Full-bridge LLC Resonant Converter Research Articles

Thermal Balance Modulation of Switching Devices for Hybrid-Clamped Three-Level Full-Bridge LLC Resonant Converter

Thermal Balance Modulation of Switching Devices for Hybrid-Clamped Three-Level Full-Bridge LLC Resonant Converter

An LLC resonant converter with wide output range fixed frequency PWM control for PEV charging applications

PurposeThis study aims to regarding the application of traditional pulse frequency modulation control full-bridge LLC resonant converters in wide output voltage fields such as on-board chargers, there are issues with wide frequency adjustment ranges and low conversion efficiency.Design/methodology/approachTo address these issues, this paper proposes a fixed-frequency pulse width modulation (PWM) control strategy for a full-bridge LLC resonant converter, which adjusts the gain by adjusting the duty cycle of the switches. In the full-bridge LLC converter, the two switches of the lower bridge arm are controlled by a fixed-frequency and fixed duty cycle, with their switching frequency equal to the resonant frequency, whereas the two switches of the upper bridge arm are controlled by a fixed-frequency PWM to adjust the output voltage. The operation modes of the converter are analyzed in detail, and a mathematical model of the converter is established. The gain characteristics of the converter under the fixed-frequency PWM control strategy are deeply analyzed, and the conditions for implementing zero-voltage switching (ZVS) soft switching in the converter are also analyzed in detail. The use of fixed-frequency PWM control simplifies the design of resonant parameters, and the fixed-frequency control is conducive to the design of magnetic components.FindingsAccording to the fixed-frequency PWM control strategy proposed in this paper, the correctness of the control strategy is verified through simulation and the development and testing of a 500-W experimental prototype. Test results show that the primary side switches of the converter achieve ZVS and the secondary side rectifier diodes achieve zero-current switching, effectively reducing the switching losses of the converter. In addition, the control strategy reduces the reactive circulating current of the converter, and the peak efficiency of the experimental prototype can reach 95.2%.Originality/valueThe feasibility of the fixed-frequency PWM control strategy was verified through experiments, which has significant implications for improving the efficiency of the converter and simplifying the design of resonant parameters and magnetic components in wide output voltage fields such as on-board chargers.

Hybrid Control Method of Full-Bridge LLC Resonant Converter Based on Electric Vehicle

Hybrid Control Method of Full-Bridge LLC Resonant Converter Based on Electric Vehicle

POWER SUPPLIES BASED FULL-BRIDGE LLC RESONANT CONVERTER PERFORMANCE FOR IH APPLICATIONS

This paper describes the analysis and performance of a full-bridge LLC resonant converter based on power supplies for IH applications. The analysis contains five components: half bridge inverter, resonant tank, high frequency transformer, rectifier and coil. The switching bridge generates a square waveform to excite the LLC resonant tank, which will produce a resonant sinusoidal current which is transferred to the secondary of the converter through a high-frequency transformer. As it scales the voltage up or down according to the output requirements. The load represented by the equivalent circuit of the coil and work-piece is fed by the current transformed by the rectifiers. Considering that load parameters and resonant frequency vary greatly in all phases of system operation, this paper provides improved knowledge of output power control for high temperature applications. The validity of the analyzed converter parameters had been simulated and tested using MATLAB-SIMULINK software. The results of testing demonstrated that the proposed scheme and assembly has good efficiency, and it is well suited for magnetic induction heating systems

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.

Research on Symmetrical Integrated Matrix Transformer Applied to Full-Bridge LLC Resonant Converter for CM Noise Cancellation

The planar transformer is widely used in DC-DC power converters due to the small leakage inductance and low height. However, the big overlapping area between primary and secondary windings in the planar transformer generates large parasitic capacitance, which brings serious common-mode (CM) noise problems. The full-bridge LLC resonant converter can meet the premise of CM noise cancellation since the noise sources on the primary and secondary sides have same magnitudes and opposite phases. Therefore, the symmetrical planar transformer design is more conducive to the attenuation of CM noise. This paper analyses symmetrical winding arrangements with minimal winding loss for the transformer in the full-bridge LLC resonant converter. Based on this, the symmetry of the reverse integrated matrix transformer (RIMT) and forward integrated matrix transformer (FIMT) composed of two elemental transformers is investigated. The scattering parameter <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> is used to evaluate the symmetry of RIMT and FIMT. It is found that the two CM <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> curves of RIMT are not consistent even though the windings have been arranged symmetrically. In contrast, the CM <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">21</sub> curves for FIMT are almost overlapped. This implies that FIMT is symmetrical and capable of CM current cancellation. Finally, the CM noises of the full-bridge LLC resonant converter using RIMT, RIMT with a balance capacitor, and FIMT are tested. Experimental results show that the CM noise for the converter using FIMT is lowest. Especially at the switching frequency, the CM noise is reduced by more than 20 dBμV.

Design of Magnetic Integrated LLC Transformer

The direct current/direct current (DC/DC) converter of the LLC (inductor-inductor-capacitor) converter is an important part of affecting the work efficiency, volume, and weight of the device. It not only has the functions of traditional transformers but is also able to solve the problems of traditional power transformers’ high price, huge volume, prodigious no-load loss, and inflexible control. This paper studies the DC/DC converter mainly, according to the given indexes, the magnetic integrated LLC resonant transformer is designed in detail. The magnetic integrated transformer greatly reduces the converter volume, and the selection of devices is completed based on parameters design. In addition, according to design parameters, losses and the efficiency of the LLC resonant transformer are calculated. The results meet the efficiency requirements. A test platform of a full-bridge LLC resonant converter is built according to theoretical research. The correctness and effectiveness of theoretical research and design methods of the DC/DC converter are verified by analyzing the experimental waveforms.

A Burst Mode and Variable Frequency Voltage Sharing Control Mechanism for an Adjustable High Voltage Pulsed Converter

This article presents a modular adjustable high-voltage pulse (MAHVP) generation system. The proposed MAHVP generation system uses a combination of full-bridge LLC resonant converters whose input terminals are connected in parallel and whose output terminals are in series to boost the output voltage; input parallel output series configuration efficiently increases the power holding capabilities of the overall system. The MAHVP generation system uses a novel burst mode and variable frequency voltage sharing (BMVFVS) control mechanism, the BMVFVS control mechanism senses the type of load if the MAHVP generation system needs to operate at a heavy load, it uses the variable frequency voltage sharing method to divide the power equally between the modules to enhance the overall performance. For light load conditions, the MAHVP generation system operates in burst mode, and the BMVFVS control mechanism combined with the frequency modulation technique is used to control the amplitude and pulsewidth of the output voltage smoothly and efficiently. A hardware prototype of 2.4 kW is developed, and experimental results are taken to verify the feasibility and validity of the proposed system, the maximum output voltage of the developed two-module prototype is tested up to 6 kV at the high efficiency of 97%.

A Novel Dead Time Design Method for Full-Bridge LLC Resonant Converters with SiC Semiconductors

As third-generation semiconductors become commercial, SiC semiconductors are gradually becoming more widely used in LLC resonant converters. The efficiency of the LLC resonant converter is improved by employing soft switching. However, when designing LLC resonant converters, semiconductors are usually regarded as ideal devices, and their turn-on and turn-off times are neglected. Furthermore, the method of designing the dead time relies on engineering experience and lacks precise theoretical foundations. In order to overcome the shortcomings of the current empirical method and to improve the generality and practicality of the dead time design method, a novel method for calculating the dead time of full-bridge LLC converters is proposed through theoretical research based on the operating principle of full-bridge LLC converters and the conditions for implementing soft switching. The method takes into account the switching characteristics of semiconductors and the on-state delay time of their body diodes, stray inductance, drive circuits, and errors arising from the first harmonic approximation (FHA) and improves the accuracy of the dead time calculation. It can implement good soft switching with full-bridge LLC converters, reduce switching losses, and improve system efficiency. Finally, the simulation experiment and the 2 kW experimental prototype are built to verify the effectiveness of the proposed method.

Research on Wide Input Voltage LLC Resonant Converter and Compound Control Strategy

This paper presents a wide input voltage vehicle DC/DC converter based on an LLC resonant converter for a 48 V light hybrid power system. According to the design requirements of on-board DC/DC converters and an analysis of their system characteristics, a full-bridge LLC resonant converter is employed with a zero-voltage activation of the switching transistors through resonant elements. In terms of the control strategy, the unsatisfactory high-frequency regulation gain of an LLC resonant converter is analyzed under the frequency modulation (FM) control strategy. In addition, to accommodate wide input voltage operating conditions, a composite control strategy is proposed by combining the advantages of the frequency modulation control strategy and phase shift control strategy, analyzing their control principles, and discussing the selection of the control mode switching point. By modeling LLC resonant converters with simulation software, the obtained results verify the effectiveness of the composite control strategy for LLC resonant converters. An experimental platform based on the TMS320F28335 controller, which can achieve stable operation with an input voltage in the range of 300 V–600 V and an output voltage of 48 V, is then built. The experimental results verify the feasibility of the design.

오프셋 전압 인가 방식의 펄스 크기 변조 풀브릿지 다이오드 클램프 3레벨 LLC 공진형 컨버터

In this paper, a full-bridge diode-clamped three-level LLC resonant converter with pulse-amplitude-modulation (PAM) suitable for a high-input voltage system has been studied. Unlike the existing frequency sweep converter, the proposed PAM method controls the output voltage by modulating the magnitude of fundamental component of leg voltage input to the resonance tank while fixing the operating frequency at the resonance point. In addition, the PWM switching pattern was easily implemented by applying an offset voltage while reducing the switching loss by using the ±180° discontinuous PWM (DPWM) technique. In this study, the control algorithm and operation characteristics were analyzed in detail, and the feasibility was confirmed through simulation.

Novel and simplified implementation of digital high-power pulsed MIG welding power supply with LLC resonant converter

PurposeThis paper aims to overcome the limitations of low efficiency, low power density and strong electromagnetic interference (EMI) of the existing pulsed melt inert gas (MIG) welding power supply. So a novel and simplified implementation of digital high-power pulsed MIG welding power supply with LLC resonant converter is proposed in this work.Design/methodology/approachA simple parallel full-bridge LLC resonant converter structure is used to design the digital power supply with high welding current, low arc voltage, high open-circuit voltage and a wide range of arc loads, by effectively exploiting the variable load and high-power applications of LLC resonant converter.FindingsThe efficiency of each converter can reach up to 92.3%, under the rated operating condition. Notably, with proposed scheme, a short-circuit current mutation of 300 A can stabilize at 60 A within 8 ms. Furthermore, the pulsed MIG welding test shows that a stable welding process with 280 A peak current can be realized and a well-formed weld bead can be obtained, thereby verifying the feasibility of LLC resonant converter for pulsed MIG welding power supply.Originality/valueThe high efficiency, high power density and weak EMI of LLC resonant converter are conducive to the further optimization of pulsed MIG welding power supply. Consequently, a high performance welding power supply is implemented by taking adequate advantages of LLC resonant converter, which can provide equipment support for exploring better pulsed MIG welding processes.

Research on Single-Phase and Three-Phase Compatible Isolated On-Board Charger and Control Technology

This paper presents a single-phase and three-phase compatible isolated on-board charger for electric vehicles. The charger is compatible with the single-phase and three-phase AC voltage input and is composed of two-stage circuits. Based on the three-phase six-switch power factor correction (PFC) circuit, by switching on and off, the front stage is transformed into a cascade topology of a totem-pole PFC circuit and boost circuit. The rear stage is a full-bridge LLC resonant converter. In the single-phase or three-phase working mode, the front-stage control strategy is a double closed-loop control. The current inner loop controller is improved for the three-phase six-switch PFC circuit. The PI controller and repetitive controller are connected in parallel to form the current inner loop compound controller, which can effectively reduce the total harmonic distortion of the input current. By using simulation software MATLAB/Simulink, the circuit model was built. The simulation results verify the correctness of the theoretical analysis.

Pulse-Amplitude-Modulation Full-Bridge Diode-Clamped Multilevel LLC Resonant Converter Using Multi-Neighboring Reference Vector Discontinuous PWM

A full-bridge diode-clamped multilevel LLC resonant converter suitable for power conversion systems that use high input voltage, such as railway vehicles, is proposed in this paper. In order to eliminate the voltage deviations of the capacitors connected in series to the high voltage input DC link, a novel modulation strategy referred to as multi-neighboring reference vector discontinuous pulse-width modulation (MNRV DPWM) is proposed. Unlike the existing two-level resonant converter that varies the operating frequency to hold the output voltage constant, the proposed multilevel resonant converter modulates the amplitude of the fundamental wave input to a resonance tank while fixing the operating frequency at the resonance point. Therefore, the design of passive elements becomes easier, and stable operation is possible over a wide operating range with only one power conversion stage. In this paper, the control algorithm and operation characteristics of the newly proposed full-bridge diode-clamped four-level LLC resonant converter are analyzed in detail and design guidelines are presented. The feasibility of the proposed converter is verified through a simulation and an experiment with a prototype converter.

State of the art and materials based characteristics in power converters for electric vehicles

The most prominent challenge in Electric Vehicles (EVs) is the method for charging the batteries, as well as the expanding appeal of power necessary due to the rapid demands for electric power demanded by EVs, Hybrid Electric Vehicles (HEVs), and Plug-in Hybrid Electric Vehicles (PHEVs). The converters used in electric car charging units have been subjected to a thorough and comprehensive examination. This article discusses the different seventeen power converters utilised in electric car charging modules in terms of their characteristics, performance criteria, benefits, drawbacks, circuit challenges, and cost. Additionally, it has been demonstrated that electric cars are far more economical than HEV and PEV due to their structure and operational mode simplicity. The usage of four converters, including Half Bridge LLC (HBLLC), Full Bridge LLC resonant converter (FBLLC), EF2 converter, and Full Bridge (FB) converters, is getting prominence between all these seventeen converters. This is owing to the fact that these converters have a higher efficiency factor and produce better results. As a result, a reasonable conclusion is that the FB LLC resonant converter is best suited for electric car charging modules.

GMAW power supply based on parallel full-bridge LLC resonant converter

ABSTRACT In order to reduce energy loss and improve the electrical energy conversion efficiency during the welding process and decrease electromagnetic interference (EMI) of the welding power supply, this paper introduces a gas metal arc welding (GMAW) power supply with an LLC resonant converter. The parallel full-bridge LLC resonant converter was selected according to the characteristics of GMAW, including high open-circuit voltage, low arc voltage, high welding current, and changeable arc load. Load simulation tests and welding tests were carried out using the proposed power supply. Results of load simulation tests show that the switching frequency has a significant effect on the power supply. When the load changes from a light load to the rated load, the shape of the primary-side resonant current gradually approaches the shape of a standard sine wave. Welding test results reveal that the proposed power supply achieves complete arc ignition. The stable working point of the welding process is within the efficient operating range of the LLC resonant converter. The weld bead produced in the welding test was well formed.

An Adaptive Synchronous Rectification Driving Strategy for Bidirectional Full-Bridge LLC Resonant Converter

In this study, an adaptive driving method for synchronous rectification in bidirectional full-bridge LLC resonant converters used in railway applications is proposed. The drain to source voltage of the synchronous rectifier is utilized to detect the conduction of the body diode, and a suitable driving signal for synchronous rectification is generated accordingly. The proposed driving scheme is simple and can be realized using a low-cost digital signal processor (DSP). According to the experimental results, which averaged 0.4625% and 1.097%, improvement can be observed under charging and discharging mode, respectively.

Analysis and Design of Three-Level Full-Bridge LLC Resonant Converter Based on Pulse Frequency Modulation

Aiming at the problem of serious switching loss in high-power and high-voltage occasions, the traditional LLC resonant network is difficult to adapt, the DC gain is difficult to obtain intuitively, and the voltage stress on the switch is too high, resulting in large switching losses and difficult selection of the switch. This paper uses a three-level full-bridge LLC resonant converter topology, the First Harmonic Approximation (FHA) is used to analyze the LLC resonant converter gain characteristics, and the parameter design ideas are given. A simulation experiment of a three-level full-bridge LLC resonant converter based on frequency modulation control is presented. The simulation results show that each primary side switch transistor can achieve zero voltage switching (ZVS), the secondary side diode realizes zero current switching (ZCS), and can obtain higher working efficiency, which verifies the feasibility of the design.

Thermally-Compensated Magnetic Core Loss Model for Time-Domain Simulations of Electrical Circuits

This article introduces a thermally-compensated magnetic hysteresis model, capable of accurately determining core losses of ferrite materials while accounting for core temperature variations. The employed model is based on permeance-capacitance analogy and it captures the frequency-independent hysteresis effect with the help of the Preisach model. For validation purposes, a 100 kW, 10 kHz realized medium frequency transformer prototype is selected and modeled as a part of a full-bridge LLC resonant converter in a time-domain simulation environment. Conducted simulations show the ability of the thermally-compensated magnetic hysteresis model to impact the generated core losses for core temperatures of up to 120 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C. Finally, a temperature-feedback loop within the transformer is successfully closed inside of a system-level simulation, allowing for a more precise determination of the core and winding steady-state temperatures.

Design and Implementation of a Full-Bridge LLC Converter With Wireless Power Transfer for Dual Mode Output Load

The proposed research is to accomplish a converter for driving DC load or AC load with wireless power transfer (WPT) technique. In this novel scheme, a full-bridge LLC resonant converter is adopted to deliver the energy from the primary to the secondary side. Besides, the LLC converter has soft-switching characteristic of the switches at the primary to improve the efficiency of the converter if the switching frequency is selected appropriately. In order to achieve the feature of wireless power transfer, the WPT (transmitting/receiving) coils are utilized to replace the transformer. The leakage inductor can be treated as a resonant inductor integrated in the transmitting coil. In the output side, a sinusoidal pulse width modulation (SPWM) technique is added to generate AC voltage for specific load. In other words, the proposed converter can output DC or AC voltage by user’s demand. In the end of this research, a LLC converter with WPT technique for 1kW is implemented. The experimental results and the related waveforms are also shown in the content. In this topology, the highest efficiency of DC output is 89.2%, and the highest efficiency of AC output is 82.6% respectively.