Research On The Characteristics Of Integrated Piezoelectric Transformer With Self-compensation Of Capacitive Impedance

Piezoelectric transformer(PT)realizes the mutual conversion between electrical energy and mechanical energy through the positive and negative piezoelectric effect of piezoelectric materials,and has the advantages of high power density,small size,simple structure and low cost.It is expected to become a substitute for traditional electromagnetic transformers.Generally,the piezoelectric transformer needs to add an additional inductance element for capacitive compensation in the driving,so that the peripheral driving circuit can realize the zero voltage state and obtain high efficiency.However,the additional electromagnetic components make the piezoelectric transformer drive more complicated,reducing the advantages of miniaturization and no electromagnetic interference of the piezoelectric transformer.In order to realize the capacitive impedance compensation of the piezoelectric transformer in the drive,while avoiding the use of electromagnetic components.Based on the piezoelectric inductor(PL)concept proposed by the researchers,this paper designs an integrated piezoelectric transformer(IPT)based on piezoelectric inductors and piezoelectric transformers.The characteristics of the integrated piezoelectric transformer are analyzed through finite element simulation and experiment.The main research contents of this paper are as follows:(1)Theoretical model of piezoelectric inductor.The knowledge of piezoelectric theory is briefly summarized from the three aspects of piezoelectric effect,piezoelectric equation and piezoelectric transformer equivalent circuit model,which lays the foundation for the proof of piezoelectric inductor theory.Based on the lumped parameter model and the piezoelectric motion equation,combined with the analysis of the radial motion of the piezoelectric ceramic thin ring,the theoretical model of the piezoelectric inductor is established,and the existence conditions of the piezoelectric inductor theory are derived.The analysis shows that the piezoelectric structure will show excellent inductive characteristics in the system’s resonance and anti-resonance frequency range.In addition,the paper theoretically analyzes the influence of piezoelectric material parameters on piezoelectric inductance based on the electrical equivalent model of the piezoelectric structure.(2)The impedance characteristic simulation and experimental measurement of the integrated piezoelectric transformer.Combining the concept and working principle of piezoelectric inductor,the paper proposes an integrated piezoelectric transformer design scheme: a piezoelectric inductor and a piezoelectric transformer are designed on the same piece of piezoelectric ceramic material,and the two are electrically connected in series and mechanically connected in parallel.Through COMSOL Multiphysics software simulation modeling,the impedance characteristics of piezoelectric transformers with and without integrated piezoelectric inductor were compared and analyzed,and then the impedance phase and amplitude of piezoelectric transformers before and after integration were tested with the help of experiments.The simulation and experimental results prove that the piezoelectric transformer with integrated piezoelectric inductor can realize capacitive impedance self-compensation well.(3)Integrated piezoelectric transformer driving simulation and experiment.The paper simulated and experimented the driving performance of integrated and independent piezoelectric transformer,and compared the characteristics of the two.First,through frequency domain simulation analysis and sinusoidal drive experiments,the results show that the integrated piezoelectric transformer has a wider high-efficiency frequency range and a higher step-up ratio.Secondly,through the Spice netlist combined with COMSOL’s transient analysis and square wave drive experiment,the results show that under the same excitation voltage,the drive efficiency of the integrated piezoelectric transformer is about 10% higher than that of a single piezoelectric transformer.The successful integration of piezoelectric inductors and piezoelectric transformers provides new ideas for the integration and miniaturization of piezoelectric devices in the future.