A Driver for Piezoelectric Transducers with Control of Resonance

Variations in electric impedance curves of piezoeletric transducers occur under influence of mechanical load, temperature, electric excitation, among others. Electronic circuits for driving these transducers should correct the tune to maintain the performance of the transducer. Considering the changes at resonance, we have developed a circuit for a laboratory bench that performs two functions. The first, working on low power, by swapping frequencies around resonance, allows to the user define electric impedance and frequency operation that intend to apply in the experiment. The operation of this circuit is based on detection of magnitude of current in the transducer. A microcontroller and Labview are used to obtain the results. In the second, while under high power operation, deviations from original impedance are corrected by using a feedback network that evaluates amplitude of impedance. In this circuit, a class D MOSFET amplifier is used for exciting the transducer. Also, a microcontroller system controls the feedback network. Experiments with variation of mechanical loads have shown the effectiveness of the system.