基于反馈控制的高能效LED驱动电路设计

为了提高可调光发光二极管（LED）的灵活性和能量效率,提出了一种基于反馈控制的LED驱动器。该驱动电路采用了自适应电压调节技术,使线性电流调节器的功率损耗降到了最低。并设计了相应的基于电阻数字模拟转换器的数字控制机制,可用于馈送dc–dc转换器的模拟反馈输入。实验结果显示,提出的数字控制方法灵活性和稳定性较高,且能够有效控制调节速度。当输入电压为26 V时,LED驱动器能够提供较宽的5~40 V输出电压范围,获得了较大的灵活性。在输出电流为680 mA时,稳定状态下的精确度超过97.7%,频率为1 kHz且最短的接通持续时间为4 μs,系统的峰值效率达94.1%。     

基于新型1200V碳化硅(SiC)MOSFET的三相双向逆变器的研究

研究了基于新一代宽禁带1 200 V碳化硅(SiC)MOSFET三相双向逆变器,由于SiC MOSFET的高耐压、低损耗、高开关频率特性,逆变电路的拓扑结构得到简化,并提高了功率密度和可靠性。同时,利用碳化硅MOSFET的双向第三象限导通特性,与硅基IGBT相比省略了开关器件的反并联二极管。20 k VA实验样机验证了在该中大功率三相双向逆变器中SiC MOSFET相比硅基IGBT方案的优势。     

Carbon-sensitized and nitrogen-doped TiO2 for photocatalytic degradation of sulfanilamide under visible-light irradiation

A novel carbon-sensitized and nitrogen-doped TiO₂ (C/N-TiO₂) was synthesized by a facile sol-gel method using titanium butoxide as both titanium precursor and carbon source, and nitric acid as nitrogen source. The calcination temperature had a great effect on the crystal phase structure, nitrogen incorporation into the TiO₂ lattice and content of carbonaceous species. The incorporated carbonaceous species could serve as photosensitizer, while the nitrogen doping could lead to the remarkable red shift of absorption edge of C/N-TiO₂. The C/N-TiO₂ calcinated at 300 °C (T300) exhibited the highest photocatalytic activity for sulfanilamide (SNM) degradation under irradiation of visible-light-emitting diode (vis-LED). The SNM photocatalytic degradation and mineralization were more efficient in acidic conditions due to the carbon photosensitizing effect. Insignificant inhibitory effects were observed in the presence of chloride, nitrate and sulfate, while bicarbonate, phosphate and silica could inhibit the SNM mineralization to different degrees. Acetate, ammonium and sulfate were released during SNM mineralization. T300 exhibited good photochemical stability and could be reused for 5 times with less than 10% decrease in the SNM removal efficiency. The acute toxicity of SNM solution could be reduced over prolonged photocatalysis according to the Microtox assay.     

A model for correcting the fluorescence signal from a free-falling depth profiler

Measuring chlorophyll fluorescence at five different wavelengths provides the discrimination of four phytoplankton groups. Here the problems associated with a free-falling depth profiler for phytoplankton discrimination are considered. When F0, F, and Fm are determined sequentially in the same measuring cell, then the algae inside the cell have a different light history. It depends on their different locations in the cell as caused by the induction curve of chlorophyll fluorescence. Mathematical algorithms are developed which enable the calculation of the concentrations of individual phytoplankton groups from the integral fluorescence signal (averaged for 1s) for different velocities of the falling probe. The theory requires the knowledge of the fluorescence behaviour of phytoplankton in stationary suspensions. The predictions of the model are compared with measurements in flowing suspensions containing chlorophyta, cyanobacteria, cryptophyta and diatoms. The comparison shows the reliability of the algorithms. The application of the algorithms is indispensable for dark-adapted cells and is less important for light-adapted cells.     

Parameter extraction of solar panels using the graphical method

ABSTRACT

An effective approach to extract the loss parameters of solar panel is developed and able to accurately represent their electrical behaviour. This method allows extracting the parameters of the single-diode model using only the information provided by the manufacturer's datasheet with a low-cost parameter determination technique and no complexity. The complete equation of the single- diode model of solar cells and panels is used, where the number of parameters to be calculated is reduced only to two parameters by a transcendental equation exclusively connecting the series resistance and the diode current, which is solved using the graphical method. The accuracy of the presented approach is justified by experimental data. In addition, the results of the proposed procedure are compared to the most recent proposed techniques in the literature. Furthermore, the results show a highly accurate; in particular, at the maximum power point, the error is still much less than 0.01%.     

半导体激光器可靠性评估系统设计

介绍了一种基于单片机控制的可预置工作电流值、工作温度值的半导体激光器可靠性评估系统的软、硬件设计方法.该方法以89C51单片机为核心部件,通过闭环反馈控制系统对工作电流、工作温度进行比较、调整,提高系统精度.该可靠性评估系统可实时显示工作电流及工作温度值.     

氧化锌压敏电阻老化分析

摘要：限压型电涌保护器（SPD）的老化问题,经分析是由于ZnO压敏电阻内部的离子迁移导致肖特基势垒的畸变,从而引起泄漏电流与压敏电压增加等。通过对几组ZnO压敏电阻在老化环境下的试验,分析老化前后压敏电阻性能参数的变化,得到如下结论：交流老化过程中,压敏电压和漏流存在一定的逆老化现象．但压敏电压和漏流随老化呈增长趋势;（爹交流老化时,压敏电阻温度的升高与加热时间、施加电流以及老化程度有关,伏安特性曲线发生对称漂移;（萤交流老化之后,压敏电阻内阻的变化不大．且局部有降低的趋势,分布电容、阻抗和非线性系数的变化较小。     

低频带通与带阻自由切换的频率选择表面

为了在不同时域下获得兼具带通与带阻空间滤波功能的低频频率选择表面(FSS),提出了一种带通与带阻型FSS可自由切换的设计方法,即在基于卷曲技术设计的小型化FSS表面上贴装电控PIN二极管,并利用"场-路"协同仿真的方法进行建模与计算。其中,卷曲图案既是滤波结构,也是馈电导线。当PIN二极管导通时,卷曲图案缝隙处产生的电容C1与金属贴片电感L1构成并联LC回路,FSS表现为带通滤波功能;反之,焊盘处缝隙及反偏PIN二极管产生的电容C2与金属贴片电感L2串联,FSS切换为带阻滤波功能。采用印刷线路板及表面贴装工艺制作出了400 mm×400mm试验样件并采用自由空间法进行测试,仿真与测试结果表明:在2.45GHz处,当PIN二极管导通时,FSS表现为强透射性能,反之则表现出强反射效果。这种基于电控PIN二极管开关所实现的带通与带阻型FSS自由切换方法在通信、电磁屏蔽及雷达隐身等领域具有广阔的应用前景。     

Standalone PV-fed LED Street Lighting Using Resonant Converter

This paper proposes a single-stage, single-switch, non-isolated step-up converter with resonant inverter for a standalone photovoltaic battery-powered light-emitting diode (LED) street light. The LED driver presented in this paper integrates a high step-up DC–DC converter with coupled inductors and LCC resonant converter into a single-stage conversion circuit topology. The proposed converter is a compact cost-effective driver for powering a 60 W LED Street light with a battery backup charged from PV array of 12 V. The modes of operation and analysis of the proposed converter are explained. The design of the circuit elements is done based on the theoretical analysis. The proposed circuit has been simulated, and prototype has been developed to demonstrate its feasibility.     

A 0.6‐V sub‐mW X‐band RFSOI CMOS LNA with novel complementary current‐reused technique

A fully integrated 0.6 V low‐noise amplifier (LNA) for X‐band receiver application based on 0.18 μm RFSOI CMOS technology is presented in this paper. To achieve low noise and high gain with the constraint of low voltage and low power consumption, a novel modified complementary current‐reused LNA using forward body bias technique is proposed. A diode connected MOSFET forward bias technique is employed to minimize the body leakage and improve the noise performance. A notch filter isolator is constructed to improve the linearity of low voltage. The measured results show that the proposed LNA achieves a power gain of 11.2 dB and a noise figure of 3.8 dB, while consuming a DC current of only 1.6 mA at supply voltage of 0.6 V. Copyright © 2017 John Wiley & Sons, Ltd.