Search Results (36)

Modular multilevel converters (MMCs) are widely used in power-conversion applications, including distributed energy storage integration, because of their scalability, high efficiency, and reduced harmonic distortion. Integrating battery storage systems into MMC submodules using dual active bridge (DAB) converters provides electrical isolation and reduces voltage stress, harmonics, and common-mode issues. However, voltage fluctuations due to the battery state of charge can compromise the zero-voltage switching (ZVS) operation of a DAB and increase the reactive power circulation, leading to higher losses and reduced system performance. To address these challenges, this study investigated an active control strategy for submodule voltage regulation in an MMC with DAB-based battery integration. Assuming single-phase-shift modulation, two control strategies were evaluated. The first strategy regulated the DAB voltage on one side to match the battery voltage on the other, scaled by the high-frequency transformer turns ratio, which facilitated the ZVS operation and reduced the reactive power. The second strategy optimized this voltage to minimize the total power-conversion losses. The proposed control strategies improved the efficiency, particularly at low power levels, achieving several percentage points of improvement compared to maintaining a constant voltage. Full article

This paper introduces a novel topology called the dual-path step-down converter with auxiliary switches to minimize voltage stress and enable wide voltage conversion ranges. The proposed dual-path step-down converter with auxiliary switches, which uses an inductor and flying capacitor as power conversion components, helps to reduce the voltage stress on the power switches. By adding auxiliary switches, the proposed topology achieves the same voltage conversion ratio range as that of a conventional buck converter. Additionally, soft-start technology is incorporated to reduce the initial inrush current. Furthermore, this paper introduces a system-level design procedure for DC-DC converters. Designed for low-power applications with lithium-ion (Li-ion) batteries, the proposed converter steps down the battery voltage to 1.2 V. With a 380 nH inductor and a 5 µF output capacitor, the converter attains a peak efficiency of 90% under the conditions of 2.7 V to 1.2 V conversion. Full article

The four-quadrant detector (4QD), as a highly sensitive and fast-response position-sensitive device, is widely used in laser guidance, target tracking, and related fields. However, traditional visible and infrared 4QDs exhibit significant vulnerability to ambient light interference, particularly under high-intensity background illumination. To address this issue, this paper presents a solar-blind ultraviolet (UV) 4QD and a spot positioning system based on AlGaN diodes, achieving a UV/visible suppression ratio of 2.17 × 10⁴ (without solar-blind filters). The system employs a high-linearity, low-noise capacitive transimpedance amplifier (CTIA) as the readout circuit for the high-sensitivity and rapid-response solar-blind UV detectors, enabling the precise conversion of weak photocurrent signals into voltage signals for digitization. Utilizing a third-order polynomial least-squares fitting algorithm without introducing complex filtering techniques, the system achieves a maximum positioning error of 0.0101 mm and a root-mean-square error (RMSE) of 0.0057 mm, among of one the best-performing solar-blind UV 4QDs. The experimental results demonstrate exceptional spot positioning performance under a 275 nm laser source, meeting the high-precision requirements for space target detection. This research provides a reference for the application of solar-blind UV 4QDs in positioning, alignment, and monitoring scenarios, thereby holding significant practical implications. Full article

Microwave photonic (MWP) systems are inseparable from conversions of microwave electrical signals into optical signals, and their performances highly depend on the linearity of electro-optic modulators. Thin-film lithium niobate (TFLN) is expected to be an ideal platform for future microwave photonic systems due to its compact size, low optical loss, linear electro-optic effect, and high bandwidth. In this paper, we propose a TFLN modulator with a low voltage–length product (V_πL) of 1.97 V·cm and an ultra-high-linearity carrier-to-distortion ratio (CDR) of 112.33 dB, using a dual-parallel Mach–Zehnder interferometer configuration. It provides an effective approach to fully suppress the third-order intermodulation distortions (IMD3), leading to 76 dB improvement over a single Mach–Zehnder modulator (MZM) in TFLN. The proposed TFLN modulator would enable a wide variety of applications in integrated MWP systems with large-scale integration, low power consumption, low optical loss, and high bandwidth. Full article

Human observation of the ocean has gradually evolved from the sea surface to systematic monitoring and sampling through seafloor observation networks, and constant current power supply has become the main power supply method for seafloor observation networks due to its high reliability. There are some studies on current source to voltage source converters, but there are few studies on current source to current source (CS/CS) converters, which affects the expansion of power supply networks for seafloor observation networks. In this paper, by employing input current sharing and output voltage doubling circuits, an active clamp dual-inductor isolated CS/CS converter which uses a single-stage conversion circuit to realize constant current source conversion with a wide output voltage range is proposed. Active clamp technology at the primary side of the proposed circuit is employed to recover energy stored in leakage inductance, suppress voltage spikes of the primary side switches, and achieve zero-voltage switching of the primary side switches. The secondary side’s output voltage doubling circuit resonates with transformer leakage inductance to achieve zero-current switching of the secondary side diodes, which can reduce losses and enhance efficiency. The operating principles of the proposed circuit are analyzed in detail, and the characteristic and parameter design analysis, including current conversion ratio, transformer turn ratio, power inductors, and resonant capacitors and inductor, are presented. Finally, the experimental results based on a 100 W experimental prototype validate the feasibility of the proposed converter. Full article

This paper proposes a VCO-based ADC with first-order noise shaping for EEG signal recording front ends. Addressing the challenge of applying analog integrators in advanced processes due to low voltage issues, a multi-phase quantizer structure is introduced based on V-F conversion within the VCO structure, resulting in lower analog power consumption at the same output bit-width. By introducing a form of Gray code encoding, errors caused by circuit metastability are limited to within 1 bit. Considering the effects of motion artifacts and the electrode DC offset, the circuit achieves a wide input range of 500 m$V_{pp}$ by adjusting the feedback coefficients. A prototype ADC is fabricated using 180 nm CMOS technology, operating at a 1.8 V/1 V power supply voltage, with power consumption of 17.1 $\mathsf{\mu }$W, while achieving a 62.1 dB signal-to-noise and distortion ratio (SNDR) and 55.2 dB dynamic range (DR). The proposed ADC exhibits input noise of 8.64 $\mathsf{\mu }$$V_{rms}$ within a bandwidth of 0.5 Hz–5 kHz. Full article

Layers of TiO₂ nanotubes formed by the anodization process represent an area of active research in the context of innovative energy conversion and storage systems. Titanium nanotubes (TNTs) have attracted attention because of their unique properties, especially their high surface-to-volume ratio, which makes them a desirable material for various technological applications. The anodization method is widely used to produce TNTs because of its simplicity and relative cheapness; the method enables precise control over the thickness of TiO₂ nanotubes. Anodization can also be used to create decorative and colored coatings on titanium nanotubes. In this study, a combined structure including anodic TiO₂ nanotubes and SrTiO₃ particles was fabricated using chemical synthesis techniques. TiO₂ nanotubes were prepared by anodizing them in ethylene glycol containing NH₄F and H₂O while applying a voltage of 30 volts. An anode nanotube array heat-treated at 450 °C was then placed in an autoclave filled with dilute SrTiO₃ solution. Scanning electron microscopy (SEM) analysis showed that the TNTs were characterized by clear and open tube ends, with an average outer diameter of 1.01 μm and an inner diameter of 69 nm, and their length is 133 nm. The results confirm the successful formation of a structure that can be potentially applied in a variety of applications, including hydrogen production by the photocatalytic decomposition of water under sunlight. Full article

The paper introduces a step-down converter that exhibits a static conversion ratio of cubic nature, providing an output voltage which is much closer to the input voltage, and at the same duty cycle, compared to a wide class of one-transistor buck-type topologies. Although the proposed topology contains many components, its control is still simple, as it employs only one transistor. A dc analysis is performed, the semiconductor stresses are derived in terms of input and output voltages and output power, revealing that the semiconductor voltage stresses remain acceptable and anyway lower than in other cubic buck topology. All detailed design equations are provided. The state-space approach is used to analyze the converter in the presence of conduction losses and a procedure for calculating the individual power dissipation is provided. The feasibility of the proposed cubic buck topology is first validated by computer simulation and finally confirmed by an experimental 12 V–10 W prototype. Full article

This paper aims to investigate the state-of-the-art isolated high-step-up DC–DC topologies developed for photovoltaic (PV) systems. This study categorises the topologies into transformer-based and coupled inductor-based converters, as well as compares them in terms of various parameters such as component count, cost, voltage conversion ratio, efficiency, voltage stress, input current ripple, switching mode, and power rating. The majority of the topologies examined exhibit peak efficiencies of 90% to 97%, with voltage conversions in excess of eight, as well as power ratings ranging from 100 W to 2 kW. The existing literature has found that most isolated DC–DC converters increase their turn ratios in order to achieve high step-up ratios. As a result, voltage spikes have increased significantly in switches, resulting in a decrease in overall system efficiency. In this research, the use of passive and active snubbers to provide soft switching in isolated step-up DC–DC converters is investigated. Moreover, a comprehensive analysis of the three most widely used boost techniques is provided. A reduction in turn ratio and a decrease in voltage stress were the results of this process. The main purpose of this study is to provide a comprehensive overview of the most used high-boost isolated DC–DC topologies in PV systems, including flyback, isolated SEPIC, forward, push-pull, half- and full-bridge, and resonant converter, with a focus on the recent research in the field and the recent advancements in these topologies. This study aims to guide further research and analysis in selecting appropriately isolated topologies for PV systems. Full article

We have investigated the effects of the methylammonium bromide (MABr) content of the precursor solution on the properties of wide-bandgap methylammonium lead tribromide (MAPbBr₃) perovskite solar cells (PSCs). In addition, the anti-solvent process for fabricating MAPbBr₃ perovskite thin films was optimized. The MAPbBr₃ precursor was prepared by dissolving MABr and lead bromide (PbBr₂) in N,N-dimethylformamide and N,N-dimethyl sulfoxide. Chlorobenzene (CB) was used as the anti-solvent. We found that both the morphology of the MAPbBr₃ layer and the PSCs performance are significantly affected by the MABr content in perovskite precursor solution and anti-solvent dripping time. The best-performing device was obtained when the molar ratio of MABr:PbBr₂ was 1:1 and the CB drip time was 10 s. The best device exhibited a power conversion efficiency of 7.58%, short-circuit current density of 7.32 mA·cm⁻², open-circuit voltage of 1.30 V, and fill factor of 79.87%. Full article

Solar-driven interfacial evaporation (SDIE) is considered a sustainable and environmentally friendly technology for using solar energy to produce fresh water, which is a crucial resource for the existence of human life. Porous membranes are widely used in SDIE owing to their porous structure, which is highly suitable for this kind of photothermal material and allows an efficient supply of water and escape of vapor during the evaporation process. Electrospinning is perhaps the most versatile technique to produce highly porous structures of nanofiber membranes with a large surface-to-volume ratio, high porosity, low density, and many advantages. Nevertheless, acquiring a stronger background on the initial research questions in this enticing field of research needs further investigation. Typically, for the enhancement of process control, the impact of flow rate on the morphology of the prepared membrane is quite important. This research article has two-fold objectives: firstly, it discusses the fundamental description of the photothermal conversion mechanism of polymer-based photothermal materials for water treatment. A systematic investigation supported by previous studies revealing the working mechanism and the design of solar-driven interfacial evaporation has been provided. On the other hand, our interim experimental results elaborate on the influence of process conditions such as electrospinning parameters on the structural morphology and diameter of fabricated electrospun nanofibers produced by using the coaxial electrospinning setup in our lab. The scanning electron microscope (SEM) was used to examine the morphology of the electrospun nanofibers. Our introductory results provide a useful insight into tuning the necessary process parameters to fabricate electrospun polyacrylonitrile (PAN) nanofiber membranes by electrospinning technique. From our preliminary results after the three processing experiments, it is revealed that a polymer concentration of 10% wt., an applied voltage of 20 kV, a tip-to-collector distance of 18 cm, and a flow rate of 0.8 mL/h produce the optimum nanofiber membranes with a uniform structure and a diameter in the range 304–394 nm. The variation in the diameter of nanofibers in the three processing conditions is endowed by the regulation of the initiating droplet extruded from the tip of the metallic needle (syringe jet) to the collector using the electrospinning setup. Full article

This paper presents a 1-GS/s12-bit pipelined analog-to-digital converter (ADC) fabricated in 40-nm CMOS technology that optimizes the settling time, bit error rate, and robustness. This ADC uses an improved timing called pre-quantization timing (PQT), which implements quantization in half the time of the sampling phase to maximize the output-settling time of the operational amplifier (op-amp). A complete clocking scheme along with a delay lock loop (DLL) is proposed to generate an accurate timing no matter how process, voltage, and temperature (PVT) change. Based on PQT, a high-speed comparator circuit is adopted to obtain a bit error rate (BER) below 10⁻¹⁵. Sample and hold amplifier (SHA) is used to guarantee robustness over the wide input frequency. Furthermore, a low-cost automatic calibration is implemented to correct residual curves, and inter-stage gain errors are also corrected. This ADC achieves a signal-to-noise-and-distortion ratio (SNDR) of 57.3 dB and a spurious-free dynamic range (SFDR) of 78.5 dB at a 227 MHz input frequency. The measured differential nonlinearities (DNL) and integral nonlinearities (INL) after calibration are ±0.7 LSB and ±1.50 LSB, respectively. The power consumption of the ADC core is 97.6-mW, and the Walden figure of merit (FoM) is 172.9-fJ/conversion-step. Full article

Whilst Cu(In,Ga)Se₂ (CIGSe) is an extremely promising material for solar cell fabrication, the widening of the band gap beyond the standard 1.1 eV is highly desirable for semitransparent applications. By replacing Cu with Ag and increasing the Ga content, we fabricate ACIGSe absorbers with band gaps ranging from 1.27–1.55 eV. An Ag/(Ag + Cu) ratio from 0.36–1.00 is chosen, as well as a Ga/(Ga + In) ratio from 0.25–0.59. The larger Ag and Ga contents lead to the expected band gap widening, which is, together with high sub-gap transparency, essential for semitransparent applications. The crystalline properties are confirmed by Raman spectroscopy and X-ray diffraction, which both reveal peak shifts according to the composition variations: a higher Ag content results in lower Raman shifts as well as in lower angles of X-ray diffraction for the main peaks due to the larger mass of Ag compared to Cu and the larger lattice constant of Ag-rich compounds. Increased open circuit voltages and decreased short circuit current densities are confirmed for higher band gaps. An overall trend of increased power conversion efficiency of the related devices is promising for future research of wide band gap Ag-chalcopyrites and their semitransparent application. Full article

This study proposes a novel bidirectional isolated DC/DC converter with a high gain ratio and wide input voltage for electric vehicle (EV) storage systems. The DC bus of an EV can be used to charge its battery, and the battery pack can discharge energy to the DC bus through the bidirectional converter when the DC bus lacks power. The input voltage range of the proposed converter is 24 to 58 V on the low-voltage side, which meets the voltage specifications of most servers and batteries on the market. The proposed topology is verified through design, simulation, and implementation, and voltage gain, voltage stress, and current stress are investigated. The control bidirectional converter is simple. Only one set of complementary signals is required for step-up and step-down modes, which greatly reduces costs. The converter also features a continuous current at the low-voltage side, a leakage inductance function for energy recovery, and zero-voltage switching (ZVS) on certain switches, which can prevent voltage spikes on the switches and increase the efficiency of the proposed converter. A bidirectional converter with a total power of 1 kW is used to verify the topology’s feasibility and practicability. The power at the low-voltage side was 24–58 V, and the maximum efficiency in step-up mode was 94.5%, 96.5%, and 94.8%, respectively; the maximum efficiency in step-down mode was 94.4%, 95.4%, and 93.7%, respectively. Full article

We present a high-power conversion efficiency (PCE) on-chip switched-capacitor (SC) DC–DC step-up converter for a fully implantable neural interface operating with less than a few tens µW from energy harvesting. To improve the PCE in such light loads and wide variations of voltage-conversion ratio (VCR), which is a typical scenario for ultra-low-power fully implantable systems depending on energy harvesting, a phase-reduced soft-charging technique has been implemented in a step-up converter, thereby achieving very low VCR-sensitive PCE variation compared with other state-of-the-art works. The proposed DC–DC converter has been fabricated in a standard 180 nm CMOS 1P6M process. It exhibits high PCE (~80%) for wide input and output ranges from 0.5 V to 1.2 V and from 1.2 V to 1.8 V, respectively, with switching frequencies of 0.3–2 MHz, achieving a peak efficiency of 82.6% at 54 µW loads. Full article