LLC Resonant Circuit Research Articles

High-Performance Light Emitting Diode Lighting Circuits and Their Interior Design Applications

This study explores the application of the half-bridge Inductor-Inductor-Capacitor (LLC) resonant converter in Light Emitting Diode (LED) lighting driver power supplies, with a specific focus on improving efficiency and dimming capabilities. The investigation begins with an analysis of the sliding mode control (SMC) method, utilizing a constant-current design with a fixed switching frequency (FWF). A novel fuzzy frequency-selective SMC dimming strategy is proposed to recognize the challenge of significant output voltage ripple during dimming under a FSF. To address the ripple issue during dimming, an electromagnetic filtering circuit is designed, and a zero-voltage turn-on Metal—Oxide—Semiconductor (MOS) tube is introduced, incorporating a synchronous rectification scheme to mitigate losses in the secondary-side rectification diode. The study comprehensively considers a current-mode self-driven method, specifically tailored to the LLC circuit’s different operating modes. The LLC resonant circuit, along with the subsequent synchronous rectification circuit, is meticulously designed for a 252 W LED driver power supply prototype. A closed-loop simulation circuit model is developed using PSIM software in experimental validation. The feasibility of SMC based on a FSF is affirmed through a comparative analysis of SMC signal waveforms, steady-state output current (OC) models, and resonant tank current waveforms. The investigation into the OC under various SMC conditions demonstrates the half-bridge LLC resonant converter’s ability to achieve stable output with minimal ripple. The designed LED lighting circuit is applied to indoor design, providing adjustable LED brightness and switch status at different power levels. Although obstacles slightly impact the communication quality of the circuit, it remains suitable for the majority of users’ needs.

Modelling a five‐level LLC resonant converter for bidirectional battery application

SummaryThis study designed and evaluated an integrated cascaded pair of full‐bridge LLC resonant bidirectional DC–DC converters usable in varied applications, including in energy storage systems, to function as an interface between two dc voltage buses in a variety of applications. The proposed converter combines an isolated five‐level cascaded H‐bridge LLC (IFCHB‐LLC) resonant circuit with a buck/boost circuit (bidirectional converter BID). In this converter, the inbuilt capabilities of an LLC converter, which function as a current source and a voltage source, were exploited, resulting in the constant current (CC) and constant voltage (CV) charges while CV was implemented in the discharge stage (reverse flow). The modelling of the LLC converter was done following the first harmonic approximation (FHA) approach. Furthermore, to ensure improved efficiency of the proposed system, the passive elements of the resonance tank and isolation transformer ratio were programmed in a manner that the converter can be operated within the zero‐voltage switching (ZVS) and zero‐current switching (ZCS) regions. The feasibility and validity of the converter were tested using a 500 W prototype converter with an input voltage of 200 V resulting in the highest efficiency level of 94.46%.

Modeling, Simulation and Digital Control of Full-Bridge LLC Resonant Converter

In order to demonstrate the performance of an LLC resonant converter with digital control, in this paper, we analyze the operating principles of the full-bridge LLC resonant converter. According to the operating characteristics of the full-bridge LLC resonant converter at different frequency bands, a simulation model was established using MATLAB Simulink software, and simulations were carried out. The digital control system of full-bridge LLC resonant converter was then designed based on the STM32 microcontroller. The simulation and experimental results demonstrated that the LLC resonant main circuit was always operating within the zero voltage switching (ZVS) state of the primary MOSFET and the zero current switching (ZCS) state of the secondary rectifier diode, while soft-switching was achieved in the full load range. The digital control of the full-bridge LLC resonant converter was ideally realized based on STM32. The input disturbance load test result validated the closed-loop concept of the proposed LLC resonant converter. The step response results in both simulation and load tests show that the power supply system has the desired dynamic response characteristics with low overshoot, short rise time and settling time, while the load step response results in both tests showed that the system has a strong anti-interference ability and robustness.

Analysis & Simulation of Different LLC Converter Topologies

There is an expanding trend in electric vehicle (EV) technologies because of finite fuel sourcesand environmental concerns. One of the essential barriers in EVs commercialization is the charging ofbatteries. The inductor-inductor-capacitor (LLC) resonant converter appears the most appealing design dueto its advantages, such as small electromagnetic interference, obtaining high-power density, ability to bedesigned at very high switching frequencies, operation for wide input and output voltage range with narrowswitching frequency variation, and high efficiency. This study compares different topologies of LLCresonant converter that can be adapted as battery charger of electric vehicle. The schematics of topologies,detailed design calculation of the parameters, simulation results of topologies to show the circuitperformance are presented, respectively. The simulation model is realized for whole examined topologieswith a proportional integral controller to obtain constant output voltage using MATLAB. LLC resonantcircuit is designed for the input voltage range of 305-345V, output voltage range of 36-58V, and outputpower of 700W. Analytical and simulation results are included in this study to illustrate the performancedifferences among the presented topologies of LLC resonant converter in terms of structure, efficiency, anddynamic response at sudden load changes.

Модель инвертора напряжения для анализа частотных характеристик

The purpose of this work is issues related to the design of the control circuit of the energy converter, where the developed model can be considered as a tool for research and analysis of frequency characteristics. The object of the study is a stabilized voltage source based on a bridge converter with an LLC-resonant circuit, designed for the needs of industrial equipment. The first part of the work look is devoted to constructing the Bode diagram of the transducer based on experimental data and comparing the obtained results with calculated curves. In the second half of the work, a computer model of a closed control loop is presented.

Insulation improvement scheme of multi-output solid-state-transformer for photovoltaic grid-connected circuit

Solid-state-transformer (SST) with small volume and lightweight has been widely used in renewable energy grid connection. The electric field analysis of the transformer provides accurate insulation design and has significant engineering application value. By analysing the electric field between the adjacent windings of multi-winding transformer, it is determined that the pie winding structure should be selected for single winding and the design of even layers. In combination with the requirements of an LLC resonant circuit for magnetic transformer integration, a shielding ring is set on the plane where the insulating medium intersects the iron core to increase the leakage inductance of the transformer and eliminate the tip effect on the edges and corners of the iron core.

Design and Simulation of LLC Resonant Converter for Hydrogen Production Based on Proton Exchange Membrane Electrolysis

This paper studies the relationship between the parameters in LLC resonant circuit based on the fundamental wave analysis method, analyzes the gain curve and the soft-switching conditions of the power tube, gives the selection method of the parameters k and Q and calculates the resonant component parameters. In this paper, a closed-loop frequency modulation control method is used to control the DC output voltage of the resonant converter. At the same time, mathematical modeling and analysis are carried out for the electrochemical model and thermal model of the proton exchange membrane (PEM) hydrogen production electrolyzer, and the Simulink simulation tool is used to complete the joint simulation of the PEM electrolysis model and the LLC resonant converter. The simulation results fully reflect the actual control process.

Применение метода расширенных функций описания при проектировании контура управления источником питания

The article is devoted to issues related to the design of a control loop of an energy converter, where the method of extended description functions is used as a tool for research and analysis of frequency characteristics. The object of research is a stabilized voltage source based on a bridge converter with an LLC-resonant circuit, designed for the needs of industrial equipment. Within the framework of this work, a single-loop feedback with stabilization of the output voltage level is considered. Based on the calculations, the voltage source circuit was simulated in the LTSpice circuit simulation environment.

LLC Inverter Design Procedure for Induction Heating with Quantitative Analysis of Power Transfer

The paper explains the operating principle of an LLC resonant circuit for induction heating applications. Although induction heating has attracted a great deal of attention in recent years, very little consideration on designing the inductor in the resonant circuit for specific requirements has been done. Specifically, a design procedure with the required power and work-head dimension as inputs is still needed, from a practical point of view. In this paper, a quantitative analysis of power transferred to the work-head will be done to help design the resonant circuit. A design procedure for the LLC circuit will be proposed, utilizing results from the quantitative power analysis and taking into account mechanical constraints on the work-head. In addition, a simple technique to monitor the soft switching condition of the power switches in the resonant inverter, utilizing only voltage signals, is also proposed. The feasibility of the proposed design procedure will be demonstrated and verified by simulations and experiments.

Analysis of a Series‑Parallel Resonant Converter for DC Microgrid Applications

An input-series output-parallel soft switching resonant circuit with balance input voltage and primary-side current is studied and implemented for direct current (DC) microgrid system applications. Two resonant circuits are connected with input-series and output-parallel structure to have the advantages of low voltage stresses on active devices and low current stresses on power diodes. A balance capacitor is adopted on high voltage side to balance two input capacitor voltages. The LLC (inductor–inductor–capacitor) resonant circuit cells are employed in the converter to have soft switching operation for power semiconductors. The magnetic coupling component is adopted on the primary-side to automatically realize current balance of the two resonant circuits. In the end, a laboratory hardware circuit is built and tested. Experiments demonstrate and prove the validity of the resonant converter.

A Single-Stage High Power Factor Power Supply for Providing an LED Street-Light Lamp Featuring Soft-Switching and Bluetooth Wireless Dimming Capability

Light-emitting diode (LED) has the characteristics of environmental protection and energy saving, having become the lighting source of a new generation of street-light lamps. The traditional two-stage power supply for providing an LED street-light lamp is composed of an AC-DC converter with a power-factor-correction (PFC) function at the front stage and a DC-DC converter at the rear stage. The two-stage power supply for an LED street-light lamp has a large number of electronic components and costs, and the circuit efficiency is not high. Therefore, this paper presents a novel single-stage high power factor AC-DC power supply for providing an LED street-light lamp featuring soft-switching and Bluetooth wireless dimming capability through using smart tablets or smartphones to remote control the output power of the LED street-light lamp for achieving energy-saving benefits. The proposed AC-DC LED power supply integrates an interleaved buck converter circuit with coupled inductors and a half-bridge LLC resonant converter circuit into a single-stage power conversion circuit. Moreover, the coupled inductor of the interleaved buck converter circuit is designed to operate in the discontinuous conduction mode, which can naturally achieve PFC. In addition, the two power switches in the novel LED power supply have zero-voltage switching (ZVS) characteristics, which can reduce the switching losses of the power switches. The two output diodes have the characteristics of zero-current switching (ZCS), which can reduce the conduction losses of the power diodes. This paper developed a single-stage prototype circuit for providing an 144 W (36 V/4 A)-rated LED street-light lamp. According to the experimental results of the prototype circuit with an AC input voltage of 110 volts, the presented single-stage LED power supply offers high power factor (PF > 0.99), low input-current total harmonic distortion factor (THD < 3%), and high efficiency (>89%). In addition, this paper used the built-in Bluetooth wireless communication function of a smart tablet or smart phone to fulfill remote dimming control. By changing the duty ratio of the control signal, we could realize remote dimming control of 20% to 100% of the output LED street-light lamp power.

Analysis of a Three-Level Bidirectional ZVS Resonant Converter

A bidirectional three-level soft switching circuit topology is proposed and implemented for medium voltage applications such as 750 V dc light rail transit, high power converters, or dc microgrid systems. The studied converter is constructed with a three-level diode-clamp circuit topology with the advantage of low voltage rating on the high-voltage side and a full-bridge circuit topology with the advantage of a low current rating on the low-voltage side. Under the forward power flow operation, the three-level converter is operated to regulate load voltage. Under the reverse power flow operation, the full-bridge circuit is operated to control high-side voltage. The proposed LLC resonant circuit is adopted to achieve bidirectional power operation and zero-voltage switching (ZVS). The achievability of the studied bidirectional ZVS converter is established from the experiments.

Design and implementation of high frequency induction heating with LLC resonant load matching using ELTA

Induction heating is a non-contact method of producing heat which can be used to perform various processes like hardening, annealing, tempering, welding, brazing, melting, forging, etc. This paper discusses the design and implementation of induction heating on a given work-piece, using an LLC resonant circuit and a transformer for impedance matching, so as to transfer a maximum power of 5KW to the load. The load parameters are found out using ELTA software which calculates the values based on the dimensions of the work piece, operating frequency and temperature. The inverter used is based on SiC MOSFETs which minimizes the losses at high frequencies and high temperatures. The theoretical and simulated results from MATLAB are analysed and verified. The hardware is implemented for the LLC circuit with transformer and the results are presented.

A Novel LLC Resonant Converter Circuit-Input Parallel Output Series Subside Resonant LLC Resonant Converter

At present, LLC resonant converters are mostly used in step-down situations. The reason why LLC resonant converters are not used in high step-up situations is that parasitic parameters caused by high turn-to-turn ratio of transformers affect the circuit and the large current stress of switching devices and resonant components on the input side. In this paper, a new type of LLC resonant converter circuit, i.e. input parallel output series subside resonant LLC resonant converter, is designed. It can not only reduce the current stress borne by the switching devices on the input side and the resonant components, but also reduce the turn-to-turn ratio of the transformer under the same output voltage. Therefore, it can be used in boost occasion to output high voltage. In this paper, a new type of circuit is used in high boost situation, and the final output is stable 2KV high voltage.

Zero-Voltage-Switching PWM Resonant Full-Bridge Converter With Minimized Circulating Losses and Minimal Voltage Stresses of Bridge Rectifiers for Electric Vehicle Battery Chargers

This paper presents a zero-voltage-switching (ZVS) full-bridge dc-dc converter combing resonant and pulse-width-modulation (PWM) power conversions for electric vehicle battery chargers. In the proposed converter, a half-bridge LLC resonant circuit shares the lagging leg with a phase-shift full-bridge (PSFB) dc-dc circuit to guarantee ZVS of the lagging-leg switches from zero to full load. A secondary-side hybrid-switching circuit, which is formed by the leakage inductance, output inductor of the PSFB dc-dc circuit, a small additional resonant capacitor, and two additional diodes, is integrated at the secondary side of the PSFB dc-dc circuit. With the clamp path of a hybrid-switching circuit, the voltage overshoots that arise during the turn off of the rectifier diodes are eliminated and the voltage of bridge rectifier is clamped to the minimal achievable value, which is equal to secondary-reflected input voltage of the transformer. The sum of the output voltage of LLC resonant circuit and the resonant capacitor voltage of the hybrid-switching circuit is applied between the bridge rectifier and the output inductor of the PSFB dc-dc circuit during the freewheeling phases. As a result, the primary-side circulating current of the PSFB dc-dc circuit is instantly reset to zero, achieving minimized circulating losses. The effectiveness of the proposed converter was experimentally verified using a 4-kW prototype circuit. The experimental results show 98.6% peak efficiency and high efficiency over wide load and output voltage ranges.

Performance prediction of third-order series resonant convertor

The steady-state analysis of a modified resonant series DC/DC power convertor with an LLC resonant circuit operating under frequency control in the continuous-conduction mode is considered. A describing function and harmonic balance techniques are applied to the power convertor large-signal nonlinear equations to obtain steady-state equations. The input and output rectifiers and output transformer are also included in the analysis. Steady-state calculations compare fairly well with experimental results.