基于反激式开关电源升压电路的改进

已被广泛采用的升压式DC—DC变换器的体积比较大,并且升压比小。文中提出了一种基于自耦变压器升压方式的反激式电路,此电路具有结构简单、体积小、升压比大、效率高等优点。分析了其工作原理,并在理论基础上．实验验证了一种升压300V的反激式DC—DC变换器,证明了自耦变压器升压的反激式电路的可行性。     

Active clamp dual-end convertor

An active clamp dual-end convertor is proposed to achieve zero voltage switching for all switches with low voltage stress and eliminate the DC current component in the transformer. A 40 W prototype is built and the experimental results are obtained for verification     

频率计算法设计RCC开关电源

RCC称为自激式反激变换器,是中小功率开关电源最常用的设计方式之一。但设计RCC开关电源时,因各参数的互相影响,使计算、调试复杂。而传统的预选频率,后进行AP校验法需多次计算,所设计的系统难于工作在最佳状态。在开关电源设计中变压器设计是重点,变压器设计最重要的参考量是工作频率。若能预先计算出电源工作频率,或至少确定影响频率的因素,将大大减少计算和调试的时间。首先推导出频率计算公式,确定频率主要与初、次级电感量和输入电压的关系,并进一步确定变压器参数,最终确定电源的其他参数。最后通过对电源硬件的简单调试,验证设计的合理性。     

Three phase high frequency DC-DC convertor

A three phase system in a high frequency DC-DC convertor is proposed. Potential advantages of such an implementation include smaller magnetic parts, much lower output and input ripple, higher transformer utilisation factor and efficiency, and lower AC voltages for the same DC output voltage. There are also some disadvantages. More switchers and rectifying diodes are required. A three phase transformer and master oscillator at high frequencies are also necessary.<>     

Regulated self-oscillating convertor with auxiliary feedback circuit

A regulated self-oscillating transformer-coupled d.c./d.c. convertor is presented which has an auxiliary feedback loop to sustain self oscillations. While this circuit retains the inherent simplicity of self-oscillating circuits, it avoids certain starting problems which are usually encountered if transformer coupling is inserted into the self-oscillating feedback loop.     

Nondissipative switched networks for high-power applications

The letter seeks to extend the concepts of active-filter theory to high-power applications. Current-fed switched-capacitor networks and voltage-fed switched-inductor networks are efficient topologies suitable for high-power operation. Passive and active switched networks realised include the transformer, gyrator and a negative inductor using a generalised impedance convertor.     

等离子体中频电源的驱动与保护电路设计

讨论了150 kHz等离子体中频电源的驱动与保护电路设计方案。该电路采用脉冲变压器耦合MOSFET管驱动电路,具有输出变压器原边平均电流和副边峰值电流的过流保护功能。结果表明:驱动波形的上升和下降时间都不超过80 ns,并能在检测到过流信号时封锁驱动信号,关断变换器中的开关器件,切断过流故障,有效进行电路保护。     

基于波形相似度的水电站电流饱和变压器保护装置设计

为解决传统水电站电流饱和变压器保护装置保护及时率低的问题,基于波形相似度设计水电站电流饱和变压器保护装置。计算水电站电流饱和变压器保护运维动态基线,补偿水电站电流饱和变压器保护功率因数,基于波形相似度,分析水电站电流饱和变压器保护信号,采用NBC叠片式弹片,设定水电站电流饱和变压器保护装置额定电压,实现水电站电流饱和变压器保护装置设计。设计实例分析,结果表明,设计的保护装置保护及时率明显高于对照组,能够解决传统保护装置保护及时率低的问题。     

基于P89C669微控制器的MODBUS协议转换器设计与实现

基于P89C669微控制器和计算机数据通信技术,设计了MODBUS协议转换器,实现了MODBUS网络的主控设备与RTU(远程终端单元)之间的数据转换,并在电力系统220 kV主变风冷控制中用于变电所站内自动化监控计算机系统的MODBUS网络和PLC(可编程逻辑控制器)的数据通信,使站内自动化监控系统可根据主变油温、负荷电流等运行参数对风冷机组和油泵进行实时调控。     

基于等效法的电容式电压互感器铁磁谐振试验研究

并联在电容式电压互感器（简称CVT）中间变压器二次绕组上的阻尼器,是抑制CVT铁磁谐振的关键。在产品的例行试验及型式试验中,均需要对CVT产品进行铁磁谐振试验,以验证阻尼器的设计是否正确。但800kV及以上电压等级产品的铁磁谐振试验瞬间会对试验设备产生较高冲击。本文通过对等效法铁磁谐振试验的研究,避免了在施加较高电压下进行铁磁谐振试验对试验设备造成的伤害。     

Saturation-mode CMOS transconductor with enhanced tunability and low distortion

A new transconductor based on MOS transistors operating in saturation is presented. Linearisation is based on an offset biased pair in a cross-coupled configuration. Simulation results show that the proposed convertor combines excellent tuning characteristics with a large signal handling capability.<>     

Advanced Control of a Resistance Spot Welding System

This paper deals with a middle-frequency resistance spot welding system. It consists of an input converter, welding transformer, and a full-wave rectifier mounted at the transformer secondary. The welding current at the full-wave rectifier output is normally controlled by the pulse width modulated primary voltage of the transformer supplied by the input converter. The unequal ohmic resistances of the two transformer's secondary circuits and the different characteristics of the diodes of output rectifier certainly lead to the magnetic saturation which, consequently, causes the unwanted spikes in the transformer's primary current and over-current protection switch-off. This disadvantage of classical spot welding systems is completely eliminated by the proposed advanced hysteresis controller (AHC), which keeps transformer iron core saturation within prescribed bounds regardless of how unequal the ohmic resistances and diodes' characteristics in the transformer's secondary circuits are. This is achieved by a combined closed-loop control of the welding current and closed-loop control of the iron core saturation level. The proposed AHC assures a very short rise time of the welding current and the best possible utilization of the transformer iron core.     

基于电流型脉宽调制器的自适应反激驱动开关电源的设计

分析了一种采用3844B电流型脉宽调制器控制,实现多路输出的单端反激式大功率IGBT驱动电源。根据控制芯片特性与输出要求给出了详细的电路参数,设计了符合要求的高频变压器,提出改进的反馈控制方法,具有很强的自适应性。实验结果表明,该电源的可靠性更高,稳定性好,输出纹波小,能够适应规定电网电压波动195V到265V的要求,甚至更大的电压波动。     

A novel approach to the design of a transistorized inverter- converter operating at higher-than-audio frequencies

In this paper we describe some of the design and operating characteristics of an unusual 5-Kw 25kHz transistorized invertor- convertor, in which the high-power switch consists of a series arrangement of low-power transistors. The dc voltage is obtained from the three-phase line by voltage tripling rectification in each phase, thus avoiding a 60-Hz transformer. The resulting supply is exceptionally compact, light weight, and inexpensive. In contrast to most solid-state circuits, this supply is found to be extremely resistant to reactive voltage `spikes' attendant to the excitation of inductive loads. We also discuss the advantage in reliability resulting from the series arrangement of the transistors.     

A Computer Model of Magnetic Saturation and Hysteresis for Use on SPICE2

Magnetic saturation and hysteresis are simulated on SPICE2 using a model containing two nonlinear controlled sources. The model is applied to inductors and transformers made from a variety of core materials, and procedures are given for determining the model parameters directly from magnetic core catalog data. Four examples of circuit applications are given: a saturating instrumentation transformer, a saturating snubber inductor, a ferroresonant regulator transformer, and a Royer saturation oscillator.     

Transformer Computer Design Aid for Higher Frequency Switching Power Supplies

A transformer computer design aid is presented that was developed for use at switching frequencies above 100 kHz where the classical method of using the saturation constraint results in an over-heated transformer due to excessive core loss. Flux density is selected instead by an optimization procedure that minimizes total transformer losses. Key equations used in the design procedure are developed. Emphasis is placed on the algorithm used in the transformer design procedure.     

A zero-voltage and zero-current switching full bridge DC-DCconverter with transformer isolation

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the leading leg. It has a simple and robust structure, and load current control capability even in short circuit conditions, The possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC-DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12 kW prototype designed for welding application was verified by experiments     

New constant frequency PWM dual convertor with synchronous rectifier

A new constant frequency PWM dual convertor which has fully regulated dual outputs is proposed. The proposed convertor is the superposition of a forward convertor and a flyback convertor. The switches in the forward convertor for synchronous rectification provide another degree of freedom in controlling the flyback convertor. Thus, not only forward output but also flyback output can be fully regulated by constant frequency PWM control in continuous conduction mode (CCM).<>     

Improvement on current limiting performance of current limitingdevices with damping coils

An improved model of the current limiting devices such as the high-Tc superconducting fault current limiter (SFCL) and the reactor have been developed. The high-Tc SFCL mainly consists of the primary copper coil, the secondary high-Tc superconducting rings, and the damping coils, which are magnetically coupled through a three-legged magnetic core. Because a portion of the magnetic flux above the saturation point generated by the fault current is cancelled by the damping coil, thereby the magnetic core is prevented from getting into the saturated state. The limiting current level and the saturation of the core could be controlled by the air-gap length of the central leg with the damping coil. A new design of the SFCL is found to increase the effective impedance by about 60 to 70%, compared to the SFCL design without the damping coils     

Characterization of an active clamp flyback topology for powerfactor correction applications

Flyback derived power convertor topologies have long been attractive because of their relative simplicity when compared with other topologies used in low-power applications. Incorporation of active clamp circuitry provides the additional benefit of recycling transformer leakage energy while minimizing switch voltage stress. This paper presents the analysis, design, and experimental results of 500 W single stage and 600 W interleaved active clamp flybacks used for power factor correction. Several practical issues, including the application of charge control, the use of mixed power devices, and a solution to the hold-up time problem are discussed and experimentally verified