Design And Implementation Of Class E Power Amplifier For Magnetically-Coupled Resonant Wireless Power Transfer

As a kind of power transmission method that has been developed rapidly in recent years,wireless power transmission has been widely studied by scholars all over the world.Wireless power transmission has its unique advantages.It can realize the transmission of electric energy from power source to load without contact.This characteristic can break some limitations of traditional cable power transmission.Magnetically-coupled Resonant Wireless Power Transfer(MCR-WPT)is less affected by the external environment during transmission and thus becomes the most valuable wireless transmission method.As an important part of wireless power transmission system,high frequency power supply plays a decisive role in the whole system.At present,there are two main options for choosing the front-stage high-frequency power supply of MCR-WPT system: one is the inverting circuit with frequency less than 200 kHz and power of kilowatt level;the other is the power amplifier with frequency up to 1MHz and power of several or several dozen watts.However,little research has been done on how to improve the output power of MCR-WPT system operating at 1MHz.The main research work in this paper for this issue are as follows:(1)Based on the mutual inductance theory,the overall mathematical analysis of the MCR-WPT system is carried out.The circuit model of the MCR-WPT system and the characteristics and performance of the power transmission are studied.The voltage and current in the circuit are calculated by Kirchhoff's law and finally the relationship between the transmission efficiency of the system and the power supply frequency is derived.(2)The operating parameters of the basic class E power amplifier are designed under the working conditions of the soft switch.And the basic class E power amplifier is optimized in view of the mismatch state when the load resistance changes.The optimized class E power amplifier can maintain a stable output voltage when the load changes,and will reduce large peak voltage and peak current on the switch device because of the load mismatch.(3)According to the characteristics of class E power amplifier in high frequency situation,the power structure of three phase class E power amplifier and reverse parallel double class E power amplifier is proposed.The simulation results show that the proposed circuit structure not only has the high frequency characteristics of class E power amplifier,but also has significantly higher output power than class E power amplifier.(4)The class E power amplifier,three-phase class E power amplifier and reverse parallel double class E power amplifier are used as high frequency power supply of MCR-WPT system respectively.The whole MCR-WPT system is simulated by PSpice,and the simulation results are taken as theoretical reference.Taking the optimized class E power amplifier as an example,the experimental prototype of the MCR-WPT system is further built,and the experimental results verify the feasibility of the research.