1,720,965 research outputs found
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
넓은 입력 범위를 가지는 LLC 공진형 컨버터의 공진 주파수 변경을 통한 효율 개선
No full text수명이 짧은 전해 캐패시터 대신 필름 캐패시터를 링크 캐패시터로 가지는 컨버터의 경우, 매우 넓은 입력 전압 범위를 가질 수 밖에 없다. 일반적인 넓은 입력 범위를 가지는 LLC 공진형 컨버터의 경우, 변압기 인덕터 값을 작게 하여 순환 전류가 커지도록 설계될 수 밖에 없고, 이는 LLC 공진형 컨버터의 더 큰 도통 손실 및 더 큰 turn-off 손실을 야기하여 LLC 공진형 컨버터의 변환 효율을 감소시키게 된다. 이를 개선하기 위하여 공진 인덕터에 보조 권선을 감고, 추가 스위치를 이용하여 입력 범위에 따라 공진 주파수를 변경할 수 있는 컨버터를 제안한다. 제안하는 컨버터는 LM값을 키워 정상 상태 시 도통 손실 및 turn-off 손실을 줄여 효율을 개선할 수 있으며, 낮은 입력 시 보조 스위치를 이용, fo변경을 통하여 추가적인 gain을 얻으면서 공진 인덕터의 철손을 줄여 넓은 입력 범위를 커버하면서 높은 변환 효율을 얻을 수 있다. 또한 제안하는 컨버터는 간단한 제어 방법과 낮은 전류 스펙을 가지는 작은 스위치를 사용할 수 있어 전력 밀도 증가를 최소화하면서 높은 효율을 가져갈 수 있다는 장점을 가진다
LLC resonant converter with high voltage gain using auxiliary LC resonant circuit
No full textTo design a LLC resonant converter optimally in the wide input voltage, the LLC resonant converter with a high voltage gain using an auxiliary LC resonant circuit is proposed. The auxiliary LC resonant circuit operates as a variable inductor, and it is represented as an effective magnetizing inductance combined with the magnetizing inductance. In the nominal state, the auxiliary LC circuit provides a high effective magnetizing inductance to minimize the primary circulating current for a high efficiency. During the hold-up time, the auxiliary LC circuit leads the effective magnetizing inductance to be reduced to obtain the high voltage gain. Therefore, an optimal design of the LLC resonant converter, which reduces the primary conduction loss and switching loss, is possible. The proposed converter is verified by experimental results with a 330–390V input 56V/350W output prototype
Analysis and design of Boost-LLC converter for high power density AC-DC adapter
No full textThis paper proposes the size reduction methods for two-stage Boost-LLC converter to achieve high power density in 60W AC-DC adapter. The two-stage converter has high component count, and the passive components such as inductor, transformer, and capacitor occupy the most of the area. In order to make the converter have small size, this paper proposes the size reduction methods of passive components: the design of low link voltage, the design of the resonant tank without additional inductor and with high resonant frequency, and the design of C-L-C filter replacing output capacitor. A 60W (16.8V/3.65A) prototype adapter is designed and implemented to verify the feasibility of the proposed methods. The converter achieves 14.5W/in3 power density with the methods
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
A digital leading phase current reduction (LPCR) technique for CCM boost PFC in light load conditions
No full textThis paper proposes a leading phase current reduction (LPCR) technique in a continuous conduction mode (CCM) boost power factor correction (PFC) for light load power factor (PF) improvement. The proposed LPCR technique provides the corrected average inductor current reference and the modified duty ratio feed-forward (MDFF) technique which can cancel the effect of the phase lead currents resulting from the EMI filter and input capacitor. Moreover, the proposed LPCR also provides the optimal dead-zone from the corrected current reference and MDFF. Therefore, the proposed LPCR can improve the power quality and efficiency not only in high AC line voltage range but also in extreme light load conditions. The principle and analysis of the proposed LPCR are presented, and the performance and feasibility are verified by experimental results from 230Vrms input and 750W–400V output laboratory prototype
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
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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