High-voltage portable pulsed power supply fed by low voltage source

This article proposes a new structure of voltage multiplier for portable pulsed power applications. In this configuration, which is based on capacitor-diode voltage multiplier, the capacitors are charged by low AC input voltage and discharge through the load in series during pulse generation mode. The proposed topology is achieved by integrating of solid-state switches with conventional voltage multiplier, which can increase the low input voltage step by step and generate high-voltage high-frequency pulsed power across the load. After some discussion, simulations and experimental results are provided to verify the effectiveness of the proposed topology.     

Implementation of a high speed frequency synthesizer employing a dual input phase accumulator

We present a new PLL based frequency synthesizer, in which we have replaced the conventional phase frequency detector and the dividers (programmable counters) with a sequential dual input phase accumulator (DIPA), consisting of a digital circuit employing adders, registers and a ladder. The main feature of the DIPA is that the two input frequencies are not required to be normalized (divided down) to the step frequency of the synthesizer. Instead, the two different high frequencies, that is the reference and the output frequency of the synthesizer, are applied directly. The DIPA samples and normalizes their phases at very high rates, calculates their phase difference, producing an output that consists of a dc component proportional to the phase difference and harmonics of the two input high frequencies. These harmonics are high frequencies and can easily be rejected by a wide bandwidth filter of the loop, without affecting the high convergence speed of the loop. Moreover, these harmonics do not generate spurs near the output frequency. The resolution of the DIPA based synthesizer depends only on the length of the digital word of the DIPA, and its convergence speed depends on the lower of the two input frequencies. The output of the DIPA is a linear function of the phase difference of the two input frequencies and its dynamic range exceeds the limit of ±2π that governs the conventional phase detectors. Thus, the proposed frequency synthesizer based on the DIPA has low phase noise, no spurs nearby the output frequency, high resolution and fast convergence rate. Additionally, the output frequency can be digitally modulated under the control of the closed loop, either by phase or frequency modulation.     

Ceramic Substrates for High-temperature Electronic Integration

One of the most attractive ways to increase power handling capacity in power modules is to increase the operating temperature using wide-band-gap semiconductors. Ceramics are ideal candidates for use as substrates in high-power high-temperature electronic devices. The present article aims to determine the most suitable ceramic material for this application.     

EN55025:2008与EN55025:2003的差异

通过介绍EN 55025:2008版与EN 55025:2003版的差异,说明EN 55025:2008版标准在测量范围、测量方法、合格性判定以及供电电源电压范围等方面的新要求.     

Functionalization of Pyrene To Prepare Luminescent Materials—Typical Examples of Synthetic Methodology

Pyrene‐based π‐conjugated materials are considered to be an ideal organic electro‐luminescence material for application in semiconductor devices, such as organic light‐emitting diodes (OLEDs), organic field‐effect transistors (OFETs) and organic photovoltaics (OPVs), and so forth. However, the great drawback of employing pyrene as an organic luminescence material is the formation of excimer emission, which quenches the efficiency at high concentration or in the solid‐state. Thus, in order to obtain highly efficient optical devices, scientists have devoted much effort to tuning the structure of pyrene derivatives in order to realize exploitable properties by employing two strategies, 1) introducing a variety of moieties at the pyrene core, and 2) exploring effective and convenient synthetic strategies to functionalize the pyrene core. Over the past decades, our group has mainly focused on synthetic methodologies for functionalization of the pyrene core; we have found that formylation/acetylation or bromination of pyrene can selectly lead to functionalization at K‐region by Lewis acid catalysis. Herein, this Minireview highlights the direct synthetic approaches (such as formylation, bromination, oxidation, and de‐tert‐butylation reactions, etc.) to functionalize the pyrene in order to advance research on luminescent materials for organic electronic applications. Further, this article demonstrates that the future direction of pyrene chemistry is asymmetric functionalization of pyrene for organic semiconductor applications and highlights some of the classical asymmetric pyrenes, as well as the latest breakthroughs. In addition, the photophysical properties of pyrene‐based molecules are briefly reviewed. To give a current overview of the development of pyrene chemistry, the review selectively covers some of the latest reports and concepts from the period covering late 2011 to the present day.     

SSD在便携式消费类电子产品领域的应用

SSD以flash为存储核心,是近年来新兴的存储介质.它具有体积小、读写速度快、抗震、防潮防辐射、宽温度领域工作等特点,是便携式消费类电子产品绝对的最佳选择,同时也是在某些行业、某些特殊工作环境的唯一选择.文章阐述了SSD在便携式消费类电子产品领域的应用.     

Bibliography on Nullors and Their Applications in Circuit Analysis, Synthesis and Design

A bibliography on research work related to nullors and their applications in circuit analysis, synthesis and design, covering the period 1961–2000, is given.     

美国麻省理工学院"电路与电子电路"课程2002年春教学情况简介

介绍了美国麻省理工学院（MIT）电气工程和计算机科学系（EECS）2002年春“电路与电子电路”课程的教学内容-“电路理论”、“模拟电子电路”和“数字电子电路”的全新组合,先修课程-物理系“电磁学”/“经典电磁学理论”和数学系“常微分方程”/“线性代数”的电类专业导向和现代化的教学手段（在图书馆或校园网上随时可观看长达9小时的教学录像等）。MIT在电类基础课教学中所采用的这些独特做法和成功经验,对国内当前的课程改革、教材创新和教学管理都具有一定的参考价值。     

Structural and Electrostatic Complexity at a Pentacene/Insulator Interface

The properties of organic‐semiconductor/insulator (O/I) interfaces are critically important to the operation of organic thin‐film transistors (OTFTs) currently being developed for printed flexible electronics. Here we report striking observations of structural defects and correlated electrostatic‐potential variations at the interface between the benchmark organic semiconductor pentacene and a common insulator, silicon dioxide. Using an unconventional mode of lateral force microscopy, we generate high‐contrast images of the grain‐boundary (GB) network in the first pentacene monolayer. Concurrent imaging by Kelvin probe force microscopy reveals localized surface‐potential wells at the GBs, indicating that GBs will serve as charge‐carrier (hole) traps. Scanning probe microscopy and chemical etching also demonstrate that slightly thicker pentacene films have domains with high line‐dislocation densities. These domains produce significant changes in surface potential across the film. The correlation of structural and electrostatic complexity at O/I interfaces has important implications for understanding electrical transport in OTFTs and for defining strategies to improve device performance.