1,720,959 research outputs found
A New Control Method Using JFET for an Off-line Flyback Converter with Low Stand-by Power Consumption
No full textTo reduce stand-by power consumption in an off-line flyback converter, a number of control methods are used. This paper reviews the conventional method to reduce stand-by power in the off-line flyback converter. A new control method is proposed to reduce power consumption in an input filter part using a junction field effect transistor with maximum sampling period. The proposed control method has been implemented in 0.5μm BCDMOS technology. The validity of the proposed control method is verified by a prototype off-line flyback converter
Design of series input parallel output interleaved flyback converter for 75W AC-DC adapter
No full textIn this paper, a series input parallel output (SIPO) interleaved flyback converter for 75W AC-DC adapter is designed by three methods. To improve the efficiency of the SIPO interleaved flyback converter, discontinuous conduction mode (DCM) with valley switching technique is applied to reduce the switching loss at high line, and continuous conduction mode (CCM) is applied to reduce the conduction loss at low line. Since the input voltage is divided by the series input structure, the main switch can use the low voltage-rated switch. In addition, the small size of output-filter can be used by the interleaving operation. Therefore, the SIPO interleaved flyback converter with DCM at high line and CCM at low line, achieves high efficiency and high power density for the low-cost 75W (15V-5A) AC-DC laptop adapter application
Analysis and design of active clamp forward DC/DC converter with asymmetric two transformers
No full textConventional active clamp forward converter has narrow ZVS range of main switch. Although utilizing high magnetizing current can realize wide ZVS range, it increases the conduction loss. To solve this problem, an active clamp forward converter with asymmetric two transformers is proposed. The proposed converter has wide ZVS range without severe conduction loss by magnetizing current. It results in the proposed converter can achieve high frequency switching operation and high power conversion efficiency. The validity of the proposed converter is verified with 300W prototype converter
Design of Series Input Parallel Output Interleaved Flyback Converter for 75W AC-DC Adapter
No full textIn this paper, a series input parallel output (SIPO) interleaved flyback converter for 75W AC-DC adapter is designed by three methods. To improve the efficiency of the SIPO interleaved flyback converter, discontinuous conduction mode (DCM) with valley switching technique is applied to reduce the switching loss at high line, and continuous conduction mode (CCM) is applied to reduce the conduction loss at low line. Since the input voltage is divided by the series input structure, the main switch can use the low voltage-rated switch. In addition, the small size of output-filter can be used by the interleaving operation. Therefore, the SIPO interleaved flyback converter with DCM at high line and CCM at low line, achieves high efficiency and high power density for the low-cost 75W (15V-5A) AC-DC laptop adapter application
Analysis and design of wireless power transfer system with an intermediate coil for high efficiency
No full textThis paper presents a theoretical analysis, an optimal design method and experimental results for a wireless power transfer (WPT) system with an intermediate coil. The analytical expression of the DC voltage transfer function is presented and discussed. In a two coil WPT system, which has low coupling coefficient, the intermediate coil boosts the self-inductance and magnetizing inductance of the primary side at around the resonance frequency of the intermediate coil, so that the coupling coefficient is compensated. The coupling coefficient makes the system efficiency increase and induces bi-furcation phenomenon. From the analysis, this paper proposes an optimal design method using the second resonance frequency operation with the bi-furcation phenomenon and presents design procedure for high efficiency. A prototype of the WPT system with the intermediate coil is implemented and experimented to verify the validity of the analysis and the proposed design method. The prototype operates at 100 kHz switching frequency and has an air gap between primary and secondary side of 200mm. An overall system efficiency of 95.57% has been achieved at 6.6kW of output power
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A new high efficiency active clamp forward DC/DC converter with asymmetric two transformer
No full text학위논문(석사) - 한국과학기술원 : 전기및전자공학전공, 2007.2, [ iii, 51 p. ]반도체 기술이 계속 진보함에 따라 전자 기기들의 기능적 밀도가 점차 높아지고 있고 소형 경량화와 고효율화가 끊임없이 추구되어감에 따라 보다 낮은 전압에서 동작하는 새로운 논리 소자들이 등장하고 있다. 한 점에 위치한 하나의 중앙 전원 에서 각 지역에서 필요로 하는 모든 종류의 전원을 만들어 보내주는 형태의 종래의 중앙 집중형 전원 장치로는 점차 높아지는 전력요구와 낮은 전압 그리고 높은 효율과 높은 신뢰도를 만족시키기에는 어려움이 많다. 따라서 분산형 전원 장치에 대한 요구가 급증하고 있고 이에 대한 연구가 활발히 진행되고 있다. 통신용 분산 전원 시스템은 크게 AC/DC converter, front-end converter, on-board converter로 이루어져있다. 여기서 fornt-end 컨버터는 높은 DC 전압을 버스 전압으로 낮추는 컨버터이다. front-end 컨버터는 높은 효율이 요구되기 때문 에 만은 토폴로지가 연구 되어 왔다. 그중에서 능동 클램프 포워드 컨버터는 중간급 전원 시스템에 적용될 수 있다. 능동 클램프 포워드 컨버터는 간단한 구조 이지만 클램프 스위치의 영전압 스위칭(ZVS)가 잘 된다. 하지만 주 스위치의 ZVS는 잘 되지 않는다. 이로인해 스위칭 노이즈가 증가하고 효율이 감소하는 문제가 생긴다. 이런 문제를 해결하기 위해 본 논문은 두 개의 비대칭 변압기를 갖는 능동 클램프 포워드 컨버터를 제안한다.한국과학기술원 : 전기및전자공학전공
- …
