• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 하계학술대회 논문집 C
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• pp.2089-2091
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• 2000

Pulsed power systems consist of a capacitor bank, an isolated high-voltage charging power-supply, high-current bus-work for charging and discharging and a control system. In such pulsed power systems, the operating-lifetime of the capacitors is closely dependent on the voltage reversal. Hence, most capacitor-discharging systems includes crowbar circuits. The crowbar circuit prevents the capacitor recharging with reverse voltage. Usually it consists of crowbar resistors and high pulse-current diode-stacks connected in series. The requirements for the diode-stacks are fast-recovery time and high-voltage and large-current ratings, which results in the high cost of the pulsed-power system. This paper presents a protection scheme of a charging and discharging system of a 500kJ capacitor bank using a low-cost crowbar circuit and safety-fuses.

• 한국재료학회지
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• 제29권7호
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• pp.456-462
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• 2019

ZnO thin-films are grown on a p-Si(111) substrate by RF sputtering. The effects of growth temperature and $O_2$ mixture ratio on the ZnO films are investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), and room-temperature photoluminescence (PL) measurements. All the grown ZnO thin films show a strong preferred orientation along the c-axis, with an intense ultraviolet emission centered at 377 nm. However, when $O_2$ is mixed with the sputtering gas, the half width at half maximum (FWHM) of the XRD peak increases and the deep-level defect-related emission PL band becomes pronounced. In addition, an n-ZnO/p-Si heterojunction diode is fabricated by photolithographic processes and characterized using its current-voltage (I-V) characteristic curve and photoresponsivity. The fabricated n-ZnO/p-Si heterojunction diode exhibits typical rectifying I-V characteristics, with turn-on voltage of about 1.1 V and ideality factor of 1.7. The ratio of current density at ${\pm}3V$ of the reverse and forward bias voltage is about $5.8{\times}10^3$, which demonstrates the switching performance of the fabricated diode. The photoresponse of the diode under illumination of chopped with 40 Hz white light source shows fast response time and recovery time of 0.5 msec and 0.4 msec, respectively.

• 전력전자학회논문지
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• 제4권4호
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• pp.377-383
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• 1999

종래의 충전기 및 통신용 전원장치에 있어서 입력 역률을 개선시키기 위해 고 역률 컨버터(Power Factor Correction Circuit)가 제안되어 적용되고 있고, 이들 대부분 회로는 Hard Switching을 이용한 정류회로로, 입력역률 1제어와 입력전류를 정현파형을 만들 수 있지만 Switching Noise에 의한 전자파장해(EMI)와 스위칭손실 등의 문제를 안고 있다. 또한, 절연된 DC 출력전압을 얻기 위해서는 고 역률 컨버터 후단에 절연된 DC/DC 컨버터가 적용되어야 함으로써, 주 회로 및 제어회로가 다단으로 구성되는 등 복잡화되는 단점이 있었다. 본 논문에서는 이러한 단점을 극복하기 위해 역률보정회로(PFC)를 갖는 절연된 Single Stage 무손실 스너버적용 고주파 소프트 스위칭 컨버터를 제안하고자 한다.

• Journal of Power Electronics
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• 제11권2호
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• pp.188-193
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• 2011

A highly efficient AC-DC converter for small wind power generation systems using a brushless DC generator (BLDCG) is presented in this paper. The market standard AC-DC converter for a BLDCG consists of a three-phase diode rectifier and a boost DC-DC converter, which has an IGBT and a fast recovery diode (FRD). This kind of two-stage solution basically suffers from a large amount of conduction loss and the efficiency greatly decreases under a light load, or at a low current, because of the switching devices with a P-N junction. In order to overcome this low efficiency, especially at a low current, a three-phase bridgcless converter consisting of three upper side FRDs and three lower side Super Junction FETs is presented. In the overall operating speed region, including the cut-in speed, the efficiency of the proposed converter is improved by up to 99%. Such a remarkable result is validated and compared with conventional solutions by calculating the power loss based on I-V curves and the switching loss data of the adopted commercial switches and the current waveforms obtained through PSIM simulations.

• 조명전기설비학회논문지
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• 제25권6호
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• pp.9-17
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• 2011

The high-power LED (Light Emitting Diode) which is recently gaining popularity as a digital light source has such advantages as low power consumption, long life, fast switching speed, and high efficiency. Thus, many efforts are being made to use the high-power LEDs for general lighting. This paper proposes LED driving circuit uses a DC/DC converter that can recover energy to compensate for the current variations caused by changes in LED equivalent resistance following a temperature change instead of serial resistance. The maximum input voltage of this DC/DC converter has low voltage variations by temperature change when the rated current is formed. In order to return current to the input side, we need a high boosting at low power. Thus, to improve the low efficiency of power converter, the power converter can be configured in such a way to gather the powers of low-capacity DC/DC converters and return the total power. Experiments showed that the proposed system improved efficiency compared to the conventional LED drive using the existing DC/DC converter.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1996년도 하계학술대회 논문집 A
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• pp.388-391
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• 1996

The conventional high frequency phase-shifted full bridge DC-DC converter has a disadavantage that a circulating current flows through transformer and switching devices during the freewheeling interval Due to this circulating current, RMS current stress, conduction losses of transformer and switching devices are increased. To alleviate this problem, this study provides a novel circulating current free type high frequency soft switching phase-shifted full bridge DC-DC converter which applies the energy recovery snubber(ERS) attached at the secondary side of transformer. The ERS adopted in this study is consisted of three fast recovery diode($Ds_1$, $Ds_2$, $Ds_3$), two resonant capacitor($Cs_1$, $Cs_2$) and a small resonant inductor [(Lr) : It can be ignored because the transformer leakage inductance(Ll) is able to use in stead of inserting the resonant inductor(Lr)]

• 연구논문집
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• 통권33호
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• pp.81-88
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• 2003

A metal jet printing system based on ink jet printing technique is one of the effective equipments for manufacturing elements of display devices, electrical devices, information processing systems, and so on. In order to develop an actuator of the metal jet printing system, bimorph type PZT actuator(length 25.2mm, width 7.2mm, thickness 0.5mm, shim thickness 0.2mm) and its controller(voltage range $\pm24v$, built-in fast recovery diode) were suggested and investigated. Performance tests and characteristic analysis, such as displacement, force, hysteresis and frequency, were carried out. The results show that the suggested actuator and controller are suitable for the metal jet printing system.

• 조명전기설비학회논문지
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• 제23권5호
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• pp.1-8
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• 2009

자동차의 자동변속기에는 변속을 하기 위한 솔레노이드 밸브가 장착되어 있으며, 이 솔레노이드 밸브는 자동변속기의 고장 원인 중 상당부분을 차지하므로 이 밸브를 세척하기 위하여 솔레노이드 밸브 세척기를 사용한다. 그러나 현재 사용되고 있는 세척기는 슬러지를 제거하는 효과가 적고 세척 속도가 느린 단점을 가지고 있다. 본 논문에서는 솔레노이드 오프시에 잔류전류를 신속하게 제거하여 플런저의 동작속도를 증가시킴으로써 세척력을 증가시키고 세척 속도를 빠르게 하는 방법을 제안하였으며, 그 성능을 실험을 통해 증명하였다.

• 한국식품위생안전성학회지
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• 제38권5호
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• pp.390-401
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• 2023

본 연구에서는 기존 식품첨가물 분석법에서 합으로써 분석되는 락색소를 laccaic acid A, B, C, E 4가지 성분으로 분류하고 개별적으로 정량 할 수 있는 분석법을 확립하였다. Natural red 25를 사용하여 구조적으로 비슷한 laccaic acid A와 B를 1차적으로 분취한 후 2차로 A와 B를 분리했다. 같은 방식으로 C와 D를 1차, 2차에 걸쳐 각각의 개별 표준품으로 사용하였다. 락색소 불검출 시료 3가지 시료(햄, 토마토 주스, 고추장)를 확보하여 0.05-107.2 ㎍/mL 범위에서 결정계수(r²) 0.995 이상의 직선성을 확인하였다. 3가지 시료에서 정밀도와 정확성을 측정한 결과, 일내 정밀도는 0.2-12.3%, 정확도는 90.6-112.7% 범위 내에서 확인되었으며 일간 정밀도는 0.3-13.3%, 정확도는 90.3-113.0% 범위내로 확인 되었다. 락색소를 사용하는 식품과 사용 금지 식품에 대해 회수율을 측정한 결과, 사용 가능 식품에서는 91.6-114.9% 범위의 회수율을 보였으며, 사용 불가 식품의 경우 92.5-113.5% 범위의 회수율을 보였다. 락색소의 검출 한계는 3가지 시료에서 검출한계 0.01-0.15 ㎍/mL, 정량한계 0.02-0.47 ㎍/mL로 확인되었다. 락색소의 4가지 성분중 laccaic acid A와 C에 대한 측정 불확도를 산출한 결과, laccaic acid A의 측정 불확도는 13.65±0.39 mg/kg(신뢰수준 95%, K=2), laccaic acid C의 측정 불확도는 4.19±0.39 mg/kg(신뢰수준 95%, K=2)로 비교적 낮은 측정불확도 값을 산출하였다. 따라서 본 연구에서는 식품 중 락색소의 개별 분석과 정성 및 정량분석을 위해 유효성이 검증된 분석법을 확립으로 식품 중 잔류물질 기준규격 설정 및 관리에 참고 자료가 될 수 있고, 향후 매트릭스 효과에 따른 laccaic acid 개별 분석과 개별 활성 및 독성시험 연구의 근거 지표가 될 수 있다고 판단된다.