Oscillation effect of auxiliary winding in primary side regulated flyback converter

In the operation of a primary‐side‐regulated (PSR) flyback converter, oscillation of the auxiliary winding would degrade the system reliability, as this winding plays an important role. In previous works, the oscillation of the auxiliary winding was thought to be related to the oscillation of the primary winding when the switch is turned off. However, a comprehensive explanation has not been given for this phenomenon. Meanwhile, the oscillation of the auxiliary winding depends not only on the oscillation of the primary winding but also on the conducting size and the layer distribution. Based on a multi‐winding model obtained from the physical dimensions, this paper derives a mathematical expression to calculate the relation, in the time domain, between the ringing of the auxiliary winding and primary winding. The analytical results would allow the magnetic windings to be analyzed and optimized because the oscillation of the auxiliary winding is expressed as a function of the winding geometry and position. Besides, the skin and proximity effects as well as the nonlinear core properties are considered in the multi‐winding model. An application example is also included. Simulation and experimental results of a single‐stage, 16‐W PSR flyback converter are given to validate the proposed analysis. © 2016 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis and design of a dual‐mode control flyback converter

This letter presents a dual‐mode control scheme to improve the efficiency of a flyback converter in a wide load range. The proposed flyback converter features a novel dual‐mode operation. The valley‐switching technique is adopted to reduce the switching loss at light load. On the other hand, the fixed off‐time (FOT) controls with continuous conduction mode operations decrease the conduction losses at heavy load. The principles and design procedures of the proposed dual‐mode controller are discussed and analyzed. Finally, a 140‐W dual‐mode flyback converter with an output voltage of 19 V is implemented. Experimental results agree with the theoretical analysis. Copyright © 2012 John Wiley & Sons, Ltd.     

Modelling cross‐regulation in a single switched capacitor DC‐DC converter

The letter proposes to model cross‐regulation in a dual‐output switched capacitor converter (SCC) by three equivalent resistances connected in delta circuit. It is shown that as opposed to linear equivalent (output) resistance of single‐output SCCs, these resistances are voltage‐controlled. The obtained analytical expressions have been verified by simulations and give correct results even if the output voltages change in wide range. The proposed analysis paves the way for modelling cross‐regulation in complex SCCs with multiple topologies and can be useful in studies of crosstalk through parasitic capacitances on chip.     

Two‐switch flyback PWM DC‐DC converter in continuous‐conduction mode

The two‐switch flyback DC‐DC converter is an extended version of the conventional single‐switch flyback converter. An additional switch and two clamping diodes serve as a simple, but an effective way to limit the switch overvoltages, which occur in the conventional single‐switch flyback converter due to the ringing of the resonant circuit formed by the transformer leakage inductance and the transistor output capacitance. The clamping diodes in the two‐switch flyback topology clamp the maximum voltage across each switch equal to the DC input voltage. This paper presents a detailed steady‐state analysis and design procedure of the diode‐clamped two‐switch flyback converter operated in continuous‐conduction mode (CCM). The power loss in each component of the two‐switch flyback converter is compared with those of the single‐switch flyback converters with and without RCD clamp, and is presented in a tabular form. The two‐switch flyback converter was bread‐boarded to validate the theoretical analysis. Experimental results from a 10 V/30 W, 100 kHz laboratory prototype verified that the maximum switch voltage is limited to the DC input voltage. Copyright © 2010 John Wiley & Sons, Ltd.     

Dynamic model development and control for multiple‐output flyback converters in DCM and CCM

Multiple‐output flyback converters are widely used in switching power supplies due to their low component count and cost‐effective structure. The main problem of this structure is how to balance output voltages in different load conditions. This paper proposes a new approach for single‐input multiple‐output flyback converters operating in DCM and CCM by a small‐signal averaged model. The averaged model is derived by presenting the piecewise‐linear waveform for the inductor currents inside the converter. In DCM, the magnetizing current and currents through the output windings reach zero when the switch is turned off. In CCM, the magnetizing current of the converter is continuous over a switching interval and this possibility exists that only some of the output diodes completely conduct when the switch is off. The proposed model of the converter can be used in a wide range of operations within identical and non‐identical loading conditions. Using a laboratory prototype, several case studies and input‐to‐output transfer functions are considered to verify the proposed model. The controller design is performed for the both CCM and DCM, and then dynamic characteristics of the overall system are evaluated.     

Design of a two‐output forward converter with an output voltage objective function

A new method is proposed in this paper to distribute the steady‐state output voltage errors in a two‐output forward converter. The cross regulation between the two output voltages are described in terms of the circuit parameters. An objective function is formed for each of the two outputs to track its reference within the specified error. The legitimate duty cycle range is located through the transfer characteristics between the duty cycle and the load currents. The weighting feedback gains of the two output voltages can be determined by the presented control scheme which optimizes the objective function. The proposed method is suitable for a two‐output system without a dominant load. Experiments on a prototype are conducted to show that there exist a duty cycle range and a set of weighted feedback gains minimizing the defined objective function. Copyright © 2010 John Wiley & Sons, Ltd.     

通过设计变压器改善反激变换器的交叉调整率

鉴于变压器性能对多路输出反激变换器的交叉调整率有重要影响,为变换器的关键器件之一,提出了基于有限元数值仿真的任意多路输出变压器的建模方法.基于此模型,结合电路仿真软件研究了变压器分布参数及线圈结构对反激变换器交叉调整率的影响.在此基础上,给出变压器的设计指导原则.实验证明,提出的任意多路输出变压器建模方法不仅使用方便,而且所建模型有足够高的精度;所设计的指导原则可有效提高多路输出变换器的交叉调整率.     

LLC resonant DC–DC converter with series‐connected primary windings of transformer

This paper proposes a zero‐voltage switching (ZVS) LLC resonant step up DC–DC converter with series‐connected primary windings of the transformer. The series resonant inverter in the proposed topology has two power switches (MOSFETs), two resonant capacitors, two resonant inductors, and only one transformer with center‐tapped primary windings. The power switches are connected in the form of a half‐bridge network. Resonant capacitors and inductors along with the primary windings of the transformer form two series resonant circuits. The series resonant circuits are fed alternately by operating the power switches with an interleaved half switching cycle. The secondary winding of transformer is connected to a bridge rectifier circuit to rectify the output voltage. The converter operates within a narrow frequency range below the resonance frequency to achieve ZVS, and its output power is regulated by pulse frequency modulation. The converter has lower conduction and switching losses and therefore higher efficiency. The experimental results of a 500‐W prototype of proposed converter are presented. The results confirm the good operation and performance of the converter. © 2014 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Performance analysis and calculation of critical inductance and output voltage ripple of a simple non‐isolated multi‐input bidirectional DC‐DC converter

In this paper, a simple non‐isolated multiple input (MI) bidirectional DC‐DC topology is proposed which can operate in buck, boost, or buck‐boost modes. The proposed topology utilizes a battery pack to realize the bidirectional power flow operation especially when the input sources are non‐storable ones. The excess energy of input sources can be stored in the battery and be injected to the load, when required. Simultaneous or independent power transfer of input sources is also provided. For better evaluation, the proposed topology has been compared with several recently presented novel topologies, from view point of number of inductors, capacitors, switches, and diodes. Comparison results show that the proposed topology utilizes less number of components (switches, inductors, capacitors, and current sensors) which can reduce the size, cost, and complexity of converter. Different operational modes of the proposed topology (unidirectional buck, boost, buck‐boost modes, and bidirectional mode) have been presented. Also, boost mode of the proposed topology has been investigated in detail, from design point of view, and generalized relationships have been proposed for calculation of critical inductance (CI) and output voltage ripple (OVR) of proposed n‐input boost topology. To validate proposed theoretical concepts, the proposed topology has been modeled and simulated in PSCAD/EMTDC software, and the 3‐input boost version has been experimentally implemented. Simulation and experimental results confirm appropriate performance of the proposed topology.     

Adaptive B‐spline neural network‐based vector control for a grid side converter in wind turbine‐DFIG systems

This paper presents a novel control system design for the grid‐side converter of doubly fed induction generator wind power generation systems. The control method proposed in this work is a vector control based on adaptive B‐spline neural network by using a simple fixed‐gain stabilizing control topology. The adaptive control is designed both for inner current loops and an outer DC‐link voltage loop of the grid side converter control system. To guarantee the control stability, the weights updating rule for the B‐spline neural network is synthesized by utilizing Lyapunov's direct method. To verify the effectiveness of the proposed control system, extensive simulations are performed using MATLAB/Simulink. Based on the simulation results, it is concluded that the proposed controller has improved performance compared to an optimum proportional integral control system. It is also relatively robust against external disturbances and variations of the control parameters. © 2015 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

水电机组一次调频控制系统分析与功能完善

文中深入分析了水电机组一次调频控制系统动态与静态特性,指出一次调频控制系统在功率闭环控制模式下存在的问题,提出了功率开环控制模式一次调频控制系统方案.在开度控制模式基础上,引入"开度一功率"非线性反馈环节,既能保持开度控制模式响应电网频率变化的快速性,又能达到功率闭环控制模式机组目标功率准确性.     

Analysis and design of a two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers

A new two‐transformer active‐clamping forward converter with parallel‐connected current doubler rectifiers (CDRs) is proposed in this paper. The presented DC–DC converter is mainly composed of two active‐clamping forward converters with secondary CDRs. Only two switches are required and each one is the auxiliary switch for the other. The circuit complexity and cost are thus reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve zero‐voltage‐switching (ZVS) during the dead times. Two CDRs at the secondary side are connected in parallel to reduce the current stresses of the secondary windings and the ripple current at the output side. Accordingly, the smaller output chokes and capacitors decrease the converter volume and increase the power density. Detailed analysis and design of the presented two‐transformer active‐clamping forward converter are described. Experimental results are recorded for a prototype converter with a DC input voltage of 130??180V, an output voltage of 5 V and an output current of 40 A, operating at a switching frequency of 100 kHz. Copyright © 2010 John Wiley & Sons, Ltd.     

Harmonic spectrum analysis of the output voltage and grid‐side filter design for three‐level voltage‐source converters

Because of the complex arithmetic computation of the traditional three‐level space vector modulation (SVM), its hardware implementation is difficult to achieve. Moreover, the normal approach of acquiring the output voltage harmonic is sensitive to the simulation step, measurement accuracy, system noise, etc. This paper proposes a new method for analyzing the voltage harmonic spectrum of the three‐level converter. Furthermore, the minimum value of the inductance of the grid‐side filters is designed on this basis. First, the formulas of the duty cycle and the modulation waveform of the three‐level SVM algorithm are easily derived using some simple linear calculations under the 120° coordinate. Then, considering the characteristics of the digital circuits, the harmonic components of the output voltage are calculated using Fourier analysis. Third, a precise analytical design of the minimum inductance value of grid‐connected converters with LCL and L input filters is presented. Finally, the validity of this approach is verified by using experimental results. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Analysis and implementation of a high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter

A high‐efficiency zero‐voltage‐zero‐current‐switching DC–DC converter with ripple‐free input current is presented. In the presented converter, the ripple‐free boost cell provides ripple‐free input current and zero‐voltage switching of power switches. The resonant flyback cell provides zero‐voltage switching of power switches and zero‐current switching of the output diode. Also, it has a simple output stage. The proposed converter achieves high efficiency because of the reduction of the switching losses of the power switches and the output diode. Detailed analysis and design of the proposed converter are carried out. A prototype of the proposed converter is developed and its experimental results are presented for validation. Copyright © 2011 John Wiley & Sons, Ltd.     

Analysis and experimental verification of the linear correlation of the operation condition among the bifurcation points of current‐mode‐controlled buck–boost converter

The operation parameter of the buck–boost converter is examined for its boundary of the first flip bifurcation. It is found that the parameters exhibit a linear relation for the same parameter at another bifurcation point. The bifurcation parameters also have a linear correlation between them. Theoretical analysis is presented to explain how this can occur. Simulation and experimental results at 20 kHz are used to present these novel results. Copyright © 2005 John Wiley & Sons, Ltd.     

Analysis and design of a ZVS converter for high voltage input–low voltage output application

This paper proposes a full‐bridge (d = 50%) cascaded buck topology which is a very suitable circuit for high voltage input–low voltage output applications with high output current. Benefiting from working under a large duty cycle, the proposed converter can easily achieve zero voltage switching turn‐on and turn‐off of active switches in a full bridge. Small‐signal model of this topology is analyzed through its corresponding peak current mode control. Its small‐signal transfer function is given, and the control loop design is discussed. Advantages of this topology and operation principles are analyzed. Design guidelines, drawn from this analysis, are applied on a low‐voltage (3.3 V) output voltage prototype to validate the proposed concept. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Influence of period‐doubling bifurcations in the appearance of border collisions for a ZAD‐strategy‐controlled buck converter

The first period‐doubling bifurcation of a dc–dc buck converter controlled by a zero‐average dynamic strategy is studied in detail. Owing to the saturation of the duty cycle, this bifurcation is followed by a border‐collision bifurcation, which is the main mechanism to introduce instability and chaos in the circuit. The multiparameter analysis presented here leads to a complete knowledge of the relatioship between these two bifurcations. The results are obtained by using a frequency‐domain approach for the study of period‐two oscillations in maps. Copyright © 2010 John Wiley & Sons, Ltd.     

Impact of stray inductances of the power loop on false trigger‐on in the zero‐voltage‐switching full‐bridge converter

Here, we propose an exhaustive theoretical investigation and experimental verification of the false trigger‐on phenomenon, which would lead to the interaction between the upper and lower devices during the switching transient, in the zero‐voltage‐switching (ZVS) full‐bridge converter. An equivalent model of the converter, which takes not only the parasitic capacitors of the metal–oxide–semiconductor field‐effect transistors into account but also the stray inductances of the main circuit, is presented. Based on the model, a comprehensive study of the false trigger‐on phenomenon is carried out. According to the analysis results, the stray inductances of the metal–oxide–semiconductor field‐effect transistors have negligible influence on the false trigger‐on phenomena since the soft‐switching is realized. The false trigger‐on phenomenon is induced by the stray inductances of the main circuit. Moreover, the arrangement of the switching sequence would cause significant discriminations in the false trigger‐on phenomena because of the specific working mode of the ZVS full‐bridge converter. According to the investigation results, optimization methods are presented to suppress the induced voltage. At last, the theoretical investigations are verified by tests of a ZVS full‐bridge converter. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis and design of a half‐bridge LLC series resonant converter employing two transformers

This paper presents a two‐transformer LLC series resonant converter (SRC), which is derived from incorporating two identical converters. The proposed converter allows a low‐profile power supply design for liquid crystal display (LCD) TVs and servers. The presented converter can equally share the total load current between two transformers and the output rectifier modules. Therefore, the heat problem can be effectively relieved. The steady‐state analysis and design of this new two‐transformer LLC SRC are described. The experimental results are recorded for a prototype converter with an output voltage of 12thinspaceV, an output power of 300 W, and a resonant frequency of 74 kHz. Copyright © 2011 John Wiley & Sons, Ltd.     

SPWM逆变器死区效应的研究

在SPWM逆变器中,为防止同一桥臂上的上下两个器件发生直通现象,必须注入若干微秒的死区时间。死区会导致逆变器的波形畸变,即死区效应,如输出基波电压降低、谐波成分增大等,这种效应随着调制频率的增大而增加,其结果是影响了高速开关器件的有效利用,降低了SPWM调速系统的动、静态性能,增大了低次谐波的抑制难度。文章对不同使用条件下死区时间引起的输出电压基波、低次谐波的变化规律进行了系统分析,建立了定量计算的数学模型,给出了仿真曲线,并以实验结果作了验证。所得结论对于SPWM逆变器的设计具有一定的参考作用。