• The Transactions of the Korean Institute of Electrical Engineers D
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• v.49 no.4
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• pp.175-182
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• 2000

The back-light inverter used in the laptop computer is designed in this paper. It has been difficult for electromagnetic transformer to enhance the efficiency and compact profile of the inverter. In this paper, (1) the piezoelectric transformer (PT) is used for reducing the loss; (2) the volumes of core and winding coil are used in electromagnetic transformer, and (3) the half-bridge series parallel resonant circuit is used in the driver of the inverter. The modified PT for this paper and the equivalent circuit are supported by the simulation program. The result of the experiment shows more than 91% improvement in terms of the efficiency.

• The Journal of the Acoustical Society of Korea
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• v.37 no.1
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• pp.46-52
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• 2018

The piezoelectric single crystals used in piezoelectric transformers have a problem that power transfer capacity is comparatively low due to their high input impedance. In this study, we suggest a method to improve the power transfer capacity by reducing the high input impedance of the piezoelectric single crystal vibrator by connecting a capacitance increasing circuit to the electrical terminals of the piezoelectric single crystal vibrator where the circuit is a GIC (Generalized Impedance Converter) circuit using operational amplifiers. The result of measuring driving characteristics after applying the designed capacitance increasing circuit to the $128^{\circ}$ rotated Y-cut $LiNbO_3$ crystal vibrator confirmed that the input impedance decreased by 25 %, electromechanical coupling factor increased by 30 %, and the power transfer capacity increased by about 17 to 30 times in voltage conversion characteristics.

• 정보저장시스템학회:학술대회논문집
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• 2005.10a
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• pp.235-240
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• 2005

In this paper, vibration suppression of a CD-ROM main base with piezoelectric shunt circuit is studied. Admittance is introduced to predict the performance of piezoelectric shunt damping. Numerical admittance obtained by commercial finite element code, ANSYS, correlates well with experimentally measured one. Multi-mode piezoelectric shunt damping is realized based on the target mode and frequencies obtained by the admittance analysis. Experimental results prove that admittance of the piezoelectric structure is capable of predicting the performance of piezoelectric shunt damping and the vibration of the main base with the piezoelectric patches is reduced effectively.

• Transactions of the Society of Information Storage Systems
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• v.2 no.1
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• pp.7-12
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• 2006

In this paper, vibration suppression of a CD-ROM main base with piezoelectric shunt circuit is studied. Admittance is introduced to predict the performance of piezoelectric shunt damping. Numerical admittance obtained by commercial finite element code, ANSYS, correlates well with experimentally measured one. Multi-mode piezoelectric shunt damping is realized based on the target mode and frequencies obtained by the admittance analysis. Experimental results prove that admittance of the piezoelectric structure is capable of predicting the performance of piezoelectric shunt damping and the vibration of the main base with the piezoelectric patches is reduced effectively.

• Journal of Power Electronics
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• v.3 no.2
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• pp.139-144
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• 2003

In this paper, 11 and 13 layered step-down piezoelectric transformers were fabricated and their electrical characteristics have been analyzed for AC-adapter. When the voltage is applied to the driving piezoelectric vibrator polarized in the longitudinal direction, the output voltage is generated at the generating piezoelectric vibrator polarized in the thickness direction due to the piezoelectric effects. From the piezoelectric direct and converse effects, symbolic expressions between the electric inputs and outputs of the step-down piezoelectric transformer are derived with an equivalent circuit model. With those expressions, load and frequency characteristics are discussed through the simulations. Output voltage and current from a 11-layered and a 13-layered piezoelectric transformers were measured under the different load and frequency conditions. First we measured resonant frequency from impedance curve and got equivalent impedance value of the piezoelectric transformer from admittance plot. It was shown from experiments that output voltage increase s and resonant frequency changes according to the various resistor loads. Output current decreases inversely proportional to the change of loads. Moreover, the measured output voltage and current are well matched with the simulated results obtained from the proposed equivalent circuit model. Furthermore, a new step-down piezoelectric transformer has been suggested to Increase the output power based on a simulation result having a driving piezoelectric vibrator polarized thickness direction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.216-221
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• 2002

In this paper, the transmitted noise reduction of smart panels of which passive piezoelectric shunt damping is used, is experimentally studied. Shunt damping experiments are based on the measured electrical impedance model. A passive shunt circuit composed of inductors, and a load resistor is devised to dissipate the maximum energy into the joule heat energy. For multi-mode shunt damping, the shunt circuit is redesigned by adding a blocking circuit. Also the optimal location of the piezoelectric patch is studied by FEM in order to cause the maximum admittance from the patch for each mode of aluminum plate. In results, the transmitted sound pressure level of panels is efficiently reduced for multi-modes

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.624-629
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• 2003

In this paper, broadband shunt technique for increasing transmission loss is experimentally investigated. Piezoelectric shunt damping is studied using resonant shunt circuit and negative capacitor shunt circuit. A resonant shunt circuit is implemented by using a resistor and inductor. Negative Capacitor shunt damping is similar in nature to resonant shunt damping techniques, as a single piezoelectric material is used to dampen multi-mode. Performance of both methods is experimentally studied for noise reduction. This is based upon SAE J1400 test method and a transmission loss measurement system is provided for it. This paper will present the test setup fer transmission loss measurement and the tuning procedure of shunt circuits. Finally the results of sound transmission tests will be shown.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.701-706
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• 2002

Typically, dimensions of the power circuit depend on magnetic components, heat sink, and smoothing capacitor, etc. For the miniaturization of the power circuit, one of the solutions is that bulky magnetic transformer in previously used is replaced by a piezoelectric transformer. Therefore, since many systems are attempted to apply the piezoelectric transformers, a new piezoelectric material is tending to be developed continuously. In this paper, an analysis of neon tube inverters with piezoelectric transformers are presented by Pspice modeling. Simulation results show that it is possible to apply a piezoelectric transformer to neon tube inverters with high conversion efficiency

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.5
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• pp.463-469
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• 2015

A vibration-based energy harvester and its equivalent circuit models have been reported. Most models predict voltage signals at harmonic excitation. However, vibrations in a natural environment are unpredictable in frequency and amplitude. In this paper, we propose a realistic equivalent circuit model of a frequency-up-converting impact-based piezoelectric energy harvester. It can describe the behavior of the harvester in a real environment where the frequency and the amplitude of the excitation vary arbitrarily. The simulation results of the model were compared with experimental data and showed good agreement. The proposed model can predict both the impact response and long term response in a non-harmonic excitation. The model is also very useful to analyze the performance of energy conversion circuitry with the harvester.

• JSTS:Journal of Semiconductor Technology and Science
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• v.15 no.3
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• pp.319-325
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• 2015

This paper presents an efficient vibration energy harvester with a piezoelectric (PE) cantilever. The proposed PE energy harvester increases the efficiency through minimization of hardware complexity and hence reduction of power dissipation of the circuit. Two key features of the proposed energy harvester are (i) incorporation synchronized switches with a simple control circuit, and (ii) a feed-forward buck converter with a simple control circuit. The chip was fabricated in $0.18{\mu}m$ CMOS processing technology, and the measured results indicate that the proposed rectifier achieves the efficiency of 77%. The core area of the chip is 0.2 mm2.