一种带有软开关缓冲电路的变流器

为提高变流器的能量转移能力,降低控制电路的复杂性,提出一种适用于升压变流器的新的有源软开关缓冲电路。该电路利用辅助开关来参与能量转移;且升压变流器和缓冲器的开关能以零电压切换(ZV S)关断和零电流切换(ZCS)导通的方式工作。虽然流过升压变流器和缓冲器开关的电流不同,但这些开关在导通的大部分时间里并联运行,因此缓冲器开关参与了从电源到输出的能量转移。两个开关采用相同的控制信号和非隔离的门极驱动电路,控制电路十分简单、可靠。该方法通过一个3.2 kW升压变流器原型的实验结果得到证实。     

一种单开关软切换PWM正向变流器

提出了一种单开关软切换PWM正向变流器。这种单开关软切换PWM正向变流器工作时有源开关上无电压应力,电流应力很小。此变流器及其两个派生电路可工作在接近于无损耗的切换状态,基本实现开关器件零电流切换(ZCS)导通和零电压切换(ZVS)关断,其输出电压由脉宽调制式(PWM)技术控制。对这些变流器的工作原理作了详细分析,并用仿真和实验结果加以证实。     

基于E类放大器的松耦合电源的分析与设计

文章设计的松耦合电源是基于E类功率放大器电路改进,并对此电路拓扑进行电路分析,经去耦等效建模,将电路划分为四种工作状态,分别进行时域电路求解并画出理论波形。通过分析电路工作频率随耦合系数、开关导通时间改变的关系,以及输出功率与开关导通时间的关系,提出一种电流过零导通开关、并以电流平均值控制开关导通时间的功率控制策略,实现了功率输出的稳定性,并进行了实验验证。     

基于软开关技术的PWM变频调速系统

软开关电力电子技术利用在零电压（零电流)条件下控制开关器件的导通和关断,从而在理论上实现了开关器件的零损耗。介绍一个基软开关技术的PWM变频调速系统。利用8051单片机组成控制系统,来控制IGBT的导通和关断。在主电路中,采用辅助二级管谐振极PWM逆变器来实现软开关技术。     

一种PWM软开关变流器实现及损耗分析

零电流转换（ZCT）技术通过控制辅助电路的谐振,为开关器件创造零电流的开关条件.辅助电路的引入不会对主电路的控制算法产生影响,使得传统PWM控制策略能够直接应用在软开关变流器上.在分析ZCT软开关工作原理的基础上,引入的辅助电路损耗小于减少的开关损耗,ZCT技术提高变流器的整机效率.通过一台500 kVA三相ZCT软开关PWM软开关变流器互馈试验平台,完成了功率、软开关试验及不同谐振参数下的效率对比试验.试验结果表明,PWM变流器基本实现了开关器件的零电流转换,且谐振过程与理论分析基本相同,验证了谐振电流峰值与谐振周期对整机效率的影响.     

一种优化的反激式微逆变器有源钳位控制方式

针对反激式并网微型逆变器有源钳位电路,通过分析其工作过程,给出了反激输出侧二极管与辅助开关管体二极管的导通时刻以及两者导通先后顺序判断及其理论依据,提出了一种优化的控制方式.通过适时地控制辅助开关管的导通与关断,在实现主、辅开关管的零电压开关(ZVS)以及反激输出侧二极管的零电流开关(ZCS)的基础上,进一步实现主、辅开关管体二极管的ZCS,最大限度地降低了系统的开关损耗.最后,仿真结果验证了有源钳位控制方式的正确性.     

大功率用改进型ZCT-Boost DC/DC变流器

为了适应较大功率DC／DC变流器的需要,提出了一种改进型的零电流转换．脉宽调制Zero Current Transition Pulse Width Modulation,ZCT-PWM）Boost变流器。通过在电路中增加两个辅助开关管和两个小电感．运用简单的控制策略,不仅实现了变流器主管和两个辅管的ZCT,主管和辅管的电流应力较传统的零电流开关（zero Current Swith,ZCS）电路有明显减小,有效地减小了导通损耗,同时也实现了输出二极管的软换流,解决了二极管反向恢复的问题。文中将详细分析该变流器的工作原理,并通过实验结果验证理论分析。     

升压型Boost-PFC电路的频率反走临界电流控制

临界导通工作模式下的Boost PFC电路在交流输入电压过零点附近出现开关频率过高和过零点交越失真,导致电路开关损耗增加和总谐波失真增大,为此在恒定导通时间控制基础上,提出了一种电流控制频率反走的控制策略.通过在交流输入电压过零点附近将电路从临界工作模式切换到断续工作模式的方式,降低电路在交流输入电压过零点附近开关管的...     

改进型零电压转换PWM软开关功率变换器的实现机理分析

为改进传统谐振缓冲功率变换器(RSI)应用于高精度场合纹波较大的问题,提出一种改进型零电压转换(ZVT)脉宽调制(PWM)软开关功率变换器。通过LC环节减小输出电流纹波,并采用负载分段实现软开关的方式。轻载下利用交变的滤波电感电流实现主开关器件的零电压开通,重载下通过合理的导通谐振回路实现软开关,同时辅助开关器件实现零电流开关。该拓扑可采用PWM控制,具有效率高、纹波噪声小和开关频率固定的优点。通过分析电路的实现机理,对各工作时区进行解析计算,并给出实现软开关的条件。最后通过实验,在200kHz的开关频率下,验证了电路的有效性。相比于硬开关,效率得到了很大的提升,而相比于RSI在效率上虽有降低,但输出噪声却大幅减小。     

混合导通模式并网逆变器的直接电荷量控制方法

逆变器的不连续导通模式(discontinuous conduction mode,DCM)所需滤波电感量小,可以实现开关管的软开通,因而能够有效地提高逆变器的效率及功率密度。但是,DCM下电流应力较高。针对这一问题,该文采用T型三电平电路构建LCL型并网逆变器,并使逆变侧电感工作于混合导通模式(mixed conduction mode,MCM)。逆变器在负载电流较小时工作于DCM,在负载电流较大时工作于梯形导通模式(trapezium conduction mode,TPCM),从而在实现软开关的同时,有效地减小了电流应力。DCM与TPCM都可以实现固定开关频率,但基于传统的状态平均模型难以实现控制器的设计。该文提出一种以桥臂输出的电荷量作为控制变量的电荷量模型。该模型为线性化的二阶模型,大大简化控制器的设计。基于该模型,该文提出了一种定开关频率的直接电荷量控制方法。最后,通过仿真和实验,验证所提出的建模与控制方法的优越性。     

A lossless switching technique for smart grid applications

Smart grid is an upgrade of the existing electricity infrastructure in which integration of non conventional energy sources are an integral part. This leads to the introduction of harmonics and increased switching losses in the system. Thus there is a need of loss less switching techniques for smart grid applications. Switched mode power supplies (SMPSs) are being extensively used in most power processes [1]. Developments were carried out centered on hard switched converters, where switching frequency is limited to 10 s of kHz [2]. The uses of soft switching techniques, [3], [4], [5], [6] zero voltage switching (ZVS) or zero current switching (ZCS), is an attempt to substantially reduce the switching losses and hence attain high efficiency at increased switching frequency. The soft-switching topologies belong to families namely resonant load converters [3], resonant switch converters [2], [4], resonant transition converters [5], [6], and most recently active clamped PWM converters [7], [8], [9]. The active clamp topology adds an active clamp network, consisting of a small auxiliary switch in series with a capacitance plus the associated drive circuitry to the traditional hard switch converters. The proposed paper basically deals with the design, modeling and simulation of a ZVS–PWM active clamp/reset forward converter having features like zero switching power losses, constant frequency and PWM operation, Soft-switching for all devices and Low voltage stresses on active devices due to clamping action.     

A practical soft switching power supply with self-oscillating circuit and resonant converter using a cross transformer

Recently, soft switching power supplies using resonant converters have been attracting notice owing to their high efficiency and low noise characteristics. Conventional resonant-type converters have a complex control circuit, and we solved this problem by using a cross transformer. Various types of switching power supplies which have a simple structure can be realized by a combination of a self-oscillating driving circuit and a resonant converter. This paper presents our development process and describes the latest technology of soft switching power supplies making use of super-small-sized cross transformers. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 121(1): 60–69, 1997     

A DC voltage converter with a series resonant inverter and asymmetric control of power transistors

The interest in dc converters with a series resonant inverter (resonant converters) is due to the fact that they easily realize switching of semiconductor devices at zero current and zero voltage in a device. This makes it possible to significantly reduce power losses during switching of semiconductor devices and to realize the operation of a dc–dc converter at higher frequencies with a high efficiency. In the foreign literature, many circuits of resonant converters are described and many results of experimental studies are presented. However, the theory of such converters has not been sufficiently developed and theoretical studies are conducted using approximate methods, for example, fundamental-harmonic method. This paper describes the operating principle of the power part of a dc–dc converter with a series resonant inverter with asymmetric control in the discontinuous conduction mode (DCM), when the switching frequency is less than the resonance frequency of the LC circuit. The features of symmetric and asymmetric control of the inverter’s power transistors are described, in which bipolar current pulses are formed in half of the switching period. An algorithm for asymmetric control of transistors is proposed, and a scheme for implementing this algorithm on discrete components in the form of a virtual model in the Matlab–Simulink environment is presented. The results of modeling (transient and steady-state conditions, external characteristics, and other dependences), as well as the results of a comparison of the taken and theoretical (constructed from analytical relationships) characteristics, are presented.     

高压变压器寄生电容对串联谐振变换器特性的影响

高压串联谐振变换器广泛应用于电容器充电、静电除尘等系统中。然而,高压变压器寄生电容的存在,使得客观上并不存在理想的高压串联谐振变换器。定量分析了高压高频变压器的寄生电容对工作于断续谐振电流模式(discontinuous current mode,DCM)的串联谐振变换器特性的影响,这些特性包括临界断续谐振频率、归一化输出电流和软开关。当考虑高压变压器寄生电容后,串联谐振变换器实际上已经演变为LCC串并联谐振变换器。通过对DCMLCC谐振变换器在不同工作阶段的数学分析、推导和归一化处理,得到了具有封闭形式的电路特性的表达式。通过分析发现,随着等效电压增益的增加,DCM LCC谐振变换器的正向和反向谐振过程均由两元件谐振向三元件谐振过程转变,临界断续频率升高。以图形曲线的方式给出了量化的分析结果。通过比较两类典型的控制方法可知,第二类典型控制方法具有更高的电流输出能力和能量传输效率,是一种优化的控制方法。所得分析结果可为工作于断续谐振电流模式的高压串联谐振变换器的设计提供参考,特别对电容充电和静电除尘电源具有工程应用价值。     

输入并联输出串联LCC变换器的设计

LCC串并联谐振变换器较之其他形式的谐振变换器能更有效利用高压变压器的漏感和寄生电容实现软开关,并且能更大范围地调整输出电压,从而更加适用于高压电源.提出了一种输入并联输出串联LCC变换器的设计,分析了软开关实现的条件.所设计的变换器采用了主从控制方法,主模块采用脉冲频率调制,从模块采用脉冲频率调制结合脉冲跨周期调制,...     

Soft‐switching converter with low circulating current and wide range of ZVS turn‐on

In this paper, a new hybrid dc–dc converter with low circulating current within the freewheeling interval, wide range of zero‐voltage switching and reduced output current ripple is presented. The proposed hybrid circuit includes two three‐level pulse‐width modulation converters and a series resonant converter with the shard lagging‐leg switches. Series resonant converter is operated at fixed switching frequency (close to series resonant frequency) to extend the zero‐voltage switching range of lagging‐leg switches. The output of series resonant converter is connected to the secondary sides of three‐level converters to produce a positive rectified voltage instead of zero voltage. Hence, the output inductances can be reduced. The reflected positive voltage is used to decrease the circulating current to zero during the freewheeling interval. Therefore, the circulating current losses in three‐level converters are improved. Finally, experiments are presented for a 1.44 kW prototype circuit converting 800 V input to an output voltage 24 V/60A. Copyright © 2015 John Wiley & Sons, Ltd.     

三种BUCK谐振型PWM DC/DC变换器的比较

谐振型PWM软开关变换器具有工作频率高、效率高、电磁干扰小、控制和调节特性好等优点,已经成为软开关变换器的研究热点。以三种谐振型PWM软开关BUDK电路为例,从拓扑结构、开关损耗及电压电流应力等几方面进行分析比较。     

一类改进的恒频PWM型并联谐振交流器

对传统的并联谐振交流器拓扑结构加以改进，新一类交流器包括两种不同的电路结构，输出电压的调节采用恒频脉宽调制方式。文中通过电路分析、计算机仿真和一台１００ｋＨｚ、２４Ｖ／１００Ｗ变流器的电路实验，以证实改进后变流器所具的优点     

降低整数阶无线电能传输谐振频率的分数阶方法

针对谐振无线电能传输谐振频率高而电力电子器件目前较难实现高频大功率开关变换器的问题,提出一种基于分数阶原理降低无线电能传输谐振频率的方法,建立SS型分数阶无线电能传输系统的电路模型,推导其输出功率和传输效率的表达式,通过Matlab数值仿真分析分数阶元件的阶数对谐振无线电能传输参数及特性的影响。研究结果表明,采用分数阶电感、电容元件,可以大幅度降低谐振无线电能传输系统的谐振频率,从而降低开关器件的开关频率,且可以输出比整数阶无线电能传输系统更大的功率。     

非对称半桥交错并联输出式LLC谐振DC-DC变换器设计

LLC谐振变换器由于谐振特性,能够较容易实现软开关和增大变换器功率密度,在中大功率场合得到广泛应用。为了增大功率密度提高输出容量,设计了一种非对称半桥交错并联输出式LLC谐振DC-DC变换器,对变换器的工作过程进行了分析。分析了不同k值对变换器的影响,对谐振网络进行了等效分析。不同谐振频率下变换器分布在不同的工作区域,不同的工作区域中开关MOS管实现软开关过程的难易程度不等。通过仿真和样机测试验证了设计的变换器开关管能够实现零电压开关(ZVS),能够有效减小变换器的开关损耗。