System for detecting foreign matter by sampling current phase difference

The invention discloses a system for detecting a foreign matter by sampling a current phase difference. The system is composed of a voltage-stabilizing power supply, an inverter, a sampling circuit, adetection coil, a capacitor and a controller. The sampling circuit is used for sampling a current zero-crossing point of a current signal outputted by an inverter. The controller is used for controlling the output frequency of the inverter to be greater than preset frequencies of resonant frequencies of the detection coil and the capacitor in advance, determining a phase difference between a voltage signal and a current signal that are outputted by the inverter, acquiring a current zero-crossing point of a voltage signal outputted by the inverter, calculating a current phase difference according to the sampled current zero-crossing point, and determining foreign matter existence in a detected environment when the current phase difference is smaller than a phase difference and the smallerphase difference is greate