A review on piezoelectric transformer structural modeling is presented. The operating principle and the basic behavior of piezoelectric transformers as governed by the linear theory of piezoelectricity are shown by a simple, theoretical analysis on a Rosen transformer based on extensional modes of a nonhomogeneous ceramic rod. Various transformers are classified according to their structural shapes, operating modes, and voltage transforming capability. Theoretical and numerical modeling results from the theory of piezoelectricity are reviewed. More advances modeling on thermal and nonlinear effects also are discussed. The article contains 167 references.

http://zdsys.web.xtu.edu.cn:8081/xiangxinhuaeWebEditor_V280_Free_sp1/UploadFile/2012920153830754.pdf

Piezoelectric transformer structural modeling - a review

Piezoelectric ceramics are characterized as smart materials and have been widely used in the area of actuators and sensors. The principle operation of a piezoelectric transformer (PT) is a combined function of actuators and sensors so that energy can be transformed from electrical form to electrical form via mechanical vibration. Since PTs behave as band-pass filters, it is particularly important to control their gains as transformers and to operate them efficiently as power-transferring components. In order to incorporate a PT into amplifier design and to match it to the linear or nonlinear loads, suitable electrical equivalent circuits are required for the frequency range of interest. The study of the accuracy of PT models is carried out and verified from several points of view, including input impedance, voltage gain, and efficiency. From the characteristics of the PTs, it follows that the efficiency of the PTs is a strong function of load and frequency. Because of the big intrinsic capacitors, adding inductive loads to the PTs is essential to obtain a satisfactory efficiency for the PTs and amplifiers. Power-flow method is studied and modified to obtain the maximum efficiency of the converter. The algorithm for designing a PT converter or inverter is to calculate the optimal load termination, Y OPT , of the PT first so that the efficiency (power gain) of the PT is maximized. And then the efficiency of the dc/ac inverter is optimized according to the input impedance, Z IN , of the PT with an optimal load termination. Because the PTs are low-power devices, the general requirements for the applications of the PTs include low-power, low cost, and high efficiency. It is important to reduce the number of inductive components and switches in amplifier or dc/ac inverter designs for PT applications. High-voltage piezoelectric transformers have been adopted by power electronic engineers and researchers worldwide. A complete inverter with HVPT for CCFL or neon lamps was built, and the experimental results are presented. However, design issues such as packaging, thermal effects, amplifier circuits, control methods, and matching between amplifiers and loads need to be explored further. iii Acknowledgments I would like to thank my advisor, Dr. Fred C. Lee, for his support and guidance during the course of this research work. Without his constant correction on my research attitude, I would have never accomplish this work. I would like to express my boundless gratitude to my beloved wife, Kuang-Fen, …

Design and Analysis of Piezoelectric Transformer Converters

Piezoelectric Transformer Characterization and Application of Electronic Ballast

Piezoelectric transformers (PTs) are solid-state devices that transform electrical energy into electrical energy by means of a mechanical vibration. These devices are manufactured using piezoelectric materials that are driven at resonance. With appropriate design and circuitry, it is possible to step up and step down the voltages between the input and output sections of the piezoelectric transformer, without making use of magnetic materials and obtaining excellent conversion efficiencies. The initial concept of a piezoelectric ceramic transformer was proposed by Charles A. Rosen in 1954. Since then, the evolution of piezoelectric transformers through history has been linked to the relevant work of some excellent researchers as well as to the evolution in materials, manufacturing processes, and driving circuit techniques. This paper summarizes the historical evolution of the technology.

https://www.mdpi.com/2076-0825/5/2/12/pdf

Piezoelectric Transformers: An Historical Review

In this paper, a new complementary gate driver for power metal-oxide semiconductor field-effect transistors and insulated gate bipolar transistors is presented based on the use of a piezoelectric transformer (PT). This type of transformer has a high integration capability. Its design is based on a multilayer structure working in the second thickness resonance mode. A new design method has been used based on an analytical Mason model in order to optimize the efficiency, the available power at the transformer secondary ends, and the total volume. This design method takes into account mechanical losses and heating of the piezoelectric material; it can be extended to predict the characteristics of the PT: gain, transmitted power, efficiency, and heating of piezoelectric materials according to load resistance. A prototype of a PT rated for an inverter-leg gate driver was fabricated and tested experimentally. All calculated characteristics have been confirmed by measurements. Satisfactory results have been obtained in driving a 10-A/300-V/10-kHz chopper. Moreover, a study has been carried out about the propagation of common mode currents between the top-switch and the bottom-switch of the inverter leg throughout the driver in order to avoid cross-talking failures.

Piezoelectric transformer for integrated MOSFET and IGBT gate driver

A new type of piezoelectric transformer (PT) power converter incorporating the ZVS technique is presented. A combination of the ZVS technique and the PT successfully achieves higher efficiency. For low output voltage, using half-bridge rectifier stage, the converter achieved 72% efficiency, at V/sub in/=80 V, V/sub o/=11.8 V, and P/sub o/=5 W. For medium output voltage, using full-bridge rectifier stage, the converter achieved 83% efficiency at V/sub in/=80 V, V/sub o/=40 V, and P/sub o/=10.7 W. >

F.C. Lee

Papers

Piezoelectric transformer operating in thickness extensional vibration and its application to switching converter