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Keywords = LDC converter

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19 pages, 5665 KiB  
Article
A Novel Two-Stage Power Conversion Method Suitable for 1MHz-LDC of Electric Vehicles
by Tran Manh Tuan, Abdul Shakoor Akram and Woojin Choi
Electronics 2025, 14(12), 2403; https://doi.org/10.3390/electronics14122403 - 12 Jun 2025
Viewed by 317
Abstract
Low-Voltage DC-DC converters (LDCs) in electric vehicles require high power density and high efficiency operation over the wide range of load and input voltage variations. This paper introduces a novel topology which combines three 1 MHz half-bridge (HB) LLC resonant converters and an [...] Read more.
Low-Voltage DC-DC converters (LDCs) in electric vehicles require high power density and high efficiency operation over the wide range of load and input voltage variations. This paper introduces a novel topology which combines three 1 MHz half-bridge (HB) LLC resonant converters and an inverting buck–boost (IBB) converter to adjust the output voltage without frequency modulation. The switching frequency of the proposed converter is fixed at 1 MHz to achieve a constant frequency operation for the resonant converter. In the proposed topology, Gallium Nitride (GaN) devices and planar transformers are employed to optimize the converter operation at high frequency. A 1-MHz/1.8 kW-400/14 V prototype converter is built to verify the feasibility and the validity of the proposed LDC topology. Full article
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16 pages, 22951 KiB  
Article
Non-Destructive Testing of Carbon Fiber-Reinforced Plastics (CFRPs) Using a Resonant Eddy Current Sensor
by Ming Ma, Shiyu Liu, Ronghua Zhang, Qiong Zhang, Yi Wu and Bailiang Chen
Sensors 2024, 24(11), 3449; https://doi.org/10.3390/s24113449 - 27 May 2024
Cited by 7 | Viewed by 2335
Abstract
Eddy current testing (ECT) is commonly used for the detection of defects inside metallic materials. In order to achieve the effective testing of CFRP materials, increasing the operating frequency or improving the coil structure is a common method used by researchers. Higher or [...] Read more.
Eddy current testing (ECT) is commonly used for the detection of defects inside metallic materials. In order to achieve the effective testing of CFRP materials, increasing the operating frequency or improving the coil structure is a common method used by researchers. Higher or wider operating frequencies make the design of the ADC’s conditioning circuit complex and difficult to miniaturize. In this paper, an LC resonator based on inductance-to-digital converters (LDCs) is designed to easily detect the resonant frequency response to the state of the material under test. The reasonableness of the coil design is proven by simulation. The high signal-to-noise ratio (SNR) and detection sensitivity of the LC resonator are demonstrated through comparison experiments involving multiple probes. The anti-interference capability of the LC resonator in CFRP defect detection is demonstrated through various interference experiments. Full article
(This article belongs to the Section Sensor Materials)
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13 pages, 4936 KiB  
Article
Research on the Time Drift Stability of Differential Inductive Displacement Sensors with Frequency Output
by Xiaolong Lu, Guiyun Tian, Zongwen Wang, Wentao Li, Dehua Yang, Haoran Li, You Wang, Jijun Ni and Yong Zhang
Sensors 2022, 22(16), 6234; https://doi.org/10.3390/s22166234 - 19 Aug 2022
Cited by 31 | Viewed by 3354
Abstract
An edge displacement sensor is one of the key technologies for building large segmented mirror astronomical optical telescopes. A digital interface is one novel approach for sensor technologies, digital transformation and the Internet of Things (IoT) in particular. Frequency output sensors and inductance-to-digital [...] Read more.
An edge displacement sensor is one of the key technologies for building large segmented mirror astronomical optical telescopes. A digital interface is one novel approach for sensor technologies, digital transformation and the Internet of Things (IoT) in particular. Frequency output sensors and inductance-to-digital converter (LDC) demonstrated significant advantages in comparison with conventional sensors with analog-to-digital converter (ADC) interfaces. In order for the differential inductive frequency output displacement (DIFOD) sensor to meet the high-stability requirements of segmented mirror astronomical telescopes, it is important to understand the factors for time drift of the sensor. This paper focuses on the investigation of key factors of sensor structure and material, signal conditioning and interface, and fixtures for time drift to permanently installed applications. First, the measurement principle and probe structural characteristics of the sensor are analyzed. Then, two kinds of signal conditioning and digitalization methods using resonance circuits and LDC chips are implemented and compared. Finally, the time drift stability experiments are performed on the sensors with different signal conditioning methods and fixtures under controlled temperature. Experimental results show that the magnetic shield ring effectively improves the sensitivity and quality factor of the sensors, the time drift stability of the sensor using the signal conditioning based on resonance circuits is better than that of the sensors using LDC chips, and the root mean square (RMS) of the sensor time drift meets the requirement of 0.01 μm/24 h. This study will help further development of high-stability of frequency output sensors and IoT-based systems for scaled-up applications in the future. Full article
(This article belongs to the Section Electronic Sensors)
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19 pages, 6735 KiB  
Article
A High-Power-Density Active-Clamp Converter with Integrated Planar Transformer
by Dae-Woo Lee, Ji-Hoon Lim, Dong-In Lee and Han-Shin Youn
Energies 2022, 15(15), 5609; https://doi.org/10.3390/en15155609 - 2 Aug 2022
Cited by 8 | Viewed by 3878
Abstract
This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and [...] Read more.
This paper proposes an active-clamp forward-flyback (ACFF) converter with an integrated planar transformer for wide-input voltage and high-output current applications, such as low-voltage direct-current (LDC) converters in electric vehicles. An integrated planar transformer that consists of a forward-flyback transformer, single primary winding, and efficient structure of secondary windings is adopted for the proposed converter, and since this transformer is implemented with a common four-layer printed circuit board (PCB) winding, a high power density and low cost of the proposed converter can be achieved. In addition, due to the low leakage inductance induced by the planar transformer, a reduced commutation period can be achieved, and it is possible to increase the switching frequency resulting in low volume of transformer. Although the integrated planar transformer has relatively high conduction loss, the active-clamp topology can significantly reduce the conduction loss on switches compared with widely used full-bridge (FB) converters because it only utilizes two switches and shows the low circulating current. As a result, the proposed converter with an integrated planar transformer has strengths in high power density and cost competitiveness without degraded efficiency, and it is a very attractive topology for LDC converters and other applications that require wide-input voltage and high-output current. Full article
(This article belongs to the Topic Advanced Electric Vehicle Technology)
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20 pages, 2997 KiB  
Article
From Enzyme to Preparative Cascade Reactions with Immobilized Enzymes: Tuning Fe(II)/α-Ketoglutarate-Dependent Lysine Hydroxylases for Application in Biotransformations
by Selina Seide, Lilia Arnold, Solange Wetzels, Mariela Bregu, Jochem Gätgens and Martina Pohl
Catalysts 2022, 12(4), 354; https://doi.org/10.3390/catal12040354 - 22 Mar 2022
Cited by 9 | Viewed by 3353
Abstract
Fe(II)/α-ketoglutarate-dependent dioxygenases (KDOs) catalyze a broad range of selective C–H oxidation reactions. However, the difficult production of KDOs in recombinant E. coli strains and their instability in purified form have so far limited their application in preparative biotransformations. Here, we investigated the immobilization [...] Read more.
Fe(II)/α-ketoglutarate-dependent dioxygenases (KDOs) catalyze a broad range of selective C–H oxidation reactions. However, the difficult production of KDOs in recombinant E. coli strains and their instability in purified form have so far limited their application in preparative biotransformations. Here, we investigated the immobilization of three KDOs (CaKDO, CpKDO, FjKDO) that catalyze the stereoselective hydroxylation of the L-lysine side chain using two one-step immobilization techniques (HaloTag®, EziG™). The HaloTag®-based immobilisates reached the best results with respect to residual activity and stability. In preparative lab-scale experiments, we achieved product titers of 16 g L−1 (3S)-hydroxy-L-lysine (CaKDO) and (4R)-hydroxy-L-lysine (FjKDO), respectively, starting from 100 mM L-lysine. Using a HaloTag®-immobilized lysine decarboxylase from Selenomonas ruminantium (SrLDC), the (3S)-hydroxy-L-lysine from the CaKDO-catalyzed reaction was successfully converted to (2S)-hydroxy-cadaverine without intermediate product purification, yielding a product titer of 11.6 g L−1 in a 15 mL consecutive batch reaction. We propose that covalent in situ immobilization is an appropriate tool to access the preparative potential of many other KDOs. Full article
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21 pages, 4728 KiB  
Article
A Framework for Calculating Peak Discharge and Flood Inundation in Ungauged Urban Watersheds Using Remotely Sensed Precipitation Data: A Case Study in Freetown, Sierra Leone
by Angela Cotugno, Virginia Smith, Tracy Baker and Raghavan Srinivasan
Remote Sens. 2021, 13(19), 3806; https://doi.org/10.3390/rs13193806 - 23 Sep 2021
Cited by 9 | Viewed by 5592
Abstract
As the human population increases, land cover is converted from vegetation to urban development, causing increased runoff from precipitation events. Additional runoff leads to more frequent and more intense floods. In urban areas, these flood events are often catastrophic due to infrastructure built [...] Read more.
As the human population increases, land cover is converted from vegetation to urban development, causing increased runoff from precipitation events. Additional runoff leads to more frequent and more intense floods. In urban areas, these flood events are often catastrophic due to infrastructure built along the riverbank and within the floodplains. Sufficient data allow for flood modeling used to implement proper warning signals and evacuation plans, however, in least developed countries (LDC), the lack of field data for precipitation and river flows makes hydrologic and hydraulic modeling difficult. Within the most recent data revolution, the availability of remotely sensed data for land use/land cover (LULC), flood mapping, and precipitation estimates has increased, however, flood mapping in urban areas of LDC is still limited due to low resolution of remotely sensed data (LULC, soil properties, and terrain), cloud cover, and the lack of field data for model calibration. This study utilizes remotely sensed precipitation, LULC, soil properties, and digital elevation model data to estimate peak discharge and map simulated flood extents of urban rivers in ungauged watersheds for current and future LULC scenarios. A normalized difference vegetation index (NDVI) analysis was proposed to predict a future LULC. Additionally, return period precipitation events were calculated using the theoretical extreme value distribution approach with two remotely sensed precipitation datasets. Three calculation methods for peak discharge (curve number and lag method, curve number and graphical TR-55 method, and the rational equation) were performed and compared to a separate Soil and Water Assessment Tool (SWAT) analysis to determine the method that best represents urban rivers. HEC-RAS was then used to map the simulated flood extents from the peak discharges and ArcGIS helped to determine infrastructure and population affected by the floods. Finally, the simulated flood extents from HEC-RAS were compared to historic flood event points, images of flood events, and global surface water maximum water extent data. This analysis indicates that where field data are absent, remotely sensed monthly precipitation data from Integrated Multi-satellitE Retrievals for GPM (IMERG) where GPM is the Global Precipitation Mission can be used with the curve number and lag method to approximate peak discharges and input into HEC-RAS to represent the simulated flood extents experienced. This work contains a case study for seven urban rivers in Freetown, Sierra Leone. Full article
(This article belongs to the Special Issue Geospatial Techniques for Urban Water Management)
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18 pages, 9463 KiB  
Article
A Novel Hybrid LDC Converter Topology for the Integrated On-Board Charger of Electric Vehicles
by Vu-Hai Nam, Duong-Van Tinh and Woojin Choi
Energies 2021, 14(12), 3603; https://doi.org/10.3390/en14123603 - 17 Jun 2021
Cited by 5 | Viewed by 4310
Abstract
Recently, the integrated On-Board Charger (OBC) combining an OBC converter with a Low-Voltage DC/DC Converter (LDC) has been considered to reduce the size, weight and cost of DC-DC converters in the EV system. This paper proposes a new integrated OBC converter with V2G [...] Read more.
Recently, the integrated On-Board Charger (OBC) combining an OBC converter with a Low-Voltage DC/DC Converter (LDC) has been considered to reduce the size, weight and cost of DC-DC converters in the EV system. This paper proposes a new integrated OBC converter with V2G (Vehicle-to-Grid) and auxiliary battery charge functions. In the proposed integrated OBC converter, the OBC converter is composed of a bidirectional full-bridge converter with an active clamp circuit and a hybrid LDC converter with a Phase-Shift Full-Bridge (PSFB) converter and a forward converter. ZVS for all primary switches and nearly ZCS for the lagging switches can be achieved for all the operating conditions. In the secondary side of the proposed LDC converter, an additional circuit composed of a capacitor and two diodes is employed to clamp the oscillation voltage across rectifier diodes and to eliminate the circulating current. Since the output capacitor of the forward converter is connected in series with the output capacitor of the auxiliary battery charger, the energy from the propulsion battery can be delivered to the auxiliary battery during the freewheeling interval and it helps reduce the current ripple of the output inductor, leading to a smaller volume of the output inductor. A 1 kW prototype converter is implemented to verify the performance of the proposed topology. The maximum efficiency of the proposed converter achieved by the experiments is 96%. Full article
(This article belongs to the Collection Invited Papers on Electric Vehicles)
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27 pages, 1914 KiB  
Review
Resolving the Contradictory Functions of Lysine Decarboxylase and Butyrate in Periodontal and Intestinal Diseases
by Martin Levine and Zsolt M. Lohinai
J. Clin. Med. 2021, 10(11), 2360; https://doi.org/10.3390/jcm10112360 - 27 May 2021
Cited by 9 | Viewed by 4132
Abstract
Periodontal disease is a common, bacterially mediated health problem worldwide. Mastication (chewing) repeatedly traumatizes the gingiva and periodontium, causing traces of inflammatory exudate, gingival crevicular fluid (GCF), to appear in crevices between the teeth and gingiva. Inadequate tooth cleaning causes a dentally adherent [...] Read more.
Periodontal disease is a common, bacterially mediated health problem worldwide. Mastication (chewing) repeatedly traumatizes the gingiva and periodontium, causing traces of inflammatory exudate, gingival crevicular fluid (GCF), to appear in crevices between the teeth and gingiva. Inadequate tooth cleaning causes a dentally adherent microbial biofilm composed of commensal salivary bacteria to appear around these crevices where many bacteria grow better on GCF than in saliva. We reported that lysine decarboxylase (Ldc) from Eikenella corrodens depletes the GCF of lysine by converting it to cadaverine and carbon dioxide. Lysine is an amino acid essential for the integrity and continuous renewal of dentally attached epithelium acting as a barrier to microbial products. Unless removed regularly by oral hygiene, bacterial products invade the lysine-deprived dental attachment where they stimulate inflammation that enhances GCF exudation. Cadaverine increases and supports the development of a butyrate-producing microbiome that utilizes the increased GCF substrates to slowly destroy the periodontium (dysbiosis). A long-standing paradox is that acid-induced Ldc and butyrate production support a commensal (probiotic) microbiome in the intestine. Here, we describe how the different physiologies of the respective tissues explain how the different Ldc and butyrate functions impact the progression and control of these two chronic diseases. Full article
(This article belongs to the Special Issue The Oral Microbiome in Health and Disease)
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17 pages, 7526 KiB  
Article
Full-Bridge Active-Clamp Forward-Flyback Converter with an Integrated Transformer for High-Performance and Low Cost Low-Voltage DC Converter of Vehicle Applications
by Jaeil Baek and Han-Shin Youn
Energies 2020, 13(4), 863; https://doi.org/10.3390/en13040863 - 16 Feb 2020
Cited by 18 | Viewed by 8477
Abstract
This paper presents a full-bridge active-clamp forward-flyback (FBACFF) converter with an integrated transformer sharing a single primary winding. Compared to the conventional active-clamp-forward (ACF) converter, the proposed converter has low voltage stress on the primary switches due to its full-bridge active-clamp structure, which [...] Read more.
This paper presents a full-bridge active-clamp forward-flyback (FBACFF) converter with an integrated transformer sharing a single primary winding. Compared to the conventional active-clamp-forward (ACF) converter, the proposed converter has low voltage stress on the primary switches due to its full-bridge active-clamp structure, which can leverage high performance Silicon- metal–oxide–semiconductor field-effect transistor (Si-MOSFET) of low voltage rating and low channel resistance. Integrating forward and flyback operations allows the proposed converter to have much lower primary root mean square (RMS) current than the conventional phase-shifted-full-bridge (PSFB) converter, while covering wide input/output voltage range with duty ratio over 0.5. The proposed integrated transformer reduces the transformer conduction loss and simplify the secondary structure of the proposed converter. As a result, the proposed converter has several advantages: (1) high heavy load efficiency, (2) wide input voltage range operation, (3) high power density with the integrated transformer, and (4) low cost. The proposed converter is a very promising candidate for applications with wide input voltage range and high power, such as the low-voltage DC (LDC) converter for eco-friendly vehicles. Full article
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22 pages, 10539 KiB  
Article
Numerical Analysis of the Cooling Performance in a 7.2 kW Integrated Bidirectional OBC/LDC Module
by Jung-Hun Noh, Seong-il Song and Deog-Jae Hur
Appl. Sci. 2020, 10(1), 270; https://doi.org/10.3390/app10010270 - 30 Dec 2019
Cited by 3 | Viewed by 3908
Abstract
To satisfy increasing demands for ecofriendly vehicles, researchers are now studying electric vehicle (EV)-related technologies. In particular, integrated bidirectional onboard battery charger (OBC)/low-voltage DC–DC converter (LDC) modules are being researched to improve the efficiency of onboard chargers for EV charging applications. In this [...] Read more.
To satisfy increasing demands for ecofriendly vehicles, researchers are now studying electric vehicle (EV)-related technologies. In particular, integrated bidirectional onboard battery charger (OBC)/low-voltage DC–DC converter (LDC) modules are being researched to improve the efficiency of onboard chargers for EV charging applications. In this study, a numerical analysis method is proposed that considers the power loss and heat flow characteristics in the design of a 7.2 kW integrated bidirectional OBC/LDC module. The developed module supports four operating modes depending on the service situation: OBC and LDC single operation, OBC/LDC simultaneous operation, and LDC operation. The mode is selected based on the power system flow. The characteristics of the circuit were analyzed in each of the four modes to compute the heat loss from the major heating elements. The results of a numerical analysis of the internal cooling characteristics showed that the internal temperature was higher in the OBC single operating mode than in the OBC and LDC simultaneous operating mode in which the power loss was the highest. The results emphasize the importance of ensuring that cooling designs consider the characteristics of various modes as well as the worst-case power loss. Full article
(This article belongs to the Section Mechanical Engineering)
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16 pages, 4023 KiB  
Article
Optimization Based on Product and Desirability Functions for Flow Distribution in Multi-Channel Cooling Systems of Power Inverters in Electric Vehicles
by Deog-Jae Hur, Suk-Hwan Jeong, Seong-Il Song and Jung-Hun Noh
Appl. Sci. 2019, 9(22), 4844; https://doi.org/10.3390/app9224844 - 12 Nov 2019
Cited by 3 | Viewed by 4041
Abstract
The onboard charger (OBC)/low-voltage DC-DC converter (LDC) integrated power inverter for electric vehicles comprises multiple electrical elements that can heat up, which can cause performance degradation and system instability issues in electric vehicles. To address this, a cooling system is included in the [...] Read more.
The onboard charger (OBC)/low-voltage DC-DC converter (LDC) integrated power inverter for electric vehicles comprises multiple electrical elements that can heat up, which can cause performance degradation and system instability issues in electric vehicles. To address this, a cooling system is included in the OBC/LDC integrated power inverter, which primarily uses water as a coolant. In this water cooling method, controlling the flow rate of water is critical for uniform cooling of the component. Thus, we propose an optimization method that helps determine the design variables to ensure uniform flow rate in each channel of the water-cooled system. The control variables for fluid-flux flow distribution optimization are selected by performing flow analysis for the initial design shape and analyzing their effects on fluid-flux flow distribution. For optimization analysis, the central composite design technique was applied; in addition, multi-response surface optimization using the same flow rate for each channel was performed. The optimization results were compared and verified using desirability functions based on the flow ratio of the cooling water channel, product function, and error function. Among single-response objective functions, the product function showed excellent performance. However, optimization using a multi-response objective function showed significantly higher prediction accuracy than the single-response function: using the optimized design obtained with the multi-response objective function improved the fluid-flux flow distribution uniformity by approximately 90% or more than the initial design. Full article
(This article belongs to the Section Mechanical Engineering)
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