Soft-switching Characteristics Research Articles

A Single-Stage Electrolytic-Capacitor-Free AC–DC LED Driver With High Power Factor and Soft Switching Characteristics

A Single-Stage Electrolytic-Capacitor-Free AC–DC LED Driver With High Power Factor and Soft Switching Characteristics

A Review of Non-Isolated High-Gain Y-Source Converters Topologies

Due to the low voltage and high randomness of renewable energy, high-performance grid-connected converters are needed. With the advantages of a high boost ratio, flexible design, and simple control, the Y-Source Converter (YSC) is widely concerned. However, there are a few drawbacks to the traditional Y-source converter, including significant switching stress, voltage voltage overshoot, and discontinuous current. To solve the problems above, a series of improved topologies are proposed. Moreover, the voltage gain, current ripple, and soft switching characteristics have also been optimized. So far, the existing literature lacks the collation and comparison of different topologies of Y-source, as well as the analysis of its evolution process. Therefore, this paper provides a comprehensive overview of Y-source converters’ topologies. According to their features and applications, different topologies are classified and described, leading to guidance for the selection of YSCs under different scenarios. Meanwhile, the working principle, evolution process, and vital issues are analyzed. By revealing their deductive rules, valuable suggestions are provided for the future development of YSCs.

Dual-Side Asymmetric Duty Modulation Based on Accurate Soft-Switching Characteristics Modeling for DAB-Based DC Microgrid

Dual-Side Asymmetric Duty Modulation Based on Accurate Soft-Switching Characteristics Modeling for DAB-Based DC Microgrid

A high step-up soft-single switched converter with three coupling inductors

ABSTRACT This paper presents a new high voltage gain converter, which bases on the incorporation of the voltage multiplier cell and the switched coupled inductor technique, having low voltage stress on the switch, which is far from the output voltage. The presented topology is well suited for high step-up applications. By integrating coupled inductors and voltage multiplier cell techniques, a high step-up voltage gain is achieved. All of the semiconductor devices are switched under soft switching conditions, which reduces the switching losses significantly. The switch turns on at ZCS and turns off at ZVS. All diodes have soft-switching features and their reverse recovery problem is obviated due to the leakage inductance. The operation principles and theoretical analysis of proposed converter are presented in details. At the end, the experimental results have been taken from a laboratory prototype rated at 100 W, input voltage of 24 V, output voltage of 300 V, and switching frequency of 100 kHz.

Analysis of A Bidirectional Resonant Converter Applied in High/Low Voltage Conversion

In order to ensure the safe and reliable operation of the ship, the emergency power supply of the ship can provide short-term power supply when the main power supply of the ship fails. This paper proposes a two-way LLC resonant converter to be used in marine emergency power supplies. While ensuring the high efficiency and soft switching performance of the converter, it realizes high and low voltage conversion and bidirectional energy flow. By analyzing the topology, working principle and gain under variable frequency control of the two-way LLC resonant converter, and constructing the principle prototype and verifying its performance, the experiment shows that the application of the two-way LLC resonant converter in the emergency power supply can achieve high and low voltage The conversion and has good soft switching characteristics.

A Novel Impedance Matching of Class DE Inverter for High Efficiency, Wide Impedance WPT System

In high-frequency wireless power transfer (WPT) applications, Class D, E, and F inverters are most widely used. Class DE inverters combine the respective advantages of Class D and Class E inverters. However, the Class DE inverter is sensitive to changes in impedance, which can easily lead to the loss of soft switching characteristics, thereby reducing efficiency. In this paper, an impedance-matching compensation design method is proposed to expand the high-efficiency region of the Class DE inverter by matching impedance and parameters. The effect of the method on the zero-voltage switching (ZVS) characteristic of Class DE inverters is analyzed in detail. The proposed WPT system maintains a constant voltage and zero phase angle by employing PS/PS compensation topology. Theoretical analysis shows that the impedance can be compressed for the design of resonant network impedance, and the method can expand the high-efficiency region with a reasonable choice of parameters to match the phase. Finally, a 500 kHz, 1 kW WPT prototype was constructed with a coupling factor of 0.25–0.4 and a load range of 30–80 Ω. The inverter’s efficiency exceeds 95%, with optimal efficiency reaching 97.3%. The system efficiency is greater than 87%.

A Novel Integrated Electronic Lighting Driver Circuit for Supplying an LED Projection Lamp with High Power Factor and Soft Switching Characteristics

The traditional light source of projection lamps adopts a halogen lamp, which has the advantages of high brightness, but its luminous efficiency is not good and consumes energy. A light-emitting diode (LED) has the characteristics of high luminous efficiency and energy savings and can be used as a new light source for projection lamps. The conventional two-stage electronic lighting driver circuit for supplying an LED projection lamp is composed of an AC-DC converter with power factor correction (PFC) as the first stage and a DC-DC converter for providing rated lamp voltage and current as the second stage. The conventional LED projection lamp driver circuit has more circuit components, a higher cost and limited efficiency. Therefore, this paper proposes a novel electronic lighting driver circuit for supplying an LED projection lamp with PFC function, which integrates a modified stacked dual boost converter and a half-bridge LLC resonant converter into a single-stage power-conversion circuit. The inductor inside the modified stacked boost converter is designed to operate at discontinuous conduction mode (DCM) for the driver circuit achieving PFC. Wide bandgap semiconductor devices silicon carbide (SiC)-based Schottky diodes are utilized to reduce power diode losses, and soft switching is implemented in the proposed LED projector lamp driver circuit to reduce the switching losses of the power switches and thus improve circuit efficiency. This paper has completed a single-stage prototype driver circuit for an LED projection lamp with PFC function, and the prototype circuit has a high power factor (PF > 0.98), low input current total-harmonic-distortion (THD < 6%) and high efficiency (>89%) in the case of an AC input power supply with an RMS value of 110 volts, and both power switches have the characteristics of soft switching.

Characterization and Mitigation of Dimensional Effects on Core Loss in High-Power High-Frequency Converters

To date, LLC Resonant converters are deployed in many applications for improved efficiency, density, and reliability. With the introduction of WBG devices coupled with the soft switching feature, the switching frequency can be extended beyond MHz. With the significant increase in operating frequency, complicated magnetic components can be broken down into a cellular structure, each with a few number of turns. They can be easily implemented using 4-6 layers of PCB windings. Moreover, integrating the cellular cores using flux cancellation can further improve the power density. The proposed integrated magnetics can be automated in the manufacturing process. With the recently developed high-frequency core material, phenomena referred to as the dimensional effects on core loss are observed. The dimensional effects were discussed in the literature when using an unusually large core structure; however, at high excitation frequencies, it can be observed more frequently, particularly with integrated magnetic components. In this paper, we give an overview of the dimensional effects on core loss, namely flux crowding, dimensional resonance, and eddy loss, with the latest being a dominant factor in the 1 MHz transformer loss. We also introduce a practical method for the characterization of the dimensional effects to help engineers better their design of the high frequency converter. This includes measuring the ferrite material characteristics and evaluating the dimensional effects using Finite-Element Analysis. Finally, a case study of 1MHz 400-to-48 V converter design is presented, showing superiority in both power density and efficiency metrics compared to other reported literature from the same category. This shows the importance of including the dimensional effects and, specifically, the core eddy loss in the design procedure.

Novel Control Approach for Resonant Class-DE Inverters Applied in Wireless Power Transfer Systems

Regulating the load voltage is of major importance for ensuring high transmission efficiency in wireless power transfer (WPT) systems. In this context, this work presents a novel control strategy applied in the dc-ac converter used in the primary side of a WPT system. The performance of a class-DE resonant inverter is investigated considering that such topology presents inherent soft-switching characteristics, thus implying reduced switching losses. The controller relies on an autoregressive with exogenous output (ARX) model based on an adaptive linear neuron (ADALINE) network, which allows for determining the turn-on time of the active switches accurately while providing the system with the ability to adapt to distinct alignment conditions. The performance of the proposed controller is compared with that of a linear controller, which does not prove to be an effective solution if misalignment occurs.

An Input-Current Shaping and Soft-Switching Drive Circuit Applied to a Piezoelectric Ceramic Actuator.

Piezoelectric ceramic actuators utilize an inverse piezoelectric effect to generate high-frequency vibration energy and are widely used in ultrasonic energy conversion circuits. This paper presents a novel drive circuit with input-current shaping (ICS) and soft-switching features which consists of a front AC-DC full-wave bridge rectifier and a rear DC-AC circuit combining a stacked boost converter and a half-bridge resonant inverter for driving a piezoelectric ceramic actuator. To enable ICS functionality in the proposed drive circuit, the inductor of the stacked boost converter sub-circuit is designed to operate in boundary-conduction mode (BCM). In order to allow the two power switches in the proposed drive circuit to achieve zero-voltage switching (ZVS) characteristics, the resonant circuit of the half-bridge resonant inverter sub-circuit is designed as an inductive load. In this paper, a prototype drive circuit for providing piezoelectric ceramic actuators was successfully implemented. Experimental results tested at 110 V input utility voltage show that high power factor (PF > 0.97), low input current total harmonic distortion (THD < 16%), and ZVS characteristics of the power switch were achieved in the prototype drive circuit.

Variable Frequency Isolated Bidirectional CLLC Resonant Converter With Voltage Controlled Variable Capacitors

This paper proposes a novel variable frequency isolated bidirectional CLLC resonant converter with voltage-controlled variable capacitors (VCVCs) and auxiliary clamp circuits (ACCs). By employing the class II ceramic capacitors as VCVCs, the converter's modes in one switching cycle and the transient process to set up the DC voltage bias on VCVCs are analyzed detailly to explain the fundamental principles and lossless characteristics of ACCs in the steady state. Suitable ranges of capacitor voltage stress and current stress and gain characteristics of the converter are also given to design the resonant parameters. The converter's soft-switching characteristics, fast transient process, and high efficiency are well demonstrated by the experimental results obtained on a 500 W prototype. The high-efficiency range of the proposed converter with the VCVCs is 20%∼100%, which is at least 10% wider than the others without VCVCs.

Design and Optimization of High-Gain Bidirectional DC–DC Converter for Electric Vehicles

To better leverage and cope with the characteristics of low-voltage electric vehicle battery pack, this work optimizes the design of on-board bidirectional DC/DC converter. Based on the dual active half-bridge (DAHB) converter, combined with partial switch sharing, a high gain bidirectional DC/DC converter is proposed. This converter has 48-V and 24-V output voltage levels, and the multiple voltage levels, which are often required by new energy vehicles, are able to reduce the number of on-board converters. The theoretical part of this work analyzes the design process of the converter, and in parallel, establishes the mathematical models of transmission power, soft switching, current stress and reactive backflow loss. Under the condition of high gain, the system has good soft switching characteristics and low reactive backflow loss. In the experimental part, a prototype with an input voltage of 400V is built under an operating frequency of 100 kHz. The voltage of the two output ports is stable and a peak efficiency of 94.7% is achieved. The experimental results verify the validity of the theoretical analysis.

Design and Comparative Analysis of an Ultra-Highly Efficient, Compact Half-Bridge LLC Resonant GaN Converter for Low-Power Applications

For low-power applications, this paper presents the development and design of a compact and ultra-highly efficient half-bridge LLC resonant converter. By using Galium Nitride (GaN) devices and high-efficient magnetics, the efficiency and power density of resonant converters can be improved. Compared to Silicon MOSFETs, GaN high-electron-mobility transistors (GaN HEMT) have a lower output capacitance and gate charge, resulting in lower driving loss and shorter dead times. Consequently, the proposed LLC converter based on GaN devices has excellent performance characteristics such as ultra-high efficiency, low switching losses, compact size, high voltage endurance, high operating temperature and high operating frequency. Furthermore, the proposed resonant converter features soft switching properties that ensure that the switches and diodes on the primary side are always switched at zero voltage and current. By doing so, LLC resonant converter switching losses are significantly reduced by up to 3.1%, and an overall efficiency of 98.5% is achieved. The LLC resonant converter design with GaN HEMT has great advantages over Si MOSFET solution regarding efficiency, overall losses, switching loose and power factor correction. A 240 W, 240 V to 60 V half-bridge GaN HEMT LLC resonant converter is simulated with a switching frequency of 75 KHz, along with the comparative analysis of the Si metal oxide semiconductor field effect transistor (MOSFET) solution. Moreover, the design and analysis of highly efficient magnetics with a power factor of 0.99 at full load is presented. A 240-Watt single stage LED driver with power factor correction is also designed to verify and compare the performance of proposed LLC resonant converter.

Towards Full Range Zero-Voltage Switching of DAB Converters: An Improved Multi-Mode Modulation at Light Loads Under Close-to-Unity Voltage Ratio

The soft switching characteristics of ZVS are of great significance for reducing the switching loss and improving the efficiency of the converter. However, affected by non-ideal factors, the DAB converter using the three-phase-shift modulation method has an inherent non-ZVS region. This paper proposes a novel operating mode to fill the non-ZVS area with ZVS operation where the input and output voltage are close to match with. What's more, combined with the existing mixed-mode modulation method and dynamic-process modulation method, the ZVS operation of DAB in full voltage gain range and full power range under all working conditions can be realized.

Frequency‐adapted hybrid modulation strategy of resonant converter with narrow frequency range

SummaryResonant converters have been widely applied in many fields, such as electric vehicles, renewable energy sources, and switch‐mode power supply. Conventional resonant converters generally adopt pulse frequency modulation (PFM), which would cause an extremely wide frequency variation range under wide output applications. However, it would lead to high electromagnetic interference (EMI), low utilization of magnetic components, and loss of soft switching features. For catering to wide output range applications, this paper proposes a self‐adaptive narrow frequency range PFM and asymmetrical voltage‐cancelation hybrid modulation strategy to solve the above problem. The advantages of the proposed strategy include (1) narrow frequency variation range; (2) self‐adaptive shift frequency; and (3) full process achievement of zero voltage switch. The modulation strategy and operational principle and performance analysis of the proposed method are given. Eventually, a series resonant converters–based experimental platform was implemented to verify the proposed strategy.

A wide zero-voltage-switching range with low reactive power modulation strategy for LCL resonant three-phase dual active bridge DC–DC converter in renewable energy generations

LCL resonant three-phase dual active bridge (LCL-TPDAB) dc–dc converter is progressively used in renewable energy systems due to the advantages of low circulating reactive power and wide voltage regulation. Conventional dual-phase-shift (DPS) modulation can effectively reduce the circulating reactive power of the converter, but it cannot achieve zero-voltage-switching (ZVS) of all switches, which increases switching losses and generates electromagnetic interference. To solve the above problems, an optimized modulation strategy based on phase-shift plus duty cycle (PSPDC) control is proposed in this paper. Firstly, the mathematical model of the LCL-TPDAB converter with the PSPDC modulation is established by harmonic analysis. Then, the relationship between the ZVS boundaries and the control variables is determined by analyzing the soft-switching characteristics. In order to accurately describe the ZVS boundaries, the impact of switch junction capacitance is considered in the analysis. Further, an optimized modulation strategy is proposed, which can achieve ZVS for all switches and low reactive power in the whole operating range. Furthermore, the offline particle swarm optimization (PSO) algorithm is introduced to acquire the optimal control variables in the operation of the converter. Finally, a 1.5 kW experimental prototype is applied to verify the effectiveness and excellence of the proposed optimized modulation strategy, where the efficiencies are improved in the whole operating range.

Bidirectional CLLLC Resonant Converter Based on Frequency-Conversion and Phase-Shift Hybrid Control

Due to the symmetrical structure, consistent working characteristics in the forward and reverse operations, and good soft-switching characteristics, bidirectional CLLLC resonant converters are widely used in electric vehicles and other fields. To meet the requirements of the on-board charger, this paper uses a bidirectional CLLLC resonant converter as the rear-stage of the on-board charger. The converter uses a constant voltage and constant current control in the forward operation and voltage and current double-closed-loop control in the reverse operation. Aiming at the problem whereby the voltage gain range of the bidirectional CLLLC resonant converter is relatively narrow under frequency-conversion control, the paper proposed a hybrid control method of frequency conversion and phase shift. Frequency-conversion control is used when the voltage gain is high, and phase-shift control is used when the voltage gain is low. The output voltage range of the converter is effectively broadened, and zero voltage switching and zero current switching can be realized in the full load range to improve operating efficiency. A 3.3 kW bidirectional CLLLC resonant converter simulation system is built in the simulation software. The simulation results verify the correctness and feasibility of the designed circuit and control method.

A high efficiency multi-module parallel RF inverter system for plasma induced hydrogen

Hydrogen energy plays an important role in achieving carbon neutralization, and plasma induced hydrogen is an effective production method. One challenge is how to guarantee high efficiency operation with wide power output range of the RF inverter system used to generate the plasma. In this paper, a multi-module parallel topology of a high-frequency inverter is analyzed, in which the power combining network can maintain the soft switching characteristics of the inverter modules. A control method of "ON/OFF + phase shift" is adopted to broaden the output power range of the inverter. The equivalent impedances of different modules are analyzed in detail. A four-module 13.56 MHz high-frequency inverter prototype is built and tested. The results show that the inverter can operate at high efficiency and wide output power range with efficiency improved by at least 5% compared with the traditional parameter design method without considering the effect of paralleled modules.

A New Soft-Switching AC–DC Converter Based on Coupled Inductors for Onboard Charging Applications

This article proposes a soft-switching full-bridge ac–dc converter consisting of its hard-switching counterpart and simple active auxiliary branch. The auxiliary branch is composed of an inductor and two power switches. The proposed converter features zero voltage switching (ZVS) turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> for main switches and zero current switching (ZCS) condition for auxiliary switches. The ZVS condition is created by turning on auxiliary switches ahead of the main switch turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> signal to reversely excite the auxiliary inductor. The two mutually coupled inductors connected in series in opposing magnetic field manner are designed as the main filter inductor and to provide positive voltage for the auxiliary inductor to degauss it as well. Meanwhile, the auxiliary inductor contributes ZCS turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">on</small> and turn- <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">off</small> to the auxiliary switches because it slows down the change rate of the current through the switches. Considering the parasitic capacitors of the auxiliary switches inevitably resonate with the auxiliary inductor, a clamping technique is given to alleviate the additional voltage stresses caused by the resonance. Then, the mathematical parameter design is deduced to guide the converter realization. Finally, a laboratory prototype with 1000 W rated power operating at 50 kHz switching frequency is completed and tested to demonstrate the soft-switching features. The efficiency of the proposed converter is up to 97.67% at full load and the maximum efficiency improvement is 5.3% at light load, which further highlights the outstanding performance.

Long Life Power Factor Corrected LED Driver with Capacitive Energy Mechanism for Street Light Applications

Conventional switch-mode LED drivers have problems such as poor performance in harmonic distortion, flickering, power factor correction, stresses on the switches, high switching losses, large size, and high cost. To resolve these problems, we propose a long-life LED driver with the ability of power factor correction. The proposed system is based on the integration of a half-bridge LLC resonant converter and two boundary-conducted boost converters. Both boost converters share a common inductor designed in such a way that both boost converters work in boundary conduction mode to attain the natural power factor correction. Half-bridge LLC resonant converter has soft switching characteristics, which assure the zero-voltage switching (ZVS) of primary-side switches and zero-current switching (ZCS) of diodes on the secondary side. This significantly reduces switching losses and improves the overall efficiency of the system. Voltage divider capacitors are used on the input side, which minimizes the bus voltages. The proposed system has two identical secondary windings with a coupled inductor to eliminate the mismatch between them, which powers two independent LED strings. The simulation of a 100-watt 240 V AC converter yields the approximate sinusoidal shape of the input current. It shows that the switches on the primary side are operated in ZVS and the diodes in ZCS. At 240-volt AC input, the efficiency is 87.4%, the total harmonics distortion (THD) is 10.98%, and the power factor (PF) is 0.98.