Search Results (140)

Two-dimensional (2D) material-based resistive random-access memory (RRAM) has emerged as a promising solution for neuromorphic computing and computing-in-memory architectures. Compared to conventional metal-oxide-based RRAM, the novel 2D material-based RRAM devices demonstrate lower power consumption, higher integration density, and reduced performance variability, benefiting from their atomic-scale thickness and ultra-flat surfaces. Remarkably, 2D layered metal oxides retain these advantages while preserving the merits of traditional metal oxides, including their low cost and high environmental stability. Through a multi-step dry transfer process, we fabricated a Pd-MoO₃-Ag RRAM device featuring 2D α-MoO₃ as the resistive switching layer, with Pd and Ag serving as inert and active electrodes, respectively. Resistive switching tests revealed an excellent operational stability, low write voltage (~0.5 V), high switching ratio (>10⁶), and multi-bit storage capability (≥3 bits). Nevertheless, the device exhibited a limited retention time (~2000 s). To overcome this limitation, we developed a Gr-MoO₃-Ag heterostructure by substituting the Pd electrode with graphene (Gr). This modification achieved a fivefold improvement in the retention time (>10⁴ s). These findings demonstrate that by controlling the type and thickness of 2D materials and resistive switching layers, RRAM devices with both high On/Off ratios and long-term data retention may be developed. Full article

This paper proposes a dual-mode CMOS analog front-end (AFE) circuit for short-wave infrared (SWIR) image sensors, which integrates a hybrid readout circuit (ROIC) and a 12-bit two-step single-slope analog-to-digital converter (TS-SS ADC). The ROIC dynamically switches between buffered-direct-injection (BDI) and direct-injection (DI) modes, thus balancing injection efficiency against power consumption. While the DI structure offers simplicity and low power, it suffers from unstable biasing and reduced injection efficiency under high background currents. Conversely, the BDI structure enhances injection efficiency and bias stability via an input buffer but incurs higher power consumption. To address this trade-off, a dual-mode injection architecture with mode-switching transistors is implemented. Mode selection is executed in-pixel via a low-leakage transmission gate and coordinated by the column timing controller, enabling low-current pixels to operate in low-noise BDI mode, whereas high-current pixels revert to the low-power DI mode. The TS-SS ADC employs a four-terminal comparator and dynamic reference voltage compensation to mitigate charge leakage and offset, which improves signal-to-noise ratio (SNR) and linearity. The prototype occupies 2.1 mm × 2.88 mm in a 0.18 µm CMOS process and serves a 64 × 64 array. The AFE achieves a dynamic range of 75.58 dB, noise of 249.42 μV, and 81.04 mW power consumption. Full article

Solid oxide fuel cells (SOFCs) represent a pivotal technology in renewable energy due to their clean and efficient power generation capabilities. Their role in potential carbon mitigation enhances their viability. SOFCs can operate via a variety of alternative fuels, including hydrocarbons, alcohols, solid carbon, and ammonia. However, several solutions have been proposed to overcome various technical issues and to allow for stable operation in dry methane, without coking in the anode layer. To avoid coke formation thermodynamically, methane is typically reformed, contributing to an increased degradation rate through the addition of oxygen-containing gases into the fuel gas to increase the O/C ratio. The performance achieved by reforming catalytic materials, comprising active sites, supports, and electrochemical testing, significantly influences catalyst performance, showing relatively high open-circuit voltages and coking-resistance of the CH₄ reforming catalysts. In the next step, the operating principles and thermodynamics of methane reforming are explored, including their traditional catalyst materials and their accompanying challenges. This work explores the components and functions of SOFCs, particularly focusing on anode materials such as perovskites, Ruddlesden–Popper oxides, and spinels, along with their structure–property relationships, including their ionic and electronic conductivity, thermal expansion coefficients, and acidity/basicity. Mechanistic and kinetic studies of common reforming processes, including steam reforming, partial oxidation, CO₂ reforming, and the mixed steam and dry reforming of methane, are analyzed. Furthermore, this review examines catalyst deactivation mechanisms, specifically carbon and metal sulfide formation, and the performance of methane reforming and partial oxidation catalysts in SOFCs. Single-cell performance, including that of various perovskite and related oxides, activity/stability enhancement by infiltration, and the simulation and modeling of electrochemical performance, is discussed. This review also addresses research challenges in regards to methane reforming and partial oxidation within SOFCs, such as gas composition changes and large thermal gradients in stack systems. Finally, this review investigates the modeling of catalytic and non-catalytic processes using different dimension and segment simulations of steam methane reforming, presenting new engineering designs, material developments, and the latest knowledge to guide the development of and the driving force behind an oxygen concentration gradient through the external circuit to the cathode. Full article

This article introduces a high-efficiency, high-voltage-ratio bidirectional DC–DC converter based on the Dual-Active-Bridge (DAB) topology, specifically designed for applications involving low-voltage, high-capacity cells. Addressing the critical challenge of enhancing bidirectional power transfer efficiency under ultra-high step-up ratios, which is essential for integrating renewable energy sources and battery storage systems into modern power grids, an optimized control strategy is proposed. This strategy focuses on refining switching patterns and minimizing conduction losses to improve overall system efficiency. Theoretical analysis revealed significant enhancements in efficiency across various operating conditions. Simulation results further confirmed that the converter achieved exceptional performance in terms of efficiency at extremely high voltage conversion ratios, showcasing full-range Zero-Voltage Switching (ZVS) capabilities and reduced circulating reactive power. Specifically, the proposed method reduced circulating reactive power by up to 22.4% compared to conventional fixed-frequency control strategies, while achieving over 35% overload capability. These advancements reinforce the role of DAB as a key topology for next-generation high-performance power conversion systems, facilitating more efficient integration of renewable energy and energy storage solutions, and thereby contributing to the stability and sustainability of contemporary energy systems. Full article

We present the performance and application of a commercial off-the-shelf Si PIN diode (Hamamatsu S14605) as a charged particle detector in a compact ion beam system (IBS) capable of generating D–D and p–B fusion charged particles. This detector is inexpensive, widely available, and operates in photoconductive mode under a reverse bias voltage of 12 V, supplied by an A23 battery. A charge-sensitive preamplifier (CSP) is mounted on the backside of the detector’s four-layer PCB and powered by two ±3 V lithium batteries (A123). Both the detector and CSP are housed together on the vacuum side of the IBS, facing the fusion target. The system employs a CF-2.75-flanged DB-9 connector feedthrough to supply the signal, bias voltage, and rail voltages. To mitigate the high sensitivity of the detector to optical light, a thin aluminum foil assembly is used to block optical emissions from the ion beam and target. Charged particles generate step responses at the preamplifier output, with pulse rise times in the order of 0.2 to 0.3 µs. These signals are recorded using a custom-built data acquisition unit, which features an optical fiber data link to ensure the electrical isolation of the detector electronics. Subsequent digital signal processing is employed to optimally shape the pulses using a CR-RCⁿ filter to produce Gaussian-shaped signals, enabling the accurate extraction of energy information. Performance results indicate that the detector’s baseline RMS ripple noise can be as low as 0.24 mV. Under actual laboratory conditions, the estimated signal-to-noise ratios (S/N) for charged particles from D–D fusion—protons, tritons, and helions—are approximately 225, 75, and 41, respectively. Full article

This article presents an efficient non-isolated DC-DC hybrid converter for direct large-ratio step-down applications such as data centers. The converter topology employs a three-level-assisted Dickson switched capacitor network and interleaved dual inductors, significantly mitigating voltage swings at the switching nodes. As a result, the conduction duration of rectifying switches is substantially extended. This configuration is suitable for both odd- and even-order converters, achieving self-balancing of the flying capacitor voltages and inductor currents. To address uneven interleaved inductor currents, a duty-cycle-matching-based current distribution method is proposed to ensure equal current sharing and facilitate loss transfer between inductors. Additionally, an intrinsic charge-ratio-based method for capacitance optimization is introduced to achieve quasi-complete soft charging of the flying capacitors. This method eliminates surge currents during reconfiguration of the capacitor network, reduces losses, and enhances the capacitor utilization. Operating at 300 kHz, the prototype achieves high-ratio voltage conversion from 48 V to 0.5–2.0 V, with a maximum output current of 30 A. It attains a peak efficiency of 91.96% and a power density of 944.88 W/in³. Quasi-complete soft charging of the flying capacitors results in an approximate 2.94% improvement in the conversion efficiency. Full article

The exhaust purge on the anode side is a critical step in the operation of fuel cell systems, and optimizing the exhaust interval time is essential for enhancing stack efficiency and hydrogen utilization. This paper proposed a method to determine the purge strategy of hydrogen supply system based on theoretical and simulation analysis. To investigate the impact of anode purge strategy on the performance of automotive fuel cells, a model of a 100 kW fuel cell stack and a dual-ejector hydrogen supply system was developed in MATLAB/Simulink(R2022b) using principles of fluid dynamics, simulation, and experimental data. This model effectively captures the accumulation and exhaust of hydrogen, nitrogen, and vapor within the anode. Simulations were conducted under seven different exhaust interval times at varying current densities to study the effect of exhaust interval on the performance of the fuel cell. The results indicate that for a 100 kW fuel cell, the exhaust interval time should be controlled within 25 s and should decrease as the current density increases. At low current density, increasing the exhaust interval has a more significant effect on improving hydrogen utilization. At high current density, reducing the exhaust interval helps maintain a stable hydrogen excess ratio and shortens the time required for the output voltage to reach a stable state. Full article

This study introduces an enhancement-mode AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistor (MIS-HEMT) featuring a self-aligned p-GaN gate structure, fabricated using a gate-first process. The key innovation of this work lies in simplifying the fabrication process by utilizing gate metallization for both electrical contact and etching mask functions, enabling precise self-alignment. A highly selective Cl₂/N₂/O₂ inductively coupled plasma (ICP) etching process was optimized to etch the p-GaN layer in the access regions, with a selectivity ratio of 33:1 and minimal damage to the AlGaN barrier. Additionally, a novel, non-annealed ohmic contact formation technique was developed, leveraging ICP etching to create nitrogen vacancies that facilitate contact formation without requiring thermal annealing. This technique streamlines the process by combining ohmic contact formation and mesa isolation into a single lithographic step. Incorporating a SiNx gate dielectric layer led to a 4.5 V threshold voltage shift in the fabricated devices. The resulting devices exhibited improved electrical performance, including a wide gate voltage swing (>10 V), a high on/off current ratio (~10⁷), and clear pinch-off characteristics. These results demonstrate the effectiveness of the proposed fabrication approach, offering significant improvements in process efficiency and manufacturability. Full article

Series–series (SS) wireless power transfer (WPT) systems are used in many applications because of their simple circuit structure. Compared with higher-order complex compensation topology, they are suitable for more demanding applications, such as rail trams with high power requirements but limited space for the coupling mechanism. However, the characteristics of their voltage source also put forward higher requirements for the control strategy. Improving the dynamic response performance of an SS compensation WPT system without any communication between the primary and secondary sides is the key issue. This paper proposes an improved variable step-size maximum power point tracking control strategy with the mutual inductance identification. Compared with the conventional P&O control, it can achieve a faster response and more accurate tracking, which are very important to the WPT for rail transit. A method of the mutual inductance identification based on the weight of parameter sensitivity is proposed. Based on the results of the identified mutual inductance, to make the system transfer the maximum power, the duty ratio of the receiver is adjusted to approach the corresponding equivalent load. To deal with the change of the mutual inductance, a condition of terminating the searching process of the maximum power point and re-identifying the mutual inductance is proposed. A simulation and experimental platform is built for verification. The results show that the proposed control strategy can quickly respond to the variation of the mutual inductance and load and achieve accurate maximum power point location, which improves the performance of the SS compensation WPT system. Full article

In this article, a new high step-up interleaved DC–DC converter is presented for renewable energy systems. The converter circuit is based on the interleaved two-phase boost converter and integrates a voltage-lift capacitor and a voltage multiplier cell. A high voltage gain of the converter can be achieved with a reasonable duty ratio and the voltage stresses of semiconductor devices are reduced. Because of low voltage stress, the switches with low on-resistance and the diodes with low forward voltage drops can be adopted to minimize the conduction losses. Additionally, the switching losses are reduced because the switches are turned on under zero-current switching (ZCS) conditions. Due to the existence of leakage inductances of the coupled inductors, the diode reverse-recovery problem is alleviated. Moreover, the leakage energy is recycled and the voltage spikes during switch turn-off are avoided. The parallel input architecture and interleaved operation reduce the input current ripple. The operating principles, steady-state characteristics, and design considerations of the presented converter are proposed in detail. Furthermore, a closed-loop control is designed to maintain a well-regulated output voltage despite variations in input voltage and output load. A prototype converter with a rated 1000 W output power is realized for demonstration. Finally, experimental results show the converter effectiveness and verify the theoretical analysis. Full article

Microrobots, characterized by their small size, flexibility, and portability, have a diverse range of potential applications. However, microrobots’ actuation (piezoelectric ceramics, dielectric elastomers, ion winds, etc.) often requires a high voltage, typically hundreds of volts. The lithium niobate transformer (LNT), a piezoelectric voltage transformer, presents a promising solution for miniaturizing high-voltage power supplies due to its compact size, low weight, and high step-up ratio. This study explores the effects of structural parameters and external circuits on the resonant frequency and step-up ratio of the LNT through numerical simulations and experiments. The results indicate the following: (1) the second-order longitudinal vibration frequency of the lithium niobate (LN) plate inversely correlates with its length; (2) the thickness and width of the plate have minimal impact on the frequency; (3) the step-up ratio increases as the plate thickness decreases. The experimental results suggest that LN plates with a thickness of 1 mm are preferable due to the fragility of 0.5 mm plates, especially at the output end. Additionally, optimizing the input circuit enhances voltage amplification, allowing the LNT to generate sufficient output voltage for corona discharge. These findings highlight the potential of LNTs for efficiently and reliably powering small-scale devices. Full article

An innovative analog frontend for big data collection and intelligent compression as part of an instantaneous failure prediction platform is presented. Failure prediction in power management systems is crucial for increasing uptime and preventing massive failure. Accurate failure prediction, with real-time decision-making, requires data collection from many wide-bandwidth signals within a system, as low-bandwidth information such as DC output voltage is of limited value for decision-making and failure prediction. Analog compression, data profiling, and anomaly detection methods enabled by the unique analog frontend are presented. The system significantly reduces the demand for high computational power, fast communication, and large storage space required for the task. A real-time compression ratio exceeding 100:1 was achieved by the experimental analog frontend, digitizing the analog signal at a rate of 135 MS/s with a 10-bit resolution. The motivation, existing solutions, performance metrics, and advantages of the analog frontend are demonstrated, along with the details of the circuit operation principle. The process of data collection, its intelligent processing using the analog frontend, and anomaly detection are simulated to validate the theoretical hypotheses. For experimental validation, a laboratory setup that includes a dedicated analog frontend prototype and step-down DC-DC converter was built and evaluated to demonstrate the robust performance in sampling and monitoring wide-bandwidth signals and smart data processing using analog frontend for quick decision-making. Full article

Fuel cells (FCs) offer several operational advantages when integrated as a power source in electric vehicles (EVs). Since the voltage of these cells is typically low, usually less than 1 V, the power conversion system requires a DC–DC converter capable of providing a high voltage conversion ratio to match the input voltage of the motor propulsion system, which can exceed 400 V and reach up to 800 V. The modular DC–DC boost converter proposed in this paper is designed to achieve a high voltage step-up ratio for the input FC voltages through the use of isolated series-connecting boosting submodules connected. The power electronic topology employed in the submodules (SMs) is designed to provide a flexible output voltage while maintaining a continuous input current from the fuel cells with minimal current ripple to improve the FC’s performance. The proposed step-up modular converter provides several benefits including scalability, better controllability, and improved reliability, especially in the presence of partial faults. Computer simulations using MATLAB/SIMULINK^® software (R2024a) have been used to study the feasibility of the proposed converter when connected to a permanent magnet synchronous motor (PMSM). Also, experimental results using a 1 kW prototype composed of four SMs have been obtained to validate the performance of the proposed converter. Full article

This paper presents a novel high-precision 11-bit single-slope/successive approximation register analog-to-digital converter (SS/SAR ADC) architecture specifically designed for CMOS image sensors (CISs). The proposed design solves critical challenges in conventional ADCs by utilizing only two reference voltages, thereby minimizing voltage mismatch and completely eliminating the need for complex switch arrays. This unique approach reduces the transistor count by 64 per column ADC, significantly enhancing area efficiency and circuit simplicity. Furthermore, a groundbreaking on-chip fine step range calibration technique is introduced to mitigate the impact of parasitic capacitance, ensuring the precise alignment between coarse and fine steps and achieving exceptional linearity. Fabricated using a 0.18-µm CMOS process, the ADC demonstrates superior performance metrics, including a differential nonlinearity (DNL) of −1/+1.86 LSB, an integral nonlinearity (INL) of −2.74/+2.79 LSB, an effective number of bits (ENOB) of 8.3 bits, and a signal-to-noise and distortion ratio (SNDR) of 51.77 dB. Operating at 240 kS/s with a power consumption of 22.16 µW, the ADC achieves an outstanding figure-of-merit (${\mathrm{FOM}}_W$) of 0.291 pJ/step. These results demonstrate the proposed architecture’s potential as a transformative solution for high-speed, energy-efficient CIS applications. Full article

This paper presents an isolated DC-DC converter with high voltage gain that features an advanced inter-built nanocrystalline-core medium-frequency transformer (NC-MFT). The isolated DC-DC converter with an NC-MFT is specifically designed for applications such as interconnect photovoltaic (PV) systems, DC microgrids, DC loads, and DC buses, where voltage gain is one of the essential issues to consider. The NC-MFT inside the DC-DC converter is designed with a new approach that not only provides isolation but also contributes to achieving high efficiency and a higher step-up ratio. The high efficiency of the converters contributes to the integration of PV systems into DC microgrids. The converter yields a high voltage conversion ratio of 16.17. The experimental results obtained at 41.8 V/676 V and 275 W for the prototype revealed high efficiency (95.63% at full load). The experimental results validate the theoretical analysis and simulation, confirming that the converter achieves the main objective of high voltage conversion and high efficiency. These results will contribute to the interest in the use of this type of energy and its impact on the reduction in CO₂ emissions. Full article