Features and Prototypes of HTS High Q Resonant Circuit

High Te superconductor （HTS） technology has been used to develop a unique high Q resonant circuit. Such circuit or device has some special characteristics such as very high voltage generation. Theoretical study and experimental approaches have proceeded for the concept verification. This paper presents the theory about this high Q resonant circuit. The operation principle of the circuit is described. A practical prototype for HTS high voltage generation is also demonstrated. The experiment result shows that very high voltages can be achieved by the developed method using HTS technology.     

Electronics for a high temperature superconducting receiver systemfor magnetic resonance microimaging

Describes an MRI (magnetic resonance imaging) receiver system that incorporates a high temperature superconducting (HTS) resonator as a surface coil. Techniques for measuring the Q of the HTS resonator in a 7 Tesla field are discussed. A method for coupling a room temperature copper resonant circuit to the HTS element is covered, and it is shown that such a coupling scheme preserves the signal-to-noise gain afforded by the HTS coil. A preamplifier with a noise figure of <0.15 dB at 300 MHz is described     

CO2激光器高压高频充电电源的应用研究

为改善现有CO2激光器工频充电电源体积、重量大、充电精度低等缺点,开展高频高压充电电源的研究,研制一台采用全桥逆变结构和串联谐振软开关电路、输出电压36 kV、输出平均充电功率为10 kJ／s的高频高压充电电源。该电源系统采用三相380 VAC作为供电系统,大功率智能功率模块（IPM）作为全桥逆变电路,逆变交流信号经串联谐振电路及高频脉冲变压器得到高压脉冲信号,高压脉冲经整流给负载电容充电;同时,电源应用电压、电流双闭环控制系统,输出电压、电流经采样及放大反馈到电源控制芯片SG3525,SG3525通过判断反馈信号的大小控制输出PWM驱动信号的占空比。实验结果表明：电源输出电压36 kV,输出平均功率为10.8 kJ／s,充电效率为0.82,电源纹波系数为1％。电源系统保证了激光器稳定工作在30 Hz条件下。     

36kV/10kW CO2激光器充电电源的研制

为了改善现有CO2激光器工频LC谐振充电时充电电压随激光器工作频率升高而降低、影响激光输出的稳定性和光束质量,不利于装置的小型化和轻量化的问题。采用全桥逆变结构和串联谐振软开关电路,研究了36kV/10kW高频高压充电电源。该电源系统采用三相380V交流电作为供电系统,大功率智能功率模块作为全桥逆变电路。逆变交流信号经串联谐振电路及高频脉冲变压器得到高压脉冲信号,高压脉冲经整流给负载电容充电,电源应用电压电流双闭环控制系统,输出电压、电流经采样及放大后,反馈到电源控制芯片SG3525,芯片SG3525通过判断反馈信号的大小,控制输出脉冲宽度调制驱动信号的占空比。激光器放电频率为25Hz时,电源输出电压为37kV,峰值输出功率为13.05kW,充电效率为0.826。结果表明,该高频高压充电电源适合用作CO2激光器的高压充电电源。     

基于FPGA的光弹调制器用高压驱动电路设计

为满足光弹调制器对高电压、高稳定和精确易控制的驱动电压需求,设计了一种基于FPGA控制、全桥结构LC谐振升压的高压驱动电路。该电路与传统的光弹调制器驱动控制电路相比,大幅降低了直流电源的电压输入要求,通过DDS调节方波频率来控制光弹调制器工作频率,调节方波占空比来控制输出电压。该电路应用于光弹调制器实验,结果表明在光弹调制器的谐振频率下,外部直流电压为5 V时,方波占空比范围为0~50%,对应电压峰-峰值可调节范围为0~840 V。电路具有稳定可靠、操控方便、带负载能力较强等优点,能够实现光弹调制器驱动电压实时精确的控制。     

一种集成电路高压传输控制电路结构

集成电路设计中,用逻辑电平控制高压信号传输的情况很多,而传统的高压传输控制电路的结构过于复杂,版图面积较大且受工艺限制.介绍的电路能有效实现高压信号的传输和控制,且电路结构简单,利用两个NMOS实现了数字信号对高压信号的传输控制,大大简化了高压传输控制电路的复杂度.     

Design of superconducting MRI surface coil by using method of moment

A method of moment with an enhanced model to design high-temperature superconductor (HTS) RF surface coils for magnetic resonant image (MRI) is presented. The resonant frequency and quality factor (Q) of HTS RF spiral coils are simulated using this method. The agreements of resonant frequencies and Qs between the simulation and measurement are excellent with differences less than 1 % and 3 %, respectively. The 0.2-/spl mu/ m-thick YBaCuO (YBCO) thin films are deposited onto single side of 0.508-mm-thick LaAlO/sub 3/ (LAO) and sapphire substrate and patterned into a spiral shape. To accurately analyze the resonant frequency and Q of a coil, an enhanced two-fluid model is employed. HTS RF coils with diameter of 65 mm for 0.2 T and 1.5 T MRI systems are designed and fabricated with the measured Q of 19 K and 23 K, respectively. In addition, the shift of resonant frequency due to the mutual coupling between two HTS spiral coils is predicted by this method, which is important for design of HTS coil arrays in an MRI system.     

UTSi CMOS: A Complete RF SOI Solution

Fully integrated frequency synthesizers are comprised of three major blocks: a voltage controlled oscillator (VCO), a phase locked loop (PLL) and a loop filter between them. In this paper we discuss the technology and design issues necessary to make fully integrated synthesizers capable of meeting the demanding specifications of GSM and CDMA systems. All elements of the synthesizer will be discussed. Two of the most difficult elements to integrate are the inductor and varactor in the resonant circuit of the VCO; we will discuss these devices at length. CMOS/SOI on a sapphire substrate has shown to significantly improve RF device characteristics. Reduced floating body effects; achievement of high Q on chip components; excellent isolation; and high performance RF circuits enable high performance fully integrated synthesizers on SOS substrates.     

基于高频高压交流母线多组输出直流电源的研制

本电源是基于高频高压交流母线具有多组输出的直流电源，它具有高达200kHz的开关频率，后级的整流电路由于高频交流母线的存在，使得变压器和电感的设计变得简单，滤波电容的选择也更容易。本电源由PFC电路提供400V的高压直流输入，再由MOSFET组成全桥逆变电路，在固定额率的PWM发生电路和IR2110 MOSFET驱动电路作用下，只加—个谐振电感就可实现开关管的零电压开通，可在大大降低开关损耗和噪声的同时实现直流交流的变换。整流部分采用倍流整流电路以提高原边电压的利用率，可输出低压大电流。由于采用肖特基管，—方面可使得二板管的损耗可以接受，另外—方面还避免了采用同步整流电路所面临的电路结构复杂和驱动困难。     

A synchronous switched capacitor filter [CMOS Si-gate implementation]

A new switched capacitor circuit is presented, realizing a moderate to high Q frequency emphasizing network. The original feature of this circuit is that its resonant frequency is equal to one half of the sampling frequency, and independent of the accuracy of the capacitor ratio or of any imperfection, both affecting only the Q factor. The gain is nearly proportional to the Q factor. An experimental circuit has been implemented in CMOS Si-gate technology with a programmable gain of 20 dB and 40 dB, corresponding to a Q factor of 8.6 and 79, respectively. Experimental results are in good agreement with the theory. Modifications of the basic circuit are proposed to cancel the effects of parasitic capacitances and to reduce the chip area.     

L6598高压谐振控制器及应用

L6598是将谐振变换控制电路与高压半桥驱动器结合在一起的单片IC,它适用于AC／DC适配器和需要谐振拓扑结构的场合,在应用中其外部所需的元件极少。文中介绍了L6598内部结构、引脚功能、单元电路工作原理及其在宽范围AC／DC适配器中的应用电路。     

Asymmetrical pulse-width-modulated resonant DC/DC convertertopologies

This paper presents asymmetrical pulse-width-modulated (APWM) DC/DC resonant converter topologies that exhibit near-zero switching losses while operating at constant and very high frequencies. The converters include a bridged chopper to convert the DC input voltage to a high-frequency unidirectional AC voltage, which in turn is fed to a high-frequency transformer through a resonant circuit. The bridged chopper has two switches that alternately conduct. The duty cycles of the conduction of the switches are complementary with one another and are varied to control the output voltage. Three resonant circuit configurations suitable for this type of control are presented. Frequency domain analysis of the converter is given, and performance characteristics are presented. Experimental results for a 48-5 V, 30 W converter show an efficiency of 88% at a constant operating frequency of 1 MHz     

A high voltage resonant inverter for dielectric discharge barrier cell plasma applications

Among the applications of dielectric barrier discharge cells (DBDCs), the generation of cold plasmas for the degradation of toxic organic compounds has received a great deal of attention in recent years. Normally, a DBDC can be energized by means of a high voltage power supply operating at line frequency. In this paper, the analysis, design and construction of a power resonant seriesinverter is presented; this inverter is aimed to operate at high-voltages/high-frequencies, and its suitability to excite a DBDC is investigated. The topological analysis of the inverter is carried out using the fundamental approximation technique, where the DBDC has been modelled as a capacitor whose terminals' voltage is provided by a pulse transformer. Both, the DBDC and the pulse transformer are represented in an RLC equivalent circuit. The resonant inverter is designed to operate in a region where the transfer function is load dependent. The series resonant inverter performance has been experimentally tested in a DBDC application, showing its effectiveness in the generation of the electron discharge by means of a charge/voltage figure of merit.     

基于Multisim 11的品质因数计算与仿真分析

品质因数Q作为描述谐振电路性能的一项重要参数,直接影响谐振电路的通频带和选择性等指标,因此对品质因数进行研究有助于准确理解电路的谐振特性。Q值定义有多种不同的表述方法,也可以从不同的角度计算Q值。在此从研究Q的物理本质出发,分别就Q的能量定义、电路固有参数、复杂谐振电路端口等效和电路选频性能等方面综合剖析品质因数的不同计算方法,揭示了各种方法间的联系及电路的储能或频率选择特性。最后结合Multisim 11仿真软件对工程中常用的RL-C并联电路中功率、电压与电流等参量进行交流分析和参数扫描分析,通过实例计算与仿真验证了公式的正确性。     

串联谐振型放电电源仿真分析

为了分析串联谐振型气体放电电源的影响因素,为设计高效、节能的放电电源提供仿真基础,采用PSpice仿真软件对影响负载电容谐振电压的电源参数、电阻参数和电感参数进行了参数扫描仿真分析。结果表明:电源幅值增加,谐振电压升高;电源频率等于谐振固有频率时,谐振电压最高;电阻越大,谐振电压越低;电感选择合适时,负载谐振电压最高。因此,在设计气体放电电源时,考虑减少电路电阻、选择漏感合适的变压器等。     

一种高精度快速响应欠压锁定电路设计

针对传统欠压锁定(UVLO)电路结构复杂和响应速度慢的问题,设计了一种高精度的快速响应欠压锁定电路.该电路整体均由CMOS管组成,结构简单且易于实现.采用电流模控制技术,随电源电压呈二次方曲线变化的自偏置电流控制阈值电压的产生,有效提高了电路的响应速度.该欠压锁定电路基于0.18μm BCD工艺设计,并利用HSPICE进行仿真验证,当电源电压在0～5V区间变化时,输出电压翻转的上阈值门限为3.91 V,相应下阈值门限为3.82V,迟滞量为90 mV,温度在-40～125℃范围变化时,阈值门限电压容差仅为0.9μV,可实现输出电压的高精度转换,电路面积仅为15 μm×48μm.     

Q/V频段高通量卫星通信系统抗雨衰设计

分析了高通量通信卫星系统的发展趋势,下一代高通量卫星的容量将达到1Tb/s,而其面临的挑战是现有的Ka频段频谱资源有限,因此需要将馈电链路从Ka频段迁移到频谱资源更多的Q/V频段。针对Q/V频段卫星通信系统可能遇到的问题--雨衰问题,详细分析现有的三种空间分集模式,从卫星载荷实现复杂程度、地面段投资成本分析每种模式优缺点。针对最为可行的N+P模式,展开其馈电链路可用度计算,并给出实现的关键技术--信关站切换策略。     

一种电流型二线制光照强度变送器的设计

现阶段对电流型二线制光照强度变送器的研究还相对较少,设计的光照强度变送器普遍存在精度不高,线性度不好,性能不够稳定,不能输出标准4~20 mA电流信号的问题。介绍了一种电流型二线制光照强度变送器的设计,其结构由光照强度转电压电路、电压范围转换电路、电压转电流电路以及稳压电源产生电路组成。实验结果表明该变送器具有精度高、线性度好、功耗低,能够稳定可靠地输出标准4~20 mA电流的特点。     

基于模块化多电平拓扑的谐振变换器设计

在海洋科学研究和海洋观测领域中,水下系统的供电方式大多是岸基负高压传输到海底接驳设备。海底接驳设备中的功率变换器将岸基电源的数千伏至十几千伏的直流高压转换成低压375 V供海底设备供电。针对变换器高电压输入、宽电压范围输入及输入输出电压变比大的技术难点,提出了模块化多电平的LLC谐振变换器拓扑结构,文中对变换器进行了模型搭建和电路仿真,并完成了一台40 kW工程样机的设计,最后根据仿真和实验结果验证了模块化多电平谐振变换器工作原理的正确性及可行性。     

Design and Application for PV Generation System Using a Soft-Switching Boost Converter With SARC

In order to improve the efficiency of energy conversion for a photovoltaic (PV) system, a soft-switching boost converter using a simple auxiliary resonant circuit, which is composed of an auxiliary switch, a diode, a resonant inductor, and a resonant capacitor, is adopted in this paper. The conventional boost converter decreases the efficiency because of hard switching, which generates losses when the switches are turned on/off. During this interval, all switches in the adopted circuit perform zero-current switching by the resonant inductor at turn-on, and zero-voltage switching by the resonant capacitor at turn-off. This switching pattern can reduce the switching losses, voltage and current stress of the switching device. Moreover, it is very easy to control. In this paper, we have analyzed the operational principles of the adopted soft-switching boost converter, and it is designed for PV generation system. Simulation and experimental results are presented to confirm the theoretical analysis.