Research On Constant Current And Constant Voltage Wireless Charging System

With the development of science and technology,wireless power transmission technology is getting more and more attention.Compared with the wired charging method,the wireless charging technology has the advantages of convenience,safety and strong environment application,which can solve the problems of traditional wired power supply.At present,the wireless charging of energy storage battery usually adopts the combination of constant current and constant voltage charging to avoid overcharging in constant current model or undercharging in constant voltage model.In order for the constant current mode to be switched to the constant voltage mode immediately and smoothly,communication between the primary and secondary side,as well as complex control methods at the primary side or DC conversion circuit at the secondary side is usually required,which will undoubtedly increase the difficulty of system control and the system volume.For this problem,this paper starts from the design of constant current and constant voltage hybrid compensation network and realizes the conversion of charging mode by switching compensation topology at the secondary side.In addition,in order to reflect the secondary charging or running state,the phase modulation principle is used to carry out the reverse transmission of the signal.Firstly,starting from the basic compensation network and the composite resonant compensation network,the constant current or constant voltage output characteristics of the SS,SP,LCL/LCC,and S/SP compensation networks are analyzed in detail based on the loosely coupled transformer mutual inductance and leakage inductance model.In view of the above-mentioned deficiency of the compensation network design,the T/S compensation network design process based on the two-port network is introduced,and different voltage or current gains can be obtained without changing the transformer.Secondly,two hybrid compensation networks are designed for single load wireless charging system,which can realize constant current and constant voltage output switching and ZPA.The design process of the compensation network parameters is analyzed in detail and the sensitivity of the compensation network parameters is deduced as well.In addition,the order of the switching action is analyzed in depth.In order to improve the transmission efficiency of the system,the implementation of ZVS is introduced.The output characteristics of constant currentand constant voltage are verified by simulation,and the load characteristics and transmission efficiency of the system are analyzed fully.The experimental results show that the system can achieve better constant current or constant voltage output and can change compensation topology smoothly.Thirdly,in order to realize multi-load constant current and constant voltage wireless charging,a wireless charging system with primary side series or LC compensation is designed.The constant current or constant voltage output characteristic and its parameters design principle of LCL-LC/LCL hybrid compensation network are analyzed.The closing and disconnecting order of the switch as well as parameter sensitivity is introduced in detail.Considering the influence of external conditions or component parasitic parameters,the system transmission efficiency and load characteristics are deduced in detail.In order to achieve a better constant current and constant voltage output,the operating frequency can be appropriately increased.The constant current output,constant voltage output and constant current constant voltage output characteristics are verified by building a two-load wireless charging system platform.Finally,in order to reflect the charging state of the secondary side,based on the ZPA characteristics of the constant current and constant voltage wireless charging system,the reverse transmission of the signal is realized according to the principle of phase modulation.From the influence of the capacitance parallel position on the output characteristics of the system,the capacitance parallel position in different output mode is determined respectively.The sensitivity of the input impedance angle of the system to the capacitance is analyzed.At the same time,the influence of quality factor,load RL and system frequency on the accuracy of signal transmission is also introduced.In addition,the rate of signal transmission is analyzed.Experimental results verify the feasibility of signal transmission based on the phase modulation.