| Wireless charging technology is a new type of power supply technology that uses non-electrical contact,which transfers energy from one side to the other,it can reduce the waste of line resources and avoid the safety accident caused by the power interface exposed to the air,so it has a broad application prospects.This paper will use magnetic coupling resonant way to design a medium power wireless charging system,its maximum output power can reach 100 W,and research the methods to improve the transmission efficiency and transmission distance of the system.The contents include the theoretical analysis and calculation of the system,the design of the system circuit and the preparation of the software,the coil simulation and the final experimental test.The main work is as follows:The first,Depth analysis of the working principle of the Magnetic coupling resonant wireless charging system.Obtained the coupling process of the system energy is by the coupling mode theory;then the equivalent circuit of the system is calculated,system parameters in a certain range of changes,the wireless charging system will appear frequency split phenomenon,and the change in the frequency of the split.Finally,analysis the change trend of the transmission efficiency of the coil when the coupling coefficient and the output load are changed.The second,according to the system design requirements,design the transmitter and receiver hardware circuit,draw the schematic and PCB of the system,boarding,welding and debugging,verify that the rectifier circuit,regulator circuit,inverter circuit and sampling circuit of the system are working properly.Which uses the synchronous rectifier and synchronous buck circuit to reduce the system when the work of energy loss;the transmitter and the receiver use radio frequency to communicate,it is more stable and faster than traditional carrier communication.The third,according to the needs of the system coil inductance,complete thedesign of loose coupling transformer.Through the Maxwell simulation design of the same self-inductance,different parameters of the coil model,analyze the change of coupling coefficient when the coil spacing is changed.Wound coil model for testing,when the coil self-inductance is kept constant,increasing the line and inner diameter of the coil can increase the coupling coefficient between the coils and slow down the coupling factor when the coil spacing increases.The last,experimental test of transmitter and receiver hardware circuit.Change the output load and the coil spacing,test system transmission efficiency at different operating frequencies.As the system operating frequency increases,the transmission efficiency will increase significantly,when the operating frequency is near the inherent resonant frequency,the transmission efficiency is maximized.When the output load and coil spacing are small and the system works near the inherent resonant frequency,the maximum output power is significantly reduced,the system frequency division phenomenon.The transmission efficiency of the test system when using different coils.Which increases the coil diameter and diameter can increase the transmission efficiency and transmission distance of the system.According to the test results to find a system operating frequency adjustment method,the starting frequency of the system is set to a value higher than the natural resonant frequency,and then according to the size of the receiving side of the rectifier voltage to determine whether the operating frequency is increased or decreased.Write the system load detection and energy transfer phase of the program,and the system software and hardware joint test.The system in the use of the inner diameter of 25 mm coil,the energy of the effective transmission distance can reach 20 mm,when the output power changes within the range of 100 W,the system transmission efficiency is more than 77%,the maximum transmission efficiency can reach 87.4%,to achieve the purpose of improving the system energy transmission efficiency and distance. |
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