一种新颖四象限隔离型反激双向直流变换器

隔离型反激DC-DC变换器具有较高增益和较大功率等级,已成为高增益大功率场合的研究焦点,针对传统反激变换器存在的变压器漏感尖峰的问题,提出一种带反激缓冲器的隔离式四象限全桥双向DC-DC变换器。应用钳位电容和反激缓冲器来钳位因流馈式电感和隔离变压器漏电感间的潮流差而引起的尖峰电压,成功地把电压钳位到理想水平;同时消除了因漏电感的续流带来的开关损耗,提高了变换器工作效率;缓冲器还限制漏感电流ip在全桥开关中循环,在超载情况下降低了开关电流应力,提高了系统可靠性。实验证明了理论分析正确性和可行性。     

基于RBF网络和ADPCM的增益非线性量化

本文在G.728语音编码算法的码书归一化和增益精确表示的基础上,使用ADPCM对增益进行量化,提出对自适应量化阶距采用RBF网络进行非线性预测,将之运用到G.728算法的增益量化中.仿真结果表明:采用RBF网络的非线性自适应量化阶距方案比标准的G.728编码算法的平均分段信噪比提高1.63dB,这对于降低G.728算法的码率具有重要意义.     

具有LCL单元的磁集成Boost变换器

提出一种由2个电感、一个电容和2个二极管组成的LCL单元,利用该单元的储能作用,提高升压变换器的电压增益.应用磁集成技术对电感进行耦合集成,降低电感电流纹波.为进一步增加电压增益、减小开关管的电压应力引入电容C2.分析了变换器的工作原理,推导了电压增益公式、开关器件的电压应力和电感电流纹波.与传统Boost变换器相比,...     

一种基于SEPIC结构的非耦合电感高增益变换器

针对应用于新能源系统的变换器电压增益不高及电压应力过大等问题,提出了一种基于SEPIC结构的非耦合电感高增益变换器.该变换器不采用变压器或耦合电感来提高电压增益,避免了变换器过大的体积和过大电压应力的出现.分析了变换器的两种工作模式,并与结构相似的变换器在电压增益和电压应力方面进行了对比.在理论分析的基础上,试制了一台200 W样机.由实验结果可知,变换器的工作状态与理论分析一致,变换器具有连续的输入电流,在具有较高电压增益的同时又具有较小的电压应力,适用于光伏发电等新能源系统.     

一种大带宽高增益微带天线的研究与设计

普通微带天线带宽很窄,大多数扩展其带宽的方法是以牺牲天线增益为代价的.本文提出了一种新型大带宽、高增益微带天线结构.该天线采用厚的空气介质层,通过与贴片相连的斜置金属带进行馈电.此外,还采用了U形接地板来提高天线的增益.利用HFSS仿真软件计算和分析,探讨了各结构参数的变化对天线性能的影响,给出了详细的设计过程.仿真结果表明,该天线在驻波比小于2 时的相对带宽可达75.5%,在整个频带内的平均增益为7.31 dBi,而且,方向图和增益随频率变化较平稳.     

永磁同步电机转速环扰动反馈线性化控制

针对永磁同步电机运行过程中的不确定性扰动问题,设计了基于高增益扩张观测器的永磁同步电机转速环扰动反馈线性化控制器.首先,基于永磁同步电机完全数学模型设计了高增益扩张观测器对系统不确定性扰动进行观测.其次,结合系统电流环PI控制,设计了基于电机简化数学模型的高增益扩张观测器,有效降低了观测器阶数,提高了系统执行效率.最后,在扰动观测的基础上,对系统转速环进行反馈线性化控制,提高了系统在扰动下的转速动态响应性能.对比实验结果验证了反馈线性化控制器在抗扰动方面的优势.     

基于Sepic的单开关高增益DC/DC变换器

为解决传统耦合电感型升压变换器电压增益低、输入电流纹波大等缺点.将传统的Sepic变换器与耦合电感、开关电容两种电压增益提升单元组合,提出了一种新型的高增益变换器.该变换器在提高电压增益的基础上削弱了MOS管漏、源极间于振荡所产生的电压尖峰,并且保留了Sepic变换器输入电流连续的优点,适合应用在可再生能源系统中.首先利用耦合电感替换Sepic变换器中的输出电感,随后引入开关电容单元与无源箝位电路,增加电压增益的同时还解决了漏感问题,漏感能量得到了循环利用,从而进一步提高了变换器效率.详细分析了该新型高增益变换器的工作原理,并且在实验室构建了一台额定功率为200 W的实验样机,实验结果成功验证了所提变换器原理分析的正确性与可行性.     

采样系统快时变扰动比例积分观测器鲁棒H2/H∞控制

针对控制系统存在快时变扰动或噪声使传统观测器存在较大观测误差问题,依据鲁棒控制理论,采用线性矩阵不等式(LMI)方法,设计鲁棒H2/H∞全维状态比例积分观测器.研究系统在快时变扰动情况下,采样系统基于改进比例积分观测器的状态观测效果及鲁棒稳定性,得到一类充分条件,给出快时变扰动观测器比例增益、积分增益、控制器增益以及鲁棒H2性能指标的求解方法.仿真结果表明:所设计的观测器鲁棒性强,提高了状态观测精确度.     

风能转换系统的MPPT变增益极值搜索控制

针对传统最大功率点追踪(MPPT)极值搜索法固定积分增益存在的不足,依据不同积分系数对系统的影响,提出了一种MPPT变增益极值搜索法,使积分增益随叶尖速比和功率系数之间平均相位移的变化而变化.仿真结果表明,采用改进后的MPPT极值搜索法,平均风能捕获率较传统的极值搜索法有所提高,且当系统达到稳定运行点后,叶尖速比的标准差较积分增益为0.01时降低了0.05,有效地抑制了系统在稳定点附近的振动,提高了系统的动态性能.     

基于耦合电感与开关电容单元的高增益DC/DC变换器

提出一种基于耦合电感与开关电容单元的高增益DC/DC变换器.将开关电容单元集成到电路拓扑中,并拓展至n个,提高该变换器调节增益的自由度,使其不仅能通过改变耦合电感匝比来调节电压增益,还能通过增减开关电容单元来改变电压增益.耦合电感中漏感的电流不能突变,使得二极管的反向恢复问题得以解决.漏感能量通过无源箝位电路得到了很好的吸收,进而降低了开关管的电压应力,提高了变换器的效率和可靠性.分析了所提电路拓扑的工作原理,并对比分析了变换器的性能特点.最后,制作了一台输入电压为20～40 V,输出电压为380 V,额定功率为300 W的样机进行实验验证.主要工作波形与理论分析基本一致,且实测最高效率为95.4％,从而验证了理论分析的正确性与所提变换器的可行性.     

Enhanced active‐feedback frequency compensation with on‐chip‐capacitor reduction feature for amplifiers with large capacitive load

A large capacitive load amplifier with enhanced active‐feedback frequency compensation is proposed in this paper. The enhancement is achieved through using a wide‐bandwidth scalar circuit to increase the transconductance of the output stage so that the overall bandwidth of the amplifier can be extended considerably. Implemented in a standard CMOS 130‐nm technology, with a supply of 0.7 V and consuming 27 μA of current, the amplifier drives a load capacitor of 15 nF. No on‐chip resistor is needed; only a 0.91‐pF compensation capacitor is used to maintain stability. The achieved gain‐bandwidth product and phase margin are 1.28 MHz and 66.9°, respectively. Moreover, the slew rate is 0.263 V/μs. The active chip area is 0.0056 mm². Copyright © 2017 John Wiley & Sons, Ltd.     

Design of a 1‐GSample/s 9‐b double sampling track‐and‐hold amplifier in BiCMOS technology

This paper gives a detail presentation of a fully pseudo‐differential open‐loop BiCMOS track‐and‐hold amplifier (THA) for 9‐b operation up to 1 GSample/s. The proposed THA not only uses a double sampling technique to increase the achievable sampling frequency by a factor of two, but also employs a linearization technique to reduce the gain dependence of the THA input stage upon the input level. Moreover, timing mismatch between the clock signals of the two interleaved paths is minimized by means of a timing mismatch insensitive clock generator controlled by a common master sampling clock. The post‐layout simulation results using TSMC 75 GHz f_T, 0.35‐µm SiGe BiCMOS technology show that the proposed architecture achieve a signal to noise and distortion ratio of 53.92 dB, equivalent to the effective number of bits of 8.66‐b for 58.11 MHz input frequency at 1 GSample/s. The power dissipation of the whole THA is 161.1 mW. Copyright © 2012 John Wiley & Sons, Ltd.     

An offset cancellation technique of complementary input pair buffers for continuous time applications

This letter describes an offset cancellation technique for rail‐to‐rail complementary input pair operational amplifiers in unity gain loop configuration that overcomes the variable offset and minimizes distortion. The simulated buffer exhibits up to 40 dB increase in spurious‐free dynamic range and up to 30 dB increase in signal‐to‐noise and distortion ratio. When used to buffer a continuous time modulator, the performance matches that of chopping. Measurement results verify the technique, illustrating effective offset cancellation regardless of the input signal level. Copyright © 2016 John Wiley & Sons, Ltd.     

Z Copy‐Controlled Gain‐Current Differencing Buffered Amplifier and its applications

The Z Copy‐Controlled Gain‐Current Differencing Buffered Amplifier (ZC‐CG‐CDBA) is introduced in the paper. In addition to the well‐known CDBA, the input Current Differencing Unit (CDU) is modified and completed by special circuits. Analogously to the conventional CDBA, the z terminal is internally connected to the input of voltage buffer. The current gain from the difference input p, n to the output z can be controlled electronically or by an external device. In addition, an independent high‐impedance output zc is available, providing difference current I_p?I_n. In the paper, the extension of application range of the ZC‐CG‐CDBA compared with the conventional CDBA is referred to. The novel circuit element is assembled from commercial integrated circuits and its principle is verified experimentally on a universal second‐order filter. Copyright © 2010 John Wiley & Sons, Ltd.     

化学水浴法制备ZnS薄膜

采用了化学水浴法制备异质结薄膜太阳电池中的窗口层ZnS薄膜.尝试了酸性溶液制备ZnS薄膜,讨论了溶液成分、水浴时间和温度对薄膜成分和形貌的影响.研究结果表明在75℃,6 h条件下沉积得到的薄膜最平整,成分最符合化学计量比,退火后薄膜主要为纤锌矿结构的ZnS相.     

高压换流阀可控硅组件均压特性的研究

高压直流输电系统用可控硅换流阀要求在各种条件下都能稳定运行 ,这必须合理地选择可控硅辅助电路参数来保证系统的稳定操作 ,并降低可控硅换流阀的能量损耗。用可控硅宏模型对换流阀内的一个可控硅模块进行动态仿真研究 ,综合考虑可控硅的开通、关断特性以及可控硅换流时电压振荡特性和器件的能量损耗 ,从而给出优化的电路参数     

Gain Measurements of THz Quantum Cascade Lasers using THz Time-Domain Spectroscopy

Terahertz (THz) time-domain spectroscopy is used to investigate the gain and losses of a THz quantum cascade laser (QCL) operating at 2.86 THz. This measurement technique allows access to the amplitude and phase spectra, allowing the direct determination of the gain. At the emission frequency of the QCL, a value of 6.5 cm^-1 is found. The gain can also be studied as a function of different operating conditions, even when no laser action is present. Effects such as gain clamping and spectral narrowing are also observed. Furthermore, temperature measurements illustrate the reduction of the gain as the temperature is increased.     

Teaching microwave amplifier design at the undergraduate level

Many textbooks on the subject of microwave amplifier design contain redundant material that may overload and confuse a student confronting microwave amplifiers for the first time. Some topics such as unilateral gain and unilateral design are often not necessary in this day of personal computing where exact gain and gain circle calculations can easily be used. Stability circles can be used to both identify allowable values of source and load reflection coefficients for the transistor and ascertain whether or not the transistor is unconditionally stable. By eliminating redundant topics and emphasizing the dual role of stability circles, instructors are able to effectively teach undergraduate students in a relatively short time design methods for narrow-band low-noise amplifiers, both single-stage and multistage, which employ either conditionally or unconditionally stable transistors.     

基于非线性状态观测器的永磁同步电动机无位置传感器矢量控制

应用微分流形理论分析了面贴式永磁同步电动机在不同工作状态下的状态不可区分性,研究了其旋转坐标系模型的局部弱能观及全局能观性。在此基础上,设计了降阶全局能观测子系统的高增益非线性电流-速度观测器,并将其应用到转子速度的实时估计中。基于大范围调速及暂态过程中估计值偏差大的情况,利用观测到的交轴电流微分值设计了观测器自适应增益率,分析了其对观测器状态收敛的适应性。利用直轴观测到的电流与实际测量值的微分差值设计了转子的位置估计器。分析了该方法对定子电阻及外部转矩扰动的参数变化鲁棒性。为了验证所提方法的正确性,分别进行了数值仿真及实验验证。