Novel ZVT-PWM converters with active snubbers

An active snubber cell is proposed to contrive zero-voltage-transition (ZVT) pulsewidth-modulated (ZVT-PWM) converters. Except for the auxiliary switch, all active and passive semiconductor devices in a ZVT-PWM converter operate at zero-voltage-switching (ZVS) turn on and turn off. The auxiliary switch operates at ZVS turn off and near zero current-switching (ZCS) turn on. An analytical study on a boost ZVT-PWM converter with the proposed active snubber cell is presented in detail. A 750 W 80 kHz prototype of the boost ZVT-PWM converter has been built in the laboratory to experimentally verify the analysis. Six basic ZVT-PWM converters can be easily created by attaching the proposed active snubber cells to conventional PWM converters. A detailed design procedure of the proposed active snubber cell is also presented in this paper     

Zero-voltage switching technique in DC/DC converters

A novel resonant switch operating under the principle of zero-voltage switching is presented. The basic configurations of the voltage-mode resonant switches are presented. The circuit's operating principles are described using a voltage-mode quasi-resonant boost converter. DC analysis of the converter is carried out. A new family of voltage-mode quasi-resonant converters are derived, and several members of this family are presented. The duality relationship between the zero-current switching technique and the zero-voltage switching technique is derived. These two techniques are compared using an example showing the duality between a current-mode quasi-resonant Buck converter and a voltage-mode quasi-resonant boost converter. The similarities and differences of the voltage-mode quasi-resonant converters and the Class-E converters are discussed. A 5 MHz 50 V to 5 V flyback converter employing the zero-voltage switching technique has been implemented. Design considerations and experimental results of this circuit are presented     

Active-clamp snubbers for isolated half-bridge DC-DC converters

In conventional isolated half-bridge dc-dc converters, the leakage-inductance-related losses degrade converter efficiency and limit the ability to increase the converters' switching frequencies. In this paper, a novel active-clamp snubber circuit for half-bridge dc-dc converters is proposed to recycle the energy stored in the leakage inductance by transferring this energy to a capacitor with zero-voltage zero-current-switching switched auxiliary switches, such that body-diode conduction of primary-side main switches are prevented and primary side ringing are attenuated resulting in improved converter efficiency. Principles of operation and simulation analysis are presented and supported by experimental results that show significant improvement in efficiency.     

Design-oriented analysis of common switching DC to DC converters

A general, computer-aided analysis of power electronic circuit dynamics is proposed. An automatic generation of dynamic models from a circuit specification is the starting point for a symbolic, automatable, exact, ‘top-down’ procedure, that contrasts with circuit-specific analyses. The algorithm is suitable for analysing any converter containing two reactive elements, covering the common switching power stages: buck, boost, buck-boost converters. The method is illustrated by application to the computation of the transient response of a boost converter; the computer results are compared with those obtained by applying the ‘state space averaging’ method and with laboratory results.     

DC/DC变换器的PWM控制技术

ＤＣ／ＤＣ变换器广泛应用于便携装置（如笔记本计算机、蜂窝电话、寻呼机、ＰＤＡ等）中。它有两种类型,即线性变换器和开关变换器。开关变换器因具有效率高、灵活的正负极性和升降压方式的特点,而备受人们的青睐。开关稳压器利用无源磁性元件和电容电路元件的能量存储特性,从输入电压源获取分离的能量,暂时地把能量以磁场形式存储在电感器中,或以电场形式存储在电容器中,然后将能量转换到负载,实现ＤＣ／ＤＣ变换。开关稳压器的框图示于图１。实现能量从源到负载的变换需要复杂的控制技术。现在,大多数采用ＰＷＭ（脉冲宽度调制）…     

Computer-aided small-signal analysis based on impulse response ofDC/DC switching power converters

The paper describes a method for automated small-signal frequency response analysis based on transient response obtained using a general-purpose simulation tool such as simulation program with integrated circuit emphasis (SPICE). The method is based on using the simulation tool to evaluate the converter impulse response. The main advantage of the proposed method as a design verification tool is that frequency responses can be generated efficiently for any converter configuration and any model complexity supported by the general-purpose simulator. Application examples are included to demonstrate very good correlation between the generated responses and experimental data, and to compare the results with predictions of approximate analytical methods. In particular, the method is applied to investigate high-frequency dynamics of pulse width modulation (PWM) converters operating in discontinuous conduction mode, and the results are used to compare and validate several existing analytical modeling approaches     

Benchmark of power packaging for DC/DC and AC/DC converters

This paper presents the first reported final results of a benchmarking project "StatPEP" which investigated the Status of Power Electronic Packaging used in commercial DC/DC and AC/DC switch mode power supplies. The methodology of the project is first described. Some of the salient results of a comprehensive benchmarking of DC/DC converters (rated power of 100 W) and AC/DC converters (rated power up to 576 W) are presented. Examples for figures-of-merit are presented. The results of the investigation are presented in a generic form, which does not identify individual products. A comparison of the performance of the units shows that the measured power density of the AC/DC units is approximately 10% that of the DC/DC while the thermal density based on footprint is 50%. Also the switching frequency of the AC/DC is 50% that of the DC/DC. Some of the reasons for these differences are discussed     

Multifrequency averaging of DC/DC converters

This paper presents some of the issues involved in applying frequency-selective averaging to modeling the dynamic behavior of pulsewidth-modulated (PWM) DC-DC converters. We use the boost converter as an example to show the details involved in deriving some novel extended averaged models, and we use simulations to highlight the accuracy of the models even when traditional small-ripple conditions are not satisfied     

Computer-aided optimization of DC/DC converters for automotive applications

This paper investigates computer-aided optimization of DC/DC converters, with a focus on converters for dual-voltage automotive electrical systems. A new CAD optimization approach based on Monte Carlo search methods is introduced which allows the design space to be rapidly explored in an automated fashion and the most optimal designs and design approaches to be identified. The optimization approach also allows the effects of variations in design specifications on the cost, weight, and volume of an optimized converter to be readily determined. A prototype converter designed using this optimization procedure is evaluated and compared to a converter designed by conventional means.     

Zero-voltage-ripple rectifiers and DC/DC resonant converters

Class E zero-voltage-ripple (ZVR) rectifiers are introduced. The proposed circuits offer a new means of a significant improvement in suppressing the output voltage ripple compared with their predecessors. Therefore, the size of the output filter can be considerably reduced, the rI_rms² conduction power loss in the equivalent series resistance of the filter capacitor can be lowered, aluminum or tantalum electrolytic capacitors may be entirely eliminated, filter capacitors with low capacitances and thereby high self-resonant frequencies can be used, and a faster dynamic response becomes achievable. ZVR is accomplished by reducing the AC component of the current at the input of the output filter. Class E² and Class D-E ZVR resonant DC/DC power converters are derived using the Class E ZVR rectifiers. An experimental prototype of a Class E² 30 W/500 kHz DC/DC converter was built and tested. Its output voltage ripple was as much as 20 times lower than that of the corresponding conventional converter. The new converters are suitable for noise-sensitive high-output-current applications     

航天器DC/DC变换器热分析研究

为了解决航天器DC/DC变换器的热可靠性问题,利用有限元分析软件ANSYS对实际的航天器DC/DC变换器进行热仿真分析,得到了其内部的温度分布特性。并对其进行了红外成像测试实验,通过红外成像测试结果与仿真分析结果对比分析,验证了热仿真的准确性。使用有限元分析方法为航天器DC/DC变换器合理热设计提供了依据,也为同类电子设备的热设计提供了一种思路。     

轻松选择DC/DC变换器

分布式供电体制(distributed-power architectures,DPA)的盛行,极大地促进了集成DC/DC变换器的发展。本文主要讲述了DC/DC变换器在评测、对比和选型时的需要注意的问题,以协助DPA设计人员在市场上挑选出合适的产品。功率、输入和输出首先要考虑的是输入电压、额定功率以及输出电压的大小和种类。根据额定功率的大小,DC/DC变换器通常可分为超低功率(1W以下)、小功率(1～9W)、中功率(10～150W)和大功率(150W以上)等类别。大多数变换器的输入电压是12V或24V,对于那些要求输入电压可变或者输入电压不标准的场合,可以选用具有宽电源输…     

Lateral power MOSFET for megahertz-frequency, high-density DC/DC converters

DC/DC converters to power future CPU cores mandate low-voltage power metal-oxide semiconductor field-effect transistors (MOSFETs) with ultra low on-resistance and gate charge. Conventional vertical trench MOSFETs cannot meet the challenge. In this paper, we introduce an alternative device solution, the large-area lateral power MOSFET with a unique metal interconnect scheme and a chip-scale package. We have designed and fabricated a family of lateral power MOSFETs including a sub-10 V class power MOSFET with a record-low R/sub DS(ON)/ of 1m/spl Omega/ at a gate voltage of 6V, approximately 50% of the lowest R/sub DS(ON)/ previously reported. The new device has a total gate charge Q/sub g/ of 22nC at 4.5V and a performance figures of merit of less than 30m/spl Omega/-nC, a 3/spl times/ improvement over the state of the art trench MOSFETs. This new MOSFET was used in a 100-W dc/dc converter as the synchronous rectifiers to achieve a 3.5-MHz pulse-width modulation switching frequency, 97%-99% efficiency, and a power density of 970W/in/sup 3/. The new lateral MOSEFT technology offers a viable solution for the next-generation, multimegahertz, high-density dc/dc converters for future CPU cores and many other high-performance power management applications.     

Switched-capacitor DC/DC converters with resonant gate drive

In this paper, we examine how switched-capacitor (SC) converters can be used in low-voltage low-power DC/DC applications with power management. Analysis of losses is presented to facilitate SC converter design and optimization. A resonant gate drive is proposed to reduce switching losses and simplify control of switches in SC converters. A closed-loop controller is designed to enable and disable oscillations of the resonant gate drive so that the output DC voltage is well regulated down to zero load and so that high efficiency is maintained for a very wide range of loads. Results are experimentally verified on two low-power (0.2 and 5 W) five-one step-down converters with regulated 3 Vdc output and efficiency greater than 80% in a 100-1 load range     

Class-E DC/DC converters with a capacitive impedance inverter

Analysis and design rules are presented for three class-E switching-mode DC/DC power converters, each with a capacitive impedance inverter. Experimental results are given for one of the converters. A zero-voltage switching technique is achieved for both class-E inverters and rectifiers. Therefore, the efficiency of the converters is very high at switching frequencies in the megahertz range. By applying a capacitive impedance inverter, lossless operation of the class-E inverter can be obtained for a wide range of converter load resistance, from full load to infinity. Experimental results are in excellent agreement with the theoretical calculations. Only a 12% relative bandwidth of the switching frequency is required to maintain a constant DC output voltage for the load resistance from full load to infinity at about 1 MHz with 15-W output     

A comparative study of AC/DC converters for high-power DC arc furnace

Today, dc arc furnaces are supplied by thyristor rectifiers. Because of the phase control strategy on the rectifiers, the arc voltage swings induce large reactive power variations on the power network and a static VAr compensator (SVC) or a static synchronous compensator (STATCOM) is always added to avoid flicker effect. In this paper, the authors present a new control strategy which suppresses the flicker effect and increases the furnace productivity. To supply the dc arc furnace, the ac/dc converter is based on diode rectifiers and choppers with a constant power control strategy. Consequently, the ac/dc converter can operate without a STATCOM or an SVC. To evaluate the gain in flicker and furnace productivity, simulations are done with Matlab software. These simulations take into account arc voltage measurements on a 100-MW dc arc furnace and allow for comparison of the different solutions.     

Current distribution control design for paralleled DC/DC converters using sliding-mode control

This paper shows the analysis and design of a parallel-connected converter system using sliding mode control techniques. The design is particularised for a system that consists of N boost converters and a current feedback loop based on a proportional-integral compensator of the output voltage error. The paper emphasises the advantages of the sliding-mode control over the classic design method based on small-signal models, thus providing an effective and robust means of controlling nonlinear multi-input converters. The design is based on the Utkin conditions, which permit us to know the regions under which a sliding mode exists. This fact allows us to design the compensator and to introduce some modifications in the control loop that avoids input-current overshoots during the system startup. Simple design expressions are obtained and verified with simulation and experimental results, thus showing the improvements achieved with the proposed modifications.     

A capacitor modeling method for integrated magnetic components in DC/DC converters

For the special case of dc/dc converters, the gyrator-capacitor model is revised by replacing gyrators with current sources to symbolize the electrical actions on windings. The revised capacitor model is suitable for analyzing integrated magnetic components. Several examples illustrate the usage of this approach. Comparisons between the revised capacitor model and the conventional reluctance model for magnetic calculation and integration are presented.     

Voltage-source charge-pump power-factor-correction AC/DC converters

Voltage-source charge-pump power-factor-correction (VS-CPPFC) AC/DC power converters are proposed in this paper. The PFC converter using the CP concept is first derived. The unity power factor condition is derived and analyzed. The clamping technique is used to satisfy the unity power factor condition. Based on the steady-state analysis, design considerations for the CPPFC stage are discussed. A family of VS-CPPFC topologies is also presented. The proposed VS-CPPFC AC/DC power converter was implemented and tested. The experimental results show that 83.5% efficiency and 0.996 power factor can be achieved for a half-bridge CPPFC AC/DC converter with 250-W and 12-V output,     

Synthesis of input-rectifierless AC/DC converters

This paper discusses the basic construction procedure and topological possibilities of creating AC/DC converters out of simple DC/DC converters. It is shown that two separately controlled DC/DC converters are sufficient for producing a regulated DC output and shaping the input current, from an AC voltage source, without the need for input rectifiers. Some design constraints are discussed, emanating from the limitation of the conversion ratios that can be achieved by particular DC/DC converters. Selected topologies are verified experimentally. This kind of rectifierless converter find applications in airborne power supplies where zero-crossing distortions are significant because of the inevitable phase-lead effect of the input rectifier bridge.