Frequency Resonant Converter Research Articles

An Improved High-Frequency Resonant Converter With Design Considerations of Voltage-Driven Class-E Resonant Rectifier

Resonant inverter and resonant rectifier are indispensable for high-frequency resonant converters to achieve high power density, high conversion efficiency, and low electromagnetic interference. However, multiple inductors and capacitors excite complex resonances, impeding the precise parameter design through numerical computations. For the resonant rectifier, the trial method by sweeping resonant frequency and impedance parameters in simulation tools is commonly adopted, which simplifies the design procedure. Nevertheless, it relies heavily on the accuracy of simulation tools and considers only the fundamental wave. This article aims to provide a design methodology for the voltage-driven class-E resonant rectifier based on accurate calculation and comprehensive consideration. Furthermore, both harmonic factors and different connections between the inverter stage and the rectifier stage are taken into considerations. A family of improved high frequency resonant converters is presented, which enhances efficiency significantly. The operating principles analysis is expounded, and the circuit characteristics are summarized. The experimental results on the prototypes built in the laboratory demonstrate the feasibility of the theoretical analysis.

Research on current‐type high frequency resonant power converter based on magnetic energy recovery switch

LCL resonant converters have been widely used to get a constant current output. This paper proposes an LCL resonant converter based on the magnetic energy recovery switch (MERS), which adjusts the output current of the converter by controlling the paralleled equivalent capacitance, as responding to the parameter errors or input voltage disturbance. Firstly, based on the equivalent model of the LCL resonant converter, the effect of variable capacitive impedance on the output current characteristics of the converter is analysed. Then the topological structure of MERS is introduced and its working principle as a controllable capacitive impedance controller is further explained. On this basis, the operating characteristics and soft switching characteristics of the proposed topology in each complete working cycle are analysed in detail. By controlling the phase shift angle between the output voltage of bridge and the fundamental component of MERS voltage, the equivalent capacitance of the MERS is changed, and the resonant frequency of the converter is accordingly adjusted to accurately compensate the output current against the input voltage disturbance. Finally, the effectiveness and feasibility of the MERS applied to the LCL resonant converter are verified by simulation and experiments. Besides, its operating characteristics are analysed and evaluated.

Harmonic analysis of VHF resonant converter based on equivalent nonlinear controlled model

AbstractLifting operating frequency can effectively reduce the size of energy‐storage components and increase the power density of converters, thus the very high frequency (VHF) resonant converters can find wide applications in practice. In order to further study the characteristics of VHF converters, a modeling method is presented for solving the state variables. First, according to the analysis of a typical VHF converter's operating modes, a unified equivalent circuit is established, which contains nonlinear controlled current sources. Then the mathematical model of the equivalent circuit is derived and solved by using the equivalent small parameter (ESP) method. And the approximate analytical solutions of state variables can be finally obtained, which are composed of a DC component and various harmonics. It is shown that the obtained solutions are accurate enough as the results from the proposed method agree well with the simulations and experimental results. Furthermore, the approximate analytical expressions for harmonics of state variables can be used as a guide for circuit design and stability analysis of the converter.

High Frequency, High Efficiency, and High Power Density GaN-Based LLC Resonant Converter: State-of-the-Art and Perspectives

Soft switching for both primary and secondary side devices is available by using LLC converters. This resonant converter is an ideal candidate for today’s high frequency, high efficiency, and high power density applications like adapters, Uninterrupted Power Supplies (UPS), Solid State Transformers (SST), electric vehicle battery chargers, renewable energy systems, servers, and telecom systems. Using Gallium-Nitride (GaN)-based power switches in this converter merits more and more switching frequency, power density, and efficiency. Therefore, the present paper focused on GaN-based LLC resonant converters. The converter structure, operation regions, design steps, and drive system are described precisely. Then its losses are discussed, and the magnets and inductance characteristics are investigated. After that, various interleaved topologies, as a solution to improve power density and decrease current ripples, have been discussed. Also, some challenges and concerns related to GaN-based LLC converters have been reviewed. Commercially available power transistors based on various technologies, i.e., GaN HEMT, Silicon (Si) MOSFET, and Silicon Carbide (SiC) have been compared. Finally, the LLC resonant converter has been simulated by taking advantage of LTspice and GaN HEMT merits, as compared with Si MOSFETs.

Power Quality Improvement in Induction Heating System Using Vienna Rectifier Based on Hysteresis Controller

—Induction heating (IH) technology is increasingly implemented in domestic, industrial as well as medical applications in the modern era. Designing of modern IH system incorporates high frequency (HF) resonant converter that results in the generation of HF harmonics. The HF harmonics has an inherent tendency to back flow toward the supply side and deteriorates the power quality at the grid side. So, in order to mitigate this power quality issue, a single phase Vienna rectifier (1-ø VR) based IH system has been proposed. Hysteresis and pulse density modulation controller is employed in the proposed IH system. The unidirectional nature of VR protects the overall IH system from the HF harmonics. VR also improves the power factor of the input supply along with low total harmonic distortion of input current. The feasibility of the proposed IH system is validated through MATLAB/Simulink environment. Finally, an experimental prototype of 1200 W has been developed and further correlated with the simulation results to verify the uniqueness of the proposed IH system.

High Frequency Resonant Converters: An Overview on the Magnetic Design and Control Methods

Resonant converters, especiallyLLC converters, are deployed in many applications thanks to their reliability and high efficiency. With the introduction of wide band gap (WBG) devices and the soft switching feature of the LLC converter, the switching frequency of the LLC can be pushed to the order of megahertz, to shrink the converter size and increase the power density. However, magnetic design and control challenges stand in the way of doing so. This article addresses the challenges of high-frequency magnetic design for the LLC converter, and presents an overview for the latest solutions on the magnetic design of the LLC transformer. The matrix transformer is suitable for an LLC converter where high output current at high frequency is required. Different integration methods for the matrix transformer are discussed and demonstrations of hardware prototypes are provided. The dynamic behavior of the LLC converter presents another significant challenge against deploying an LLC converter in applications where fast transient response is needed. This article discusses such challenges as well and provides an overview on the latest control techniques, including average current-mode control, charge control, and simplified optimal trajectory control, to improve the dynamic performance of an LLC converter. A 1 megahertz LLC converter with digital control is presented, using simplified optimal trajectory control with improved transient performance over a wide frequency range.

A review of high frequency resonant DC-DC power converters: Topologies and planar magnetic technologies

With the development of high frequency resonant DC-DC power converters, the system efficiency, power density and dynamic characteristics have been significantly improved. High frequency resonant DC-DC converters have been applied in DC grid, renewable energy, transportation, aerospace, point-of-load (POL) power supply and many other fields. Under high switching frequencies, switching loss and magnetic loss are the main concerns; thus, the resonant topology and planar magnetic are two key technologies to reduce loss. This review compares different resonant topologies and analyzes the advantages and disadvantages respectively, such as LLC circuit, dual active bridge (DAB) circuit, and other high order resonant circuits. For planar magnetic components, optimal winding structures, modeling methods and integration methods are thoroughly surveyed. With corresponding topics, the opportunities and challenges in the future development are summarized, which mainly focus on the characteristics of wide bandgap devices, such as the dynamic resistance, output capacitance loss and also the integrated module. This review can be a helpful guidance when designing high frequency resonant DC-DC converters.

Axion dark matter detection by superconducting resonant frequency conversion

We propose an approach to search for axion dark matter with a specially designed superconducting radio frequency cavity, targeting axions with masses ma ≲ 10−6 eV. Our approach exploits axion-induced transitions between nearly degenerate resonant modes of frequency ∼ GHz. A scan over axion mass is achieved by varying the frequency splitting between the two modes. Compared to traditional approaches, this allows for parametrically enhanced signal power for axions lighter than a GHz. The projected sensitivity covers unexplored parameter space for QCD axion dark matter for 10−8 eV ≲ ma ≲ 10−6 eV and axion-like particle dark matter as light as ma∼ 10−14 eV.

A Direct Mapped Method for Accurate Modeling and Real-Time Simulation of High Switching Frequency Resonant Converters

This article presents a direct mapped method (DMM) for real-time simulation of high switching frequency resonant converters. The DMM links state variables to diode statuses and provides an exact and noniterative solution to network equations. The proposed method is implemented on field programmable gate array (FPGA) to simulate an LLC converter with switching frequencies ranging up to 500 kHz. The best reported implementations of DMM achieve a 25-ns simulation time-step for a wide range of clock frequencies, ranging from 40 to 320 MHz.

An 8kW LLC resonant converter in plasma power supply based on SiC power devices for efficiency improvement

PurposeThis paper aims to present an 8 kW LLC resonant converter designed for plasma power supply with higher efficiency and lighter structure. It presents how to solve the problems of large volume and weight, low performance and low efficiency of traditional plasma power supply.Design/methodology/approachAt present, conventional silicon (Si) power devices’ switching performance is close to the theoretical limit determined by its material properties; the next-generation silicon carbide (SiC) power devices with outstanding advantages can be used to optimal design. This 8 kW LLC resonant converter prototype with silicon carbide (SiC) power devices with a modulated switching frequency ranges from 100 to 400 kHz.FindingsThe experimental results show that the topology, switching loss, rectifier loss, transformer loss and drive circuit of the full-bridge LLC silicon carbide (SiC) plasma power supply can be optimized.Research limitations/implicationsDue to the selected research object (plasma power supply), this study may have limited universality. The authors encourage the study of high frequency resonant converters for other applications such as argon arc welding.Practical implicationsThis study provides a practical application for users to improve the quality of plasma welding.Originality/valueThe experimental results show that the full-bridge LLC silicon carbide (SiC) plasma power supply is preferred in operation under conditions of high frequency and high voltage. And its efficiency can reach 98%, making it lighter, more compact and more efficient than previous designs.

EFFECT AND MECHANISM OF ACTION OF NON-THERMAL PLASMA IN THE SURVIVAL OF Escherichia coli, Staphylococcus aureus AND Saccharomyces cerevisiae

Non-thermal plasma (NTP) is an emerging technology of great interest because the elimination of pathogens and spoilage microorganisms and their probable use in various industrial sectors such as food and health. In this study was to evaluate the inactivation of non-thermal plasma on the survival of Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 51811 and Saccharomyces cerevisiae. Treatments of different microorganisms were conducted with cells exposed NTP generated dielectric barrier reactor (DBD) able to produce atmospheric pressure plasmas. These devices operate at 13.56 MHz and are driven by a specifically built radio frequency (RF) resonant converter. The reactors, which operate at atmospheric pressure in a He-air gas mixture at a 1.5 L min-1 flow rate, applying a 850 V voltage at different exposure times (10, 20, 40, 60, 80, 100 and 120 s). All the strains showed a reduction in viability of < 0.001 log CFU mL-1 after to exposed to plasma. The cells showed membrane damage, these effects being the main cause for microbial inactivation, caused by the action of Non-thermal plasma, which leads to membrane and/or cell wall breakdown with consecutive DNA denaturation, these being the main factors inducing microorganism death.

A High Power Medium Voltage Resonant Dual Active Bridge for MVDC Ship Power Networks

This paper presents the design and control of a megawatt scale, medium voltage, medium frequency resonant dual active bridge dc-dc converter operating as a bus-tie converter in a dc distribution network. The high voltage (HV) side of the converter is designed using series connected low voltage (LV) devices to efficiently operate at higher switching frequencies. A combined variable frequency and phase-shift control method is proposed to achieve input-output power flow and voltage control, while maintaining soft switching operation for both the HV and LV bridges. Two 1 MW converter prototypes operated in a back-to-back arrangement are presented to validate the proposed topology and control.

Analysis of the resonant LCL circuit operation: the case of discontinuous current

The article is focused on the analysis of the LCL resonant circuit, which operates under discontinuous input current condition. This condition leads to the LCL topology variability phenomenon what drastically changes Inverter-LCL system properties. The LCL topology variability phenomenon is precisely described. The analytical analysis presents formulae that express VSI-LCL converter features. The theoretical results are compared with laboratory tests. The concept of Controlled Variable Frequency Resonant Converter is presented and illustrated by simulation tests. The principle of CVFRC operation is based on the LCL topology variability phenomenon.

Evaluation of Gallium Nitride Transistors in High Frequency Resonant and Soft-Switching DC–DC Converters

The emergence of gallium nitride (GaN)-based power devices offers the potential to achieve higher efficiencies and higher switching frequencies than possible with mature silicon (Si) power MOSFETs. In this paper, we will evaluate the ability of gallium nitride transistors to improve efficiency and output power density in high frequency resonant and soft-switching applications. To experimentally verify the benefits of replacing Si MOSFETs with enhancement mode GaN transistors (eGaNFETs) in a high frequency resonant converter, 48–12 V unregulated isolated bus converter prototypes operating at a switching frequency of 1.2 MHz and an output power of up to 400 W are compared using Si and GaN power devices.

Bidirectional Semiconductor Transformer using high frequency resonant converter

This paper describes a prototype of modularized 3-phase semiconductor transformer which was developed in the lab for feasibility study. The developed prototype is composed of three units of single-phase semiconductor transformer coupled in Y-connection. Each single-phase unit has multiple units of high-voltage high-frequency resonant AC-DC converter, a low-voltage hybrid-switching DC-DC converter, and a low-voltage hybrid-switching DC-AC inverter. Also each single-phase unit has two DSP boards to control converter operation and to acquire monitoring data. Monitoring system was developed based on LabView by using CAN communication between the DSP board and the PC. Through diverse experimental analyses it was verified that the prototype operates with proper performance under normal and sag condition. The developed prototype confirms a possibility to fabricate a commercial high-voltage high-power semiconductor transformer by increasing the number of series-connected converter modules in high-voltage side and improving the system efficiency with a new switching device such as SiC device.

An Electrolytic Capacitor-less Bi-Directional EV On-Board Charger Using Harmonic Modulation Technique

This paper suggests a new electrolytic capacitor-less bi-directional on-board charger for electric vehicle. It has a cascade structure of constant frequency resonant converter for electrical isolation and DCM buck/boost converter for charging/discharging control and input harmonic regulation. Harmonic modulation technique is also proposed to obtain a high power factor and structure change method has been adopted to cope with a wide line voltage condition. Harmonic regulation and charging/discharging control can be accomplished with very simple control algorithm so that high performance controller is not required. Its feasibility has been verified with a 3-kW prototype.

Study on High-Voltage DC Power Supply for Electron Beam Furnace Based on Series Resonance

The high-voltage DC power supply for electron beam furnace belongs to Special Power Supplies. It has the characteristics of high voltage and high power. At present, the high voltage DC power supplies for electron beam furnace are mostly controlled by the silicon controlled rectifier operated by power frequency, which not only has the disadvantages of large volume but also doesn't has the characteristics of anti-short circuit capacity、 rapid protection and restart. This characteristic affects the service life of the electron gun and the quality of the smelting. To solve the above problems, a high frequency resonant converter has been used in high voltage power supply, reduced the volume of power supply and the switching loss, and achieved rapid protection and restart. Simulation and experimental research show that the power supply can meet the requirement of smelting.

An EL Capacitorless EV On-Board Charger Using Harmonic Modulation Technique

This paper suggests an electrolytic capacitorless on-board charger for electric vehicles. It has the cascade structure of a constant frequency resonant converter for electrical isolation and a discontinuous conduction mode boost converter for charging control and input harmonic regulation. To obtain a high power factor, the harmonic modulation technique is also proposed. The proposed charger uses a very simple algorithm to achieve harmonic regulation and charging control. Its feasibility has been verified with a 3-kW prototype.

Study on Performance Improvement of AC-DC Converter

Study on Performance Improvement of AC-DC Converter

A Driving Scheme Using a Single Control Signal for a ZVT Voltage Driven Synchronous Buck Converter

This paper deals with the optimization of the driving techniques for the ZVT synchronous buck converter proposed in [1]. Two new gate drive circuits are proposed to allow this converter to operate by only one control signal as a 12V voltage regulator module (VRM). Voltage-driven method is applied for the synchronous rectifier. In addition, the control signal drives the main and auxiliary switches by one driving circuit. Both of the circuits are supplied by the input voltage. As a result, no supply voltage is required. This approach decreases both the complexity and cost in converter hardware implementation and is suitable for practical applications. In addition, the proposed SR driving scheme can also be used for many high frequency resonant converters and some high frequency discontinuous current mode PWM circuits. The ZVT synchronous buck converter with new gate drive circuits is analyzed and the presented experimental results confirm the theoretical analysis.