Quality factor concept in piezoceramic transformer performance description

Abstract

A new general approach based on the quality factor concept to piezoceramic transformer (PT) performance description is proposed. The system's quality factor, material elastic anisotropy, and coupling factors of the input and output sections of an electrically excited and electrically loaded PT fully characterize its resonance and nearresonance behavior. The PT efficiency, transformation ratio, and input and output power were analytically analyzed and simulated as functions of the load and frequency for the simplest classical Langevin-type and Rosen-type PT designs.A new formulation of the electrical input impedance allows one to separate the power consumed by PT from the power transferred into the load. The system's PT quality factor takes into account losses in each PT "input-outputload" functional components. The loading process is changing PT input electrical impedance on the way that under loading the minimum series impedance is increasing and the maximum parallel impedance is decreasing coincidentally. The quality-factors ratio, between the states of fully loaded and nonloaded PT, is one of the best measures of PTs dynamic performance-practically, the lower the ratio is, the better PT efficiency. A simple and effective method for the loaded PT quality factor determination is proposed. As was found, a piezoceramic with low piezoelectric anisotropy is required to provide maximum PT efficiency and higher corresponding voltage gain. Limitations on the PT output voltage and power, caused by nonlinear effects in piezoceramics, were established.

Optimum Phase Shift in the Self-Oscillating Loop for Piezoelectric-Transformer-Based Power Converters

“…where ω = 1/ √ LC is the series-resonance angular frequency of the PT [31], [32]. Therefore, resonant current is considered as sinusoidal waveform described in (3).…”

Analysis of Bidirectional Piezoelectric-Based Converters for Zero-Voltage Switching Operation

“…7 shows the input circuit of the converter and the related waveforms; the floating voltage v FP and the resonant current (i res ), which are studied in detail in the following analysis. Since piezo transformers have a high quality factor [34], higher harmonics are filtered out and only the fundamental component of the current passes through the output [27], [35]. Therefore, the resonant current is a sinusoidal waveform with a peak amplitude of I pk and a phase shift of φ.…”

A comparison of 1D analytical model and 3D Finite Element Analysis with experiments for a Rosen-type piezoelectric transformer

“…This model is a powerful tool that can describe the PT operating in an external electrical or mechanical environment. Various authors used the electrical equivalent circuit model and most of them made an invalid assumption [19,20], as they consider that the wave velocity in the primary and the secondary sides are equal, which is untrue. The constant velocity assumption leads to discrepancies between the measured and calculated characteristics of the PT [21,22], in particular significant errors (higher than 20%) on the values of resonance frequencies and voltage gain [17,23].…”