A wireless charging apparatus, wherein the apparatus comprises a transmit end or a receive end; the transmit end comprises a transmit end resonant network and an inverter circuit, and the transmit end resonant network comprises a transmitting coil; the receive end comprises a receive end resonant network and a rectifier circuit, and the receive end resonant network comprises a receiving coil; the receive end further comprises an auxiliary coil; during wireless charging, a voltage at both ends of the auxiliary coil is generated by a current of the transmitting coil; and the apparatus further comprises a controller; the controller is configured to: • obtain (S3) a relative position between the transmit end and the receive end based on a self-inductance of the transmitting coil and based on at least one of the following parameters: a coupling coefficient between the transmitting coil and the auxiliary coil and a coil mutual inductance between the transmitting coil and the auxiliary coil, o wherein the relative position comprises a horizontal relative position and a vertical relative position, o wherein the vertical relative position is obtained by the controller based on the self-inductance of the transmitting coil and the horizontal relative position is obtained by the controller based on the at least one parameter, • obtain (S4) an alternating current impedance of the transmitting coil based on the horizontal relative position and the vertical relative position; • obtain (S4) a power loss at the transmit end based on the alternating current impedance of the transmitting coil and a current of the transmitting coil in a charging process; • obtain (S4) a transmit power based on an input power at the transmit end and the power loss at the transmit end; • obtain (S4) a foreign object loss based on the transmit power and a receive power at the receive end; and • when the foreign object loss is greater than a power threshold, determine (S4) that a foreign object exists between the transmit end and the receive end. • obtain (S3) a relative position between the transmit end and the receive end based on a self-inductance of the transmitting coil and based on at least one of the following parameters: a coupling coefficient between the transmitting coil and the auxiliary coil and a coil mutual inductance between the transmitting coil and the auxiliary coil, o wherein the relative position comprises a horizontal relative position and a vertical relative position, o wherein the vertical relative position is obtained by the controller based on the self-inductance of the transmitting coil and the horizontal relative position is obtained by the controller based on the at least one parameter, o wherein the relative position comprises a horizontal relative position and a vertical relative position, o wherein the vertical relative position is obtained by the controller based on the self-inductance of the transmitting coil and the horizontal relative position is obtained by the controller based on the at least one parameter, • obtain (S4) an alternating current impedance of the transmitting coil based on the horizontal relative position and the vertical relative position; • obtain (S4) a power loss at the transmit end based on the alternating current impedance of the transmitting coil and a current of the transmitting coil in a charging process; • obtain (S4) a transmit power based on an input power at the transmit end and the power loss at the transmit end; • obtain (S4) a foreign object loss based on the transmit power and a receive power at the receive end; and • when the foreign object loss is greater than a power threshold, determine (S4) that a foreign object exists between the transmit end and the receive end. <EOS>