计算机电源常见故障的检修方法

目前,计算机电源采用的基本上都是双管半桥式无工频变压器的脉宽调制变换型稳压电源。这种电源将市电整流成直流后通过变换型振荡器变成频率较高的矩形或近似正弦波电压,再经过高频整流滤波变成低压直流电压提供给负载,并且通过控制电路对振荡器输出的脉宽进行调制,从而实现稳定输出直流电压的目的。现在计算机电源功率一般为230W～250W,通过高频滤波电路共输出四组直流电压：＋5V(20A)、＋12V(8A)、－5V(0～3A)、－12V(0～3A),为防止负载过流或过压损坏电源,在交流市电输入端设有保险管,在直流输出端设有过载保护电路。在使用…     

一种小巧高效的直流升压器

<正> 一种香港产D-D 升压电路如图所示。图中BG_2L,C 组成高频振荡电路。BG_1DW 起稳压作用。接入1.5V 至5V 直流电压即输出12V 稳定直流电压。换不同DW 可得到3～35V 直流电压。全电路在一块板上构成比火柴盒还小的升压器,可取代价昂的叠层电池。作电子变容系统的调谐电源EPROM 写入电源等。有兴趣者请与武昌登月科技服务部联系。     

基于C8051F121和XSZ的无线电罗盘角度测量的设计

为解决飞机无线电罗盘输出角度信号的测量问题,设计了基于C8051F121和旋转变压器——直流电压转换器（XSZ）的测角仪。介绍了旋转变压器、旋转变压器——直流电压转换器的结构和原理,软件中航向角度的算法。     

中国低压断路器市场分析

1产品定义 低压断路器是用于交流电压1200V,直流电压1500V的电路中起通断、控制或保护等作用的电器。     

提高直流电压高内阻信号源测量精度新方法的研究

本文首次提出了一种提高测量精度的新的设计方法,这一新方法从理论上讲也适用于解决直流电压阻信号源的测量精度难题,为此,本文定义了一种全新的实用传感器电路类型－－电荷耦合传感电路（3C电路）,并用自行设计的电路证实了该方法的可行性和实用性,该新方法为大量pH计低成本地升级换代提供了一个新的途径,具有很高的经济和实用价值。     

“数据采集系统及其应用”讲座：第二讲 信号的干扰与抗干扰

一、串模干扰及其抑制法 由于供电系统中有杂波或信号在长距离传输时有电磁干扰。参杂到信号中去的纹波为信号的串模干扰,如图1中V_（Ro）由于信号不共地,对公共端存在共模干扰,如图la中从R_1上取出的电压信号对地的共模电压为5V,从R_2上取出电压的共模直流电压为7V,而真正的信号V_(R1)、V_(R2)很小。     

利用平均值电路提高直流电压基准源的温度特性

根据不同直流电压基准源芯片的温度漂移互相独立的特点,研究单个电压基准源芯片输出的温度特性,提出一种利用平均值电路降低基准电压温度漂移系数的方法。实验结果表明:温度系数最优为4.5μV/℃的4个基准源芯片,经过平均电路融合输出后,温度系数减小到2.46μV/℃,可以有效地降低直流电压基准的温度漂移系数。     

基于STM32的LED闪光灯电源的设计与制作

本系统是基于STM32的高效率LED闪光灯的电源。采用DC-DC变换器,通过按键进行界面切换,通过液晶屏显示必要信息。电池输入3V~3.6V电压升压到10.32V,然后利用场效应管和运放组成的压控恒流源来实现直流电压-直流电流变换。电源具有连续输出和脉冲输出两种模式,可以按键操作,具有输出电压限压保护和报警功能。     

过压自动保护电路

在有些地区经常出现市电220V电压升高,造成电器损坏。这里介绍的过压自动保护电路,可以解决这一问题。工作原理:220V电压经过变压器变压、整流、滤波,变成约15V直流电压。调整W,通过W、Rl分压,使BGl处于截     

基于UCC28019的AC-DC变换电路的设计

本系统是一种高功率因数AC-DC开关稳压电源,以功率因数校正控制芯片UCC28019输出的PWM波形来控制核心电路Boost升压斩波电路,使电感交替的储存和释放能量,电容交替的充放电,使输入的24V交流电压能稳定输出36V的直流电压。同时该电路输入的交流电压和输出的直流电流在较宽的范围内变换时,也能输出稳定的直流电压,当输出的直流电流或输入的交流电压在一定范围内变换时有较好的负载调整率或电压调整率,输入侧的功率因数达到0.99,具有输出过流保护、输入欠压保护功能。     

基于平衡PZT法解调的FBG传感器

提出了一种基于压电陶瓷叠堆驱动参考光纤Bragg光栅(FBG)扫描滤波的FBG传感器波长解调机构,设计了对称结构U型金属支架结构,并采用两侧粘贴光纤光栅的方式,同时对光纤光栅施加相等的预应力,这种结构扩展了解调光栅的扫描范围,平衡了压电陶瓷叠堆所受的拉力,增强了其运行可靠性,提高了扫描线性度.实验结果显示:在0-200...     

基于钼酸铅晶体电致旋光效应的光学电压传感器

研究了基于晶体电致旋光效应的光学电压传感器,电压传感元件采用了国产钼酸铅(PbMoO4)晶体。光学电压传感头仅由两块棱镜偏振器和一块钼酸铅晶体组成。实验结果表明此电压传感器具有较大的线性测量范围,例如对50-5000V工频电压测量的非线性误差低于0.2%;当测量100kHz的高频电压并利用锁相放大器检测传感信号时,最小可测量电压幅值为0.5V。此外,实验测量了所用钼酸铅晶体在635nm光波长及工频电压作用时的电致旋光系数,其数值为1.03pm/V。     

Design,modeling, and mechanical characterizations of micromachined InP-based actuator for tunable MOEMS applications

A novel InP-based microactuator, which is actuated by electrostatic means, has been proposed, designed, fabricated, and characterized for tuning applications in the 1.5 μm wavelength domains. Its structural design is based on the global optimization method. The tunable device is a big square membrane, which is supported by four identical cantilever beams. The three alternating layers Si₃N₄/SiO₂ as a distributed Bragg reflector (DBR) mirror, which were previously reported, have been formed on the top of the membrane. Based on the optical interferometric measurements, the proposed Fabry–Perot filter has demonstrated a maximum deflection of ∼321 nm with an applied voltage up to 12 V, an average sensitivity of ∼27 nm/V, a pull-in voltage of 12.7 V, and a release voltage of 10.7 V. It is also observed that its natural frequency is 88.4 kHz. This measured frequency implies that the tuning speed of our device is fast for optical operations within 0.01 ms. In addition, our device’s mirror remains so flat with a good planarity of 0.07°, which is strictly required for the filter’s optical performance. This optical performance can be achieved, when the micromachined structure has a tuning displacement up to ∼38 nm with a low tuning voltage up to 5 V. When compared with the finite element models (FEM), which were generated by the commercialized software, Coventor™, our experimental results agree well in terms of the natural frequency, pull-in voltage and deflections. Thus, our tunable filter, which is based on the optimized design, enables better performances including reduced actuation voltages, large pull-in voltage, improved device reliability, and fast switching times. Our device can also quickly snap back to the original position. In addition, the undesired spring-softening effect has been reduced.     

一种PM2.5检测传感器设计

为了减小和防治灰霾天气对人们生活和健康的不利影响,对灰霾检测设备进行了研究,提出了一种PM 2.5检测传感器设计。根据光电传感器原理,采用对射型检测方式,将波长为650nm、功率为10mW的半导体激光器作为光源,使用具有内增益、灵敏度好的雪崩光电二极管作为接收器,经过由I/V转换、电压放大和具有低偏压差、低温度漂移、高性能电压跟随器构成的调理电路处理后,完成对颗粒物检测传感器设计。实验结果表明:该传感器测量准确、响应快、误差小,为准确测量颗粒物的浓度提供了硬件基础。     

The effect of transmittance and luminous efficiency with the application of cathode mesh mask in transparent organic light‐emitting devices

With the development of organic light‐emitting devices (OLEDs), the transparent OLED is also restricted by its efficiency and stability. Thus, in order to improve the transmittance and luminous efficiency of transparent OLED, the cathode mesh mask combined with Al:Ag alloy is adopted to prepare the cathode of transparent OLED, which would enhanced the luminance, efficiency, and transmittance of the device. With the same driving voltage, the device has the highest brightness, when the cathode thickness is 85 nm. At the voltage of 13 and 14 V, the luminance, for bottom‐emission and top‐emission, is 9501 cd/m² and 1840 cd/m², respectively. The entire transmittance of the device has achieved about 78% at a 480 nm wavelength.     

The properties of lattice-shifted microcavity in photonic crystal slab and its applications for electro-optical sensor

In this paper, a micro electro-optic sensor structure and its sensing technique based on lattice-shifted resonant microcavity (H0-nanocavity) in a triangular lattice photonic crystals (PhCs) slab are presented. The H0-nanocavity is formed by only laterally shifting two adjacent holes outwards slightly in the opposite direction, which can realize a nanocavity with high quality factor (Q) value to meet the requirements of practical application. The electro-optic sensor is realized in hole-array based photonic crystal slab with triangular lattice air holes infiltrated with a nonlinear optical (NLO) polymer (n_poly = 1.6) in Silicon-on-Insulator (SOI) operating in the wavelength range from 1400 nm to 1600 nm. The simulation results of PhC electro-sensitive structure show that the optical properties of PhCs can be used to design sensing devices characterized by a high degree of compactness and good resolution. The properties of the sensor are analyzed and calculated using the plane-wave expansion (PWE) method and simulated using the finite-difference time-domain (FDTD) method. The simulation results display that the resonant wavelength of the mode localized in the microcavity shifts its spectral drop position following a linear behavior when a driving voltage ranging between 0.0 V and 3.2 V is applied, and the sensitivity of 31.90 nm/V is observed.     

忆阻值的影响参数分析

为了分析参数对忆阻器忆阻值的影响,通过搭建忆阻器的Matlab仿真模型,运用控制变量法,分别设置外加激励幅值为1,2V,电压频率为1,2Hz,忆阻器横截面积为10,25 μm2,忆阻器长度为10,20 nm,对不同条件不同参数的忆阻器模型进行了大量仿真分析.计算各伏安特性曲线和忆阻值的具体变化范围,通过对仿真数据的统一比较分析得出了不同情况下忆阻值的变化规律.     

Low Voltage Electrowetting-on-Dielectric Platform using Multi-Layer Insulators

A low voltage, two-level-metal, and multi-layer insulator electrowetting-on-dielectric (EWD) platform is presented. Dispensing 300pl droplets from 140nl closed on-chip reservoirs was accomplished with as little as 11.4V solely through EWD forces, and the actuation threshold voltage was 7.2V with a 1Hz voltage switching rate between electrodes. EWD devices were fabricated with a multilayer insulator consisting of 135nm sputtered tantalum pentoxide (Ta(2)O(5)) and 180nm parylene C coated with 70nm of CYTOP. Furthermore, the minimum actuation threshold voltage followed a previously published scaling model for the threshold voltage, V(T), which is proportional to (t/ε(r))(1/2), where t and ε(r) are the insulator thickness and dielectric constant respectively. Device threshold voltages are compared for several insulator thicknesses (200nm, 500nm, and 1μm), different dielectric materials (parylene C and tantalum pentoxide), and homogeneous versus heterogeneous compositions. Additionally, we used a two-level-metal fabrication process, which enables the fabrication of smaller and denser electrodes with high interconnect routing flexibility. We also have achieved low dispensing and actuation voltages for scaled devices with 30pl droplets.     

Controlling reflectivity of silver-corundum-silver nanostructure by DC voltage

Significant changes of the permittivity of a silver film have been detected using the surface plasmon resonance (SPR) method when a constant electric field is applied to the 177-nm dielectric corundum film placed between two silver films 49 nm and 36 nm thick. The effect manifests itself as a significant change of the reflectivity of the structure when the voltage of up to 30 V is applied to the electrodes. It is shown that the optical parameters of the anode and cathode layers strongly differ if dc voltage is above 4 V.     

一种用于人体传感器网络的接收器模拟前端

设计了一种用于人体传感器网络的低功耗接收器模拟前端,电路物理层信道利用人体进行通信,并采用了一种宽带信号传输技术,可以在0.8 V电压供电,100 mV输入敏感度条件下传输20 Mb/s的数据。片上的电压偏置电路提供了50Ω的输入阻抗。放大器采用了一种低压低功耗的Cascode结构,具有58 dB的增益,25 MHz的增益带宽积。另外采用了一种结构简单,功耗极低的电流反馈型Schmitt触发器。电路采用SMIC0.13μm标准CMOS工艺设计,面积0.02 mm2,供电电压0.8 V,功耗仅为2.2 mW。