Study on the Parallel Electric Matching of High Power Piezoelectric Transducers

For high power piezoelectric transducers, resonant frequency tracking and impedance matching are necessary in order to obtain high energy transmission efficiency and stable working state. When a piezoelectric transducer is excited near its resonance frequency, the input electric impedance is capacitive. In order to compensate the capacitive impedance and increase the power factor, inductive matching circuit should be used, and it can be connected with the transducer in series or parallel. In this paper, the effect of the parallel matching inductor on the piezoelectric transducer is analyzed. The dependency of the resonance/anti-resonance frequency, the effective electromechanical coupling coefficient, the electric quality factor and the electroacoustic efficiency on the matching inductor is obtained. It is shown that when the parallel matching inductor is increased, the anti-resonance frequency is decreased and the resonance frequency unchanged; the effective electromechanical coupling coefficient and the electric quality factor are decreased; the electroacoustic efficiency at resonance frequency is unchanged and increased at anti-resonance frequency. The electric quality factor at resonance is less than that at anti-resonance. The electroacoustic efficiency at resonance frequency is larger than that at anti-resonance frequency. It is shown that the theoretically predicted relationship between the electromechanical characteristics and the parallel matching inductor is in good agreement with the experimental results.