一种基于电流控制模式的白光LED驱动芯片的设计

设计了一款基于2μm bipolar工艺、应用于彩色LCD背光照明的白光LED驱动芯片。采用PFM控制模式、低反馈电阻及负载电流反馈技术实现芯片驱动的低功耗和恒流输出。系统仿真结果表明,负载电流为20mA时,输出电压纹波系数为0.013%/V,输出电流纹波系数为0.02mA/V,效率为80.1%;芯片版图面积为0.67mm×1.28mm。     

电流型电化学传感器恒电位仪电路的研究

电流型电化学传感器在与目标气体发生反应的同时,还会与其他氧化性气体发生反应,影响测量值。针对上述问题,根据恒电位仪工作原理,利用高精度基准电压源、直流负反馈电路及参比电极电路研究了一种恒电位仪电路,为传感器工作电极提供一个恒定电位,提高传感器的选择性。同时对工作电极相对于参比电极的电压与给定电位的关系进行实验,获取了控制电位的性能指标。实验验证了该电路具有给定电位稳定（相列误差不大于0．2％）、控制电位精度高（相对误差不大于0．3％）、易于实现等特点。     

电流模式的高阶曲率补偿CMOS带隙基准源

因为传统的带隙电压基准源只经过了一阶温度补偿,且输出电压只能在1.2 V左右,所以为了得到一个可调的、更高精度的电压基准源,提出了电流模式的带隙电压基准源电路。电路采用了高阶曲率补偿方法,且输出的基准电压可根据输出电阻的大小进行调节。电路采用gpdk090 CMOS工艺,通过Spectre仿真,当电源电压为3.6 V、在-60℃~-120℃温度范围内、温度系数为14.4×10-6/℃时电源电压抑制比为78.3 d B,输出电压平均为1.162 V。     

基于电流模电路的通用宽带电流放大器的设计与仿真

设计了一种基于电流模电路的宽带电流放大器。系统由宽带I/V变换器、电压放大器以及宽带压控电流源三模块直接耦合级联而成。详细论述了电路设计原理、电路结构以及元件参数选择方法。通过选用电流反馈型运算放大器设计电路,不受电压反馈型运放增益带宽积和有限压摆率的限制,提高了电流放大器的带宽;用负载接地的豪兰德电流源设计压控电流源,实现较高精度的V/I转换;采用三级结构,增益及带载能力可以根据实际需要灵活调节。系统仿真结果表明,论述的电路设计方法是可行的。测得典型电路的输入电阻约为0.13Ω,输出电阻为约59 kΩ,电流增益为60 d B。     

Fabrication of planar and three-dimensional microcoils on flexible substrates

Inductors are basic components of magnetic sensors. Generally, with those sensors, a weak magnetic variation has to be detected. As the sensitivity increases with the inductance value, our objectives are to design inductors with a maximum of turns while keeping millimetric sizes for the sensor. In this work, we present two microcoil fabrication processes compatible with rigid and flexible substrates. The first one is used for the realization of planar microcoils with one step of copper micromoulding. For example, a 40-turn microcoil of 1 mm external diameter and 5 μm copper width and spacing wires has been obtained. The second process allows the fabrication of three-dimensional microcoils (microsolenoids). It is based on two steps of copper micromoulding. In this process, a grey-tone photolithography step is implemented. Microsolenoids with 10–13 wires have been realized.     

电流模ADC发展概况与趋势

高性能数据转换器在数字信号处理中起到非常重要的作用,高速、高精度模数转换器的性能制约着现代信息技术的发展。本文对新兴的电流模式ADC的发展状况进行回顾,总结了电流模ADC的性能特点,并将电流模式和电压模式ADC的性能特点和发展趋势进行比较,同时对制约ADC、特别是电流模式ADC性能的主要因素进行了详细分析。     

Generation of ZnO nanowires with varied densities and lengths by tilting a substrate

Recently, ZnO nanowires have received wide attention. Existing fabrication approaches mainly focused on generating such nanowires with uniform density and length over a substrate. On the other hand, ZnO nanowires with gradients of density and length over a single substrate could make the corresponding devices have varied properties. Therefore, in this work, we developed a simple approach to generate ZnO nanowires of varied morphology on a common substrate. This was achieved by creating a boundary layer of non-uniform thickness which affected the amount of reactants reaching the surface during the growth. This was done by tilting the substrate relative to the incoming gas flow. Here, we first presented theoretical background of the critical idea, and then simulated the thicknesses of boundary layers for different substrate tilt angles. Finally, based on these theoretical and numerical investigations, we fabricated two types of surfaces, which had one- and two-tier wire structures, respectively.     

基于恒流模式的比例阀控制系统的设计

针对传统的采用PID控制技术的比例阀控制系统在控制性能要求较高的场合不能满足要求的问题,提出一种基于恒流模式控制的比例阀控制系统的设计方案,分析了恒流模式的控制原理及其数学模型,详细介绍了系统控制电路的设计以及采用STM32F103VET6实现数据校正算法。实际应用表明,采用恒流模式对比例阀的压力和流量进行控制具有价格低廉、重复性好、功耗小、抗干扰能力强等优点。     

Risk evaluation approaches in failure mode and effects analysis: A literature review

Failure mode and effects analysis (FMEA) is a risk assessment tool that mitigates potential failures in systems, processes, designs or services and has been used in a wide range of industries. The conventional risk priority number (RPN) method has been criticized to have many deficiencies and various risk priority models have been proposed in the literature to enhance the performance of FMEA. However, there has been no literature review on this topic. In this study, we reviewed 75 FMEA papers published between 1992 and 2012 in the international journals and categorized them according to the approaches used to overcome the limitations of the conventional RPN method. The intention of this review is to address the following three questions: (i) Which shortcomings attract the most attention? (ii) Which approaches are the most popular? (iii) Is there any inadequacy of the approaches? The answers to these questions will give an indication of current trends in research and the best direction for future research in order to further address the known deficiencies associated with the traditional FMEA.     

峰值电流控制模式中的自适应斜坡补偿技术

为了解决PWM(脉冲宽度调制)峰值电流模式中当占空比大于50%时发生次斜坡振荡的问题,提出了一种当输入输出电压变化时补偿量跟随变化的斜坡补偿电路方案。与固定斜坡补偿电路相比,本文设计的自适应补偿电路有更好的跟随性,还可避免发生过补偿问题。电路采用gpdk090 CMOS工艺仿真,由仿真结果可知,该电路可以很好地抑制次谐波振荡,提高电路的稳定性和性能。     

峰值电流模升压转换器的动态斜坡补偿电路设计

基于HHNEC 0.35 μm BCD工艺设计了一种应用于峰值电流模升压转换器的动态斜坡补偿电路.该电路能够跟随输入输出信号变化,相应给出适当的补偿量,从而避免了常规斜坡补偿所带来的系统带载能力低及瞬态响应慢等问题.经Cadence Spectre验证,该电路能够达到设计要求.     

Characterization of the influence of fabrication methods on microstructure failure

Single-crystal silicon microstructures, of identical design, exhibit different failure rates (following fabrication or mechanical shock testing) due to various processes. The microstructures fabricated with a boron diffusion and subsequent removal of the boron-diffused layer have a higher survival rate to the fabrication process and to mechanical shock. The survival rate (a survivor has an intact proof mass and beam) through the process is increased by 26.5%. At a 3680g shock, the boron-diffused devices have a 2.3% lower failure rate but the difference is not statistically significant. These results have been developed with wafer-level shock testing, which permits bulk testing of many samples in a cost-effective manner.     

The influence of finite width interfaces on mixed mode stress intensity factors

The problem of a crack approaching a finite width interface is investigated using finite elements. The crack is inclined to the interface and a condition of mixed mode fracture exists. The influence of a finite width bond line interface is considered for one representative material pair combination (E₂/E₁ = 0.10). The stress intensity factors for an inclined crack at various distances from the interface are established as a function of interface width. Maximum cleavage stress and probable angles of crack extension are presented as a function of crack inclination and interface width. Circumferential variations of σ_rr, σ_θθ, and α_rθ are also presented as functions of crack inclination and interface width.     

Risk prioritization in failure mode and effects analysis under uncertainty

Failure mode and effects analysis (FMEA) is a powerful tool for identifying and assessing potential failures. The tool has become increasingly important in new product development, manufacture or engineering applications. Generally, risk assessment in FMEA is carried out by using risk priority numbers (RPNs) which can be determined by evaluating three factors: occurrence (O), severity (S) and detection (D). Due to the vagueness and uncertainty existing in the evaluating process, crisp numbers representing RPNs in the traditional FMEA might be improper or insufficient in contrast to fuzzy numbers. Currently, the fuzzy methods and linear programming method have been proposed as an effective solution for the calculations of fuzzy RPNs. However, considering the fact that fuzzy RPNs are determined on a multidimensional scale spanning O, S and D along with their interactions under a fuzzy environment, several gaps should be bridged in the evaluation, calculation, and ranking of fuzzy RPNs. First, decision makers tend to use multi-granularity linguistic term sets for expressing their assessments because of their different backgrounds and preferences. Second, numerical compensation may be existed among O, S and D that can derive different RPNs in the engineering applications. Third, the complete ranking results for fuzzy RPNs may be easily changed by the effects of uncertain factors. In this study, a fuzzy-RPNs-based method integrating weighted least square method, the method of imprecision and partial ranking method is proposed to generate more accurate fuzzy RPNs and ensure to be robust against the uncertainty. A design example of new horizontal directional drilling machine is used for illustrating the application of the proposed approach.     

我国集成电路产业发展影响因素及发展模式探索

集成电路产业有其独特的发展规律和特点,影响其发展的因素是多方面、复杂的。认识与分析集成电路产业发展的影响因素,探索适合我国国情的产业分工,不仅是新的理论研究课题,而且是发展集成电路产业的实际需要。本文力求从多个方面、多个角度,通过系统分析和数据验证,研究集成电路产业的影响因素,对现阶段我国集成电路产业发展模式进行探讨。     

Leakage current in a Si-based nanopore structure and its influence on noise characteristics

We have measured leakage current in a silicon substrate-based nanopore membrane device immersed in an aqueous environment which typically shows the current level of few nA. This current level is compared with the measured current density (400 nA/cm² at 1 V) from the pristine Si wafer (p-type, 10¹⁶/cm³ boron doping) indicating that the exposed Si surface in a nanopore membrane device acts as an electrochemical reaction site. The leakage current is drastically reduced from >10 nA to <100 pA at 1 V by the deposition of a dielectric layer to the Si-based nanopore membrane device. We also noted that the root-mean-square noise of the ionic current is also reduced from 38 to 28 pA in correlation with the reduction of leakage current, indicating that electrochemical reaction provides one of the major sources of noise.     

平均电流控制模式负载点电源(POL)的控制系统设计

设计了一种基于MAX5060并采用平均电流控制模式的DC/DC变换器的控制系统。该变换器为输出电压可调的负载点电源(POL),采用大信号系统和小信号系统相结合的方法设计控制回路。详细分析了电源的控制系统设计。     

开关电源中功率MOSFET管损坏模式及分析

结合功率MOSFET管不同的失效形态,论述了功率MOSFET管分别在过电流和过电压条件下损坏的模式,并说明了产生这样的损坏形态的原因,也分析了功率MOSFET管在关断及开通过程中发生失效形态的差别,从而为失效在关断或在开通过程中发生损坏提供了判断依据。给出了测试过电流和过电压的电路图。同时分析了功率MOSFET管在动态老化测试中慢速开通、在电池保护电路应用中慢速关断及较长时间工作在线性区时损坏的形态。最后,结合实际应用,论述了功率MOSFET通常会产生过电流和过电压二种混合损坏方式损坏机理和过程。     

自适应流模式负荷分担设计与实现

随着Internet的高速发展,Internet中的通信流量迅速增长,对高端核心路由器设计提出了更高要求,不但要实现高线速转发,而且对带宽、时延等性能的要求也越来越高。本论文在逐流模式基础上,统计参与分担的各链路实际流量,设计并实现了自适应流模式负荷分担,确保了分担链路负载的动态均衡,提高了链路带宽的利用效率和分担性能。