Wireless power receiver and wireless power transmission system

A wireless power transmission system that transmits power from a wireless power transmitting device to a wireless power receiving device by wireless, wherein

• the wireless power transmitting device includes:
• a power conversion circuit that converts input DC power into AC power;
• a power transmitting coil that receives the AC power supplied from the power conversion circuit to generate an AC magnetic field;
• and
• a control circuit that controls the AC power to be supplied to the power transmitting coil, and
• the wireless power receiving device includes:
• a power receiving circuit including a power receiving coil that takes in AC power through the AC magnetic field and a rectifying circuit that converts the AC power received by the power receiving coil into DC power and outputs the DC power to a load;
• and
• a detection circuit that detects a circuit characteristic value of the power receiving circuit having a first peak having a relatively large peak value and a second peak having a relatively small value with respect to a horizontal separation distance between the power transmitting coil of the wireless power transmitting device and the power receiving coil,
• wherein the control circuit
• determines that the power receiving coil exists near the periphery of a position suitable for receiving power from the power transmitting coil when the circuit characteristic value detected by the detection circuit exceeds a first threshold value set between the peak value of the second peak and a detection limit value of the detection circuit, and
• calculates transmittable power from the wireless power transmitting device to the wireless power receiving device based on the circuit characteristic value detected by the detection circuit when the circuit characteristic value detected by the detection circuit exceeds a second threshold value set between the peak value of the second peak and the peak value of the first peak, and
• changes the second threshold value in accordance with a vertical distance between the power transmitting coil and the power receiving coil.

A wireless power receiving device that is mounted in a mobile body and configured to receive power transmitted from a wireless power transmitting device by wireless, the wireless power receiving device comprising:

• a power receiving circuit including a power receiving coil that takes in AC power through a magnetic field and a rectifying circuit that converts the AC power received by the power receiving coil into DC power and outputs the DC power to a load;
• a detection circuit that detects a circuit characteristic value of the power receiving circuit having a first peak having a relatively large peak value and a second peak having a relatively small value with respect to a horizontal separation distance between a power transmitting coil of the wireless power transmitting device and the power receiving coil;
• and
• a position detection circuit that detects a state of the relative position between the power receiving coil and the power transmitting coil, the position detection circuit determining that the power receiving coil exists near the periphery of a position suitable for receiving power from the power transmitting coil when the circuit characteristic value detected by the detection circuit exceeds a first threshold value set between the peak value of the second peak and a detection limit value of the detection circuit, calculating transmittable power from the wireless power transmitting device based on the circuit characteristic value detected by the detection circuit, when the circuit characteristic value detected by the detection circuit exceeds a second threshold value set between the peak value of the second peak and the peak value of the first peak, and determining that alignment between the power transmitting coil and the power receiving coil is not performed properly when the circuit characteristic value detected by the detection circuit does not exceed the second threshold value within a predetermined time period from when the circuit characteristic value exceeds the first threshold value.

A wireless power transmission system that transmits power from a wireless power transmitting device to a wireless power receiving device by wireless, wherein

• the wireless power transmitting device includes:
• a power conversion circuit that converts input DC power into AC power;
• a power transmitting coil that receives the AC power supplied from the power conversion circuit to generate an AC magnetic field;
• and
• a control circuit that controls the AC power to be supplied to the power transmitting coil, and
• the wireless power receiving device includes:
• a power receiving circuit including a power receiving coil that takes in AC power through the AC magnetic field and a rectifying circuit that converts the AC power received by the power receiving coil into DC power and outputs the DC power to a load;
• and
• a detection circuit that detects a circuit characteristic value of the power receiving circuit having a first peak having a relatively large peak value and a second peak having a relatively small value with respect to a horizontal separation distance between the power transmitting coil of the wireless power transmitting device and the power receiving coil, wherein the control circuit
• determines that the power receiving coil exists near the periphery of a position suitable for receiving power from the power transmitting coil when the circuit characteristic value detected by the detection circuit exceeds a first threshold value set between the peak value of the second peak and a detection limit value of the detection circuit,
• calculates transmittable power from the wireless power transmitting device to the wireless power receiving device based on the circuit characteristic value detected by the detection circuit when the circuit characteristic value detected by the detection circuit exceeds a second threshold value set between the peak value of the second peak and the peak value of the first peak, and
• determines that alignment between the power transmitting coil and the power receiving coil is not performed properly when the circuit characteristic value detected by the detection circuit does not exceed the second threshold value within a predetermined time period from when the circuit characteristic value exceeds the first threshold value.