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A hybrid-loop control approach applied to inverter circuit design with piezoelectric transducers is proposed in this paper. This approach was motivated because the transducer is easily affected by the temperature effect and damping pressure, causing the mechanical frequency drift and unstable current variation. In view of these demerits, a hybrid-loop control mechanism is suggested to achieve both phase-tracking and constant-current control such that both operation frequency and vibration strength can be well controlled while maintaining a stable mechanical frequency. Moreover, by embedding this hybrid control concept into microprocessor controller units without adding any further sensors devices, the design cost is found to be meanwhile reduced. To validate the feasibility of this approach, the method has been validated through mathematical analysis and hardware realization. Test results confirm the performance improvement of the approach for piezoelectric transducer applications.

This paper proposes a plasma-driven system with piezoelectric transformer-based feedback control approaches along with a contactless power source. The research is motivated because many plasma-driven circuits employed the bulky components as resonant circuit and current feedback sensors. Hence, this study proposes to utilize one piezoelectric ceramic transformer to serve for both resonance tank and feedback devices in order to achieve the low cost and design simplification. Moreover, since the plasma discharge often suffers the problem of high humidity and particle-polluted environment, a contactless power transfer circuit integrated with a high-frequency coil is developed as the power source, by which the electrode damage can be better prevented. To reach a better discharge quality and own a higher flexibility of regulating power, the study also completes a constant-power control mechanism and a phase-locked loop control. Both software simulations and hardware realization have been accomplished. Analysis results and experimental outcome help validate the practicality of the proposed approach.Index Terms-Plasma discharge, piezoelectric transformer, contactless power transfer, phase-locked loop control.