Analysis and modeling of a piezoelectric transformer in high output voltage applications

2009 IEEE Energy Conversion Congress and Exposition

2009

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--A digital control method for optimal capacitor charging was developed and tested by simulations and experimentally. The control algorithm follows the concept of first searching for the optimal charging conditions of the given power stage and then using the collected data in the free running operation. The major advantage of this control approach is that it eliminates the uncertainty due to parameters variations and that it can be applied to any type of capacitor charger configuration by setting the desired charging profile objectives. The method is demonstrated on a piezoelectric transformer based power stage that behaves like a resonant converter. To further increase the accuracy of the control for this resonant converter case, we applied a frequency resolution enhancement algorithm that allows fine tuning of the drive. Excellent agreement was obtained between the analytical derivations, simulations and experimental results.

Section: Analysis Of Optimal Capacitor Charging By a Pt Based Comentioning

confidence: 83%

“…However, the output impedance that the converter "sees" is changing as a function of the voltage across the output capacitor [11,12]. As a result, the switching frequency has to track the resonant frequency of the network which varies during the charging operation.…”

Section: Analysis Of Optimal Capacitor Charging By a Pt Based Comentioning

confidence: 99%

A heuristic digital control method for optimal capacitor charging

Peretz

2009 IEEE Energy Conversion Congress and Exposition

2009

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“…As shown in [5], the voltage doubler and load section can be represented as an equivalent reactive load (a resistor in parallel to a capacitor). Consequently the gain function (8) is valid for this case too, except that the load resistance and output capacitance in Fig.…”

Section: Rosen Type Pt In Hv Applicationsmentioning

confidence: 99%

Maximum power tracking of piezoelectric transformer HV converters under load variations

IEEE Trans. Power Electron.

Lineykin

2006

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Abstract-The problem of maximum power point tracking of high output dc voltage converters that apply piezoelectric transformers (PT) and voltage doublers was studied theoretically and experimentally. It was shown that the operating frequency of the PT, at which maximum power is reached, is a function of the load. Hence, under load variations, and to overcome parameter instability, there is a need for some frequency tracking mechanism that will help to lock the operating frequency to the optimum one. The proposed method to achieve frequency tracking is based on a phase locked loop (PLL). The PLL inputs are the phase of the input voltage driving the PT and the phase of the current flowing through one of the voltage doubler diodes. Theoretical analysis, verified by experiments, shows that when the phase shift of the diode current relative the phase of the input voltage is zero, the voltage gain of the system is at its maximum. By applying this approach, the system's operation can be made independent of input voltage, load variations, temperature (within a permitted range), and the spread and nonlinearity of the PT parameters, as well as their drift with time.Index Terms-Phase locked loop (PLL), piezoelectric transformers (PTs).

“…As was shown earlier [6], the frequency of maximum output is different from the mechanical resonant frequency. The principle of operation of the VD rectifier when operating at the maximum output voltage mode was studied in [4] and is further developed in the present work. Current doubler rectifier operating at the mechanical resonant frequency of PT was studied by number of investigations [1,5] while the present work studies its operation at the maximum output voltage mode.…”

Section: The Comparative Circuits and The Comparison Principlesmentioning

confidence: 99%

“…The comparison methodology, applied in this study, follows the concept of representing the output capacitor of PT and the rectifier sections by an equivalent circuit [1][2][3]. The equivalent circuit is linear and is composed of a parallel RC network that loads the PT as the corresponding rectifier does [4,5]. The study uses the earlier generic analysis and generic characteristics of PT [6] together with the proposed comparative analysis of the two types of rectifiers for developing the generic model of PT AC/DC power converter.…”

Section: Introductionmentioning

confidence: 99%

A comparison of AC/DC piezoelectric transformer converters with current doubler and voltage doubler rectifiers

Ivensky

Bronstein

IEEE 34th Annual Conference on Power Electronics Specialist, 2003. PESC '03.

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Abstract.The objective of this study was to develop recommendations for an optimal design of PT AC/DC converters. The paper presents a comprehensive comparison of the two commonly used rectifier topologies in a piezoelectric transformer (PT) based power converters: current doubler and voltage doubler rectifiers. The advantages and disadvantages of the two rectifiers were investigated and the area of their applications with respect to output current, voltage, power capability, load resistance etc. -was delineated. Generic principles are proposed for choosing a PT for a given set of requirements, i.e. output voltage, input voltage and load resistance, as well the rectifier type suitable for the given PT and application. Simulation and experimental results support the theoretical study and are found to be in a good agreement with the analysis.