Zero-voltage Zero-current Switching Research Articles

A Low-Cost and High-Efficiency Active Cell-Balancing Circuit for the Reuse of EV Batteries

In this paper, a high-efficiency and low-cost active cell-to-cell balancing circuit for the reuse of electric vehicle (EV) batteries is proposed. In the proposed method, a battery string is divided into two legs to transfer the charge from each cell in one leg to that in the other and a bidirectional CLLC resonant converter is used to transfer energy between the selected cells. Thanks to the proposed structure, the number of bidirectional switches and gate drivers can be reduced by half compared to the conventional direct cell-to-cell topologies, thereby achieving lower cost for the system. The CLLC converter is used to transfer the charge, and it is designed to work at resonant frequencies to achieve zero-voltage zero-current switching (ZVZCS) for all the switches and diodes. Consequently, the system’s efficiency can be enhanced, and hence, the fuel economy of the system can also be improved significantly. To verify the performance of the proposed active cell-balancing system, a prototype is implemented for balancing the three EV battery modules that contain twelve lithium-ion batteries from xEV. The maximum efficiency achieved for the charge transfer is 89.4%, and the balancing efficiency is 96.3%.

A New Zero-Voltage Zero-Current Switching Converter with Minimum Duty Cycle Loss

Zero-voltage zero-current switching (ZVZCS) phase-shifted full-bridge (PSFB) converters have been widely used in high-power applications because of their high efficiency, low price, and easy control. Currently, the biggest problem with PSFB converters in operation is their high duty cycle loss. With the increase in current, duty cycle loss grows and degrades their performance. Focusing on this problem, a new ZVZCS PSFB converter is proposed in this paper. This topology adds an auxiliary circuit to minimize duty cycle loss. Moreover, the lagging-leg switches can obtain zero-current switching (ZCS) easily with the help of the circuit. The auxiliary circuit is built of four metal-oxide-semiconductor field-effect transistors (MOSFETs) and an auxiliary transformer, and extra voltage can be added to the primary coils when the direct-current (DC) voltage is small. This paper discusses its operation principles and characteristics, and an experiment of a 2 kW prototype was conducted, the results of which demonstrate the advantages of the presented circuits.

High Power ZVZCS Phase Shift Full Bridge DC–DC Converter With High Current Reset Ability and No Extra Electrical Stress

Zero-voltage zero-current switching (ZVZCS) phase-shift full-bridge (PSFB) dc–dc converters are candidate converters for high-power switching mode power supply because of their low cost and high efficiency. However, these converters still have some definite weaknesses, e.g., resetting obstacles of high-value currents, extra electrical stress on the power devices. Hence, customers seldom adopt these topologies in high-power applications. This article proposes a new ZVZCS PSFB dc–dc converter to solve the above problems. A clamping circuit with two <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s, two diodes, and a resetting transformer ensures ZCS of the lagging-leg switches over a wide load range, and no extra electrical stress arises on the primary or secondary components. The clamping circuit has a high current reset ability and can break through the power limitation of conventional ZVZCS PSFB dc–dc converters. The volume of the resetting transformer is small because of the low voltage-second product, and the added <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> s cause low power loss because of the wide soft-switching load range and low on-resistance. The experimental results from a 12-kW prototype prove the rightness and advantages of the proposed converter.

Analysis, Design, and Experimental Results for a High-Frequency ZVZCS Galvanically Isolated PSFB DC-DC Converter over a Wide Operating Range Using GaN-HEMT

This paper investigates the potential of the emerging gallium nitride (GaN) high-electron mobility transistors (HEMT) power devices to meet certain power conversion challenges. The advantages of utilizing GaN HEMT transistors in a high-frequency, high-power isolated DC-DC topology are explored experimentally. Using the GaN HEMT’s parasitic elements, e.g., output capacitance, and the leakage inductance of the transformer, a soft switching zero-voltage zero-current switching (ZVZCS) phase shift converter is proposed. Accordingly, the freewheeling current is terminated, and soft switching is realized for most of the primary and secondary active devices. Furthermore, without using any additional circuitry, the overshoot voltage across the bridges of active rectifier diodes is clamped at their voltage level. In addition, a high-frequency power transformer is optimized to minimize the overall transformer losses (e.g., winding and core losses). Combined the conductor types, e.g., litz wire and copper foil, shows good electrical and thermal performance by reducing the AC and DC resistance. Finally, a 5 kW, 100–250 kHz prototype is built and tested. The experimental results show a conversion efficiency of up to 98.18% for the whole converter.

Analysis and implementation of an isolated high step‐down converter with interleaved output for low voltage applications

AbstractThis paper proposes a new isolated high step‐down dc‐dc converter with a more extensive output range and high efficiency. The interleaved output and ZVS‐ZCS switching for all semiconductors have made the converter appropriate for high output current applications. An auxiliary inductor is used to achieve the ZVS (zero‐voltage switching) and ZVZCS (zero‐voltage zero‐current switching) condition, which charges and discharges the parallel snubber capacitors of the power switches at different modes of operation. Therefore, the switching losses of semiconductor components are reduced significantly, which results in enhanced efficiency. Moreover, the connection of an auxiliary capacitor in series with the transformer has prevented the probability of DC‐current saturation. The proposed converter could be controlled with duty‐cycle or switching frequency variations. However, the output voltage control with the switching frequency variations gives an extended range of output voltage compared with the other presented converters. Moreover, a coupled inductor is used to relate the output gain with the turn ratios, which causes a more extensive range for output voltage gain. Finally, the theoretical analysis is given and is compared with a 140 W experimental prototype, which converts a higher input voltage 300v to 7.5 V of the output voltage.

A Hybrid Three-Level ZVZCS Converter for Photovoltaic Power Connecting to MVDC Collection System

Compared with the medium voltage ac (MVAC) collection system, the medium voltage dc (MVDC) one for renewable energy sources has many advantages. High-power dc/dc converters are one of the key stages of the MVDC collection system to boost the voltage generated by photovoltaic or wind turbine. A novel hybrid three-level dc/dc converter utilizing a blocking capacitor to realize zero-voltage zero-current-switching (ZVZCS) is proposed. A higher overall efficiency can be achieved by reducing conduction losses. Detailed experimental results on a scaled-down hardware prototype rated at 150 V/750 V/1 kW are demonstrated to verify the proposed converter performance.

Investigation of a Novel Interleaved Buck Converter for Renewable Energy Applications: Design and Analysis

In this paper, a new interleaved buck converter with soft-switching is investigated. The soft-switching condition, zero voltage zero current switching (ZVZCS) of IGBTs during turn-on is obtained with the help of a soft-switching cell that includes active and passive devices that is incorporated in the interleaved buck converter (IBC). The presence of the soft-switching cell reduces the switching losses and improves the overall efficiency. The IGBTs in the converter achieved ZVZCS turn on operations, while converter is operated under both light and heavy loads. The principles of operation and theoretical aspects of the proposed converter system 400 V / 110 V / 2.5 kW are verified with simulation analysis.

A new zero voltage transition interleaved flyback converter

The paper introduced a new zero voltage transition (ZVT) interleaved flyback converter which has two similar flyback converters. Two flyback converters are in parallel connection and auxiliary circuit in this converter provides ZVT condition for all of the main switches and also provides zero current switching and zero voltage zero current switching (ZVZCS) conditions for the auxiliary switch. Also, ZCS conditions are created for diodes turning off, so reverse recovery problem is solved. The auxiliary circuit in the suggested converter is modular, and by adding parallel branches to the flyback circuit, this circuit can provide soft switching conditions for all switches without significantly change. A complete analysis of the converter is provided and its operating intervals are explained. A 180 W laboratory prototype of the converter is made to approve the theoretical calculations. The experimental results show 7.7% increase in efficiency.

A Comparative Analysis of Soft Switching Techniques in Reducing the Energy Loss and Improving the Soft Switching Range in Power Converters

This paper presents a comparative analysis of the zero-voltage zero-current switching (ZVZCS) soft switching technique with zero-voltage switching (ZVS) and zero-current switching (ZCS) counterparts. The generalization of the voltage–current crossover or the energy loss factor obtained from simulation of the prototype converter shows that the ZVZCS significantly reduces the losses and helps to improve the efficiency of the converter as compared to the ZVS or the ZCS. On the other hand, it is also found that the soft switching range of operation of the ZVS and the ZCS is largely affected by the maximum switch voltage and switch current, respectively. In contrast, these factors have a negligible effect on the ZVZCS operation which results in an extended range of soft switching operation. Additionally, a detailed PSPICE simulation is performed for selected ZVS, ZCS, and ZVZCS topologies from the recent literature, and the switching losses in the main switches of the converters are measured. It is observed that the energy losses in the ZVZCS mode are reduced on average by approximately 26% at turn on and 20% at turn off as compared to the ZVS and the ZCS. Furthermore, the low standard deviation in this mode confirms a stable low-loss profile which renders an extended soft switching range. An experimental test is also conducted by building the prototype converter to verify the simulation results. It is found that the switching losses are minimum while the converter is operated in the ZVZCS mode. Additionally, the efficiency drop remains consistently low as compared to the ZVS and the ZCS in the whole operating range. Accordingly, the simulation and the experimental results are both found to be consistent.

An Investigation of Class E VSI based DC-DC Converter for Wireless Charging Application

A class E voltage source inverter (VSI) based DC-DC step down converter is used for Inductive Power Transfer (IPT) which is generally used for the application of wireless power transfer (WPT). It has less number of switches, and can be turned ON with zero voltage zero current switching (ZVZCS), and turned OFF with zero voltage switching (ZVS). Significant progress has been achieved in the field of IPT, there are many obstacles and design challenges are still present. Low power transfer efficiencies and short power transfer range. Higher efficiencies are possible for very short transmission distances. Large amounts of power can be transferred for large distances but at reduced efficiencies. This paper addresses the limitations of IPT systems. A complete study and analysis of the converter have been given, FEM simulation tool has been used to study the shape or structure of coil has been presented. The change in coupling coefficient of two magnetically coupled coils is evaluated at different air gap and misaligned positions. The outcome of this work results in the selection of suitable shape of coil and efficient converter for wireless power transfer.

A new soft‐switching multi‐input quasi‐Z‐source converter for hybrid sources systems

This study focuses on a zero voltage transition multi-input quasi-Z-source converter (qZSC). This topology can be used for input sources with different voltages and currents to provide a constant output voltage. In the proposed structure, several qZSCs are combined and the output filter of all stages is eliminated. Therefore, the overall number of circuit elements, cost, volume and weight are reduced in comparison with when they are in a separate operation. In this converter, the soft-switching conditions are provided for all stages by using only one auxiliary circuit. The employed technique provides zero-voltage zero-current switching (ZVZCS) and zero-voltage switching for main switches at turn-on and turn-off instants, respectively. The auxiliary switch turns on under zero-current switching and turns off under ZVZCS. Furthermore, the reverse recovery losses of diodes are reduced. The theoretical foundation of the proposed converter is presented and its performance is simulated by OrCAD software. The obtained results show 3.5% improvement in the efficiency at nominal loads, compared to its hard-switching counterpart. A dual-input prototype of the proposed structure is successfully built to support the validity of the theoretical analysis.

An Interleaved Zero-Voltage Zero-Current Switching High Step-Up DC-DC Converter

An interleaved zero-voltage zero-current switching (ZVZCS) high step-up DC-DC converter is proposed for modern photovoltaic power generation systems. The proposed converter can achieve high voltage conversion gain without operating under extreme duty cycles. The voltage conversion gain can be readily adjusted by selecting different numbers of the diode-capacitor multiplier (DCM) cells in the circuit at the design stage. Moreover, with the passive snubber circuit in the proposed converter, all power switches and diodes in the DCMs can achieve zero-voltage turn-off and zero-current turn-on, which effectively reduces switching losses and increases the overall converter efficiency. The operational principles and analysis of the performance analysis with two DCMs are presented for demonstrative purpose. The effectiveness of the proposed ZVZCS DC-DC converter is validated using an 800W experimental prototype.

An Efficient Inductive Power Transfer Topology for Electric Vehicle Battery Charging

Recently available high-frequency power converter topologies for inductive power transfer (IPT) system utilize either zero voltage switching (ZVS) or zero current switching (ZCS) based power electronic converters while maintaining a near sinusoidal current for limited power transfer range. However, achieving ZVS or ZCS for all power switches simultaneously is still a challenging task in IPT systems. In this article, an improved zero-voltage zero-current switching (ZVZCS) IPT topology and its switching pattern are proposed. ZVS is achieved by optimizing the classical series compensation and additionally, an auxiliary network is employed to achieve ZCS. The proposed concept is verified by using MATLAB/Simulink based simulations for resistive and battery load. Finally, the practical viability of the proposed topology is validated by the results obtained using a laboratory prototype rated for 1.1 kW, 85 kHz. An efficiency of 91.26% is achieved with ZVZCS for a full dynamic power transfer range of 20 W–1.1 kW.

Isolated Single-ended Primary-inductive Converter with a Soft-switching Cell for Implementing Features of Zero-voltage Switching and Zero-current Switching

Isolated Single-ended Primary-inductive Converter with a Soft-switching Cell for Implementing Features of Zero-voltage Switching and Zero-current Switching

Soft-Switching High Step-Up/Down Converter Using Coupled Inductors With Minimum Number of Components

This article presents a soft-switching buck-boost converter with high step-up/down conversion ratio. The popular coupled inductors method is employed to achieve high step-up/down gain conversion. Moreover, a simple auxiliary circuit, including a small capacitor, active switch, and an extra winding on the coupled inductors, is utilized to provide soft-switching condition for the main switches in both operating states. This simple auxiliary circuit is a proper substitute for two essential active clamp circuits required in bidirectional converters with coupled inductors. Also, the added auxiliary winding is employed in the power flow path to increase the step-up/down voltage gain. All switches have zero current switching (ZCS) turn-on and zero voltage ZCS (ZVZCS) turn-off performance, which eliminates the reverse recovery problem of switches body diodes and improves converter efficiency. A 300-W prototype converter with 48-380 V conversion ratio is realized to confirm the validity of theoretical analysis and the operation of the proposed converter.

Dual‐active‐bridge DC–DC converter with auxiliary parallel networks for wide load range ZVZCS application

In this study, a wide load range zero-voltage zero-current switching (ZVZCS) dual-active-bridge DC–DC converter using auxiliary parallel networks is proposed. The outstanding feature of the proposed converter is that all of the switches are allowed to operate with zero-voltage switching while four of the switches are allowed to operate with zero-current switching, due to the use of two auxiliary parallel networks, which were paralleled to two active bridges, respectively. Furthermore, the circulating current losses can be reduced significantly by using unified boundary trapezoidal modulation method. Based on these merits, the proposed converter has some advantages for the wide range load variation applications with less circulating current losses. The operation principles, soft-switching conditions and loss analyses comparison are given in this study. These benefits and characteristics mentioned above are verified from the experimental results by using a 1 kW prototype.

Zero-voltage Zero-current Switching Scheme for Charge-pump Based Dual Boost Converter

Zero-voltage Zero-current Switching Scheme for Charge-pump Based Dual Boost Converter

High-efficiency active cell-to-cell balancing circuit for Lithium-Ion battery modules using LLC resonant converter

A high-efficiency active cell-to-cell balancing circuit for Lithium-Ion battery modules is proposed in this paper. By transferring the charge directly from the highest voltage cell to the lowest voltage cell using an LLC resonant converter designed to achieve zero-voltage switching (ZVS) and nearly zero-current switching (ZCS) for all of the primary switches and zero-voltage zero-current switching (ZVZCS) for the diodes in the secondary, the proposed topology can achieve a high efficiency and a fast balancing speed with a simple control and design. In order to show the improved performance of the proposed method, a prototype circuit was built with a battery module having twelve Lithium-Ion (Li-Ion) batteries. Experimental results are presented to verify the shorter balancing time and higher efficiency of the proposed method when compared with conventional methods. The measured time for the balancing of the twelve cells was 47 min and a maximum efficiency of 94.5% was achieved at 1.5 W.

A New Simple-Structure Passive Lossless Snubber for DC–DC Boost Converters

A new soft-switching boost converter with simple-structure passive lossless snubber is proposed in this article. It shows various advantages as low cost, few auxiliary elements, and low-voltage stress on the switch. The passive snubber circuit consists of an inductor, two capacitors, and two diodes. It provides zero current switching (ZCS) turn-on and zero voltage switching (ZVS) turn-off for the switch. The main diode turns on under ZVS and turns off under zero-voltage ZCS, therefore, reverse recovery problem is solved. Also, total efficiency and conducted electromagnetic interference of the proposed converter compared to the conventional boost converters are improved. To prove it, 220 W prototypes are implemented. The experimental results along with the theoretical analysis confirm an increase of 3% in efficiency of the proposed converter.

Comparative Evaluation of Wide-Range Soft-Switching PWM Full-Bridge Modular Multilevel DC–DC Converters

This paper discusses some wide-range soft-switching full-bridge (FB) modular multilevel dc–dc converters (MMDCs), and a comparative evaluation of these FB MMDCs is also presented. The discussed topologies have all merits belonging to conventional FB MMDCs, e.g., smaller voltage stress on the primary switches, no added primary clamping devices and modular primary structure. In addition, the primary switches in each converter can obtain zero-voltage switching (ZVS) or zero-current switching (ZCS) in a wide load range. Two presented topologies are selected as examples to discuss in detail. The proposed FB MMDCs are assessed and evaluated based on performance, components and topology structure indices, such as soft switching characteristics, current stress, power loss distribution, number of added devices, complexity of structure and added cost. Experimental results are also included to verify the feasibility and advantages of the new topologies.