Power feeding apparatus, power receiving apparatus, wireless power feeding system and method for wireless transfer of power

A power feeding apparatus comprising:

• an impedance detector;
• a controller configured to provide first control information and second control information based on an impedance detected by the impedance detector;
• a power transmitter configured to wirelessly transmit power, the power transmitter including a power feeding coil with a variable diameter;
• a variable matching circuit configured to change the variable diameter of the power feeding coil according to the first control information;
• and
• a signal transmitter configured to wirelessly transmit the second control information,
• wherein the second control information includes at least one of diameter change information, impedance detection result information, and setting information associated with an external variable matching circuit.

A wireless power feeding system comprising:

• a power feeding apparatus and a power receiving apparatus,
• the power feeding apparatus including:
• (a) an impedance detector;
• (b) a controller configured to provide first control information and second control information based on an impedance detected by the impedance detector;
• (c) a power transmitter configured to wirelessly transmit power to the power receiving apparatus, the power transmitter including a first power feeding coil with a first variable diameter;
• (d) a first variable matching circuit configured to change the first variable diameter of the first power feeding coil according to the first control information;
• and
• (e) a signal transmitter configured to wirelessly transmit the second control information to the power receiving apparatus;
• and
• the power receiving apparatus including:
• (a) a power receiver configured to wirelessly receive power from the power feeding apparatus, the power receiver including a second power feeding coil with a second variable diameter;
• (b) a signal receiver configured to wirelessly receive the second control information from the power feeding apparatus;
• and
• (c) a second variable matching circuit configured to change the second variable diameter of the second power feeding coil according to the second control information, wherein the second control information is based on the impedance detected in the power feeding apparatus.