• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.196-198
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• 2007

본 논문에서는 가전 및 사무용 전원장치가 대기모드 상태에 있는 경우의 전력소모를 줄일 수 있는 PWM(Pulse Width Modulation) IC를 설계하였다. 설계된 PWM IC는 전원장치가 정상상태에서 동작하는 경우 전원장치 출력단에서 피드백 받은 신호의 크기에 따라 40 ~ 60kHz의 구동 주파수를 가지는 스위칭 소자 구동 신호를 내보내고, 대기모드 상태에서 동작하는 경우에는 최소 33KHz의 주파수를 가지는 신호를 내보내도록 설계되었다. 각각의 경우에 스위칭 소자 구동 신호의 듀티비는 정상상태인 경우에는 20 ~ 88%, 대기모드 상태인 경우에는 1%이내가 되도록 설계하였다. 시뮬레이션을 통해 검증한 결과 대기모드 상태에서 전원장치의 전력소모량은 0.2W 정도로 작게 나타남을 확인하였다.

• Journal of Power Electronics
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• v.10 no.5
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• pp.548-554
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• 2010

In this paper, a 1.5 kW Interior Permanent Magnet Synchronous Generator (IPMSG) with a power conditioner for the grid integration of a variable-speed wind turbine is developed. The power-conditioning system consists of a series-type 12-pulse diode rectifier powered by a phase shifting transformer and then cascaded to a PWM voltage source inverter. The PWM inverter is utilized to supply sinusoidal currents to the utility line by controlling the active and reactive current components in the q-d rotating reference frame. While the q-axis active current of the PWM inverter is regulated to follow an optimized active current reference so as to track the maximum power of the wind turbine. The d-axis reactive current can be adjusted to control the reactive power and voltage. In order to track the maximum power of the wind turbine, the optimal active current reference is determined by using a simple MPPT algorithm which requires only three sensors. Moreover, the phase angle of the utility voltage is detected using a simple electronic circuit consisting of both a zero-crossing voltage detecting circuit and a counter circuit employed with a crystal oscillator. At the generator terminals, a passive filter is designed not only to decrease the harmonic voltages and currents observed at the terminals of the IPMSG but also to improve the generator efficiency. The laboratory results indicate that the losses in the IPMSG can be effectively reduced by setting a passive filter at the generator terminals.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.135-135
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• 2015

Tubes are of extreme importance in industries as for fluid channels or wave guides. Furthermore, some weapon systems such as cannons use the tubes as gun barrels. To increase the service life of such tubes, a protective coating must be applied to the tubes' inner surface. However, the coating methods applicable to the inner surface of the tubes are very limited due to the geometrical restriction. A small-diameter cylindrical magnetron sputtering gun can be used to deposit coating layers on the inner surface of the large-bore tubes. However, for small-bore tubes with the inner diameter of one inch (~25 mm), the magnetron sputtering method can hardly be accommodated due to the space limitation for permanent magnet assembly. In this study, a new approach to coat the inner surface of small-bore tubes with the inside diameter of one inch was developed. Instead of using permanent magnets for magnetron operation, an external electro-magnet assembly was adopted around the tube to confine the plasma and to sustain the discharge. The electro-magnet was operated in pulse mode to provide the strong axial magnetic field for the magnetron operation, which was synchronized with the negative high-voltage pulse applied to the water-cooled coaxial sputtering target installed inside the tube. By moving the electro-magnet assembly along the tube's axial direction, the inner surface of the tube could be uniformly coated. The inner-surface coating system in this study used the tube itself as the vacuum chamber. The SS-304 tube's inner diameter was 22 mm and the length was ~1 m. A water-cooled Cu tube (sputtering target) of the outer diameter of 12 mm was installed inside of the SS tube (substrate) at the axial position. The 50 mm-long electro-magnet assembly was fed by a current pulse of 250 A at the frequency and pulse width of 100 Hz and 100 usec, respectively. The calculated axial magnetic field strength at the center was ~0.6 Tesla. The central Cu tube was synchronously driven by a HiPIMS power supply at the same frequency of 100 Hz as the electro-magnet and the applied pulse voltage was -1200 V with a pulse width of 500 usec. At 150 mTorr of Ar pressure, the Cu deposition rate of ~10 nm/min could be obtained. In this talk, a new method to sputter coat the inner surface of small-bore tubes would be presented and discussed, which might have broad industrial and military application areas.

• The Journal of the Korea Contents Association
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• v.10 no.2
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• pp.72-80
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• 2010

The 1Gbps clock and data recovery (CDR) circuit using the proposed multi-point phase detector (PD) is presented. The proposed phase detector generates up/down signals comparing 3-point that is data transition point and clock rising/falling edge. The conventional PD uses the pulse width modulation (PWM) that controls the voltage controlled oscillator (VCO) using the width of a pulse period's multiple. However, the proposed PD uses the pulse number modulation (PNM) that regulates the VCO with the number of half clock cycle pulse. Therefore the proposed PD can controls VCO preciously and reduces the jitter. The CDR circuit is tested using 1Gbps $2^{31}-1$ pseudo random bit sequence (PRBS) input data. The designed CDR circuit shows that is capable of recovering clock and data at rates of 1Gbps. The recovered clock jitter is 7.36ps at 1GHz and the total power consumption is about 12mW. The proposed circuit is implemented using a 0.18um CMOS process under 1.8V supply.

• Proceedings of the Korean Society of Medical Physics Conference
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• 2002.09a
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• pp.396-399
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• 2002

Intense quasi-monochromatic x-ray irradiation from the linear plasma target is described. The plasma x-ray generator employs a high-voltage power supply, a low-impedance coaxial transmission line, a high-voltage condenser with a capacity of about 200 nF, a turbo-molecular pump, a thyristor pulse generator as a trigger device, and a flash x-ray tube. The high-voltage main condenser is charged up to 55 kV by the power supply, and the electric charges in the condenser are discharged to the tube after triggering the cathode electrode. The x-ray tube is of a demountable triode that is connected to the turbo molecular pump with a pressure of approximately 1 mPa. As electron flows from the cathode electrode are roughly converged to the molybdenum target by the electric field in the tube, the weakly ionized plasma, which consists of metal ions and electrons, forms by the target evaporating. In the present work, the peak tube voltage was almost equal to the initial charging voltage of the main condenser, and the peak current was about 20 kA with a charging voltage of 55 kV. When the charging voltage was increased, the linear plasma x-ray source grew, and the characteristic x-ray intensities of K-series lines increased. The quite sharp lines such as hard x-ray lasers were clearly observed. The quasi-monochromatic radiography was performed by a new film-less computed radiography system.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.1043-1045
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• 2002

고전압 전원공급기를 고 밀도로 제작하기 위하여 고 주파수 동작을 시켜야 한다. 이에 따라 전원 공급기에서 최대의 부피를 차지하는 부품인 변압기는 원하는 주파수에서 최소의 부피로 충분한 전력을 수용하면서 완벽한 펄스재현을 하여야 한다. 고전압 전원공급기는 풀-브릿지 DC/DC 컨버트로 구성되어 있으며 스윗칭 주파수는 100 kHz 이다. 변압기는 일차권선이 1개이며 이차 권선은 4개로 구성된다 일차전압은 250 Vdc, 이차 권선 각각의 출력은 520 Vrms이다. 변압의 이차 권선은 배 전압 회로를 이용하여 승압 후 각각을 직렬로 연결하여 -4,100 VDC와 -2,050 VDC를 만들어 TWT(Travel Wave Tube)의 케소드 및 콜렉트에 공급한다. 이 변압기는 100 kHz 펄스로 동작하고 최대부피가 400$cm^3$이하가 되어야 한다. 본 논문에서는 이러한 변압기의 설계 방법 및 최소 온도상승을 위한 적절한 동작 자속밀도의 선택에 대하여 기술하고 변압기의 누설 인덕턴스, 분포 케페시턴스, 공진 주파수에 대하여 설계치 및 실험치를 비교 평가하였다.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.250-251
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• 2007

산업용 조사장치로 전자빔은 활용도가 매우 높고, 대부분의 장치는 국내에서 제작이 어려울 뿐만 아니라 외국의존도 높다. 현재 미국, 일본, 러시아, 캐나다 등을 중심으로 약 1500 기의 전자빔 조사 설비가 산업용 및 연구용으로 설치되어 있는데, 이 중 많은 설비가 공동이용 연구시설 또는 상업적인 전자빔 조사서비스 시설로 운영되고 있다. 산업적으로 이용하기 위하여 철원물리기술연구소에 설치될 전자빔 조사 시설을 위한 전자빔 가속기를 개발 중이다. 곡물 살충 및 발아억제, 식품 저장, 위생용품 살균, 의약품 및 의료용구 살균, 전력반도체 생산 등의 분야에 전자빔 조사 설비를 응용할 수 있다. 본 논문에서는 산업용 조사 설비의 전원장치로 사용되는 펄스 모듈레이터의 설계, 제작 및 실험내용을 보이고자 한다.

• Journal of Power Electronics
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• v.17 no.4
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• pp.1117-1126
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• 2017

The main contribution of this paper is the use of sensorless active diodes to generate the gate signals for a three-phase boost-rectifier with a self-powered control scheme. The sensorless operation is achieved making use of the gate control signals generated by the active diode schemes on each of the switching devices using a pulse width half-controlled boost rectifier modulation technique (PWM-HCBR). The proposed scheme synchronizes the gate control signals with a three phase voltage supply. Autonomous operation is obtained making use of the output DC bus to feed the control circuitry, the active diodes and the driver circuitry. The three-phase boost-rectifier is supplied by a three-phase permanent magnet electric generator powered by a solar concentrator dish with variable voltage and variable frequency conditions. Experimental results report an efficiency of up to 94.6% for 25 W and an input of 3.6 V peak per phase with 450.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.295-300
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• 2001

A variety of high voltage DC power supplies employing the high frequency inverter are difficult to achieve soft switching considering a quick response and no overshoot response under the wide load variation ranges which are used in medical-use x-ray high voltage generator from 20kV to 150kV in the output voltage and from 0.5mA to 1250mA, respectively. The authors develops soft switching high voltage DC power supply designed for x-ray power generator applications, which uses series resonant inverter circuit topology with a multistage voltage multiplier instead of a conventional high voltage diode rectifier connected to the second-side of a high-voltage transformer with a large turn ratio. A constant on-time dual mode frequency control scheme operating under a principle of zero-current soft switching commutation is described. Introducing the multistage voltage multiplier, the secondary transformer turn-numbers and stray capacitance of high-voltage transformer is effective to be greatly reduced. It is proved that the proposed high-voltage converter topology with dual mode frequency modulation mode control scheme is able to be the transient response and steady-state performance in high-voltage x-ray tube load. The effectiveness of this high voltage converter is evaluated and discussed on the basis of simulation analysis and observed data in experiment.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.11
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• pp.1239-1247
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• 2012

In this paper, design and fabrication of solid state power amplifier(SSPA) using GaN HEMT chip for X-band frequency are presented. The SSPA consists of the power supply for stable power and the control unit for communication and controlling the internal module, the RF Part to amplify RF signal, In particular the adopted active device for the RF Parts is GaN HEMT Bare chip of TriQuint company, the RF parts consists of pre-stage, drive-stage, main power-stage and each amplifier is designed with input and out matching circuit. The developed power amplifier demonstrated more than 300 W peak output power in condition of 26 % duty, max. pulse width 100us for the X-band frequency( 500 MHz bandwidth) and can apply to marine radar systems.