Research On Improved Impedance Matching Circuit Of Ultrasound Transducer Based On Vapar

Power ultrasound is widely used in ultrasonic cleaning,ultrasonic welding,ultrasonic machining and ultrasonic extraction and so on,these applications have achieved good social and economic benefits.The key problem in power ultrasound is how to effectively convert electrical energy into mechanical energy.With the rapid development of power electronics devices and power electronics technology,some topologies that only existed in theory before have the foundation of practical application.This paper mainly studies the matching circuit of ultrasonic transducers,and proposes a inductive capacitor matching circuit based on Variable active-passive Reactance(VAPAR).Based on the traditional inductance-capacitance matching circuit,this circuit introduces a kind of variable active-passive reactance which can greatly change its equivalent inductance value.The theoretical basis of the inductance-capacitance matching circuit based on VAPAR is analyzed theoretically.The lumped parameter equivalent circuit model of ultrasonic transducer is introduced and the admittance circle theory is introduced to simplify the analysis.Then the matching theory of transducer are described and discussed in detail the series inductance matching circuit and the inductance capacitance matching circuit,points out that when the equivalent circuit parameters of the transducer changes due to outside influences,fixed parameters matching circuit enough to satisfy the requirement of the circuit matching,thus introducing VAPAR to improve the circuit.Then it introduces the principle,circuit topology and control method of VAPAR,determines the timing comparison control method to control the current of VAPAR,and discusses the overall system of the inductance and capacitance matching circuit based on VAPAR.An ideal linear method is used to analyze the parameter selection in VAPAR from a microscopic perspective.These parameters include the inductance value of the auxiliary inductor La,the voltage value of the dc power supply in the inverter and the time base of the timing comparison controller.From the three aspects of the tracking ability of VAPAR circuit current to the instruction current,the tracking error width and the commutation of the inverter,the ideal set of VAPAR parameter inequalities are derived from the situations where the simulated inductance is larger than the auxiliary inductor and the simulated inductance is smaller than the auxiliary inductor.On the basis of the inequality set and in combination with the actual loaded ultrasonic transducer,seven different frequency were selected to analyze the circuit state corresponding to VAPAR under ideal circumstances,so as to specify all the parameters of the inductance and capacitance matching circuit system based on VAPAR.Under the environment of Cadence PSpice A/D 16.6,the circuit modules are designed and simulated.Simulation results show that VAPAR can transform its own equivalent inductance according to the given value,and the external equivalent inductance value is basically consistent with the given value.The current harmonic components generated by VAPAR are not many and can be used normally.Caused by the change of equivalent circuit parameters for transducer series resonance frequency offset,ordinary inductance capacitance matching when the offset is can play a role of reactive power compensation,but when the frequency offset slightly,the compensation ability is insufficient,introducing VAPAR inductance capacitance matching circuit,matching circuit on the system reactive power can be enhanced by absorbing ability,broaden the operating frequency range of the circuit.