Gate Trigger Research Articles

Oxide-based synaptic transistors gated by solution-processed gelatin electrolytes

In human brain, a large number of neurons are connected via synapses. Simulation of the synaptic behaviors using electronic devices is the most important step for neuromorphic systems. In this paper, proton conducting gelatin electrolyte-gated oxide field-effect transistors (FETs) were used for emulating synaptic functions, in which the gate electrode is regarded as pre-synaptic neuron and the channel layer as the post-synaptic neuron. In analogy to the biological synapse, a potential spike can be applied at the gate electrode and trigger ionic motion in the gelatin electrolyte, which in turn generates excitatory post-synaptic current (EPSC) in the channel layer. Basic synaptic behaviors including spike time-dependent EPSC, paired-pulse facilitation (PPF), self-adaptation, and frequency-dependent synaptic transmission were successfully mimicked. Such ionic/electronic hybrid devices are beneficial for synaptic electronics and brain-inspired neuromorphic systems.

돌입전류 제한회로 개선을 통한 전원변환장치 운용신뢰성 향상

본 논문에서는 돌입전류로부터 전원변환장치를 보호하고 오동작을 예방하기 위해서 돌입전류 제한회로의 성능 향상방법에 관해 서술하였다. 군용 레이더의 전원변환장치를 운용하던 도중 회로차단기가 간헐적으로 동작하여 장비운용에 불편함이 초래되었다. 돌입전류 제한회로의 출력 전류를 측정해 본 결과 간헐적으로 250A이상 과전류가 발생하여 회로차단기가 동작하였다. 돌입전류 제한회로에 사용된 SCR(Silicon Controlled Rectifier) 분석, 돌입전류 제한회로의 동작원리 분석을 통해 의도치 않게 dv/dt triggering 방식으로 SCR이 도통되면서 과도한 전류가 발생한다는 것을 알 수 있었다, 분석한 원인을 바탕으로 SCR 양단에 급격한 전압 변화가 생기지 않도록 하고, SCR이 gate triggering 이외의 방식으로 도통 되어도 의도한 전류이상으로 돌입전류가 발생하지 않도록 SCR 앞단에 저항이 위치 하도록 회로를 변경하여 순간적인 전압 변화를 방지하였다. 마지막으로 돌입전류 제한회로의 전류 측정을 통해 의도한 전류 이상으로 돌입전류가 발생하지 않음을 입증 하였고, 상위체계에 부착시험을 통해 체계 영향성을 확인 하였으며, 전원변환장치에 적용하여 1년 이상 야전에서 운용결과 회로차단기가 동작하는 경우가 발생하지 않았다. This paper describes the performance improvement of an inrush current limiter to prevent damage or malfunctions in power converters due to the inrush current. When the power converter of military radar is operated, the circuit breaker of the power converter is often activated because the overcurrent flows through the circuit breaker of the power converter. Therefore, this study performed a cause analysis of the problem, which is a larger current flow than the intended current(250A). The operation principle of an inrush current limiter and SCR (Silicon Controlled Rectifier) used in the inrush current limiter was analyzed. As a result, the overcurrent flow through the circuit breaker was found to be due to dv/dt triggering of SCR. Based on cause analysis, this paper proposes a technique by adding the resistor in front of the SCR to prevent an unnecessary inrush current. Finally, the effectiveness of the improvement was verified by measuring the output current in the inrush current limiter. The power converter equipped with the improved inrush current limiter operated for more than 1 year without the circuit breaker of the power converter being activated.

A Universal Simulation Method to Calculate Power Losses of IGBTs and Anti-Parallel Diodes

In this paper, a universal loss calculation model in simulation is established in MATLAB / Simulink which can be used in not only ideal but also non-ideal conditions ( non-sinusoidal load current and grid voltage, unfixed system parameters such as stator resistance for induction motors, unstable DC voltage with fluctuation, aperiodic modulation strategies with unfixed switching frequency, and so on). Considering the influence of dead time, steady operating states of each device can be obtained by the measurement of the load current and gate triggering pulses of every IGBT in a phase arm which can be easily measured in experiment rather than the currents and voltages of devices. Analyses in two-level topology and Neutral-Point-Clamped (NPC) three-level topology were done as examples. In periodic pulse width modulation with sinusoidal modulation wave, consistency among results from the proposed simulation model, the formula commonly used and commercially available loss software provided by power device manufacturer was shown. Through the design of a two-level inverter in hysteretic control, experimental verification of proposed method was applied. Calculating power loss in this method can be adapted to different converter topologies with various control strategies which is not even for ideal conditions.

Performance Analysis of Savonius Rotor Based Hydropower Generation Scheme with Electronic Load Controller

This paper describes the performance of electronic load controller (ELC) of asynchronous generator (AG) coupled to an uncontrolled Savonius turbine and variable water velocity. An AC-DC-AC converter with a dc link capacitor is employed to maintain the required frequency. The ELC which is feeding a resistive dump load is connected in parallel with the generating system and the power consumption is varied through the duty cycle of the chopper. Gate triggering of ELC is accomplished through sinusoidal pulse width modulation (SPWM) by sensing the load current. A MATLAB/Simulink model of Savonius rotor, asynchronous generator, ELC, and three-phase load is presented. The proposed scheme is tested under various load conditions under varying water velocities and the performances are observed to be satisfactory.

Turn-on of High-Voltage SiC Thyristors for Fast-Switching Applications

This paper is focused on the characterization of the turn-ON transition of high-voltage SiC thyristors of different epi-layer thicknesses and active-area sizes to determine their suitability and limitations in high- $dI/dt$ , fast-switching applications. The unique aspects of this paper include the very high current density being switched through the thyristors over a short period of time at initial turn-ON, resulting in very high instantaneous dissipated power over the small device volume. The devices that were characterized were 6-kV, 0.5-cm2 thyristors; 10-kV, 1.05-cm2 thyristors; and 15-kV, 1.05-cm2 thyristors, all fabricated by Cree, Inc. (now Wolfspeed) for the U.S. Army Research Laboratory. The highest dI/dt and the current density were 13 kA/ms and 3.2 kA/cm2 for a parallel pair of 0.5-cm2 thyristors, with pulsed current peaking 250 ns from initial gate trigger. All devices evaluated were capable of switching a current pulse >2 kA/cm2 within a period of less than $2~\mu \text{s}$ . These evaluations have broad application in helping to inform SiC device design tradeoffs for increasing epi thickness, increasing device area, and the effects of lifetime enhancement processes. Results are also presented for initial exploration of fast-switching applications for these devices.

Investigation of Series-Connected IGBTs in Fast High-Voltage Circuit Breaker

The ECRH system on J-TEXT tokamak requires fast circuit breakers as switches to cut off the 80 kV power supply within 20 μs when failure occurs. Series connected IGBTs is a better choice for the breaker than mechanical switch and thyristor in this case. The voltage balance among IGBTs is the main issue that needs investigation. This paper presents a two-stage active gate trigger time compensation method to ensure the voltage balance among IGBTs. The test environment consists of a 1500 V/10 A circuit with 3 IGBTs which are connected in series. The experimental result shows that the method can effectively improve the dynamic-voltage balance and has a certain extent meaning for the solution of voltage balance of series connected IGBTs .

Minimum gate trigger current degradation in 4.5 kV 4H-SiC commutated gate turn-off thyristor

The increment in minimum gate trigger current in a 4H-SiC commutated gate turn-off thyristor after the current stress test is investigated. The recombination at the intersection line of the Shockley-type stacking faults and the pn junction causes a reduction in the level of carrier injection from the anode to the gate. The current gain of the top pnp bipolar junction transistor, therefore, decreases, and the minimum gate trigger current increases. The minimum gate trigger current after the current stress test does not return to that before the current stress test at 200 °C, although the on-state voltage of the degraded thyristor returns to that of the original one when the temperature is increased to more than 150 °C. The Shockley-type stacking faults, which are parallel to the current flow from the anode to the gate and cause the increment in minimum gate trigger current, exist even if the temperature increases.

A New Thyristor Triggering Scheme for Intermittent Pulse Rectifiers for a Large-Capacity Pulsed Power Supply

Technical details about intermittent pulse rectifiers for large-capacity pulsed power supply have rarely been reported in the literature. In this paper, a new thyristor triggering scheme for this application is proposed. This proposed scheme adjusts gate trigger pulses according to the real-time variation of thyristor anode-to-cathode voltage to optimize the triggering performance. Accurate triggering is possible under big line voltage distortions and large frequency changes. Integrated real-time diagnostics can provide valuable information regarding thyristor triggering. The scheme can also prohibit unnecessary trigger pulses to reduce the gate power dissipation. Thus, gate trigger pulses can be designed with high amplitude to enhance the thyristor turn-on characteristics. The validity and superiority of the proposed scheme is verified through experiments. In actual operation, the scheme performs satisfactorily even under sudden load changes.

Towards a compensatable Muon Collider calorimeter with manageable backgrounds

Muon Collider detectors pose very challenging problems in detectortechnology due to extremely large backgrounds present in the detectorvolume as a result of muon decays. Current designs of a 750 GeV/c perbeam Muon Collider envisage 4.28 × 105 muon decays per meter in the beam pipeclose to the interaction region. The decay electrons after intenseshielding still manage to produce large backgrounds in the detectorvolume of low energy photons, neutrons and higher energy Bethe Heitlermuons. There are 170/184/6.8/177 TeVs energy entering the detector volume per crossingdue to EM particles/Muons/Mesons/Baryons respectively. Weinvestigate the capabilities of an iron calorimeter with pixelatedreadout where each pixel gives a yes/no answer as to whether a chargedparticle passed through it or not, to solve this problem. Each pixel is individuallytriggered by a ``travelling gate trigger'' with a gate of 2 ns wherethe beginning of the gate is the time of arrival of a light signalfrom the interaction region to the pixel. We show that such acalorimeter is compensatable and propose two schemes to compensate thedigital output in software to improve the resolution of thecalorimeter. We show that such a calorimeter is capable of digitizingphysics signals from the interaction region and as a result,the backgrounds fromthe muon decays are much reduced and under control.

A driver for gate commutated thyristors

A driver for a gate communicated thyristor is developed that provides for pulses of gate trigger current of amplitude 200 A, sustains gate current of 10 A, and forms gate turn-off current pulses of amplitude up to 5500 A with a rise time less than 1 μs.

Structural basis for the coupling between activation and inactivation gates in K+ channels

The coupled interplay between activation and inactivation gating is a functional hallmark of K(+) channels. This coupling has been experimentally demonstrated through ion interaction effects and cysteine accessibility, and is associated with a well defined boundary of energetically coupled residues. The structure of the K(+) channel KcsA in its fully open conformation, in addition to four other partial channel openings, richly illustrates the structural basis of activation-inactivation gating. Here, we identify the mechanistic principles by which movements on the inner bundle gate trigger conformational changes at the selectivity filter, leading to the non-conductive C-type inactivated state. Analysis of a series of KcsA open structures suggests that, as a consequence of the hinge-bending and rotation of the TM2 helix, the aromatic ring of Phe 103 tilts towards residues Thr 74 and Thr 75 in the pore-helix and towards Ile 100 in the neighbouring subunit. This allows the network of hydrogen bonds among residues Trp 67, Glu 71 and Asp 80 to destabilize the selectivity filter, allowing entry to its non-conductive conformation. Mutations at position 103 have a size-dependent effect on gating kinetics: small side-chain substitutions F103A and F103C severely impair inactivation kinetics, whereas larger side chains such as F103W have more subtle effects. This suggests that the allosteric coupling between the inner helical bundle and the selectivity filter might rely on straightforward mechanical deformation propagated through a network of steric contacts. Average interactions calculated from molecular dynamics simulations show favourable open-state interaction-energies between Phe 103 and the surrounding residues. We probed similar interactions in the Shaker K(+) channel where inactivation was impaired in the mutant I470A. We propose that side-chain rearrangements at position 103 mechanically couple activation and inactivation in KcsA and a variety of other K(+) channels.

In vivo gated 4D imaging of the embryonic heart using optical coherence tomography

We demonstrate the first in vivo gated 4D images of avian embryonic hearts by use of optical coherence tomography (OCT). We present a gated 4D dataset of an in vivo beating quail heart consisting of approximately 864,000 A-scans accumulated over multiple heartbeats. Generation of a gating trigger from a laser Doppler velocimetry (LDV) signal, collected from an outlying vitelline vessel, enabled us to gate image acquisition to the cardiac cycle. To fully characterize the genesis and mechanisms of cardiac defects, a tool capable of assessing structure and function simultaneously at early stages of development is needed, and gated OCT has the capability to become such a tool.

Novel gate and substrate triggering techniques for deep sub-micron ESD protection devices

As technology feature size is reduced, ESD becomes the dominant failure mode due to lower gate oxide breakdown voltage. In this paper, the effectiveness of new gate and substrate triggering techniques has been investigated to lower the trigger voltage of the LVTSCR and MOSFET based ESD protection circuits using 2D simulations and HBM/TLP measurements. The simulation results show that the using these techniques reduces the ESD triggering voltage by 63 and 44% for MOSFET-based and LVTSCR-based ESD structures, respectively, under 2kV HBM ESD stress. The effectiveness of proposed gate and substrate triggering techniques is also confirmed by the HBM and TLP measurements.

Prodrug Activation Gated by a Molecular “OR” Logic Trigger

Molecules that define logic: A molecular “OR” logic gate trigger has been demonstrated by masking a functional group in a doxorubicin prodrug with a linker that contains two cleavable substrates (input). The prodrug molecule was activated by two different enzymes to release the parent drug (see scheme; input red; output (drug) blue). Supporting information for this article is available on the WWW under http://www.wiley-vch.de/contents/jc_2002/2005/z500842_s.pdf or from the author. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

A simple respiration gating technique and its application in high-resolution PET camera

We have developed a simple technique to gate positron emission tomography (PET) imaging in synchronization with respiratory motion to reduce image blurring caused by breathing and improve quantification of tracer uptake in lesions in the chest and abdomen, especially in very high-resolution PET systems. Taking advantage of the temperature differences in the air flow in a nostril due to inhalations and exhalations, a simple solid thermometer was used to construct a respiratory gating system to monitor the respiratory cycles. The gating system provided trigger signals synchronous with respiration and 40 Hz timing marks. These trigger signals and timing marks were inserted into the data stream in real-time while the PET camera was taking data. The gating trigger signals represent a particular phase of respiratory motion, and the evenly cycled timing marks were designed for motion-image frame registration. This gating system was implemented and tested with our MDAPET, a very high-resolution (2.7-mm resolution) PET camera developed at The University of Texas M. D. Anderson Cancer Center. A volunteer with 2 spherical lesion phantoms (diameters 3 mm and 5 mm) placed on the abdomen close to the navel was scanned in the gated mode. The respiration-gated images of the lesion phantoms were compared and studied. The simple respiratory gating system worked well in terms of detecting the breathing cycle and providing gating trigger signals and timing marks. Image blur and errors in the measurements of the lesions' volumes in the gated PET images were reduced, compared with those of the non-gated PET images.

Energy measurement of relativistic electron beams by laser Compton scattering.

Laser Compton scattering by relativistic electrons provides the energy information associated with electron beams in an accelerator. Determining the electron beam energy by this method depends primarily on the signal to noise (S/N) ratio associated with laser Compton scattering. In this study, we propose a method to enhance the S/N ratio by synchronous measurement with a high peak power pulsed ${\mathrm{CO}}_{2}$ laser. In this method, the pulsed ${\mathrm{CO}}_{2}$ laser provides the gate trigger signals, and the delay times of the triggers are optimized to obtain a maximum S/N ratio. In the storage ring of Taiwan Light Source, a \ensuremath{\gamma} ray with the highest energy of 3.021 MeV was backscattered after the 0.1172 eV ${\mathrm{CO}}_{2}$ laser photons colliding with the relativistic electrons. The S/N ratio is about 42.5 with the electron beam current being 19 mA. Also, the measured electron beam energy is 1.3058 GeV with relative uncertainty 0.13%. \textcopyright{} 1996 The American Physical Society.

A high-current and high-temperature 6H-SiC thyristor

A 6H-SiC thyristor has been fabricated and characterized. A forward breakover voltage close to 100 V and a pulse switched current density of 5200 A/cm/sup 2/ have been demonstrated. The thyristor is shown to operate under pulse gate triggering for turn-on and turn-off, with a rise time of 43 ns and a fall time of less than 100 ns. The forward breakover voltage is found to decrease by only 4% when the operating temperature is increased from room temperature to 300/spl deg/C. It is found that anode ohmic contact resistance dominates the device forward drop at high current densities.

A fine pattern GTO thyristor fabricated using a self-aligned process

GTO thyristors with a 2 cm2 active area and small rectangular 40 * 40 μm emitters were fabricated using a specially developed self-aligned process based entirely on reactive ion etching, RIE, technology. Each device consists of 176 1 mm2 segments containing 100 individual emitters. The devices were electrically evaluated and compared to standard, wet etched mesa, GTO devices of comparable size having 3000 * 200 μm large emitters. Simulations were carried out to analyse specific features of the new devices. In particular the influence of the surface quality on the gate trigger current and on-state voltage was investigated. It was demonstrated that it is possible to reduce significantly the GTO unit cell dimensions without sacrificing the yield. 23% of the cm2 devices out of a lot containing 50 devices could be accepted without repair while the overall segment yield was 97%. The dynamic performance of the devices under both snubbered and snubberless conditions compares well to that of the reference devices.

Characteristics of Zero Current Switching High Frequency Inverter with Constant Frequency Power Control.

A constant frequency power control (CFPC) by phase difference regulation of the gate triggering pulse in the half bridge high frequency inverter (HF-INV) is proposed in this paper. The principle of zero current switching (ZCS) operation utilized an overlapping commutation mode in the HF-INV is numerically analyzed in associated with normalized frequency and load.The results obtained through the analysis are supplemented with experimental results. Furthermore the design criteria on the basis of numerical analysis are investigated.

High-frequency 6000 V double-gate GTO's

A double-gate gate turn off (GTO) thyristor, which has an additional gate on the n-base layer, has been proposed to realize high-frequency operation for high-power inverters. The double-gate structure has further been combined with an n-buffer structure to realize narrow n-base width. A forward-blocking voltage of 6000 V was obtained, even at 150 degrees C, when the second gate was shorted to the anode electrode. In order to reduce turn-on and turn-off switching losses, the dependence of these losses on a time interval between two gate triggering pulses has been investigated. It was found that the turn-off loss of approximately 1/20th of that for a conventional GTO thyristor was achieved by adjusting the time interval between the two gate triggering pulses. >