A true ZCZVT commutation cell for PWM converters

This paper introduces a true zero-current and zero-voltage transition (ZCZVT) commutation cell for DC-DC pulsewidth modulation (PWM) converters operating with an input voltage less than half the output voltage. It provides zero-current switching (ZCS) and zero-voltage switching (ZVS) simultaneously, at both turn on and turn off of the main switch and ZVS for the main diode. The proposed soft-switching technique is suitable for both minority and majority carrier semiconductor devices and can be implemented in several DC-DC PWM converters. The ZCZVT commutation cell is placed out of the power path, and, therefore, there are no voltage stresses on power semiconductor devices. The commutation cell consists of a few auxiliary devices, rated at low power, and it is only activated during the main switch commutations. The ZCZVT commutation cell, applied to a boost converter, has been analyzed theoretically and verified experimentally. A 1 kW boost converter operating at 40 kHz with an efficiency of 97.9% demonstrates the feasibility of the proposed commutation cell     

High-efficiency multiple-output DC-DC conversion for low-voltagesystems

This versatile power converter controller provides dual outputs at a fixed switching frequency and can regulate either output voltage or target system delay (using an external L-C filter). In the voltage regulation mode, the output voltage is monitored with an analog-digital (A/D) converter, and the feedback compensation network is implemented digitally. The generation of the pulsewidth modulation (PWM) signal is done with a hybrid delay line/counter approach, which saves power and area relative to previous implementations. Power devices are included on chip to create the two independently regulated output PWM signals. The key features of this design are its low-power dissipation, reconfigurability, use of either delay or voltage feedback, and multiple outputs     

Zero-voltage-switching half-bridge DC-DC converter with modified PWM control method

Asymmetric control scheme is an approach to achieve zero-voltage switching (ZVS) for half-bridge isolated dc-dc converters. However, it is not suited for wide range of input voltage due to the uneven voltage and current components stresses. This paper presents a novel "duty-cycle-shifted pulse-width modulated" (DCS PWM) control scheme for half-bridge isolated dc-dc converters to achieve ZVS operation for one of the two switches without causing the asymmetric penalties in the asymmetric control and without adding additional components. Based on the DCS PWM control scheme, an active-clamp branch comprising an auxiliary switch and a diode is added across the isolation transformer primary winding in the half-bridge converter to achieve ZVS for the other main switch by utilizing energy stored in the transformer leakage inductance. Moreover, the auxiliary switch also operates at ZVS and zero-current switching (ZCS) conditions. Furthermore, during the off-time period, the ringing resulted from the oscillation between the transformer leakage inductance and the junction capacitance of two switches is eliminated owing to the active-clamp branch and DCS PWM control scheme. Hence, switching losses and leakage-inductance-related losses are significantly reduced, which provides the converter with the potential to operate at higher efficiencies and higher switching frequencies. The principle of operation and key features of the proposed DCS PWM control scheme and two ZVS half-bridge topologies are illustrated and experimentally verified.     

A new single-phase ZCS-PWM boost rectifier with high power factor and low conduction losses

This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching (ZVS) in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved because of the following reasons: 1) the circulating current for the soft switching flows only through the auxiliary circuit; 2) a minimum number of switching devices are involved in the circulating current path; and 3) the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Seven transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM-switch model is used to predict the system performance. A prototype rated at 1 kW, operating at 60 kHz, with an input alternating current voltage of 220 V/sub rms/ and an output voltage of 400 V/sub dc/, has been implemented in laboratory. An efficiency of 98.3% and a power factor over 0.99 have been measured. Analysis, design, and the control circuitry are also presented in this paper.     

适合低压大电流直流输入的软开关局部PDM PWM高频DC-DC功率变换器

本文特别针对24V电池输入条件下的低电压、大电流特性，设计了一种新颖的PWM软开关DC-DC前向式功率变换器模型。在局部运行区域，利用了ZCS PWM DC-DC前向式功率变换器的附加控制模式来实现软开关。这种新型功率变换器在低负载条件下可支持PWM-PDM双模控制方式，研究结果证实，在ZCS和有功电压钳位开关条件下，基于PWM-PDM双模控制的软开关前向式功率变换器可在较大的负载范围内改善运行效率。     

A novel ZCS-PWM power-factor preregulator with reduced conduction losses

This paper proposes a new single-phase high-power-factor rectifier, which features regulation by conventional pulsewidth modulation (PWM), soft commutation, and instantaneous average line current control. A new zero-current-switching PWM (ZCS-PWM) auxiliary circuit is configured in the presented ZCS-PWM rectifier to perform ZCS in the active switches and zero-voltage switching in the passive switches. Furthermore, soft commutation of the main switch is achieved without additional current stress by the presented ZCS-PWM auxiliary circuit. A significant reduction in the conduction losses is achieved, since the circulating current for the soft switching flows only through the auxiliary circuit and a minimum number of switching devices are involved in the circulating current path and the proposed rectifier uses a single converter instead of the conventional configuration composed of a four-diode front-end rectifier followed by a boost converter. Nine transition states for describing the behavior of the ZCS-PWM rectifier in one switching period are described. The PWM switch model is used to predict the system performance. A prototype rated at 1 kW, operating 50 kHz, with an input ac voltage of 220 V/sub rms/ and an output voltage 400 V/sub dc/ has been implemented in laboratory. An efficiency of 97.3% and power factor over 0.99 has been measured. Analysis, design, and the control circuitry are also presented in this paper.     

A new ZVT-PWM DC-DC converter

In this paper, a new active snubber cell that overcomes most of the drawbacks of the normal "zero voltage transition-pulse width modulation" (ZVT-PWM) converter is proposed to contrive a new family of ZVT-PWM converters. A converter with the proposed snubber cell can also operate at light load conditions. All of the semiconductor devices in this converter are turned on and off under exact or near zero voltage switching (ZVS) and/or zero current switching (ZCS). No additional voltage and current stresses on the main switch and main diode occur. Also, the auxiliary switch and auxiliary diodes are subjected to voltage and current values at allowable levels. Moreover, the converter has a simple structure, low cost, and ease of control. A ZVT-PWM boost converter equipped with the proposed snubber cell is analyzed in detail. The predicted operation principles and theoretical analysis of the presented converter are verified with a prototype of a 2 kW and 50 kHz PWM boost converter with insulated gate bipolar transistor (IGBT). In this study, a design procedure of the proposed active snubber cell is also presented. Additionally, at full output power in the proposed soft switching converter, the main switch loss is about 27% and the total circuit loss is about 36% of that in its counterpart hard switching converter, and so the overall efficiency, which is about 91% in the hard switching case, increases to about 97%     

Configurable front-end converters for multicurrent locomotives operated on 16 2/3 Hz AC and 3 kV DC systems

A configurable converter topology is presented as front-end converter for a locomotive that can be operated as well on a high voltage AC-system as on a medium voltage DC-system. The configurable converter is realized on the base of a multilevel chain, where all modules are fed through reversible and isolated DC-DC stages. The medium frequency transformers used in the isolation stages of the DC-DC converters allow a significant weight reduction of the locomotive, in comparison with the classical low-frequency voltage-transformers. A first solution using hard switching techniques is presented, using a three-times silicon-conversion. A second solution based on ZVT/ZCS techniques is then presented, with the advantage of having ideally only a two times silicon conduction. Prototype modules have been realized with association of diodes and IGBTs in order to provide reverse-blocking devices. First results of the two-stage conversion are also presented.     

An isolated bridgeless AC-DC PFC converter using a LC resonant voltage doubler rectifier

This paper proposed an isolated bridgeless AC–DC power factor correction (PFC) converter using a LC resonant voltage doubler rectifier. The proposed converter is based on isolated conventional single-ended primary inductance converter (SEPIC) PFC converter. The conduction loss of rectification is reduced than a conventional one because the proposed converter is designed to eliminate a full-bridge rectifier at an input stage. Moreover, for zero-current switching (ZCS) operation and low voltage stresses of output diodes, the secondary of the proposed converter is designed as voltage doubler with a LC resonant tank. Additionally, an input–output electrical isolation is provided for safety standard. In conclusion, high power factor is achieved and efficiency is improved. The operational principles, steady-state analysis and design equations of the proposed converter are described in detail. Experimental results from a 60 W prototype at a constant switching frequency 100 kHz are presented to verify the performance of the proposed converter.     

Buck quasi-resonant converter operating at constant frequency:analysis, design, and experimentation

A buck pulsewidth modulated zero-current switching quasi-resonant converter (buck PWM ZCS QRC) operating at constant frequency is discussed. Operating principle and design-oriented analysis are presented with normalized design curves, design procedure, design example, simulations, and experimental results. The new topology, which can be considered as a particular one, is compared with the well-established buck frequency-modulated zero-current switching quasi-resonant converter (buck FM ZCS QRC) proposed by Fred C. Lee (1988)     

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     

ZVZCS移相全桥PWM变换器的分析与仿真研究

ZVZCS移相全桥PWM变换器实现了超前桥臂的零电压开关(ZVS)与滞后桥臂的零电流开关(ZCS),其软开关的实现条件比ZVS移相全桥与ZCS移相全桥要好。文章全面分析了这种变换器的工作原理,讨论了实现软开关的条件,设计关键参数并利用SIMetrix软件进行了仿真研究。     

An improved soft-switching PWM FB DC/DC converter for reducingconduction losses

An improved soft-switching topology of a full-bridge (FB) pulsewidth-modulated (PWM) DC/DC converter is described. The new topology employs an energy-recovery snubber to minimize a circulating current flowing through the transformer and switching devices. By using an energy-recovery snubber instead of adding a tapped inductor and a saturable reactor to reduce RMS current stress, the converter achieves zero-current switching (ZCS) for the right leg due to the minimized circulating current and achieves zero-voltage switching (ZVS) for the left leg due to the reflected output current during the interval of left leg transition. Both analysis and experiments are performed to verify the proposed topology by implementing a 7 kW (120 VDC, 58 A) 30 kHz insulated gate bipolar transistor (IGBT) based experimental circuit     

基于LPC2214的ZVZCS-PWM全桥变换控制器的研究

针对传统ZVZCS-PWMDC／DC全桥变换器在实现滞后桥臂开关管零电流开关过程中,存在着辅助谐振电路附加损耗较大,软开关实现方式复杂,功率开关管电压应力和电流应力高等缺点,介绍了一种新型次级箝位移相控制的ZVZCSPWMDC／DC全桥变换器。文中分析了该变换器实现软开关的原理,同时设计了变换器数字控制系统,控制器采用LPC2214型ARM芯片,并通过一台实验样机验证了这种软开关变换器相关理论的正确性以及该数字控制系统的可行性。     

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     

Novel zero-voltage and zero-current-switching full bridge PWMconverter using transformer auxiliary winding

A novel zero voltage and zero current switching (ZVZCS) full bridge (FB) pulse width modulation (PWM) converter is proposed to improve the demerits of the previously presented ZVZCS-FB-PWM converters, such as use of lossy components or additional active switches. A simple auxiliary circuit which includes neither lossy components nor active switches provides ZVZCS conditions to primary switches, ZVS for leading-leg switches and ZCS for lagging-leg switches. Many advantages including simple circuit topology, high efficiency, and low cost make the new converter attractive for high power (>2 kW) applications. The operation, analysis, features and design considerations are illustrated and verified on a 2.5 kW, 100 kHz insulated gate bipolar transistor (IGBT) based experimental circuit     

Interleaved ZVS Converter With Ripple-Current Cancellation

In this paper, an interleaved soft-switching converter with ripple-current cancellation is presented to achieve zero- voltage-switching (ZVS) turn-on and load current sharing. In order to achieve ZVS turn-on, an active snubber is connected in parallel with the primary winding of the transformer. The energy stored in the transformer leakage inductance and magnetizing inductance can be recovered so that the peak voltage stress of switching devices is limited. The resonance at the transition interval is used to realize ZVS turn-on of all switches. In order to achieve three-level pulsewidth-modulation (PWM) scheme, an addition fast-recovery diode is used in the converter. Three-level PWM scheme can reduce the ac ripple current on the output inductor such that the output inductor can be reduced. The current-doubler rectifier is adopted in the secondary side of the transformer to reduce the transformer secondary-winding current and output voltage ripple by canceling the current ripple of two output inductors. The output voltage is controlled at the desired value using the interleaved PWM scheme. These features make the proposed converter suitable for the dc-dc converter with high output current. The operation principles, steady state analysis, and design equations of the proposed converter are provided in detail. Finally, experiments based on a 600-W (12 V/50 A) prototype are provided to verify the effectiveness and feasibility of the proposed converter.     

一类零电流谐振开关电容变换器的特性分析

具有零电流开关特性的谐振开关电容变换器是开关电容变换器的一种新拓扑形式.本文着重分析电路寄生参数和变换器运行条件对该类谐振开关电容变换器稳态特性的影响,推出变换器输出电压和效率的数学表达式,为研究负载或输入电压变化时变换器的输出性能提供了分析和设计依据.基于输出电压表达式,还提出谐振开关电容变换器的频率控制方案.全文以一个降压式谐振开关电容变换器为例详细说明公式的推导过程,并将此稳态特性分析推广到其它类型的谐振开关电容变换器.最后,文中设计了一台12V/5V/2.5A降压式谐振开关电容变换器样机,实验结果验证了本文的理论分析结果.     

Characterization of GTOs under different modes of zero currentswitching

Several papers have described the use of GTOs in zero current switching (ZCS) applications, with the goal of increasing the frequency range for medium- and high-power converters. Zero current switching with GTOs can be applied in series and parallel resonant converters, as well as in PWM inverters with commutation aid networks. The voltage and current waveforms at the devices differ in each of these applications, and different modes of ZCS can be identified. In this paper, a comparative view of the behavior and characteristics of the GTO in the different modes of ZCS is presented. The variety of ZCS waveforms is described and transferred into a unifying schematic. The behavior of GTOs in the different modes of operation is characterized, and requirements to the circuit environment are pointed out. The relations between the most important circuit parameters and some of the device waveform parameters are investigated experimentally     

Analysis and implementation of a dual-output LLC resonant converter

This article analyses and presents an LLC resonant converter with a high power factor for LCD-TV applications. It integrates the advantages of power factor correction and the LLC resonant converter. It can improve not only power quality but also circuit efficiency. Since the power factor corrector is used in the first stage of the LLC resonant converter, it is suitable for wide input voltage range application. On the basis of the resonant behaviour, zero voltage switching is achieved for the power switches and ZCS is achieved for the rectifier diodes. An experimental prototype of 90–260V _rms input and 12V/10A and ?12V/10A outputs with 92.6% efficiency for 32″ LCD-TV application is built in the laboratory to verify the operation principle of the adopted converter.