功率二极管反向恢复特性模拟研究

针对功率二极管反向恢复既快又软的开关特性要求,根据Rajapakse．二极管反向恢复模型,模拟二极管反向恢复I-t、V-t变化规律,模拟结果与已有文献结果吻合,通过控制变量得到不同存储时间trra、恢复时间trrb、正向电流If、正向电流上升速率dIf/dt对反向恢复电流的影响,模拟结果表明：trra,trrb跟二极管反向恢复过程密切相关。文中最后分析计算了不同电压,不同电流下二极管反向恢复过程中的功率损耗。     

高压二极管的反向恢复时间测试系统

通过对二极管的反向恢复过程及相关应用的研究,指出二极管反向恢复时间测试的必要性,综合比较了三种现有的反向恢复时间的测试方法的优缺点,提出并设计了一个测量范围更广、更实用、精度更高、成本也较低的高压二极管反向恢复时间测试系统。该文对设计方案进行了误差分析,根据仪器在工厂的运行情况及示波器结果显示的比较,证明方案可行且误差较小。     

快速整流二极管的一种新结构

介绍了一种新型结构的整流二极管，即多晶硅／硅结构的二极管。从理论分析和实验结果表明，这种器件的反向恢复时间很短。     

两种新结构SiGe/Si功率二极管特性模拟

提出了在 n- 区中采用掺杂浓度三层渐变式结构 Si Ge/Si功率二极管及台面结构的 Si Ge/Si功率二极管。由 Medici模拟所得的特性表明 ,在采用 n- 区渐变掺杂结构的 p+ ( Si Ge) -n- -n+ 功率二极管中 ,在正向特性基本不发生变化的前提下 ,与 n-区固定掺杂结构相比反向恢复过程加快 ,二极管下降时间 t A 缩短近 1 /2 ;在采用台面结构的 p+ ( Si Gi) -n- -n+功率二极管中 ,反向恢复特性也有明显改进 ,电流反向恢复时间缩短近 1 /3 ,而电压反向恢复时间缩短近 1 /2。     

理解功率MOSFET体二极管反向恢复特性

半桥、全桥和LLC的电源系统以及电机控制系统的主功率MOSFET、同步Buck变换器的续流开关管、以及次级同步整流开关管,其体内寄生的二极管都会经历反向电流恢复的过程。功率MOSFET的体二极管的反向恢复性能和快恢复二极管及肖特基二极管相比,其反向恢复速度要低很多,反向恢复电荷也要大很多,因此反向恢复的特性较差。这样,导致二极管的开关损耗增加,降低系统的效率,同时,也会产生较高的振铃,影响功率MOSFET的安全工作。功率MOSFET数据表中,通常给出了一定条件下的Qrr和反向恢复的时间,并没有给出和实际应用相关     

铂扩散快恢复二极管特性的研究

描述了用直拉单晶(CZ)硅片采取铂液态源扩散的方法控制少子寿命,以达到减小快恢复二极管的反向恢复时间的目的.通过一系列的实验对铂扩散二极管的特性进行研究,分析了铂扩散二极管的反向恢复时间TRR、正向压降VF以及漏电流IR等参数之间的关系,并分析了反向恢复时间TRR的温度特性.得到TRR与VF之间的理想折衷:TRR为80～500 ns,VF控制在0.9～1.3 V.不但使TRR与VF的折衷有了较大的改善,而且在材料上采用了成本较低的直拉单晶硅片代替成本较高的外延片.分析了铂扩散温度和时间对反向恢复时间TRR和正向压降VF的影响,理论上解释了各主要参数之间相互影响的原因.     

电子辐照减小大电流快速恢复二极管的反向恢复时间

报告了用电子辐照方法减小快速恢复二极管反向恢复时间的实验结果。     

电子辐照减小大电流快速恢复二极管的反向恢复时间

报告了用电子辐照方法减小快速恢复二极管反向恢复时间的实验结果。     

硅片预退火对二极管反向恢复时间的影响

本文研究了预退火对二极管反向恢复时间的影响．为获得满意的反向恢复时间，硅棒上不同部位的硅片需要不同的预退火温度．头、中、尾部的硅片最佳预退火温度分别为600℃、700℃、800℃，这是因为不同部位的硅片中主导少子寿命的因素不同．     

新型大功率快速软恢复二极管：SIOD

提出了用于高频电力线路中的一处大功率软恢复二极管新结构。该二极管阳极由低注入效率的Ｐ区及高注入效率的Ｐ区组成。大电流下Ｐ区的高注入效率使二极管正向压降显著降低，而在换地，Ｐ区的低注入效率又能使反向峰值电流显著下降，反向电流衰减变软，阴极是欧姆接触结构，同时为电子和穴提供抽取通道，大大降低了反向恢复时间。采用传统绊导体哗啦的常规工艺，作出了反向恢复软度因子ｔＢ／ｔＡ最大，ｄｉ（ｒｅｃ）／ｄｚ最小的大     

Short historical review of development of scientific branch “negatronics”

Main stages of development of negatronics are considered in the article. The review is based on the analysis of research results in the branch of creations of negatrons and devices based on negatrons which use various physical effects in gas, vacuum and semiconductors. Merits and demerits of designed negatrons are generalized. Roles of various scientific trends in the area of negatronics are noted.     

Brief Overview of Recent Developments on Negative Phase–Velocity Mediums (alias Left–Handed Materials)

This brief overview covers a rapidly occurring development in the area of microwave composite materials: isotropic dielectric–magnetic mediums wherein the phase velocity vector and the time–averaged Poynting vector are oppositely directed. Such materials have also been inappropriately designated as left–handed materials. Ramifications for aberration–free lenses, homogenization approaches, and complex mediums are also presented.     

DUBAT负阻参数的推导和功率DUBAT的设计与研制

本文第一部分用较简单而不同于文献[1]的方法推导出双基区晶体管(DUBAT)有关的负阻参数,与实验结果符合良好;第二部分对功率型DUBAT进行了设计并初步制成这种器件。     

Compact left-handed microstrip line based on multiple layered step impedance resonators

A novel compact left-handed (LH) microstrip transmission line is presented. To establish a negative permeability and permittivity, the transmission line is loaded with step impedance resonators (SIRs) and an array of thin wires on dual-layer architecture. Compared to existing LH structures, which incorporate conventional split ring resonators (SRRs), the proposed structure is three times smaller in size whilst achieving the same performance. To illustrate the electromagnetic properties of the metamaterial, both analytical and full wave analysis were performed and utilized to determine the effective electromagnetic parameters of the proposed structures. The experimental results show that a microstrip line periodically loaded with SIR only produces a rejection of ?6?dB at a resonant frequency of 5.50?GHz. The results also indicate a pass-band response for a left-handed microstrip line (LHML) constructed from SIR and thin wire arrays at the same resonant frequency.     

Negative permittivity and negative permeability of multi-walled carbon nanotubes/polypyrrole nanocomposites

Multi-walled carbon nanotubes(MWCNTs)/polypyrrole(PPy) nanocomposite particles were synthesized by in-situ polymerization. Negative permittivity and negative permeability appeared simultaneously in MWCNTs/PPy nanocomposites with different content of MWCNTs. It was found from SEM analysis that MWCNTs/PPy nanocomposite particles were randomly packed with a large number of micropores, and formed a lot of conductive loops around the micropores, some MWCNTs could be cross the micropores and increase the number of conductive loops. In the meantime, MWCNTs themselves in MWCNTs/PPy composite also formed many conductive networks. The negative permittivity behavior stem from the plasma oscillation of delocalized electrons in the conductive networks, and the negative permeability was attributed to the diamagnetic response of ring currents in the plentiful conductive loops. This study should initially find a double negative metamaterial in polymer composites.     

Positive and Negative Goos-Hauml;nchen Shifts and Negative Phase-Velocity Mediums (alias Left-Handed Materials)

On total reflection from a half-space filled with an isotropic, homogeneous, weakly dissipative, dielectric-magnetic medium with negative phase-velocity (NPV) characteristics, it is shown here that a linearly polarized beam can experience either a negative or a positive Goos-Hauml;nchen shift. The sign of the shift depends on the polarization state of the beam as well as on the signs of the real parts of the permittivity and the permeability of the NPV medium.     

SITH负阻转折特性的分析模型

提出了一个用于分析ＳＩＴＨ正向阻断态的新模型。这个模型在结构上类似于ＳＣＲ。这样,就可以把ＳＩＴＨ的二维分析简化为ＳＣＲ的一维分析。我们应用了这个模型来分析ＳＩＴＨ的负阻特性并且计算出了阳极正向转折电压,计算结果与实际测量值相符合,从而证明了这个模型的合理性。     

Sub-Wavelength Virtual Imaging Using a Pair of 2-D L Loaded and C Loaded Transmission-Line Metamaterial Slabs

The dispersion relations and impedance expressions for both two-dimensional （2-D）/μ-negative and e-negative transmission line metamaterials, which may be paired to form a virtual image of the object, are presented. Under the conjugate matched condition, the voltage distri-butions inside and outside such paired slabs are derived for a plane-wave excitation. Green＇s functions corresponding to the voltages by a y directed elementary current source excitation are utilized to computed voltage phase and mag-nitude in all regions. The 2-D plots show that the voltage waves, the propagating waves and the evanescent waves, can pass through the conjugate matched slabs and so sub-wavelength virtual imaging has been achieved.     

Measurements of n-InGaAs with MBE layers: Relevance of negative magnetoresistance in the investigated samples

Measurements of n_H were performed. n_H values showed a distinct increase at temperatures below ~90 K (1.1 μm n-InGaAs samples) and a decrease at temperatures below ~30 K (7 μm n-InGaAs samples), depending on the doping level. These trends might be related to the magnetoresistance (MR) of the n-InGaAs samples. The MR behavior of the n-InGaAs samples with respect to magnetic field and temperature was apparently dependent on the doping level. Two n-InGaAs samples, one of which had a thin InGaAs epilayer (1.1 μm) and the other with a thicker (7 μm) epilayer, showed interesting behavior at low temperature. Their behavior at magnetic fields of approximately −15000 to +15,000 G were determined. The resistivity ((ρ_G – ρ₀)/ρ₀) of the 1.1 μm sample was negative at temperatures lower than 30 K.     

浅析手机上网不良信息监测实现方案

通过对手机上网流程、内容的分析,从数据获取、分析、过滤3个层面对手机上网不良信息监测提出了技术实现方案及完整的实现流程。