高效率准谐振Buck变换器设计与研究

电感电流临界连续工作模式(BCM)Buck变换器,在电感电流下降到零时,输出滤波电感和开关管并联电容谐振即准谐振(Quasi Resonant)(QR)。在开关管两端电压谐振到零的时候开通开关管,则可以实现零电压零电流开通(ZVS/ZCS)。本文通过详细分析输出电感与开关管并联电容的谐振过程,得出开关管两端电压为零的时间,并且通过设计延时电路,以保证输入电压变化时依然能够实现零电压和零电流开通(ZVS/ZCS)。在开关管关断时由于开关管两端并联了谐振电容,可近似认为是零电压关断。而且Buck变换器工作于BCM模式时输出滤波电感体积小,动态响应速度变快,二极管自然关断,没有反向恢复损耗。最后设计了一台3kW的原理样机,最高效率可以达到98.7%。     

推挽正激整流及其应用

在传统的全波整流基础上，引入一个电容，提出了一种新颖的整流电路一推挽正激整流。文中分单极性和双极性两种情况对电路工作原理进行分析，揭示出这种整流电路的优点：①输出电感电流纹波小；②输出整流二极管无反向恢复电压尖峰；③可以实现所有开关管的ZVS开关；④减小了续流期间的导通损耗。理论分析和仿真结果表明推挽正激整流拓扑特别适用于作为“直流变压器”。基于以上分析设计的240W“直流变压器”原理样机效率高达97．1％，表明该整流方式具有优越的整机性能。     

开关电源整流电路功率因数校正的研究

详细分析了整流电路输入电流与输入电压之间存在相位差和功率因数低的原因。通过在整流输出端与电容之间增加一个Buck电路,分析了Buck型PFC拓扑电路的工作原理及电感电流的工作模式,通过控制该电路的开关管占空比大小的方法,使整流输出端呈阻性负载,迫使输入电流去跟随输入电压的相位。理论分析Buck电路的工作原理,仿真和试验验证了通过改变开关管的占空比能有效地实现功率因数校正。     

倍流整流ZVS PWM复合式全桥三电平变换器

本文提出一种倍流整流方式ZVS PWM复合式全桥三电平变换器，它可以在很宽负载范围内实现所有开关管的ZVS和输出整流管的自然换流，从而有效地消除输出整流管上的电压尖峰和振荡。该变换器还有利于减小输出滤波电感纹波电流和输出纹波电流，适用于宽输入电压范围场合。本文阐述该变换器的工作原理，并通过一台540W的原理样机验证该变换器的工作原理，最后给出实验结果。     

含耦合电感倍压单元的高增益DC/DC变换器

提出一种含耦合电感倍压单元的高增益DC/DC变换器。变换器的电压增益可通过调节耦合电感的匝比得到进一步提升。由输入电感和辅助电容可组成输入电流纹波吸收电路,通过合理配置电容参数可实现输入电流的零纹波,从而可降低滤波电感体积。变换器引入耦合电感倍压单元后,开关管不直接箝位于输出高电压,因此可实现开关管的低电压应力。此外,由箝位二极管和储能电容形成的电压尖峰吸收电路可有效降低漏感引发的开关管电压尖峰。分析了变换器的工作机理和稳态特性,并推导了零输入电流纹波满足条件和参数优化方案。最后,通过一台功率为100 W的实验样机进行了可行性验证。     

基于充电机的3kW移相全桥变换器

为了抑制输出整流二极管反向恢复引起的电压振荡,采用初级二极管箝位的电路拓扑设计移相全桥零电压开关(ZVS)变换器。通过改变移相角稳定输出电压,将开关管的结电容和外并电容与串接的电感作为谐振元件,实现开关管的ZVS。实验表明,该方案在实现软开关的同时,可以较好地抑制输出整流二极管上的电压振荡,减小输出整流二极管的电压应力。     

交错并联磁集成软开关双向DC/DC变换器的研究

交错并联磁集成软开关技术可以减小变换器输出电流纹波,提高动态响应,减小开关损耗。介绍了一种交错并联磁集成双向DC/DC变换器电路拓扑结构,该变换器具有开关器件电压应力低,输入输出电压变比大的优点。分析了变换器在Boost和Buck模式下的工作模态,并推导了稳态工作时的基本方程,获得了稳态电压增益,通过等效电感分析了输出稳态纹波与动态响应和集成电感耦合系数的关系,并给出了设计范围,利用阵列式磁芯设计了耦合电感,并给出了设计方法。采用交错并联磁集成技术,减小了输入输出电流纹波;给出了软开关的实现条件,可以实现所有开关管的零电压开关(ZVS)导通,减小了开关损耗。研制了原理样机,通过实验验证了理论分析的正确性。     

基于耦合电感倍压单元的零输入电流纹波高增益非隔离变换器

提出一种基于耦合电感倍压单元的零输入电流纹波非隔离型高增益DC-DC变换器。该变换器由零输入电流纹波Boost变换器和耦合电感单元组成,通过设计耦合电感电压比,实现了高升压增益特性。同时,采用无源无损吸收电路消除了漏感引起的开关管两端电压尖峰,降低了开关管的电压应力。通过增加由电容和二极管组成的倍压单元,进一步减小了开关管的电压应力,同时消除了输出二极管的电压尖峰,降低了二极管电压应力。因此,可通过选取低导通电阻、低电压等级的MOSFET,以降低变换器成本和开关管的导通损耗,提高变换器的效率。此外,还实现了变换器的零输入电流纹波,降低了输入滤波器的设计难度。文中详细分析了该变换器的工作原理及工作特性,给出了关键参数的设计原则。最后,通过实验结果验证了理论分析的正确性。     

一种低输入电流纹波高增益软开关DC-DC变换器

针对新能源发电系统输出电压低、电压稳定性差等问题，提出一种非隔离型低输入电流纹波高增益软开关直流变换器。该变换器结合有源钳位技术和耦合电感与二极管-电容倍压结构，提高了变换器的电压增益，降低了开关器件的电压应力。耦合电感自身漏感有效缓解二极管反向恢复问题，并通过有源钳位网络回收利用了漏感的能量，开关管无关断电压尖峰。利用耦合电感漏感，所有开关管均实现了零电压软开关，提高了变换器的效率。详细分析了变换器的拓扑结构与工作原理，并对电压增益、器件电压电流应力、软开关等电路性能进行了分析。最后，搭建了一台40 V输入、400 V输出、额定功率为160 W的试验样机，实验验证了该变换器具有低输入电流纹波、高电压增益、高变换效率和低电压应力等优点。     

新型零电流转换移相全桥DC/DC变换器

提出了一种新型零电流转换(ZCT)移相全桥DC/DC变换器拓扑。该变换器通过在原边增加一个由电容和电感构成的有源辅助电路,在开关管状态发生变化时,控制辅助电路的谐振电流,可实现主功率开关管和辅助开关管的零电流开关(ZCS),消除IGBT拖尾电流引起的开关损耗,同时减小了二极管的反向恢复损耗。辅助电路结构不会增加开关管的导通损耗,还能一定程度上克服传统零电压开关(ZVS)全桥变换器原边环流损耗大和占空比丢失严重的缺点。详细分析了该新型全桥变换器的工作原理以及实现零电流开关的条件,给出了主电路拓扑结构及相关参数选取,根据所选取参数对主电路进行仿真研究,给出了主要仿真波形,结果验证了电路分析的正确性和设计的可行性。     

Implementation of a Soft Switching Converter with High Input Voltage

This paper presents an interleaved zero voltage switching (ZVS) DC/DC converter with high input voltage applications. In order to reduce the voltage stress of MOSFETs, two half‐bridge zeta converters are connected in series at high voltage side. Thus, the voltage stress of MOSFETs can be clamped at one‐half of input voltage. Asymmetric pulse‐width modulation (APWM) is adopted to control power switches. With the resonant behavior by the leakage inductance of transformer and the output capacitance of MOSFET at the transition interval, MOSFETs can be turned on at ZVS. For each half‐bridge zeta converter, two series transformers are connected in series at the primary side and in parallel at the secondary side in order to reduce the current stress of secondary windings for high load current applications. Interleaved PWM scheme is used to control two half‐bridge converters in order to reduce the size of output filter inductor and capacitor due to the partial ripple current cancellation. Experimental results, taken from a laboratory prototype rated at 1 kW, are presented to demonstrate the converter performance. Copyright © 2012 John Wiley & Sons, Ltd.     

A new interleaved bidirectional dc/dc converter with zero voltage switching and high voltage gain: analyses,design and simulation

In this paper, a new interleaved non‐isolated bidirectional dc–dc converter with capability of zero voltage switching and high voltage gain is proposed. In the proposed converter by using two coupled inductors and one capacitor, the voltage gain is extended. Moreover, by using only an auxiliary circuit that includes an inductor and two capacitors, the zero voltage switching (ZVS) of two used switches in the first phase of converter can be achieved. The ZVS operation of two used switches in the second phase is always obtained without using any extra auxiliary circuit. This converter similar to other interleaved converters has low input current ripple and low current stress on switches. In this paper, the proposed converter is analyzed in all operating modes, and also the voltage gain, required conditions for ZVS operation of switches, voltage and current stresses of all switches, and the value of input current ripple in both boost and buck operations are obtained. Finally, the accuracy performance of the proposed converter is verified through simulation results in EMTDC/PSCAD software. Copyright © 2017 John Wiley & Sons, Ltd.     

一种新型零电压零电流开关三电平DC/DC变换器的研究

该文介绍了一种新型的带有简单辅助电路的零电压零电流开关（ZVZCS）三电平DC/DC变换器，它的辅助电路不含耗能元件和有源开关，可实现超前管的零电压开通和滞后管的零电流关断。耦合电感取代了常规滤波电感，它所感应出的电压由功率变压器反射到初级，使得变换器在零状态时的循环电流减小到零。通过改变耦合线圈的匝数比，可以任意设置用于电流回零的电压幅值的大小，调节电流回零的时间。文中介绍了该变换器的工作原理，讨论了设计参数。通过实验验证，该电路具有辅助电路简单、效率高、整流二极管承受的电压低和环流自动调节等优点，适用于高电压、大功率的应用场合。     

Implementation of parallel zero‐voltage switching converter with series‐connected transformers

This paper presents a parallel zero‐voltage switching (ZVS) DC–DC converter with series‐connected transformers. In order to increase output power, two transformers connected in series are used in the proposed converter. Two buck‐type converters connected in parallel have the same switching devices. The primary windings of series‐connected transformers can achieve the balanced secondary winding currents. The current doubler rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding. Thus, the current ripple on the output capacitor is reduced, and the size of the output choke and output capacitor are reduced. Only two switches are used in the proposed circuit instead of four switches in the conventional parallel ZVS converter to achieve ZVS and output current sharing. Therefore, the proposed converter has less power switches. The ZVS turn‐on is implemented during the commutation stage of two complementary switches such that the switching losses and thermal stresses on the semiconductors are reduced. Experimental results for a 528‐W (48 V/11 A) prototype are presented to prove the theoretical analysis and circuit performance. Copyright © 2011 John Wiley & Sons, Ltd.     

Novel interleaved ZVS converter with ripple current cancellation

This paper presents a zero voltage switching (ZVS) converter with interleaved pulse‐width modulation scheme. An active clamp circuit is adopted in the proposed converter to recycle the energy stored in the leakage inductor of the transformer and reduce the voltage stress of the main power switch in the converter. The ZVS feature of switches can be achieved due to the resonance during the transition interval of two power switches. Two full‐wave rectifiers with ripple current cancellation are connected in parallel at the output side to reduce the current stress of the secondary winding of transformers. Instead of the conventional interleaved forward converter, power switches in the proposed converter can perform the functions of both forward converter and active clamp at the same time. Therefore, the circuit components in the power circuit are less than that of in the conventional interleaved forward converter. The operation principle and system analysis of the proposed converter are provided. Some experimental results for a 240 W (12 V/20 A) prototype are provided to demonstrate the effectiveness of the proposed converter. Copyright © 2008 John Wiley & Sons, Ltd.     

Analysis and Implementation of an Interleaved ZVS Converter with High Input Voltage

An interleaved half‐bridge converter is presented for high input voltage application. The features of the proposed converter are zero voltage switching (ZVS) turn‐on for all active switches, ripple current reduction at output side, load current sharing and load voltage regulation. Two half‐bridge converters connected in series and two split capacitors are used to limit the voltage stress of each power switch at one‐half of input DC bus voltage. Thus, active switches with low voltage stress can be used at high input voltage application. On the other hand, the output sides of two half‐bridge converters are connected in parallel to share the load current and reduce the current stresses of the secondary windings and the rectifier diodes. Since two half‐bridge converters are operated with interleaved pulse‐width modulation (PWM), the output ripple current can partially cancel each other such that the resultant ripple current at output side is reduced and the size of output inductors can be reduced. In each half‐bridge converter, asymmetrical PWM scheme is used to regulate the output voltage. Based on the resonant behavior by the output capacitance of MOSFETs and the leakage inductance (or external inductance) of transformers, active switches can be turned on at ZVS during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The proposed converter can be applied for high input voltage applications such as three‐phase 380‐V utility system. Finally, experiments based on a laboratory prototype with 960‐W rated power are provided to demonstrate the performance of proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

Analysis of the ZVS two‐switch forward converter with synchronous current doubler rectifier

A soft switching two‐switch forward converter is presented to achieve zero voltage switching (ZVS) turn‐on of switching devices. In the adopted converter, a buck‐boost type of active clamp is connected in parallel with the primary winding of transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance between the transient interval of two main and auxiliary switches is used to achieve ZVS turn‐on of all switches. The current doubler synchronous rectifier is used in the secondary side of transformer for reducing the root mean square value of output inductor current, transformer secondary winding current and output voltage ripple by cancelling the current ripple of two output inductors. First, the circuit configuration and the principles of operation are analyzed in detail. The steady‐state analysis and design consideration are also presented. Finally, experimental results with a laboratory prototype based on a 380 V input and 12 V/30 A output were provided to verify the effectiveness of the proposed converter. Copyright © 2007 John Wiley & Sons, Ltd.     

A new non‐isolated free ripple input current bidirectional DC‐DC converter with capability of zero voltage switching

In this paper, a new nonisolated free ripple input current bidirectional dc‐dc converter with capability of zero voltage switching (ZVS) is proposed. The free ripple input current condition at low voltage side is achieved by using third winding of a coupled inductor and a capacitor for the whole range of duty cycles. In the proposed structure, the voltage conversion ratio can be more increased by adding the turn ratio of the second winding of the coupled inductor for the whole range of duty cycles. By adjusting the value of an auxiliary inductor in the topology of the converter, according to the power, the ZVS operation of the implemented 2 switches can be achieved throughout the whole power range. The mentioned features of proposed converter are validated theoretically for both boost and buck operations. In this paper, the proposed converter is analyzed for all operating modes. Moreover, all equations of the voltages and currents of all components, voltage conversion ratio, the required conditions for ZVS operation of switches, and also required conditions for canceling input current ripple at low voltage side are obtained. Finally, the performance of the proposed converter is reconfirmed through experimental and EMTDC/PSCAD simulation results.     

Analysis,design and implementation of a high‐voltage gain DC‐DC converter

An interleaved DC‐DC converter with soft switching technique is presented. There are two converter modules in the adopted circuit to share the load power. Since the interleaved pulse‐width modulation (PWM) is adopted to control two circuit modules, the ripple currents at input and output sides are naturally reduced. Therefore the input and output capacitances can be reduced. In each circuit module, a conventional boost converter and a voltage doubler configuration with a coupled inductor are connected in series at the output side to achieve high step‐up voltage conversion ratio. Active snubber connected in parallel with boost inductor is adopted to limit voltage stress on active switch and to release the energy stored in the leakage and magnetizing inductances. Since asymmetrical PWM is used to control active switches, the leakage inductance and output capacitance of active switches are resonant in the transition interval. Thus, both active switches can be turned on at zero voltage switching. The resonant inductance and output capacitances at the secondary side of transformer are resonant to achieve zero current switching turn‐off for rectifier diodes. Therefore, the reverse recovery losses of fast recovery diodes are reduced. Finally, experiments based on a laboratory prototype rated at 400 W are presented to verify the effectiveness of the proposed converter. Copyright © 2012 John Wiley & Sons, Ltd.     

Isolated high voltage‐boosting converter derived from forward converter

A novel isolated high voltage‐boosting converter, derived from the traditional forward converter, is presented in this paper. As compared with the traditional forward converter, the demagnetizing winding of the transformer in the proposed converter is used not only to demagnetize but also to improve the voltage conversion ratio. Therefore, the duty cycle is not limited, and the utilization of the transformer, also called coupled inductor, can be increased also. Furthermore, the proposed converter maintains the advantage of possessing a non‐pulsating output current, leading to a small output voltage ripple. Moreover, by applying one additional voltage‐boosting winding to the transformer, the voltage conversion ratio can be significantly improved. In addition, an active clamp circuit is employed in the proposed converter to reduce the voltage stress of the main switch, caused by the leakage inductance in the transformer, and the switches can achieve zero‐voltage switching. Finally, the analysis of operating principles, choice of the turns, turns ratio, core size, and each wire size of the coupled inductor are described in detail, and the experimental results with a prototype with 12‐V input voltage, 100‐V output voltage, and 100‐W output power are provided to verify the feasibility and effectiveness of the proposed converter. Copyright © 2015 John Wiley & Sons, Ltd.