A new ZVT-ZCT-PWM DC-DC converter

In this paper, a new active snubber cell is proposed to contrive a new family of pulse width modulated (PWM) converters. This snubber cell provides zero voltage transition (ZVT) turn on and zero current transition (ZCT) turn off together for the main switch of a converter. Also, the snubber cell is implemented by using only one quasi resonant circuit without an important increase in the cost and complexity of the converter. New ZVT-ZCT-PWM converter equipped with the proposed snubber cell provides most the desirable features of both ZVT and ZCT converters presented previously, and overcomes most the drawbacks of these converters. Subsequently, the new converter can operate with soft switching successfully at very wide line and load ranges and at considerably high frequencies. Moreover, all semiconductor devices operate under soft switching, the main devices do not have any additional voltage and current stresses, and the stresses on the auxiliary devices are at low levels. Also, the new converter has a simple structure, low cost and ease of control. In this study, a detailed steady state analysis of the new converter is presented, and this theoretical analysis is verified exactly by a prototype of a 1-kW and 100-kHz boost converter.     

A zero-voltage transition boost converter using a zero-voltage switching auxiliary circuit

A soft switching boost converter with zero-voltage transition (ZVT) main switch using zero-voltage switching (ZVS) auxiliary switches is proposed. Various operating intervals of the converter are presented and analyzed. Design considerations are discussed. A design example with experimental results obtained from a 300-W, 250-kHz, 300-V output DC-DC converter is presented. A modified gating scheme to utilize the auxiliary switch in the main power processing is discussed. A 600-W, 100-kHz, 380 V output, 90-250 V AC, power factor corrected, AC-to-DC, boost converter with the modified gating scheme is presented. Results show that the main switch maintains ZVT while auxiliary switches retain ZVS for the complete specified line and load conditions. Parasitic oscillations existing in the converters proposed in the literature are completely removed.     

Novel zero-voltage-transition PWM multiphase converters

Novel zero-voltage-transition (ZVT) pulse-width-modulation (PWM) multiphase converters are presented. To construct a ZVT multiphase converter in a conventional way, it is necessary to add the auxiliary circuits with as many number of phases. In the proposed converter, only one auxiliary circuit provides the zero-voltage switching (ZVS) for main switches and diodes of all phases. So, the new converters are cost effective and attractive for high-performance and high power-density conversion applications. Operation, features, and characteristics of the two-phase buck converter are illustrated and verified on a 4-kW 100-kHz insulated gate bipolar transistor (IGBT)-based (a MOSFET for the auxiliary switch) experimental circuit     

Self-commutated auxiliary circuit ZVT PWM converters

This paper introduces a novel class of zero voltage transition (ZVT) DC/DC pulse-width modulation (PWM) converters that use a resonant inductance-capacitance (L-C) circuit connected to the auxiliary switch, which is termed a self-commutated auxiliary circuit. It provides a simple and reliable means of achieving zero-current conditions (ZCS) for auxiliary switch commutations under wide line and load ranges, without the inclusion of any kind of DC voltage source. Furthermore, this auxiliary circuit is placed in parallel with the main power converter, retaining the ZVT characteristics. The self-commutated auxiliary circuit ZVT PWM boost is analyzed, and its feasibility and reliability are confirmed by experimental results obtained from laboratory prototypes rated at 1 kW and 100 kHz.     

一种新型软开关DC-DC PWM升压变换器设计

为提高转换效率并降低电源开关的电流应力,提出一种基于新型有源缓冲电路的PWM DC-DC升压变换器。该有源缓冲电路使用ZVT—ZCT软开关技术,分别提供了总开关ZVT开启及ZCT闭合、辅助开关ZCS开启及ZCT闭合。消除了总开关额外的电流及电压应力,消除了辅助开关电压应力,且有源缓冲电路的耦合电感降低了电流应力。另外,通过连续将二极管添加到辅助开关电路,防止来自共振电路的输入电流应力进入总开关。实验结果表明,相比传统的PWM变换器,新的DC-DC PWM升压变换器在满负荷时电流应力降低且总体效率能达到98.7%。     

A zero voltage transition boost converter employing a soft switching auxiliary circuit with reduced conduction losses

This paper presents a zero-voltage-transition (ZVT) boost converter using a soft switching auxiliary circuit for power factor correction (PFC) applications. The improvement over existing topologies lies in the positioning of the auxiliary circuit capacitors and the subsequent reduction in the resonant current and therefore the conduction losses as compared to other similar topologies. The proposed converter operates in two modes - Mode 1 and Mode 2. It is shown in the paper that the converter should be designed using the constraints obtained in Mode 1 to achieve low-loss switching. The converter is analyzed and characteristic curves presented which are then used in a detailed design example. Experimental results from a 250 W, 127 V input laboratory prototype switching at 100 kHz verify the design process and highlight the advantages of the proposed topology. The proposed converter is suitable for single-phase, two stage power factor correction circuits with universal input voltage range and power levels up to 3 kW.     

An improved ZCS-PWM commutation cell for IGBT's application

An improved zero-current-switching pulsewidth-modulation (ZCS-PWM) commutation cell is proposed, which is suitable for high-power applications using insulated gate bipolar transistors (IGBTs) as the power switches. It provides ZCS operation for active switches with low-current stress without voltage stress and PWM operating at constant frequency. The main advantage of this cell is a substantial reduction of the resonant current peak through the main switch during the commutation process. Therefore, the RMS current through it is very close to that observed in the hard-switching PWM converters. Also, small ratings auxiliary components can be used. To demonstrate the feasibility of the proposed ZCS-PWM commutation cell, it was applied to a boost converter. Operating principles, theoretical analysis, design guidelines and a design example are described and verified by experimental results obtained from a prototype operating at 40 kHz, with an input voltage rated at 155 V and 1 kW output power. The measured efficiency of the improved ZCS-PWM boost converter is presented and compared with that of hard-switching boost converter and with some ZCS-PWM boost converters presented in the literature. Finally, this paper presents the application of the proposed soft-switching technique in DC-DC nonisolated power converters     

Emulating DC constant power load: a robust sliding mode control approach

This article presents emulation of a programmable power electronic, constant power load (CPL) using a dc/dc step-up (boost) converter. The converter is controlled by a robust sliding mode controller (SMC). A novel switching surface is proposed to ensure a required power sunk by the converter. The proposed dc CPL is simple in design, has fast dynamic response and high accuracy, and offers an inexpensive alternative to study converters for cascaded dc distribution power system applications. Furthermore, the proposed CPL is sufficiently robust against the input voltage variations. A laboratory prototype of the proposed dc CPL has been developed and validated with SMC realised through OPAL-RT platform. The capability of the proposed dc CPL is confirmed via experimentations in varied scenarios.     

Zero-Voltage-Transition PWM Converters With Synchronous Rectifier

In this paper, a family of zero-voltage-transition (ZVT) pulsewidth-modulated converters with synchronous rectifier (SR) is introduced. The SR decreases the conduction losses, while it increases the achieved soft switching range. In this family of converters, zero-voltage-switching (ZVS) condition is attained for the main and rectifier switches. Also, zero-current switching is achieved for the auxiliary switch. In addition, the applied ZVS technique can eliminate the reverse recovery losses of the rectifier switch body diode. The ZVT buck converter with SR is analyzed, and the presented 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 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%     

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     

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     

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     

Novel zero-voltage-transition current-fed full-bridge PWM converterfor single-stage power factor correction

A novel zero-voltage-transition (ZVT) current-fed full-bridge pulsewidth modulation (PWM) power converter for single-stage power factor correction (PFC) is presented to improve the performance of the previously presented ZVT converter. A simple auxiliary circuit which includes only one active switch provides a zero-voltage-switching (ZVS) condition to all semiconductor devices (two active switches are required for the previous ZVT converter). This leads to reduced cost and a simplified control circuit compared to the previous ZVT converter. The ZVS is achieved for wide line and load ranges with minimum device voltage and current stresses. Operation principle, control strategy and features of the proposed power converter are presented and verified by the experimental results from a 1.5 kW 100 kHz laboratory prototype     

A Comparative Study of Zero-Current-Transition PWM Converters

Zero-current-transition pulsewidth-modulation (ZCT-PWM) boost converters are conventional boost converters that use an active auxiliary circuit to turn off the main power switch with zero-current switching; the operation and properties of these converters are the focus of this paper. In this paper, the general operating principles behind all ZCT-PWM converters are reviewed, and the operation and properties of specific converters are discussed. The strengths and weaknesses of each converter are stated, and a new and improved ZCT-PWM boost converter is proposed and discussed. Experimental results obtained from an experimental ZCT-PWM boost converter prototype implemented with several of the auxiliary circuits discussed in this paper are presented, and the results confirm the superior performance of the proposed converter     

A Three-Level Resonant Single-Stage Power Factor Correction Converter: Analysis, Design, and Implementation

This paper presents a new single-stage power factor correction ac/dc converter based on a three-level half-bridge resonant converter topology. The proposed circuit integrates the operation of the boost power factor preregulator and the three-level resonant dc/dc converter. A variable-frequency asymmetrical pulsewidth modulation controller is proposed for this converter. This control technique is based on two integrated control loops: the output voltage is regulated by controlling the switching frequency of the resonant converter, whereas the dc-bus voltage and input current are regulated by means of duty cycle control of the boost part of the converter. This provides a regulated output voltage and a nearly constant dc-bus voltage regardless of the loading condition; this, in turn, allows using smaller switches and consequently having a lower on resistance helping to reduce conduction losses. Zero-voltage switching is also achieved for a wide range of loading and input voltage. The resulting circuit, therefore, has high conversion efficiency making it suitable for high-power wide-input-voltage-range applications. The effectiveness of this method is verified on a 2.3-kW 48-V converter with input voltage (90–265 Vrms).      

A new soft-switched PWM boost converter with a lossless auxiliary circuit

A soft-switching scheme for the PWM boost converter is newly proposed to obtain the desirable features of both the conventional PWM boost and resonant converters such as ease of control, reduced switching losses and stresses, and low EMI. In order to achieve the soft-switching action, the proposed scheme employs an auxiliary circuit, which is added to the conventional boost converter and used to achieve soft-switching for both the main switch and the output diode while not incurring any additional losses due to the auxiliary circuit itself. The basic operations, in this paper, are discussed and design guidelines are presented. Through a 100?KHz, 60?W prototype, the usefulness of the proposed scheme is verified.     

Novel Family of PWM Soft-Single-Switched DC–DC Converters With Coupled Inductors

In this paper, a novel family of pulsewidth-modulation soft-single-switched dc–dc converters without high voltage and current stresses is described. These converters do not require any extra switch to achieve soft switching, which considerably simplifies the control circuit. In all converter family members, the switch is turned on under zero-current condition and is turned off at almost zero-voltage condition. From the proposed converter family, the boost topology is analyzed, and its operating modes are explained. The presented experimental results of a prototype boost converter confirm the theoretical analysis.      

ZVT Interleaved Boost Converters with Built-In Voltage Doubler and Current Auto-Balance Characteristic

An interleaved boost converter with coupled inductors and switched capacitors is proposed in this paper. The switched capacitors are used to realize the inherent voltage-double function that increases the voltage gain and reduces the voltage stress of the switch greatly. Therefore, the low-conduction resistance and low-voltage-rated switches can be applied to improve the efficiency of this topology. Moreover, the load current can automatically be equally shared by each phase as a consequence of the switched capacitors adopted in the output stage. Active clamp circuits are applied for the interleaved two phases to recycle the leakage energy and absorb the voltage spikes caused by the leakage inductance. Both the main and the clamping switches are zero-voltage transition (ZVT) switches during the whole switching transition that reduce the switching losses. The current falling rates of the clamping diodes and output diodes are controlled by the leakage inductance so that the diode reverse-recovery problem is alleviated. The experimental results are shown to verify the effectiveness of the theoretical analysis based on a 48- to- 380-V dc/dc prototype.