基于XLT604的大功率LED驱动电源的设计

针对目前大功率LED照明驱动电源在效率、稳定性、使用寿命方面的局限性,提出一款以XLT604为控制芯片的恒流驱动电源,辅以过压保护电路,散热,过温处理电路,EMI滤波,PFC校正电路,驱动36 W的大功率LED,亮度可调,效率高达86.4%,电流可靠性好,稳定度高。     

基于峰值电流控制的反激式LED电源设计

针对高性能LED驱动成本偏高的问题,基于原边反馈与峰值电流控制方案,设计了一种经济型反激式电源拓扑,采用恒流驱动芯片BP9021A实现了其硬件电路,性能测试表明,该设计具有恒流特性好、性能稳定、结构简洁和成本低廉等优点.     

全集成的可调光白光LED驱动芯片的设计

为了实现LED驱动电路的无色偏高集成度要求,提出一种新型全集成的可调光白光LED驱动芯片。该芯片在无需外部电感、电容的同时完成了白光LED的驱动,并实现了片内集成的调光功能,可用于需要高集成度或避免电磁干扰的场合;芯片采用脉冲宽度调制(PWM)的方式来实现调光功能,在获得大范围亮度调节的同时可以避免色彩偏移现象的发生;芯片内部采用一种无外置电容的低压差线性稳压器(LDO)作为功率变换单元,具有较高的稳定性和转换速度。采用CSMC0.5μm混合信号模型进行了仿真,结果表明,该芯片可以提供占空比在0到100%之间固定变换的峰值为350 mA的输出电流,实现了大范围的亮度调节功能。     

LED汽车前照灯有源纹波补偿Buck型恒流驱动电源

针对一般照明LED驱动电源中输出滤波电解电容的寿命与LED的长寿命极不匹配的问题. 提出了一种有源纹波补偿的Buck型LED驱动电路. 电路中用有源纹波补偿支路替代输出滤波电解电容,抵消电感纹波电流,使LED灯组获得恒定直流,达到LED的理想驱动状态. 为了减小纹波补偿支路的损耗,必须控制电感电流的峰值和谷值,滞环电流控制可有效地满足这个要求. 设计和制作了输出功率为30 W的滞环电流控制、有源纹波补偿BUCK型LED驱动电源. 仿真和实验验证了上述新型电源的可行性.      

全彩色LED显示屏色度均匀性优化校正

针对LED大屏幕的色度不均匀问题,从色度学理论的基本原理出发推导出以色坐标和亮度表达的颜色匹配公式,精确地计算出显示目标颜色的三基色亮度.通过LED模组实验,采用PWM电路控制电流的占空比,牺牲部分亮度和饱和度,实现了颜色匹配.校正后,红绿蓝三基色的色坐标x,y,z差别被控制在3%以内,验证了该方法的正确性和可执行性,为LED大屏幕色度均匀性问题提供了一个简便易行的解决方案.     

峰值电流控制的有源纹波补偿Buck型LED驱动电源

为解决大功率LED照明中因电解电容导致的驱动电源与LED的长寿命不匹配这一问题,提出了采用有源纹波补偿电路取代传统驱动电源中电解电容的方案.首先,选用带斜坡补偿的、峰值电流控制的Buck型电路作为主电路,建立了峰值电流控制模式下电流环的传递函数;然后,通过幅频特性和相频特性分析,得到了不同程度斜坡补偿下的电流环稳定情况.最后,设计了峰值电流模式控制的有源纹波补偿Buck型LED驱动电源的原型电路.仿真和实验结果证实了此电路的正确性和可靠性.     

基于TMS320F2812的反激式数字开关电源设计

开关电源具有效率高、体积小、稳定性好等优点,现已广泛应用于工业自动化控制、军工、科研、LED照明等设备中.但随着微电子技术的飞速发展,开关电源的数字化己成为当前开关电源研究的热点.本文设计了一种基于TMS320F2812的反激式数字开关电源,它以TMS320F2812芯片为控制核心,通过采样电路对输出电压采样并反馈到控制芯片里,控制PWM波的占空比,PWM波经过驱动电路控制开关管的通断,使高频变压器不断地充放电为负载提供电压和电流.在设计中,为了保证输出性能和动态性能的优越,防止开关和市电干扰,在电压采样模块中采用高精度的线性光耦PC817,输入部分加入了EMI滤波电路;在软件设计中,采用模糊PID控制算法.经实际测试获得了较好的效果,有一定的应用价值.     

有源纹波补偿Cuk型照明LED恒流驱动电源

一般大功率照明LED驱动电源中,输出滤波电解电容的寿命与LED的长寿命极不匹配.对此,文中提出了一种有源纹波补偿的Cuk型LED驱动电路.电路中用有源纹波补偿支路替代输出滤波电解电容,抵消电感纹波电流,使LED灯组获得恒定直流,达到LED的理想驱动状态.文中详细阐述了有源纹波补偿的原理和实现电路,分析了有源纹波补偿Cuk型LED驱动电路的损耗和效率,设计和制作了输出功率为22 W的滞环电流控制、有源纹波补偿Cuk型LED驱动电源,通过仿真和实验验证了该新型电源的可行性.     

宽电压输入多端输出开关电源的设计

设计了一种基于电流型PWM控制芯片UC3842的多端反激式开关电源,对芯片外围电路进行了计算,高频电压器不仅实现了电气隔离和电源的多路输出,还具有储存能量的作用。采用精密并联稳压器TL431进行闭环控制,使用光耦器件作为调节环节,既可以控制芯片工况又能利用光耦隔离阻断强电对芯片控制电路的干扰。提出了一种基于纹波电流选取稳压滤波电容的方法,将电容的利用率提高从而延长电源的使用寿命。最后通过实验验证了设计电路的合理性,实验表明所设计的电源具有稳压性能优良、电压调整率低等优点。     

电动汽车车载充电器辅助电源的高效设计

为了满足电动汽车车载充电器系统辅助电源要实现宽范围电压输入和多路隔离输出的实际需求,选择单端反激式多路输出作为辅助电源主电路拓扑,详细介绍了其主电路中高频变压器、RCD电路和输出电容设计步骤及参数确定依据.控制系统采用电压外环和电流内环相结合的控制方案,其中电流内环采用峰值电流控制,基于Iw1691控制芯片将自适应多模式控制和谷值开关控制相结合,减少开关管开关损耗,实现系统的高效运行.最后,通过系统仿真测试和样机测试证实设计方案的合理有效性.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

On the Thermodynamic Limit for Responses to Static Electromagnetic Fields

For molecular systems,the quantum-mechanical treatment of their responses to static electromagnetic fields usually employs a scalar-potential treatment of the electric field and a vector-potential treatment of the magnetic field.Although the potential for each field separately is associated with the choice of an(unphysical)origin,the precise choice of the origin for the electrostatic field has little consequences for the results.This is different for the     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with     

Journal of Donghua University ( English Edition) Contents of Volume 31

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