the temperature of the secondary battery reaches an upper limit temperature, and weak charging is performed with transmission power that is lower than transmission power for maintaining the temperature of the secondary battery not to be higher than the upper limit temperature and is lower than the first transmission power of which a charging state is uninterrupted when the temperature of the secondary battery reaches the upper limit temperature, and repeats the quick charging with a time difference in the plurality of power transmitting coils.