Low Voltage Characteristics Research Articles

Power Flow and Generator-Converter Schemes Studies in Ship MVDC Distribution Systems

The medium-voltage dc (MVDC) distribution system is a new shipboard power distribution technology that has been extensively discussed and studied by many shipbuilding corporations and ship-owners in recent years. As different types of power converters and ac and dc power distributions simultaneously involved in the system, the system performance for different connections of generators to MVDC converters under varying steady-state operating conditions is essential and important in the design stage of the electrical power distribution system. This type of problem can be analyzed by performing power flow studies. This paper aims presenting a methodology for power flow studies in ship MVDC distribution systems for system planning purpose. A power flow model of the power converters in steady-state is derived to consider medium and low voltage characteristics of electric power system on this type of ship. An ac/dc power flow solution approach then is developed to incorporate ac-system and dc-system models and the ac/dc interface buses in the analysis for determining an appropriate connection of generators and MVDC converters and power converter setting values. Test results of two alternatives for the direct connection of generators to MVDC converters under varying steady-state operating conditions are presented and compared to determine the proper generator-power converter scheme.

Autonomous Flyback Converter for Energy Harvesting from Microbial Fuel Cells

Cover letter An autonomous flyback converter was designed for energy harvesting from Microbial Fuel Cells (MFCs). The circuit was optimized to minimize the losses and maximize the efficiency. A Maximum Power Point Tracking (MPPT) algorithm was implanted in the converter to extract the maximum power available from MFC. Discontinuous conduction mode operation of the flyback allows controlling the MPP operation by impedance matching. The flyback can start-up at low voltage, around 300 mV. The output open circuit voltage is about 20 V and the voltage at MPP is 6.4 V with a maximum efficiency of 71.2%. Abstract: Microbial fuel cells (MFCs) use bacteria as the catalysts to oxidize organic matter and generate electricity. This energy can be used to supply low power electronic systems. A power management unit between the MFCs and the load is required to adapt the voltage and control the operation. The low voltage and low power characteristics of MFCs prohibit the use of standard converter topologies since the threshold voltage of standard CMOS transistors in CMOS technology is higher than the output voltage of MFCs. A low-voltage start-up sub-circuit is required to charge a primary capacitor to supply the driver. A specific sub-circuit is also required to control the operation of MFCs for Maximum Power Point Tracking (MPPT) issues. An optimized Discontinuous Conduction Mode (DCM) autonomous flyback converter for energy harvesting is presented for ambient sources, like MFCs. The converter is designed, fabricated, and tested. An MPPT algorithm is integrated in the system to control the operation and to extract the maximum available power from the MFC. The converter is able of start and step-up MFC output voltage to a value higher than 3 V under load. The peak efficiency of the converter is 71.2%.

Performance Improvement of Pi-gate SOI MOSFET Transistor using High-k Dielectric with Metal Gate

ABSTRACTPi-gate silicon-on insulator (SOI) MOSFET transistors have emerged as novel devices due to its simple architecture and better performance, better control over short-channel effects, and reduced power dissipation due to reduced gate leakage currents. As the oxide thickness scales below 2 nm, leakage currents due to tunnelling increase drastically, leading to high power consumption and reduced device reliability. Replacing the SiO2 gate oxide with a high-k material allows increased gate capacitance without the associated leakage effects. In this paper, we present the results of a 3D numerical simulation of the Pi-gate SOI MOSFET transistor. 3D device structure, based on the technology SOI is described and simulated by using SILVACO TCAD tools, and we compare the electrical characteristics results for titanium nitride (TiN) fabricated on Al2O3 (k ∼ 9), HfO2 (k ∼ 20), and La2O3 (k ∼ 30) gate dielectric. Excellent dielectric properties such as high-k constant, low leakage current, threshold voltage, and electrical characteristics were demonstrated. From the simulation result, it was shown that HfO2 is the best dielectric material with metal gate TiN.

Wearable non-volatile memory devices based on topological insulator Bi2Se3/Pt fibers

Pt fibers (15 μm) were coated with topological insulator Bi2Se3 nanoplates via a single mode microwave-assisted synthesis technique. With the Bi2Se3/Pt fibers, flexible memory devices were facilely assembled, and they were demonstrated to exhibit rewritable nonvolatile resistive switching characteristics of low switching voltage (−1.2 V and +0.7 V), high ON/OFF current ratio (106), and good retention (4500 s), showing the potential application in data storage. The resistive switching mechanism was analyzed on the bases of formation and rupture of conductive filaments.

0.5 V and 0.43 pJ/bit Capacitive Sensor Interface for Passive Wireless Sensor Systems.

This paper presents an ultra low-power and low-voltage pulse-width modulation based ratiometric capacitive sensor interface. The interface was designed and fabricated in a standard 90 nm CMOS 1P9M technology. The measurements show an effective resolution of 10 bits using 0.5 V of supply voltage. The active occupied area is only 0.0045 mm and the Figure of Merit (FOM), which takes into account the energy required per conversion bit, is 0.43 pJ/bit. Furthermore, the results show low sensitivity to PVT variations due to the proposed ratiometric architecture. In addition, the sensor interface was connected to a commercial pressure transducer and the measurements of the resulting complete pressure sensor show a FOM of 0.226 pJ/bit with an effective linear resolution of 7.64 bits. The results validate the use of the proposed interface as part of a pressure sensor, and its low-power and low-voltage characteristics make it suitable for wireless sensor networks and low power consumer electronics.

Voltage balancing strategies for serial connection of microbial fuel cells

The microbial fuel cell (MFC) converts electrochemically organic matter into electricity by means of metabolisms of bacteria. The MFC power output is limited by low voltage and low current characteristics in the range of microwatts or milliwatts per litre. In order to produce a sufficient voltage level (>1.5 V) and sufficient power to supply real applications such as autonomous sensors, it is necessary to either scale-up one single unit or to connect multiple units together. Many topologies of connection are possible as the serial association to improve the output voltage, or the parallel connection to improve the output current or the series/parallel connection to step-up both voltage and current. The association of MFCs in series is a solution to increase the voltage to an acceptable value and to mutualize the unit’s output power. The serial association of a large number of MFCs presents several issues. The first one is the hydraulic coupling among MFCs when they share the same substrate. The second one is the dispersion between generators that lead to a non-optimal stack efficiency because the maximum power point (MPP) operation of all MFCs is not permitted. Voltage balancing is a solution to compensate non-uniformities towards MPP. This paper presents solutions to improve the efficiency of a stack of serially connected MFCs through a voltage-balancing circuit.

Solution-processed Al-chelated gelatin for highly transparent non-volatile memory applications

Using the biomaterial of Al-chelated gelatin (ACG) prepared by sol-gel method in the ITO/ACG/ITO structure, a highly transparent resistive random access memory (RRAM) was obtained. The transmittance of the fabricated device is approximately 83% at 550 nm while that of Al/gelatin/ITO is opaque. As to the ITO/gelatin/ITO RRAM, no resistive switching behavior can be seen. The ITO/ACG/ITO RRAM shows high ON/OFF current ratio (>105), low operation voltage, good uniformity, and retention characteristics at room temperature and 85 °C. The mechanism of the ACG-based memory devices is presented. The enhancement of these electrical properties can be attributed to the chelate effect of Al ions with gelatin. Results show that transparent ACG-based memory devices possess the potential for next-generation resistive memories and bio-electronic applications.

Control and Design of a Arc Power Supply for KSTAR's the Neutral Beam Injection

The neutral beam injection generate ultra-high temperature energy in the tokamak of nuclear fusion. The neutral beam injection make up arc power supply, filament power supply and acceleration & deceleration power supply. The arc power supply has characteristics of low voltage and high current. Arc power supply generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The proposed buck converter used parallel switch because it can be increased capacity and decrease conduction loss. When an arc generated, the neutral beam injection chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus the proposed converter should be designed for the characteristics of low voltage and high current. Also, the arc power supply should be guaranteed for system stability. The proposed parallel buck converter enables the system stability of the divided low output voltage and high current. The proposed converter with constant output be the most important design of the output inductor. In this paper, designed arc power supply verified operation of system and stability through simulation and prototype. After it is applied to the 288[kW] arc power supply for neutral beam injection.

Contribution of Electrocardiogram in the Differentiation of Cardiac Amyloidosis and Nonobstructive Hypertrophic Cardiomyopathy.

Due to similar manifestations of hypertensive ventricular walls and abnormal ventricular compliance, it is difficult to differentiate cardiac amyloidosis (CA) and nonobstructive hypertrophic cardiomyopathy (NOHCM) clinically. The purpose of the study was to investigate the value of electrocardiography (ECG) in the differentiation of the two diseases. We enrolled 46 consecutive patients with CA and 64 patients with NOHCM and compared their ECG characteristics.Compared with NOHCM patients, the ECG of CA patients showed more low voltage on limb leads (50% versus 1.6%), atrioventricular block (21.7% versus 4.7%), pseudo-infarct pattern (84.8% versus 39.1%), and longer QRS duration (104 ± 25 versus 98 ± 14 ms) (all P < 0.05). The QRS complex voltage of avR demonstrated the highest diagnostic performance (sensitivity 89%, specificity 94%, cut-off value 0.45mV) as assessed by ROC analysis. The combination of the R wave voltage of I and avR reached a sensitivity of 95% and a specificity of 87% for the diagnosis of amyloidosis.Compared with NOHCM patients, CA patients showed more ECG characteristics of low voltage on limb leads, pseudo-infarct pattern, atrioventricular block, and longer QRS duration. The combination of the R wave voltage of I, avR, and QRS was of diagnostic value in the differentiation of CA from NOHCM.

팬구동용 저압 8/6 SRM의 설계 및 구동 특성

팬구동용 저압 8/6 SRM의 설계 및 구동 특성

Coordinated Control Strategy of Low Voltage Wind/Photovoltaic/Dual- Source Energy Storage Hybrid Microgrid

In this study, a coordinated droop control strategy of dual-source energy storage system with virtual coordinate transformation is proposed by researching on the operation characteristics of low voltage (LV) wind/photovoltaic hybrid microgrid, which is prepared with battery energy storage system (BESS) and super capacitor energy storage system (SCESS). Using virtual coordinate transformation-based droop control not only solves the coupling problem between active and reactive power of LV microgrid, but also enables a coordinated control on BESS and SCESS to achieve smooth handoff from grid-connected mode to isolated mode of LV microgrid for wind, photovoltaic and energy storage. Using PSCAD/EMTDC simulation software, the models of wind turbine system, photovoltaic generation system and dual-source energy storage system are established to form LV microgrid. The effectiveness and feasibility of the proposed control strategy are proved, and the choosing of droop factor of BESS and SCESS is analyzed by simulation. Keywords: Dual-source energy storage system, LV microgrid, smooth handoff, virtual coordinate transformation.

STUDY AND ANALYSIS OF RF MEMS SHUNT SWITCH FOR RECONFIGURABLE ANTENNA

RF MEMS switches can be used to achieve reconfigurability of various RF systems and in particularly for miniaturized antenna structures. In case of micro machined antennas, which involve low voltage signals, RF MEMS switches with low actuation voltage are required for achieving reconfigurability. The capacitive shunt switch derives its switching property from the significant difference of its capacitance in the up-state and down-state. The actuation voltage of RF MEMS switches mainly depends on the spring constant of the switch membrane. In this project a low actuation voltage capacitive shunt switch suitable to be used along with micro machined antennas is designed. A process flow for the fabrication is designed and simulated using Intellisuite. The electromechanical analysis results are presented and compared with that of a fixed- fixed flexure based switch membrane to establish the low actuation voltage characteristics of the proposed design

Source-gated transistors for order-of-magnitude performance improvements in thin-film digital circuits

Ultra-large-scale integrated (ULSI) circuits have benefited from successive refinements in device architecture for enormous improvements in speed, power efficiency and areal density. In large-area electronics (LAE), however, the basic building-block, the thin-film field-effect transistor (TFT) has largely remained static. Now, a device concept with fundamentally different operation, the source-gated transistor (SGT) opens the possibility of unprecedented functionality in future low-cost LAE. With its simple structure and operational characteristics of low saturation voltage, stability under electrical stress and large intrinsic gain, the SGT is ideally suited for LAE analog applications. Here, we show using measurements on polysilicon devices that these characteristics lead to substantial improvements in gain, noise margin, power-delay product and overall circuit robustness in digital SGT-based designs. These findings have far-reaching consequences, as LAE will form the technological basis for a variety of future developments in the biomedical, civil engineering, remote sensing, artificial skin areas, as well as wearable and ubiquitous computing, or lightweight applications for space exploration.

Complementary power output characteristics of electromagnetic generators and triboelectric generators

Recently, a triboelectric generator (TEG) has been invented to convert mechanical energy into electricity by a conjunction of triboelectrification and electrostatic induction. Compared to the traditional electromagnetic generator (EMG) that produces a high output current but low voltage, the TEG has different output characteristics of low output current but high output voltage. In this paper, we present a comparative study regarding the fundamentals of TEGs and EMGs. The power output performances of the EMG and the TEG have a special complementary relationship, with the EMG being a voltage source and the TEG a current source. Utilizing a power transformed and managed (PTM) system, the current output of a TEG can reach as high as ∼3 mA, which can be coupled with the output signal of an EMG to enhance the output power. We also demonstrate a design to integrate a TEG and an EMG into a single device for simultaneously harvesting mechanical energy. In addition, the integrated NGs can independently output a high voltage and a high current to meet special needs.

Space-Charge-Limited Bipolar Currents at High Fields in Polymer/C&lt;sub&gt;60&lt;/sub&gt; Diodes: A Simple Model Description

We investigate the dark transport properties of organic photovoltaic devices formed by a heterojunction of a semiconducting co-polymer and the fullerene (C60) [. The copolymers are composed of thiophene, phenylene and fluorene units, where the thiophene content was kept constant while the fluorene/phenylene ratio was varied. Measurements show that for low voltage, the current versus voltage (j x V) characteristics presents an exponential increasing, typical of a diode behavior. On the other hand, the j x V curves are space-charge limited at high voltages. This latter response follows the theoretical predictions proposed by Koehler et al in Ref. [ (see also [), which explains the dark current in polymer/fullerene photodiodes at high V's. To describe the full j x V characteristics, we have extended the analysis in Ref. [ assuming a space-charge dependent inner series resistance. From such model we are able to nicely fit the experimental curves, to estimate the effective mobility in the whole device and to obtain the diode reverse saturation current j0. Finally, the results indicate that the copolymer with the highest effective total mobility is the PFT [(9,9dihexyl-9H-fluorene-2,7-diyl)-1,2-ethenediyl-2,5-thiophene-1,2ethenediy.

Analysis of an Electrostatic Micro-Actuator Based on Vertically-Horizontally Bending

For the problems of the oversized voltage and undersized displacement in the electrostatic micro actuator of transverse loading recently, a silicon micro actuator model with characteristics of large-displacement and low-voltage is presented based on the principle of vertically-horizontally bending. The deflection equation of the micro actuator is derived. The axial static electricity, temperature stress and axial squeezing pressure on the deformation of micro-beam are analyzed. The simulation shows that the displacement is as big as 17.5μm when the driving voltage is as low as 5V. The displacement is much larger than the deformation of the current micro actuator.

중성입자빔 가열을 위한 아크 전원 공급장치 설계 및 구현

The Neutral Beam Injection(NBI) generates ultra-high temperature energy in the tokamak of nuclear fusion. The NBI consists of filament power supply acceleration and deceleration power supply and arc power supply(APS). The APS has characteristics of low voltage and high current. APS generate arc through constant output of voltage and current. So this paper proposed suitable buck converter for low voltage and high current. The case of proposed buck converter used parallel switch because it can increase capacity and decrease conduction loss. When an arc is generated, the NBI chamber occur high voltage. And it will break output capacitor of buck converter. Therefore the output capacitor was removed in the proposed converter. Thus buck converter with constant output is the most important design of the output inductor. In this paper, designed APS verified operation of system and stability through simulation and prototype.

Fuzzy Sliding Mode Control for a Fuel Cell System

Fuel cell powered systems have low voltage and high current output characteristics. Therefore, the output voltage of the fuel cell must be stepped up by DC-DC converter. In this paper an integrated mathematical model for proton exchange membrane fuel cell power system with DC-DC converter is described by analyzing the working mechanism of the proton exchange membrane fuel cell and the boost DC-DC converter. Fuzzy sliding mode control scheme is proposed to realize stable output voltage under different loads. Simulation operations are carried out and results are compared with fuzzy control and sliding mode control. It is shown that the use of the proposed fuzzy sliding mode controller can achieve good control effect. DOI: http://dx.doi.org/10.11591/telkomnika.v11i5.2553 Full Text: PDF

Design of broadband and high-efficiency class-E amplifier with pHEMT using a novel low-pass microstrip resonator cell

In this article, a high-efficient class-E amplifier design with low voltage and broadband characteristics using a novel Front Coupled Tapered Compact Microstrip Resonant Cell is presented. The proposed micorstrip resonator is used as the harmonic control network in order to suppress higher order harmonics, which obtained the optimized impedance matching for the fundamental and harmonics. The class-E amplifier is realized from 0.7 to 1.8 GHz, and obtained the power added efficiency of 72.5–77.5%. The maximum value of Power added efficiency (PAE) is 79.7% with 11-dBm input power at 1.5 GHz. The designed class-E amplifier using the proposed harmonic control network gained 15.34% increment in PAE, and 25.6% reduction in the circuit size in comparison with the conventional class-E amplifier. The simulation and measurement results show the validity of the proposed design procedure of the broadband class-E amplifier using a novel microstrip resonator cell. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1118–1124, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.27490

Simulation of the effects of AlGaN electron-blocking layers on the characteristics of InGaN blue light-emitting diodes

The internal quantum efficiency (IQE) and the forward voltage characteristics of GaN/InGaN-based blue light-emitting diodes (LEDs) are investigated based on numerical simulations. Specifically, we study the effects of structural parameters near the AlGaN electron-blocking layer (EBL), such as the Al composition of the EBL, the thickness of the GaN last barrier (LB) layer, and the doping concentration at the p-type-doped layers. When the hole concentration is sufficiently high, LEDs without the AlGaN EBL are found to show the best performances in IQE and forward voltage, implying that AlGaN-EBL-free structures can be advantageous for achieving high-efficiency LED characteristics. We also find and discuss the facts that the high hole concentration at the p-layers and the thin LB layer thickness are advantageous for high IQE and low forward voltage characteristics under the condition that the Mg diffusion into the active layers is not significant.