1,720,981 research outputs found
High efficiency, low power IC step-down controller for ultra-low power applications
No full textNowadays the evolution of Smart Technology has led to an increasing need for efficient power management systems, especially for low power and wearable applications. In such architectures, in order to minimize power consumption and achieve higher efficiency, switching regulators for power management are almost mandatory. When dealing with ultra-low power applications (average load current of hundreds of μA), the main source of losses is the control system itself, so the main challenge is to minimize the steady-current consumption for the entire control system and adapt it with load conditions.In this paper a novel control architecture principle that maximizes efficiency is proposed, and the whole system and its sub-parts are described in detail. Its main feature is an extremely low bias current (tens of nA), with an operating power consumption that is frequency-dependent; whilst high-side switch on-time is kept almost constant, system frequency is adapted with load requirements, obtaining thus a controller consumption that is proportional with load demands
A novel wireless charging technique for low-power devices based on Wiegand transducer
No full textDuring last decade biomedical devices have become more and more performing, covering an increasing number of usages. In particular, subcutaneous devices represent one the most invasive yet innovative application; their battery management is one of the most challenging topics because, once implanted, they can be handled only through surgery, so wireless charge is the only way to feed subcutaneous systems with appreciable energy in a controlled manner. But differently from conventional consumer devices, in this scenario the energy delivered necessarily runs into human body and tissues, so the main challenge consists in maximizing the "energy delivered vs. energy dissipated in tissues" ratio, in order to guarantee human safety first while also conveying an appreciable amount of energy to the implanted device After analysing the state-of-the-art of the principal techniques, this paper proposes a novel architecture for low-power wireless charging, based on a Wiegand sensor used as a transducer in order to fulfill all the requirements from both electrical and medical points of view; such architecture is implemented inside an IC prototype in 0.35 μm lithography that acts as an ultra-low-power DC-DC buck converter and battery manager
Analysis of the micro-voids fraction in structural steels and its evolution during plastic deformation until failure
Full text linkIn this work the results of an experimental analysis performed on different steels of commercial use having different microstructure and yield value are reported. The materials were characterized by performing tensile and torsion tests, bringing the material up to rupture. The specimens were extracted according to different orientations to verify the influence of anisotropy on the size and distribution of micro-voids present in the broken material. After the mechanical tests, an analysis was made of the amount of micro-voids present in the original, not deformed material and in the deformed material until failure. The results obtained show that for all the analyzed steels the initial fraction of micro-voids is negligible, and no growth or formation of further voids is observed as the applied plastic deformation increases, even for strain values close to rupture
48 v input rad-hard DCDC converters for HEP experiments: Development and results
No full textTwo new radiation-hard DCDC converters are in development, which tolerate a higher input voltage (up to 48 V) and provide a larger output power compared to existing solutions. They are called bPOL48V and rPOL48V, and they employ gallium nitride devices. bPOL48V can provide 10 A of output current with better than 90% efficiency and is close to production readiness, while rPOL48V is in an early stage of development and is designed to provide larger output current with better power density. A linear regulator called linPOL48V, able step down the voltage from up to 48 V with maximum output current of 200 mA has also been designed and tested
Multi-Frequency Trans-Inductor Voltage Regulator
No full textThe cloud computing revolution has led to a rapid increase in data center electricity consumption. Low-profile, high-density server boards are needed to efficiently step down the input distribution bus to the digital rails as power demands rise. Intermediate Bus Converters (IBCs) typically use soft-switching resonant topologies like non-regulated LLCs, while the core voltage is regulated using a multiphase buck VRM. A classic VRM must guarantee digital load regulation and represent the least efficient element of the energy distribution chain. High transient performances require high switching frequencies, which decrease the efficiency of the VRM. This paper describes a multi-frequency conversion system based on a trans-inductor structure for multiphase voltage regulator modules (VRM) to obtain a higher efficiency without affecting transient performances. Experimental results of a 16-phases prototype show the effectiveness of the proposed approach
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Full text linkWe 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
Power Segmentation Optimum: a novel technique for continuous optimal efficiency tracking in Monolithic DC-DC converters
No full text—This paper presents a novel mixed-signal architecture for the extraction and online tracking of the maximum efficiency point in generic integrated DC-DC converters, called Power Segmentation Optimum. This optimal condition is achieved by dynamically adjusting the size of the power switches to minimize total losses. Proposed system continuously tracks the optimal efficiency point under all operating conditions, adapting to both external factors (such as input/output voltage, switching frequency, temperature and output current) and internal parameters (such as MOSFET ON-resistance and gate capacitance). The operating principle consists in a A/D mixed signal implementation which continuously extracts and compares a proportional value of each loss contribution, deriving the corresponding configuration which minimizes the total losses. This technique is particularly suitable for IoT applications, characterized by long idle periods and high current pulse transients. In order to validate the theoretical results, proposed method is implemented inside a 5A DC-DC fully-integrated buck converter realized in 180nm technology with 5V input voltage rating and switching frequency up to 4MHz
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