Analysis and implementation of active clamp SEPIC converter with synchronous rectifier

An active clamp SEPIC converter with synchronous rectifier is presented to achieve zero voltage switching (ZVS). The active clamp circuit is adopted in the proposed converter to absorb the energy stored in the leakage inductance of the transformer and limit the peak voltage stress on the switching devices. The resonance during the transition interval between the switching devices will help the power switches to turn on at ZVS. Therefore, the switching losses of switches are effectively reduced. The synchronous rectifier is used at the secondary side of the transformer to further reduce the conduction loss. The principle of operation and the steady-state analysis of the proposed converter are presented. Finally, the experimental results taken from a laboratory prototype with 240 W (12V/20A) rated power are presented to verify the effectiveness of the proposed converter.     

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。     

新型恒频ZCS/ZVS准谐振变换器电路设计及实验分析

提出了一种新型恒频率ZCS/ZVS准谐振变换器，其性能优于其它变换器。它具有较小开关损耗、较好的可控性、高操作性能、能够获得可以调节的直流输出电压等优点。并给出这种变换器的电路设计、实验波形以及实验结果分析。     

双输出升压型转换器LT3466

LT3466是凌特公司生产的一款全功能双输出升压型DC／DC转换器．可驱动多达20个白光LED，并具有软启动、LED开路保护及欠压闭锁等功能。文中介绍了LT3466芯片的结构特点、工作原理、设计方法及应用电路。     

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。     

Analysis and implementation of a dual-output LLC resonant converter

This article analyses and presents an LLC resonant converter with a high power factor for LCD-TV applications. It integrates the advantages of power factor correction and the LLC resonant converter. It can improve not only power quality but also circuit efficiency. Since the power factor corrector is used in the first stage of the LLC resonant converter, it is suitable for wide input voltage range application. On the basis of the resonant behaviour, zero voltage switching is achieved for the power switches and ZCS is achieved for the rectifier diodes. An experimental prototype of 90–260V _rms input and 12V/10A and ?12V/10A outputs with 92.6% efficiency for 32″ LCD-TV application is built in the laboratory to verify the operation principle of the adopted converter.     

Multiple switching-mode series-resonant half-bridge converter for a wide load range

In this article, a multiple switching-mode series-resonant half-bridge (SRHB) dc–dc converter is presented. The proposed multiple switching scheme changes switching modes to improve power efficiency for a wide output range, especially in the low output power range. This multiple switching scheme is composed of three different switching modes depending on the output power. The prototype was implemented using a single-chip microcontroller. With the multiple switching mode, high efficiency is achieved over an entire output power region. Experimental results on a 1.2?kW prototype are presented to confirm the performance of the proposed multiple switching scheme for an SRHB converter.     

Electron-beam fabricated titanium and indium tin oxide position-sensitive detectors

This work reports on the development of an optical position sensitive detector (PSD) which exhibits highly linear output characteristics comparable to complex multilayer sensors and which is based on a simple, two-stage fabrication procedure. Further advantages of this device include the potential for large-area surfaces and the production of comparatively large output signals requiring no amplification or external biasing. Most of these studies were carried out on a Schottky barrier (SB) structure based on crystalline p-silicon and electron-beam evaporated titanium and operated under focused white light. As a comparison of output behaviour, a second testing run was carried out using a red laser diode. The devices had metal layer thicknesses ranging from 2000Å to 180Å and results showed that the highest sensitivities and lowest nonlinearities occurred with PSDs having thinner titanium films. The overall best results were obtained using white light in photovoltaic mode, i.e. with no external biasing. Additionally, we compared these titanium devices to electron-beam deposited indium tin oxide (ITO) devices, and found that the ITO series had much lower outputs and higher nonlinearities. These latter devices were considered to be heterojunction structures of n-ITO/p-Si.     

Current control in high-efficiency unidirectional converter for fuel cell

This paper presents a model to implement the switching technique of a novel isolated DC/DC converter of full-bridge to link fuel cell power output to the distribution system. The implementation was performed on a DSP F2812 of Texas Instruments. It is also proposed a new start-up system (software), to avoid overcurrent on the input side of inverter. This software avoids using an auxiliary circuit for start-up, so reducing costs, improving volume and weight and maintaining the same efficiency. A prototype has been implemented to validate the performance. Finally, comparative experimental results are presented.     

Design and analysis of switched-coupled-inductor switched-capacitor step-up DC-DC converter

The study presents a high-gain closed-loop configuration of switched-coupled-inductor switched-capacitor (SCISC) converter via integrating with a pulse-width-modulation-based (PWM) controller for the goal of step-up DC-DC conversion/regulation. The SCISC power part consists of switched-coupled-inductor booster (SCI booster) and switched-capacitor tripler (SC tripler), and the step-up voltage gain is performed by using appropriate duty ratio D of PWM and turn ratio n of coupled inductor. Although increasing n or raising D makes a higher gain, it often results in the larger weight/volume or magnetic bias/saturation of coupled inductor. Here, the SC tripler can provide for an extra gain to ease these stresses of the coupled inductor. Further, this controller is engaged not merely in doing topological operation and timing, but in enhancing output regulation and/or output robustness (against source/loading variation). The related studies are demonstrated as follows: modelling, steady-state response, voltage conversion ratio value, power efficiency, capacitance/inductance selection, system stability and control design. At the end, the simulation results are obtained to check the design/analysis validity, and the experimental results are verified on the prototype of SCISC to display the effect of the proposed scheme.     

基于UCC2892和LTC3900的开关电源设计

有源钳位正激变换器可以实现零电压开关（ZVS）,降低功率开关损耗;同步整流可以提高低压大电流输出的开关电源的效率。介绍了一种基于有源钳位脉宽调制控制器UCC2892和同步整流控制器LTC3900的正激开关电源设计。     

Parallel full-bridge converter with wide ZVS and low freewheeling current

The main objective of this paper is to present a direct current to direct current topology with high circuit efficiency. In this studied circuit, two full-bridge circuits and a half-bridge circuit connected in parallel are introduced to achieve the advantages of low switching loss, less primary current, low conduction loss and low filter size compared to the traditional parallel full-bridge converters. The circuit diagram, operation principles, steady-state analysis and experiments are provided to demonstrate the effectiveness of the studied topology. Finally, a 1.44-kW laboratory prototype is constructed to verify the validity of the theoretical analysis. Experimental results show that highest efficiency of 95.3% can be achieved.     

一种新型软开关DC-DC PWM升压变换器设计

为提高转换效率并降低电源开关的电流应力,提出一种基于新型有源缓冲电路的PWM DC-DC升压变换器。该有源缓冲电路使用ZVT—ZCT软开关技术,分别提供了总开关ZVT开启及ZCT闭合、辅助开关ZCS开启及ZCT闭合。消除了总开关额外的电流及电压应力,消除了辅助开关电压应力,且有源缓冲电路的耦合电感降低了电流应力。另外,通过连续将二极管添加到辅助开关电路,防止来自共振电路的输入电流应力进入总开关。实验结果表明,相比传统的PWM变换器,新的DC-DC PWM升压变换器在满负荷时电流应力降低且总体效率能达到98.7%。     

Quasi-multi-pulse voltage source converter design with two control degrees of freedom

In this article, the design details of a quasi-multi-pulse voltage source converter (VSC) switched at line frequency of 50 Hz are given in a step-by-step process. The proposed converter is comprised of four 12-pulse converter units, which is suitable for the simulation of single-/multi-converter flexible alternating current transmission system devices as well as high voltage direct current systems operating at the transmission level. The magnetic interface of the converter is originally designed with given all parameters for 100 MVA operation. The so-called two-angle control method is adopted to control the voltage magnitude and the phase angle of the converter independently. PSCAD simulation results verify both four-quadrant converter operation and closed-loop control of the converter operated as static synchronous compensator (STATCOM).     

New zero voltage switching DC converter with flying capacitors

A new soft switching converter is presented for medium power applications. Two full-bridge converters are connected in series at high voltage side in order to limit the voltage stress of power switches at V_in/2. Therefore, power metal–oxide–semiconductor field-effect transistors (MOSFETs) with 600 V voltage rating can be adopted for 1200 V input voltage applications. In order to balance two input split capacitor voltages in every switching cycle, two flying capacitors are connected on the AC side of two full-bridge converters. Phase-shift pulse-width modulation (PS-PWM) is adopted to regulate the output voltage. Based on the resonant behaviour by the output capacitance of MOSFETs and the resonant inductance, active MOSFETs can be turned on under zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. Two full-bridge converters are used in the proposed circuit to share load current and reduce the current stress of passive and active components. The circuit analysis and design example of the prototype circuit are provided in detail and the performance of the proposed converter is verified by the experiments.     

A miniature high-efficiency fully digital adaptive voltage scaling buck converter

A miniature high-efficiency fully digital adaptive voltage scaling (AVS) buck converter is proposed in this paper. The pulse skip modulation with flexible duty cycle (FD-PSM) is used in the AVS controller, which simplifies the circuit architecture (<170 gates) and greatly saves the die area and the power consumption. The converter is implemented in a 0.13-μm one-poly-eight-metal (1P8 M) complementary metal oxide semiconductor process and the active on-chip area of the controller is only 0.003 mm², which is much smaller. The measurement results show that when the operating frequency of the digital load scales dynamically from 25.6 MHz to 112.6 MHz, the supply voltage of which can be scaled adaptively from 0.84 V to 1.95 V. The controller dissipates only 17.2 μW, while the supply voltage of the load is 1 V and the operating frequency is 40 MHz.     

射极激励式准谐振反激变换器

针对ＲＣＣ型变换器存在的开关损耗问题,提出了对电路参数和磁路参数进行统一设计,以实现零电压开关的方法－射极激励技术,使双极性晶体管无二次击穿机理,功率处理能力仅取决于结温的限制。     

基于耦合电感高增益Buck-Boost变换器小信号建模

基于耦合电感的高增益变换器在新能源发电和直流微电网中均有良好的应用前景。论文在分析基于耦合电感的高增益升降压(Buck-Boost)变换器工作原理的基础上,采用开关流图法建立变换器的模型,详细推导了变换器的稳态模型和交流小信号模型;电力仿真(PSIM)软件对变换器小信号模型的仿真结果证明论文模型的正确性。论文结果对高增益DC/DC变换器控制回路的设计具有较高的参考价值。     

A flying-capacitor ZVS PWM 1.5 kW DC-to-DC converter with half ofthe input voltage across the switches

This paper introduces an isolated flying-capacitor DC-to-DC converter which features half of the input voltage across the switches, zero-voltage-switching, operation at constant frequency, regulation by pulse-width-modulation, and low RMS current stress upon power switches. The complete operating principle, theoretical analysis, relevant equations and design example are provided in this paper. The experimental results of a 1.5 kW converter with 60 V, 25 A output. 600 V input, operating at 50 kHz switching frequency are also presented and discussed in the paper. The proposed converter is an alternative to the full-bridge ZVS-PWM DC-to-DC converter in high-input voltage applications     

一种移相全桥ZVZCS变换器的研究与应用

基于对ZVZCS-PWM全桥变换器工作原理的分析,利用Pspice仿真软件对该变换器主电路进行了仿真,详细给出了仿真电路中的参数,对各仿真波形进行了分析。并在此基础上设计出一台50v／15A全桥软开关电源实验样机,在实验样机上测量出其实际运行时的波形及变换器效率。实验结果证明该变换器超前桥臂很好地实现了零电压开关,并在任意负载和输入电压范围内实现了滞后桥臂的零电流开关。