Analysis and design of a high efficiency bidirectional DC-DC converter for battery and ultracapacitor applications

This paper presents a high efficiency non-isolated bidirectional converter which can be employed as an interface circuit between ultracapacitors or batteries and DC bus voltage. All semiconductor devices in the proposed converter are soft switched while the control circuit remains PWM. So, the energy conversion through the converter is highly efficient. The proposed converter acts as a zero-voltage transition (ZVT) buck to charge an ultracapacitor or battery and acts as a ZVT boost to discharge an ultracapacitor or battery. The performance of the proposed converter with respect to abrupt load and operating mode change is shown through computer simulation results. The results confirm the aforementioned advantages and features of the proposed converter

Single-switch coupled-inductors-based high step-up converter with reduced voltage stress

This paper proposes a non-isolated DC-DC high step-up converter. To achieve a high voltage conversion ratio and overcome the problems related to near unity duty-cycle of the conventional boost converter in high step-up applications, coupled-inductors along with switch-capacitor techniques are merged in this topology. The proposed converter provides continuous input current with low ripple without using any current ripple cancellation method and the voltage across the switch is limited inherently. In order to reduce the control circuit complexity, the proposed converter uses only one switch. These features decrease the complexity of the proposed converter structure. The voltage stress of the semiconductor components is reduced significantly; thus, high-quality elements (fast power MOSFET switches with low on-state resistance and Schottky diodes with low forward voltage drop along with low power losses) can be used, which minimizes the switching and conduction losses and improves the converter efficiency. To confirm the converter operation and theoretical analysis, a 200-W prototype converter with 24-to-200-V input and output voltages operating at 100-kHz is implemented in the laboratory.</p

Well-Ordered Mesoporous Silica and Bioactive Glasses: Promise for Improved Hemostasis

Immediate control of uncontrolled bleeding and infection are essential for saving lives in both combat and civilian arenas. Inorganic well-ordered mesoporous silica and bioactive glasses have recently shown great promise for accelerating hemostasis and infection control. However, to date, there has been no comprehensive report assessing their specific mechanism of action in accelerating the hemostasis process and exerting an antibacterial effect. After providing a brief overview of the hemostasis process, this review presents a critical overview of the recently developed inorganic mesoporous silica and bioactive glass-based materials proposed for hemostatic clinical applications and specifically investigates their unique characteristics that render them applicable for hemostatic applications and preventing infections. This article also identifies promising new research directions that should be undertaken to ascertain the effectiveness of these materials for hemostatic applications

Inorganic Hemostats: The State-Of-The-Art and Recent Advances

Hemorrhage is the most common cause of death both in hospitals and on the battlefield. The need for an effective hemostatic agent remains, since all injuries are not amenable to tourniquet use. There are many topical hemostatic agents and dressings available to control severe bleeding. This article reviews the most commonly used inorganic hemostats, subcategorized as zeolite and clay-based hemostats. Their hemostatic functions as well as their structural properties that are believed to induce hemostasis are discussed. The most important findings from in vitro and in vivo experiments are also covered

Coupled Inductor-based Soft-switched Boost-Ćuk Converter for Microinverter Applications

In this study, a novel fully soft-switched high step-up dc-dc converter is proposed. The proposed converter comprises the integration of boost and Ćuk converters with the same input inductor and MOSFET, and series-connected output dc-link voltages. In this topology, the switch is turned on under zero current switching and low-voltage conditions since the converter works under discontinuous conduction mode due to small output Ćuk inductance. In addition, two coupled inductors are applied to create a similar voltage gain and soft switching conditions for all semiconductor elements. The first coupled inductor is placed in series with the Ćuk diode, which provides a balanced dc-link for wide load and input voltage variations and ZCS conditions for the Ćuk diode. The second coupled inductor forms a lossless passive snubber to provide a zero-voltage switching turn-off condition for the main switch. This lossless passive snubber provides a clamped circuit and reduces the turn-off slew rate of the switch voltage. This snubber circuit is simple with minimum elements, and the snubber capacitor discharges to the output while the switch is OFF. Moreover, the input current is ripple-free, which is appropriate for renewable energy systems integration. The experiments substantiate the effectiveness of the proposed converter

Two-switch Step-down Converter with Low Switch Voltage Stress

The current research introduces an enhanced buck converter. The introduced converter improves the performance of similar converters thanks to causing lower switch voltage stress, higher efficiency and fewer number of elements. To make use of low voltage MOSFETs with a smaller ON resistance, using multiple switching strategies would reduce the voltage stress across the switch and thus allow them to be used. This study compares the performance of the proposed converter with the similar converters. The gate pulses are similar in the proposed converter, so the control is very simple. Input voltage is divided between the blocking capacitors at the input and as a result, the voltage stress on the switches is lower than the input voltage. So, the converter can be designed with MOSFETs with low drain-source resistance. Also, the voltage gain is reduced in comparison with the conventional buck converter. Furthermore, output power is shared between two switches which results in better heat dissipation. Also, it is possible to implement the proposed converter using a single magnetic element. Therefore, the total number of components in comparison with similar converters is reduced. The results show that the introduced converter technically performs with lower switching losses and increased overall efficiency Discussion of operating modes, as well as converter design and test results shall be provided

A high-efficient single-switch, soft-switching high step-up DC–DC converter with a simple structure and continuous input current for renewable energy integration

This article presents a novel single-switch soft-switching high step-up dc–dc boost converter. By utilizing a coupled inductor and series capacitors in the output stage, the converter achieves soft switching performance for the power switch during turn- on and turn- off , along with a high step-up voltage gain. The design of the coupled inductors enables the simultaneous achievement of soft switching and high voltage gain without the need for additional auxiliary circuits, ensuring circuit simplicity and high efficiency. Furthermore, the converter maintains continuous input current, similar to a boost converter, improving battery lifespan and renewable input power source operation. The proposed converter addresses diode reverse recovery issues and incorporates a common ground between input and output stages, simplifying the feedback circuit. Comparative analysis with similar high-efficiency high step-up boost converters is performed, and a 200-W laboratory prototype is implemented.This work was supported in part by the Spanish Ministerio de Ciencia, Innovación y Universidades (MICINN)-Agencia Estatal de Investigación (AEI) by project PID2022-138631OB-I00, in part by MICIU/AEI/10.13039/501100011033 under Grant PID2022-138631OB-I00, and in part by “ERDF/EU.Peer ReviewedPostprint (published version

Hydrothermal Synthesis and Characterisation of Bioactive Glass-Ceramic Nanorods

In this study fabrication of rod-like bioactive glass-ceramics (BGCs) using hydrothermal treatment based on a sol-gel precursor is reported for the first time. BGCs with composition 58 wt% SiO2, 33 wt% CaO and 9 wt% P2O5 were synthesized in different thermal conditions (200 and 220 °C) and characterised with regard to morphology, chemical composition and crystallinity. The bioactivity of the materials was assessed by immersion in simulated body fluid for up to 7 days. The results revealed that as the reaction temperature increased from 200 to 220 °C, the diameter of rods was reduced from microscale to nanoscale and the crystallinity was enhanced. It was also found that the BGC nanorods have higher surface area and consequently enhanced bioactivity than BGC microrods. This technique provides a facile method for rapid production of BGC nanorods at relatively low temperature which may have the potential to be used as bioactive composite reinforcement or for bone grafting applications

Soft-switching non-isolated high step-up three-level boost converter using single magnetic element

Here, a soft switched three-level boost converter with high voltage gain is proposed which is suitable for high step-up applications with wide output power range. In this converter, a ZVT auxiliary circuit is used which provides soft switching in a wide range of output power independent of load variation. Utilizing coupled-inductors with one magnetic core removes extra auxiliary core in the soft switching circuit and provides high voltage gain in conjunction with size reduction. Also, the secondary and tertiary leakage inductances of the coupled-inductors minimize the reverse recovery problem of the output diodes. Due to its three-level structure, it has very low voltage stress over semiconductor elements in comparison to the existing interleaved structures, resulting in using MOSFETs with low on-resistance and thus lower conduction losses and cost. Operating modes as well as analytical analysis of the proposed converter are discussed. Finally, in order to validate the proposed converter performance, experimental results from a 200-W laboratory prototype are presented.Peer ReviewedPostprint (published version

Gallium-Containing Mesoporous Bioactive Glass with Potent Hemostatic Activity and Antibacterial Efficacy

Haemorrhage remains the leading cause of potentially survivable death in both military and civilian populations. Although a large variety of hemostatic agents have been developed, many of them have an inadequate capacity to induce hemostasis and are not effective in killing bacteria. In recent years, mesoporous bioactive glasses (MBGs) were found to be effective in inducing hemostasis. However, the materials may not be considered as ideal hemostats since they do not offer antimicrobial activity. The gallium ion (Ga+3) not only exhibits antibacterial properties but also accelerates the blood coagulation cascade. The aim of this study was to develop MBGs containing various concentrations of Ga2O3 (1, 2 & 3 mol%) via the evaporation-induced self-assembly (EISA) process and investigate whether the addition of Ga3+ would induce both hemostatic and antibacterial effects. The results indicated that the incorporation of lower Ga2O3 content (1 mol%) into the MBG system improved structural properties including the specific surface area, mesopore size and pore volume as well as the release of silicon and calcium ions. The bioactive glass was found to stimulate blood coagulation, platelet adhesion and thrombus generation and exerted an antibacterial effect against both Escherichia coli and Staphylococcus aureus. Likewise, Ga-doped MBGs showed excellent cytocompatibility even after 3 days, with the 1% Ga2O3-containing MBG attaining the best biocompatibility that render them safe hemostatic agents for stopping bleeding. This study demonstrated that the lowest Ga2O3-substituted MBG can be a potent candidate for controlling haemorrhage and wound infection