Effects of electron beam loading on an operating piezoelectric transformer

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.

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

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

In this paper, an analytical solution for a clamped-edge bimorph disk-type piezoelectric transformer with Kirchhoff thin plate theory is proposed. The electromechanical equations for transient motions are first derived, and coupled expressions for mechanical response and voltage output are obtained. For the case of excitation around the first resonant frequency, the resulting equations are further simplified. There are analytical solutions for a mechanical response, voltage, current, and power outputs. According to the analytical model, the output voltage is affected by the inner radius of the input and output electrodes, the radius of the piezoelectric transformer (PT), and the thickness ratio between the lead zirconate titanate (PZT) layer and the substrate. When the inner radius of the input electrode approaches zero (electrode becomes circular shape), it achieves maximum output voltage at the first resonance frequency excitation. On the contrary, when the inner radius of the output electrode approaches zero, the output voltage reaches its minimum value. Voltage ratios remain constant as the disk radius changes, and the first resonance frequency is inversely proportional to the square of the disk radius. The voltage ratio is fixed even with the miniaturization of the PT.

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.

Eight-poles of various designs, including an eight-terminal network with three input and five output terminals, are needed to replace some power objects. Especially when only the input and output characteristics of electrical energy are of interest. The paper presents the eightterminal network equations with three input and five output terminals, establishing a connection between these characteristics. Equations of the A-form establish a connection between the input and output voltages and currents; the B-form equations establish a connection between the output and input voltages and currents; G-form equations establish a connection between the input current, output voltages and output voltage, output currents; H-form equations establish the relationship between the input voltage, output currents and output current, output voltages; the Yform equations establish a connection between the input and output currents and the input and output voltages; The Z-form equations establish the relationship between the input and output voltages and the input and output currents. When implementing these equations, attention should be paid to the difference in the directions of the currents in each individual case.

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

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 objective of this study was to develop recommendations for an optimal design of piezoelectric transformer (PT) AC/DC converters. The paper presents a comprehensive comparison of the two commonly used rectifier topologies in a PT based power converters: current doubler and voltage doubler rectifiers. The advantages and disadvantages of the two rectifiers were investigated and the range of their applications with respect to output current, voltage, power capability, load resistance etc.-was delineated. Generic parameters are proposed and used to derive normalized and closed form equations that can help choosing a PT for a given set of requirements. Simulation and experimental results were found to be in a good agreement with the derivation of the theoretical analysis.

This paper proposes a piezoelectric transformer based on a resonant inverter that allows varying-capacity for ozone generation. The drawback of a piezoelectric transformer (PT) lies in its limited ability to transfer power, rendering it unable to provide sufficient current. Therefore, this study proposes a resonance topology with multiple modular parallel PTs using a PT-equivalent circuit derivation, and analyzes the resulting resonance curve characteristics. The proposed resonance topology can flexibly expand the output capacity, and stabilize the resonance characteristics and mechanical frequency. These results show that the proposed device is better suited to controller design. In addition, the study embeds an asymmetrical pulse width modulation (APWM) control concept into the microprocessor control unit such that the operating power of the ozone generator can be well regulated. This method has been realized with hardware circuit verification. Results demonstrate that the proposed inverter effectively drives the ozone generator system, regulates the operation power, and achieves the zero-voltage switching. The proposed design also ensures that the output current of each PT is evenly balanced, thereby facilitating the flexible capacity operations of the approach for industrial applications.

Recent experimental observations1 of collective ion acceleration produced when an intense relativistic electron beam was iniected into a low pressure neutral gas have firmly established a threshold beam current for the process which was predicted by Olson2; for this geometry ion acceleration does not occur unless the electron beam current (I) exceeds the space-charge limiting current (Il). In this paper we report additional observations of ion acceleration obtained in two series of experiments. In the first series, the guide tube and diode were configured to provide a large ratio of injected beam current to space charge limiting current, and drift tube endplate effects were examined. When the separation between the anode and tube endplate become less than the drift tube diameter the efficiency of the collective acceleration process is strongly reduced. In the second series of experiments the scaling of accelerated ion energy with electron beam kinetic energy was investigated using two electron beam machines which differ in stored energy by a factor of approximately 20. Using the larger machine proton energies in excess of 16.5 MeV have been attained. In addition, we also present an expression for the optimum pressure for ion acceleration in the drifting beam neutral gas geometry.

Summary form only given, as follows. The intense deposition of energy on to a high-Z target from a high current relativistic electron beam produces bremsstrahlung photons which can be used to generate radiographs of a dynamically evolving object. The interaction of the intense electron beam with the target can generate plasmas from the target surface. Consequently, a column of plasma ions expands away from the target due to the space charge potential of the electron beam. This expansion can lead to a larger beam spot size resulting in degradation of spatial resolution of radiographic images. Previous studies have shown that a self-biased electric potential between the target and the collimator can confine the ion column and maintain the electron beam spot size. In this work a two-dimensional particle-in-cell code is used to study a novel target configuration in which the converter target and the beam dump are connect electrically to maintain the self-biased potential in multiple-pulse radiography such as in the second axis of DARHT. Our simulation study showed that the self-bias electric potential between the target and the collimator was effective in confining the ions emitted from the target during multiple-pulse operation. The effects of the inductance of the target chamber on the decay time of the self-biased potential are also examined.

The use of CVD diamond for high-power switching using electron beam exitation

Pseudospark discharge is a discharge that occurs in the left band of the Paschen curve. According to previous studies, an electron beam will be generated in the initial stage of pseudospark discharge. This electron beam has the advantages of high energy, high current and self-confinement. It has a promising application in high-power microwave sources, surface treatment of metal materials, etc. To investigate the characteristics of this electron beam, a pseudospark discharge experimental platform is established in this paper. A pseudospark chamber is designed for pseudospark discharge. To trigger the discharge, a high voltage pulse trigger signal is generated by an avalanche transistor Marx circuit and a trigger unit is designed to generate trigger electrons. Faraday Cup is utilized to collect the electron beam and measure the electron waveform. In order to quantitatively characterize the electron beam, we define six electron beam characteristics, including trigger delay, peak current, electron beam charge, electron beam width, electron beam loop current ratio and electron beam loop charge ratio. To investigate the influence of gas pressure and gas type on electron beam characteristics, we experimentally obtained results of electron beam characteristics for different gas pressures and gas type. We mainly investigated the change rule of the electron beam characteristics when the gas pressure changes between 6 Pa and 20 Pa and the similarities and differences of the electron beams under the two gas environments, argon and nitrogen. We find that gas pressure can be used for the modulation of electron beam time delay. The width of the electron beam in the case of nitrogen has a very stable relationship with the gas pressure. Gas pressure and gas type are two important means of controlling the characteristics of pseudospark electron beams.

Piezoelectric transformer (PT) is attractive to the low power converting applications with advantages of high efficiency, small size, low EMI and high power density. This paper discusses ZVS conditions for a phase-lock control PT DC/DC converter, and we regulate the output voltage with the second loop. A 15 V to 45 V DC/DC converter is implemented with discrete circuit. Finally we show the experimental results