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고효율 DC/DC컨버터 제작을 위한 동기정류기 도전 손실 해석
윤석호,김용,백수현,김필수 동국대학교 산업기술연구원 1999 산업기술논문집 Vol.14 No.-
최근 반도체 소자의 제조기술 발달로 정보통신기기 등에 사용되는 온보드(on-board) 컨버터의 전원전압은 3.3V 또는 1.5V의 저전압 전원이 사용된다. 이러한 저전압 전원방식은 온보드(on-board) 컨버터의 정류기단 전력손실이 증가하게 되어 시스템의 높은 효율을 얻기가 어렵게 된다. 낮은 전원전압 방식일수록 정류기단에서 전력손실은 더욱 증가하여 컨버터의 효율은 낮아진다. 고전력밀도의 정류기단 구성을 위하여 출력단에 다이오드 대신 MOSFET 자기구동 정류기를 사용한다. 그러나 MOSFET 자기구동 정류기의 전력손실은 2차측 구동전압의 형태나 기생인덕턴스의 영향을 받게 된다. 따라서 불연속에서는 기생인덕턴스에 의한 MOSFET와 쇼트키 다이오드의 도통주기의 변화가 MOSFET 자기구동 정류기의 전력손실에 미치는 영향을 분석하였으며, 그 결과 기생인덕턴스의 크기를 감소시켜 MOSFET의 도통주기를 증가시킴으로써 MOSFET 자기구동 정류기의 전력손실을 최소화하였다. Recently, new trend in telecommunication device is to apply low voltage, about 3.3V-1.5V. However, it is undesirable in view of high efficiency and power desity which is the most important requirement in the distributed power system. Rectification loss in the output stage in on-board converter for distributed power system are constrained to obtain high efficience at low output voltage power supplies. This paper is investigated conduction power loss in synchronous rectifier with a parallel connected Schottky Barrier Diode(SBD). Conduction losses are calculated for both MOSFET and SBD respectively. The SBD conduction power loss dissipates more than the MOSFET rectifier conduction power loss.
동기정류방식에 의한 하프브리지 컨버터의 효율개선에 관한 연구
김용,고승모,백락준,김필수,윤석호 東國大學校 1999 東國論叢 Vol.38 No.-
The effort to increase operating frequency in order to reduce weight, size and coast of magnetic and filter elements is constantly hampered by higher switching stresses and switching losses. And the evolution in the digital integrated circuits in demanding lower power supply voltage. In a few years, 3.3V may be standard. In converters with such a low output voltage, it is quite difficult to achieve high efficiency due to the rectifier diodes of the output stage what limits the reduction converter size. To over come theses obstacles, this paper proposes the ZVS Half-Bridge converter using Self-driven Synchronous Rectifier. Using resonant condition of the transformer primary side series equivalent inductance and parasitic capactiance of the switching device, the circuit operates in zero-voltage switching. The steady state equation and ZVS condition are derived. The Zero Voltage Switching is analyzed taking into account the effect of the parasitic capacitance of the MOSFET rectifiers on the transformer secondary side. The Zero voltage Switching condition is established. Simulation and experimental result are compared.
The Temperature Sensitivity of the Commercial Load in KOREA
Yoon, Yong-Beum,Kang, Dong-Phil,Yoon, Yong-Tae 대한전기학회 2013 The Journal of International Council on Electrical Vol.3 No.2
This paper presents the temperature impacts on daily peak load of commercial load in KOREA. This research focuses on the overall summer and winter peak load characteristics and the impact of temperature change on the commercial load. Load data of the last five years are used to analyze the temperature sensitivity of commercial load sensitivity.
금강 중류 구석기 유적의 제4기 지질 환경과 층서 고찰
김주용(Kim, Ju-Yong),양동윤(Yang, Dong-Yoon),이융조(Lee, Yung-jo),우종윤(Woo, Jong-yoon),홍세선(Hong, Se-Sun),이상헌(Yi, Sangheon),남욱현(Nahm, Wook-Hyun),이진영(Lee, Jin-Young),봉필윤(Bong, Phil-Yoon ),오근창(Oh, Keun-Chang),이승원( 한국구석기학회 2015 한국구석기학보 Vol.- No.32
금강 중류 유역의 하안단구 상면에서 사면프로세스와 연동된 여러 매의 사니질 고토양층은 구석기 인류의 삶의 증거가 포함되어 있다. 특히 청주 관내 오송 만수리, 옥산 소로리, 현도 노산리-하석리 일대 하안단구는 저위 I면(제2단구) 위에 하성퇴적층이 널리 발달하여 있다. 금강 중류 하안단구는 해발고도 약 30m 아래에 분포하는 하성 사력층은 전반적으로 최종빙기 초(약 60ka) 이후에 형성된 것으로 해석된다. 본 연구에서 검토한 3개 구석기 유적 지점에 나타나는 고토양층 형성은 만수리에서 약 45ka 이후(1지점 Q 28), 소로리에서 약 43ka 이후 (H-15 시추코아), 그리고 노산리에서 약 37ka(3지점 F5)~43ka(2지점 B-1)로 각각 나타나, 전반적으로 고토 양층의 형성은 플라이스토세 말 중에서도 주로 최종빙기 중기와 후기(MIS 3~2) 걸치는 것으로 해석되었다. 소로리에서 신기 하성퇴적층이 최종빙기최성기(MIS 2) 이후 뵐링-알러뢰드 간빙기에 걸쳐 형성되었다. 금강 중류의 3개 구석기 유적발굴 지점 토층단면의 고토양층에서 환경변화와 주기성에 대한 예비 결과, 대자율은 농갈 색이나 적갈색 고토양층 구간에서 증가하며, 갈색~암갈색 고토양층 구간에서는 상대적으로 낮아 지는 경향을 보이며, 대자율 상승 구간에서는 일반적으로 실트 함량이 증가(40~50 % 이상)함과 동시에 사질 함량은 감소 (20~30 이하)하는 경향을 강하게 지시하고 있다. 오송 만수리 1지점 대표단면(Q28칸)의 대자율 분포를 보면, 약 65,000년전 이후 약 만년주기의 하인리히 이벤트(H5~H3) 주기가 나타나는 것으로 간주되며, 금강 유역의 다른 구석기 유적에서도 나타나는지 추가 검토가 필요하다. A number of Paleosols, which contain relicts of the paleolithic peoples, are associated with slope-processed deposits on the fluvial terrace along the middle part of Keum River Basin, where Low Terrace-I(or 2nd Terrace) is prevailed with sand and gravel deposits, particularly at Mansuri(Osong-myeon), Sorori(Ogsan-myeon), and NosanriHaseogri(Hyeondo-myeon) in Cheongju City. Fluvial terrace deposits in middle part of Keum River are distributed below ca 30 m(asl) and interpreted to be formed after 60ka. Formation ages of paleosols of three paleolithic sites in this research are converged into the range between the MIS 2~MIS3 during the Last Glacial(Upper Pleistocene); Paleosols of Mansuri initially formed in the range of 45ka(Q28 pit in Loc. 1), Paleosols of Sorori formed after 43.6ka(H-15 core), and Paleosols of Nosanri after 37ka(F5 in Loc. 3). In Sorori site Young Fluvial Sequence(YFS) formed during the BøllingAllerød Interstadial after the Last Glacial Maximum(LGM). It can be manifested from the preliminary results of the soil-sedimentary profiles of three paleolithic sites that MS increases in reddish brown and dense brown Paleosols, while it decrease relatively in brown or dark brown Paleosols; MS increase is associated with both increasing silt fraction(> 40~50 wt %) and decreasing sand fraction(>20~30 wt %) in general. Lastly although it regards that the cyclicity of low MS peaks in the representative vertical profile(Q28) of Mansuri Loc. I site may be associated with the worldwide Heinrich events(H4~H6), it may be further examined from the other Paleosol profiles among the Paleolithic sites in the Keum River Basin.
Phil Kyu Lee,Jae Lim Chung,Da Ran Kim,Young Chae Yoon,SoonWon Yang,Woong-Joo Whang,Yong-Soo Byun,HyungBin Hwang,Kyung Sun Na,HyunSoo Lee,So Hyang Chung,Eun Chul Kim,YangKyung Cho,Hyun Seung Kim,Ho Sik 대한안과학회 2024 Korean Journal of Ophthalmology Vol.38 No.1
Purpose: In the present study, we determined the prevalence of obstructive meibomian gland dysfunction (MGD), hyposecretory MGD, grossly normal MG, and hypersecretory MGD in patients with dry eye syndrome using lipid layer thickness (LLT) and MG dropout. Methods: Eighty-eight patients with dry eye syndrome were included in the study. Patients were categorized into four groups according to the LLT and weighted total meiboscore. The proportion of patients in each group was calculated. The age, sex, Ocular Surface Disease Index, LLT, Schirmer, tear film breakup time, cornea stain, weighted total meiboscore, expressibility, and quality of meibum were compared between the four groups. Results: Fifteen eyes (17.0%) had obstructive MGD, two eyes (2.3%) had hyposecretory MGD, 40 eyes (45.5%) had grossly normal MG, and 17 eyes (19.3%) had hypersecretory MGD. The obstructive MGD group was younger than the grossly normal MG group. In obstructive MGD, the ratio of men to women was higher than that of the other groups. However, Ocular Surface Disease Index, Schirmer, tear film breakup time, and corneal stain did not show statistically significant differences between the four groups. The meibum expressibility of the hyposecretoy MGD group was worse than those of the other groups. The meibum expressibility of the hyposecretoy MGD group was poor than those of the obstructive and hypersecretory MGD group. Conclusions: This categorization was expected to help determine the best treatment method for dry eye syndrome, according to the MG status.
Case Report : A Case of Membranous Lipodystrophy Observed in Lichen Amyloidosis
Yoon Hee Lee,Seok Yong Ahn,Jae Hong Ji,Seung Phil Hong,Ha Na Bak,Sang Hoon Lee,Sung Ku Ahn 대한피부과학회 2009 Annals of Dermatology Vol.21 No.2
Membranous lipodystrophy is characterized by the presence of microcysts lined by amorphous, eosinophilic material with an arabesque appearance. We experienced a case of a 72-year-old man who had dark brownish, pruritic papules on the arms, legs, and back. Histopathologic examination of a biopsied lesion showed homogeneous, eosinophilic material in the papillary dermis, as well as membranous lipodystrophy. We report a case of membranous lipodystrophy observed in lichen amyloidosis. (Ann Dermatol 21(2) 174~177, 2009)