Real-Time Control of Resonance Point of Piezoelectric Transducers Based on Class D Power Converter

Piezoelectric transducers are the main element for generating ultrasonic waves in industry and medical applications. These energy converters are nonlinear loads. With a slightly change in temperature or mechanical load, their functional characteristics change that can lead to poor performance, so the converters should always work at the point corresponding to the lowest impedance (series resonance) to have optimal performance. A piezoelectric transducer is usually driven by a high-frequency sine wave DC-AC converter. In this paper, a new circuit based on the class D half bridge amplifier is proposed using perturbation and observation (P&O) control scheme. The proposed converter has high efficiency of 90%, with low cost and volume for high power applications. The use of two switches has made it easy to control. The simulation results are verified in Matlab R2016b and the system is implemented for frequency of 27 kHz, which yields to a practical THD of 3%.