Turn-on Time Research Articles

Dynamic switching operation of diamond MOSFETs with NO2 p-type doping and Al2O3 gate insulation and passivation

Diamond metal–oxide–semiconductor field-effect transistor (MOSFET) exhibited durable and stable dynamic switching characteristics at an unprecedentedly high voltage of −105 V. Switching turn-on and turn-off times were measured to be 7.64 and 4.93 ns, respectively, with a corresponding total switching loss of 20.03 pJ for a load resistance of 50 Ω. No Miller effect was observed due to the low Miller capacitance of 11 pF/mm. This study suggests the potentiality of diamond MOSFETs in prospective high-voltage, high-speed applications.

Cold Filaments Formed in Hot Wake Flows Uplifted by Active Galactic Nucleus Bubbles in Galaxy Clusters

Multiwavelength observations indicate that the intracluster medium in some galaxy clusters contains cold filaments, while their formation mechanism remains debated. Using hydrodynamic simulations, we show that cold filaments could naturally condense out of the hot gaseous wake flows uplifted by jet-inflated active galactic nucleus (AGN) bubbles. Consistent with observations, the simulated filaments extend to tens of kiloparsecs from the cluster center, with a representative mass of 108–109 M ⊙ for a typical AGN outburst energy of 1060 erg. They show smooth velocity gradients, stretching typically from inner inflows to outer outflows with velocity dispersions of several hundred kilometers per second. The properties of cold filaments are affected substantially by the jet properties. Compared to kinetic-energy-dominated jets, it is easier for thermal-energy-dominated jets to produce long cold filaments with large masses, as observed. AGN jets with an early turn-on time, a low jet base, or a very high power tend to overheat the cluster center and produce short cold filaments that take a relatively long time to condense out.

Experience of using evaporative cooling of graphitized electrodes to reduce their consumption in ore smelting furnaces

Consumable graphitized electrodes (GE) are widely used for supplying current to AC and DC EAF's, ore-smelting and indirectly heated electric arc furnaces. Due to large current, thermal and mechanical loads, their consumption in the structure of the cost of smelting in some cases, for example, in steel smelting reaches 30 %. Considering this, as well as the unstable global economic situation, when many enterprises use imported electrodes, solving the issue of reducing them is urgent. Foreign-made arc steel furnaces with a capacity of 100 tons and more successfully use evaporative cooling (EC) technology. Its use leads to a reduction in graphite consumption by an average of 10–15 %. However, for ore-thermal furnaces, no data on the experience of using EC GE has been found in the literature. The purpose of the work is to study the possibility of reducing the temperature and consumption of GE in arc ore-smelting furnaces when using EC technology. Experimental studies were carried out at the enterprise PC “AVISMA” (Berezniki), which includes three ore-smelting furnaces with a capacity of 100 tons. For the graphite electrodes used in these furnaces, modeling of their thermal state was performed with and without EC. Rational technological parameters of the cooling process were determined: water flow 1.5 m3/h and system turn-on time 5–15 minutes from the start of the current supply. An experimental design of the EC ring and a system for monitoring water and air flow have been developed. As a result of several heats, a decrease in the surface temperature of the GE was recorded when using EC with water on its side surface and a number of shortcomings were identified. Recommendations for improving technology and improving the design of the AI system are formulated

Dynamic laser ablation loading of a linear Paul trap

We present a detailed method for accumulating Ca+ ions controllably in a linear Paul trap. The ions are generated by pulsed laser ablation and dynamically loaded into the ion trap by switching the trapping potential on and off. The loaded ions are precooled by buffer gas and then laser-cooled to form Coulomb crystals for verifying quantity. The number of ions is controlled by manipulating the trapping potential of the ion trap, partial pressure of buffer gas and turn-on time of the entrance end cap voltage. With single-pulse laser ablation, the number of trapped ions ranges from tens to ten thousand. The kinetic energy of loaded ions can be selected via the optimal turn-on time of the entrance end cap. Using multiple-pulse laser ablation, the number is further increased and reaches about 4×104 . The dynamic loading method has wide application for accumulating low-yielding ions via laser ablation in the ion trap.

Comparative Study of Different High Voltage Switches Used in Pulsed High Voltage Application

High-voltage switches play a crucial role in pulsed power applications, where the efficient and reliable control of highvoltage pulses is required. This study aims to compare different types of high-voltage switches commonly used in pulsed power systems including electromechanical switches, vacuum switches, gas-filled switches, triggered spark gaps and solidstate switches. The comparison study focuses on key performance parameters such as voltage handling capability, current carrying capacity, turn-on time, and repetition rates are considered to provide a comprehensive study and analysis of the switch’s suitability for different pulsed power applications. Gas-filled switches such as spark gaps, thyratrons and ignitrons have been used in pulsed power systems due to their high voltage handling capability and low switching losses. However, they suffer from a limited lifetime and require maintenance and periodic replacement. Solid-state switches, i.e. Silicon-Controlled Rectifiers (SCRs), Insulated Gate Bipolar Transistors (IGBTs) and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) offer advantages in terms of longevity, reliability, and reduced maintenance. However, they have limitations in high-voltage applications and exhibit higher switching losses. The findings of this comparison study will assist researchers, engineers, and system designers in selecting the most appropriate high-voltage switch for pulsed power applications, considering the specific requirements and constraints of the system. This will ultimately contribute to the advancement and optimization of pulsed power technologies across a wide range of scientific, industrial, and strategic applications.

A 4H-SiC p-channel insulated gate bipolar transistor with higher breakdown voltage and superior V F·C res figure of merit

A silicon carbide p-channel insulated gate bipolar transistor (IGBT) with higher breakdown voltage (BV) and low V F·C res figure of merit (FOM) has been simulated, fabricated, and characterized successfully. The proposed IGBT adds two n-type implant regions in the junction FET (JFET) area and increases the gate oxide thickness above the JFET area to reduce the reverse transfer capacitance (C res) and gate oxide electric field (E ox). The proposed structure notably lowers E ox below 3 MV cm−1 while elevating the BV to 16.6 kV. A new FOM of V F·C res is defined to evaluate the trade-off between the on-state and the C res characteristics. The experimental results demonstrate that a lower V F·C res FOM of 0.369 V·pF is achieved from the proposed IGBT with a reduction of 66.4%, compared to the conventional current spreading layer IGBT. Meanwhile, the simulated turn-on and turn-off times of the proposed IGBT are reduced by 29.4% and 20%, respectively.

A closer look to the factors affecting the switching transient times of optocouplers

The significant parameters for a high-speed optoelectronic switch were the transient times. In the time domain, there is a time elapsed on the order of microseconds between applying a current pulse and seeing an output. Therefore, the present work aimed to give a closer look on the factors affecting the transient times of the optocoupler switching action, namely; delay (td)-, rise (tr)-, in addition to storage (ts)- and fall (tf)-times. The turn-on time (Ton = td + tr) and turn-off time (Toff = ts + tf) of the optocoupler (type 4N25) were investigated and plotted under the influence of different operating conditions such as: load resistance (RL), forward LED drive current (IF), bias collector voltage (VCC), emitter–base resistance (RBE), and ambient temperature.

Intelligent Personalized Lighting Control System for Residents

The demand for personalized lighting environments based on households is steadily increasing among users. This article proposes a novel intelligent control system for personalized lighting in home environments, aiming to automatically capture user information, such as homecoming time and light switching behavior, in order to train a model that intelligently regulates the lights for users. Facial recognition technology is employed by this system to identify users and record their lighting data. Subsequently, nine commonly used machine learning models were evaluated, revealing that the error back-propagation neural network algorithm exhibits excellent performance in time-series analysis. The BPNN weights were optimized using genetic algorithms, resulting in an improved coefficient of determination (R2) of 0.99 for turn-on time and 0.82 for turn-off time test sets. Furthermore, testing was conducted on data collection duration which demonstrated that even with only 20 time-series data collected from new users, the model still displayed exceptional performance in training prediction tasks. Overall, this system effectively identifies users and automatically adjusts the lighting environment according to their preferences, providing comfortable and convenient lighting conditions tailored to individual needs. Consequently, a broader goal of energy conservation and environmental sustainability can be achieved.

Novel Control Approach for Resonant Class-DE Inverters Applied in Wireless Power Transfer Systems

Regulating the load voltage is of major importance for ensuring high transmission efficiency in wireless power transfer (WPT) systems. In this context, this work presents a novel control strategy applied in the dc-ac converter used in the primary side of a WPT system. The performance of a class-DE resonant inverter is investigated considering that such topology presents inherent soft-switching characteristics, thus implying reduced switching losses. The controller relies on an autoregressive with exogenous output (ARX) model based on an adaptive linear neuron (ADALINE) network, which allows for determining the turn-on time of the active switches accurately while providing the system with the ability to adapt to distinct alignment conditions. The performance of the proposed controller is compared with that of a linear controller, which does not prove to be an effective solution if misalignment occurs.

A Pulsewidth Adjustable Trigger Method for Reverse Blocking Diode Thyristor to Suppress Current Filamentation and Improve di/dt Capability

In this paper, to suppress the current filamentation and improve di/dt capability, a pulse width adjustable trigger method based on Marx generator for reverse blocking diode thyristor (RBDT) is proposed. The importance of trigger voltage pulse width for RBDT is firstly illustrated. The influence of the width of the voltage trigger pulse on RBDT is simulated in TCAD and verified by experiments. It is turned out that the turn-on delay time can be reduced when the width of voltage trigger pulse is shorter than 800ns. When the width of the voltage trigger pulse further increases, the turn-on delay time becomes saturated. It is shown in the simulations that wider trigger voltage pulse can suppress the current filamentation in RBDT. The simulation result is validated by comparative experiments with two different widths of voltage trigger pulse generated by Marx generator at different main voltages. The switching loss of RBDT triggered by voltage pulse width of 1000ns is smaller than that by voltage pulse width of 240ns under the same condition. Besides, RBDT triggered by voltage pulse width of 1000ns can even survive when the maximum di/dt per unit area is about 16.7kA/μs/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> at the main voltage of 970V. However, RBDT triggered by voltage pulse width of 240ns fails at the main voltage of 920V. Finally, the sensitivity of the proposed trigger method is verified.

Effects of Synchronous Bias Mode and Duty Cycle on Microstructure and Mechanical Properties of AlTiN Coatings Deposited via HiPIMS

The good mechanical properties of metal nitrides make them ideal surface coatings for cutting tools and mold components. Conventional TiN coatings have largely been replaced by AlTiN due to their superior mechanical properties and resistance to high temperatures. In this study, we investigated the application of bias voltage to the substrate to enhance ion bombardment during the synthesis of protective AlTiN coatings using high-power impulse magnetron sputtering (HiPIMS) with synchronous trigger-direct current (ST-DC) bias voltage. The ST-DC parameters included the duty cycle duration (3%, 6%, 12%, 18%) and turn-on time, which included synchronous (TD0) or a trigger delay of 50 μs (TD50). Scanning electron microscope images revealed that the highest deposition rate (22.1 nm/min) was achieved using TD50 with a duty cycle of 3%. The results obtained using an electron probe microanalyzer and X-ray diffractometer revealed the formation of an h-AlN structure when the Al/Ti ratio was between 0.71 and 0.74. Transmission electron microscopy and nanoindentation results revealed that transforming DC bias into synchronous bias to boost the bias output time (i.e., increasing the duty cycle) increased AlTiN grain refinement (from ~100 nm to ~55 nm) with a corresponding increase in hardness (from 22.7 GPa to 24.7 GPa) as well as an increase in residual stress within the AlTiN coating (from 0.16 GPa to −51 GPa). The excellent adhesion performance of the coatings provided further evidence indicating the importance of duty cycle and trigger delay when using pulsed-DC bias in HiPIMS.

An Improved High Voltage Pulse Generator With Few Nanoseconds Based on the Synergy of DOS and LTD Topologies for Supra Electroporation

Supra electroporation, also known as nanoelectroporation, induced by nanosecond pulse could increase organelle membrane permeability with negligible effect on cell membrane, which has been used for tumor treatment through immunogenic cell death. In order to investigate the supra electroporation of organelle membrane, this study proposes a new topology to generate high voltage pulse with few nanoseconds. This circuit topology contains two main stages: firstly, the topology of diode opening switch (DOS) with LC resonance boosting is used to generate few nanoseconds pulse. Secondly, for improving the output/input voltage gain, four DOS modules are optimally connected (two modules in parallel and another two modules in series) using linear transformer driver (LTD) structure. Moreover, the turn-ON time of MOSFET switch and the inductance of LTD windings are optimized to further boost the voltage amplitude. Finally, experimental results validate the functionality of the proposed topology. The output/input voltage gain can reach 24. This generator can output the nanosecond pulses with full width half maximum (FWHM) of 5.1 ns, amplitude of 3.7 kV (input voltage is 0.15 kV), and repetition frequency up to MHz with unipolar and bipolar polarity in burst mode.

Influence of Acceptor Incomplete Ionization in p&lt;sup&gt;+&lt;/sup&gt; Emitter on SiC LTT with n-Type Blocking Base

Influence of acceptor incomplete ionization in p+ emitter on characteristics of SiC LTT with n-type blocking base was investigated in this work through TCAD simulation. The incomplete ionization model in the p+ emitter was shielded for comparison of the influence of acceptor complete ionization status. The minimum triggering intensity, forward on-state voltage drop, turn-on delay time and anode voltage falling time were simulated and discussed. The simulation results indicated that the acceptor incomplete ionization in p+ emitter makes the minimum triggering intensity, forward on-state voltage drop, switch-on delay time and anode voltage falling time increase by about 3.0 times, 1.24 times, 22% and 2.55 times, respectively.

Synchronous rectification of LLC resonant converters based on resonant inductor voltage

Synchronous rectification (SR) technology has been a critical technology for LLC converters to achieve high efficiency and power density. However, conventional SR driving methods face challenges in terms of light-load condition, module size, switching accuracy, and circuit complexity. This paper proposes an SR driving strategy based on resonant inductor voltage (RLV) to address those issues. This RLV-SR driving strategy does not require current sensors and is insensitive to rectifier parasitic parameters. In addition, the RLV-SR driving strategy can be applied in a relatively wide operating frequency range and load conditions. Experimental results based on a 100-W/24-V LLC converter are presented to verify the effectiveness of the proposed RLV-SR driving strategy. Furthermore, the error of turn-on time caused by stray inductance is significantly reduced compared with the conventional VDS-ON sensing method, which improves the power converter’s efficiency.

CMOS-Compatible Tellurium/Silicon Ultra-Fast Near-Infrared Photodetector.

High-quality photodetectors are always the main way to obtain external information, especially near-infrared sensors play an important role in remote sensing communication. However, due to the limitation of Silicon (Si) wide bandgap and the incompatibility of most near infrared photoelectric materials with traditional integrated circuits, the development of high performance and wide detection spectrum near infrared detectors suitable for miniaturization and integration is still facing many obstacles. Herein, the monolithic integration of large area tellurium optoelectronic functional units is realized by magnetron sputtering technology. Taking advantage of the type II heterojunction constructed by tellurium (Te) and silicon (Si), the photogenerated carriers are effectively separated, which prolongs the carrier lifetime and improves the photoresponse by several orders of magnitude. The tellurium/silicon (Te/Si) heterojunction photodetector demonstrates excellent detectivity and ultra-fast turn-on time. Importantly, an imaging array (20 × 20 pixels) based on the Te/Si heterojunction is demonstrated and high-contrast photoelectric imaging is realized. Because of the high contrast obtained by the Te/Si array, in comparison with the Si arrays, it significantly improve the efficiency and accuracy of the subsequent processing tasks when the electronic pictures are applied to artificial neural network (ANN) to simulate the artificial vision system.

Study on changes in electrical and switching characteristics of NPT-IGBT devices by fast neutron irradiation

We studied the irradiation effects of fast neutron generated by a 30 MeV cyclotron on the electrical and switching characteristics of NPT-IGBT devices. Fast neutron fluence ranges from 2.7 × 109 to 1.82 × 1013 n/cm2. Electrical characteristics of the IGBT device such as I–V, forward voltage drop and additionally switching characteristics of turn-on and -off were measured. As the neutron fluence increased, the device's threshold voltage decreased, the forward voltage drop increased significantly, and the turn-on and turn-off time became faster. In particular, the delay time of turn-on switching was improved by about 35% to a maximum of about 39.68 ns, and that of turn-off switching was also reduced by about 40%–84.89 ns, showing a faster switching.

A novel digital sensor-less synchronous rectification method for CLLLC resonant converters

With the rapid development of the renewable energy vehicles, pursuing the power converters with high efficiency and high reliability has caught more attention recently. In order to solve those problem with low cost, this paper proposes a sensor-less synchronous rectification method for the CLLLC resonant converters. The precise conduction time of the synchronous switches is obtained based on the analysis of the working principle of CLLLC resonant converter, and the relationship between the SRs switching time and the inverter switching time can be derived as well. To achieve the wide output voltage range, the converter requires wide working frequency. And the correct turn-on and turn-off time for the synchronous switches can be obtained respectively by calculation and piecewise linear function fitting methods within full working frequency range. Compared with traditional synchronous rectification control for CLLLC, which require additional high bandwidth voltage sensors or current sensors, the method proposed in this paper is realized by only one low-cost output voltage sensor. And the proposed method is suitable for high-power applications with a wide voltage and load variation. Moreover, because of the symmetrical topology, this method is valid in bidirectional power transfer. Additionally, the exist analog synchronous rectification control chips suffer from losing accuracy with wide bus voltage variation, however, this method can overcome this shortcoming. Thus, the proposed synchronous rectification method is a low-cost and suitable for high-power, high power density, high efficiency application which benefit from its simple algorithm. Finally, the proposed sensor-less synchronous rectification method is validated by the simulation results and experimental results. The results of simulation and experimental have shown the proposed method offers significant benefits which increases the efficiency of the whole CLLLC system by about 3%, and the reliability of the converter are greatly increased, due to the cooler SRs.

The novel procedure of active thermal ndt: combining heating and forced cooling

A novel technique of active thermal nondestructive testing is proposed. It involves consecutive heating and forced cooling of the surface of test objects. The results of numerical modeling and experiments have demonstrated efficiency of this technique in case of test materials, which are characterized by a high level of emission/absorption noise. Optimization of such test procedure requires correctly choosing power and turn-on time of forced cooling to stimulate increase of temperature contrast over defects at particular times. An additional advantage of forced cooling is decrease of a thermal load on test materials that may be important in case of composites.

Capacitance Variations and Gate Voltage Hysteresis Effects on the Turn-ON Switching Transients Modeling of High-Voltage SiC MOSFETs

This paper presents a discrete and real-time capable dynamic behavioural model of the turn-on switching transition of high-voltage and high-current Silicon Carbide (SiC) metal-oxide-semiconductor field-effect transistor (MOSFET) half-bridge power modules. The dynamic switching model utilizes the Shichman and Hodges equations using voltage-dependent non-linear device capacitances and module electrical parameters to obtain an accurate dynamic model of the device switching transients. The key device states gate-source voltage, drain current and drain-source voltage are modelled. The paper investigates the impact of correct device capacitance modelling with low off-state gate-source voltage values, impacting the device capacitances and causes gate-voltage hysteresis effects. It has been shown that the presented discrete-time dynamic switching model accurately describes the turn-on transient and the results highlight the importance of correct capacitance and threshold voltage characterization data. The modelling results are compared to experimental measurements conducted in a 3.3 kV/750 A SiC MOSFET power module. The model exhibits an average accuracy of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 4\%$</tex-math></inline-formula> for turn-on energy and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\sim 1.3\%$</tex-math></inline-formula> for the turn-on time compared to measurements. These models are valuable for rapid and cost effective design and validation of advanced gate-driver circuits and for determining key design and operating parameters such as deadtime, switching frequency and switching losses.

Способ сокращения времени подачи резервного питания в системах электроснабжения с двигательной нагрузкой

Nowadays fast-acting automatic transfer equipment is commonly applied in power supply systems with a motor load since it ensures uninterrupted power supply of critical consumers. However, their application requires the use of high-speed breakers. The implementation of a “high-speed” transfer to a backup power source when using vacuum switches may not be possible due to the long turn-on and turn-off times. Therefore, the purpose of the paper is relevant. The aim of the paper is to study the possibility to reduce the backup power supply time by improving the algorithm to control the vacuum switches of the main and backup power sources in the modes “high-speed” switching by the fast-acting automatic device in case of short circuits in the external power supply network. To achieve this purpose, computer modeling methods are used. They are based on mathematical models of electrical network elements written using systems of differential equations. The authors have defined the regularities of the transient processes in synchronous and induction motors when switching to a backup power source by the fast-acting automatic device in case of short circuits in the external power supply network. It makes possible to set the limit value of the mismatch angle between the residual voltage vectors on the section of the main power source and the voltage of the backup power source, at which the level of the self-starting current does not exceed the values of the starting currents. Also, it makes possible to develop an algorithm to control breakers. The proposed algorithm is based on changing the operation order of the switches of the main and backup power sources. The obtained results show that implementation of the proposed algorithm to control breakers of the main and backup power sources in fast-acting automatic devices in case of short circuits in the external power supply network of the main power source makes it possible to reduce the backup power supply time and decrease the level of self-starting currents that do not exceed the level of starting currents of electric motors without use of high-speed switches.