Driving an inductive piezoelectric transducer with class E inverter

Piezoelectric transducers are conventionally driven at their resonance frequency, where they show resistive characteristics. However, the resonance frequency does not take advantage of the loss reduction mechanism, which occurs between the resonance and anti-resonance frequency. The resonance drive leads to more heat generation and lower efficiency. In this paper, an innovative driving scheme of a Langevin piezoelectric transducer under its inductive frequency range is proposed, which takes advantage of the maximum efficiency frequency between the resonance and anti-resonance. In this approach, first, a constant vibration velocity measurement system is used to find the optimum driving frequency, which is defined as the point where the real input electric power is the lowest for a given output mechanical vibration level. The transducer has an inductive behavior at the optimum frequency. Next in this approach an equivalent circuit of the transducer based on Butterworth-Van Dyke (BVD) model is established, whose parameters are used to design Class E inverter driving circuits. Using MATLAB, two Class E inverters are precisely designed to drive the transducer at the resonance frequency (resistive) and transducer at the optimum frequency (inductive), impedance converter is added when driving at the optimum frequency. The required power for the optimum frequency driving method is reduced by 39% compared with the resonance frequency driving method, and smaller increase in temperature is also revealed according to the experiments.