Turn-on Time Research Articles

Wakeup scheduling and its buffered tree synthesis for power gating circuits

Power gating circuit suffers from large amount of rush current during wakeup, especially when all switch cells are turned on simultaneously. If each switch cell is turned on at a different time, rush current can be reduced. It is shown in this paper that rush current can be reduced even more if signal transition time (or signal slew) to each switch cell is adjusted. We define wakeup scheduling as to determine turn-on time and signal slew of each switch cell; the goal is to minimize wakeup delay while keeping rush current below the maximum value that is allowed. The determined turn-on time and signal slew are implemented using a buffered tree. The wakeup scheduling and buffered tree construction are integrated into a design flow. To adapt to process variation, we use adjustable delay buffers in the wakeup network. We also apply grid-based design flow and use Schmitt triggers to implement large designs. Experiments in an industrial 1.1V, 32-nm technology demonstrate that the wakeup delay is reduced by 12% on average of example circuits compared with turn-on scheduling.

Peripheral halo-functionalization in [Cu(N^N)(P^P)]+ emitters: influence on the performances of light-emitting electrochemical cells.

A series of heteroleptic [Cu(N^N)(P^P)][PF6] complexes is described in which P^P = bis(2-(diphenylphosphino)phenyl)ether (POP) or 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (xantphos) and N^N = 4,4'-diphenyl-6,6'-dimethyl-2,2'-bipyridine substituted in the 4-position of the phenyl groups with atom X (N^N = 1 has X = F, 2 has X = Cl, 3 has X = Br, 4 has X = I; the benchmark N^N ligand with X = H is 5). These complexes have been characterized by multinuclear NMR spectroscopy, mass spectrometry, elemental analyses and cyclic voltammetry; representative single crystal structures are also reported. The solution absorption spectra are characterized by high energy bands (arising from ligand-centred transitions) which are red-shifted on going from X = H to X = I, and a broad metal-to-ligand charge transfer band with λmax in the range 387-395 nm. The ten complexes are yellow emitters in solution and yellow or yellow-orange emitters in the solid-state. For a given N^N ligand, the solution photoluminescence (PL) spectra show no significant change on going from [Cu(N^N)(POP)]+ to [Cu(N^N)(xantphos)]+; introducing the iodo-functionality into the N^N domain leads to a red-shift in λ compared to the complexes with the benchmark N^N ligand 5. In the solid state, [Cu(1)(POP)][PF6] and [Cu(1)(xantphos)][PF6] (fluoro-substituent) exhibit the highest PL quantum yields (74 and 25%, respectively) with values of τ1/2 = 11.1 and 5.8 μs, respectively. Light-emitting electrochemical cells (LECs) with [Cu(N^N)(P^P)][PF6] complexes in the emissive layer have been tested. Using a block-wave pulsed current driving mode, the best performing device employed [Cu(1)(xantphos)]+ and this showed a maximum luminance (Lummax) of 129 cd m-2 and a device lifetime (t1/2) of 54 h; however, the turn-on time (time to reach Lummax) was 4.1 h. Trends in performance data reveal that the introduction of fluoro-groups is beneficial, but that the incorporation of heavier halo-substituents leads to poor devices, probably due to a detrimental effect on charge transport; LECs with the iodo-functionalized N^N ligand 4 failed to show any electroluminescence after 50 h.

Realistic vs sudden turn-on of natural incoherent light: Coherences and dynamics in molecular excitation and internal conversion.

Molecular excitation with incoherent light is examined using realistic turn-on time scales, and results are compared to those obtained via commonly used sudden turn-on, or pulses. Two significant results are obtained. First, in contrast to prior studies involving sudden turn-on, realistic turn-on is shown to lead to stationary coherences for natural turn-on time scales. Second, the time to reach the final stationary mixed state, known to result from incoherent excitation, is shown to depend directly on the inverse of the molecular energy level spacings, in both sudden and realistic turn-on cases. The S0 → S2/S1 internal conversion process in pyrazine is used as an example throughout. Implications for studies of natural light harvesting systems are noted.

A liquid crystal cell with double-side protrusion electrodes for fast response and low-voltage operation

ABSTRACTWe propose a homogeneously aligned liquid crystal (LC) cell with double-side protrusion electrodes for fast response and low-voltage operation. In the proposed device, both the bottom and top substrates have pixel electrodes to generate the fringe electric field. Because the penetration depth of the electric field is increased owing to the protrusion electrodes, the operating voltage is very low and the turn-on time is dramatically reduced compared with the conventional in-plane switching (IPS) mode. Moreover, LC molecules anchored strongly to the penetrated protrusion electrodes on both substrates exert a strong restoring force, resulting in a fast turn-off time. We found that the total response time of the LC cell with the proposed structure is three times faster than that of the conventional IPS mode.

High-Efficiency Polymer LEDs with Fast Response Times Fabricated via Selection of Electron-Injecting Conjugated Polyelectrolyte Backbone Structure.

Imidazolium ionic side-group-containing fluorene-based conjugated polyelectrolytes (CPEs) with different π-conjugated structures, poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] dibromide (F8im-Br) and poly[(9,9-bis(8'-(3″-methyl-1″-imidazolium)octyl)-2,7-fluorene)-alt-(benzo(2,1,3)thiadiazol-4,8-diyl) dibromide (F8imBT-Br), are synthesized and utilized as an electron injection layer (EIL) in green-emitting F8BT polymer light-emitting diodes (PLEDs). Both CPE EIL devices significantly outperform Ca cathode devices; 17.9 cd A(-1) (at 3.8 V) and 16.6 lm W(-1) (at 3.0 V) for F8imBT-Br devices, 11.1 cd A(-1) (at 4.2 V) and 9.1 lm W(-1) (at 3.4 V) for F8im-Br devices, and 7.2 cd A(-1) (at 3.6 V) and 7.0 lm W(-1) (at 3.0 V) for Ca devices. Importantly, unlike the F8im-Br EIL devices, F8imBT-Br PLEDs exhibit much faster electroluminescence turn-on times (<10 μs) despite both EILs possessing the same tethered imidazolium and mobile bromide ions. The F8imBT-Br devices represent, to the best of our knowledge, the highest efficiency in thin (70 nm) single-layer F8BT PLEDs in conventional device architecture with the fastest EL response time using CPE EIL with mobile ions. Our results clearly indicate the importance of an additional factor of EIL materials, specifically the conjugated backbone structure, to determine the device efficiency and response times.

Pulsed Excitation Dynamics of an Optomechanical Crystal Resonator near Its Quantum Ground State of Motion

Using pulsed optical excitation and read-out along with single-phonon-counting techniques, we measure the transient backaction, heating, and damping dynamics of a nanoscale silicon optomechanical crystal cavity mounted in a dilution refrigerator at a base temperature of Tf≈11 mK. In addition to observing a slow (approximately 740-ns) turn-on time for the optical-absorption-induced hot-phonon bath, we measure for the 5.6-GHz “breathing” acoustic mode of the cavity an initial phonon occupancy as low as ⟨n⟩=0.021±0.007 (mode temperature Tmin≈70 mK) and an intrinsic mechanical decay rate of γ0=328±14 Hz (Qm≈1.7×107). These measurements demonstrate the feasibility of using short pulsed measurements for a variety of quantum optomechanical applications despite the presence of steady-state optical heating.Received 6 April 2015DOI:https://doi.org/10.1103/PhysRevX.5.041002This article is available under the terms of the Creative Commons Attribution 3.0 License. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI.Published by the American Physical Society

Voltage regulation of a matrix converter with balanced and unbalanced three-phase loads

This paper addresses the design, simulation and experimental validation of a voltage control for a three-phase to three-phase Matrix Converterworking under balanced and unbalanced resistive loads. The converter is based on bidirectional switches and space vector pulse width modulationis used to control their turn-on and turn-off times. Tracking and repetitive controls are designed and implemented; having this last one a majorimpact on the performance of the output voltage regulation for balanced or unbalanced loads. The experimental control setup is comprised of afield programmable gate array board, a digital signal processor and a graphics interface board.All Rights Reserved © 2015 Universidad Nacional Autonoma de Mexico, Centro de Ciencias Aplicadas y Desarrollo Tecnologico. This is anopen access item distributed under the Creative Commons CC License BY-NC-ND 4.0.

Time‐sharing PWM control scheme for isolated multi‐output DC–DC converter

A novel multi-output pulse-width-modulated control scheme based on time sharing is presented and applied to a two-output forward converter. Unlike the traditional two outputs, the main voltage output and the auxiliary voltage output can be controlled independently via two different switching periods and controllers, by inserting one auxiliary switch into the circuit. Put simply, the main turn-on time is used to control the main switch, the auxiliary turn-on time is used to control the auxiliary switch, and there are several auxiliary turn-on times within one main turn-on time. By this means, two stabilised output voltages are obtained with good cross-regulation. The prototype is verified by a 24 V input, the main voltage output, which has a rated output voltage of 56 V and a rated output power of 50 W, and the auxiliary output, which has a rated output voltage of 44 V and a rated output power of 40 W.

MULTI-WAVELENGTH LIGHT CURVE MODEL OF THE ONE YEAR RECURRENCE PERIOD NOVA M31N 2008-12a

We present a theoretical light curve model of the recurrent nova M31N 2008-12a, the current record holder for the shortest recurrence period (1 yr). We combined interior structures calculated using a Henyey-type evolution code with optically thick wind solutions of hydrogen-rich envelopes, which give the proper mass-loss rates, photospheric temperatures, and luminosities. The light curve model is calculated for a 1.38 M_sun white dwarf (WD) with an accretion rate of 1.6 \times 10^{-7} M_sun yr^{-1}. This model shows a very high effective temperature (log T_ph (K) \geq 4.97) and a very small wind mass-loss rate (\dot M_wind \leq 9.3 \times 10^{-6} M_sun yr^{-1}) even at the maximum expansion of the photosphere. These properties are consistent with the faint optical peak of M31N 2008-12a because the brightness of the free-free emission is proportional to the square of the mass-loss rate. The model well reproduces the short supersoft X-ray turn-on time of 6 days and turnoff time of 18 days after the outburst. The ejecta mass of our model is calculated to be 6.3 \times 10^{-8} M_sun, corresponding to 37% of the accreted mass. The growth rate of the WD is 0.63 times the mass accretion rate, making it a progenitor for a Type Ia supernova. Our light curve model predicts a bright supersoft X-ray phase one or two days before the optical peak. We encourage detection of this X-ray flash in future outbursts.

Optical Response Features of LC Cells Doped with CdSe/ZnS Quantum Dots

We investigated the optical response times of the LC cells with a nematic liquid crystal with positive dielectric anisotropy doped with 3.5 nm semiconductor quantum dots CdSe/ZnS. We observed that the optical response times of LC cells doped with 1 and 2 mg/ml QDs decreased significantly after one month in comparison with initial. The turn-on time at a wavelength of 1.55 μm of the twist cell with a thickness of 8 μm, filled with the suspension of the LC and 1 mg/ml QDs was about 200 μs. It is shown that using a unipolar square wave voltage decreasing response time of the liquid crystal cell.

ChemInform Abstract: Improving the Carrier Balance of Light‐Emitting Electrochemical Cells Based on Ionic Transition Metal Complexes

AbstractReview: 82 refs.

The Research of Turn-On Time for Silicon Micromechanical Gyroscope on a Chip

On the basis of analyzing the boot process of silicon micromechanical gyroscope on a chip at room temperature, -40 °C and 60 °C constant temperature environment, for the character that the gyroscope can realize the compensation function and possess temperature-sensitive output model, This paper analyzes the relationship between the bias and temperature meter, and presents compensation method of the initial bias so as to reduce different turn-on time caused by the variation with the temperature of working environment. Experimental results demonstrate the method can effectively reduce turn-on time at the variation with temperature of working environment.

Enhanced ESD power clamp for antenna switch controller with SOI CMOS technology

An enhanced electrostatic discharge (ESD) power clamp for an antenna switch controller with silicon-on-insulator (SOI) complementary metal-oxide-semiconductor (CMOS) technology is presented. The gate drive voltages of larger n-type metal-oxide-semiconductor transistors in a stacked configuration of a RC-triggered power clamp have been optimised to obtain larger discharging capability and shorter turn-on time compared to the conventional topology. The proposed ESD power clamp circuits are implemented in a double-pole five-throw antenna switch controller and the experimental results confirm the validity of this approach.

LED Driver with TRIAC Dimming Control by Variable Switched Capacitance for Power Regulation

A TRIAC dimming LED driver that can control the brightness of LED arrays for a wide range of source voltage variations is proposed in this paper. Unlike conventional PWM LED drivers, the proposed LED driver adopts a TRIAC switch, which inherently guarantees zero current switching and has been proven to be quite reliable over its long lifetime. Unlike previous TRIAC type LED drivers, the proposed LED driver is composed of an LC input filter and a variable switched capacitance, which is modulated by the TRIAC turn-on timing. Thus, the LED power regulation and dimming control, which are done by a volume resistor in the same way as the conventional TRIAC dimmers, can be simultaneously performed by the TRIAC control circuit. Because the proposed LED driver has high efficiency and a long lifetime with a high power factor (PF) and low total harmonic distortion (THD) characteristics, it is quite adequate for industrial lighting applications such as streets, factories, parking garages, and emergency stairs. A simple step-down capacitive power supply circuit composed of passive components only is also proposed, which is quite useful for providing DC power from an AC source without a bulky and heavy transformer. A prototype 60 W LED driver was implemented by the proposed design procedure and verified by simulation and experimental results, where the efficiency, PF, and THD are 92%, 0.94, and 6.3%, respectively. The LED power variation is well mitigated to below <TEX>${\pm}2%$</TEX> for 190 V < <TEX>$V_s$</TEX> < 250 V by using the proposed simple control circuit.

The electro-optics of nematic liquid crystals stabilized by physical networks

A new composite material based on the 5CB nematic stabilized by a physical network formed by 12-hydroxyoctadecane acid has been prepared. The electro-optical properties of the material—the dependence of the transmittance and the turn-on and turn-off times on the voltage—have been studied. Two turn-on and turn-off times have been found. It has been found that the gelling agent (acid) strongly violates the orientation of the liquid crystal to form two systems of its regions. One has a planar orientation; the other, an inclined orientation. The effective sizes of these regions are different and significantly smaller than the thickness of the cell.

Method to Minimize the Low-Frequency Neutral-Point Voltage Oscillations With Time-Offset Injection for Neutral-Point-Clamped Inverters

This paper proposes a method to reduce the low-frequency neutral-point voltage oscillations. The neutral-point voltage oscillations are considerably reduced by adding a time offset to the three-phase turn-on times. The proper time offset is simply calculated considering the phase currents and dwell time of small- and medium-voltage vectors. However, if the power factor is lower, there is a limitation to eliminate neutral-point oscillations. In this case, the proposed method can be improved by changing the switching sequence properly. Additionally, a method for neutral-point voltage balancing is also proposed. The change in switching frequency by the proposed method and its effects on the outputs are negligible. Simulation and experimental results verify the validity and feasibility of the proposed strategy.

Orbitron-type vacuum gauge with nanocarbon field cathode

A novel electron–optical scheme of ionization-type vacuum gauge is proposed that allows the use of field-emission nanocarbon cathodes. The developed gauge satisfies the requirements imposed by possible utilization in on-board satellite equipment: low mass, size and energy consumption, low turn-on time, etc. High efficiency and sensitivity of the sensor are achieved by the use of an electrostatic trap for accumulation of electrons ionizing the gas molecules. Magnetic field was not used for mass economy reason and to avoid possible influence onto other on-board equipment. The main problem solved in the work originated from the intrinsic contradiction between the aims of achieving long-term confinement of electrons in the trap and focusing of the applied electric field at the cathode, the latter being necessary to utilize the phenomenon of field-induced emission. Experimental tests were performed with two prototype devices realizing different versions the electron-scheme design, viability of both developed schemes has been confirmed.

A High-Sensitivity Radar System Featuring Low Weight and Power Consumption

In this article, a lightweight, low-power radar system for vibration monitoring has been presented. Based on a theoretical analysis of the competition scenario, an optimized system concept has been developed. The radar front end is able to sequentially evaluate the in-phase and quadrature component of the received signal with only a single hybrid coupler and power detector, reducing the overall weight to 5 g including the power-supply cable. A low duty cycle of 1% allowed the power to average 1.5 mW. As the minimum required sensitivity was limited to 0.5-mm oscillation amplitude, the most challenging parts in this student competition were, in our opinion, the tight power and weight optimizations. As the competition required only vibration detection butno ranging, a minimalistic system concept optimized for this application was proposed. The system features a free-running VCO sourced directly from the power supply without any further stabilization. For ranging applications, temperature changes as well as supply and tuning voltage variations at the VCO could have a severe impact on the system's accuracy. However, for pure vibration detection of a well-defined target, this is not a problem. Further improvements could be achieved when designing a customized 24-GHz oscillator, optimized for high efficiency [9] and fast turn-on time. In addition, the necessary number of measurements per second could be further investigated. Currently, with ten measurements per second, there is a convenient safety margin against false detections; however, fewer measurements would directly reduce the duty cycle and thus the average power consumption of the system.

Indirect Matrix Converters' Enhanced Commutation Method

This paper introduces an enhanced commutation method applied to the indirect matrix converter topology. It is based on the detection of the load current polarity so as to cancel the turn-on delay times of the load-side converter's switches. The proposed method allows the grid-side converter devices to commutate at zero current with larger time interval widths provided for this safe commutation. Moreover, it has been shown through experimental results, carried out on a laboratory prototype of the matrix converter, that a substantial improvement of line current total harmonic distortion is achieved.

Simulation and Analysis of Static and Dynamic Performance of Normally-off TIVJFET Using Sentaurus TCAD

2D numerical simulation of normally-off 4H-SiC Trenched and Implanted VJFET is performed using Sentaurus TCAD simulator. Transport equations and different physical models are employed for exploring the device characteristics. Dynamic and static characteristics are simulated under various channel widths (0.81-0.93μm, step 0.03μm). At a channel width of 0.93μm, forward drain current of 5.77 A is observed which corresponds to specific on-state resistance of 0.328 mΩ.cm2. The device is capable of blocking voltage up to 850V with leakage current of the order of 10-7 A. The switching times and energy losses are extracted from switching waveforms. The turn-on and turn-off times of 3 and 9ns are recorded at RT. Furthermore, the turn-on energy of 1.8μJ and turn-off energy of 5.4μJ are also calculated at RT.