| 摘要 |
PROBLEM TO BE SOLVED: To provide a foreign matter detection device capable of increasing the distance at which a foreign matter can be detected with high precision.SOLUTION: A foreign matter detection device 100 includes a first coil 11a, a second coil 11b, and a foreign matter detection circuit 10. The winding directions of the first coil 11a and the second coil 11b are identical to each other. The foreign matter detection circuit 10 outputs a first detection signal having a first predetermined waveform to a first terminal T1 of the first coil 11a, outputs a second detection signal having a second predetermined waveform having the same polarity as the first predetermined waveform to a third terminal T3 of the second coil 11b, makes the magnetic field from the first coil 11a and the magnetic field from the second coil 11b be repelled between the first coil 11a and the second coil 11b so as to measure the variation amount of the impedance value of any one of the first coil 11a and the second coil 11b which results from the presence or absence of a foreign matter 20, and determines that a foreign matter exists on the first coil 11a or the second coil 11b when the variation amount of the impedance value exceeds a predetermined value.SELECTED DRAWING: Figure 1 |
