Turn-on Delay Research Articles

Real-Time Device-Level Simulation of MMC-Based MVDC Traction Power System on MPSoC

Real-time simulation of device-level power electronic converter models plays an essential role in traction power systems by allowing accurate prediction of device stresses to design improved control and protection schemes. This paper proposes the electrothermal behavioral power electronic models for the modular multilevel converter (MMC)-based medium voltage direct current (MVDC) traction power system based on the Wiener–Hammerstein configuration. The new configuration introduces the carrier charge prerequisite dynamic transients before device turn-ON or turn-OFF operation. The equivalent carrier charge circuit is also proposed, and the first-order delay assumption of turn-ON and turn-OFF delay time has been proven by the device datasheet. The power electronic device models are implemented in a Xilinx® Zynq® multiprocessing system-on-chip platform. By utilizing hardware and software codesign, both 25- $\mu \text{s}$ time-step system-level and 100-ns time-step device-level transients can be captured in real time within a single device. The three-phase unbalance issue has been resolved by introducing the three-phase to single-phase MMC topology. In the case study, the MMC-based MVDC traction power system has been utilized for the performance of the proposed electrothermal behavioral power electronic models by the off-line simulation models on SaberRD® for device-level transients and PSCAD/EMTDC® for system-level transients.

The effect of external cavity reflectivity on the dynamic behaviors of quantum cascade laser

The effect of external reflectivity on the dynamic behaviors of quantum cascade laser coupled to external cavity is theoretically investigated. Our model is based on three-level rate equations including the dependence of the loss on external cavity parameters. We find in particular that the effective reflectivity, photon lifetime and threshold current are strongly influenced by the external cavity length and external reflectivity. The optimum external cavity length (Lext) is about 4 cm. We also show that the external cavity reflectivity influences significantly the dynamics of the electron number in the upper and lower laser levels, population inversion, and photon numbers in the Fabry Perot and in the external cavities. In addition, the external cavity reflectivity dependences of turn-on delay time (tth) is also studied and discussed.

A Novel Constant-Frequency Quasi-Resonant Converter

In this paper, a new constant-frequency LL switch-capacitor (LLSC) quasi-resonant converter is proposed. Compared with the traditional frequency voltage regulation instruments, the proposed converter can effectively reduce the volume of magnetic components. A switch-control capacitor is used in the LLSC converter and adjusts the capacitor parallel anti-series MOSFET turn-ON delay to change the equivalent capacitance. At constant frequency, the output voltage is adjusted by impedance adjustment. The LLSC converter can achieve the primary side MOSFET zero-voltage switching. A new design procedure is proposed for the LLSC converter. The proposed converter is experimentally by experimental results using 80–120 V and 250-W output prototype.

Approximate analytical expressions for pulse modulation response of quantum cascade lasers

Approximate analytical expressions for turn-on delay, rise time and fall time for pulse modulation of the drive current of quantum cascade lasers are presented. These time expressions are obtained using piece-wise analysis of rate equations. From the analytical expressions, the effects of laser parameters and off and on currents are discussed. A numerical analysis shows reasonable agreement with analytical results. It also confirms the predictions from analytical results. The pulse response is compared with that of near-infrared interband lasers.

Impact of Dot Size on Dynamical Characteristics of InAs/GaAs Quantum Dot Lasers

The purpose of this research is to study laser dynamics of InAs/GaAs Quantum Dot Lasers (QDLs) by changing QD energy levels. To date, most of the investigations have focused on only one of these circumstances, and hardly the result of change in the energy levels can be seen in lasing. In this work, in the first step, energy levels of lens-shape QDs are investigated by the eight-band k.p method, their variation for different QD sizes are surveyed, and recombination energies of the discrete levels are determined. Then, by representing a three-level InAs/GaAs QD laser, dynamics of such a laser device is numerically studied by rate equations in which homogeneous and inhomogeneous broadenings are taken into account. The lasing process for both Ground State (GS) and Excited States (ES) was found to be much sensitive to the QD size. It was observed that in larger QDs, photon number and bandwidth of the small signal modulation decrease but turn-on delay, maximum output power, and threshold current of gain increase. It was also found that for a good modulation, smaller QDs, and form the point of view of high-power applications, larger QDs seem better.

Injection modulation of p+–n emitter junction in 4H–SiC light triggered thyristor by double-deck thin n-base**Project supported by the National Natural Science Foundation of China (Grant No. 51677149)

To overcome hole-injection limitation of p+–n emitter junction in 4H–SiC light triggered thyristor, a novel high-voltage 4H–SiC light triggered thyristor with double-deck thin n-base structure is proposed and demonstrated by two-dimensional numerical simulations. In this new structure, the conventional thin n-base is split to double-deck. The hole-injection of p+–n emitter junction is modulated by modulating the doping concentration and thickness of upper-deck thin n-base. With double-deck thin n-base, the current gain coefficient of the top pnp transistor in 4H–SiC light triggered thyristor is enhanced. As a result, the triggering light intensity and the turn-on delay time of 4H–SiC light triggered thyristor are both reduced. The simulation results show that the proposed 10-kV 4H–SiC light triggered thyristor is able to be triggered on by 500-mW/cm2 ultraviolet light pulse. Meanwhile, the turn-on delay time of the proposed thyristor is reduced to 337 ns.

Multi-Functional CMOS Compatible Nano-Electro-Mechanical Relays for Vapor Phase Explosive Detection

Nano-electro-mechanical (NEM) relays play a very important role in ultra-low standby power and ultra-low power vapor phase gas sensor for Internet-of-Things sensor applications. In this paper, for the first time, we demonstrate a multi-functional fully-CMOS compatible titanium-based NEM relay with 1.8V actuation voltage, ~100Ω R ON , 50ns turn ON delay, and 10 9 ON/OFF current ratio in the ambient conditions. The innovative feature of this paper lies on the novel combination of grayscale electron beam lithography and a bi-layer lift-off process at room temperature (RT) to realize an NEM relay. This novel combination facilitates easy release of structures with an air gap of 25nm and a beam size of 1μm × 1.5μm. As an example, using the proposed self-purging NEM relay, a vapor phase gas sensing application is successfully demonstrated for explosives detection in an ambient air at RT.

Temperature performance analysis of intersubband Raman laser in quantum cascade structures

In this paper we investigate the effects of temperature on the output characteristics of the intersubband Raman laser (RL) that integrated monolithically with a quantum cascade (QC) laser as an intracavity optical pump. The laser bandstructure is calculated by a self-consistent solution of Schrodinger-Poisson equations, and the employed physical model of carrier transport is based on a five-level carrier scattering rates; a two-level rate equations for the pump laser and a three-level scattering rates to include the stimulated Raman process in the RL. The temperature dependency of the relevant physical effects such as thermal broadening of the intersubband transitions (ISTs), thermally activated phonon emission lifetimes, and thermal backfilling of the final lasing state of the Raman process from the injector are included in the model. Using the presented model, the steady-state, small-signal modulation response and transient device characteristics are investigated for a range of sink temperatures (80–220K). It is found that the main characteristics of the device such as output power, threshold current, Raman modal gain, turn-on delay time and 3-dB optical bandwidth are remarkably affected by the temperature.

LDQ10: a compact ultra low-power radiation-hard 4 × 10 Gb/s driver array

A High-speed and low-power VCSEL driver is an important component of the Versatile Link for the high-luminosity LHC (HL-LHC) experiments. A compact low-power radiation-hard 4 × 10 Gb/s VCSEL driver array (LDQ10) has been developed in 65 nm CMOS technology. Each channel in LDQ10 can provide a modulation current up to 8 mA and bias current up to 12 mA. Edge pre-emphasis is employed to compensate for the bandwidth limitations due to parasitic and the turn-on delay of VCSEL devices. LDQ10 occupies a chip area of 1900 μm × 1700 μm and consumes 130 mW power for typical current settings. The modulation amplitude degrades less than 5% after 300 Mrad total ionizing dose. LDQ10 can be directly wire-bonded to the VCSEL array and it is a suitable candidate for the Versatile Link.

A High-Speed Inkjet-Printed Microelectromechanical Relay With a Mechanically Enhanced Double-Clamped Channel-Beam

We report a high-speed inkjet-printed three-terminal microelectromechanical (MEM) relay with a double-clamped beam that exploits the enhanced stiffness of the double-clamped structure to improve electrical performance. To minimize mechanical delay and pull-in voltage, the contact gap between the channel-beam and drain, and the stiffness of the beam and shape of the drain was carefully designed and optimized through a 3-D finite element simulation. The double-clamped beam prevents stiction-related failure between the channel-beam and drain despite the contact gap being only 370 nm for a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$&gt; 500~\mu \text{m}$ </tex-math></inline-formula> long beam. The resulting printed relay delivers a turn-ON delay of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$8~\mu \text{s}$ </tex-math></inline-formula> at a gate voltage of 10 V, a pull-in voltage of only 7.2 V, immeasurable off-leakage, excellent subthreshold swing, and a small hysteresis window of 2 V without any bending or collapsing of the beam. The device also shows reliable operation over <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{5}$ </tex-math></inline-formula> cycles while maintaining a high ON/OFF ratio of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{8}$ </tex-math></inline-formula> , and extremely low ON-state resistance of 3.7 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Omega $ </tex-math></inline-formula> . [2016-0180]

Dynamic modeling of optically pumped electrically driven terahertz quantum cascade lasers

Based on our four-level rate equations model, we analyze through numerical simulations the dynamics of the electron density, population inversion and terahertz intensity present within the cavity of a mid-infrared optically pumped electrically driven THz quantum cascade laser. We find in particular that the mid-infrared pump intensity influences significantly the dynamical behavior of the present device. Moreover, compared to its homologue, the conventional electrically injected THz quantum cascade laser, this system presents much faster dynamics. In addition, within the premises of our model, we derive in the most general case the equation that allows for the determination of the turn-on delay time tth.

Energy-Proportional Photonic Interconnects

Photonic interconnects have emerged as the prime candidate technology for efficient networks on chip at future process nodes. However, the high optical loss of many nanophotonic components coupled with the low efficiency of current laser sources results in exceedingly high total power requirements for the laser. As optical interconnects stay on even during periods of system inactivity, most of this power is wasted, which has prompted research on laser gating. Unfortunately, prior work has been complicated by the long laser turn-on delays and has failed to deliver the full savings. In this article, we propose ProLaser, a laser control mechanism that monitors the requests sent on the interconnect, the cache, and the coherence directory to detect highly correlated events and turn on proactively the lasers of a photonic interconnect. While ProLaser requires fast lasers with a turn-on delay of a few nanoseconds, a technology that is still experimental, several types of such lasers that are suitable for power gating have already been manufactured over the last decade. Overall, ProLaser saves 42% to 85% of the laser power, outperforms the current state of the art by 2× on average, and closely tracks (within 2%--6%) a perfect prediction scheme with full knowledge of future interconnect requests. Moreover, the power savings of ProLaser allow the cores to exploit a higher-power budget and run faster, achieving speedups of 1.5 to 1.7× (1.6× on average).

A 2 MHz 12–100 V 90% Efficiency Self-Balancing ZVS Reconfigurable Three-Level DC-DC Regulator With Constant-Frequency Adaptive-On-Time $V^{2}$ Control and Nanosecond-Scale ZVS Turn-On Delay

This paper presents a miniaturized wide-input-range integrated reconfigurable three-level dc-dc voltage regulator. A three-level buck converter topology with zero-voltage switching (ZVS) is adopted to remove the dominant switching power loss under high-input-voltage condition, thereby enabling the converter to achieve high power efficiency in the megahertz range and reduce the required values of power passives. A constant-frequency adaptive-on-time $V^{2}$ control is proposed to not only regulate the output voltage, but also offer the flying capacitor self-balancing in the megahertz range and over a wide input range for improving the converter reliability. A body diode-based floating ZVS detector is also developed to enable full-ZVS operation of power transistors in high-frequency low duty-ratio conditions with $\leq 5$ ns ZVS turn-on delay. Implemented in a 120 V 0.5 $\mu \text{m}$ CMOS process, the proposed voltage regulator uses four 50 V on-chip power nMOS to support an input voltage from 12 to 100 V and regulates the output voltage at 10 V with a maximum output power of 5 W. The proposed regulator achieves a maximum power efficiency of 90% under the nominal 48 V input and 2 MHz switching frequency. Compared with the state-of-the-art counterparts, the proposed regulator provides >66 times and >2.6 times reductions in the inductance and the total capacitance, respectively.

Characterization of an n-Type 4-kV GTO for Pulsed Power Applications

This paper details the experimental evaluation and simulation of a 4-kV n-type gate turn-OFF thyristor (GTO) designed for pulsed power applications. The primary criteria of evaluation are rate of current rise ( $dI/dt$ ), turn-ON delay time ( $T_{D})$ , and resistance of the device during turn-ON transients [ $R_{\mathrm{\scriptscriptstyle ON}}(t)$ ]. The device under test (DuT) is an n-type asymmetric-blocking GTO manufactured by Silicon Power (Part No. 14N40A10) with a rated dc blocking voltage of 4 kV. A test circuit was specifically designed to minimize stray inductance in order to capitalize on the $dI/dt$ capabilities of the DuT. Experimental data collected from resistance measurements are used to develop a single-switch approximate model for use in simulation. The results of $dI/dt$ experiments provide a profile of DuT $dI/dt$ operation beyond rated values; specifically $dI/dt$ values >70 kA/ $\mu \text{s}$ were readily achieved. The turn-ON delay time of the DuT is also characterized and determined to be $\sim 225$ ns on average.

Influence of Indium-Percentage Variation on Dynamical Characteristics of InxGa1-xAs/GaAs(001) Quantum Dot Lasers

The influence of indium percentage on dynamical characteristics of InxGa1-xAs/GaAs(001) quantum dot lasers (QDLs) is investigated. Energy levels of self-organized truncated-cone-shape QDs are calculated by means of the eight-band k.p model and their dependence to indium percentage is surveyed. Then, by presenting a four-level model and numerical solution of the resulting rate equations, laser properties are determined. Our results show that inclusion of more indium gives rise in the reduced bandgap and electron–hole recombination energy. Moreover, lasing for both Ground State (GS) and Excited States (ES) sounds to be sensitive to indium percentage. It is shown that rise of indium percentage at fixed injected current results in the increased ES turn-on delay and GS photon number and 3 dB modulation bandwidth, and decreased ES photon number, GS turn-on delay, amplitude of relaxation oscillations, output power, and ES 3 dB modulation bandwidth; but has no effect on threshold current and laser gain. At last, we find an optimized cavity length which was likely to be independent from indium percentage.

Modeling of mid-infrared quantum cascade lasers: The role of temperature and operating field strength on the laser performance

In this paper a self-consistent numerical approach to study the temperature and bias dependent characteristics of mid-infrared (mid-IR) quantum cascade lasers (QCLs) is presented which integrates a number of quantum mechanical models. The field-dependent laser parameters including the nonradiative scattering times, the detuning and energy levels, the escape activation energy, the backfilling excitation energy and dipole moment of the optical transition are calculated for a wide range of applied electric fields by a self-consistent solution of Schrodinger–Poisson equations. A detailed analysis of performance of the obtained structure is carried out within a self-consistent solution of the subband population rate equations coupled with carrier coherent transport equations through the sequential resonant tunneling, by taking into account the temperature and bias dependency of the relevant parameters. Furthermore, the heat transfer equation is included in order to calculate the carrier temperature inside the active region levels. This leads to a compact predictive model to analyze the temperature and electric field dependent characteristics of the mid-IR QCLs such as the light-current (L–I), electric field-current (F–I) and core temperature-electric field (T–F) curves. For a typical mid-IR QCL, a good agreement was found between the simulated temperature-dependent L–I characteristic and experimental data, which confirms validity of the model. It is found that the main characteristics of the device such as output power and turn-on delay time are degraded by interplay between the temperature and Stark effects.

Circuit-level implementation of quantum-dot VCSEL

In this paper, for the first time a circuit model of quantum dot InGaAs–GaAs VCSEL including thermal effects is presented. The model is able to predict L-I characteristics for a range of ambient temperatures that the simulation results reveal a good agreement with experimental data reported in literatures. Also the effects of carrier dynamics on the QD-VCSEL performance are simulated that is accordance with results reported by other researcher. The parameters affecting high-speed optical modulation techniques, particularly on–off keying, such as turn-on delay, relaxation oscillations frequency (f ro ) and cutoff frequency for different level modulation currents are investigated. The model is compatible with circuit analysis programs.

Spatial dynamics of high current turn-on in low-voltage AlGaAs/GaAs phototransistors

Dynamic characteristics of low-voltage AlGaAs/GaAs heterostructure N-p-N phototransistors operating in the high-current mode have been studied. It was found that, above critical voltages, the turn-on process of a phototransistor consists of two phases separated in space and time. It is shown that the power of an optical-activation source affects the turn-on delay of the phototransistor and has no effect on the maximum current. An analysis of the spatial current dynamics in the plane of the collector p-n junction demonstrated that the first phase of the turn-on process is localized in the optical activation (optical window) region. In this case, the region of current localization during the first phase may be smaller than the optical-activation region. It was found that the whole current during the second phase is localized at the boundary between the optical window and the ohmic contact. The turn-on delay of the second phase is associated with the carrier transport in the base layer from the optical-activation region to the boundary with the ohmic collector contact.

Serial-Parallel IGBT Connection Method Based on Overvoltage Measurement

This paper deals with a novel method which allows the serial connection of Insulated Gate Bipolar Transistors (IGBTs). The different dynamic characteristics of serially connected IGBTs during turn ON and OFF cause a short-term overvoltage stress in the transistors. In contrary to the commonly used techniques, the presented method reduces additional commutation losses by actively correcting turn ON and OFF delays. The presented method uses overvoltages as measured by a peak detector. The correction circuit doesn’t require a high speed Analog-Digital converter (ADC) or high speed computation. The target power switch unit consists of two serial connected transistors with two identical parallel branches. The well-known 2-level inverter topology equipped with the power switch unit can be connected directly to the high-voltage grid. This converter topology was demanded by our industry partner for 11 MW mining machines. The paper contains a laboratory experiment conducted on a serial-parallel IGBT power switch unit with a tested output power of 1 kW. DOI: http://dx.doi.org/10.5755/j01.eee.22.1.14110

Small-signal transient response and turn-on delay of polariton laser diodes

We present a theoretical description of the small-signal transient response of polariton laser diodes (pol-LDs) based on simplified coupled rate equations describing the exciton reservoir and the ground-state polariton populations. The analytic expressions derived for two pumping geometries, which are valid for all inorganic semiconductors suitable for the realization of pol-LDs, are compared to exact numerical calculations performed for the specific case of GaN-based devices. The two approaches show excellent agreement provided the current step transient remains within the small-signal limit. We report that the temporal attenuation of the envelopes of the oscillations matches half the value of the damping factor () of the pol-LDs, which is proportional to the square of the oscillation relaxation resonance frequency. An explicit expression for the dependence of on both the exciton-photon detuning and the driving current (equivalently the optical pump power) is also obtained. In a further step, we derive the expression for the turn-on delay (td) associated with the build-up of the exciton reservoir population up to its threshold value before coherent light emission occurs. We show that td has the same functional form for the two pumping geometries. It is equal to the effective exciton lifetime () weighted by a logarithmic dependence on the initial and final driving currents. In addition, is shown to be approximately equal to the exciton lifetime, which proves to be the main parameter governing the build-up of polariton lasing/condensation. Beyond electrically driven polariton lasers, we highlight that the temporal shape of the transients could also be easily tested by monitoring the time dependence of the output power of optically pumped polariton lasers subjected to a sudden increase in the continuous wave pump power within the small-signal limit.