Zero-voltage Switching Condition Research Articles

Steady-State Analysis and Modified Control Technique of a Capacitor Voltage Clamped Dual Half-Bridge Series Resonant Inverter

The paper discusses the technical problems, which are related to the application of the inverter configurations for electrotechnological purpose with power-limiting property. The examined capacitor voltage clamped dual half-bridge series-resonant inverter (CVCDHB-SRI) is a part of the class of inverters with improved load characteristics, which are characterized by stability in the operation of the power circuit, the power consumption is constant and independent from changes in the load. The present paper extends the investigation of the electromagnetic processes in steady-state mode of CVCDHB-SRI that supplies two different loads. A unified approach is introduced in the analysis of processes in steady-state mode, as well as, expressions for determination of the currents through the power devices and the resonant circuit components are obtained. A modified control technique for operating loads with different frequency and power is also discussed. Thus, the additional current overload of some of the transistors in the circuit is avoided. The commutation mechanism of the transistors enables zero-voltage and zero-current switching conditions. This results in increases the efficiency of the system and improves power quality and reduces the overall cost. The results of the analysis are confirmed by simulating with OrCad Pspice.

A New PWM and Commutation Scheme for One Phase Loss Operation of Three-Phase Isolated Buck Matrix-Type Rectifier

In this paper, a new pulse width modulation (PWM) scheme and commutation method is presented for one phase loss operation of three-phase isolated buck matrix-type rectifier. With the proposed PWM scheme, the maximum allowable voltage gain for one phase loss operation can be achieved, which permits the continuous operation of the converter to deliver two-third of the rated power and regulate the output voltage with maximum output voltage drop less than 5% of nominal output voltage. In addition, with the proposed commutation method, a safe transition from one phase loss operation to normal operation and vice versa can occur with minimum commutation steps (two-step) under zero-voltage switching condition. The performance of the proposed PWM scheme and commutation schemes with one phase loss operation is evaluated and verified by simulations and experiments on a 5 kW prototype.

A ZVS Bidirectional Inverting Buck-Boost Converter Using Coupled Inductors

The bidirectional inverting buck-boost converter (BIBBC) has a simple structure and a wide voltage ratio. It can be used in the battery supercapacitor hybrid energy storage system (BSHESS) and the motor drive system. However, the traditional continuous conduction mode (CCM) BIBBC will have severe switching loss. The triangular current mode (TCM) BIBBC can reduce the switching loss, but it will increase core loss and filter capacitance. To solve these problems, this paper proposes a new zero voltage switching (ZVS) BIBBC using a coupled inductor. This ZVS BIBBC will provide ZVS conditions for both transistors whether in positive operation or negative operation. Meanwhile, this ZVS BIBBC has small core losses and filter capacitance, and can be used simply. Finally, experimental results obtained from these BIBBC experimental prototypes are presented to validate the soft-switching achieving and the efficiency improvement performance. Experimental results show that both transistors of the ZVS BIBBC achieve ZVS turn-on conditions. The efficiency of the ZVS BIBBC increased by up to 10 percent compared to the traditional CCM BIBBC at heave load, and by up to 1.5 percent compared to the TCM BIBBC at a light load.

Soft Switching of Three-Phase AC to DC CIHRC with Wireless Power Transfer (WPT) Function

<span lang="EN-US">This paper presents the verification of soft switching condition for three-phase AC to DC current injection hybrid resonant converter (CIHRC) with wireless power transfer (WPT) function. Details on the operation of current injection technique with the lossless zero voltage switching (ZVS) condition on shaping the high power factor of supply current waveforms are presented. With a suitable high switching frequency operation, the proposed resonant converter is capable to operate with ZVS conditions, thus, allowing reduction in the size of inductive and magnetic components. Selected results are also presented to verify the lossless ZVS condition for three-phase AC-DC CIHRC with WPT function.</span>

A New Interleaved Coupled-Inductor Nonisolated Soft-Switching Bidirectional DC–DC Converter With High Voltage Gain Ratio

This paper presents a new interleaved coupled-inductor nonisolated bidirectional dc–dc converter that provides high voltage gain ratio (VGR), low ripple current at the low-voltage side (LVS), and soft switching. The high VGR is obtained by connecting in series the outputs of an interleaved bidirectional buck–boost converter and a dual-active half-bridge converter, using the turns ratio of a coupled inductor. Since the voltage of the high-voltage side is shared between the converters outputs, the voltage stress across the active switches decrease. The active switches turn ON under zero-voltage switching condition in both directions. Moreover, the low current ripple at the LVS is achieved due to the applied interleaved technique. By employing the phase-shift angle modulation, the output voltage is regulated. The proposed converter is analyzed in details and a 900-W experimental prototype with 48-V input voltage and 400-V output voltage under 100-kHz switching frequency is implemented to verify the theoretical results.

Efficiency optimisation of ZVS isolated bidirectional DAB converters

This study presents a control method for isolated bidirectional dual-active-bridge converters to optimise the efficiency by achieving the zero-voltage switching (ZVS) in high-voltage applications, which the switching losses are the major issues. At light-load condition, the duty control algorithm is proposed to achieve the ZVS for all switches while the triple phase shift with ZVS condition is realised at heavy load condition. The operating principles and the design considerations of the proposed control scheme are analysed in detail. A 2 kW prototype converter is built up and tested to verify the feasibility of the proposed control strategy.

Isolated high step‐up DC–DC converter with integrated cascade structure

In this study, an isolated high step-up DC-DC converter with integrated cascade structure is proposed. The converter structure is equivalent to that of a cascade consisting of a boost converter and an isolated buck-boost converter. Compared with existing converters, the proposed converter can achieve a higher voltage gain with a lower transformer turn ratio. In addition, the integrated structure makes the controller more reliable and the system more compact. As the leakage inductance energy of the transformer is released to the output capacitors, the voltage spike caused by leakage inductance can be avoided, thereby reducing the voltage stress of the switches. Moreover, the zero-voltage switching (ZVS) operation improves the conversion efficiency and the continuous input current makes a small peak current. This study discusses the operating principles of the discontinuous and continuous conduction modes in detail. The theoretical derivation of the proposed converter is provided, and the ZVS principle and conditions are presented. Finally, a prototype circuit with 40 V input voltage, 500 V output voltage, and 200 W output power is implemented to verify the validity of the theoretical analysis and the performance of the proposed converter.

A Dual Half-Bridge Phase-Shifted Converter With Wide ZVZCS Switching Range

This paper presents a phase-shifted dual-half-bridge converter, which achieves zero-voltage switching (ZVS) for the leading-leg switches and zero-current switching (ZCS) for the lagging-leg switches. The proposed converter contains two paralleled half-bridge inverters in the primary side. The rectifier stage is composed of six diodes connected with the form of full-bridge rectification. The ZVS condition is created by the output filter inductor and leakage inductor, while the ZCS condition is created by the blocking capacitors. A wide range of soft-switching operation can be achieved with small leakage inductors. Compared with the traditional phase-shifted full-bridge converter, the proposed converter can obtain a three-level output rectified voltage, and the power is transferred from the primary side to the secondary side during the whole period, which can significantly reduce the current ripple of the output filter inductor. In this paper, the operation principle and relevant analysis are presented. A laboratory prototype is built to verify the performance of the proposed converter.

Cascaded High Voltage Conversion Ratio Bidirectional Nonisolated DC–DC Converter With Variable Switching Frequency

In this paper, a multistage nonisolated high voltage conversion ratio (VCR) bidirectional dc–dc converter is proposed. The VCR is n times of the conventional buck/boost converter using only $n+ {\text{2}}$ switches. All the switches can achieve full-range zero voltage switching (ZVS) despite the power flow direction. The operating principle, ZVS condition, and design considerations of a four-stage topology are analyzed in detail. In addition, an improved dynamic switching frequency modulation is proposed to reduce the power loss. Analyses and comparisons between the conventional constant frequency and variable frequency control are made to show the effectiveness. A 500-W experimental prototype interfacing 20–30 V with 270 V is fabricated to verify the performance of the proposed converter and control strategy.

Implementation of two‐output three‐level series‐resonant inverter for induction melting application

This study aims to present a two-output three-level series-resonant inverter together with an implementation and experiments for an induction melting application. A three-level circuit is applied for each branch of inverter in order to decrease the voltage stress on switching devices. A phase-shifted pulse-width modulation (PSPWM) with variable frequency control is applied for providing and maintaining a zero-voltage switching condition over a wide load range. In addition, the PSPWM could provide symmetrical output voltage and current waveforms that result in decreasing the THD v and THD i of output waveforms and harmonic losses of high-frequency transformer cores comparing to other PWM schemes. Finally, the prototype was designed, built, and tested to verify the consistency between the experimental results and theories of the proposed inverter.

Simulation and Analysis of Multiphase Boost Converter with Soft-Switching for Renewable Energy Application

<span>This paper presents the simulation design of dc/dc interleaved boost converter with zero-voltage switching (ZVS). By employin the interleaved structure, the input current stresses to switching devices were reduced and this signified to a switching conduction loss reduction. All the parameters had been calculated theoretically. The proposed converter circuit was simulated by using MATLAB/Simulink and PSpice software programmes. The converter circuit model, with specifications of output power of 200 W, input voltage range from 10~60 V, and operates at 100 kHz switching frequency was simulated to validate the designed parameters. The results showed that the main switches of the model converter circuit achieved ZVS conditions during the interleaving operation. Consequently, the switching losses in the main switching devices were reduced. Thus, the proposed converter circuit model offers advantages of input current stress and switching loss reductions. Hence, based on the designed parameters and results, the converter model can be extended for hardware implementation.</span>

Wide-Range Adaptive IPT Using Dipole-Coils With a Reflector by Variable Switched Capacitance

A dipole-coil-based inductive power transfer (IPT) with a reflector, which first adopts the variable switched capacitance for load power regulation under very wide-range distance variation between transmitter (Tx) and receiver (Rx) coils, is newly proposed. The resonant frequency of the LC tank of the proposed IPT can be appropriately modulated by the variable switched capacitance with reliable zero-voltage-switching (ZVS) operations. Therefore, even though the distance changes very widely, load power can be regulated solely by the variable switched capacitance in the Rx circuit without complicated communication links between the Tx and Rx coils. A detailed static analysis based on a recent imaginary gyrator model and design procedure for the proposed IPT are presented to build a simplified LC resonant tank of the proposed IPT and ZVS condition and to identify applicable distance variation range for constant load power. A prototype of the Tx and Rx coils for 100 W of load power, considering average power consumptions of home appliances, was fabricated and verified by simulations and experiments, which showed that load power was completely regulated to 100 W for 23–70 cm of very wide-range distance variation at a fixed switching frequency of 140 kHz.

Single‐stage soft‐switched PWM flyback power factor correction with reduced dead angle

This study proposes a single-stage zero-voltage transition pulse width modulation (PWM) flyback power factor correction converter. The bulk capacitor voltage is controlled by using negative magnetic feedback (NMF) without any input current dead angle. In the proposed circuit, the main and auxiliary switches turn on and off under zero-voltage switching and zero-current switching conditions, respectively. The proposed auxiliary circuit provides soft switching condition while eliminating the dead angle caused by NMF winding. Thus, high-efficiency and high-power factor is achieved. Experimental results obtained from a 160 V/300 W circuit are provided to verify that the proposed structure can suppress the dead angle at zero crossing and soft switching of all switches can be achieved properly.

A High-Frequency Isolation (HFI) Charging DC Port Combining a Front-End Three-Level Converter with a Back-End LLC Resonant Converter

The high-frequency isolation (HFI) charging DC port can serve as the interface between unipolar/bipolar DC buses and electric vehicles (EVs) through the two-power-stage system structure that combines the front-end three-level converter with the back-end logical link control (LLC) resonant converter. The DC output voltage can be maintained within the desired voltage range by the front-end converter. The electrical isolation can be realized by the back-end LLC converter, which has the bus converter function. According to the three-level topology, the low-voltage rating power devices can be adapted for half-voltage stress of the total DC grid, and the PWM phase-shift control can double the equivalent switching frequency to greatly reduce the filter volume. LLC resonant converters have advance characteristics of inverter-side zero-voltage-switching (ZVS) and rectifier-side zero-current switching (ZCS). In particular, it can achieve better performance under quasi-resonant frequency mode. Additionally, the magnetizing current can be modified following different DC output voltages, which have the self-adaptation ZVS condition for decreasing the circulating current. Here, the principles of the proposed topology are analyzed in detail, and the design conditions of the three-level output filter and high-frequency isolation transformer are explored. Finally, a 20 kW prototype with the 760 V input and 200–500 V output are designed and tested. The experimental results are demonstrated to verify the validity and performance of this charging DC port system structure.

A high step-up DC–DC soft-switched converter using coupled inductor and switched capacitor

ABSTRACTIn this paper, a zero-voltage-switching (ZVS) high step-up three level coupled inductor-based boost converter is proposed. Three-level structure of the proposed converter causes significant reduction of the switches and diodes voltage stress. The leakage inductance that is caused by coupled inductor leads to voltage ringing, the use of the active-clamp circuit in this structure not only eliminates the voltage ringing but also makes all switches turn on and off under ZVS condition that results in improving the efficiency. All the switches in the proposed converter will operate with an appropriate duty cycle for high step-up applications. The proposed converter features, operating principles and analysis are discussed in the paper and to verify the validity of theoretical analysis, the experimental results of a 200-W laboratory prototype with a 4-V input and 400-V output are presented.

Quasi‐resonant DC‐link H5 PV inverter

By removing transformer from PV inverters, they become more attractive for distributed power generation systems. Regardless of their some extra leakage currents, transformer-less inverters would be more advantageous regarding their higher efficiency. However, using traditionally hard-switching converters still causes to drastic switching losses, high di/dt and electromagnetic interference. Quasi-resonant DC-link techniques have promising features to provide zero-voltage switching (ZVS) condition for full bridge inverters, but they are not suitable for transformer-less PV inverters due to consequent high leakage current. In this study, a transformer-less PV inverter is proposed by adapting a proper quasi-resonant DC-link technique to the H5 topology. Using only two auxiliary switches, ZVS turn on and turn off for high-frequency bus switch and ZCS turn on and ZVS turn off for high-frequency switches of the bridge as well as ZVS turn on and turn off of the antiparallel diodes of main switches are realised. Zero current switching (ZCS) turn on and ZVS turn off for auxiliary switches and ZVS turn on and ZCS turn off for antiparallel diodes are also provided. To verify the proposed circuit operation, a 20 kHz 1 kW quasi-resonant DC-link H5 PV inverter prototype is implemented and operation characteristics, soft switching conditions and design rules are confirmed.

Two-Switch Forward Converter With Reset Winding and an Auxiliary Active-Clamp Circuit for a Wide Input Voltage Range

In this study, a two-switch forward converter with reset winding and an auxiliary active-clamp circuit for a wide input voltage range are proposed. The proposed converter offers simple reset scheme through reset winding, while retaining the reduced voltage stress on the switches. Hence, the operating duty ratio can be extended. Furthermore, it can also attain zero-voltage switching (ZVS) through the auxiliary active-clamp network when magnetizing inductor is properly designed. The operation principle of the proposed converter is analyzed. Analyses of the extended duty ratio and ZVS condition are then conducted in detail based on mode analysis. The performance of the proposed converter is evaluated using a 100-kHz 300-W/48-V prototype converter for an input voltage range of 200–400 V.

A New Family of Single-Switch ZVS Resonant Converters

This paper presents a new family of soft-switching resonant dc–dc converters. The proposed topologies include only one switch, two diodes and one high-frequency resonant LC tank. Zero-voltage switching condition is provided for the switch and thereby the converter power density and efficiency are enhanced considerably. Unlike quasi-resonant converters and soft-transition (ZVT/ZCT) converters, which have inherited a relatively large inductor from their PWM parents; in the proposed converters, only one small inductor is employed. The proposed family includes three step-down, three step-up, and three step-down/up converters. Complete analysis of the step-down converter is presented in this paper. Summarized key results of other topologies are also provided. Experimental results from a 100 W/445 kHz laboratory prototype are presented for verification.

High step‐up dual full‐bridge ZVS DC–DC converter with improved integrated magnetics and new resonant switched capacitor cell

A high voltage gain dual interleaved full bridge converter with Zero Voltage Switching (ZVS), improved integrated magnetics, and a new resonant Switched -Capacitor-Cell (RSC) is presented. By taking the advantage of a new resonant switched capacitor cell and transformers with low turn-ratio as well as low leakage inductances, the desired high output voltage can be obtained. Furthermore, the output diodes operate in Zero Current Switching (ZCS) condition, and switches are maintained under ZVS condition over the whole range of output load variations. In addition, switches turn off near zero current leading to high overall efficiency. An interleaved approach (multi-cell) is adopted over a single cell to increase the power handling capacity. Furthermore, transformers of dual cells are integrated into a single UU core which cuts down the total volume of the converter as well as the total core loss. Since secondary windings have opposite polarities, there exists no DC flux, and the top and bottom RSC cells operate in 180 degree out of phase. Taking the aforementioned characteristics into consideration, the proposed converter has a good performance for high voltage applications. Experimental results of a 3 kw prototype with an output voltage of 16 kV validate the features of this topology.

Soft-Switching Dual-Flyback DC–DC Converter With Improved Efficiency and Reduced Output Ripple Current

This paper presents a soft-switching dual-flyback dc-dc converter with improved efficiency and reduced output ripple current. Zero-voltage-switching (ZVS) technique and a dual-flyback module for reducing the number of snubber current paths are adopted to improve efficiency. For the ZVS technique, a self-driven synchronous rectifier (SR) is used instead of an output diode. By turning the self-driven SR off after a short delay, a main switch is turned on under the ZVS condition. For reducing the number of snubber current paths, a dual-flyback module and a snubber diode are used. When the main switch is turned off, leakage inductance energy is absorbed by a snubber diode into an input source and a primary dc-bus capacitor. Then, this energy is reprocessed by the dual-flyback dc-dc module to secondary side. Hence, there is only one snubber current path. In addition, the proposed converter features a reduced output ripple current because of the continuous current. Consequently, the proposed converter can achieve high efficiency and reduced output ripple current. To verify the performance of the proposed converter, operating principles, steady-state analyses, and experimental results from a 340 to 24-V, 100-W prototype are presented.