Change In Output Voltage Research Articles

Application of the Artificial Neural Network (ANN) Method as MPPT Photovoltaic for DC Source Storage

This paper shows the details of the design of DC-DC Boost Converter as the Maximum Power Point Tracker (MPPT). This technique is used to optimize the potential of energy generated by photovoltaics. The changing of the duty cycle in the switching Boost Converter process will affect the amount of photovoltaic (PV) power output. Boost Converter is chosen because the output voltage of PV arrays is smaller than the DC source storage one. In this study, the Artificial Neural Network (ANN) algorithm has been applied as a method to search as Maximum Power Point (MPP). ANN learning data has been used to adjust the duty cycle of Boost Converter so that the Boost Converter output voltage and current change and the output power reaches MPP, which is the target data. The design results have been implemented using 3 pieces of PV, each one having 100WP of power. The experimental results show that the proposed method can optimize PV output power for DC source storage with an average power increase of 56.22% compared to PV output power without using MPPT control.

Cold-start icing characteristics of proton-exchange membrane fuel cells

Understanding the icing characteristics of proton-exchange membrane fuel cells (PEMFCs) is essential for optimizing their cold-start performance. This study examined the effects of start-up temperature, current density, and microporous layer (MPL) hydrophobicity on the cold-start performance and icing characteristics of PEMFCs. Further, the cold-start icing characteristics of PEMFCs were studied by testing the PEMFC output voltage, impedance, and temperature changes at different positions of the cathode gas diffusion layer. Observation of the MPL surface after cold-start failure allowed determination of the distribution of ice formation at the catalytic layer/MPL interface. At fuel cell temperatures below 0 °C, supercooled water in the cell was more likely to undergo concentrated instantaneous freezing at higher temperatures (−4 and −5 °C), whereas the cathode tended to freeze in sequence at lower temperatures (−8 °C). In addition, a more hydrophobic MPL resulted in two successive instantaneous icing phenomena in the fuel cell and improved the cold-start performance.

A Hybrid Current Mode Controller with Fast Response Characteristics for Super Capacitor Applications

A wide-bandwidth current-controller is required for the fast charging and discharging of applications containing super capacitors. To accomplish this, peak current mode is generally used due to the speed of its response characteristics. On the other hand, peak current mode control must be provided with a slope compensation function to restrain sub-harmonic oscillations. However, if the controlled output voltage is varied, the slope must be changed accordingly. Nonetheless, it is not easy to change the slope for every change in output voltage. Another solution involves the slope being set at the maximum value, which results in a slow response. Therefore, in this paper, a hybrid mode controller was proposed that uses a peak current and a newly-specified valley current. Using the proposed hybrid mode control, sub-harmonic oscillation did not occur for duty cycles larger than 0.5 and response times were fast.

ГЕНЕРАТОРИ ОДНАКОВИХ СТРУМІВ ІЗ ВИСОКИМИ ВИХІДНИМИ ОПОРАМИ ДЛЯ БАГАТОРОЗРЯДНИХ ЦАП

The article discusses the principles of construction of generators of the identical currents with high output resistances for use in multi-bit DACs. Approaches to the construction of generators of the identical currents for multi-bit DACs with primary current generators connected to the output stages by means of current mirrors are considered. Variants of circuits using an additional generator of bias currents and with auto bias in the output stage of generators of the identical currents are shown. The sources of errors that occur when the output voltage changes and affect the output resistance of the current generator are analyzed. Analytical relations are derived for calculating the output resistance value. Computer simulation of identical current generators for multi-bit DACs was carried out using the integrated software package for analog and digital simulation of electrical and electronic circuits MicroCap 11 and the correctness of the derived relations was confirmed. The approaches to the construction of generators of the identical currents for multi-bit DACs with primary current generators connected directly to the output stages are considered. Variants of this scheme using an additional bias current generator and with auto-bias in the output stage of current generators are also shown. The sources of errors that occur when the output voltage changes and affect the output resistance of the current generator are analyzed. Analytical relationships are derived for calculating the output impedance values ​​and computer simulation of generators of identical currents is carried out using a program for modeling electrical and electronic circuits and the correctness of the derived relationships is confirmed. Modifications of the above mentioned schemes with extremely large output impedance are considered. For these schemes analytical relationships for calculating the output impedance values ​​are also derived and computer simulation is carried out and the correctness of the derived relationships is also confirmed. The parameters of the considered generators of the identical currents for multi-digit DACs are compared, their advantages and disadvantages are evaluated, and recommendations for their use are provided.

Self-Inductance-Based Metal Object Detection With Mistuned Resonant Circuits and Nullifying Induced Voltage for Wireless EV Chargers

In this paper, a metal object detection (MOD) system, a kind of foreign object detection (FOD), which is based on mistuned resonant circuits and utilizes the variation of self-inductance of a sensing pattern, is newly proposed for wireless electric vehicle (EV) chargers. The sensing pattern that consists of multiple loop coil sets is mounted on the transmitting (Tx) pad of an EV charger, where a loop coil set has two coils connected in series with the opposite polarity to cancel out the induced voltage generated by the Tx coil. Variation of self-inductance of the loop coil set is detected by a parallel-resonant circuit, driven by a current source and operating at near 1 MHz, in order to enhance the resolution of the proposed MOD system. To increase the detection sensitivity of the proposed MOD system, instead of an exact resonant frequency, a mistuned operating frequency near the –3 dB point is utilized for the parallel-resonant circuit. In this way, the proposed MOD system can detect very small metal objects regardless of their position and orientation on the Tx coil without any blind zone. Through simulations and experiments, it is found that the proposed MOD system detects not only horizontal but also standing upright metal objects. A prototype MOD system, operating at 85 kHz to satisfy the standard J2954, was fabricated to verify its feasibility. The results showed that output voltage change of the proposed MOD system becomes 22.7% for a piece of the aluminum foil of 3 × 3 cm2 and 40.9% for 100 Korean Won coin.

Memristor-Based Circuit Implementations of Recognition Network and Recall Network With Forgetting Stages

This paper proposes a novel memistor-based neuron circuit, in which the memristor-CMOS hybrid synaptic circuit simply utilizes the positive voltage to change the memristance. At the same time, in order to obtain the memristance and output voltage changes in the neuron circuit, a mathematical deduction is implemented according to the circuit structure. Then, the memristor-based recognition and recall network circuits are constructed based on the proposed neuron circuit. The recognition and recall functions are realized by associative learning between the unconditional stimuli and the conditional stimuli (CS). After the learning stages, the single presentation of CS activates forgetting stages in the two networks. Furthermore, the related parameter changes in the learning and forgetting stages can be calculated by the deduced equations approximately. The PSPICE simulations are implemented to demonstrate the effectiveness of the proposed circuits and the deduced equations.

Analysis, Design, and Implementation of Improved LLC Resonant Transformer for Efficiency Enhancement

In battery charging applications, the charger changes its output voltage in a wide range during the charging process. This makes the design of LLC converters difficult to be optimized between the efficiency and the gain range. In this paper, an improved resonant transformer is presented for LLC resonant converter charger to improve the gain adjustment and charger efficiency. The resonant inductance and magnetizing inductance are integrated in the designed LLC transformer, and the magnetizing inductance can be adjusted dynamically with the change of output voltage and load, which is realized by a switch-controlled inductor (SCI) parallel to the secondary winding of transformer. The proposed transformer has 22.4% reduction in losses under full load conditions compared to conventional solutions. Moreover, the conduction loss and switching loss of LLC resonant tank are reduced by dynamically adjusting the magnetizing inductance, which improves the comprehensive efficiency of the whole charging process. The proposed transformer design is verified on a 720 W prototype.

Integrated 240-GHz Dielectric Sensor With dc Readout Circuit in a 130-nm SiGe BiCMOS Technology

This paper presents a high-integration miniaturized dielectric spectroscopy system for sensing the change of permittivity at 240 GHz in the SiGe BiCMOS technology. The sensor features a transducer with a resonator to perform bandpass frequency response, whose complex value of $S_{21}$ is varied with the permittivity of the sample under test. This variation can be detected and recorded as the change of amplitude and phase of the 240-GHz in-phase and quadrature direct conversion mixer. An external 30-GHz source is employed with cascade frequency multiplier chain to deliver a signal through the system with a wide tuning range of 215–245 GHz. An additional probe is employed to carry the sample and implement chip measurements on the probe station. The sensing function of this system is performed with the leaded wire as a metallic sample to be placed on the top of the transducer. Based on the measured dc output voltage changes, the calculated magnitude and phase of IQ signal in the 215–245-GHz range are used to estimate the complex permittivity change of MUTs. This dielectric spectroscopy system is also suitable for sensing the complexy permittivity change at higher frequencies in the future terahertz Lab-on-Chip measurements.

Introducing Self-Oscillating Technique for a Soft-Switched LED Driver

In this paper, a self-oscillating soft-switched converter for light-emitting-diode (LED) driver application is presented. In the proposed converter, the self-oscillation conditions are provided with a low number of additional components, and this converter provides a zero-current switching (ZCS) condition for instant switch turn- OFF . This converter does not need additional output current feedback because the output current changes only 10% when the output voltage changes by 33%. The self-oscillating part of this converter applies three low-power BJT and guarantees a soft-switching condition. The proposed self-oscillating control circuit can be implemented with a low cost since it does not need any IC and power supply for the control circuit. The proposed self-oscillating circuit detects the proper moment to turn the switch OFF under the ZCS condition. In order to justify the validity of theoretical analysis, the results of the implemented prototype for driving an LED string are presented. The measured power factor of the prototype shows that, although the input current of the converter is not sinusoidal, this converter can meet the IEC61000-3-2 standard at an operating power of less than 25 W, in addition to having a simple structure and achieving the robust ZCS condition.

Liquid-State Environment Sensors Using Liquid Metal

Flexible devices have many potential applications in wearable electronics, robotics, health monitoring, and more. Mechanically deformable devices and sensors such as flexible devices enable conformal coverage of electronic systems on curved and soft surfaces. Sensors utilizing liquids confined in soft templates as the sensing component present the ideal platform for such applications, as liquids are inherently more deformable than solids. However, to date, current liquid-metal based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart-rate monitoring which require much lower pressure detection resolution. In addition, liquid-based devices have been limited to metal lines based on a single liquid component given the difficulty in the fabrication of liquid-based junctions due to intermixing. Here we demonstrate state-of-art microfluidic environmental sensors using liquid metal, highly sensitive pressure sensor based on tactile diaphragm pressure sensor, and temperature/humidity/oxygen sensors with mechanically robust liquid-liquid “heterojunction”. This report will present an important advancement towards the realization of liquid-state electronic systems. Introduction Electronic devices and sensors which exhibit large amounts of mechanical deformability have many applications such as in smart wallpapers and human-machine interfaces for prosthetics. In this regard, tremendous advancements have been made in engineering solid-state electronic materials and devices on elastic substrates. Recently, sensors based on using liquid active components embedded within soft elastomeric substrates have shown much promise for such applications as liquids present the ultimate limit in deformability. In this paper, we report four microfluidic sensors using liquid metals, highly sensitive pressure sensor based on tactile diaphragm pressure sensor, and temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”. The work presents an important step towards the potential realization of liquid-state electronic systems that offer new form factors and functionality. Current Result < Microfluidic diaphragm pressure sensor> In both sensors, the devices were fabricated by photolithography techniques using poly(dimethylsiloxane) (PDMS) as the substrate, and eutectic GaInSn (Galinstan) as electrodes. A microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width 70 µm height) capable of resolving sub-50 Pa changes in pressure with sub-100 Pa detection limits and a response time of 90 ms is demonstrated(Fig. 1). An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of 0.0835 kPa-1 change in output voltage. The Wheatstone bridge also provides temperature self-compensation, allowing for operation in the range of 20-50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real time pulse monitoring(Fig. 2) and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated(Fig. 3). <Temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”> In termes of temperature/humidity/oxygen sensors with liquid-liquid “heterojunction”, liquid metal was used as electrode, and ionic liquids as a sensing material(Fig. 4 and 5). As shown in Fig. 6, equivalent circuit of the sensors were established based on Nyquist plot The sensor showed stable sensitivity to temperature without hysteresis as shown in Fig. 7 with a 0.039/°C increase in conductivity, which is quite high compared to other reports. We also show proof of concept for humidity and oxygen gas sensing using three kinds of ionic liquids, 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIM][Otf]), 1-Butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF6]), and 1-Butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([BMPYR][NTf2]). As shown in Fig. 7, the sensitivity of each ionic liquid to humidity and oxygen differed depending on the ionic liquid. For each type of stimuli, the sensing can be optimized by choosing the proper ionic liquid. In the future, multiple liquid heterojunction sensors, each with a different ionic liquid may be multiplexed into a fully integrated system to sense different stimuli with calibrated response. Figure 1

Investigation of VDMOSFET's switching power dissipation changes under constant electrical stress

This study aims to examine the electrical stress effects on the switching power dissipation in n-channel VDMOSFET. We set up a resistive load NMOS inverter as a test circuit. At first step of measurement, VDMOSFETs are subjected to the high constant voltage (55VDC) up to 6 h and this degradation process is continued until just prior to the oxide breakdown. Stress induced changes in output voltage and current are extracted using the resistive load NMOS inverter. The static and dynamic power dissipations, and power-delay product are calculated accordingly. In addition, assuming that the inverter load is selected as n-channel VDMOSFET, the power dissipation is calculated. In resistive load NMOS inverter, it is observed that the static power dissipation is decreased by 5.3%, the dynamic power is increased by around 60% and the total power dissipation is decreased by 5% compared to before the stress. In enhancement load NMOS inverter, the total power dissipation has a decrease of around 92%.

Wheatstone bridge-giant magnetoresistance (GMR) sensors based on Co/Cu multilayers for bio-detection applications

A Wheatstone bridge-giant magnetoresistance (GMR) sensor was successfully developed for a potential biomaterial detection. In order to achieve this, a giant magnetoresistive [Co(1.5nm/Cu(1.0nm)]20 multilayer structures have been fabricated by DC magnetron sputtering method, showing a magnetoresistance (MR) of 2.7%. The X-Ray diffraction (XRD) patterns showed that Co/Cu film multilayer has a high degree of crystallinity with a single peak corresponding to face-centered cubic (111) structure at 2θ = 44.1°. Co/Cu multilayers exhibit a soft magnetic behavior with the saturation magnetization (Ms) of 1489 emu/cc and the coercivity (Hc) of 11.2 Oe. The magnetite Fe3O4 nanoparticles used as a bimolecular labels (nanotags) were synthesized via co-precipitation method, exhibiting a soft magnetic behavior with Ms of 77.16 emu/g and Hc of 49 Oe. XRD patterns and transmission electron microscopy (TEM) images showed that Fe3O4 was well crystallized and it grew in their inverse spinel structure with an average size of around 10 nm. The GMR sensor design was used to detect a biomolecules of streptavidin magnetic particles with concentration 10, 20, 30, and 40 μl/ml and α-amylase enzyme with consentration 10, 20, 30, and 40 μl/ml captured using polyethylene glycol (PEG)/Fe3O4 nanoparticles. Various applied magnetic fields of 0-650 Gauss have been performed using electromagnetic with the various currents of 0-5 A. Here, the final value of the output voltage signals for the streptavidin magnetic particles concentration is 1.2 mV (10 μl/ml). The output voltage changes with the increase of concentration. It was reported that the output voltage signal of the Wheatstone bridge exhibits log-linear function in real time measurement of the concentration of streptavidin magnetic particles and α-amylase enzyme respectively, making the sensor suitable for use as a biomolecule concentration detector. Thus, the combination of Co/Cu multilayer, Wheatstone bridge, magnetite and PEG polymer has potential application to be used in bio-detection applications where ultra-small bio-labels are needed.

A 10-MHz 2–800-mA 0.5–1.5-V 90% Peak Efficiency Time-Based Buck Converter With Seamless Transition Between PWM/PFM Modes

Time-based controllers are well suited for implementing both single- and multi-phase wide bandwidth high switching frequency pulsewidth modulation (PWM)-based dc–dc converters. They also consume very little quiescent current but their light load efficiency is severely degraded by switching losses. We explore pulse frequency modulation (PFM) that is commonly used to improve light load efficiency in voltage-mode controllers and extend its operation to time-based controllers. To maintain high efficiency even in the presence of dynamic load variations, we present techniques to perform automatic and seamless switching between PWM/PFM modes. Fabricated in a 65-nm CMOS, the prototype buck converter using the time-based PWM/PFM control achieves 90% peak efficiency and >80% efficiency over a load current range of 2–800 mA. Output voltage changes by less than 40 mV during PWM to PFM transitions.

High resolution DPWM clustered architecture for digitally controlled DC–DC converter using FPGA

Several researches have been done in literature to improve the resolution of pulse mode architectures used for controlling the DC–DC converters. Resolution can be measured as the number of bits used for representing the duty cycle control input [1]. Higher the resolution of control inputs more precisely the changes in output voltage with DC–DC converter can be addressed [2]. Traditional architectures implemented with counter and other delay line structure occupies large area and also has less throughput with an increase in number of control inputs. But the DC–DC converters used in portable and mobile based applications must be compact and consumes low power [3]. This proposed DPWM architecture uses Block RAM available in FPGA to store the binary bit patterns to derive variable duty cycle pulses [4]. The architecture is proposed for three different control inputs like four bit, three bit and two bit control inputs. This proposed architecture for a four bit control input can address 4096 bit patterns and has maximum operating clock frequency of 306.84 megahertz (MHz).

Pulmonary repercussions in patients with Fabry disease

We report on InGaZnO (IGZO) thin film transistors (TFTs)-based bio-chemical sensors which can detect the chemical/biological species. As novel sensing platform, the IGZO TFT with Ag nanowire (NW) mesh showed pronounced output voltage changes responding to all analytes of H2O2, b-d-glucose, d-glucono-1,5-Lactione, and lactic acid, which are reproducible and reversible. Herein, porous Ag NW-functionalized top gate electrode plays a major role in sensing platform for enhanced sensing capability in aqueous medium. Moreover, these top gate geometry serve as a stable backplane for electrical modulation. As a result, analytes solutions become acidic or basic and such pH alterations induce significant turn-on voltage shifts on our devices. For implementation of a resistive load inverter, the output sensing voltage signals can be directly extracted, and such signals are reproducible and reversible. The proposed IGZO TFTs with Ag NW mesh top gate electrode based sensing platform pave the way for development of portable and reusable real-time non-destructive label-free chemical/biological sensors.

Optical-Interferometry-Based CMOS-MEMS Sensor Transduced by Stress-Induced Nanomechanical Deflection.

We developed a Fabry–Perot interferometer sensor with a metal-oxide-semiconductor field-effect transistor (MOSFET) circuit for chemical sensing. The novel signal transducing technique was performed in three steps: mechanical deflection, transmittance change, and photocurrent change. A small readout photocurrent was processed by an integrated source follower circuit. The movable film of the sensor was a 350-nm-thick polychloro-para-xylylene membrane with a diameter of 100 µm and an air gap of 300 nm. The linearity of the integrated source follower circuit was obtained. We demonstrated a gas response using 80-ppm ethanol detected by small membrane deformation of 50 nm, which resulted in an output-voltage change with the proposed high-efficiency transduction.

A novel fabrication method for co-integrating ISFET with damage-free sensing oxide and threshold voltage-tunable CMOS read-out circuits

A novel fabrication method using a top SiO2-SiN-bottom SiO2 (ONO) dielectric stack is proposed and implemented to obtain ion sensitive field effect transistor (ISFET) with damage-free sensing oxide and threshold voltage (Vth)-tunable devices in CMOS read-out circuits. By wet-etching the top SiO2 and the SiN sequentially, the ISFET with damage-free sensing oxide is obtained due to the high selectivity between them. Also, the Vth-tunable circuit devices with the ONO stacks are simultaneously achieved by protecting the ONO stacks from the wet-etching. Through the measurements of pH and biomolecule responses, it is confirmed that the pH and biomolecule can be detected stably because the drain current (ID) is stabilized to a predetermined value more quickly and the ID fluctuation during the ID stabilization is significantly reduced compared with devices having damaged sensing oxide. Additionally, it is verified that the Vth of devices for circuits can be fine-controlled by injecting charges into the SiN via Fowler-Nordheim tunneling. Furthermore, it is demonstrated that the biomolecule-induced Vth shift of ∼150 mV in the proposed ISFET is successfully amplified to the output voltage change of ∼370 mV in common source amplifier (CSA) voltage-readout circuit consisting of one p-type ISFET and one Vth-tuned n-type MOS.

Optimizing Temperature Coefficient and Frequency Response of Rogowski Coils

This paper describes a new method for optimizing both Rogowski coil’s temperature coefficient and its high frequency response. The proposed scheme is based on finding a value for coil termination resistance and for its temperature coefficient, which result in negligible change of coil output voltage versus temperature while still allowing for any damping ratio desired. The method is tested in a proof-of-concept setup with an openable, rigid Rogowski coil. The result shows that a well-damped LC-resonance of the coil is possible without having to make a compromise with temperature coefficient and vice versa. The proof-of-concept measurement is done for a broad temperature range around room temperature and works for any range where the coil‘s temperature expansion is sufficiently linear. At the same time, the frequency response is preserved, giving an extension of at least an order of magnitude with respect to previous work.

A practical approach to comparative design of non-contact sensing techniques for seed flow rate detection

This study, as a part of a broader research project on development of a seed drill performance monitoring system, seeks to make a practical approach to comparative design of non-contact sensing techniques for seed flow rate detection. To determine actual flow rate, various non-contact sensing techniques have been proposed by other researchers. The methods of light dependent resistors (LDR), infrared (IR), and laser diodes (LD) drew more attention. LD, IR, and LDR sensing units were successfully designed and developed. Each of these sensors has a type of LEDs, consist of infrared, visible light and laser-LED as well as an element as a radiation receiver. When the seeds pass through the seed sensor and through the band of light beams, their shades fall on the receiver elements, resulting in output voltage changes. Thus, the seed flow rate could be estimated by investigating signal information corresponding to the passing seeds. A particular test apparatus was designed to compare proposed sensing units ability in confronting with the same seed flow. For each seed flow rate in experiments, individual LDR, IR, and LD, pulse signals and discharged seeds mass were recorded. Results show that there is a strong linear relationship (r=0.87) between the actual seed mass changes and the corresponding voltages of IR sensing unit. Due to obtained results in comparison with other investigated sensing methods, it is recommended that IR detection technique is a more proper non-contact sensing technique for estimating of the seed flow rate.

Wearable Microfluidic Diaphragm Pressure Sensor for Health and Tactile Touch Monitoring.

Flexible pressure sensors have many potential applications in wearable electronics, robotics, health monitoring, and more. In particular, liquid-metal-based sensors are especially promising as they can undergo strains of over 200% without failure. However, current liquid-metal-based strain sensors are incapable of resolving small pressure changes in the few kPa range, making them unsuitable for applications such as heart-rate monitoring, which require a much lower pressure detection resolution. In this paper, a microfluidic tactile diaphragm pressure sensor based on embedded Galinstan microchannels (70 µm width × 70 µm height) capable of resolving sub-50 Pa changes in pressure with sub-100 Pa detection limits and a response time of 90 ms is demonstrated. An embedded equivalent Wheatstone bridge circuit makes the most of tangential and radial strain fields, leading to high sensitivities of a 0.0835 kPa-1 change in output voltage. The Wheatstone bridge also provides temperature self-compensation, allowing for operation in the range of 20-50 °C. As examples of potential applications, a polydimethylsiloxane (PDMS) wristband with an embedded microfluidic diaphragm pressure sensor capable of real-time pulse monitoring and a PDMS glove with multiple embedded sensors to provide comprehensive tactile feedback of a human hand when touching or holding objects are demonstrated.