Search Results (135)

The LLC resonant converter, as an isolated DC-DC conversion topology, has been widely adopted in industrial applications. However, when operating under wide input/output voltage ranges, a broad switching frequency range is required to achieve the desired voltage gain. This wide frequency variation complicates the design of magnetic components, causes loss of soft-switching characteristics, and deteriorates electromagnetic interference (EMI) performance. To address these challenges, this paper presents a detailed analysis of the L-LCLC resonant converter. By controlling the connection/disconnection of additional inductors and capacitors through switching devices, the topology achieves structural reconfiguration to enhance the voltage gain range. Optimal mode transition points are selected to ensure stable operation during mode transitions, thereby reducing design complexity, minimizing transition losses, and suppressing voltage/current stress. The parameter design methodology for the additional reactive components is systematically developed. The converter’s performance is validated with Simulink, and the experimental prototype is established with 100 W. Both simulation and experimental results confirm that the L-LCLC resonant converter achieves a wide voltage gain range within a narrow frequency band while maintaining stable mode transitions. Full article

Background: Cancer vaccines represent a groundbreaking advancement in cancer immunotherapy, utilizing tumor antigens to induce tumor-specific immune responses. However, challenges like tumor-induced immune resistance and technical barriers limit the widespread application of predefined antigen vaccines. Here, we investigated the potential of viral protein R (Vpr) peptides as effective candidates for constructing anonymous antigen vaccines in situ by directly injecting at the tumor site and releasing whole-tumor antigens, inducing robust anti-tumor immune responses to overcome the limitations of predefined antigen vaccines. Methods: The cytotoxic effects of Vpr peptides were evaluated using the CCK8 reagent kit. Membrane penetration ability of Vpr peptides was observed using a confocal laser scanning microscope and quantitatively analyzed using flow cytometry. EGFR levels in the cell culture supernatants of cells treated with Vpr peptides were evaluated using an ELISA. Surface exposure of CRT on the tumor cell surface was observed using a confocal laser scanning microscope and quantitatively analyzed using flow cytometry. The secretion levels of ATP from tumor cells were evaluated using an ATP assay kit. HMGB1 release was evaluated using an ELISA. Mouse (Male C57BL/6 mice aged 4 weeks) MC38 and LLC bilateral subcutaneous tumor models were established to evaluate the therapeutic effects of Vpr peptides through in situ vaccination. Proteomic analysis was performed to explore the mechanism of anti-tumor activity of Vpr peptides. Results: Four Vpr peptides were designed and synthesized, with P1 and P4 exhibiting cytotoxic effects on tumor cells, inducing apoptosis and immunogenic cell death. In mouse tumor models, in situ vaccination with Vpr peptide significantly inhibited tumor growth and activated various immune cells. High-dose P1 monotherapy demonstrated potent anti-tumor effects, activating DCs, T cells, and macrophages. Combining ISV of P1 with a CD47 inhibitor SIRPαFc fusion protein showed potent distant tumor suppression effects. Proteomic analysis suggested that Vpr peptides exerted anti-tumor effects by disrupting tumor cell morphology, movement, and adhesion, and promoting immune cell infiltration. Conclusions: The designed Vpr peptides show promise as candidates for in situ vaccination, with significant anti-tumor effects, immune activation, and favorable safety profiles observed in mouse models. In situ vaccination with Vpr-derived peptides represents a potential approach for cancer immunotherapy. Full article

This article proposes a high-efficiency isolated three-port resonant converter for DC microgrids, combining a dual active bridge (DAB)–LLC topology with hybrid Pulse Width Modulat-Pulse Frequency Modulation (PWM-PFM) phase shift control. Specifically, the integration of a dual active bridge and LLC resonant structure with interleaved buck/boost stages eliminates cascaded conversion losses. Energy flows bidirectionally between ports via zero-voltage switching, achieving a 97.2% efficiency across 150–300 V input ranges, which is a 15% improvement over conventional cascaded designs. Also, an improved PWM-PFM shift control scheme dynamically allocates power between ports without altering switching frequency. By decoupling power regulation and leveraging resonant tank optimization, this strategy reduces control complexity while maintaining a ±2.5% voltage ripple under 20% load transients. Additionally, a switch-controlled capacitor network and frequency tuning enable resonant parameter adjustment, achieving a 1:2 voltage gain range without auxiliary circuits. It reduces cost penalties compared to dual-transformer solutions, making the topology viable for heterogeneous DC microgrids. Based on a detailed theoretical analysis, simulation and experimental results verify the effectiveness of the proposed concept. Full article

A prototype of an industrial installation for the deposition of self-restoring nitride coatings on the surface of reed switch contacts using electro-spark erosion alloying was developed, manufactured, and tested under the laboratory conditions at LLC Nitron. It was shown that the coatings are formed inside a bulb of reed switches at the final stage of their production following the impact from the spark breakdown between the contacts, stimulated via alternating magnetic and electric fields. The nitrogen concentration in the surface layers of the nitride coatings, estimated by means of X-ray microanalysis, was ca. 19 at. % and their thickness, measured by time-of-flight secondary ion mass spectrometry via sputter depth profiling, ranged between 250 and 350 nm. The novelty of the presented work consists of the development of an innovative piece of equipment, the operating principle and design of which are protected by intellectual property rights (four Russian patents). The technological approach implemented in this installation differs from the industrial galvanic technology due to its high level of environmental safety and economic efficiency, since it does not require the use of gold, ruthenium, or other high-priced metals. Full article

This paper proposes a half-bridge parallel dual LLC resonant converter with wide output voltage range. The proposed converter uses a conventional parallel double half-bridge LLC resonant converter. On the primary side of the converter, only one of the two half bridges is used to control the two resonant loops. Due to the resonance of the converter, the active switches can achieve ZVS (zero-voltage switching), and the rectifier diode can also achieve ZCS (zero-current switching), and thus the switching loss is reduced. The current stress can be reduced and power can be distributed on both of the primary side and/or the secondary side. A voltage regulation circuit is designed on the secondary side to achieve the function of wide output voltage. The operation and analysis of the proposed converter are described in detail. The experiments were carried out on a circuit prototype, which is a converter with DC input voltage of 384 V and output voltage of 24–40 V and operating at a switching frequency of 107 kHz. The feasibility and performance of the proposed converter were verified by simulation and experimental results. Full article

This article presents the design and implementation of a DC–DC power converter for application in electric vehicle (EV) fast-charging systems. The prototype is of the resonant LLC type and consists of a high-power transformer operating at high frequency, which is an essential feature for the adequate behavior of the EV fast-charging system as a whole. As demonstrated throughout the article, by using this converter topology as well as its specific operating modes, such as for achieving zero-voltage switching (ZVS) and zero-current switching (ZCS), it is possible to enhance efficiency by reducing conduction and switching losses as well as to increase power density. The details of the high-power high-frequency transformer (HFT), considering different designs, are presented and discussed. With the implemented laboratorial prototype fully developed with silicon carbide (SiC) power semiconductor devices, it was possible to demonstrate and validate the main features of the resonant LLC converter, including high efficiency, under distinct conditions of operation. Full article

Germany’s dual Vocational Education and Training (VET) system has been criticized for insufficient cooperation among vocational schools, companies, and inter-company training centers, limiting its potential to effectively relate theory with practice. Despite the issue’s ongoing relevance, recent research on Learning Location Cooperation (LLC) remains scarce. This study addresses the existing research gap by examining contemporary LLC dynamics through the lens of key stakeholders. A total of 20 semi-structured interviews were conducted across interconnected learning locations, with each of the five targeted occupations represented by an apprentice, vocational teacher, trainer, and inter-company trainer. The study design enabled participants, connected through the apprentices’ learning journeys, to discuss LLC phenomena from their unique viewpoints, facilitating an in-depth exploration of cooperation strategies, relationships, conditions for success or failure, and desired improvements. Findings reveal both similarities and differences in perceptions, highlight diverse barriers, and provide actionable recommendations to strengthen LLC. These insights are crucial for refining Germany’s VET system and offer valuable lessons for international contexts, where integrating theory and practice is essential for developing a skilled and adaptable workforce. Overall, the study underscores the importance of fostering deeper cooperation among learning locations to ensure the effectiveness and sustainability of (vocational) education globally. Full article

The modeling of a mixer used for mixing ammonia and flue gasses is considered. Simulations were performed using Flow Vision 3.14 (TESIS LLC). As a result of the simulation, the distribution of concentrations along the mixer length was obtained at 50%, 65%, 85%, and full flue gas loading. It was found that operations at 100% and 85% gas loads are accompanied by an acceptable distribution of ammonia in the mixer volume (Cov = 0.05). The development and creation of an experimental model in real production was carried out according to the results of the numerical simulation. The simulation results were compared with experimental data on the speed and concentration of ammonia in the control section. The discrepancy, in general, did not exceed 15%. The developed mixer corresponds to modern developments in terms of mixing quality but is simpler in design and more compact. Full article

This study reviews advancements in high-frequency converters for renewable energy systems and electric vehicles, emphasizing their role in enhancing energy efficiency and sustainability. Using the PRISMA 2020 methodology, 73 high-quality studies from 2014 to 2024 were synthesized to evaluate innovative designs, advanced materials, control strategies, and future opportunities. Key findings reveal significant progress in converter topologies, such as dual active bridge and LLC resonant designs, which enhance efficiency and scalability through soft-switching. Wide-bandgap semiconductors, including silicon carbide and gallium nitride, have driven improvements in power density, thermal management, and compactness. Advanced control strategies, including adaptive and AI-driven methods, enhance stability and efficiency in microgrids and vehicle-to-grid systems. Applications in photovoltaic and wind energy systems demonstrate the converters’ impact on improving energy conversion and system reliability. Future opportunities focus on hybrid and multifunctional designs that integrate renewable energy, storage, and electric mobility with intelligent control technologies like digital twins and AI. These innovations highlight the transformative potential of high-frequency converters in addressing global energy challenges driving sustainable energy and transportation solutions. This review offers critical insights into current advancements and pathways for further research and development in this field. Full article

LLC resonant converters have emerged as essential components in DC charging station modules, thanks to their outstanding performance attributes such as high power density, efficiency, and compact size. The stability of these converters is crucial for vehicle endurance and passenger experience, making reliability a top priority. However, malfunctions in the switching transistor or current sensor can hinder the converter’s ability to maintain a resonant state and stable output voltage, leading to a notable reduction in system efficiency and output capability. This article proposes a fault diagnosis strategy for LLC resonant converters utilizing a reduced-order interval sliding mode observer. Initially, an augmented generalized system for the LLC resonant converter is developed to convert current sensor faults into generalized state vectors. Next, the application of matrix transformations plays a critical role in decoupling open-circuit faults from the inverter system’s state and current sensor faults. To achieve accurate estimation of phase currents and detection of current sensor faults, a reduced-order interval sliding mode observer has been designed. Building upon the estimation results generated by this observer, a diagnostic algorithm featuring adaptive thresholds has been introduced. This innovative algorithm effectively differentiates between current sensor faults and open switch faults, enhancing fault detection accuracy. Furthermore, it is capable of localizing faulty power switches and estimating various types of current sensor faults, thereby providing valuable insights for maintenance and repair. The robustness and effectiveness of the proposed fault diagnosis algorithm have been validated through experimental results and comparisons with existing methods, confirming its practical applicability in real-world inverter systems. Full article

The LLC resonant converter is widely recognized as an effective solution for achieving high efficiency in high-frequency operations. This is primarily due to its ability to perform zero-voltage switching (ZVS) on primary switches and zero-current switching (ZCS) on secondary rectifier switches. However, implementing the secondary rectifier of an LLC resonant converter often requires the use of jumpers on the PCB to construct circuit topologies such as the center-tap rectifier (CTR), full-bridge rectifier, and voltage-doubler rectifier (VDR). In conventional VDR configurations, the source voltage of the high-side FET fluctuates according to the switching operation of the primary switch. This fluctuation necessitates auxiliary windings or bootstrap circuits to provide a floating voltage source, adding significant complexity to gate drive circuits in high-power-density applications. This complexity poses a major barrier to the practical adoption of VDRs. To address these challenges, this paper proposes a novel rectification circuit based on the VDR topology, specifically designed for LLC resonant converters, offering simplified gate drive circuitry and improved suitability for high-power-density applications. Full article

Background/Objectives: This study investigates the temperature changes on the external root surface during root canal preparation using different rotary systems and assesses the impact of irrigation temperatures. Methods: Sixty extracted human maxillary incisors were divided into four groups based on the rotary system used: ProTaper Next (Dentsply Sirona, Ballaigues, Switzerland), Reciproc Blue (VDW GmbH, Munich, Germany), WaveOne Gold (Dentsply Sirona, Ballaigues, Switzerland), and TruNatomy (Dentsply Sirona, Ballaigues, Switzerland). These systems differ in cutting efficiency and design. Temperature measurements during instrumentation and irrigation were recorded using a FLIR E60bx thermal camera (Teledyne FLIR LLC, Hudson, NH, USA). Irrigations were conducted with sodium hypochlorite at room temperature and heated to 60 °C. Results: The ProTaper Next group exhibited the highest average temperature increase during instrumentation (5.2 °C), followed by WaveOne Gold (4.3 °C), Reciproc Blue (3.7 °C), and TruNatomy (2.8 °C). During irrigation with heated sodium hypochlorite, temperature rises recorded were 6.8 °C for ProTaper Next, 5.9 °C for WaveOne Gold, 5.2 °C for Reciproc Blue, and 4.1 °C for TruNatomy. Statistical analysis revealed a significant negative correlation between dentin thickness and temperature rise, with r-values ranging from −0.62 to −0.87 across the groups. No significant correlation was found between canal diameter and temperature change, indicating that the canal’s size does not influence the thermal impact as much as the properties of the rotary system and irrigation temperature. Conclusions: Different rotary systems produce varying levels of temperature increases on the external root surface, influenced significantly by the thickness of the dentin and the temperature of the irrigation solution. These variations necessitate careful selection of instrumentation and irrigation protocols to minimize potential thermal damage to surrounding periodontal tissues. Full article

Optimized guidelines for the design of power converters are crucial to achieve the expected goals in terms of performance, efficiency, power density, etc. Therefore, they are the basis for industrial success or failure. Resonant converters based on Dual Active Bridges (DABs) are particularly sensitive to the design process due to their inherently nonlinear behaviour; thus, they are in the spotlight for research and development at present. Plenty of design methodologies can be found in the literature but each of them is specific to the perspective of the authors, the performed analysis, the assumptions made, and the design objectives. It is critical to understand the Key Performance Indicators (KPIs) and design methodologies of a resonant DAB converter. There is a significant lack of articles that concisely and clearly summarize this. Different design methodologies are analyzed and compared with respect to the most important KPIs, and the most relevant demos and experiences are pointed out so that designers can select the best choice for their assignment. These results will help designers understand the design methodologies and carefully choose one based on the application, analysis, and design objectives. Full article

This research investigates the advantages of Kelvin-connected 4-pin discrete transistors, both MOSFETs and IGBTs, in onboard battery chargers for electric vehicles. The study compares the standard 3-pin and the extended 4-pin packages based on averaged data collected from leading manufacturers. The investigation shows significant potential power loss reduction, thermal operation mitigation, and reduced gate-drive oscillation for the 4-pin package. The benefits have been quantified by analysing the operation of actual switches in an automotive battery charger based on Boost-PFC and DC-DC LLC converters. The converters’ practical design demonstrates a procedure for integrating the Kelvin-connected package into the design methodology. The results have been verified experimentally. Full article

This paper conducts an in-depth study of a wireless, hierarchical structure-based active balancing system for power batteries, aimed at addressing the rapid advancements in battery technology within the electric vehicle industry. The system is designed to enhance energy density and the reliability of the battery system, developing a balancing system capable of managing cells with significant disparities in characteristics, which is crucial for extending the lifespan of lithium-ion battery packs. The proposed system integrates wireless self-networking technology into the battery management system and adopts a more efficient active balancing approach, replacing traditional passive energy-consuming methods. In its design, inter-group balancing at the upper layer is achieved through a soft-switching LLC resonant converter, while intra-group balancing among individual cells at the lower layer is managed by an active balancing control IC and a bidirectional buck–boost converter. This configuration not only ensures precise control but also significantly enhances the speed and efficiency of balancing, effectively addressing the heat issues caused by energy dissipation. Key technologies involved include lithium-ion batteries, battery management systems, battery balancing systems, LLC resonant converters, and wireless self-networking technology. Tests have shown that this system not only reduces energy consumption but also significantly improves energy transfer efficiency and the overall balance of the battery pack, thereby extending battery life and optimizing vehicle performance, ensuring a safer and more reliable operation of electric vehicle battery systems. Full article