External Capacitor Research Articles

Diagnosis of Two-Phase Oil/Gas Flow in a Closed Pipe using an 8-Electrode ECT System

Electrical tomography techniques have been developed to monitor the internal behavior of industrial processes. Electrical capacitance gives the best benefits over other tomography modalities, as it has no radiation, is non-intrusive, and has a low cost. This study investigated the diagnosis of two-phase oil/gas flow in a closed pipe, using an image data capture system for an 8 external electrode Electrical Capacitance Tomography (ECT) sensor. The system had a high-resolution ratio, a small measurement error, and was able to remove the effects of stray capacitance. Experimental measurements were carried out on two different materials that filled the space inside the pipe in different proportions to determine the sensitivity and accuracy of the measurement. The results showed that the system had fast image data capture time, high accuracy, a very small resolution ratio, and a good signal-to-noise ratio and quality factor.

Image and Velocity Profile Reconstruction Using a Customized 8–16 Electrode Electrical Capacitance Tomography Sensor Based on LabVIEW Simulation

Electrical Capacitance Tomography is a method for determining the dielectric permittivity distribution inside an object from the measurement of the external capacitances of a multi-electrode assembly. The measuring electrodes, which are metal plates, must be large enough to give a measurable change in capacitance. In this article, the performance of the ECT sensor, the sensitivity matrix, and hence the reconstructed image quality and the velocity profiles are improved. A typical customized 16–8 electrode ECT sensor is proposed, simulated, and implemented on the LabVIEW platform in contrast with a set of standard 8, 12, and 16-electrode ECT sensors. The results of these types of sensors are noted and compared to each other, focusing on the customized sensor. It is observed from the results obtained during this simulation experiment that the performance of the customized 16–8 electrode ECT sensor is comparatively better and exhibits better quality and performance with respect to its image and velocity reconstruction. The comparison of results further demonstrated that the correlation coefficient changes from 0.61 to 0.96, and the error images are within 0.3 to 0.1 for the SNRs going from 60 to 90 dB. It was also observed that the reconstructed velocity profiles are consistent with the original expected velocity profiles for the customized 8–16-electrode ECT sensor.

Optimal Design Proposal for Capacitance in Operating Area Expandable SR Motor Drive Circuit

A novel drive circuit for switched reluctance (SR) motor expanding the operating area under limited source voltage has been proposed by adding external capacitor in series to extend supply voltage. However, the capacitance of the external capacitor has not been optimized to be sufficient to extend the driving range of the SR motor. Subsequently, the authors have previously proposed a conservative design method for capacitance by linearizing the winding current. However, there is a problem in that the difference between the conservative design and the simulated fluctuation of the capacitor voltage is large. In this paper, an optimal design method is proposed for the capacitance by using an LC equivalent circuit at the beginning of excitation and demagnetization.

Nonlinear dynamic analysis and vibration suppression on the composite laminated plates with general boundary conditions in supersonic airflow

This paper performs the nonlinear dynamic analysis and vibration reduction of the panel structures subjected to supersonic airflow. The negative capacitance piezoelectric shunt damping circuit (PSDC) which contains bonded piezoelectric element and external negative capacitance is adopted. Based on the modified Ritz approach and energy approach, the formulations of the nonlinear panel structure with attached piezoelectric element are derived. A unified mathematical model for the nonlinear dynamic analysis of composite panels subjected to general edge boundaries in supersonic airflow is formulated. Furthermore, the Newmark approach and Newton iteration approach are utilized to calculate time domain responses of panel structures under aerodynamic pressure. Several numerical cases are further performed to verify the present formulations. Finally, impacts of several factors on the flutter characteristics of panel structures are investigated and the comparisons concerning the vibration responses of panels having and without PSDC are performed to verify vibration reduction properties of the present method. The numerical results show that the vibration and flutter of panels in supersonic airflow can be sufficiently suppressed by the present simple vibration reduction strategy.

A Fully-Integrated Micro-Display System With Hybrid Voltage Regulator

A fully-integrated active matrix light-emitting diode (AMLED) micro-display system is demonstrated in this paper. The system consists of a 36 × 64 AMLED array chip based on GaN-on-Silicon epilayers and a silicon driving chip integrating an on-chip hybrid voltage regulator, pixel drivers, and peripheral circuits. Then two chips are bonded with low-cost Au-free flip-chip bonding technology. As such, this system is able to directly operate with a battery without any external passive components. Multiple techniques were proposed to achieve the system integration: (1) A fully-integrated hybrid voltage regulator consisting of a step-up switched-capacitor (SC) converter cascaded by a step-down linear voltage regulator was fabricated in a 0.18 μm CMOS technology. It achieved only 1.38% output voltage ripple without external capacitors, and be able to deliver a maximum power of 216mW with peak efficiencies of 91% in the linear mode and 78% in the SC mode; (2) Micro-LEDs are fabricated on GaN-on-Silicon substrate that significantly suppresses the light crosstalk between pixels and reduces the cost; (3) An Au-free flip-chip bonding technique is developed to reduce the bonding cost and achieved reliable connections between AMLED array chip and silicon driving chip. The whole system achieved 635 pixel/in (PPI) pixel density. Images and videos with 4-bit grayscale could be rendered. This prototype achieved a high integration level and demonstrates the tremendous potential of the highly efficient, low cost fully integrated AMLED micro-display system.

Programmable resonant and forced mode high-voltage RF generator for dielectric barrier discharge and quadrupole mass filter

Dielectric barrier discharge, originally called silent discharge, is the electrical discharge between two electrodes separated by an insulating dielectric barrier. A high-voltage alternating current is required to generate the discharge process. There are two major principles of operation to implement a high-voltage generator: resonant mode and forced mode. While operating in forced mode, the working frequency is forced by the user using internal electronic devices. On the other hand, in resonant mode, the operating frequency is determined by the resonant circuit, which includes the external capacitance, inductance, and resistance of the load. This work shows a flexible circuit based on a real-time digital signal processor and a full H-bridge that combines the two topologies and can be used as a controller for dielectric barrier discharge and a quadrupole mass filter with varying capacitance.

Robot sensing based on electrical capacitance tomography sensor with rotation

The existing sensing technology for industrial robot hands cannot sense inside of an object. To recognise the material and internal distribution of an object when it is grasped, electrical capacitance tomography (ECT) may be used if the object is non-conductive, as ECT can measure the permittivity distribution inside an object from external capacitance measurements. An ECT sensor normally has 8 or 12 electrodes equally distributed around an object. This paper introduces the first attempt to make use of ECT with robot hands. Because the number of electrodes is limited, it is necessary to rotate the object to be imaged mechanically, so that sufficient measurements can be taken. Four aspects of the ECT sensor are discussed based on simulation: (1) the structure of electrodes; (2) the number of rotation times; (3) the starting position of rotation; and (4) the diameter of rotation. Two image reconstruction algorithms are used: the linear-back projection and Landweber iteration with three typical distributions. The results show that the rotational three-electrode ECT structure has good ability to produce useful images, showing the internal distribution of unknown objects.

ディスクリートIGBTを用いた電圧共振回路搭載IH調理器の放射EMI対策

The limit levels of radiated EMI for IH cookers were revised to lower values in December 2018 by the Electrical Appliances and Materials Safety Act. In this study, a switching noise mechanism and its countermeasures for an IGBT loaded into a voltage resonance circuit of an IH cooker is analyzed. A device model is developed using a BSIM3 MOSFET model with voltage-dependent capacitors. The inductor and capacitor load switching operation, including the parasitic elements of a test circuit, is simulated, and switching noise generated during turn-off transient conditions is discussed. An effective method for EMI suppression is proposed based on optimization of the C-voltage characteristics and the addition of an external capacitor. The effect of reduced radiated EMI levels is discussed.

Extended topological interface modes with tunable frequency in the piezoelectric phononic crystal

Acoustic metamaterials have provided a versatile platform to explore more degrees of freedom for tunable topological wave manipulation. Recently, extended topological interface modes (ETIMs) with heterostructure have been proposed to extend the spatial degree of freedom. However, the absence of frequency tunability still restricts the application of the wave transports of ETIMs. Here, we propose a one-dimensional piezoelectric topological phononic crystal (PTPC) with electrically tunable working frequency by introducing external capacitor circuit. With the bandgap frequency actively controlled by appropriately tuning the capacitances, we construct the heterostructured PTPCs possessing high-energy-capacity ETIMs with electrically tunable working frequency range and bandwidth. This work paves the way to wide engineering applications on acoustic sensing enhancement, nondestructive testing, energy harvesting, information processing, and reconfigurable topological wave transports.

Proposal of a novel methodology for the electrochemical characterization of well-behaved redox-active materials used in supercapacitors

This work presents a new methodology to interpret the electrochemical behavior of pseudocapacitors (PCs) which is based on a new theoretical approach denoted as the generic electrochemical model (GE). Based on a single premise, the GE model is composed of two distinct time constants (τ = RC) used to represent the narrow-deep (n-d) and large-shallow (l-s) heterogeneous surface structures incorporating the different surface defects (e.g., cracks, fissures, pores, etc.), which incurs in the so-called distributed capacitance and resistance phenomena. Five different transition metal oxide (TMO) electrodes composed of Ni, Co, and Ru were used to verify the validity of the proposed model equations. The internal (inner) and external (outer) capacitances and resistances were accurately determined from the fitting analysis (e.g., r2 ≥ 0.998 and χ2 < 10–5) involving the findings obtained using different techniques. Therefore, disagreements between the electrochemical techniques regarding the resistance and capacitance absolute values were ascribed to different average penetration depths intrinsic to each particular perturbation function, i.e., each electrochemical technique exhibits a particular sensitivity for detecting the capacitive and resistive phenomena in porous/defective electrodes. We verified for well-behaved PCs, where the so-called battery-like behavior is absent, that capacitive and pseudocapacitive phenomena are indistinguishable phenomena, as predicted by Saveànt and Conway. Therefore, the GE model can also be used for studying different carbon-based materials used in supercapacitors. Finally, the presence of different surface heterogeneous structures present in defective electrodes is the main cause of the distributed capacitance and resistance verified in both time and frequency domains.

A wide input range, external capacitor-less LDO with fast transient response

A high voltage, external capacitor-less low-dropout regulator (HVLDO) with transient enhancement loop is presented in this work. The proposed HVLDO is designed with high withstand voltage laterally-diffused MOS (LDMOS) transistors and a transient enhancement loop is proposed to properly inject/sink current to/from the gate and output nodes of the power transistors to achieve fast transient response and high stability. Fabricated in 0.5µm SOI BCD process, the HVLDO occupies an active area of 0.29mm2. Operating with an input voltage ranging from 5.2 to 20V, it supplies an output voltage of 5V and a maximum load of 100mA. For all load conditions, this design has the power supply rejection of -49dB@100kHz, the phase margin over 68.4deg and achieves a temperature coefficient of 13.15ppm/°C. Measurement results show that this design has a line regulation of 0.88mV/V and a load regulation of 0.22mV/mA. The proposed HVLDO features fast line transient response of 60/20mV@9.8V/µs, fast load transient response of 30/70mV@100mA/µs, and recovery time of 2µs without external capacitors. Compared with the prior art, this work achieves the best transient FOM of 12.19fs.

Frequency modulations due to domain dynamics in terahertz quantum cascade lasers

The light output of quantum cascade lasers is strongly affected by electric field-domain oscillations if the laser shows electrical instabilities. This can result in a substantial broadening of the emission spectrum, which is investigated here by detailed simulations for a terahertz device. We explain how the light pulsation is affected by electrical injection conditions and external capacitances. Experimental data confirm that the oscillation frequencies are not essentially affected by circuit conditions, while a large external capacitance produces almost non-observable oscillations due to stabilization of the circuit.

Measurements of Small Frequency Differences by Dual Mode 4 MHz Quartz Sensors

We proposed a method for measuring frequency differences of the order of a few Hz with an experimental error lower than 0.0001% by using two 4 MHz quartz oscillators, the frequencies of which are very close (a few 10 Hz difference) due to the dual mode operation (differential mode with two temperature-compensated signal frequencies or a mode with one signal and one reference frequency). We compared the existing methods for measuring frequency differences with the new method which is based on counting the number of transitions through zero within one beat period of the signal. The measuring procedure requires equal experimental conditions (temperature, pressure, humidity, parasitic impedances etc.) for both quartz oscillators. To ensure equal resonant conditions for oscillation two quartz crystals are needed, which form a temperature pair. The frequencies and resonant conditions of both oscillators must be almost equal, which is achieved by an external inductance or capacitance. In such a way, we minimized all the external effects and ensured highly stable oscillations and high sensitivity of the differential sensors. The counter detects one beat period by an external gate signal former. By using the method of counting transitions through zero within one beat period, we reduced the measuring error by three orders of magnitude, compared to the existing methods.

A new capacitive coupler design for wireless capacitive power transfer applications

Capacitive power transfer (CPT) technology has become a promising alternative solution for wireless charging applications. This paper proposes a novel coupler design to form a resonant capacitor by inserting dielectric material between two bent metal plates for each primary and secondary circuit. The main purpose of the proposed coupler is to eliminate the external capacitors and solve the low coupling capacitance for CPT applications. A comparison to the conventional four-plate coupler is presented, which shows specifically higher coupling capacitance, lower required inductance, and lower cost. Finally, the effectiveness of the proposed coupler structure is verified by simulation and experimental results.

A MOS-DTMOS Implementation of Floating Memristor Emulator for High-Frequency Applications

The work presented in this article focuses on designing a floating MOS-dynamic threshold voltage MOSFET (DTMOS)-based circuit to emulate a memristor. The proposed circuit consists of four transistors, including a DT-MOSFET and an external capacitor, which helps obtain high-frequency operations up to 3 MHz. This facilitates easier integration of the devices and monolithic IC fabrication. The correctness of the proposed emulator is validated by conducting various parametric analyses at different operating frequencies and process corners, and it generates acceptable pinched hysteresis loops (PHLs) at various frequencies. Furthermore, pre- and post-layout validation of the proposed emulator are also performed using Cadence Virtuoso with Taiwan Semiconductor Manufacturing Company (TSMC) 180-nm process design kits (PDKs) to prove its effectiveness as a memristor. The area and power consumption of the proposed emulator are <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$157.48~\mu \text {m}^{2}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8.24~\mu \text {W}$ </tex-math></inline-formula> , respectively. The physical experiment of the proposed memristor emulator is performed using ALD <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1106~n$ </tex-math></inline-formula> -channel MOSFETs to characterize its functionality as a real-life memristor. It is also used in designing a memristor-based application to showcase its applicability in power and area optimal circuit design.

A Fully Autonomous SSHIC Interface Circuit With Configurable Multi-Step Bias-Flip for Piezoelectric Energy Harvesting

This brief presents a piezoelectric energy harvesting interface circuit with a multi-step bias-flip strategy to boost the energy extraction capability. The optimized parallel synchronized switch on inductor and capacitor (SSHIC) technique is adopted. Except for the external inductor and capacitors, the proposed interface circuit is designed for fully integrated control without any external adjustment during the bias-flip process. Moreover, the steps for bias-flip can be configured flexibly, and the circuit can work even without an inductor. The interface circuit has been designed and implemented with 0.18- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\mu }\text{m}$ </tex-math></inline-formula> CMOS technology. With the 5-step bias-flip SSHIC topology and a 1-mH inductor, the simulated whole current dissipation is 106 nA, the measured maximum flipping efficiency is 90.3%, and the measured maximum power efficiency improvement is 642% compared to the ideal full bridge rectifier (FBR).

Artificial visual neuron based on threshold switching memristors

The human visual system encodes optical information perceived by photoreceptors in the retina into neural spikes and then processes them by the visual cortex, with high efficiency and low energy consumption. Inspired by this information processing mode, an universal artificial neuron constructed with a resistor (R s) and a threshold switching memristor can realize rate coding by modulating pulse parameters and the resistance of R s. Owing to the absence of an external parallel capacitor, the artificial neuron has minimized chip area. In addition, an artificial visual neuron is proposed by replacing R s in the artificial neuron with a photo-resistor. The oscillation frequency of the artificial visual neuron depends on the distance between the photo-resistor and light, which is fundamental to acquiring depth perception for precise recognition and learning. A visual perception system with the artificial visual neuron can accurately and conceptually emulate the self-regulation process of the speed control system in a driverless automobile. Therefore, the artificial visual neuron can process efficiently sensory data, reduce or eliminate data transfer and conversion at sensor/processor interfaces, and expand its application in the field of artificial intelligence.

Investigation of external capacitance effects on electrochemical discharge drilling

ABSTRACT Electrochemical discharge drilling (ECDD) involves a combination of electrical discharge drilling (EDD) and electrochemical drilling (ECD) to remove the recast layer while drilling at high speed. Here, a T-RC power supply similar to the EDD method is adopted. However, the solution resistance characteristics change as a result of utilizing a weak conductivity solution instead of deionized water with insulating properties. Different external capacitances will impact ECDD. In this study, through experiment and simulation, the influence of capacitance on the ECDD performance of Ni-based single-crystal alloy is investigated compared to EDD. In the open-circuit stage, the ECDD current shows an exponential relationship, and the voltage drops slightly. The highest line material removal rate reaches 326 μm/s, which is higher than EDD, and the tool wear ratio drops by 40%. The aperture and taper continue to ascend. Finally, no recast layer can be realized over 680 nF.

Enhanced self-sensory measurements for smart carbon-based textile reinforced cement structures

This study explores advanced capabilities of smart carbon-based textile reinforced cement-based elements to monitor its structural health. The goal is to enhance and amplify the electrical measurements and the sensitivity of the electrical readings. To answer these goals, the study develops advanced alternating current (AC) based electrical measurement setups. The study also offers to use a new cementitious matrix with enhanced mechanical, rheological and electrical properties. To amplify the measurement, the study suggests measuring the electrical changes at the resonance frequency of the system, which can be done by connecting external capacitors to the embedded carbon roving. A comparison investigation is performed to explore the monitoring capabilities of four electrical measurement setups at various structural states. Eight textile and fibers reinforced cement-based beam specimens were investigated under flexural loading. It is found that by connecting an external parallel capacitor to the roving, amplified, stable and sensitive electrical measurements are achieved.

Ka-Band Three-Stack CMOS Power Amplifier with Split Layout of External Gate Capacitor for 5G Applications

In this study, we designed a Ka-band two-stage differential power amplifier (PA) using a 65 nm RFCMOS process. To enhance the output power of the PA, a three-stack structure was utilized in the power stage, while the driver stage of the PA was designed with a common-source structure to minimize power consumption in the driver stage. The layout of an external gate capacitor for the stacked power stage was split to maximize the performance of the power transistor. With the proposed split layout of the external capacitor, gain, output power, and power-added efficiency (PAE) were improved. Additionally, a capacitive neutralization technique was applied to the power and driver stages to ensure the stability and enhance the gain of the PA. The measured P1dB and the saturation power were 22.0 dBm and 23.3 dBm, respectively, while the peak PAE was 27.8% at 28.5 GHz.