Design Of Wireless Charging System With Optimal Efficiency Tracking Control

Along with the continuous renewal of electronic devices,wireless transmission technology is becoming a hot spot of the current application,in view of the small power electrical equipment,this paper developed a parallel-parallel type of wireless charging system,the system is improved in the transmitter single pipe LC resonant inverter circuit,improve the transmitting terminal input current waveform,reduce noise,improve the efficiency of the system.At the same time,in order to achieve the optimal efficiency of the system transmission,this paper uses the principle of the minimum power of the transmitter,adopts the voltage and frequency double closed-loop control strategy,so that the system can not only maintain a constant output voltage,but also track the optimal charging efficiency.In this paper,the steady-state equivalent model is established for the four resonant circuit topologies of magnetically coupled resonant radio energy transmission in the mode of single transmitter-single reception,and the influence of different factors on the efficiency is obtained by theoretical analysis of the four models.Under low power condition,parallel-parallel resonance circuit has higher transmission efficiency and longer transmission distance.Then the basic structure of the system is analyzed,and the working principle of the four-switch buck-boost circuit used in the voltage control circuit at the transmitting end,the multi-stage parallel variable capacitance circuit used in the resonant circuit at the transmitting end and the synchronous rectifier circuit at the receiving end is analyzed.Under the condition of small output power,it is simpler,higher power density and lower system design cost to adopt single-tube LC resonance circuit than to adopt half-bridge or full-bridge inverter topology.And then analyzed the proposed modified single pipe LC resonance circuit working principle and mode,and compared with the traditional single pipe LC resonance circuit,using Simulink simulation software,respectively,set up two kinds of circuit simulation model,and compared under no-load and load circuit waveform,verify the improved single pipe LC resonance circuit can effectively improve the transmitting terminal input current waveform,so it can measure,reduces the system static consumption at the same time,improve the system efficiency.This paper introduces three main closed-loop control methods for radio energy transmission systems: impedance matching,frequency tracking and dc-dc transformation.According to the advantages and disadvantages of the above three control methods,a voltage and frequency double closed-loop control method for parallel-parallel wireless transmission system is proposed.The transfer function is obtained by analyzing the small signal of the transmitting terminal voltage regulating circuit and then the control strategy parameters are designed.This paper analyzes the function of two frequency adjustments and the control program of flow design to achieve the design of optimal efficiency tracking control.Finally,the hardware and software parts of the system are studied in this paper,and the experimental model of parallel-parallel wireless charging system is built.The experimental test results show that the improved single-tube LC resonant circuit topology proposed in this paper can effectively reduce the static consumption of the system and improve the input current waveform.Based on QC3.0 standard,the overall transmission efficiency of the system can reach about 80% under the condition that the output is 5V/1A,5V/2A and 9V/2A.Compared with other low power wireless charging systems,the transmission efficiency of the parallel-parallel wireless charging system developed in this paper is greatly improved.