• Journal of the Optical Society of Korea
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• 제18권3호
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• pp.288-291
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• 2014

This paper presents a new method for measuring the half-wave voltage $V_{\pi}$ of an electro-optic phase modulator based on a phase-modulated photonic link with interferometric demodulation. By using this method, the $V_{\pi}$ can be obtained with the RF voltage amplitude input required to achieve 1-dB gain compression of link and the differential delay of a Mach-Zehnder interferometer. We measure the $V_{\pi}$ of a commercial phase modulator by using the presented method and the carrier/the first sideband intensity ratio method. Furthermore, we compare the two measurements with the typical value provided by the manufacturer. The experiment shows that this novel measurement method is feasible, straightforward, and accurate.

• Journal of Magnetics
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• 제16권3호
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• pp.246-252
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• 2011

A high-voltage power supply has been built for activation of the brain via stimulation using a Full Wave Cockroft-Walton Circuit (FWCW). A resonant half-bridge inverter was applied (with half plus/half minus DC voltage) through a bidirectional power transistor to a magnetic stimulation device with the capability of producing a variety of pulse forms. The energy obtained from the previous stage runs the transformer and FW-CW, and the current pulse coming from the pulse-forming circuit is transmitted to a stimulation coil device. In addition, the residual energy in each circuit will again generate stimulation pulses through the transformer. In particular, the bidirectional device modifies the control mode of the stimulation coil to which the current that exceeds the rated current is applied, consequently controlling the output voltage as a constant current mode. Since a serial resonant half-bridge has less switching loss and is able to reduce parasitic capacitance, a device, which can simultaneously change the charging voltage of the energy-storage condenser and the pulse repetition rate, could be implemented. Image processing of the brain activity was implemented using a graphical user interface (GUI) through a data mining technique (data mining) after measuring the vital signs separated from the frequencies of EEG and ECG spectra obtained from the pulse stimulation using a 90S8535 chip (AMTEL Corporation).

• KIEE International Transactions on Electrophysics and Applications
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• 제3C권4호
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• pp.123-129
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• 2003

We propose a high voltage dc-dc converter for a CW (continuous wave) $CO_2$ laser system using a current resonant half-bridge inverter and a Cockcroft-Walton circuit. This high voltage power supply includes a 2-stage voltage multiplier driven by a regulated half-bridge series resonant inverter. The inverter drives a step-up transformer and the secondary transformer is applied to the voltage multiplier. It is highly efficient because of the reduced amount of switching losses by virtue of the current resonant half-bridge inverter, and also due to the small size, low parasitic capacitance in the transformer stage owing to the low number of winding turns of the step up secondary transformer combined with the Cockroft-Walton circuit. We obtained a maximum laser output power of 44 W and a maximum system efficiency of over 16%.

• 한국통신학회논문지
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• 제17권2호
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• pp.142-152
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• 1992

본 논문에서는 광파이버 센서로써 고전계(고전압)측정의 어려움을 해결하기 위하여 지금까지 알려진 다른 전기광학 소자보다 반파장 전압이 매우 높은 SiO2를 사용하여 고전계을 계측하기 위한 새로운 방법을 제시 하였다. SiO2를 비롯한 광학소자로 구성된 센서내부, 즉 전광자 및 편광자에서의 광변조식을 Stokes Parameter와 Mueller 행렬로 유도 하였고 이를 복굴절 결정에서의 전기광학 효과를 이론적으로 해석하고 위상지연과 반파장 전압을 계산하였다. 설계 제작한 광전압 센서에 , 분압없이 최대전압 20KV까지 공급 했을때의 출력신호를 검출한 결과 오차는 3%미만으로서 매우 우수한 직선성을 얻었다. SiO2의 온도변화(-20~60$^{\circ}$C)에 따른 출력전압 변화를 실험한 결과 최대 7.5%까지 변동율이 발생하였으나 열처리 한후로는 1.0% 이내로 개선된 특성을 보였다.

• Journal of Power Electronics
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• 제17권6호
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• pp.1391-1401
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• 2017

In this paper, a secondary resonance half-bridge dc-dc converter with an inductive output filter is presented. The primary side of such a converter utilizes asymmetric pulse width modulation (APWM) to achieve zero-voltage switching (ZVS) of the switches, and clamps the voltage of the switch to the input voltage. In addition, zero current switching (ZCS) of the output diode is achieved by a half-wave rectifier circuit with a filter inductor and a resonant branch in the secondary side of the proposed converter. Thus, the switching losses and diode reverse-recovery losses are eliminated, and the performance of the converter can be improved. Furthermore, an inductive output filter exists in the converter reduce the output current ripple. The operational principle, performance analysis and design equation of this converter are given in this paper. The analysis results show that the output diode voltage stress is independent of the duty cycle, and that the voltage gain is almost linear, similar to that of the isolation Buck-type converter. Finally, a 200V~380V input, 24V/2A output experimental prototype is built to verify the theoretical analysis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1998년도 하계학술대회 논문집 F
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• pp.2088-2090
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• 1998

A low-cost electronic starter is developed to decrease ignition failure significantly through successive starting trial and to prevent overheating at the end of fluorescent lamp life. Moreover, it has an additional feature of being capable of ignition at the recovered lamp voltage without any circuit correction. The developed electronic starter is consisted of four parts - a half wave rectifier circuit, a timer circuit, a switching circuit and a protection circuit. The protection circuit made up of a transistor and capacitors utilizing capacitive characteristics, carries out successive starting trial and end-of-life protection. Lamp ignition is completed within 0.5 seconds with taking advantage of a high preheating current from the half-wave rectifier circuit. Nevertheless, its performance is proved to be very excellent through a standard switching endurance test.

• Journal of Information Display
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• 제9권4호
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• pp.1-5
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• 2008

This paper investigates the effect of the electrode edge of a patterned vertical alignment (PVA) liquid crystal (LC) device on the viewing angle characteristics. In general, a transmissive LCD applies an LC layer with half-wave retardation for a bright state and with zero retardation for a dark state. The retardation of the LC layer would be distorted in each point, however, when a voltage is applied because of the non-uniform voltage distribution in the electrode edge effect. In this paper, the feasibility of the full effect of the electrode edge on the viewing angle property is considered, and the optical viewing angles of the VA LCD with a uniform half-wave LC layer and the PVA LCD with a practical non-uniform LC layer are compared.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 B
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• pp.1327-1329
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• 2000

The thyristor among the power-semi-conductor elements, which has large current capacity and high voltage, is used widely nowadays. When the thyristor was being used to the long time, this element may be able to arise the system trip caused by changing the characteristic and dropping the performance. Therefore, it would be necessary to analyze the characteristic of element to maintain the stable operation of the system. In oder to analyze this characteristic, it would be need to test forward direction, reverse direction and leakage current by supplying the half-sine wave voltage. Among these testing, transient current condition is generated from the testing of leakage current. This transient current may be the main factor of the error in the precise measurement of leakage current. Therefore, this paper analyzes the relationship between supply voltage and transient current in measuring leakage current of the SCR, and then suggests the condition and cause of transient current as appearing the leakage current in the testing the leakage current.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 C
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• pp.1821-1823
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• 2003

We propose a high voltage dc-dc converter for CW(continuous wave) $CO_2$ laser system using a current resonant half-bridge inverter and a Cockcroft-Walton circuit. This high voltage power supply includes a 2-stage voltage multiplier driven by a regulated half-bridge series resonant inverter. The inverter drives a step-up transformer and the transformer secondary is applied to the voltage multiplier. Thus, it has high efficiency because of the less switching losses by virtue of the current resonant half-bridge inverter, and also compact size, small parasitic capacitance in the transformer stage owing to the low number of a winding turn of the step up transformer secondary by combining with Cockroft-Walton circuit. We could be obtained the maximum laser output power of 44 W and the maximum system efficiency of over 16 %.

• 전력전자학회논문지
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• 제9권1호
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• pp.10-16
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• 2004

본 논문에서는 공진 에너지 회생율을 최대화하여 전체적인 효율을 증가시킨 개선된 전파형 ZVT(Zero-Voltage-Transition) PWM(Pulse-Width-Modulation) DC-DC 컨버터를 소개한다. 개선된 회로는 단지 기존 컨버터의 보조스위치와 공진형 인덕터 사이에 직렬로 역공진 저지 다이오드를 추가로 달아서 모든 스위칭 소자들이 소프트 스위칭 조건에서 턴온/턴오프하여 스위칭 손실을 최소화하고, 공진 에너지를 완전히 입력으로 회귀시켜 전도손실을 절감하여 효율의 증감을 이루었다. 본 논문에서는 부스터 컨버터를 이용하여 개선된 컨버터의 동작을 분석하고, 실험결과를 바탕으로 제안된 회로의 타당성을 입증하였다.