FOREIGN OBJECT DETECTOR, POWER TRANSMITTER, POWER RECEIVER, AND WIRELESS POWER TRANSMISSION SYSTEM

A foreign object detector includes: an oscillator circuit having a coil and resonant capacitors Cx, Cy, the oscillator circuit being configured to output a voltage which includes an AC component and a DC component, the AC component having a positive cycle and a negative cycle; and an electric circuit for sensing a variation of the AC component and a variation of the DC component in the voltage output from the oscillator circuit when a foreign object approaches the coil