Power feeding system, power feeding device, and power feeding method
A power feeding system has a power receiving device having: a resonant circuit having a receiving coil, a resonant capacitor configured to resonate with the receiving coil, and a first switching element configured to change an electrical connection state of the resonant capacitor; and a resonance control unit configured to control the first switching element, and has a power feeding device having: a second switching element connected in series to a feeding coil; a drive signal generation unit configured to generate a drive signal for driving the feeding coil; a variation detection unit configured to detect the change in electrical connection state of the resonant capacitor; and a power feeding control unit configured to control electric power supplied to the feeding coil based on a period of the resonant state and a period of the non-resonant state that are estimated from the periodic waveform variation.
1. A power feeding system, comprising:
a power feeding device having a feeding coil; and
a power receiving device having a receiving coil,
the power feeding system being configured to supply electric power from the power feeding device to the power receiving device through electromagnetic induction,
the power receiving device comprising:
a resonant circuit having:
the receiving coil configured to receive the electric power from the feeding coil;
a resonant capacitor configured to resonate with the receiving coil; and
a first switching element configured to perform switching between a resonant state and a non-resonant state by changing an electrical connection state of the resonant capacitor; and
a resonance control unit configured to control the first switching element based on received power by the receiving coil from the feeding coil, and power consumption of a load to which the received power is supplied,
the power feeding device comprising:
a second switching element connected in series to the feeding coil;
a drive signal generation unit configured to generate a drive signal for driving the feeding coil by switching the second switching element between a conductive state and a non-conductive state;
a variation detection unit configured to detect the change in electrical connection state of the resonant capacitor as a periodic waveform variation in an excited voltage excited in the feeding coil;
a variable power supply configured to vary a voltage value of a drive voltage supplied to the feeding coil; and
a power feeding control unit configured to control the voltage value of the drive voltage supplied to the feeding coil based on a period of the resonant state and a period of the non-resonant state that are estimated from the periodic waveform variation detected by the variation detection unit.
2. A power feeding system according to claim 1 , wherein the power feeding control unit is configured to change the voltage value of the drive voltage supplied to the feeding coil so that a ratio between the period of the resonant state and the period of the non-resonant state reaches a predetermined ratio.
3. A power feeding system according to claim 1 , wherein the power feeding control unit is configured to change the voltage value of the drive voltage supplied to the feeding coil so that a repetition cycle of the period of the resonant state and the period of the non-resonant state reaches a predetermined cycle.
4. A power feeding system according to claim 1 , wherein the power feeding control unit is configured to calculate a moving average over a plurality of cycles of a ratio between the period of the resonant state and the period of the non-resonant state, and control the voltage value of the drive voltage supplied to the feeding coil based on the moving average.
5. A power feeding system according to claim 1 , wherein the resonance control unit is configured to control the first switching element so that the resonant circuit is set to the resonant state when a voltage of a supply line through which the received power is supplied to the load is equal to or less than a predetermined threshold value, and control the first switching element so that the resonant circuit is set to the non-resonant state when the voltage of the supply line is larger than the predetermined threshold value.
6. A power feeding system according to claim 1 , wherein the power feeding control unit comprises a drive control section configured to determine whether or not the electric power can be supplied to the power receiving device based on the periodic waveform variation detected by the variation detection unit, and control whether or not to continue supply of the drive signal to the second switching element based on a result of the determination.
7. A power feeding device configured to supply electric power to a power receiving device through electromagnetic induction,
the power receiving device comprising:
a resonant circuit having:
a receiving coil configured to receive the electric power from a feeding coil;
a resonant capacitor configured to resonate with the receiving coil; and
a first switching element configured to perform switching between a resonant state and a non-resonant state by changing an electrical connection state of the resonant capacitor; and
a resonance control unit configured to control the first switching element based on received power by the receiving coil from the feeding coil, and power consumption of a load to which the received power is supplied,
the power feeding device comprising:
a second switching element connected in series to the feeding coil;
a drive signal generation unit configured to generate a drive signal for driving the feeding coil by switching the second switching element between a conductive state and a non-conductive state;
a variation detection unit configured to detect the change in electrical connection state of the resonant capacitor as a periodic waveform variation in an excited voltage excited in the feeding coil;
a variable power supply configured to vary a voltage value of a drive voltage supplied to the feeding coil; and
a power feeding control unit configured to control the voltage value of the drive voltage supplied to the feeding coil based on a period of the resonant state and a period of the non-resonant state that are estimated from the periodic waveform variation detected by the variation detection unit.
8. A power feeding device configured to supply electric power, through electromagnetic induction, to a power receiving device having a receiving coil, a resonant capacitor configured to resonate with the receiving coil, and a first switching element configured to perform switching between a resonant state and a non-resonant state of the resonant capacitor,
the power feeding device comprising:
a feeding coil;
a second switching element connected in series to the feeding coil;
a drive signal generation unit configured to generate a drive signal for driving the feeding coil by switching the second switching element between a conductive state and a non-conductive state;
a variation detection unit configured to detect a change in electrical connection state of the resonant capacitor as a periodic waveform variation in an excited voltage excited in the feeding coil;
a variable power supply configured to vary a voltage value of a drive voltage supplied to the feeding coil; and
a power feeding control unit configured to control the voltage value of the drive voltage supplied to the feeding coil based on a period of the resonant state and a period of the non-resonant state that are estimated from the periodic waveform variation detected by the variation detection unit.
9. A power feeding method for a power feeding system configured to supply electric power from a power feeding device to a power receiving device through electromagnetic induction,
the power receiving device comprising a resonant circuit having a receiving coil configured to receive electric power, a resonant capacitor configured to resonate with the receiving coil, and a first switching element configured to perform switching between a resonant state and a non-resonant state by changing an electrical connection state of the resonant capacitor,
the power feeding device comprising a feeding coil, a second switching element connected in series to the feeding coil, and a variable power supply coupled to the feeding coil and configured to supply a drive voltage having a variable voltage value to the feeding coil,
the power feeding method comprising:
generating a drive signal by the power feeding device for driving the feeding coil by switching the second switching element between a conductive state and a non-conductive state;
controlling the first switching element by the power receiving device based on received power by the receiving coil from the feeding coil, and power consumption of a load to which the received power is supplied;
detecting the change in electrical connection state of the resonant capacitor by the power feeding device as a periodic waveform variation in an excited voltage excited in the feeding coil; and
controlling the variable voltage value of the drive voltage supplied to the feeding coil by the variable power supply based on a period of the resonant state and a period of the non-resonant state estimated from the periodic waveform variation.