| Matching circuit is an important part of ultrasonic vibration system,and its parameter design affects the vibration effect of the transducer and the energy efficiency of the ultrasonic vibration system.The matching technology of low-power ultrasonic power supply has been quite mature.Since the impedance of piezoelectric ultrasonic transducer has complex nonlinearity when working at high power,it is difficult to analyze the transducer under high power by the existing nonlinear theory,leading to the immature matching technology of highpower ultrasonic power supply.The parameter design generally depends on engineering experience.In order to solve the state analysis of piezoelectric ultrasonic transducer under high power and the optimization of matching parameters of high power ultrasonic power supply,the following research has been done:（1）According to the Mason equivalent circuit,the impedance characteristics of piezoelectric transducer at low power were analyzed,and the L-type matching calculation formula of inductance and capacitance between the frequency of capacitive region and resistive frequency of transducer was deduced.The main factors affecting the nonlinearity of piezoelectric ultrasonic transducer under high power were analyzed.（2）The influence of static pressure on the impedance characteristics of piezoelectric ultrasonic transducer under small signal was analyzed through experiments,and the influence law of static pressure on the equivalent electrical parameters and characteristic frequency of transducer was summarized.The impedance characteristics of transducer in plastic ultrasonic welding process were studied by dynamic dynamometer,and the average value of resonant resistance measured under static load was obtained,which approximated the resonant resistance during welding.The metal ultrasonic welding piezoelectric transducer working at anti-resonant frequency was studied.The mathematical model of anti-resonant resistance about driving voltage and driving frequency was proposed.The feasibility of the model was verified by experiments.（3）The impedance characteristics of inductance capacitance L-type matching circuit based on resistive state transducer were analyzed by MATLAB,and the influence of equivalent resistance and frequency of transducer on the tuning effect of matching circuit under fixed matching parameters was obtained.The transformer-inductance capacitance L-type matching circuit was studied by SABER simulation software.The influence of transformer ratio,matching inductance and matching capacitance on inductance current,output voltage and output current of matching circuit under capacitive,resistive and inductive topology was summarized,which provided reference for the optimization of matching parameters.The parameter optimization method of L-type matching circuit of transformer-inductancecapacitance for high-power ultrasonic power supply based on the fitting model of piezoelectric transducer anti-resonant resistance was proposed.（4）The matching experiment was carried out on the matching parameter optimization theory based on mathematical model.The matching parameters were designed by three different matching methods: low-power matching method,engineering experience method and matching parameter optimization method based on mathematical model.The matching parameters were evaluated from three aspects: transmission efficiency of matching circuit,filtering effect of matching circuit and welding morphology of weldment.The experimental results showed that the low-power matching law was not applicable in the high-power matching design,and the matching parameters obtained from low-power had serious detuning in practical work;compared with the matching parameters obtained from engineering experience,the optimized matching circuit based on model had higher power transmission efficiency and better frequency selection characteristics;The welding morphology is mainly related to the input power of transducer,welding effect is similar when power is similar. |
PDF Full Text Request