Wide Gain Range Research Articles

Research on Multi-Port DC-DC Converter Based on Modular Multilevel Converter and Cascaded H Bridges for MVDC Applications

Aiming at the low-voltage DC distribution network system and combining the characteristics of F2F structure and ISOP-DAB structure DC transformer, this paper proposes a DC transformer structure based on modular multilevel converter (MMC) and cascaded H-bridge. First of all, this paper analyzes several different cases. Case 1 proposes a type of equal carrier-phase-shift pulse-width modulation (CPS-PWM) of MMC, which can produce an equal five-level voltage waveform. In the meanwhile, another unequal CPS-PWM control is proposed to produce an unequal five-level voltage waveform. According to the descriptions of case 2 , the quasi-square-wave-modulation method with a wide gain range can greatly reduce the insulation design difficulty of the intermediate AC side high-frequency transformer and the voltage stress on the AC side. Case 3 demonstrates the extended-phase-shift (EPS) control of three-port DC-DC converter. Combining the voltage sorting algorithm of voltage sequencing and cyclic switching, a strategy of voltage equalization for grouped capacitors is proposed. Considering the various application scenarios of actual working conditions, the soft switching characteristics and multi-port power characteristics of the DC transformer are analyzed. In order to verify the feasibility of the DC transformer structure and its control strategy, a simulation model was built in Matlab/Simulink and the results were verified. The results are in accordance with the theoretical analysis.

Multi-Channel Low-Noise Analog Front Design

With the development of digital nuclear pulse processing technology, the requirements for the analog front-end circuit of digital energy spectrometers are getting higher and higher. Not only need to reduce the noise caused by the device as much as possible, but also need to meet the needs of multi-channel data acquisition. This article based on VGA (Variable Gain Amplifier) has designed a multi-channel low-noise analog front-end circuit to meet the functional requirements of the energy spectrometer while reducing the signal transmission in the analog front-end circuit as much as possible. The circuit noise is strictly controlled to ensure the signal-to-noise ratio of signal transmission. AD9255 is used for waveform digitization, and the input range is 100 μV-2 VPP. After testing, the circuit has a wider gain range and better noise control. Input 100 μVpp signal when the analog front-end gain is 24 dB, and its signal-to-noise ratio can reach 1:1.

A New High Voltage Gain DC to DC Converter with Low Voltage Stress for Energy Storage System Application

Increasing energy demand globally has led to exploring ways of utilizing renewable resources for sustainable development. More recently, the integration of renewable distributed resources in small- and large-scale grid has been seriously researched. Development in renewable power sources and its integration with the grid require voltage level conversion to match the grid/micro-grid level. The voltage level conversion is brought about by employing Direct Current-Direct Current (DC-DC) converters with boosting features. The paper presents a wide gain range DC-DC boost converter with a low-stress on switching devices. The proposed converter’s voltage gain is high compared with the conventional quadratic boost converter and other recently developed high gain boost converters. The topology has been compared with recently proposed topologies, and comparative analysis based on various performance parameters has shown that the topology is suitable for renewable and sustainable energy storage and grid integration. The power loss analysis has been done by incorporating the switching and conduction losses. A hardware prototype of 150 W has been developed to validate the converter’s performance in steady-state as well as in dynamic conditions.

Land cover/use change analysis and mapping of Borg El-Arab City, Egypt

One of the essential steps for agricultural development planning is the recognition of land cover and land use LCLU classes and the associated changes with time, in which LCLU avails as one of the major input criteria. The North coastal region of Egypt is exposed to significant spatial and temporal changes in LCLU classes (urban, agriculture, and water bodies) that basically affect any kind of development programs. Borg El-Arab City represents a potential community and new industrial site for future development in the region. The supervised classification of Landsat satellite images and computation of the normalized difference vegetation index (NDVI) are applied as effective tools in the study area to observe the LCLU changes. Landsat 5, 7, and 8 satellite images were used and four images dated in 1986, 1999, 2006, and 2017 were selected. The area under consideration was classified into seven main classes ,e.g., Mediterranean Sea, salt marshes, agriculture, urban, bare land, swamps and wet land, and shoreline strip. The area was subjected to significant changes in the last three decades as a result of the reclamation projects growing and industrial effectiveness as well. Taking the whole period (1986–2017) into consideration, results show that the study area is exposed to a wide range of gain or loss in the area of different land cover classes, particularly in regard to the agriculture area, urban land, and bare land. The surface area of urban land, agriculture land, and water bodies increased on the expense of decreasing the bare land, where it lost 31.3%. The urban area expanded into much of the agricultural and the agricultural land expanded into bare land. In light of the recognized change causes, approach policy suggestions for better management of LCLU can be established.

Three-Phase LLC Battery Charger: Wide Regulation and Improved Light-Load Operation

Three-phase LLC resonant converters can handle much higher power compared to half-bridge and full-bridge LLC converters, which makes them suitable for levels 2 and 3 battery charger applications. In addition to the unique features of LLC resonant converters, the three-phase structure provides higher power capacity and higher power density at higher power levels in comparison with single-phase structures. Although single-phase LLC resonant converters were thoroughly investigated in the literature for many different applications, limited work has been done on three-phase LLC converters. Unexplored problems with three-phase LLC resonant converters include issues with their limited gain range and also their poor light-load efficiency. In this article, a modified three-phase LLC resonant converter with a new phase-shedding strategy is proposed. With the proposed modified topology and phase-shedding strategy, the wide gain range needed for covering the recovery zone of charging Li-ion batteries is realized. Moreover, with the proposed phase-shedding strategy, a significant efficiency improvement with light-load absorption charging is achieved. A 3-kW prototype was developed to validate the performance of the proposed converter.

Activity-dependent myelination: A glial mechanism of oscillatory self-organization in large-scale brain networks

Communication and oscillatory synchrony between distributed neural populations are believed to play a key role in multiple cognitive and neural functions. These interactions are mediated by long-range myelinated axonal fiber bundles, collectively termed as white matter. While traditionally considered to be static after development, white matter properties have been shown to change in an activity-dependent way through learning and behavior-a phenomenon known as white matter plasticity. In the central nervous system, this plasticity stems from oligodendroglia, which form myelin sheaths to regulate the conduction of nerve impulses across the brain, hence critically impacting neural communication. We here shift the focus from neural to glial contribution to brain synchronization and examine the impact of adaptive, activity-dependent changes in conduction velocity on the large-scale phase synchronization of neural oscillators. Using a network model based on primate large-scale white matter neuroanatomy, our computational and mathematical results show that such plasticity endows white matter with self-organizing properties, where conduction delay statistics are autonomously adjusted to ensure efficient neural communication. Our analysis shows that this mechanism stabilizes oscillatory neural activity across a wide range of connectivity gain and frequency bands, making phase-locked states more resilient to damage as reflected by diffuse decreases in connectivity. Critically, our work suggests that adaptive myelination may be a mechanism that enables brain networks with a means of temporal self-organization, resilience, and homeostasis.

Turn-Off Delay-Controlled Bidirectional DC–DC Resonant Converter With Wide Gain Range and High Efficiency

Series resonant converter can only operate efficiently within a narrow voltage gain range, which limits the use for battery charging applications. Thus, this article proposes a turn-off delay-controlled bidirectional series resonant (TFD-BSR) converter to extend the voltage gain range and enhance the efficiency. Instead of frequency modulation, the turn-off delay of the corresponding bottom switches is adopted to regulate the direction and amplitude of power flow. First, high peak and low valley voltage gain is obtained at fixed switching frequency. As a result, wide voltage range is extended. Second, the voltage gain is independent of auxiliary and magnetizing inductors, and hence, a large value for the two inductors, which depresses the circulating losses significantly, can be designed just considering zero-voltage switching (ZVS) conditions. In addition, all the active switches can operate with ZVS, which further enhances the efficiency. Operation principles, voltage gain characteristics, ZVS analysis, and design method of the proposed TFD-BSR converter are analyzed in detail. Finally, the feasibility and performance of the proposed converter are validated by simulations and experimental results from a 3.5-kW prototype.

Transient Control and Soft Start-Up for 1-MHz LLC Converter With Wide Input Voltage Range Using Simplified Optimal Trajectory Control

The 48-V bus converters are widely used in telecommunications and network power architectures. A single-stage regulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> bus converter can achieve high efficiency and high power density. This article addresses the control challenges of a regulated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> converter for 48-V bus converter applications. Simplified optimal trajectory control (SOTC) is used to control a 1-MHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> converter with an input voltage range of 40–60 V and a frequency range of 0.8–1.8 MHz. A digital implementation of two-step SOTC is proposed for the high-frequency <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> using a low-speed microcontroller (MCU). The proposed implementation can achieve the optimum transient performance and minimize settling time. SOTC can achieve the optimum transient response for an <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> operating at resonant frequency but has a limited impact at a wide gain range. As a result, a feedforward compensation is proposed, in conjunction with SOTC, to achieve optimum transient response at a wide input voltage range or wide gain range. Moreover, a soft start-up with adaptive switching frequency is proposed to achieve start-up under limited current stress over the whole input voltage range. The experimental results are demonstrated on a 1-MHz <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$LLC$ </tex-math></inline-formula> 48-V bus converter using a 90-MHz TMS320F28069 Piccolo MCU.

Universal Output Characteristics of Single-Mode Operation in Low-Loss Large- V -Number Multimode Waveguide Lasers with Transverse Spatial Hole Burning

We study the performance limit of single-mode operation in low-loss large-V-number planar waveguide lasers, with transverse spatial hole burning as the dominating mechanism for transverse-mode competition. By introducing normalized variables, we develop a simple semianalytical model to describe the universal output characteristics of single-mode emission before the onset of high-order modes, which can be easily scaled to a wide range of laser configuration parameters. Our model is validated using exact numerical solutions, which show applicability beyond that of the low-loss approximation. Our analysis establishes a minimum criterion of the loss ratio between the fundamental and first higher-order mode for a robust single-mode operation. This criterion is much weaker than that of conventional wisdom based on the pure wave-propagation argument, which we attribute to a resonator enhancement effect. Our universal outcome can be denormalized to establish the relationship between single-mode extraction efficiency and optimum output coupling in a multimode laser with arbitrary modal loss ratios over a wide range of single-pass unsaturated gain and loss.

Design Method of 6-Element Boundary Gain for LLC Resonant Converter of Electric Vehicle

In the application of on-board chargers, LLC resonant converters need to work in multiple operating modes to achieve wide-range output requirements. For the most commonly used single-phase and three-phase LLC topologies, the time domain expressions of all possible operating modes are introduced to predict voltage and current behaviors. Based on the mode analysis, the 6-element boundary gain design method is proposed to design a wide gain range LLC resonant converter. The resonant current is used as the basis for ZVS judgment and the transformation trend of ZVS in the full operating range is given. Through reasonable distribution of the boost region and the buck region, the resonant devices can be designed more appropriately to achieve lower conduction loss and higher efficiency. Finally, the prototypes of 3.3kW and 6.6 kW are built to verify the theoretical analysis of the method in single-phase LLC and three-phase LLC.

The neoEEG board: A 3 nV/[formula omitted] multi-channel wireless instrument for neonatal EEG monitoring

This paper describes the design considerations and performance evaluation of a novel high-performance instrumentation, termed the neoEEG Board, able to record neonatal EEG signals with high precision. This prototype EEG recording modality is proposed as an alternative to the currently utilised in NICU state-of-the-art device, the CFM™. Among other characteristics, the neoEEG Board is modular, portable, wearable, wireless and battery operated. It offers 8 channels per module, each providing independent spectral analysis from 0.5 to 100 Hz, with a novel topology for variable bandwidth. The proposed instrument’s noise figure has been measured and found to be equal to 3 nV/Hz, allowing it to resolve very weak signals down to 6 nVp-p. In addition it provides high CMRR (>130 dB), wide gain range (74 dB to 95.5 dB), DC-offset tolerance up to ±35 mV, sampling rate per channel up to 32 kHz and supports wireless data transmission up to 2 Mbits/s.

Effects of Gain and Index of Difficulty on Mouse Movement Time and Fitts’ Law

The mouse, being the major means of inputting and controlling data on a computer, should be set right for best performance. Mouse gain, defined as the ratio of the movement distance on the computer screen to the movement distance of the mouse, controls the movement time when both speed and accuracy are important. Reported optimum gain values vary widely from about 2 to 15. An experiment having a targeting task was used to test 16 participants using a wide range of gain (1.2, 2.4, 14.5, and 38.9). An optimum gain of 2.4 was found for a display movement amplitude ( A ) of 100 mm, whereas the optimum gain was 14.5 for amplitudes of 200 and 400 mm. Depending on the gain and the movement amplitude, Fitts’ law should be modified to accurately model movement time (MT) in the form of MT = A + b (ID) − c ( A *ID). Only at low gains could a critical index of difficulty be determined, that being about 3.5.

A Family of Step-Up Series–Parallel Dual Resonant Switched-Capacitor Converters With Wide Regulation Range

In this paper, a family of new step-up series–parallel dual resonant switched-capacitor converters (SP-DRSCs) is proposed to extend the conversion ratio for high step-up applications. The converters feature a wide gain range, continuously adjustable, and enhanced light-load voltage regulation. All flying capacitors operate in resonance, eliminating high transient current spikes and charge sharing losses. Thus, zero-current-switching (ZCS) turn- on for all transistors and ZCS turn- off for all diodes are achieved. A comprehensive analysis of the operation principle, voltage-gain curves, stable regulation range, and voltage and current stress is given. An analytical method to quantify the passive component volume for the group of step-up dual resonance switched-capacitor converters is presented. Further design considerations to optimize the passive component volume of the proposed SP-DRSC and the effect of bulky bypass capacitors on the volume are discussed.

Changing Moho Beneath the Tibetan Plateau Revealed by GRACE Observations

AbstractA wide range of mass gain in the inland of the Tibetan Plateau (TP) has been observed by the Gravity Recovery and Climate Experiment (GRACE). But there are still controversies on how to understand this phenomenon. In this paper, satellite geodesy data and hydrological models are combined and applied for extracting signals caused by tectonic processes in the TP during the period from 2003 to 2009. We find that in the inland of the TP there are three regions with a significant signal that should be attributed to tectonic processes. The three prominent mass signals, each located in the western, central, and eastern TP, are estimated to be at the rate of 1.47 ± 0.43, −0.85 ± 0.53, and 1.51 ± 0.56 cm/year, respectively, in equivalent water height. However, the rate caused by Earth surface deformation constrained by GPS is 0.33 ± 0.15/0.30 ± 0.10/0.14 ± 0.24 cm/year in equivalent water height, which cannot explain the whole tectonic signals and indicates that a significant mass change occurs beneath the crust, that is, the deformation of the Moho interface. We estimate the Moho change rate in the inland of the TP and find that the Moho interface is suffering an uneven deformation. The Moho is uprising at a rate of 18.1 ± 7.2 mm/year in the west and 21.7 ± 9.7 mm/year in the east of the TP, while there is an obvious deepening rate of −18.3 ± 8.6 mm/year in the central TP.

Emission Characteristics of All-Silicon Distributed Feedback Lasers With a Wide Gain Range

With the development of nanomanufacturing methods, the manipulation of photons down to the nanoscale in silicon integrated optical chips has become a feasible and promising solution for next-generation data processing as electronic chips reach their limit. As an essential active device that generates photons for all other working photonic components, silicon lasers are the last barrier to achieve silicon integrated optical chips. Although optical gain in silicon nanocrystals (Si–NCs) was observed in 2000, the progress in realizing all-Si lasers has been very limited due to the inferior optical gain compared to traditional gain materials. In this paper, highly luminescent thin films of Si–NCs with a photoluminescence quantum yield of 57% are developed. The broadband photoluminescence covers the wavelength range from 650 to 900 nm, and wide-range optical gains are identified, indicating the feasibility of a tunable laser. Distributed feedback (DFB) all-Si lasers are fabricated using these thin films and pumped by femtosecond pulses. Various characteristic lasing behaviors are observed. Additionally, three different DFB grating periods are selected, and the lasing peak can be tuned by over 100 nm. The lasing thresholds range from 8.3 to 53.3 MW/cm2. The linewidths of lasing peaks are less than 2 nm.

A Compact Model for Si-Ge Avalanche Photodiodes Over a Wide Range of Multiplication Gain

Silicon-germanium (Si-Ge) avalanche photodiodes (APDs) have superior gain bandwidth product due to the low impact ionization ratio of silicon. To enable efficient optical transceiver systems, cosimulation environments are essential for optimization of optical devices and transceiver circuitry. A compact Si-Ge APD circuit model, which captures both electrical and optical dynamics over a wide range of multiplication gain, is presented. This model includes effects of carrier transit time, avalanche buildup time and electrical parasitics. Model parameters are extracted by small-signal measurement and impulse response measurement where three gain regimes are discussed corresponding to the different mechanisms of carrier transit time and electrical parasitics. Simulated and measured bandwidth versus gain have a good agreement for APD multiplication gains from M = 1 to M = 17. Excellent matching between simulated and measured 25 Gb/s eye diagrams at M = 2 and M = 5.9 is achieved.

High‐power‐density high‐efficiency LLC converter with an adjustable‐leakage‐inductance planar transformer for data centers

LLC converters can achieve high efficiency, high- power density, wide gain range, and galvanic isolation. This study presents a high-power-density and high-efficiency LLC converter with an adjustable-leakage-inductance planar transformer for the DC-DC conversion in data center power supplies. A planar transformer with adjustable leakage inductance is modelled and developed to provide an accurate design for resonant frequency and voltage gain. A detailed power loss analysis is performed. Furthermore, a thermal model is provided to aid in heat sink design. GaN devices are used in the converter to achieve high-switching frequency and low-switching loss. A 450 kHz, 360-400 V DC input, 12 V DC output, 750 W LLC converter prototype with an adjustable-leakage-inductance planar transformer is built and tested. The power density of the system is 15.4 W/cm 3 including an auxiliary power supply. The peak efficiency of the overall system is over 95%.

A 5-kW Isolated High Voltage Conversion Ratio Bidirectional CLTC Resonant DC–DC Converter With Wide Gain Range and High Efficiency

This paper presents a novel high voltage conversion ratio (HVCR) bidirectional CLTC resonant dc-dc converter. Based on inductor-inductor-capacitor (LLC), series resonant converter, and capacitor-inductor-inductor-capacitor (CLLC), the novel CLTC structure is proposed. With the use of auxiliary transformer and extra resonant capacitor, a CLTC resonant dc-dc converter can achieve zero voltage switching in all load ranges. Also, CLTC has a good gain characteristic with high power load. In this study, a review of the statuses for the isolated HVCR bidirectional converters is made. The operating principle of a bidirectional power flow in two directions is analyzed in details. In addition, by changing ac output resistance, a modified fundamental harmonic analysis (FHA) method makes the calculated gain curve more accurately than traditional FHA. Also, voltage and current stresses of power switches and resonant capacitors are given. A parameter optimization method is proposed to minimize the impedance angle of CLTC, which corresponds to less reactive power and turn-off current. The optimal parameters show advantages in voltage and current stresses. Moreover, power losses are analyzed in this study, showing advantage of CLTC in efficiency. At last, the experimental results based on a 5-kW prototype converter are presented to validate the theoretical analyses.

Experimental AND and OR Logic Gates With MZI and SOA Using PAM Modulation

One of the main limitations of optical communication systems is the current need for optoelectronic conversions in intermediate devices, which do not reach the transmission rates of optical fibers of terabits per second. In this work, we investigated the obtaining of logic gates through a configuration of a Mach–Zehnder interferometer with a semiconductor optical amplifier (SOA) as the unbalancing element of the interferometer. We experimentally studied three different scenarios of input power for a continuous wave regime and one scenario for the PAM regime, both with varying levels of gain of the SOA. As a result, we obtained the AND and OR logic gates in all scenarios in a wide range of gain of the SOA, besides the logic functions 0 and 1 in some of the cases. We confirm the quality of these logic gates by the precision rate regarding the threshold of 0.4 dB above and below the central limit, according to recommendations from the literature. We highlight that the technique used in this experiment is much less complex than most of those described in the literature. The use of pulse amplitude modulation (PAM) suggests a simpler way for controlling logic gates, once we can obtain those by simply changing the injection current applied by the SOA. The experimental obtaining of such logic gates is relevant for all-optical logic circuits that are proposed to optimize the current optical communication systems.

Reconfigurable Wide Bandwidth Using Novel Extraction Technique of Slotted Monopole Antenna with RF CNT Network

This work first moment focuses on the concept of reconfigurable wide bandwidth using novel extraction technique of slotted monopole antenna with RF carbon nanotube (CNT) network. The entire approach is folded into four different designs. The first design proposes a monopole antenna where asymmetric flower type corners and mushroom shape encloses by T-slot is cut on the patch. This new shaped antenna covers wide impedance bandwidth of about 14.5 GHz within range from 21.5 to 36 GHz. The proposed antenna observed that lower bands are excited with new resonating modes by inserting T-slot upon mushroom shape while higher bands are effected due to asymmetric flower type corners on the patch. A wide range of gain from 16.3 to 20.5 dB with maximum axial ratio bandwidth of 2.8% is also succeed. Measured and simulation results for proposed antenna shows good agreement with each other. In second design, a novel extraction technique is used for equivalent model of slotted monopole antenna which shows promising agreement with the original geometry. Thirdly, introduces RF CNT equivalent model which demonstrates its ability to resonant at wideband within range of 12.4–25.1 GHz with 68% of fractional impedance bandwidth. Finally, RF equivalent model of slotted monopole antenna is integrated with CNT for the proper operation. The fabrication of integration network scenario proves notability of reconfiguration in aspect of wide bandwidth with the compactness. A frequency switchable notability dominant some excited additional resonant modes using proper impedance matching between proposed antenna and RF CNT. This proposed work is fascinating to our integration network which fully covered K-band and almost for Ka-band application.