| 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 includes a first coil 11a, a second coil 11b, a third coil 11c, and a foreign matter detection circuit 10. The foreign matter detection circuit 10 outputs a first detection signal S1 having a first predetermined waveform to a first terminal T1 of a first coil 11a, and outputs a second detection signal S2 having a second predetermined waveform having a polarity opposite to that of the first predetermined waveform to a fifth terminal T5 of a third coil 11c so as to generate composite magnetic field striding between the first coil 11a and the third coil 11c, measures the variation amount of the impedance value of either the first coil 11a or the third coil 11c which corresponds to the composite magnetic field variation resulting from the presence or absence of a foreign matter, and determines that a foreign matter exists on the second coil 11b when the variation amount of the impedance value exceeds a predetermined value.SELECTED DRAWING: Figure 1 |
