| Traditional wired power supply way need a lot of wires and cables as the transmission medium which not only caused the waste of energy but also its safety and reliability will be greatly reduced with the growth of using time. Wireless power transfer technology (WPT) compared to the wired power supply has the advantages of high security, good reliability and it can be used into the harsh environment, so it is becoming the hot research.Firstly, the advantage, disadvantage and range of application of the three major WPT technologies are analyzed, in the dissertation. The magnetically coupled resonance (MCR) way which was suitable for the small and medium distance transmission was chosen as the focus study of this research, and the MCR wireless power transfer technology was used to drive LED lighting system.Secondly, the basic theory of the WPT technology which contained electromagnetic field theory, coupled module theory and circuit theory was introduced in this dissertation. Based on the circuit theory, the module of the WPT system was established, the transmission theory of the coupled coils was analyzed, the expression of the reflection impedance, efficiency and the output power were calculated and the factors which have influence to the system were analyzed. Considering of the low efficiency, small transmission distance and anti-interference ability of the WPT system, the impedance matching technology was used to improve the transmission ability of the WPT system. The impedance matching networks were placed on both of the source side and load side, the impedance matching network could be designed through theory calculation and Smith chart.Based on the theory analysis and research, the whole system, which can realize the function of both driving the LED lighting system with the wireless way and charging the Li battery with the capability of 3.7V/1800mA, was designed. With simulation software of MATLAB and Multisim, the relationship between the transmission performance of the system and distance, relative position, working frequency, coupling coefficient and load were researched, besides, the efficiency before and after the impedance matching were also analyzed.Finally, we made a sample device for the experiment and observed the influence of the coil distance to the output current and output power. By comparing the experiment results to the simulation results we can find that the data of the experimental have a little difference to the simulation results. After using the impedance matching technology, the efficiency of the WPT system can be improved from 40% to 85% which meets the design target. |
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