采用磁集成技术的有源箝位正激变换器设计

针对3.3 V/10 A低压大电流输出、高功率密度电源模块的设计要求,结合有源箝位正激拓扑理论和磁集成技术,提出采用磁集成技术的有源箝位正激变换器;对变换器中的主变压器和输出电感进行集成,得到高效率、高功率密度的有源箝位正激变换器。     

交错并联有源籍位ZVS-PWM正激变换器的分析与设计

提出一种交错并联有源箝位ZVS-PWM正激变换器,它的最大优点是负载从零变化到最大时开关管的损耗非常小.这种变换器是由两个有源箝位正激变换器共同耦合一个高频变压器构成的,适用于大输入电压、大功率的变换器.分析其工作原理并用一台功率为3 kW的原理样机进行实验验证.     

准谐振正激变换器零电压开关设计

准谐振有源箝位正激变换器的有源箝位电路与常规的有源箝位正激变换器的结构类似,但实际工作过程存在许多差异。通过分析准谐振有源箝位正激变换器的工作过程,研究了准谐振有源箝位正激变换器的开关管零电压导通的边界条件,并进行了仿真和实验验证。     

有源箝位正激变换器的机理研究及优势

有源箝位正激变换器有很多优点,现在正得到广泛应用。本文介绍了有源箝位技术的工作原理与主要参数的设计方法,以及应用于正激变换器中的优势。     

峰值电流控制的磁集成有源箝位正激变换器的小信号模型

文章对采用峰值电流控制的磁集成有源箝位正激变换器进行了小信号分析。建立的模型不但包括复位电路和斜坡补偿电路部分,还包括集成磁件部分。最后给出了补偿器设计原则,完成了闭环设计。     

非理想条件下有源箝位正激电路小信号模型分析

有源箝位正激变换器相对于其它复位方式,有很多优点,然而当输入源和负载发生变化时,却造成系统的不稳定性。文中分析了有源箝位正激变换器中复位电容对其小信号特性的影响,在考虑原边主管导通电阻的基础上,应用状态空间平均法,首次推导其小信号模型,并运用Mathcad仿真了该模型的频率特性,结合控制理论根之和的概念,分析了非理想条件下的有源箝位正激电路的小信号模型。     

基于LM5025的有源箝位反激变换器的前馈控制

在有源箝位反激变换器负载基本恒定的情况下采用前馈控制既可以减小变换器体积,又可降低变换器的成本。文中在分析有源箝位反激变换器工作原理的基础上,结合LM5025器件的前馈控制特性,深入研究了基于LM5025的有源箝位反激变换器前馈控制的实现方案,设计了前馈控制电路的参数,完成了有源前馈反激变换器电路设计。在此基础上进行了实验研究,实验结果证明了有源箝位反激变换器前馈控制的有效性和实用性。     

具有非线性电压转换有源箝位正激变换器

本文研究一种具有非线性电压转换的正激变换器,通过在有源箝位正激变换器的变压器二次侧增加一个续流二极管和一个输出滤波电感得到。该变换器保留了有源箝位正激变换器的优点,同时,具有更高的占空比利用率,使得其具有宽输入电压适应范围,软开关的实现和二极管电压电流应力的减小,使其功率转换效率进一步提高。研制了一台50~100V输入, 12V输出的原理样机,实验结果验证了理论分析的正确性以及该技术的可行性。     

同步整流技术的研究

介绍了同步整流技术的基本原理,结合具体电路,对栅极电荷保持技术在有源箝位正激变换器中的应用作了分析;阐述了同步整流芯片IR1176在正激变换器中的应用。     

一种新颖有源箝位ZVS正激变换器的研究

介绍了一种中心抽头全波整流有源箝位ZVS正激变换器的工作原理及主要参数计算。有源箝位电路由一个箝位开关管和箝位电容组成。变压器磁芯实现无损复位,励磁能量和漏感能量全部传递到负栽.磁芯利用率高,功率开关管承受电压应力降低。通过变压器漏感与开关管输出电容的谐振,主开关管与箝位开关管都可以实现ZVS开通,提高了变换器工作效率。文章首先分析了变换器工作原理,然后给出了主要参数的计算方法,最后通过样机(48V输入5V/20A输出)实验验证了该拓扑的高效性能。     

Large-signal transient analysis of forward converter withactive-clamp reset

The forward converter with the active-clamp reset offers many advantages over the forward converters with other transformer-reset methods. However, during the line and load transients, the maximum magnetizing current of the transformer and the peak voltage of the primary switch are strongly affected by the active-clamp circuit dynamics. As a result, the design of a forward converter with the active-clamp reset cannot be optimized based only on its DC characteristics. Due to the nonlinearity of the circuit, it is very difficult to derive the closed-form equations for the transient response of the active-clamp circuit. In this paper, an average-state-trajectory approach is proposed to analyze the transient behavior so that the trends of the maximum magnetizing current of the transformer and the peak voltage of the primary switch can be easily predicted under worst-case conditions and parameter variations     

Analysis of a Zero-Voltage Switching Converter With Two Transformers

This brief presents an active-clamp zero-voltage switching converter. Two transformers connected in series are used, and each transformer can be operated as an inductor or a transformer. No output inductor is needed. An active-clamp circuit is used to recycle the energy stored in the transformer leakage. The system analysis, operation principles, and design equations of the proposed converter are provided. Experiments based on a laboratory prototype are also provided to confirm the converter performance     

Evaluation of synchronous-rectification efficiency improvementlimits in forward converters

Design trade-offs for different implementations of the forward power converter with synchronous rectifiers are presented, and effects of the synchronous rectifier driving method on the conversion efficiency are evaluated. Specifically, the merits and limitations of the RCD-clamp and active-clamp reset approaches for a power converter with self-driven synchronous rectifiers are discussed. Estimates of the upper limits of the efficiency improvements of the discussed synchronous rectification approaches relative to the Schottky diode implementation are derived. Finally, experimental comparisons of efficiencies for an offline, 3.3 V/20 A forward power converter power stage are presented and compared with the theoretically estimated ones     

A double ZVS-PWM active-clamping forward converter: analysis,design, and experimentation

This paper presents an isolated DC-DC converter based on two ZVS-PWM active-clamping forward converters connected in series and coupled by a single high-frequency transformer. The proposed converter features no switching losses from no-load to full-load operation and low conduction losses. This converter is suitable for high input voltage (>400 VDC) and high power applications. Operation principles, theoretical analysis and design example, are presented, as well as experimental results taken from a 3 kW laboratory prototype     

High Step-Up Active-Clamp Converter With Input-Current Doubler and Output-Voltage Doubler for Fuel Cell Power Systems

A high-efficiency high step-up dc–dc converter is proposed for fuel cell power systems. The proposed system consists of an input-current doubler, an output-voltage doubler, and an active-clamp circuit. The input-current doubler and the output-voltage doubler provide a much higher voltage conversion ratio without using a high turns ratio in the transformer and increase the overall efficiency. A series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the rectifying diodes. The active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. The operation principle of the converter is analyzed and verified. A 1 kW prototype is implemented to show the performance of the proposed converter. The prototype achieved a European efficiency of 96% at an input voltage of 30 V.      

Bipolar Narrow-Pulse Generator With Energy-Recovery Feature for Liquid-Food Sterilization

This paper presents a bipolar narrow-pulse generator with energy-recovery feature for liquid-food sterilization. The generator is formed from a bidirectional flyback converter and active-clamp circuits which are further simplified to the proposed topology with the synchronous-switch technique. In the converter, the leakage inductance of the transformer will resonate with the active-clamp capacitors to recover the trapped energy and to reduce switching loss, improving efficiency by about 13%. In addition, the capacitors can reduce voltage stress significantly. Experimental results obtained from a prototype with the output of plusmn6-20 kV, depending on loads, and the peak power of 1.2 MW has confirmed these discussions.     

Magamp postregulators for symmetrical topologies with emphasis onhalf-bridge configuration

The authors point out the major differences between symmetrical topology magamps and the forward converter magamp. In a forward converter, a small portion of the magnetizing current of the power transformer is diverted to the secondary for reset of the magamp's saturable reactor. In symmetrical topologies, the transformer's magnetizing current is not used for reset of the saturable reactor(s). The magnetizing current shifts to the secondary where it causes a series of problems. The authors examine these problems, identify solutions, and explain why a half-bridge magamp supply is inherently less versatile than is the forward converter