| In wireless power transfer(WPT)technology,magnetic coupled resonant wireless power transmission(MCR-WPT)has the advantages of large amount of power conversion,suitable for short-range and medium short-range transmission,high transmission efficiency,and has been widely concerned and studied.Due to the advantages of simple structure,easy control and good high frequency effect,class-E inverter and class-E rectifier have become one of the most promising power converters in the MHz level MCR-WPT system.Therefore,it is very important to study the efficiency of MCR-WPT system based on Class E~2 converter.The MCR-WPT system based on class-E~2 converter studied in this paper consists of three units:Class-E inverter unit,class-E rectifier circuit unit and magnetic coupling resonance network unit.First of all,the transmission efficiency of these three units is analyzed and studied from the perspective of unit level.Then,from the perspective of system level,the system level design scheme to maximize the overall efficiency of this kind of system is studied.The transmission efficiency of magnetic coupling resonance network element is analyzed.Firstly,the influence of frequency,transmission distance and load on the transmission efficiency of coupled resonance network is studied.Due to the different output waveforms of different inverters,the transmission efficiency of the coupled resonant network caused by rectangular wave excitation and sine wave excitation is compared.The efficiency of class-E inverter is analyzed.According to the working process of class-E inverter,the optimal parameters of class-E inverter under soft switching condition are derived.Under the condition of optimal parameters,the working waveforms of class-E inverter and the influence of different factors on the transmission efficiency and working state of class E inverter are analyzed.The efficiency of class-E rectifier unit is analyzed.The power loss of diode in rectifier circuit is studied.According to the working process of class-E rectifier circuit,the constraint condition of soft switch state which makes it work in the highest efficiency is deduced.Simulation analysis of the optimal working state of the class-E rectifier circuit working waveform and different factors on the E-type rectifier circuit transmission efficiency and working state.The system level efficiency of MCR-WPT system based on class E~2 converter is studied.An optimal design scheme is proposed to maximize the overall efficiency of the system under given conditions,and the optimal load is determined.The effectiveness of the scheme is verified by simulation and experiment.Furthermore,aiming at the problem that the load deviates from the optimal value will lead to the system level efficiency decline,the maximum efficiency tracking control scheme is studied and designed.The simulation results show that the scheme can achieve the maximum efficiency under the condition of the load changing in a large range. |
