The Design And Research Of Multi-load Wireless Constant Current Charging System

Wireless charging technology has become more and more widely used in portable electronic devices,and its security and convenience are unmatched by cable power supply methods.However,with the increasing number of electronic devices,the scenes where users charge multiple devices simultaneously are becoming more and more frequent.At this time,neither the existing wireless charging methods nor the traditional cable charging methods can get rid of the inconvenience and safety hazards caused by too much charging equipment,building a wireless charging platform that can power multiple electronic devices simultaneously is attracting increasing attention.At the same time,the increase in the frequency of utilization of electronic devices has led to a sharp increase in the demand for fast charging in applications.As a way of achieve fast charging,constant current charging technology has also been used more and more frequent.Implementing fast charging for multiple electronic devices is of great significance to the transformation of people’s lifestyles in the future.In this paper,a multi-load wireless constant current charging system is designed.Firstly,the wireless energy transmission mode and the basic architecture of one-tomultiple wireless charging system are studied and analyzed,and the basic topology of the transmission network is determined.Then the functions of each module on the sending end are introduced,the coil structure suitable for multi-load wireless charging system is designed,the working state and function of the inverter in the system are studied and analyzed.By detecting the current in the transmitting coil,the output power of the inverter is adjusted so that there is always a certain intensity of magnetic field distribution above the transmitting coil,which will satisfy the power supply requirement of the receiving end.Finally,the constant current charging control module in the receiving end is introduced and analyzed.The charging current of the energy storage battery is controlled by sampling the charging current and adjusting the output voltage of the DC-DC converter.In addition,the equivalent model of the battery under constant current charging state is also studied,and the overall transmission characteristics of the system are obtained.The multi-load wireless constant current charging system designed in this paper isolates the transmitting end and the receiving end from each other and is controlled independently by different control modules,therefore,the circuit parameters can be adjusted autonomously according to their working conditions,avoiding real-timecommunication requirements of multiple receiving ends and transmitting ends in the multi-load application scenario,reducing the complexity of the system and improving the response speed,making the constant current charging more stable.It is verified by experiments that when charging four 1.2V NiMH batteries,the receiving end at different positions can realize constant charging current of 100 mA for the battery in the coverage of the 20cm*20cm transmitter coil,the rectified output voltage fluctuation amplitude of each receiving end is within 0.2V,and the transmission efficiency of the system reaches 70%.