An Electromechanical Model for Clamped-Edge Bimorph Disk Type Piezoelectric Transformer Utilizing Kirchhoff Thin Plate Theory

Piezoelectric transformers (PTs) are currently being used to accelerate charged-particle beams for various applications [1, 2]. Beam interactions at the output of the PT can be treated as a parallel RC electrical load. The impedance of the load can affect the output voltage due to the small, finite amount of charge available in the PT. High output voltages necessary for beam acceleration cannot be achieved if the current output from the PT is too high. A thermionic electron emitter was used to provide a controllable beam current for testing the effects of electrical loading on the PT. The electron beam was operated in vacuum pressures of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> -10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-5</sup> Torr. Variations in the electron beam current were used to vary the resistive portion of the load while beam distance was used to vary capacitance. The effects of such variations were measured via bremsstrahlung interactions at the output electrode of the PT to determine output voltage and optical techniques for finding internal operating parameters such as electric field.

Research and development within piezoelectric transformer (PT) based converters are rapidly increasing as the technology is maturing and starts to prove its capabilities.Especially for high voltage and high step-up applications, PT based converters have demonstrated good performance and DC/AC converters are widely used commercially.The availability of PT based converters for DC/DC applications are very limited and are not that developed yet.I this paper an interleaved multi layer Rosen-type PT for high step-up and high output voltage is developed, for driving a 2.5kV dielectric electro active polymer actuator [17].The targeted application utilises an inductor-less half-bridge driving topology, where the reward of eliminating the series inductor is a reduction in component count, size and price.The absence of a series inductance calls for other means to avoid large hard switching losses and obtain soft switching capabilities.This can be achieved by utilising an advantageous PT structure, which is the main advantage of the interleaved Rosen-type PT.Furthermore the design should be further optimised, in order to achieve soft switching capability.The goal of this paper is to develop a soft switching optimised PT, capable of generating output voltages higher than 2kV from a 24V supply voltage.Furthermore finite element method (FEM) has been the main tool through the PT development.

Piezoelectric transformer (PT) is a combination of piezoelectric actuator and transducer, which serve as the primary side and the secondary side respectively. In the present study the disk – shaped (of 20 mm in diameter and 0.6 mm in thickness), unipoled radial mode piezoelectric transformer based on modified PZT-type solid solution was custom designed and fabricated. Different input and output area ratios of the PT were studied, namely: 21, 4, 1. The electrical properties like voltage step-up ratio, output power and temperature rise were measured for PT operating at the first resonance frequency. With the driving voltage of 20 VRMS, the 3 W output power, 165 VRMS output voltage an temperature rise of 20 0C was obtained for PT with the input/output area ratio of 1. The voltage step-up ratio of 12.5 was obtained for PT with input/output area ratio of 21.

A new kind of multilayer piezoelectric ceramic transformer for switching regulated power supplies is described. This transformer operates in the second thickness extensional vibration mode. Its resonant frequency is higher than 1 MHz. Theoretical calculations are implemented using a distributed constant electromechanical equivalent circuit method. It is calculated that this transformer can operate with higher than 90% efficiency. A fabricated transformer is examined. PbTiO/sub 3/ family ceramics are used because of the large anisotropy between electromechanical coupling factors. Results indicate that the piezoelectric transformer has good resonant characteristics, with little spurious vibration, and exhibits 16 W/cm/sup 3/ power density with high efficiency at 2 MHz. A switching regulated power supply, applying the piezoelectric transformer, is built and examined. >

A heterostructure possessing two concurrent operational modes: current sensing (CS) mode and current transduction (CT) mode and an enhanced current sensitivity associated with the CT mode is proposed by combining a magnetoelectric ring (MER) with a piezoelectric transformer (PET). The MER is a ring-shaped magnetoelectric laminate having an axially polarized Pb(Zr, Ti)O3 (PZT) piezoelectric ceramic ring sandwiched between two circumferentially magnetized, inter-magnetically biased Tb0.3Dy0.7Fe1.92 (Terfenol-D) short-fiber/NdFeB magnet/epoxy three-phase magnetostrictive composite rings, while the PET is a Rosen-type PZT piezoelectric ceramic transformer. The current sensitivity (SI) and magnetoelectric voltage coefficient (αV) of the heterostructure in the two operational modes are evaluated theoretically and experimentally. The CS mode provides a large SI of ∼10 mV/A over a flat frequency range of 10 Hz−40 kHz with a high resonance SI of 157 mV/A at 62 kHz. The CT mode gives a 6.4-times enhancement in resonance SI, reaching 1000 mV/A at 62 kHz, as a result of the amplified vortex magnetoelectric effect caused by the vortex magnetoelectric effect in the MER, the matching of the resonance frequencies between the MER and the PET, and the resonance voltage step-up effect in the PET.

Electromagnetic transformers have become obstacles to progress power supply miniaturization. Thus, piezoelectric transformers, which are more compact, immune to magnetic field and that present a high galvanic insulation, become more and more an alternative to electromagnetic transformers. In this paper, two different piezoelectric transformers have been studied and compared: a Rosen type and a radial mode type. The first approach consists in performing an analytical model. This approach is inspired by the technique used in electroacoustics and allows to build an electric equivalent circuit of the vibrating structure. The second approach deals with numerical finite element method using ANSYS software. A three-dimensional finite element model of each transformer has been then simulated to find out the resonance frequency but also to determine the transformation ratio as a function of the frequency for several values of the load resistance. In order to validate the models, experiments have been performed. Measurements of the voltage gain, output power and efficiency of both piezoelectric transformer types have been obtained and compared taking into account their characteristics.

The piezoelectric ceramic transformers as a source for a high voltage is used in a high‐energy density state due to its small size so that the energy loss causes increased heat generation and reduction of efficiency. Therefore, it must be treated not only for the voltage step up but as a power transmission system. In the conventional design method for the piezoelectric ceramic transformer, only the voltage ratio was considered important.In this paper, the piezoelectric ceramic transformer is considered as an asymmetric filter with a different capacitance ratio and different termination resistances of the input and output parts. The transmission frequency and the termination condition for a low propagation loss and a high‐voltage ratio were found. As a figure of merit of the piezoelectric ceramic transformer, the voltage ratio x relative bandwidth was proposed. By taking into account this value and the transmission attenuation, an optimum circuit condition of the piezoelectric ceramic transformer was obtained.

This paper reports lead zirconate titatanate (PZT)-on-silicon electromechanical resonators with excellent, 50 Ω terminated, performances for RF applications. A low 2.14 dB insertion loss is demonstrated for a length extensional, PZT-on-2-μm-silicon 15 MHz resonator. A 22 dB return loss and maximum unloaded quality factor, Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">UL, max</sub> , of ~540 in air resulted for this resonator. Similar performances with a Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">UL, max</sub> of 2850 are also demonstrated with a PZT fabricated on 10-μm-silicon device. The competing effects of decreased motional resistance and increased transducer capacitances with increased transduction area are addressed through analytical models and experimental results. Additionally, a third order length extensional mode piezoelectric resonator with asymmetric input and output electrodes were also designed to assess its potential performance as a piezoelectric resonant transformer; a 2.1× voltage boost is demonstrated for a 14.7 MHz extensional mode resonator.

Single-layer piezoelectric transformers with a unique design of polarization topologies

This paper is situated in the continuity of our works focused on the use of piezoelectric transformer (PT) in MOSFET/IGBT gate drives. In this paper, a new design method for a gate drive PT is presented. We have previously demonstrated that this kind of transformer can be successfully used in insulated MOSFETs/IGBT's gate drive circuits. An optimized multi-layered PT working in the second thickness mode has been studied for transmitting signal and energy in a gate drive circuit. Based on an analytical Mason model, the design method gives the minimal size of the multi-layer PT. Thickness of the PT is given by its mechanical resonance frequency and by maximum electrical field in the material. This method takes into account mechanical losses and heating of the piezoelectric material. Area of the PT is calculated considering the required secondary power P/sub 2/ and heating of the material. This analytical design method 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 based on this design process was fabricated and tested experimentally. Piezoelectric material used for primary and secondary layers is lead titanate, PbTiO/sub 3/, polarized along the thickness. Insulation between the primary and the secondary is achieved by a 300 /spl mu/m thickness layer of alumina, Al/sub 2/O/sub 3/. All calculated characteristics have been confirmed by measurements.

In recent years, piezoelectric transformer (PT) has attracted attention in many practical applications in power electronics field. But the fact that, PT still has some drawbacks and the most issue is the limitation of transferred power. The parallel connection of PTs is introduced As a solution to the problem that mentioned above. In the experiment part, a high output voltage DC/DC converter based on parallel connection of two market-available Rosen-type PTs are built in order to verify the capable of improving the output power of PT in parallel operating

An up to 5 Watts wide range power supply LED driver demonstrator with a piezoelectric transformer (PT) has been built to show the static and dynamic behavior as an off-line power supply. The target of the power converter controller using a PT, with 2.3 mm thickness and 17 mm diameter at frequency of 155-175 kHz, designed in a resonant circuit of class-E topology, is to maintain a constant output current of 290 mA/DC with variable output voltage drop at wide input voltage range of 85-250 V/AC. Also, the ZVS (zero-voltage-switching) condition is achieved over the full operation range. The used 1200 V fieldstop IGBT (1A-Type) shows losses around 200 mW over the full operating range for constant output current. The paper shows the regulation method for off-line power supplies using PT in class-E topology in constant current mode regulation (CCMR). The regulation algorithm has been programmed in C language operated by a 32-bit DSP (TMS320F2812). Besides, in the class-E application, the duty cycle of the switching frequency needs to be controlled in order to achieve the ZVS during the operation at different load and input condition. This goal is achievable only by phase locked loop (PLL) feedback in a satisfying way. To solve this problem, the idea of PT with an auxiliary tap has been applied. The application is suited for low size LED line adapters, to be integrated in bulb sockets. The results are applicable for any controller design of resonant PT step-down topologies. The several suited optimum control concept is investigated in this paper, considering the circuit expense being minimized

RF energy harvesting converts ambient signals into electrical power, providing a sustainable energy source. This study demonstrates the use of a piezoelectric transformer for efficient RF energy harvesting. In this work, a piezoelectric transformer (PT) is employed as a high-gain, efficient inverting amplifier to enhance RF wireless energy harvesting. The PT, composed of lead zirconate titanate (PZT), is placed after the receiving loop antenna, with its output connected to an AC-to-DC converter circuit. Maximum harvested power was observed at the PT's resonance frequency of 50 kHz, with an optimal load of 40 kΩ. The system, comprising the antenna, transformer, and rectifier circuit, continues to resonate at 50 kHz, as confirmed by input impedance measurements, demonstrating stable and effective performance. The overall system efficiency was characterized to be 88%.

For developing ring type ultrasonic motors and piezoelectric transformers, the method by V. Stephenson for the computation of resonance frequency of piezoceramic rings was extended. Engineering charts of the resonance frequencies of PZT rings with different sizes and at different clamping conditions were constructed. The resonance frequencies obtained from the charts were in good agreement with the experiments. Some interesting features of the resonance frequency with respect to the ring dimensions (the outside and inside diameters. OD and ID) were found. The resonance frequency for rings with the same outside diameter decreased with decreasing OD/ID ratio. Clamping of the outer circumference of the ring reduced the resonance frequency. There was a minimum in the curve of the resonance frequency versus OD/ID, when the inside of the ring was clamped. These features provided methods to reduce the resonance frequency so as to miniaturize ultrasonic motors and other piezoelectric devices using PZT rings.

This paper presents an inductor-less start-up converter for a sub-100-mV energy harvester based on an Armstrong oscillator topology using a piezoelectric transformer and a normally ON MOSFET. Two models of the converter have been detailed and validated experimentally for the start-up phase and steady-state operation to, respectively, determine the minimum start-up input voltage and the voltage gain. The models have been validated experimentally in a setup associating the converter and a thermoelectric generator. Based on a Rosen-type piezoelectric transformer and off-the-shelf components, the proposed start-up topology begins to oscillate at 15 mV and achieves a 1-V output voltage at only 43 mV. Compared to the literature, the topology needs no inductive component and achieves self-starting operation with a smaller input voltage.