Design Of A Wireless Power Transfer System With Fixedfrequency Voltage Regulation

Compared with wired power transfer technology,wireless power transfer technology has the advantages of higher security,higher convenience,and wider application scenarios.Therefore,it has high research value and application prospects.At present,wireless power transmission has been applied to smart phones,Biomedical,electric vehicles and other fields.Aiming at the system stability problem caused by the change of load and coupling factor in the Wireless Power Transfer system(WPT),a wireless power transfer system is designed that conforms to the Qi protocol for fixed frequency voltage regulation control in this thesis.Firstly,the basic working principle and typical constituent circuit structure of the WPT is introduced,and the typical constituent circuit structure is compared and analyzed to determine the adopted structure.Secondly,the basic control method of the wireless power transmitter system is introduced,and the advantages of the fixed-frequency voltage regulation control scheme are obtained through comparative analysis from the aspects of efficiency,electromagnetic interference,and control complexity.Thirdly,the mutual inductance model and the transformer model are used to model the WPT,and the relationship between the output voltage gain of the different compensation circuits and the operating frequency,load,and magnetizing inductance is analyzed through mathematical derivation and theory.and the structure of the serial to serial-parallel compensation circuit is obtained.Better than the basic compensation circuit structure,and more suitable for the conclusion of fixed frequency control of the WPT.The WPT designed in this thesis mainly includes a step-down switching power converter with adjustable output voltage,a high-frequency full-bridge inverter,a serial to serialparallel compensation circuit,a rectifier filter circuit,a low-voltage linear regulator,and software achieve that conforms to the Qi protocol.The step-down switching power converter with adjustable output voltage is used to adjust the transmission power of the transmitter of the system.The rectifier filter circuit converts the high-frequency AC signal received by the receiver into a DC signal to power the low-voltage linear regulator to ensure constant voltage output.When the load and coupling factor change,the receiver detects the rectified and filtered output voltage and calculates the error with the reference value.The error is modulated and sent to the transmitter that makes adjustment according to the received information,thereby realizing the whole system close loop control.In this thesis,the open-loop simulation and closed-loop simulation of the system are carried out in matlab /simulink software to verify the feasibility of the fixed-frequency voltage regulation control scheme.By making a prototype,a test platform is built for testing.The test results show that the designed WPT can output a constant 12 V at an input voltage of 19 V,a transmission distance of 3mm to 7mm,a load of 15 W,and a constant voltage accuracy of less than 2%,and a maximum system efficiency of 81%.When the load and coupling factor change,the transmission power at the transmitter of the system can be adjusted.In addition,the WPT designed in this thesis conforms to the Qi protocol,so it has high engineering value and application prospects.