| Summary: | In the wireless charging system, the power transmission follows the magnetic coupling relationship between the transmitting coil and receiving coil. When there are metal foreign objects between the transmitting coil and receiving coil, the eddy current effect or magnetic focusing effect of the foreign objects will affect the transmission performance and operational stability of the wireless charging system, and in severe cases, it can also endanger charging safety. In order to clarify the influence mechanism of metal foreign objects with different materials on the performance of wireless charging system and effectively analyze the influence law of foreign objects, an accurate modeling method of metal foreignobjects is urgently needed to improve the detection accuracy of metal foreign objects. Therefore, an equivalent modeling method of metal foreign objects field is proposed, taking into account the key factors of metal material, location, equivalent area and so on. By constructing the coupling equation of wireless charging system under the influence of metal foreign objects, the expression of phase difference between the transmitting coil current and receiving coil current before and after the introduction of foreign objects is obtained. On this basis, the equivalent coil model of ferromagnetic metal and non-ferromagnetic metal and its parameter configuration method are further proposed, which can accurately obtain the current phase difference under the condition of metal foreign objects intervention. Finally, the accuracy and effectiveness of the modeling method are verified by simulation and experiment. This method provides a new idea for the characteristic analysis and online detection of metal foreign objects introduced in wireless charging system.
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