PT并列回路加入二次电压同期检测功能

针对某变电站两段母线二次电压并列过程中出现的电压并列装置出口继电器电路板烧毁的问题,并结合现场具体案例进行分析研究,提出了考虑一次母联断路器及母联两侧隔离开关分合位置的同时,还需验证两段母线PT二次电压是否同期。同期则驱动中间继电器,进行电压并列操作,以实现对一次系统并列和二次电压异常情况的综合考虑。分析结果表明,该方法能有效避免因二次侧电压相序、中性点连接不牢固、二次电压接线错误造成的电压并列事故。

一种动态自偏置的低功耗无片外电容LDO

基于0.13μm工艺设计的低功耗无片外电容LDO,文中采用动态自偏置技术使电路根据负载变化,提供不同的偏置电流,实现两级和三级结构下相互转化。电路采用Cascode Miller补偿,实现高稳定性。输出端加入过冲抑制电路,优化瞬态响应。仿真得到压差电压为57 mV;在-55~125℃范围内,温漂系数为27 ppm/℃;在电源电压1.2~3.3 V和负载100 nA~50 mA的变化范围内,线性调整率为0.452 mV/V,负载调整率为0.074 mV/mA。满载50 mA和电源电压1.2 V时,电源抑制比-53 dB@100 kHz,环路相位裕度大于60°。负载100 nA时静态电流2.5μA。负载瞬态响应结果展示过冲电压小于50 mV,建立时间约420 ns。此电路可调节性强,作为低功耗芯片,有着优秀的稳定性,适用于便携式产品。

CMOS low-dropout regulator with 3.3 μA quiescent current without off-chip capacitor

A CMOS （complementary metal-oxide-semiconductor transistor） low-dropout regulator （LDO） with 3. 3 V output voltage and 100 mA output current for system-on-chip applications to reduce board space and external pins is presented. By utilizing a dynamic slew-rate enhancement（SRE） circuit and nested Miller compensation （NMC） on the LDO structure, the proposed LDO provides high stability during line and load regulation without off-chip load capacitors. The overshot voltage is limited within 550 mV and the settling time is less than 50 μs when the load current decreases from 100 mA to 1 mA. By using a 30 nA reference current, the quiescent current is 3.3 μA. The proposed design is implemented by CSMC 0. 5 μm mixed-signal process. The experimental results agree with the simulation results.

Integrated Multi-channel High Accuracy Current Control LED Driver with Low Dropout Regulator

This research describes an integrated multi-channel high accuracy current control LED （light emitting diode） driver with low dropout regulator implemented in a 0.35μm TSMC 2P4M CMOS process. With the new trend of backlighting applications for mobile electronics and portable devices requiring a smaller size, lower cost, lesser noise and accurate current control LED driver, it came up with the idea of integrating more than one design features within a single chip. The analysis of using a capacitor-less low dropout regulator to power the constant current source has been explored, with the implementation of wide range battery voltage of 3 V to 5 V. Possible load current variations were introduced and verified to output a fixed voltage of 2.8 V. A regulated cascode current mirror structure forms the multi-channel configuration string of LED＇s; the design ensures a current matching of less than 1% error and achieves a high accuracy current control of less than 1% error, regardless of the LED＇s forward voltage variation. Moreover, for high end portable device with multimedia applications, dimming frequency can be set to 10 MHz. In addition, a switching output is a better approach for managing LED＇s contrast and brightness adjustment as well as maximizing power consumption, ensuring longer life for driving string of LEDs.

An Integrated Power Management Unit for a Battery-Operated Wireless Endoscopic System

This paper presents an integrated power management unit （PMU） for a battery-operated wireless endoscopic system. This PMU is integrated with a baseband chip in standard 0.18μm CMOS technology,promising low cost, ease in PCB design, and a minimum in system size. The optimized power supply architecture is derived from comparison. Circuits of sub blocks are presented in detail. As a result, only five small off-chip capacitances are required by PMU with an overall quiet current consumption of less than 100μA. Moreover,a digital calibration method is adopted to alleviate the effect of process variation. The achieved performance is also demonstrated with corresponding measurement results.

Variable Universe Fuzzy Control for Battery Equalization

In order to avoid the overcharge and overdischarge damages, and to improve the lifetime of the lithium-ion batteries, it is essential to keep the cell voltages in a battery pack at the same level,i.e., battery equalization. Based on the bi-directional modified Cuk converter, variable universe fuzzy controllers are proposed to adaptively maintain equalizing currents between cells of a serially connected battery pack in varying conditions. The inputs to the fuzzy controller are the voltage differences and the average voltages of adjacent cell pairs. A large voltage difference requires large equalizing current while adjacent cells both with low/high voltages can only stand small discharge/charge currents. Compared with the conventional fuzzy control method, the proposed method differs in that the universe can shrink or expand as the effects of the input changes. This is important as the input may change in a small range. Simulation results demonstrate that the proposed variable universe fuzzy control method has fast equalization speed and good adaptiveness for varying conditions.

Wide-area nonlinear robust voltage control strategy for multi-machine power systems

This paper presented a novel wide-area nonlinear excitation control strategy for multi-machine power systems. A simple and effective model transformation method was proposed for the system's mathematical model in the COI (center of inertia) coordinate system. The system was transformed to an uncertain linear one where deviation of generator terminal voltage became one of the new state variables. Then a wide-area nonlinear robust voltage controller was designed utilizing a LMI (linear matrix inequality) based robust control theory. The proposed controller does not rely on any preselected system operating point, adapts to variations of network parameters and system operation conditions, and assures regulation accuracy of generator terminal voltages. Neither rotor angle nor any variable's differentiation needs to be measured for the proposed controller, and only terminal voltages, rotor speeds, active and reactive power outputs of generators are required. In addition, the proposed controller not only takes into account time delays of remote signals, but also eliminates the effect of wide-area information's incompleteness when not all generators are equipped with PMU (phase measurement unit). Detailed tests were conducted by PSCAD/EMTDC for a three-machine and four-machine power systems respectively, and simulation results illustrate high performance of the proposed controller.

The twoscale asymptotic error analysis for piezoelectric problems in the quasi-periodic structure

Applications for piezoelectric effect have grown rapidly, and piezoelectric materials play important roles in countless areas of modem life. By means of twoscale method and coupled boundary layer, some new kinds of twoscale asymptotic expansions for solutions to the electrical potential and the displacement in quasi-periodic structure under coupled piezoelectric effect are derived, and the homogenization constants of piezoelectric materials are presented. The coupled twoscale relation between the electrical potential and the displacement is set up, and some improved asymptotic error estimates are analyzed.