Power Devices Research Articles

Recent Advanced Ultra‐Wide Bandgap β‐Ga2O3 Material and Device Technologies

AbstractGallium oxide (Ga2O3) is an emerging ultra‐wide bandgap (UWBG) semiconductor material that has gained significant attention in the field of high voltage and high frequency power electronics. Its noteworthy attributes include a large bandgap (Eg) of 4.8 eV, high theoretical critical breakdown field strength (EC) of 8 MV cm−1, and saturation velocity (νs) of 2 × 107 cm s−1, as well as high Baliga figures of merit (BFOM) of 3000. In addition, Ga2O3 has the advantages of large‐size substrates that can be achieved by low‐cost melt‐grown techniques. This review provides a partial overview of pivotal milestones and recent advancements in the Ga2O3 material growth and device performance. It begins with a discussion of the fundamental material properties of Ga2O3, followed by a description of substrate growth and epitaxial techniques for Ga2O3. Subsequently, the contact technologies between Ga2O3 and other materials are fully elucidated. Moreover, this article also culminates with a detailed analysis of Ga2O3‐based high voltage and high frequency power devices. Some challenges and solutions, such as the lack of p‐type doping, low thermal conductivity, and low mobility are also presented and investigated in this review.

Conceptual design of a high reactive-power ferroelectric fast reactive tuner

We present a novel design of a ferroelectric fast reactive tuner (FE-FRT) capable of modulating mega-VAR reactive power on a submicrosecond timescale. The high reactive power capability of our design extends the range of applications of reactive tuners to numerous applications. We present a detailed analytical model of the performance of a megawatt-class reactive power device and benchmark it against finite-element method eigenmode and frequency domain electromagnetic simulations. We introduce new features, including an annulus design for the ferroelectric capacitors and capacitive window coupling to the cavity. We consider thermal design issues and nonlinear effects in the ferroelectric. The model covers several configurations, allowing control of the frequency of superconducting and normal-conducting cavities in a variety of applications and frequencies. We calculate that the FE-FRT designed should be capable of handling around 0.45 MVAR of reactive power with around 3 kW of resistive losses, providing a frequency tuning range of 8 kHz in an example of 400 MHz cavity geometry. Published by the American Physical Society 2024

Real-world clinical outcome related to veno-arterial extracorporeal membranous oxygenator: a single-center experience

Abstract Funding Acknowledgements None. Background Veno-arterial extracorporeal membranous oxygenator (VA-ECMO) is one of the most powerful devices that rapidly restore sufficient organ perfusion in patients with cardiogenic shock. Despite abundant experiences of successful resuscitation with VA-ECMO, evidences for clinical benefit of VA-ECMO are still lacking. Purpose We summarised clinical outcomes related to VA-ECMO and investigated predictors regarding survival at discharge. Methods Patients who treated with peripheral VA-ECMO between 2006 and 2022 were included from a Hospital in South Korea. Eligible patients were analysed in stratification with ECMO initiation year (year 2006–2010, year 2011–2016, and year 2017–2022). Survival status at discharge were investigated. Results Among total of 693 patients included, 223 (32.2%) were survived at discharge. Survivors had stayed in hospital for median 28 (19–52) days. The overall volume of ECMO initiation (86 runs vs. 250 runs vs. 357 runs) and the rate of extracorporeal CPR (3.5% vs. 18.4% vs. 38.1%) have increased over time. The median duration of VA-ECMO treatment has increased over time (52.6 hours vs. 63.6 hours vs. 85.8 hours). The serum lactate test has been performed more frequently over time (15.1% vs. 79.6% vs. 99.2%). Among 470 patients who died in the index hospitalization, 154 (32.8%) patients died in the first 24 hours after initiation of VA-ECMO. In a multivariate regression model, age over 70 (OR, 0.54; 95% CI, 0.32–0.89), extracorporeal CPR (OR, 0.42; 95% CI, 0.24–0.71), and lactate level ≥8.0 mmol/L (OR, 0.24; 95% CI, 0.15–0.37) were associated with unfavorable outcome while hemoglobin was a predictor of favorable clinical outcome (OR, 1.16; 95% CI, 1.07–1.25). Conclusion The volume of VA-ECMO has increased and clinical severity has also become higher than before. The rate of survival at discharge after VA-ECMO treatment remains stable; however, the rate of patients who died in the first 24 hours is still high. Age, extracorporeal CPR, hemoglobin and lactate levels were predictors of clinical outcome after VA-ECMO treatment.

Development of Ag@Si composite sinter joining with ultra-high resistance to thermal shock test for SiC power device: Experiment validation and numerical simulation

Owing to its cost-effectiveness and low coefficient of thermal expansion (CTE), micron Si is incorporated into sintered Ag matrix to develop an Ag@Si composite sintering strategy. The Si integration helps reduce cost and alleviate CTE-mismatch of Ag-sintered die attachments. An innovative Ag@Si composite sintering structure is achieved by low-temperature and pressure-less sintering process, where a possibly slight diffusion of native SiO2 on the Si surface toward Ag is indicated by TEM observation, enabling the integration of Ag and Si into one continuous network. Owing to the robust well-bonded composite sintering, the Ag@Si joining strategy provides mechanical/microstructural reliability far beyond the pure Ag sinter joining, demonstrating significant prospects in high-temperature interconnection applications. During the harsh thermal cycling (−50–250 °C), the mitigating effect of the Si addition on CTE mismatch is manifested through the substantial suppression of microstructure deterioration in Ag@Si joint that occurs in pure-Ag-sintered joint, while the shear strength retention rate is doubled. Detailed investigation into the mechanism for elevated performance was conducted by material property and Missies stress analysis. The incorporation of Si helps modify the CTE, elastic properties, and stress distribution of Ag@Si-sintered material, synergistically contributing to the satisfactory joining reliability.

Synaptic properties of GaOx-based memristor with amorphous GaOx deposited by RF magnetic sputtering

GaOx devices have been extensively explored for applications such as power devices and solar blind detectors, based on their wide bandgap. In this study, we investigated the synaptic properties of the amorphous gallium oxide (a-GaOx)- based memristor with a W/WOx/a-GaOx/ITO structure, in which a-GaOx are deposited by RF magnetic sputtering at ambient temperature. The structure and components of a-GaOx are characterized by XRD, XPS, SEM, and EDS. The electrical test indicates that W/WOx/a-GaOx is ohmic due to the thin WOx layer with a high concentration of oxygen vacancies. Consequently, the synaptic characteristics of the W/WOx/a-GaOx/ITO memristor depend on both the a-GaOx layer itself and the a-GaOx/ITO junction. The fitting results indicate that the a-GaOx/ITO junction is Schottky with unidirectional conductive properties. However, the elevated defect density results in a larger current for the reverse-biased a-GaOx/ITO junction. Moreover, adjusting the thickness of a-GaOx allows the device to achieve almost symmetrical forward and reverse currents. We have successfully observed typical synaptic characteristics in W/WOx/a-GaOx/ITO when stimulated by consecutive spike signals. Clearly, through careful design considerations regarding the structure and parameters, we have realized superior synaptic performance in a-GaOx-based memristors. This achievement shows that amorphous GaOx has great potential applications in neuromorphic computation chips for artificial intelligence or the Internet of Things in the future.

Design of Glider Wing Shape and Research on its Aerodynamic Characteristics

The glider is a type of aircraft without a power device, which relies on airflow to obtain forward power and has important application value in environmental detection, rescue, and other scenarios. The wing shape of a glider is one of the biggest factors affecting its gliding performance. However, the quantitative mechanism by which specific airfoil parameters affect gliding performance is still unclear. This paper dives into the field of aerodynamics and analyzes which airfoil performs the best in realistic situations. Unlike traditional methods in which the only way to analyze such a foil is through rigorous testing in a wind tube, this paper uses two ways, both through simulation and idealized calculation to determine the best airfoil. The results demonstrate that the lift-to-drag ratio characteristics of NACA 4424 and NACA 4415 are better than those of NACA 64A210 and NACA 2412, but there is a certain difference between the simulation results and theoretical results, which may be related to the accumulated errors in the simulation and data processing processes. This study helps to enhance the understanding of the impact of different airfoil parameters on their aerodynamic performance, providing a reference for the optimization design of airfoils.

Aerodynamic Characterization of Glider Lift-to-drag Ratio and its Wing Shape

As a type of fixed-wing aircraft without power devices, gliders have important value in aviation measurement, cargo transportation, and other scenarios. This article studies the application of aerodynamics and fluid dynamics in gliders, but the wing shape of a glider is not sufficient to provide sufficient aerodynamic characteristics for the glider. Therefore, based on the basic theory of aerodynamics, this article studies the relationship between the lift-to-drag ratio of a glider and the aerodynamic characteristics of its wing shape in the aviation field, and changing the shape of the wings to alter the difference in air pressure between the upper and lower air during the glider's flight. Furthermore, the force exerted on the glider during flight is altered to maintain its altitude and flight time. Different airfoils to find out which one can make the glider fly farther, safer, and at higher altitudes were tested. Finally, based on this study, the conclusion drawn is that the double convex wing shape can provide higher overall efficiency and stability for gliders during flight, despite its high cost. This study provides important references for the study of aerodynamic efficiency and stability of gliders.

Vertical Schottky diode on (113) oriented homoepitaxial diamond

Vertical Schottky diodes were fabricated on (113) oriented diamond substrates produced from thick heavily boron doped (NA ∼ 3.5 × 1020 cm−3) diamond layers grown on HPHT-grown synthetic Ib diamond crystals. The p+-substrates were overgrown by a low doped p-epilayer whose surface layer was compensated up to the depth of 0.1 to 0.3 μm. The surface was then oxygen terminated and covered by evaporated Mo/Au Schottky contacts. The bottom ohmic contact to p+-substrate was formed by Ti/Au bi-layer. Current- and capacitance-voltage characteristics of the realized diodes were measured at temperatures ranging from 25 to 180 °C. At room temperature, the realized diodes show high forward current densities JF = 100 A/cm2 and low differential ON-state specific resistance Ron_sp = 3.7 mΩ.cm2 at forward voltage VF = 4 V and a very low leakage (JR < 10−9 A/cm2) in the blocking regime. At 180 °C, forward characteristics significantly improve (JF = 5 kA/cm2, Ron_sp = 0.2 mΩ.cm2 at VF = 4 V) while the blocking characteristics remain almost unchanged (JR = 6 × 10−8 A/cm2 at VR = 4 V). The breakdown electric field is about 3 MV/cm and the rectification ratio keeps at the level of 1011. Characteristics of realized diodes, which are fully comparable to those of Schottky-pn diodes prepared on (111) oriented boron doped diamond, confirm the suitability of (113) orientation for realization of vertical diamond power devices.

Application of artificial intelligence in the diagnosis and treatment of cardiac arrhythmia.

The rapid growth in computational power, sensor technology, and wearable devices has provided a solid foundation for all aspects of cardiac arrhythmia care. Artificial intelligence (AI) has been instrumental in bringing about significant changes in the prevention, risk assessment, diagnosis, and treatment of arrhythmia. This review examines the current state of AI in the diagnosis and treatment of atrial fibrillation, supraventricular arrhythmia, ventricular arrhythmia, hereditary channelopathies, and cardiac pacing. Furthermore, ChatGPT, which has gained attention recently, is addressed in this paper along with its potential applications in the field of arrhythmia. Additionally, the accuracy of arrhythmia diagnosis can be improved by identifying electrode misplacement or erroneous swapping of electrode position using AI. Remote monitoring has expanded greatly due to the emergence of contactless monitoring technology as wearable devices continue to develop and flourish. Parallel advances in AI computing power, ChatGPT, availability of large data sets, and more have greatly expanded applications in arrhythmia diagnosis, risk assessment, and treatment. More precise algorithms based on big data, personalized risk assessment, telemedicine and mobile health, smart hardware and wearables, and the exploration of rare or complex types of arrhythmia are the future direction.

Short-voltage pulse generation for induction heating load detection on a multi-output inverter with shared power devices

Purpose The purpose of this paper is to develop a load detection method for domestic induction cooktops. The solution aims to minimize its impact in the converter power transmission while enabling the estimation of the equivalent electrical parameters of the load. This method is suitable for a multi-output resonant inverter topology with shared power devices. Design/methodology/approach The considered multi-output converter presents power devices that are shared between several loads. Thus, applying load detection methods in the literature requires a halt in the power transfer to ensuring safe operation. The proposed method uses a complementary short-voltage pulse to excite the induction heating (IH) coil without stopping the power transfer to the remaining IH loads. With the current through the coil and the analytical equations, the equivalent inductance and resistance of the load is estimated. The precision of the method has been evaluated by simulation, and experimental results are provided. Findings The measurement of the current through the induction coil as a response to a short-time single-pulse voltage variation provides enough information to estimate the load equivalent parameters, allowing to differentiate between no-load, non-suitable IH load and suitable IH load situations. Originality/value The proposed method provides a solution for load detection without requiring additional circuitry. It aims for low power transmission to the load and ensures zero-voltage switching and reduced peak current even in no-load cases. Moreover, the proposed solution is extensible to less complex converters, as the half bridge.

Critical solder joint in insulated gate bipolar transistors (IGBT) power module for improved mechanical reliability

This investigation identifies the critical solder joint in a typical Insulated Gate Bipolar Transistor (IGBT) module and provided new knowledge on how operating thermal loads degrade IGBT-attach, Diode-attach, and Substrate solder joints in the device. SolidWorks software is used to create three realistic 3-D Finite Element (FE) models of the typical IGBT module used in this investigation. In-service operating power and IEC 60068–2-14 thermal cycles are implemented in ANSYS mechanical package to simulate the response of the three solder joints in the FE models to the load cycles. The solder in the joints is lead-free alloy of 96.5% tin, 3% silver, and 0.5% copper (SAC305) composition. The SAC305 material properties are modelled as time and temperature dependent with Anand's visco-plastic model employed as the constitutive model. Results show that the key degradation mechanism of solder joints in IGBT module are stress, plastic strain, and strain energy magnitudes. Accumulated plastic strain in the joints is found the predominant damage factor. Critical solder joint in the module depends on the load cycle the device experiences. IGBT-attach solder joint is critical in active power load cycle. Substrate solder joint degraded most in passive thermal cum combined passive thermal and active power load cycles.

Zinc tungstate integrated onto zinc oxide h-MDs-based flexible piezoelectric power device: A new energy technology for real-time indoor laboratory safety warning system

With the rapid development of research world, the number of researchers and research laboratories is increasing rapidly. Simultaneously, accidents in laboratories are on the rise, drawing significant attention from everyone. To address this issue, the current study demonstrates a real-time safety early warning alarm system aimed at preventing accidents and enhancing safety management in laboratories. We developed a zinc tungstate nanoparticles (NPs) integrated on zinc oxide hexagonal microdiscks (h-MDs) (ZnO–ZnWO4@PDMS) composite based on a novel flexible piezoelectric nanogenerator (FPENG). The observed piezoelectric response was 1.32 V, which is ∼4 times better than that of pure ZnWO4, owing to the synergistic effect of ZnO–ZnWO4@PDMS. When subjected to finger-tapping motion, the FPENG can charge a 1 μF capacitor, and it reached 81 mV within 56 s. Subsequently, the light-emitting diodes (LEDs) are powered with amplification. The FPENG system was demonstrated and validated through real-time application in the laboratory setting, marked as a “caution/restricted” line. The application of the system demonstrated its capability to simultaneously illuminate LEDs and sound alarms when people touch or cross the caution line. Furthermore, the proposed FPENG exhibited ∼660 mV even ∼90 % humidity, with no noticeable electrical changes under different solvents, confirming that the proposed FPENG is not affected by varying humidity and various indoor conditions. These outstanding results and real-time demonstrations unequivocally establish the feasibility of this system in contexts such as bank lockers, metro systems, hilly areas, and more.

Reinforcement learning-driven proximal policy optimization-based voltage control for PV and WT integrated power system

The depletion of conventional fuel reserves and the high carbon emissions have alarmed the energy sector drivers. The integration of renewable energy resources (RERs) towards power system transformation is an obvious approach for a new-zero future. However, this integration also brings challenges in terms of voltage stability and power losses due to the variable output of RERs. To address these challenges, this work proposes a novel approach utilizing photovoltaic (PV) inverters and static var compensators (SVCs) for reactive power control in power distribution networks (PDNs). It enhances voltage stability and minimizes power losses. The proposed study deploys a proximal policy optimization (PPO) algorithm for real-time communication and control between reactive power devices. Performance evaluation was made on an IEEE-33 Bus system to demonstrate the effectiveness of the proposed scheme in integrating RER-based distributed generators (DGs). The proposed system achieved 68 % voltage control, keeping the voltage within a certain range of ±5 % while minimizing power losses. The proposed system also reduced the voltage out-of-control ratio to 0.044, which indicates minimum voltage deviation from the standard value. The proposed study provides a promising solution for controlling the voltage of DGs integrated PDN, which can potentially enhance the efficiency and reliability of the power system.

Hyper‐parameter optimized GPR model based on chaos game algorithm for RF power transistors

AbstractIn this paper, a new frequency domain behavior model for radio frequency (RF) power transistors based on a hyper‐parameter optimized Gaussian process regression (GPR) method is presented. The chaos game optimization (CGO) algorithm is used to optimize GPR hyperparameters, resulting in the CGO‐GPR model. The basic theory as well as the details of the modeling process are presented. Validation of the model is conducted using a 10‐watt GaN power transistor. Compared to the standard GPR model, the proposed model achieved a significant improvement. Furthermore, the comparison with the particle swarm optimization (PSO) based GPR model (PSO‐GPR) showed that the proposed model allows achieving superior performance, thereby confirming the effectiveness of the developed modeling technique.

ДОСЛІДЖЕННЯ МЕТОДУ ФРАКТАЛЬНОГО СТИСНЕННЯ ЗОБРАЖЕНЬ З МЕТОЮ ПОКРАЩЕННЯ ЯКОСТІ СТИСНЕННЯ

The development of the Internet, along with the availability of increasingly powerful computers and other digital devices, cameras, scanners and printers, has led to the wide-spread use of digital images. In this regard, interest in improving data compression algo-rithms, such as images, is growing. Data compression is important for both transfer speed and storage efficiency. In addition to many commercial uses, compression technologies are also of interest in the military industry, such as applications for processing telemetry data from missile inter-ceptors or for archiving terrain image data for defense simulations. Solving the problem of image compression, or, more generally, image coding, has used advances and stimulated the development of many fields of engineering and math-ematics. The article examines fractal image compression — a data compression method based on the use of self-similar patterns in an image. This method allows you to achieve a high degree of compression while preserving image details. Fractal image compression is a unique and efficient approach to data compression based on the mathematical theory of fractals. Nowadays, it has important applications and advantages that make it a valuable tool in image processing. The main advantages include: 1. Preservation of details during compression. One of the key advantages of fractal compression is its ability to preserve a high degree of image detail in a relatively small amount of storage. This is especially important in situations where image quality must be preserved with limited storage and data transfer resources. 2. Efficiency of transmission through the network. Fractal compression allows for compact images, making it suitable for image transmission over a low-bandwidth network. This is especially true for mobile devices, the Internet of Things, and other scenarios where high bandwidth is not always available. 3. Adaptive compression for different resolutions. Fractal compression allows you to adapt the level of compression depending on the resolution and details of the image. This means that it can be used to compress various image sizes without significant loss of quality. 4. Data archiving and storage. Fractal compression can be useful for archiving and long-term storage of images, as it allows you to effectively reduce the amount of data without losing important information. This is especially important for libraries, archives, research databases and other data repositories. Fractal image compression remains a relevant and valuable tool in today's envi-ronment, thanks to its ability to efficiently compress, preserve details, and adapt to dif-ferent usage scenarios. Therefore, the study of its efficiency, the optimization of the soft-ware code to obtain a faster and better compression result, is an urgent task.

Optimizing Wireless Sensor Networks through Ant Colony-Based Localized Mesh Topology

The growing need for faster and more effective data handling and data transfer capabilities of a network require energy-efficient and more powerful smart sensor devices. These devices have become increasingly necessary in wireless sensor networks (WSN). The architecture or topology of WSN can greatly impact the organizational efficacy and connectivity among the sensor nodes employed within the given area. It is foremost important to implement a robust network topology which must be capable of ensuring continuous and reliable communication within the whole network. This research paper presents an effective approach based on Ant colony scheme to optimize mesh network topology ant colony optimization (ACO) is used to place the sensor nodes optimally in the given area of the whole network. The proposed research carries out comprehensive performance evaluation of the network under various QoS parameters such as bandwidth, throughput, delay, residual energy and routing load. These parameters shows the effectiveness or adaptability of the network with different and dynamically changing communication requirements suggested by this topology scheme. The network based on the proposed method has been simulated several times and the achieved simulation patterns have been analyzed under the mentioned QoS constraints.

A novel energy efficient 4-bit vedic multiplier using modified GDI approach at 32 nm technology

Multipliers are essential components within digital signal processing, arithmetic operations, and various computational tasks, making their design and optimization crucial for improving the efficiency and performance of integrated circuits. Among multiplier architectures, Vedic multipliers stand out due to their inherent efficiency and speed, derived from ancient Indian mathematical principles. This study presents a comprehensive analysis and comparison of 4-bit Vedic multiplier designs utilizing Gate Diffusion Input (GDI), Complementary Metal-Oxide-Semiconductor (CMOS), and Transmission Gate (TG) technologies, utilizing different adder architectures such as Ripple Carry Adder (RCA), and Carry Lookahead Adder (CLA), Carry Skip Adder (CSA). The objective is to explore the performance, area, and power consumption characteristics of these multipliers across different technologies and adder implementations. Each multiplier architecture is meticulously designed and optimized to leverage the unique features of the respective technology while adhering to the principles of Vedic mathematics. The designs are evaluated based on parameters such as transistor count, delay, power dissipation, and area. The results demonstrate the effectiveness of GDI technology in terms of in tems of delay, area, power and PDP when compared with other technologies. The 4-bit Vedic multiplier has been designed using 32 nm technology within Tanner EDA software tools.

A Noncontact Method for Simultaneous Measurement of di/dt and dv/dt

This letter proposes a non-contact method for simultaneously measuring the current and voltage change rates by Rogowski coils. The dv/dt measurement capability is achieved based on electric field coupling, which is incorporated into the state-of-the-art Rogowski coil based current sensing solutions. The application of the proposed method for power semiconductor devices is demonstrated by a case study of an IGBT switching circuit. The Rogowski coils are integrated with a Printed Circuit Board (PCB) and fit with the IGBT module terminals. The comparable results from high-performance commercial instruments verify the di/dt and dv/dt measurement accuracy of the presented compact and cost-effective solution.

Demonstration of a simple and efficient design methodology for high‐voltage floating field limiting ring in SiC power devices

AbstractThis letter, proposes and experimentally demonstrates a simple and efficient estimating method for high‐voltage floating field ring (FFR). Four rings in FFR are used to determine the influence of rings’ distance (d) on the voltage drops of the highest voltage to the third ring (Vn+1) and the third to the second ring (Vn). Then, two voltage curves (curves for Vn+1 and Vn) based on d are drawn. For a target breakdown voltage, by iterating between the curves for Vn+1 and Vn, the number of FFRs and corresponding distances can be found. Based on this method, an 8.0 kV PN diode with 111 FFRs is designed and fabricated. The measured breakdown voltage is 7840 V, which reaches 98% of the designed value. This method provides a simple and efficient design for high‐voltage SiC devices, especially for ultra‐high voltage applications where the number of rings exceeds dozens.

Gate Voltage Oscillation Mitigation in Solid-State Circuit Breakers With Single-Gate Driven Series-Connected Power Devices

Gate Voltage Oscillation Mitigation in Solid-State Circuit Breakers With Single-Gate Driven Series-Connected Power Devices