高频软开关PWM功率变换技术的发展与现状

本文介绍了三类零电压软件开关ＰＷＭ变换器和两类零电流软件开关ＰＷＭ变换器的特点和工作原理。     

Engineering design of lossless passive soft switching methods for PWM converters. II. With nonminimum voltage stress circuit cells

This paper proposes the analysis and design methodology of lossless, passive soft switching methods for PWM converters. The emphasis of the design and analysis is for PWM converters that use nonminimum voltage stress (non-MVS) circuit cells to provide soft switching. PWM converters with non-MVS circuit cells have several distinct advantages over converters that use minimum voltage stress (MVS) cells. With the same relative size of the inductor and capacitor added for soft switching, the non-MVS cells have a substantially larger duty ratio range where soft switching is guaranteed. In addition, the overcurrent stress of the main switch, under most conditions, will be lower and an optimum value of inductor and capacitor added for soft switching can be used. Therefore, with proper design, the non-MVS cells provide higher efficiency. These advantages are obtained with the price of higher switching voltage stress and one additional inductor. The loss model for a MOSFET and optimum capacitor and inductor values are utilized in the design procedure. Examples of the design procedure are given for PFC and DC-DC applications. Experimental results backup the claim of higher efficiency.     

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     

直流电－直流电开关变流器的统一建模方法

提出一种能通用于脉宽调制（ＰＷＭ）型，准谐振型，桥式串（并）联谐振型等各类开关变流器的统一建模方法，脉冲波形积分法。本法能充分反映各类变流器的自身特点，为变流器动态性能指标的分析与设计提供统一衡量标准，文中以两种类型变流器为例阐明建模原理，并将建模结果与有关文献进行比较，计算机仿真结果证明所建模型是正确的。     

Nonlinear modeling of the PWM switch

The nonlinearity due to the switching action in pulse-width-modulated (PWM) DC-to-DC converters, DC-to-AC inverters, or amplifiers and input-current-shaping AC-to-DC converters can often conveniently be confined to three-terminal structure referred to as the PWM switch. The PWM switch represents a static nonlinearity for which circuit models can easily be derived for frequencies harmonically related to the frequency of perturbation. Converter analysis can thus be approached in a way analogous to ordinary transistor circuit analysis whereby the nonlinear three-terminal device is replaced by its circuit model. A first-order approximation of the model results in the small-signal model     

Novel zero-current-switching (ZCS) PWM switch cell minimizingadditional conduction loss

This paper proposes a new zero-current-switching (ZCS) pulsewidth modulation (PWM) switch cell that has no additional conduction loss of the main switch. In this cell, the main switch and the auxiliary switch turn on and turn off under zero-current condition. The diodes commutate softly and the reverse-recovery problems are alleviated. The conduction loss and the current stress of the main switch are minimized, since the resonating current for the soft switching does not flow through the main switch. Based on the proposed ZCS PWM switch cell, a new family of DC-to-DC PWM converters is derived. The new family of ZCS PWM converters is suitable for the high-power applications employing insulated gate bipolar transistors. Among the new family of DC-to-DC PWM converters, a boost converter was taken as an example and has been analyzed. Design guidelines with a design example are described and verified by experimental results from the 2.5 kW prototype boost converter operating at 40 kHz     

Symbolic analysis methods for averaged modeling of switching powerconverters

Symbolic analysis methods for the averaged modeling of switching power converters are presented in this paper. A general averaging method suitable for computer-aided modeling is discussed first. Then, a symbolic analysis package that uses this averaging method to automatically generate an analytical averaged model for a switching power converter is described. The package is implemented using the computer algebra system Mathematica and can be used for modeling DC/DC power converters employing different switching techniques, including hard-switching pulse-width modulation (PWM), quasi-resonant soft switching, and soft transition. Several examples are provided to demonstrate the applications of the package. Further applications of symbolic analysis methods in power electronics are also discussed     

基于PWM变换器的新型无源无损软开关

详细分析了一种基于PWM变换器的新型无源无损软开关，并给出了其最优化设计步骤。通过一台满载输出功率为900w的带有该无源无损软开关的Boost变换器验证了其开关管实现零电流开通和零电压关断，并与传统的Boost变换器比较，验证其具有较高的效率。     

A zero-voltage-switched PWM boost converter with an energyfeedforward auxiliary circuit

A zero-voltage-switched (ZVS) pulsewidth-modulated (PWM) boost converter with an energy feedforward auxiliary circuit is proposed in this paper. The auxiliary circuit, which is a resonant circuit consisting of a switch and passive components, ensures that the converter's main switch and boost diode operate with soft switching. This converter can function with PWM control because the auxiliary resonant circuit operates for a small fraction of the switching cycle. Since the auxiliary circuit is a resonant circuit, the auxiliary switch itself has both a soft turn on and turn off, resulting in reduced switching losses and electromagnetic interference (EMI). This is unlike other proposed ZVS boost converters with auxiliary circuits where the auxiliary switch has a hard turn off. Peak switch stresses are only slightly higher than those found in a conventional PWM boost converter because part of the energy that would otherwise circulate in the auxiliary circuit and drastically increase peak switch stresses is fed to the load. In this paper, the operation of the converter is explained and analyzed, design guidelines are given, and experimental results obtained from a prototype are presented. The proposed converter is found to be about 2%-3% more efficient than the conventional PWM boost converter     

Characteristic curves for analysing limit cycle behaviour inswitching converters

The concept of characteristic curves (CCs) for analysing the behaviour of limit cycles in elementary DC-DC switching converters is introduced. The CC is derived by considering opposite vector fields in the on and off configurations. Feedback regulated converters with PWM or hysteresis control are investigated using this approach     

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     

Resonant link bidirectional power converter. I. Resonant circuit

This paper proposes a novel resonant circuit capable of PWM operation with zero switching losses. The resonant circuit is aimed at providing zero voltage intervals in the DC link of the PWM converter during the required converter device switching periods, and it gives minimum DC bus voltage stresses and minimum peak resonant current. It requires only two additional switches compared to a conventional PWM converter. It is observed that the resonant circuit guarantees the soft switching of all the switching power devices of converters including the switches for resonant operation. Simulation results and experimental results are presented to verify the operating principles     

Engineering design of lossless passive soft switching methods forPWM converters. I. With minimum voltage stress circuit cells

This paper presents the analysis and design methodology of lossless passive soft switching converters from an engineering perspective. The circuit operation and soft switching loss analysis are detailed and an intuitive procedure is derived that enables quick and accurate design. Analysis is given for a set of soft switching circuit cells with minimum switch voltage stress used to synthesize a family of soft switching converters. The design is based on minimizing switching losses while maintaining soft switching over the desired operating range. A new simple loss model is derived to optimize the values of the resonant components for a particular design. As an example of the design procedure, a PFC boost converter is designed and tested     

Function control-a novel strategy to achieve improved performanceof the DC-to-DC switching regulators

The control strategy of the DC-to-DC switching converters is studied to obtain the switching regulators with zero-voltage regulation. A novel control strategy, the function control, is presented for the DC-to-DC switching converters to achieve this objective. The control law and the corresponding feedback are derived directly from the equations governing the switching converters. With the function control strategy presented in the paper, the switching regulators become robust, i.e., the output is independent of the disturbances from either the supply voltage or the load and exhibits other desirable advantages. The strategy is applicable to all the four basic PWM converters, i.e., buck, boost, buck-boost, and Cuk. The analysis is confirmed by experiments and computer simulations     

Multifunctional Grid-Connected Multimodule Power Converters Capable of Operating in Single-Pulse and PWM Switching Modes

Pulsewidth-modulated (PWM) techniques equip power converters with unique features such as input-output linearity and control flexibility. Nevertheless, frequent switching of semiconductor switching devices causes considerable switching loss, and therefore makes traditional two-level PWM converters inappropriate for high-power applications. Two alternatives for building modular structures, namely multipulse and multimodule PWM converters were introduced to provide not only voltage and current sharing among the semiconductor switching devices, but also a high-quality output voltage at a much lower switching frequency. While multipulse converters offer minimal switching losses, low-order harmonic neutralization, and the best utilization of the inverter, multimodule PWM converters give control flexibility and power structure simplicity. This paper combines these two, and preserves the advantages of both multipulse and multimodule PWM converters. This not only provides an additional degree of freedom for voltage control, but also enables the converter to operate in PWM mode during transient and in single-pulse mode during the steady state. For the PWM switching mode, a special space vector strategy of 3 p.u. switching frequency is presented to maximize the voltage utilization and maintain a linear transfer characteristic. The power structure and control methods are analyzed, and validated by simulation and experimentally.     

State-space models for current programmed pulsewidth-modulatedconverters

State-space models are derived for pulse-width-modulated (PWM) converters operating at constant switching frequency under current programmed control. One model neglects the sample-and-hold effect of the current loop and is therefore representative of the traditional approach to modeling current programmed converters. The order of the model is the same as that of the power stage. A second state-space model is derived which incorporates the sample-and-hold effect. The order of this model is two higher than that of the power stage. A comparison of the two models is made which clearly demonstrates the superiority of the second modeling approach. As the models are in state-space form they may be quite readily used in a CAD package for general converter analysis and design, to determine all transfer functions and associated pole/zero locations of interest     

Modeling of single-stage converters with high power factor and fastregulation

This paper presents an approach to systematically model single-stage DC/DC converters operated in discontinuous conduction mode (DCM) based on the graft scheme. With the graft scheme, the active switches which are with a common node and operating in unison can be integrated to form a single stage converter (SSC). The small-signal models of the SSC can, therefore, be derived by combining those of its originally separate converters. Using the proposed approach can help yield highly related dynamic models of the converters in a family and, in addition, physical insights between the converters can be readily identified. Moreover, the expressions of the small-signal models for the SSCs operated in DCM can be extended to those in continuous-conduction-mode operation. These have made the proposed modeling method valuable and viable. Experimental measurements have demonstrated that the small-signal model of an SSC derived with the proposed approach is relatively accurate     

High-frequency quasi-resonant converter technologies

Resonant switch topologies operating under the principle of zero-current switching (ZCS) and zero-voltage switching (ZVS) are introduced to minimize switching losses, stresses, and noises. Using the resonant switch concept, a host of new quasi-resonant converters (QRCs) are derived from conventional PWM converters. They are capable of operating in the megahertz range, with a significant improvement in performance and power density. Performances of ZCS and ZVS QRCs are compared. Power stages, gate drives, and feedback controls are discussed     

Technique for sensing inductor and DC output currents of PWM DC-DCconverter

The design, analysis and trade-offs of a novel method to sense the inductor and DC output currents of PWM converters are presented. By sensing and adding appropriately the currents in the transistor, rectifier and capacitors of a converter using current transformers, the waveforms of inductor and DC output currents can be reconstructed accurately while maintaining isolation. This method offers high bandwidth, clean waveform, practically zero power dissipation and simple circuit. The technique is applicable to all PWM converters in both continuous and discontinuous modes, and is most suitable for the implementation of current mode control schemes like hysteretic, PWM conductance control, and output current feedforward. This approach has been experimentally verified at a wide range of current levels, duty cycles, and switching frequencies up to 1.4 MHz