基于阻抗检测的多路自动调谐式无线充电金属检测系统

Impedance detection based multi-channel automatic tuning metal object detection system for wireless charging device

针对大功率磁感应式无线充电系统所产生的高频高强度电磁场能快速加热置于其中的金属异物以致发生危险的情况,提出一种金属检测系统,能快速准确地检测金属异物有无且不受功率磁场的干扰。首先,通过分析金属异物对线圈阻抗特性的影响,提出一种基于检测线圈阻抗变化的金属检测方法。提出并联谐振电路,将检测线圈阻抗变化放大映射到谐振电路输出电压变化,并通过理论计算获得检测电路的最优激励频率。接着,提出与无线充电线圈磁解耦的双极性检测线圈,能消除功率磁场的磁耦合干扰,同时其阻抗能较好反映金属介入情况。然后,提出多路自动调谐的控制方法,提高检测准确性和反应速度。最后,通过实验验证系统功能,结果表明该系统可检测到金属硬币的介入。

In view of the dangerous situation that the high-frequency and high-intensity electromagnetic field produced by the high power inductive coupled wireless charging system can quickly heat the foreign metal object placed in it,a metal object detection system is proposed,which can quickly but accurately detect whether the foreign metal object exists or not without the interference of the power magnetic field.Firstly,by analyzing the influence of metal object on coil impedance characteristics,a metal object detecting method based on detecting the variation of coil impedance is proposed.Parallel resonant circuit is proposed subsequently,which maps the variation of coil impedance to the variation of output voltage of the resonant circuit.And the optimal excitation frequency of detecting circuit is obtained by theoretical calculation.Then,bipolar detecting coils,which are magnetically decoupled from the wireless charging coils,are proposed.They can eliminate the magnetic coupling interference of the power magnetic field,and their impedance can reflect the metal interference efficiently.Subsequently,the multi-channel automatic tuning method is adopted to improve the detection accuracy and reaction speed.Finally,the function of the system is verified by experiment.The results show that the system can detect the interference of metal coins.