Soft-switching DC-DC Research Articles

A Family of Magnetic Coupling DC-DC Converters With Zero-Voltage-Switching Over Wide Input Voltage Range and Load Variation

This paper presents a family of soft-switching DC-DC converters with a simple auxiliary circuit consisting of a coupled winding and a pair of auxiliary switch and diode. The auxiliary circuit is activated in a short interval and thus the circulating conduction losses are small. With the auxiliary circuit, zero-voltage-switching (ZVS) and zero-current-switching are achieved for the main and auxiliary switches respectively, over wide input voltage range and load variation. In addition, the reverse-recovery problem of diodes is significantly alleviated because of the leakage inductor. Furthermore, the coupled inductor simultaneously serves as the main and auxiliary inductors, contributing to reduced magnetic component in comparison with the conventional zero-voltage-transition (ZVT) converters. Experimental results based on a 500 W prototype buck circuit validate the advantages and effectiveness of the proposed magnetic coupling ZVS converter.

ZVZCS PWM DC-DC Converter with Controlled Secondary Rectifier for ARC Welding

A zero-voltage, zero-current switching (ZVZCS) PWM DC-DC power converter with secondary active rectifier tested as a dc current source for arc welding is described in this paper. The soft switching DC-DC converter consists of high frequency inverter, high frequency power transformer and controlled output rectifier with new secondary energy recovery turn-off snubber. Circulating current in the converter is reduced by using active rectifier and rms value of the current in secondary switches is decreased by utilizing a novel control algorithm. The experimental results of a 4.5 kW DC-DC converter working at switching frequency of 100 kHz are presented.

A State Space Modeling of Non-Isolated Bidirectional DC-DC Converter with Active Switch

In this paper, analysis, design and implementation of non-isolated soft-switching bidirectional DC-DC converter with an active switch are described. The proposed topology gives the output voltage as twice as the input voltage and enhances the efficiency up to 94.5% and 92.9% for boost and buck mode operation by proper selection of the duty cycle. Soft switching can be achieved at both steps up and step down operating modes. Small signal analysis based on state space averaging and transfer functions have been presented in detail for the proposed converter. Finally, the feasibility of the desired converter is confirmed to mat lab simulation and investigational results.

넓은 범위 입력전압에 소프트 스위칭이 가능한 양방향 인터리브드 DC-DC 컨버터

This study deals with a bidirectional interleaved soft switching DC-DC converter for a wide range of input voltages. The proposed converter operates in complementary switching with the purpose of inductor size reduction and zero-voltage switching (ZVS) operation. The current ripple related to complementary switching is minimized by three-phase interleaved operation. The main characteristics of the proposed topology are its soft-switching method of operation and its simple structure. The soft-switching operation and the system efficiency of the proposed converter are verified by experimental results.

A control method to improve the efficiency of a soft-switching non-isolated bidirectional DC-DC converter for hybrid and plug-in electric vehicle applications

Hybrid energy storage system (HESS) can be adopted in hybrid, plug-in hybrid, and pure electric vehicles (HEV, PHEV, and EV), where a bidirectional DC-DC converter (BDC) is used to connect batteries and ultracapacitors. The efficiency improvement of the BDC is beneficial to increase the efficiency viability of HESS. Due to ZVS, high efficiency can be obtained at heavy load operations while the efficiency is low at light load operations mainly because of the conduction losses of the auxiliary circuits. These losses can be reduced by optimising the switching frequency. The relationship of efficiency and switching frequency are presented and discussed. A scaleddown 1 kW BDC prototype is built to verify the feasibility of the efficiency improvement. With the aim of achieving ZVS conditions and variable frequency control, the implementing method is proposed. The simulated results are also presented, which can validate the feasibility of the proposed control method.

A High-Frequency-Link Secondary-Side Phase-Shifted ZVS-PWM DC-DC Converter with ZCS Active Rectifier

Performance evaluations of a secondary-side phase shift (SPS) pulse-width-modulation (PWM)-controlled zero voltage soft-switching (ZVS) DC-DC converter with a zero current soft-switching (ZCS) active rectifier are presented in this paper. In the proposed DC-DC converter, the soft-switching operations are achievable from full to null loads by utilizing the parasitic inductances of the high-frequency (HF) transformer. In addition, no circulating current emerges in either the primary- or secondary-side full-bridge circuits, and thus the related idling power losses can be minimized. In this paper, the soft-switching operations over the wide-range load variations are verified, and the characteristics of output power and voltage versus phase shift angle regulations are demonstrated in an experiment based on a 1kW-50kHz laboratory prototype of the proposed DC-DC converter. Furthermore, the converter power losses, which include the switching and conduction power losses, are analyzed, after which the effectiveness of the proposed DC-DC converter is evaluated from a practical point of view.

AC 모듈형 태양광 모듈 집적형 컨버터를 위한 소프트 스위칭 DC-DC 컨버터

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

Research on LLC DC-DC Transformer

Regulated DC-DC converter and unregulated DC-DC transformer is the basic types of DC-DC converter. Now the research is focusing on the regulated form named regulated LLC resonant DC-DC converter. Unregulated form of LLC resonant DC-DC converter named LLC resonant DC-DC transformer is studied in this paper in order to increase the practical topology of soft-switching and high-efficiency DC-DC transformer. Design method is proposed by the gain curve analyze of LLC resonant DC-DC transformer, and load characteristic of gain and efficiency of the DC-DC transformer is analyzed specializing for optimal design. A LLC resonant DC-DC transformer prototype is designed and implemented. Experimental results verify the correctness and validity of the design method and the load characteristic analysis.

Soft-Switched DC-DC Converter with Current and Voltage Doubler

This paper proposes a method that consists of a phase-shift converter with a current doubler rectifier on the output side. The phase-shift converter operates at a frequency as high as 20-25 kHz (depending on the requirement of the application) to improve the power density of the converter using unity turns ratio in the isolation transformer. The size of the circuit is smaller for the same power rating. Ferrite core transformer is used instead of the conventional one, which is bulky and leads to a very large core loss. Unlike the conventional method, the number of turns of the transformer is reduced and the overall power density is increased. The current doubler rectifier doubles the input current as needed for a few vital applications. The circuit for the phase-shift converter with the current doubler was simulated using PSPICE software. For an input current of 4 A, an output of 10.2 A was obtained, which eventually settled at nearly 8.5 A. A hardware model of the proposed method validates the simulation results.

Soft-switched DC-DC converter with current and voltage doubler

This paper proposes a method that consists of a phase-shift converter with a current doubler rectifier on the output side. The phase-shift converter operates at a frequency as high as 20-25 kHz (depending on the requirement of the application) to improve the power density of the converter using unity turns ratio in the isolation transformer. The size of the circuit is smaller for the same power rating. Ferrite core transformer is used instead of the conventional one, which is bulky and leads to a very large core loss. Unlike the conventional method, the number of turns of the transformer is reduced and the overall power density is increased. The current doubler rectifier doubles the input current as needed for a few vital applications. The circuit for the phase-shift converter with the current doubler was simulated using PSPICE software. For an input current of 4 A, an output of 10.2 A was obtained, which eventually settled at nearly 8.5 A. A hardware model of the proposed method validates the simulation results.

Zero-current switching resonant buck converters with small inductors

In this study two new zero-current switching resonant buck converters as soft-switching DC-DC converters are presented. In the first topology, small inductors are implemented and thus it is appropriate for integrated circuits. In the second topology, an alternative structure is presented in which not only a switch is eliminated but also higher power can be delivered. Both converters enjoy a very simple control method. The converters are analysed in details and theoretical equations are presented. The presented experimental results from the implemented prototypes confirm the theoretical analyses.

Simulation and Implementation of Soft-Switched Interleaved DC-DC Boost Converter for Fuel Cell Systems

In this paper, a soft-switched Interleaved DC-DC Boost Converter (IBC) for fuel cell is simulated and implemented. The proposed two-phase IBC circuit consists of two identical boost converter connected in parallel and are controlled by interleaved switching signals. But in the conventional IBC switching loss increases with the number of switching devices. To solve this problem, this paper has proposed a soft switched IBC. Detailed analysis has been done to investigate the benefits of soft-switched IBC compared to that of conventional uncoupled and directly coupled IBC. The converter circuit is constructed using power MOSFET as power switch. The PWM is generated by PIC18F4450 microcontroller. In this paper, the analysis of the converter is presented which is verified by the results of simulation and experimentation.

Simulation and Implementation of Soft-Switched Interleaved DC-DC Boost Converter for Fuel Cell Systems

In this paper, a soft-switched Interleaved DC-DC Boost Converter (IBC) for fuel cell is simulated and implemented. The proposed two-phase IBC circuit consists of two identical boost converter connected in parallel and are controlled by interleaved switching signals. But in the conventional IBC switching loss increases with the number of switching devices. To solve this problem, this paper has proposed a soft switched IBC. Detailed analysis has been done to investigate the benefits of soft-switched IBC compared to that of conventional uncoupled and directly coupled IBC. The converter circuit is constructed using power MOSFET as power switch. The PWM is generated by PIC18F4450 microcontroller. In this paper, the analysis of the converter is presented which is verified by the results of simulation and experimentation.

High-Efficiency Power Conditioning System for Grid-Connected Photovoltaic Modules

This paper presents a high-efficiency power conditioning system (PCS) for grid-connected photovoltaic (PV) modules. The proposed PCS consists of a step-up DC-DC converter and a single-phase DC-AC inverter for the grid-connected PV modules. A soft-switching step-up DC-DC converter is proposed to generate a high DC-link voltage from the low PV module voltage with a high-efficiency. A DC-link voltage controller is presented for constant DC-link voltage regulation. A half-bridge inverter is used for the single-phase DC-AC inverter for grid connection. A grid current controller is suggested to supply PV electrical power to the power grid with a unity power factor. Experimental results are obtained from a 180 W grid-connected PV module system using the proposed PCS. The proposed PCS achieves a high power efficiency of 93.0 % with an unity power factor for a 60 Hz / 120 Vrms AC power grid.

Optimal Design of a DC-DC Converter for Photovoltaic Generation

This paper presents novel circuit topology of half-bridge soft-switching PWM inverter type DC-DC high power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed, half-bridge high frequency PWM inverter with a high frequency planar transformer link PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode-equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC bus lines can achieve ZCS turn-on and ZVS turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, high switching frequency IGBTs can actually be selected in the frequency range of 40[㎑] under the principle of soft-switching. The performance evaluations of the experimental setup are illustrated practically.

Isolated Topologies of Switched-Resonator Converters

Switched-resonator converters are a new family of soft switching DC-DC converters where the energy is transferred via a resonator. This paper introduces some isolated topologies of this family. The achieved advantages include, load independent soft-switching, self short-circuit protection, and optimization capability due to topology variety. Compared to conventional seriesresonant converters, outstanding advantages such as a smaller fewer number of switches and diodes, a smaller transformer, and lower current stresses are achieved. A general synthesis scheme, functional topologies, and essential relations are included. Experimental results from a laboratory prototype confirm the presented theoretical analysis.

New high-frequency linked half-bridge soft-switching PWM DC–DC converter with input DC rail side active edge resonant snubbers

This study presents a new circuit topology of the active edge resonant snubber-assisted half-bridge soft-switching PWM inverter-type DC-DC high-power converter for DC bus feeding power plants. The proposed DC-DC power converter is composed of a typical voltage source-fed half-bridge high-frequency PWM inverter with a high-frequency planar transformer link in addition to input DC busline side power semi-conductor switching devices for the PWM control scheme and parallel capacitive lossless snubbers. The operating principle of the new DC-DC converter treated here is described by using switching mode equivalent circuits, together with its unique features. All the active power switches in the half-bridge arms and input DC buslines can achieve zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off commutation transitions. The total turn-off switching losses of the power switches can be significantly reduced. As a result, a high-switching-frequency isolated gate bipolar transistor (IGBT) can be actually selected in the frequency range of 60-kHz under the principle of soft switching. The performance evaluations of the experimental setup are illustrated practically. The effectiveness of the new converter topology is proved for low-voltage and large-current DC-DC power supplies as DC bus feeding from a practical point of view.

Practical Evaluations of a Novel Asymmetrical ZCS-PWM DC-DC Converter with High-Frequency Transformer-Link

This paper presents a novel Zero Current Switching (ZCS)-PWM controlled half-bridge DC-DC converter with High-Frequency (HF)-link. The newly-proposed soft switching DC-DC converter consists of a multi-resonant half-bridge HF-isolated inverter controlled by an asymmetrical PWM scheme and a center-tapped diode rectifier with a choke input filter. In order to attain the wide range of soft-commutation under the condition of constant switching frequency, the single Active Edge-Resonant Cell (AERC) that is composed of a lossless inductor and a switched resonant capacitor is originally employed for the half-bridge inverter arm, providing and assisting ZCS operations in the switching power devices. The ZCS-PWMDC-DC converter treated here is evaluated in experiments using the 800 W-55 kHz prototype. The practical effectiveness of the proposed soft switching DC-DC converter is actually demonstrated and discussed with the experimental results under open loop and closed loop configurations. Finally, the feasibility of the DC-DC converter topology is discussed from the view points of the high efficiency and high power density.

Power converters and amplifiers (review of "Pulse-Width Modulated DC-DC Power Converters" by Kazimierczuk, M.K.; 2008) [Book News

This book is a comprehensive textbook in the areas of electrical, electronics, and telecommunications engineering. It consists of 17 chapters and two appendices. Some of the topics covered include: buck PWM DC-DC converters; boost PWM DC-DC converters; buck-boost-PWM DC-DC converters; half-bridge and full-bridge converters; push-pull PWM DC-DC converters; open-loop small-signal characteristics of boost converters for CCM; current-mode control of boost converters; silicon and silicon carbide power diodes; and soft-switching DC-DC converters. Appendix A is an introduction to SPICE and Appendix B provides an introduction to MATLAB. Answers to problems and the index are also included at the end of the book. The book is recommended for senior undergraduate and graduate students but also for practicing engineers working with switch-mode power supplies, within applications such as computers, telecommunications, industrial electronic systems, automobile electronics, medical equipment, radars, and aerospace power technology.

Bi-directional Zero-current Soft-switching Technique Applied for Bi-directional DC-DC Converter in Energy Capacitor Systems

In our previous work, we proposed the current-source energy capacitor system (CS-ECS), which consists of an electric double-layer capacitor, current-source inverter, and bi-directional four-quadrant DC-DC (FQ DC-DC) converter to control active/reactive power that can achieve the output leveling of wind energy system. However, this system had low conversion efficiency due to hard-switching losses. The improvement of conversion efficiency and performance are indispensable to implement the CS-ECS. This article proposes the soft-switched FQ DC-DC converter with a simple L-C resonant circuit for the CS-ECS. Since the insulated gate bipolar transistors of the converter softly turns on and off by using current-mode resonance, the conversion efficiency for the proposed system improves. In order to illustrate the operating principle of the proposed system, we analyze the transition of conversion efficiency with charge and discharge operation in detail through a theoretical approach and computer simulations with MATLAB/SIMULINK and SimPowerSystems Toolbox.