A novel forward AC/DC converter with input current shaping and fast output voltage regulation via reset winding

This work presents a novel simple forward AC/DC converter with harmonic current correction and fast output voltage regulation. In the proposed AC/DC converter, a transformer incorporating reset winding provides two main advantages. First, the bulk inductor used in the conventional boost-based power-factor-correction cell is omitted in the proposed converter, allowing significant volume and weight of magnetic material to be saved. Second, the voltage across the bulk capacitor can be held under 450 V by adjusting the transformer winding ratio, despite the converter operating in a wide range of input voltages (90/spl sim/265 V/AC). This new converter complies with IEC 61000-3-2 under a load range of 200 W and has fast output voltage regulation.     

A leakage-inductance-based ZVS two-inductor boost converter with integrated magnetics

A two-inductor boost converter topology has conduction loss and transformer utilization advantages in converting low-voltage higher current inputs to high output voltages. In this letter, a new zero-voltage switching (ZVS) two-inductor boost converter with integrated magnetics is proposed. In the new topology, the two current source inductors, a resonant inductor and a two-winding transformer, are integrated into one single magnetic core with three windings. Two windings simultaneously perform the functions of the current source inductors and the transformer primary. The transformer leakage inductance forms the resonant inductance. This leads to a much more compact converter design with a significant reduction in the number of core and winding components. A theoretical analysis establishes the operating point of the ZVS converter. Both of the theoretical and experimental waveforms, including flux waveforms for the legs of the integrated core structure, are presented at the end of the letter.     

A single-stage power-factor-corrected AC/DC converter

This paper presents a single-stage isolated converter topology designed to achieve a regulated DC output voltage having no low-frequency components and a high-input power factor. The topology is derived from the basic two-switch forward converter, but incorporates an additional transformer winding, inductor and a few diodes. The proposed circuit inherently forces the input current to be discontinuous and AC modulated to achieve high-input power factor. The converter output is operated in discontinuous mode to minimize the bulk capacitor voltage variations when the output load is varied. Analysis of the converter is presented, and performance characteristics are given. Design guidelines to select critical components of the circuit are presented. Experimental results on a 150 W 50 kHz universal input (90-265 V) 54.75 V output AC/DC converter are given which confirm the predicted performance of the proposed topology     

一种新型单级功率因数校正AC/DC变换器的研究

文章研究了一种新型单级单开关PFC反激变换器。该变换器负载变轻时其储能电容电压不会飘升,应用于宽范围交流输入电压,储能电容电压低于450V。变换器用其变压器中的一个附加绕组实现了升压功能。由于省去了大电感,减小了变换器的体积和重量,在中小功率应用场合下,变换器符合IEC61000-3-2class D谐波标准,并且具有输出电压快速调节能力。     

Design of 48 V Voltage regulator modules with a novel integrated magnetics

The push-pull forward topology with the current-doubler and synchronous rectifier is a suitable approach for high-input voltage regulator modules (VRMs) used to supply high-performance microprocessors. In order to improve efficiency and reduce size, this paper proposes an improved push-pull forward converter with a novel integrated magnetics. All the magnetic components including input filter inductor, step-down transformer and output filter inductors are integrated into a single EI or EE core. This topology is essentially the modified push-pull converter with the built-in input filter and the coupled-inductor current doubler rectifier. The proposed integrated magnetic structure features a simple core structure, a small leakage inductance and low winding and core losses. A design is given for a 48-V VRM with a 1.2-V and 70-A output, and its experimental results show that the proposed approach can offer a great improvement in efficiency.     

Flexible and low cost design for a flyback AC/DC converter with harmonic current correction

This study presents a new simple flyback ac/dc converter with harmonic current correction and fast output voltage regulation. In the proposed ac/dc converter, an extra winding wound in the transformer provides two key advantages. The size of the bulk inductor used in the conventional boost-based power factor correction cell can be significantly reduced in the proposed converter. The voltage across bulk capacitor can be held under 450V by tuning the transformer winding ratio even though the converter operates in a wide range of input voltages (90 V/spl sim/265V/ac). This new converter complies with IEC 61000-3-2 under the load range of 200 W, and can achieve fast output voltage regulation.     

PCB integrated inductors for low power DC/DC converter

This paper discusses the use of printed circuit board (PCB) integrated inductors for low power DC/DC buck converters. Coreless, magnetic plates and closed core structures are compared in terms of achievable inductance, power handling and efficiency in a footprint of 10 /spl times/ 10 mm/sup 2/. The magnetic layers consist of electroplated NiFe, so that the process is fully compatible with standard PCB process. Analytic and finite element method (FEM) methods are applied to predict inductor performance for typical current waveforms encountered in a buck converter. Conventional magnetic design procedures are applied to define optimum winding and core structures for typical inductor specifications. A 4.7 /spl mu/H PCB integrated inductor with dc current handling of up to 500 mA is presented. This inductor is employed in a 1.5 W buck converter using a commercial control integrated circuit (IC). The footprint of the entire converter measures 10 /spl times/ 10 mm/sup 2/ and is built on top of the integrated inductor to demonstrate the concept of integrated passives in power electronic circuits to achieve ultra flat and compact converter solutions.     

飞机直流母线变换器的输入电磁干扰滤波器设计

针对飞机直流270 V至直流28 V电源变换器的应用需求,分析了电源变换器输入端的传导及辐射电磁干扰源.通过对电源变换器的电磁干扰（electromagnetic interference,EMI）频谱进行分析,确定了滤波器的参数.为了抑制滤波器振荡,提出在差模电感两端并联电阻电感网络的方法,替代使用液态铝电容的传统方法,提升滤波器的可靠性.根据差模电感中电流直流分量远高于交流分量的特点,提出采用扁铜漆包线来实现绕组的方法,使差模电感的体积降低.根据锰锌铁氧体低频磁导率高,镍锌铁氧体高频磁导率稳定的特点,提出双磁芯共模电感的设计方法,实现共模电感宽频率和小体积.实测结果证明输入电磁干扰滤波器可使电源变换器符合GJB 151中CE102要求.     

采用倍流整流移相全桥的ZVZCS直流变换器研究

在传统的移相全桥ZVZCS直流变换器中,输出侧多采用全波整流式结构,在大电流输出条件下这种结构将增加输出滤波电感和变压器的体积以及整流管上的电压应力,不利于在低压大电流输出场合的应用。针对这种情况,文章在输出侧采用一种适宜应用在低电压大电流输出场合的倍流整流式结构,使变压器和输出滤波电感的设计得到简化,并且输出整流二极管实现了零电流自然关断,降低了功率器件的应力与开关损耗,适合于大功率场合;文中还简单讨论了软开关的实现范围和参数的设计等问题。最后,在以上分析的基础上,设计了一台输出电压为27V,输出功率为3kW的电源,利用Matlab/Simulink进行了仿真,并给出了相应的仿真结果。     

Interleaved ZVS Converter With Ripple-Current Cancellation

In this paper, an interleaved soft-switching converter with ripple-current cancellation is presented to achieve zero- voltage-switching (ZVS) turn-on and load current sharing. In order to achieve ZVS turn-on, an active snubber is connected in parallel with the primary winding of the 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 at the transition interval is used to realize ZVS turn-on of all switches. In order to achieve three-level pulsewidth-modulation (PWM) scheme, an addition fast-recovery diode is used in the converter. Three-level PWM scheme can reduce the ac ripple current on the output inductor such that the output inductor can be reduced. The current-doubler rectifier is adopted in the secondary side of the transformer to reduce the transformer secondary-winding current and output voltage ripple by canceling the current ripple of two output inductors. The output voltage is controlled at the desired value using the interleaved PWM scheme. These features make the proposed converter suitable for the dc-dc converter with high output current. The operation principles, steady state analysis, and design equations of the proposed converter are provided in detail. Finally, experiments based on a 600-W (12 V/50 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.     

Introduction to modeling of transformers and coupled inductors

A tutorial paper is presented on modeling and design of transformers and coupled inductors. Beginning with a brief review of electromagnetic laws and magnetic circuit models, the magnetic and electric models of transformers and coupled inductors are developed, including both magnetizing and leakage effects. It is shown that while the voltage waveforms on the windings are primarily related by the turns ratio for both devices, the winding currents of transformers and coupled inductors are determined by very different mechanisms. An integrated structure with both transformer and coupled inductor on the same core is also discussed, as well as the special case of the coupled inductor used on a multiple-output transformer-isolated converter     

A Fully Integrated Thin‐Film Inductor and Its Application to a DC‐DC Converter

This paper presents a simple process to integrate thin‐film inductors with a bottom NiFe magnetic core. NiFe thin films with a thickness of 2 to 3 μm were deposited by sputtering. A polyimide buffer layer and shadow mask were used to relax the stress of the NiFe films. The fabricated double spiral thin‐film inductor showed an inductance of 0.49 μH and a Q factor of 4.8 at 8 MHz. The DC‐DC converter with the monolithically integrated thin‐film inductor showed comparable performances to those with sandwiched magnetic layers. We simplified the integration process by eliminating the planarization process for the top magnetic core. The efficiency of the DC‐DC converter with the monolithic thin‐film inductor was 72% when the input voltage and output voltage were 3.5 V and 6 V, respectively, at an operating frequency of 8 MHz.     

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     

Design of LCL-T Resonant Converter Including the Effect of Transformer Winding Capacitance

The transformer winding capacitance, which is significant in high-voltage power supplies, is not gainfully utilized in an LCL-T resonant converter (RC). A simplified analysis presented in this paper predicts the severe degradation of output current regulation of an LCL-T RC due to transformer winding capacitance. The presence of winding capacitance, in fact, changes the third-order LCL-T resonant tank into fourth-order LC-LC topology. Using an AC analysis, it is shown that, under the derived design conditions, LC-LC RC also exhibits constant output current and in-phase source voltage and current, simultaneously at all loading conditions. Thus, the transformer leakage inductance and winding capacitance are gainfully utilized as a part of a resonant network, resulting in improved output characteristics. Closed-form expressions for the converter gain and component stresses are derived. The condition for converter design optimized for the minimum size of the resonant network is obtained. Experimental results on a prototype 100-mA 2-kV DC power supply confirm the observations of analysis.     

Single-Stage Push–Pull Boost Converter With Integrated Magnetics and Input Current Shaping Technique

This paper presents a novel single-stage push–pull boost converter with improved integrated magnetics and a better low-ripple input current. Most of the reported single-stage power factor corrected (PFC) rectifiers cascade a boost-type converter with a dc–dc converter. It is found that the push–pull converter, when the duty cycles are greater than 50%, can simplify the front end of the boost-type converter to a novel single-stage converter. Coupled inductor techniques provide a method to reduce the converter size and weight and to achieve a ripple-free current. All the magnetic components including the input filter inductor and the step-down transformer are integrated into a single EI core. The proposed integrated magnetic structure has a simple core structure, a small leakage inductance, and low core losses. The prototype is built to demonstrate the theoretical prediction.     

基于DPA—Switch的反激式开关电源设计

DPA-Switch是高集成度DC／DC转换芯片,集PWM控制器和MOSFET于一体,其电路简单,性能优异。文中利用DPA-Switch设计了一个单端反激式多路输出开关电源,简要介绍了变压器的绕制。实验结果表明该电源运行可靠,输出稳定。     

High-Efficiency Boost Half-Bridge Converter With Fast Boost Current Transferring ZVS Operation

A new boost half bridge (BHB) converter is presented. It is composed of additional switch, diode and coupled winding to boost inductor of BHB converter. Using the transferring of boost inductor current to coupled winding in a short period, the cancellation of zero voltage switching (ZVS) current, which always occurs in convention one, is prevented. Therefore, the ZVS operation is easily achieved by leakage inductor current of transformer. Furthermore, since negatively build-up leakage inductor current of boost winding helps the ZVS operation throughout full load range, the excellent ZVS operation and high efficiency is achieved.      

Coupled Inductor Incorporated Boost Half-Bridge Converter With Wide ZVS Operation Range

A new boost half-bridge (BHB) converter is presented. It is composed of an additional diode and a coupled winding to the boost inductor of the BHB converter. Using the transferring of a boost inductor current to the coupled winding, the cancellation of zero-voltage-switching (ZVS) current, which always occurs in a conventional one, is prevented. Therefore, the ZVS operation is easily achieved by the leakage inductor current of the transformer. Furthermore, since the negatively built-up leakage inductor current of the boost winding helps the ZVS operation throughout a wide load range, the ZVS operation is always guaranteed.      

薄膜解耦集成磁件的结构设计与研究

文中分析了磁件解耦集成的基本原理,得出了磁件实现解耦集成所需的基本条件;根据抵消绕组间耦合作用的方法设计了一个解耦的集成磁件,将一个小功率变压器和一个电感集成在一起;采用薄膜化技术设计制作该集成磁件的薄膜磁芯;为了消除采用传统磁件结构时磁件两端的漏磁,设计了特殊的磁芯结构和与其相配套的绕组结构;对该磁件进行了仿真研究,验证了设计的有效性和可行性。     

变压器双向磁化类变换器工作原理的讲解方法

在电力电子技术课程中,推挽式、半桥式和全桥式隔离型变换器电路属一类变压器磁芯双向磁化的基本电路,在实际中得到广泛的应用。如何给学生解释清楚铁心双向对称磁化的原理是一个教学难点。本文以推挽电路为例分析了铁心双向对称磁化工作机理。从带磁复位绕组的单端正激变换器的变压器铁心磁化工作原理出发,将推挽变换器看成是两个带磁复位绕组的单端正激变换器的组合。并从空载时占空比小于四分之一情况出发,循序渐进地全面细致地分析了各种负载情况下的工作原理,这种讲解思路严谨且易于被学生理解和接受。