用开关电容网络改善DC-DC变换器性能的研究

将串并电容组合结构,极性反转开关电容网络和推挽开关电容网络和ｂｕｃｋ,ｂｏｏｓｔ,Ｃｕｋ及ｂｕｃｋ－ｂｏｏｓｔ等传统ＤＣ－ＤＣ变换器相结合,构成一系列新的变换器拓扑结构。理论分析和实验结果秀助于提高具有悬殊电压变化比的ＤＣ－ＤＣ变换器的工作频率和动态响应,还能拓宽变换器的电压变换范围。     

Modeling PWM DC/DC converters out of basic converter units

An alternative approach to modeling pulsewidth-modulated (PWM) DC/DC converters out of basic converter units (BCUs) is presented in this paper. Typical PWM DC/DC converters include the well-known buck, boost, buck-boost, Cuk, Zeta, and Sepic. With proper reconfiguration, these converters can be represented in terms of either buck or boost converter and linear devices, thus, the buck and boost converters are named BCUs. The PWM converters are, consequently, categorized into buck and boost families. With this categorization, the small-signal models of these converters are readily derived in terms of h parameter (for buck family) and g parameter (for boost family). Using the proposed approach, not only can one find a general configuration for converters in a family, but one can yield the same small-signal models as those derived from the direct state-space averaging method. Additionally, modeling of quasi-resonant converters and multiresonant converters can be simplified when adopting the proposed approach     

Switched-Capacitor/Switched-Inductor Structures for Getting Transformerless Hybrid DC–DC PWM Converters

A few simple switching structures, formed by either two capacitors and two-three diodes (C-switching), or two inductors and two-three diodes (L-switching) are proposed. These structures can be of two types: ldquostep-downrdquo and ldquostep-up.rdquo These blocks are inserted in classical converters: buck, boost, buck-boost, Cuk, Zeta, Sepic. The ldquostep-downrdquo C- or L-switching structures can be combined with the buck, buck-boost, Cuk, Zeta, Sepic converters in order to get a step-down function. When the active switch of the converter is on, the inductors in the L-switching blocks are charged in series or the capacitors in the C-switching blocks are discharged in parallel. When the active switch is off, the inductors in the L-switching blocks are discharged in parallel or the capacitors in the C-switching blocks are charged in series. The ldquostep-uprdquo C- or L-switching structures are combined with the boost, buck-boost, Cuk, Zeta, Sepic converters, to get a step-up function. The steady-state analysis of the new hybrid converters allows for determing their DC line-to-output voltage ratio. The gain formula shows that the hybrid converters are able to reduce/increase the line voltage more times than the original, classical converters. The proposed hybrid converters contain the same number of elements as the quadratic converters. Their performances (DC gain, voltage and current stresses on the active switch and diodes, currents through the inductors) are compared to those of the available quadratic converters. The superiority of the new, hybrid converters is mainly based on less energy in the magnetic field, leading to saving in the size and cost of the inductors, and less current stresses in the switching elements, leading to smaller conduction losses. Experimental results confirm the theoretical analysis.     

Soft switching active snubbers for DC/DC converters

A soft-switching active snubber is proposed to reduce the turn-off losses of the insulated gate bipolar transistor (IGBT) in a buck power converter. The soft-switching snubber provides zero-voltage switching for the IGBT, thereby reducing its high turn-off losses due to the current tailing. The proposed snubber uses an auxiliary switch to discharge the snubber capacitor. This auxiliary switch also operates at zero-voltage and zero-current switching. The size of the auxiliary switch compared to the main switch makes this snubber a good alternative to the conventional snubber or even to passive low-loss snubbers. The use of the soft-switching active snubber permits the IGBT to operate at high frequencies with an improved RBSOA. In the experimental results reported for a 1 kW, 40 kHz prototype, combined switching/snubbing losses are reduced by 36% through the use of the active snubber compared to a conventional RCD snubber. The use of an active snubber allows recovery of part of the energy stored in the snubber capacitor during turn-off. The generic snubber cell for the buck power converter is generalized to support the common nonisolated DC/DC power converters (buck, boost, buck-boost, Cuk, sepic, zeta) as well as isolated DC/DC power converters (forward, flyback, Cuk, and sepic)     

A novel PWM control for a bi-directional full-bridge DC–DC converter with smooth conversion mode transitions

A novel CMOS integrated pulse-width modulation (PWM) control circuit allowing smooth transitions between conversion modes in full-bridge based bi-directional DC–DC converters operating at high switching frequencies is presented. The novel PWM control circuit is able to drive full-bridge based DC–DC converters performing step-down (i.e. buck) and step-up (i.e. boost) voltage conversion in both directions, thus allowing charging and discharging of the batteries in mobile systems. It provides smooth transitions between buck, buck-boost and boost modes. Additionally, the novel PWM control loop circuit uses a symmetrical triangular carrier, which overcomes the necessity of using an output phasing circuit previously required in PWM controllers based on sawtooth oscillators. The novel PWM control also enables to build bi-directional DC–DC converters operating at high switching frequencies (i.e. up to 10?MHz and above). Finally, the proposed PWM control circuit also allows the use of an average lossless inductor-current sensor for sensing the average load current even at very high switching frequencies. In this article, the proposed PWM control circuit is modelled and the integrated CMOS schematic is given. The corresponding theory is analysed and presented in detail. The circuit simulations realised in the Cadence Spectre software with a commercially available 0.18?µm mixed-signal CMOS technology from UMC are shown. The PWM control circuit was implemented in a monolithic integrated bi-directional CMOS DC–DC converter ASIC prototype. The fabricated prototype was tested experimentally and has shown performances in accordance with the theory.     

DC/DC变换器自适应模糊逻辑控制器设计

文章为DC/DC变换器设计了一种自适应模糊逻辑控制器（AFLC）。所提出的AFLC不需要专家系统提供决策参数和控制规则,而是使用模型数据文件来产生参数和规则,该模型数据文件包含输入输出对的整体概况。所提出的控制器使用8位微控制器来实现降压、升压和降压-升压变换器。     

一种新型交错并联同相降压升压DC/DC转换器

为了有效降低电流纹波和提高转换器效率,提出一种新型交错并联同相降压升压DC/DC转换器。提出的结构通过采用输入/输出（I/O）磁耦合交错并联和阻尼网络技术,降低了开关的电压应力、内部电压振荡和I/O电流纹波,并提升了转换器的效率。采用状态空间平均法,在连续导通模式下分析了提出转换器的稳态运行,从理论上证明了其优势。样机的功率设置为360W,输出电压为36 V,模拟结果以及实验结果显示,当输出电流为6A时,转换效率最高达到96%,最大输入电流纹波百分比仅为9.4%,相较于其他类似转换器,提出的转换器具有效率较高和I/O电流纹波较低的优势。     

New topology for DC/DC bidirectional converter for hybrid systems in renewable energy

This article presents a new isolated DC/DC bidirectional converter with soft switching, using a transformer with two voltage taps and two full bridges with insulated-gate bipolar transistors (IGBTs), one on each side of the transformer to be integrated in hybrid systems of renewable energy. A large voltage conversion ratio can be achieved using this converter, in buck and booster modes. Also medium and high DC power can be converted with a good efficiency. Analysis and switching techniques have been reported. To verify the principle of operation, a laboratory prototype of 10 kW has been performed. Experimental results are presented, operating in boost mode. The switching algorithm used has been modelled in MATLAB-Simulink to generate C code. This code has been implemented in a DSP F2812, which has been used to build the prototype.     

Spectral characteristics of randomly switched PWM DC/DC convertersoperating in discontinuous conduction mode

This paper addresses a comparative study of the spectral characteristics of four random-switching schemes that apply to the basic pulsewidth-modulation (PWM) DC/DC converters operating in discontinuous conduction mode (DCM). They include randomized pulse position modulation, randomized pulsewidth modulation, and randomized carrier frequency modulation with fixed duty cycle and with fixed duty time, respectively. Mathematical models that characterize the input current and output voltage of the three basic PWM converters operating in DCM are derived. In particular, the effectiveness of spreading the dominant switching harmonics in the input current that normally exist in the standard PWM scheme and the introduction of low-frequency harmonics in the output voltage with respect to the randomness level are investigated. The validity of the models and analyses are confirmed experimentally by using a DC/DC buck converter     

开关电容DC—DC变换器的效率

将开关电容网络应用到ＤＣ－ＤＣ变换器，并从能量的角度研究了其效率，得出一个对所有类型的开关电容变换器的适用的公式，提出了改善效率的新的拓扑结构，使升压与降压开关电容变换器有较高的效率，实验结果与计算机模拟均取得了与分析相同的结果。     

A systematic and unified approach to modeling PWM DC/DC convertersbased on the graft scheme

A systematic and unified approach to modeling pulsewidth modulated (PWM) DC/DC converters based on the graft scheme is presented in this paper. With the graft scheme, the typical PWM switch-mode converters, such as buck-boost, boost-buck (Cuk), Sepic, and dual Sepic, can be generated from the two basic converters, buck and boost. The small signal models of these converters can, therefore, be derived by properly combining those of the buck and boost. Using the proposed approach can help to yield highly related dynamic models of the converters in a family and, in addition, physical insights into the converters can be readily identified. This has made the proposed modeling method valuable and viable     

A passive lossless snubber cell for nonisolated PWM DC/DCconverters

A passive lossless snubber cell is proposed to improve the turn-on and turnoff transients of the MOSFETs in nonisolated pulsewidth modulated (PWM) DC/DC converters. Switching losses and EMI noise are reduced by restricting di/dt of the reverse-recovery current and dv/dt of the drain-source voltage. The MOSFET operates at zero-voltage-switching (ZVS) turnoff and near zero-current-switching (ZCS) turn-on. The freewheeling diode is also commutated under ZVS. As an example, operation principles, theoretical analysis, relevant equations, and experimental results of a boost converter equipped with the proposed snubber cell are presented in detail. Efficiency of 96% has also been measured in the experimental results reported for a 1 kW 100 kHz prototype in the laboratory, Six basic nonisolated PWM DC/DC converters (buck, boost, buck-boost, Cuk, Sepic, and Zeta) equipped with the proposed general snubber cells are also shown in this paper     

Total dose effects on power-MOSFET switching converters

Power MOSFETs have important applications in space systems, particularly in dc/dc power conversion. Transistors used in the space environment are subject to the effects of exposure to the natural radiation environment in space. Among the effects of ionizing radiation are shifts in threshold voltage and reduction of carrier mobility. In this work, the total-ionizing-dose-induced degradation of two switching power converters is examined. The MOSFETs for two switching converters were irradiated with a ⁶⁰Co source and their performance was evaluated in buck and boost converters. The experimental results agree well with values obtained from SPICE simulations.     

A Compensation Technique for Smooth Transitions in a Noninverting Buck–Boost Converter

With the advent of battery-powered portable devices and mandatory adoption of power factor correction, noninverting buck-boost converters are garnering lots of attention. Conventional two-switch or four-switch noninverting buck-boost converters choose their operation modes by measuring input and output voltage magnitude. The criterion for the selection of the operation mode can cause higher output voltage transients in the neighborhood, where input and output are close to each other. For the mode selection, due to the voltage drops raised by the parasitic components, it is not enough just to compare the magnitude of input and output voltages. In addition, the difference in the minimum and maximum effective duty cycles between controller output and switching device yields discontinuity at the instant of mode change. Moreover, the different properties of output voltage versus a given duty cycle of buck and boost operating modes contribute to the output voltage transients. In this paper, the effect of the discontinuity due to the effective duty cycle derived from the device switching time at the mode change is analyzed. A technique to compensate the output voltage transient due to this discontinuity is proposed. In order to attain additional mitigation of output transients and a linear input/output voltage characteristic in buck and boost modes, the linearization of DC gain of the large-signal model in boost operation is analyzed as well. Analytical, simulation, and experimental results are presented to validate the proposed theory.     

Steady-state analysis and design of a buck zero-current-switchingresonant DC/DC converter

An analytic basis is provided for a buck high-efficiency high-frequency zero-current-switching resonant DC/DC power converter. The current and voltage waveforms are derived for the steady-state operation. Design equations are then introduced for the switch duty cycle, maximum switching frequency, DC transfer function, peak currents and voltages, output power, and power conversion capability. Finally, the design procedure is presented along with the advantages and disadvantages of the converter, which are discussed in detail     

A mathematical steady-state design model for fully-integrated boost and buck DC–DC converters

This brief discusses a mathematical steady-state model for fully-integrated boost and buck DC–DC converters, which takes all the significant resistive and dynamic power losses into account. The model provides a reduced calculation time by a factor 30 compared to SPICE. A 2%, or less, deviation in comparison with SPICE is achieved. The validation of the model through the measurements of both a fully-integrated boost and buck converter is demonstrated, resulting in an accuracy for the efficiency of 3 and 4% respectively.     

On Differential Flatness, Trajectory Planning, Observers, and Stabilization for DC–DC Converters

Differential flatness of buck, buck–boost, and boost converter models is shown. Its benefits if used for controlling the output voltage of these converters are revealed by comparing the flatness-based control with passivity-based and linear control. Two observers for the boost converter are suggested one of which requires only the measurement of the converters output voltage. Both observers can be used with minor changes for the buck–boost converter. Two flatness-based online trajectory planning algorithms are suggested. They exploit the parametrization of the trajectories in the energy. One of them is designed to achieve fast setpoint transitions during converter start-up or despite sudden load steps while simultaneously respecting the converters physical constraints. The other one is considered for applications in power factor correction. Different stabilization strategies are compared. The viability of the observers, the algorithm, and the stabilization strategies are verified by simulations of switched nonideal converter models.     

A quadratic buck converter with lossless commutation

High switching frequency associated with soft commutation techniques is a new trend in switching converters. Following this trend, the authors present a buck pulsewidth modulation converter, where the DC voltage conversion ratio has a quadratic dependence on duty cycle, providing a large step-down. By introducing two resonant networks, soft switching is attained, providing highly efficient operating conditions for a wide load range at high switching frequency. Contrary to most of the converters that apply soft-switching techniques, the switches presented are not subjected to high switch voltage or current stresses and, consequently, present low conduction losses. The authors present, for this converter, the principle of operation, theoretical analysis, relevant equations and simulation and experimental results     

Single-inductor dual-output (SIDO) DC–DC converters for minimized cross regulation and high efficiency in soc supplying systems

A compact size and high efficiency single-inductor dual-output (SIDO) DC–DC converter is proposed. The proposed SIDO DC–DC converter not only provides dual output sources (one buck and one boost outputs) but also has minimized cross regulation without using any external compensation components. Generally speaking, it is important to minimize the number of components and footprint area in the design of SIDO converters. However, usually large external compensation resistors and capacitors are required to stabilize DC–DC converters. Importantly, our proposed hysteresis mode operation can effectively avoid the oscillation problems that may exist in many SIMO designs. Furthermore, the dynamic dc current level like that in the continuous conduction mode (CCM) operation can make the proposed SIDO DC–DC converter achieve high conversion efficiency at light loads owing to small conduction loss. Experimental results show a high efficiency from 85% at light loads to 94% at heavy loads.     

Optimal feed-forward compensation for PWM DC/DC converters with`linear' and `quadratic' conversion ratio

An analytical procedure to optimize the feedforward compensation for any PWM DC/DC power converters is described. Achieving zero DC audiosusceptibility was found to be possible for the buck, buck-boost, Cuk, and SEPIC cells; for the boost converter, however, only nonoptimal compensation is feasible. Rules for the design of PWM controllers and procedures for the evaluation of the hardware-introduced errors are discussed. A PWM controller implementing the optimal feedforward compensation for buck-boost, Cuk, and SEPIC cells is described and fully experimentally characterized