Full-bridge Resonant Converter Research Articles

РОЗРАХУНОК РЕГУЛЮВАЛЬНИХ ХАРАКТЕРИСТИК РЕЗОНАНСНИХ ПЕРЕТВОРЮВАЧІВ МЕТОДОМ СУПЕРПОЗИЦІЇ

The work presents the calculations of the control characteristics of the full-bridge resonant converter with a series resonant LLC circuit and frequency control by two methods - the first harmonic method and the superposition method. The theoretical results were verified by the analytical-structural modeling method. The power circuit of the resonant converter for the analysis of electromagnetic processes is replaced by a linear T-shaped circuit with two series resonant RLC-circuits and equivalent generators of rectangular voltages, which simulate a transistor inverter and a diode rectifier in the quasi-continuous current mode. Analytical-structural modeling method consists in partly analytical and partly structural ways of building a numerical model of the resonant converter in the form of the simulation model in the MATLAB-Simulink environment. Linear structural links of the model are created on the basis of integral equations of circles. Non-linear links are created based on the non-linear functions and causal relationships. The structural model based on these links takes into account the nonlinearity of the elements of the power circuit of the resonant converter and is based on simpler mathematical expressions compared to the equivalent mathematical model of the resonant converter. The structural model corresponds to the idea of the resonant converter in the form of the resonant circuit with independent equivalent voltage generators and allows to adjust the magnetic coupling coefficient between the transformer windings and simulate processes with arbitrary control functions of equivalent generators. The peculiarity of the use of the superposition method for calculating the static characteristics of the resonant converter is the need to match the voltage phases of the equivalent generators of the equivalent circuit during the changes of the operating frequency or relative load voltage. The dependence of the input voltage of the rectifier, which is simulated by the second equivalent generator, on the processes of the power circuit of the real resonant converter, determines the conditions for matching (adjusting) the phases of the equivalent generators. References 30, figures 5.

ДИНАМІЧНА МОДЕЛЬ РЕЗОНАНСНОГО ПЕРЕТВОРЮВАЧА ДЛЯ ВПЛИВУ ЗІ СТОРОНИ ЖИВЛЕННЯ

In the paper, a discrete dynamic model of a full-bridge resonant converter with a symmetrical operating mode has been obtained, which describes the resonant converter as a transfer link with an supply voltage input side and a load current output side. The dynamic model is based on a linear mathematical model of the resonant converter built according to the superposition principle. The structure of the resonant converter with the processes outline function is given and analyzed. The structure of the discrete dynamic model of the resonant converter of the nth order is presented. It is proved that the transfer function of the discrete dynamic model for the outline function can be determined by the transfer function of the continuous system. The resulting dependencies describing the discrete transfer functions of the resonant converter are used to obtain the discrete dynamic model of the double-circuit transformer resonant converter in a synchronous rectifier. For this, the sequence of actions is defined: definition of the transfer function of the continuous dynamic model; obtaining the system of equations in vector-matrix form describing electromagnetic processes in the converter; definition of the system of discrete equations; definition of the transfer function of the circuit. The obtained theoretical results were verified by means of simulation modeling of the considered double-circuit resonant converter. The proposed dynamic model makes it possible to analyze the influence of instability and low-frequency fluctuations of the supply voltage of the resonant converter on the output values. The presented results can be used in the development and improvement of single- or multi-circuit bridge high-frequency resonant converters as the secondary power sources and converters used in ship demagnetization systems. References 25, figures 8, tables 2.

Maximum Efficiency Point Tracking Algorithm for Resonant Full-Bridge Converter in Charging Applications

In this paper, a novel maximum efficiency point tracking algorithm is proposed for a resonant DC-DC power converter in charging applications. Based on a total harmonic analysis (THA), a method for minimizing the harmonic content of the input AC current is investigated. An online algorithm is proposed for achieving the maximum efficiency at the whole charging spectrum, by controlling the angle under which zero-voltage switching occurs. The suggested control algorithm is simple to implement with very low computational complexity. Additionally, an effective winding method is proposed for increasing the leakage inductance without greatly increasing the air gap, thus eliminating the need for additional resonant inductors. A prototype converter of 2kW|20A is implemented for verifying the proposed method and 98% maximum efficiency is achieved.

A Simple Optimal Trajectory and Thermal Balance Control Strategy for Full-Bridge Resonant Converter With Wide Voltage Range Application

A Simple Optimal Trajectory and Thermal Balance Control Strategy for Full-Bridge Resonant Converter With Wide Voltage Range Application<i />

Modified Two-Channel LLC Resonant Converter With Optimal Efficiency for Wide Input Voltage Applications

A modified two-channel LLC resonant converter with optimal efficiency for wide input voltage applications. The converter has the same voltage gain and power handing ability as conventional full-bridge (FB) resonant converter, but the hardware cost is lower than conventional FB resonant converter, and the operational frequency range is narrower than conventional resonant converter for the same working condition. It has the characteristics of low input impedance at low input voltage, which is used to provide high voltage gain, and high input impedance at high input voltage, which is used to provide low voltage gain, the above characteristics are analyzed and optimized to improve the efficiency for photovoltaic applications where wide voltage gain is require. A 1 kW prototype is developed, the input voltage ranges from 80 V to 200 V, the output voltage and output power are 400 V and 1 kW, the experimental result shows that the full-load efficiency can reach 96.5% over the entire input voltage range, and the peak efficiency can reach 96.9% at full-load state.

Parasitic Parameter Extraction and Identification Method for HFT Based on DC-DC Converter in EV Application

Dual active bridge (DAB) resonant converter is one of the most commonly used soft switched converters of the new electric vehicle (EV) energy system. One of the most essential parts of the DAB resonant converter, the high-frequency transformer (HFT) includes certain parasitic parameters that caused voltage and current oscillation, or ring to the DAB converter. These precise parasitic parameters of the HFT provide accurate information and are useful to the DAB converter control system design. However, they are not provided by the manufacturer. This study focuses on this prospect of information, proposing a novel parasitic parameter identification method for the HFT based on DAB converter. Moreover, a 40 kHz full-bridge resonant DAB converter prototype based on SiC MOSFETs and HFPT laboratory prototype is constructed to verify the effectiveness and feasibility of the proposed method. Simulation and experimental results verify that the proposed method is more cost-effective than the conventional way to measure via impedance (IMDP) analyzer, requires shorter simulation time than the traditional finite element analysis (FEA) method, while it is also more accurate has fast convergence than the traditional forgetting factor recursive least square (FFRLS) identification algorithm.

Characteristics Analysis and Design of a Resonant dc–dc Converter With ZCS and Short-Circuit Fault Current Limiting Capability

The series resonant dc-dc converter (SRC) which features zero current switching (ZCS) and open-loop control is widely used for providing galvanic isolation and voltage scaling. However, output short-circuit (OSC) fault is a challenge for SRC because it will cause dramatically high current in the low-impedance resonant tank. To address this issue, a resonant full-bridge dc-dc converter only using small dc-side capacitors to resonate with the resonant inductor Lr is proposed. Under normal condition, ZCS can be achieved. When OSC fault occurs, the output dc-side capacitor can be bypassed by the anti-paralleled diodes of the full bridge and the resonant current can be limited automatically by the resonant inductor Lr without additional control. The operation principle of the converter under normal and faulty condition is analyzed. Based on these analyses, the switching frequency to achieve ZCS is designed. The resonant inductor Lr and dc-side resonant capacitors Cr design considerations are provided. The ZCS characteristics and the current limiting capability of the converter are verified on an experimental prototype.

Design of a Bidirectional CL3C Full-Bridge Resonant Converter for Battery Energy Storage Systems

In this study, a bidirectional CL3C full-bridge resonant converter was developed using a bidirectional active bridge converter as the main framework to improve conventional LLC resonant converters. A resonant inductor and resonant capacitor were installed at the secondary side of the developed resonant converter. The bidirectional operation of this converter enables zero-voltage switching at the supply-side power switch and zero-current switching at the load side. The aforementioned phenomena enhance the overall circuit efficiency and enable the resonant tank voltage to be increased in the reverse mode, which cannot be achieved with conventional bidirectional LLC resonant converters. The electrical equipment isolation function provided by a transformer made electricity usage safer, and digital control technology was adopted to control electrical energy conversion and simulate bidirectional energy conversion. Specifically, the experiment and simulation emulated how the developed converter enables energy transmission from a DC grid to a battery energy storage system through constant current–constant voltage charging and energy transmission from a battery energy storage system to a DC grid through constant power discharging.

Full-bridge resonant converter with hybrid control for wide input voltage range applications

This paper proposes a hybrid control strategy for a full-bridge resonant converter. In the applications with a wide input voltage, a resonant converter with variable frequency control (VFC) has to modulate the converter operating in a wide switching frequency range to satisfy gain requirements, which results in some problems such as difficulty in optimizing the design of magnetic components, increased power loss and deteriorated electromagnetic interference. By use of VFC, primary-side phase shift control and secondary-side phase shift control, the frequency variable range can be greatly reduced and the conversion efficiency can be increased, which make the converter appropriate for a wide input voltage range. With this hybrid control strategy, the converter can automatically convert to the corresponding control mode according to variations of the input voltage and load, which has a good transient performance. The working principle, gain characteristics and design considerations of a hybrid controlled CLL resonant converter are introduced in detail. Experimental results are shown to demonstrate its validity and feasibility.

Resonant Converter with Soft Switching and Wide Voltage Operation

A new DC/DC resonant converter with wide output voltage range operation is presented and studied to have the benefits of low switching losses on active devices and low voltage stresses on power diodes. To overcome serious reverse recovery losses of power diodes on a conventional full-bridge pulse-width modulation converter, the resonant converter is adopted to reduce the switching loss and increase the circuit efficiency. To extend the output voltage range in conventional half-bridge or full-bridge resonant converters, the secondary sides of two diode rectifiers are connected in series to have wide output voltage operation. The proposed converter can be either operated at one-resonant-converter mode for low voltage range or two-resonant-converter mode for high voltage range. Thus, the voltage rating of power diodes is decreased. Experiments with the design example are given to show the circuit performance and validate the theoretical discussion and analysis.

Design and Realization of Current-Fed Single-Input Dual-Output Soft-Switched Resonant Converter

This paper proposes a new single-input dual-output [SIDO] soft-switched resonant full-bridge converter, which has asymmetrical structures for the isolated multiple outputs. The proposed structure is capable of supplying different loads having dissimilar voltage-current characteristics and independent of each other. This converter features wide range of zero current switching (ZCS) turn-off and automatic load-voltage regulation. In automatic load-voltage regulation, converter maintains constant voltage without the need of change in frequency or duty ratio during load change. First, the modes of converter operation are explained and then design of key parameters have been outlined. A laboratory prototype for 380[Formula: see text]V, 500[Formula: see text]W as main output and 24[Formula: see text]V, 50[Formula: see text]W as auxiliary output for an input voltage range of 40–50[Formula: see text]V was built-up and tested. Experimental results confirm the viability of voltage regulation, ZCS and power efficiency of the proposed converter.

Series-Series/Series Compensated Inductive Power Transmission System with Symmetrical Half-Bridge Resonant Converter: Design, Analysis, and Experimental Assessment

In order to compensate the large leakage inductance and improve the power transmission capacity, capacitors are widely used in inductive power transfer (IPT) systems, which results in high voltage or current stresses in the resonant tanks and limits higher volt-ampere (VA) rating of the transfer power, especially in medium and low frequency applications. This paper presents a symmetrical half-bridge resonant converter (SHRC) for series-series/series compensated IPT systems with detailed analysis and design. It operates at a relatively low frequency of 12.5 kHz, suitable for IGBT applications. The theoretical analysis shows that, compared with full-bridge resonant converter (FRC) for IPT, the symmetrical half-bridge resonant converter achieves a higher efficiency. Simulation and a prototype of 1500 W power output were built to verify the theoretical analysis. The experimental results show that the power loss of SHRC is 39.7 W while that of FRC is 79.4 W, which is consistent with the theoretical analysis. The global efficiency of the IPT based on the proposed converter is 91.6%.

LLC Resonant Converter for LEV (Light Electric Vehicle) Fast Chargers

This paper presents a Light Electric Vehicle (LEV) fast charger with a Lithium-Ion Battery (LIB) and Super-Capacitor (SC). The LEV fast charger consists of an AC/DC rectifier and LLC (Inductor-Inductor-Capacitor) resonant Full bridge converter. The LLC resonant converter has high-efficiency and low switching loss because of Zero Voltage Switching (ZVS). So, it is used widely in the industry. In general, the fast charger algorithm uses the Constant Current (CC) mode and Constant Voltage (CV). The CC mode starts at first and then the CV mode finishes. However, there is a big control value gap between the CC mode and CV mode. Therefore, when changing from CC to CV, the transient state occurs. To compensate for the transient state, we propose a new control algorithm. By means of this algorithm, we can achieve a higher level of safety and stability. The fast charger with LIB of 800 Wh and SC of 50 Wh is analyzed and verified, and we obtain a maximum efficiency of 96.4%. The discussions are validated using the LLC resonant full bridge converter prototype at the laboratory level.

Design and analysis of a full bridge LLC DC-DC converter for auxiliary power supplies in traction

This paper focuses on an 8 kW LLC resonant full bridge DC-DC converter topology using a high frequency transformer for auxiliary power supply systems in traction. The full bridge DC-DC converter with the LLC resonant network has been tested under hard switching and zero current switching conditions with 100 kHz switching frequency. In addition to this, an observation made for the effect of dead time variation of the power switches to improve the overall system efficiency. This paper describes the efficiency of the ZCS full bridge converter by considering different input power levels and also compared with hard switched topology. This paper presents the operating principles, simulation analysis, and experimental verification for 3 kW to 8 kW LLC resonant full bridge converter with 1200 V/40 A IGBTs, and its efficiency comparison.

The Steady-State DC Gain Loss Model, Efficiency Model, and the Design Guidelines for High-Power, High-Gain, Low-Input Voltage DC–DC Converter

The phase modulated full bridge resonant transition converter (PMRTC) is commonly used for high-gain, high-power applications, as PMRTC converters retain the qualitative nature of hard switched pulse-width modulation counterparts with additional damping ( $R_d$ ), where $R_d$ is load, transformer turns ratio and frequency dependent. The PMRTC converter enables operation at a higher switching frequency due to the soft-switching nature, thereby achieving better power density. For battery fed high-power, high-gain applications, PMRTC exhibits a significant drop in the dc gain due to $R_d$ and other nonidealities, limiting the maximum frequency of operation. Thus, computing this drop and analyzing the effects of switching frequency becomes necessary in achieving the required steady-state dc gain. From the analysis, it is observed that, for a choice of switching frequency above $f_{s\;{\rm critical}}$ , the required steady-state dc gain is not achieved for any turns ratio. Hence, to increase the switching frequency of operation of a PMRTC converter, a two-transformer configuration is adapted and with this configuration, the dc gain loss model, power loss, and efficiency model and small-signal model are established. The design guidelines on the choice of switching frequency and transformer turns ratio based on the proposed models is described. The proposed models with the presented design guidelines are validated in simulations and hardware prototype for a 1 kW PMRTC converter.

Operation Modes of a Secondary-Side Phase-Shifted Resonant Converter

In this work, a unidirectional full-bridge resonant converter with secondary-side phase-shifted control is addressed. With the variation of voltage gain and power level, this converter may enter into different operational modes, including three continuous current modes and one discontinuous current mode. The details in each operation mode are discussed one by one. The boundary conditions between these modes have been identified. Additionally, the steady-state analysis of all continuous current modes is performed uniformly by using the fundamental harmonics approximation approach. Experimental results based on a lab prototype converter are also included to verify the operation modes predicted by the theoretical analysis.

Power Factor Corrected Single Stage AC-DC Full Bridge Resonant Converter

Power Factor Corrected Single Stage AC-DC Full Bridge Resonant Converter

可変誘導性リアクタンス機能を持つ5エレメント多重共振形DC-DCコンバータ

A five element multiplex resonant (LLCLC) full-bridge DC-DC converter controlled by pulse-frequency-modulation (PFM) is proposed in this paper. The high frequency (HF)-link resonant DC-DC converter proposed herein can perform wide-range output power and voltage regulations with a narrow frequency range owing to an anti-resonant tank which works effectively as a wide-range variable inductor. The advantageous characteristics of the anti-resonant tank provide overcurrent protection in the case of the short-circuited load condition as well as the start-up interval, thus the technical challenges of the conventional LLC DC-DC converter can be overcome, and the reliability of the relevant switch-mode power supplies can be improved. The operating principle of the LLCLC DC-DC converter is described, after which its performance is evaluated in an experimental setup based on the 2.5kW prototype. Finally, the feasibility of the proposed DC-DC converter is discussed from the practical point of view.

넓은 충전 범위를 갖는 전기 자동차용 급속 충전기의 고효율 운전을 위한 손실 분석

Power losses of a 1-stage DC-DC converter and 2-stage DC-DC converter are compared in this paper. A phase-shift full-bridge DC-DC converter is considered as 1-stage topology. This topology has disadvantages in the stress of rectifier diodes because of the resonance between the leakage inductor of the transformer and the junction capacitor of the rectifier diode. 2-stage topology is composed of an LLC resonant full-bridge DC-DC converter and buck converter. The LLC resonant full-bridge DC-DC converter does not need an RC snubber circuit of the rectifier diode. However, there is the drawback that the switching loss of the buck converter is large due to the hard switching operation. To reduce the switching loss of the buck converter, SiC MOSFET is used. This paper analyzes and compares power losses of two topologies considering temperature condition. The validity of the power loss analysis and calculation is verified by a PSIM simulation model.

Design and Implementation of a Dimmable LED Driver with Low-Frequency PWM Control

This paper proposes a high-efficiency dimmable LED driver for light emitting diodes (LED). The developed LED driver consists of a full-bridge resonant converter and six buck converters. The function of the full-bridge resonant converter is to obtain a smooth dc-link voltage for the buck converters by phase-shift modulation (PSM) while that of the six buck converters is to drive six LED modules, respectively. The gate voltage of the active switch of each buck converter is a combination of high-frequency and low-frequency pulses. The duty ratio of the high-frequency pulse controls the LED voltage and thereby, controls the amplitude of LED current. LEDs are dimmed by low-frequency pulse-width modulation (PWM) to vary the average current flowing through LED. Circuit equations are derived and circuit parameters are designed. High circuit efficiency is ensured by operating the active switches at zero-voltage switching-on to reduce the switching loss. Finally, a prototype circuit was built to verify the accuracy and feasibility of the proposed LED driver.