• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1204-1209
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• 2000

Many analytical and experimental studies on the active suppression of nonlinear panel flutter by using piezoceramic patch have been carried out. However, these active control methods have a few important problems; a large amount of power is required to operate actuators, and additional apparatuses such as sensor systems and controller are needed. In this study passive suppression schemes for nonlinear flutter of composite panel, which is believed to be more robust suppression system than active control in practical operation, are proposed by using piezoelectric inductor-resistor series shunt circuit. Toward the end, a finite element equation of motion for an electromechanically coupled system is proposed using the Hamilton's principle. To achieve the best damping effect, optimal shape and location of the piezoceramic(PZT) patches are determined by using genetic algorithms. The results clearly demonstrate that the passive damping scheme by using piezoelectric shunt circuit can effectively attenuate the flutter.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.263-266
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• 2002

In this paper, It is indicating that an issues of the conventional boost converter for high frequency induction heating. To improve those issues, it is proposed, simulated and analyzed that the current resonant circuit, simulated. As the result, we knew that the proposed circuit has a good point to improve the waveform of input current and to make high efficiency. On the other side, in the inverter for the high current power supply, it is proposed that the high frequency inverter of the half bridge topology, be done the circuit analysis to extract the optimal circuit parameter. It is making sure of the soft switching operating by the inductor to reverse parallel connected on the inverter main switch, decreasing the surge voltage when the switch is turn-off by compulsion, and repressing the switch current and bringing the high current amplitude operation by the multi resonance.

• Proceedings of the KOSOMBE Conference
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• v.1998 no.11
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• pp.165-166
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• 1998

A multi-parameter neuro muscular electrical simulator (NMES) system was developed to be used to find the optimal parameter condition in obtaining maximum muscle power and minimal fatigue. Since the performance of NMES is mainly determined by the characteristic of its output-stage circuit, we implemented 3 different circuits and compared output characteristics of them. Three amplifier circuits are; 1) a resonant switching converter, 2) a linear amplifier with a transformer, and 3) a step-up DC/DC converter with a high-voltage linear amplifier. Experimental results showed that the step up DC/DC converter with a high-voltage linear amplifier has the best performance.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.506-512
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• 1997

Ultrasonic knives have been successfully used for the surgery of many medical fields. However, the conventional ultrasonic knives for surgical operation cannot be controlled its resonant frequency. So if the material to cut has different characteristic impedance then different ultrasonic knife will be needed. Because the optimum driving frequency of ultrasonic knife is different by characteristic impedance of material. In this work, using a frequency variable ultrasonic transducer made of multi-layered PZT vibrator, a frequency controllable ultrasonic knife will be suggested. The design and computation principles will be also derived. For this work, firstly, the characteristics of this ultrasonic knife will be analyzed by transmission line model equivalent circuit, and the free admittance characteristics and vibrational velocity distributions will be obtained. Secondly, we will design and make the frequency controllable electrical oscillator for driving this ultrasonic knife.

• Proceedings of the KIEE Conference
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• 2006.10d
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• pp.125-128
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• 2006

This paper presents a novel type soft switching PWM power frequency AC-AC converter using bidirectional active switches or single phase utility frequency AC-high frequency AC matrix converter. This converter can directly convert utility frequency AC (UFAC, 50Hz/60Hz) power to high frequency AC (HFAC) power ranging more than 20kHz up to 100kHz. A novel soft switching PWM prototype of high frequency multi-resonant PWM controlled UFAC-HFAC matrix converter using antiparallel one-chip reverse blocking IGBTs manufactured by IXYS corp. is based on the soft switching resonance with asymmetrical duty cycle PWM strategy. This single phase UFAC-HFAC matrix converter has some remarkable features as electrolytic capacitor DC busline linkless topology, unity power factor correction and sine-wave line current shaping, simple configuration with minimum circuit components, high efficiency and downsizing. This series load resonant UFAC-HFAC matrix converter, incorporating bidirectional active power switches is developed and implemented for high efficiency consumer induction heated food cooking appliances in home uses and business-uses. Its operating performances as soft switching operating ranges and high frequency effective power regulation characteristics are illustrated and discussed on the basis of simulation and experimental results.

• Journal of Power Electronics
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• v.11 no.4
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• pp.591-598
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• 2011

This paper investigates a power supply of medium voltage with enhanced ignition characteristics for plasma torches. A series resonant half-bridge topology is presented as a suitable ignition circuitry. The ignition circuitry is integrated into the main power conversion system of a multi-phase staggered three-level dc-dc converter with a diode front-end rectifier. A plasma torch rated at 3MW, 2kA and having a physical size of 1m is selected to be the high enthalpy source for a waste disposal system. The steady-state and transient operations of a plasma torch are simulated. The parameters of a Cassie-Mary arc model are calculated based on 3D magneto-hydrodynamic simulations. The circuit simulation waveform shows that the ripple of the arc current can be maintained within ${\pm}10%$ of its rated value under the presence of a load disturbance. This power conversion configuration provides a high enough ignition voltage, around 5KA, during the ignition phase and high arc stability under the existence of arc disturbance noise resulting in a high-performance plasma torch system.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.1
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• pp.36-43
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• 2017

This paper describes a hybrid multi-output three-level DC/DC converter suitable for a wide, high-input voltage range of an auxiliary power supply for a high-power photovoltaic generating system. In a high-power photovoltaic generating system, the solar panel output voltage depends on solar radiation quantity and varies from 450Vdc to 1100Vdc. The proposed hybrid multi-output three-level DC/DC converter, which is an auxiliary power supply, would be used as power source for control printed circuit boards and relay and cooling fans in a high-power photovoltaic generating system. The proposed multi-output ($24V_{DC}/30A$, $230V_{DC}/5A$) hybrid three-level boost converter, which uses an energy recovery snubber, is controlled by variable-frequency and phase-shifted modulations and can achieve zero-voltage switching with all operating conditions of input voltage and load range. Experimental results of a 2kW prototype are evaluated and implemented to verify the performance of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.6
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• pp.560-568
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• 2005

The proposed Multi-level PDP sustain Driver is composed of the semiconductor devices with low voltage rating compared to those used in the prior circuit proposed by L. Wether, and it has two resonant periods during the charging (rising period) and discharging (falling period) the PDP in the sustaining voltage waveforms. In accordance with the change of timing phase$(T_{r1},\;T_{i1},\;T_{r2})$, the performance characteristics of a commercial PDP module has been carried out and compared the characteristic with the 42V6, made of LG Electronics co., Experimental results show that the performance characteristics of PDP module are greatly influenced by the variation of $T_{i1}\;and\;T_{r2}$. The variation of $T_{r1}$ do not influence much on the performances of PDP. With the conditions that $T_{r1}=60ns,\;T_{i1}=120ns,\;and\;T_{r2}=350ns$, we could get the performances listed as the luminance is increased $14.6\%$, the power consumptions is decreased $5.9\%$, the panel efficiency is increased $24.2\%$, module efficiency is increased $21.2\%$, compared to those shown in the commercial PDP module (42V6). Therefore, the proposed multi-level PDP sustain driver expected to be suitable to actual PDP module application.

• The Journal of the Acoustical Society of Korea
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• v.14 no.4
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• pp.29-37
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• 1995

A resonant frequency of piezoelectric transducer depends remarkably on the electric impedance connected to the vibrator. In this paper, using this effect of frequency controllable two layered PZT ultrasonic transducer is designed and its acoustic characteristics are analyzed by a new transmission model equivalent circuit. The theoretical and the experimental results of the electric impedance effect on the resonant frequency variation were compared and both results showed a good consistency each other. The resonant frequency has been controlled continuously in the wide frequency range of 180kHz~580kHz and the effective attenuations were less than 7dB in the frequency range of 330kHz~470kHz.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.38B no.9
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• pp.715-721
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• 2013

Minimization techniques are adaptations of Helical structure, Meta material, multi-layer structure etc. But, Helical structure is not suited to minimization technique of RF circuit having single resonant frequency. Because it generate resonant frequency following as rotation of circumference. Meta material and multi layer structure have weakness of expenditure and complex structure. In addition, conventional three dimensional M$\ddot{o}$bius Strip and planar M$\ddot{o}$bius Strip are not two dimensional planar M$\ddot{o}$bius Strip that has weakness of electrical coupling effect. Therefore, in this paper, we proposed miniaturized and reduced electrical coupling effect antenna by adaptation of Quasi M$\ddot{o}$bius Strip that topology is same as three dimensional M$\ddot{o}$bius Strip with Via-Hole structure. According to the simulation result, physical circumferential length is 1/3 minimized compared with conventional ring antenna under the same resonant frequency. In addition, coupling effect is not nearly generates near to the resonant frequency, 2.4GHz.