Device and system for power transmission
A device for power transmission includes a power transmission section and a detection section. The power transmission section is configured to transmit an electric power wirelessly. The detection section is operatively connected to the power transmission section and configured to detect an object within a range from the power transmission section based on a change in impedance in vicinity of the power transmission section.
1. A power transmitter, comprising:
a power generation circuit configured to supply an electric power to a resonance circuit, the resonance circuit including a power transmitting coil, the power transmitting coil being configured to carry out noncontact power feeding to a power receiver through a magnetic field;
a measurement circuitry configured to measure a voltage across a resistor arranged in series with the power transmitting coil periodically; and
a controller configured to determine a presence or absence of a foreign object within a range from the power transmitting coil based on the voltage across the resistor periodically,
wherein the noncontact power feeding to the power receiver is carried out for a predetermined period after the controller determines that the foreign object is absent within the range,
the measurement circuitry is configured to measure the voltage across the resistor after the noncontact power feeding to the power receiver is finished,
a first frequency is used to determine the presence or absence of the foreign object within the range from the power transmitting coil, and
a second frequency, different from the first frequency, is used to carry out the noncontact power feeding to the power receiver.
2. The power transmitter according to claim 1 , wherein
the power transmitting coil is configured to transmit an electric power wirelessly to a power reception circuit of the power receiver; and
the measurement circuitry is configured to measure the voltage across the resistor before the electric power is wirelessly transmitted to the power reception circuit.
3. The power transmitter according to claim 2 , wherein the power receiver comprises a load that is configured to perform predetermined operations based on the electric power transmitted to the power reception circuit.
4. The power transmitter according to claim 3 , wherein the load is configured to charge a battery based on the electric power transmitted to the power reception circuit.
5. The power transmitter according to claim 1 , wherein the controller is configured to monitor impedance based on the voltage and detect the foreign object based on the impedance.
6. The power transmitter according to claim 1 , wherein the controller is configured to:
compare the voltage across the resistor with a threshold value; and
detect the foreign object based on the comparison.
7. A power transmitting apparatus, comprising:
a resonance circuit including a power transmitting coil;
a resistor arranged in series with the power transmitting coil;
a power generation circuit configured to supply electric power to the resonance circuit, the power transmitting coil being configured to carry out noncontact power feeding to a power receiver through a magnetic field;
a measurement circuitry configured to measure a voltage across the resistor periodically; and
a controller configured to determine a presence or absence of a foreign object within a range from the power transmitting coil based on the voltage across the resistor before the noncontact power feeding to the power receiver is carried out,
wherein the noncontact power feeding to the power receiver is carried out for a predetermined period after the controller determines that the foreign object is absent within the range,
the measurement circuitry is configured to measure the voltage across the resistor after the noncontact power feeding to the power receiver is finished,
a first frequency is used to determine the presence or absence of the foreign object within the range from the power transmitting coil, and
a second frequency, different from the first frequency, is used to carry out the noncontact power feeding to the power receiver.
8. The power transmitting apparatus according to claim 7 , wherein
the power transmitting coil is configured to transmit an electric power wirelessly to a power reception circuit of the power receiver, the power receiver comprising a load that is configured to perform predetermined operations based on the electric power transmitted to the power reception circuit; and
the measurement circuitry is configured to measure the voltage across the resistor before the electric power is wirelessly transmitted to the power reception circuit.
9. The power transmitting apparatus according to claim 8 , wherein the load is configured to charge a battery based on the electric power transmitted to the power reception circuit.
10. The power transmitting apparatus according to claim 7 , wherein the controller is configured to monitor impedance based on the voltage and detect the foreign object based on the impedance.
11. The power transmitting apparatus according to claim 7 , wherein the controller is configured to:
compare the voltage across the resistor with a threshold value; and
detect the foreign object based on the comparison.
12. A power transmitting system comprising:
a power transmitting apparatus and a power receiving apparatus,
wherein the power transmitting apparatus comprises:
a resonance circuit including a power transmitting coil;
a resistor arranged in series with the power transmitting coil;
a power generation circuit configured to supply electric power to the resonance circuit, the power transmitting coil being configured to carry out noncontact power feeding to the power receiving apparatus through a magnetic field;
a measurement circuitry configured to measure a voltage across the resistor periodically; and
a controller configured to determine a presence or absence of a foreign object within a range from the power transmitting coil periodically,
wherein the noncontact power feeding to the power receiving apparatus is carried out for a predetermined period after the controller determines that the foreign object is absent within the range,
the measurement circuitry is configured to measure the voltage across the resistor after the noncontact power feeding to the power receiving apparatus is finished,
a first frequency is used to determine the presence or absence of the foreign object within the range from the power transmitting coil, and
a second frequency, different from the first frequency, is used to carry out the noncontact power feeding to the power receiving apparatus.