Effect of FET output capacitance on ZVS of resonant converters

The analysis of resonant converters including the capacitance of the switches is presented. New dc characteristics are obtained for the series, parallel, and series-parallel resonant converters (SPRC). The operating regions where the converters operate with zero-voltage switching (ZVS) are determined as a function of the switch capacitance. The more pronounced effect can be seen in the series resonant converter (SRC), while the parallel resonant converter (PRC) is the most insensitive. The results of the analysis have been verified on an experimental prototype     

并联H桥DC/DC变换器软开关技术研究

与传统的Buck电路相比,基于H桥并联的DC/DC变换器可以实现电压的双极性输出和故障时的冗余控制,非常适合用于大功率电动机正反转控制的场合。分析了并联H桥型DC/DC变换器的结构组成和双脉宽调制(PWM)模式。为了降低双脉宽调制下H桥型DC/DC变换器的开通和关断损耗,对无源软开关技术进行了分析,重点探讨了RCD缓冲电路和最小应力缓冲电路之间的性能差异,指出最小应力软开关技术可以获得更好的软开关性能,并就将其用于双脉宽调制下的并联H桥DC/DC变换器进行了仿真研究。仿真结果表明:最小应力软开关技术用于双脉宽调制下并联H桥DC/DC变换器时,可以实现开关管的零电压开通和零电流关断。     

Simplified analysis of PWM converters using model of PWM switch.Continuous conduction mode

A circuit-oriented approach to the analysis of pulsewidth modulation (PWM) converters is presented. This method relies on the identification of a three-terminal nonlinear device, called the PWM switch, which consists of only the active and passive switches in a PWM converter. Once the invariant properties of the PWM switch are determined, its average equivalent circuit model can be derived. This model is versatile enough to easily account for storage-time modulation of bipolar junction transistor(s) (BJTs); the DC- and small-signal characteristics of a large class of PWM converters can then be contained by a simply replacing the PWM switch with its equivalent circuit model. The methodology is very similar to linear amplifier circuit analysis, whereby the transistor is replaced by its equivalent circuit model     

Improved ZCS-PWM commutation cell for IGBTs application

An improved zero-current-switching pulsewidth-modulated (ZCS-PWM) commutation cell is presented, which is suitable for high-power applications using insulated gate bipolar transistors (IGBTs) as the power switches. It provides ZCS operation for active switches and zero-voltage-switching (ZVS) operation for passive switches. Besides operating at constant frequency and reducing commutation losses, the proposed ZCS-PWM switch cell has no additional current stress and conduction loss in the main switch. To demonstrate the feasibility of the proposed ZCS-PWM commutation cell, it was applied to a boost converter. Operating principle, theoretical analysis, design guidelines, and a design example are described and verified by experiment results obtained from a prototype rated 1 kW and operating at 40 kHz. The PWM switch model and state-space averaging approach is also used to estimate and examine the steady-state and dynamic character of ZCS-PWM boost converter system. Finally, the application of the proposed soft-switching technique in the dc-dc nonisolated converters is presented.     

Single-stage converters for PV lighting systems with MPPT andenergy backup

Single-stage converters (SSCs) are proposed for applications of photovoltaic powered lighting system (PPLS). The synchronous switch technique is employed to develop the SSCs which can fulfill maximum power point tracking (MPPT), battery charging, discharging, and lamp ballasting features. Several typical SSCs are discussed. One of the proposed SSCs, which is the integration of a buck-boost charger/discharger and a class-D series resonant parallel loaded inverter, is analyzed and designed into a PPLS. Both pulsewidth modulation (PWM) and variable-frequency controls are used to govern the system operation. The controller is implemented on a single-chip microprocessor. Simulated and experimental results of the proposed system for driving up to sixteen GE TBX 26 W fluorescent lamps are used to verify the theoretical prediction and feasibility. The proposed system has a simple configuration, as well as a zero voltage switching (ZVS) feature, and can achieve the same functions as those in conventional systems when abrupt insolation changes do not occur frequently. These result in the inherent merits of lower cost, more compact size and possibly achieving higher reliability over conventional systems     

Resonant power supplies: their history and status

The various types of converter are described, and the history of resonant power supplies is briefly sketched. The differences between pulse-width-modulated (PWM) switch mode power supplies and resonant power supplies are discussed. Single-switch, multiple-switch, and series and parallel resonant converters are examined. The control of resonant converters is addressed. Hardware is briefly considered     

Motor drive technologies for the Power-By-Wire (PBW) program:options, trends and tradeoffs. II. Power electronic converters anddevices

For pt. I see ibid., vol. 10, pp. 37-41 (1995). This is the second of two papers on the motor drive technology options for the Power-By-Wire (PBW). The organization of this paper is based on the four components of the electrical actuator (EA) system and the options available to suit the PBW program as given in the PBW studies. The first paper discussed the options available for the motor and the controller parts of a drive. This paper discusses the power electronic converter and device options. The power converter options are divided into hard-, snubbered- and soft-switching converters. The power device options are the MOSFET, the Insulated Gate Transistor (IGT), the gate turn-off thyristor (GTO) and the MOS Controlled Thyristor (MCT)     

Optimum Design of RC Snubbers for Switching Regulators

The optimum design of an RC snubber to suppress the surge voltage across the transistor in a switching regulator with a two-winding reactor is presented. Analyzing the surge voltage by means of high-frequency equivalent circuits, we obtain the third-order characteristic equation. This third-order equation is first analyzed by the aid of the root locus method. As a result, the region where the surge voltage can be suppressed is described in the R-C plane. Then considering the snubber loss, the optimum resistance and capacitance can be obtained. Second, the precise design procedure of RC snubbers is discussed by normalization and numerical calculations. This procedure is summarized in easy-to-use nomographs.     

Alternate forms of the PWM switch models

Vorperian's pulsewidth modulation (PWM) switch model consists of a PWM transformer and a nonlinear resistor. The recognition that any of the three transformer terminals can serve as the common terminal leads to two alternate PWM transformer models and the corresponding two alternate PWM switch models. For a given PWM dc-dc converter, one of the three PWM switch models is more “natural” for graphic-oriented analysis/design, e.g., it allows the idealized converter to be analyzed by inspection. Furthermore, all three PWM transformers may be used to graphically manipulate the converter circuit to a form that can be analyzed by inspection. The alternate forms of the PWM transformers and the PWM switch models are effective as graphic-oriented teaching and learning tools for PWM converters. This is demonstrated using examples based on the boost converter and the Cuk converter     

Turn-Off Characteristics of Power Transistors Using Emitter-Open Turn-Off

As compared with conventional reverse-biased turn-off, emitteropen turn-off provides superior transistor turn-off characteristics. Not only are the storage time and the fall time of the power transsistors much reduced, but also the device reverse-biased second breakdown phenomenon, commonly associated with turn-off of inductive load, is eliminated. Furthermore the storage time tolerance due to device variation and temperature change is minimized.     

Comparison of resonant topologies in high-voltage DC applications

Because of their tolerance of transformer nonidealities, resonant converters are considered to be well-suited to high-voltage applications. The series and parallel resonant topologies, as well as a newly discovered hybrid resonant topology are compared for high-voltage applications. Design criteria which incorporate transformer nonidealities are developed and used in the construction of high voltage prototypes for each topology. It is found that the parallel topology leads to the lowest peak switch current and the most ideal behavior     

A New Resonant Mode Amplifier Produces Clean AC Power

A new resonant mode power amplifier design is described which has a number of advantages over the power amplifiers available today. In particular, it has low or no EMI because of the nature of its operation. The new amplifier design is based upon a resonant mode dc-dc converter used in a push-pull configuration. All the advantages of the resonant mode power converters, such as high efficiency, small size and weight, excellent dynamic performance, low or no EMI (compared to PWM switch mode power converter), etc., are present in this new design.     

Computer Simulations of Optimum Boost and Buck-Boost Converters

The development of mathematical models suitable for minimum weight boost and buck-boost converter designs are presented. The facility of an augumented Lagrangian (ALAG) multiplier-based nonlinear programming technique is demonstrated for minimum weight design optimizations of boost and buck-boost power converters. ALAG-based computer simulation results for those two minimum weight designs are discussed. Certain important features of ALAG are presented in the framework of a comprehensive design example for boost and buck-boost power converter design optimization. The study provides refreshing design insight of power converters and presents such information as weight and loss profiles of various semiconductor components and magnetics as a function of the switching frequency.     

并联交错式有源箝位正激变换器研究

深入分析研究了并联交错式有源箝位正激变换器的原理与设计 ,获得了功率开关实现零电压 ZVS开通的条件和关键电路参数选取准则 ,仿真与试验结果均证实了理论分析的正确性。研究结果表明 ,并联交错式有源箝位正激变换器具有优良的电气性能 ,特别适用于大功率分布式电源系统     

New ZVT-PWM DC/DC converters using active snubber

A novel active snubber soft switching method is proposed. The unique location of the resonant inductor and capacitor ensures low current and voltage stresses in the converter. An analytical study of a boost dc-dc converter with the proposed active snubber method is presented in detail to illustrate its operation principles and design considerations. By simple modification, this soft switching method is also suitable for ac-dc boost topology, especially for high power-factor-correction (PFC) universal interface applications. A 500 W prototype system has been made to simulatively and experimentally verify the performance of the soft switching.     

Low-Frequency Characterization of Switched dc-dc Converters

Averaging techniques are developed to represent buck, boost, and buck-boost types of switched dc-dc converters by approximate continuous models. Simple analytical expressions in terms of the circuit components are derived for the characteristic transient and frequency responses of time-average(continuous) power-stage models for use in designing and understanding the behavior of corresponding switched power stages. Novel conclusions include the dependence of effective circuit component values upon switch duty ratio and the existence of a real positive zero in certain transfer functions. Responses from analog computer simulations of the switched and averaged powerstages agree well and, in turn, confirm the analytic predictions. High-order systems can be analyzed by the averaging technique without a commensurate increase in complexity.     

Unified approach to developing single-stage power converters

A unified approach to developing single-stage power converters which can fulfil multiple functions is presented. Four synchronous switches corresponding to the four common node types of two active switches are introduced. The approach is then to replace the active switches in multistage converters (in cascade or cascode connection) with one or several of the synchronous switches and their degenerated versions to form a single-stage converter. Illustrations of using these switches to develop single-stage converters are presented. These are started with the development of the well-known single-stage switch-mode converters (SMCs), buck-boost, Cuk, sepic, and Zeta (also named dual sepic), from the basic converters, buck and boost. Then, synthesis and applications of other single-stage converters are addressed. Due to increased component stresses, the developed single-stage converters are primarily suitable for applications with moderate power levels     

一种新型航空静止变流器的研究

 提出了一种新型的航空静止变流器方案, 采用分布式电能变换技术, 系统由规格统一、种类有限的印刷线路板构成, 没有高压功率器件, 可以克服目前静止变流器技术能量集中变换和结构复杂等缺点。变流器由4 个推挽正激变换器和4 级级联逆变器组成。分析了系统的工作原理和控制方案。研制的原理样机验证了该静止变流器具有效率高、输出波形质量好、可靠性高、工程实现简便等特点。     

High-performance front-end converter for avionics applications [aircraft power systems]

The distributed power systems of future commercial aircraft will adopt variable frequency generation (360 to 800 Hz). Front-end converters in the system will be required to have a high efficiency and a low total harmonic distortion (THD) of the input current. This paper explains the design of a zero-voltage-switching (ZVS) active-clamped isolated low-harmonic SEPIC rectifier for such applications. Utilization of the transformer leakage inductance for ZVS and a single-layer transformer design contribute to a high efficiency. An accurate averaged switch model has been developed, which shows that the control-to-input-current transfer function of this converter does not exhibit resonances observed in the conventional SEPIC. As a result, for closed-loop operation using average current control, damping of the coupling capacitor is not required. Operating at a switching frequency of 200 kHz, an experimental 100 W, 28 V output rectifier achieves a THD of 3-4% and efficiency exceeding 90% over the entire line frequency range.