A Resonance-Frequency-Tracing Method for a Current-Fed Piezoelectric Transducer

This paper presents a novel control method for a current-fed full-bridge inverter actuating an ultrasonic piezoelectric transducer (PT). In the conventional ultrasonic detection system, the PT has maximum transmitting gain at its series resonance frequency while having maximum receiving gain at its parallel resonance frequency. With the proposed approach, the PT could have maximum transmitting gain at the parallel resonance frequency and this frequency can be automatically traced, and hence adapted, to the environmental variation. A prototype circuit was constructed to verify the proposed control method. The experimental results show that the receiving voltage signal could have a maximum value at the parallel resonance frequency, and the traced frequency is 0.04 kHz higher than the parallel resonance frequency.