Showing papers on "Rise time published in 2013"
TL;DR: In this article, the influence of repetitive square wave voltage rise time on partial discharge pulse characteristics in the ultra-high frequency range was investigated using single-point contact crossed pairs with a wide range of rise times, from 200 ns to 400 μs.
Abstract: This paper focuses on the influence of repetitive square wave voltage rise time on partial discharge pulse characteristics in the ultra-high frequency range. Paerial Discharge (PD) tests on single-point contact crossed pairs were carried out using repetitive square wave voltages with a wide range of rise times, from 200 ns to 400 μs, including also 50 Hz sinusoidal voltage waveforms. Experimental results show that rise time has a significant influence on magnitude and frequency spectrum of PD pulses. Voltages of shorter rise times generate larger PD pulses with a predominance of high frequency components in the energy spectrum. Interpretations are presented for this phenomenon.
124 citations
TL;DR: In this article, the authors integrate vanadium dioxide into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>10^3) in both electrically (i.e. by bias voltage, referred to as E-MIT) and thermally driven transitions.
Abstract: Vanadium dioxide is a correlated electron system that features a metal-insulator phase transition (MIT) above room temperature and is of interest in high speed switching devices. Here, we integrate VO2 into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>10^3) in both electrically (i.e. by bias voltage, referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine transient switching characteristics of the E-MIT and observe two distinguishable time scales for switching. We find an abrupt jump in conductivity with a rise time of the order of 10 ns followed by an oscillatory damping to steady state on the order of several {\mu}s. We characterize the RF power response in the On state and find that high RF input power drives VO2 further into the metallic phase, indicating that electromagnetic radiation-switching of the phase transition may be possible. We measure S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at 2.95 dB across the frequency range in the On state and sufficient isolation of over 25 dB is observed in the Off state. We are able to simulate the RF response accurately using both lumped element and 3D electromagnetic models. Extrapolation of our results suggests that optimizing device geometry can reduce insertion loss further and maintain broadband flatness up to 40 GHz.
98 citations
TL;DR: In this article, the authors integrate vanadium dioxide into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>103) in both electrically (i.e., by bias voltage, referred to as E-MIT) and thermally driven transitions.
Abstract: Vanadium dioxide (VO2) is a correlated electron system that features a metal-insulator phase transition (MIT) above room temperature and is of interest in high speed switching devices. Here, we integrate VO2 into two-terminal coplanar waveguides and demonstrate a large resistance modulation of the same magnitude (>103) in both electrically (i.e., by bias voltage, referred to as E-MIT) and thermally (T-MIT) driven transitions. We examine transient switching characteristics of the E-MIT and observe two distinguishable time scales for switching. We find an abrupt jump in conductivity with a rise time of the order of 10 ns followed by an oscillatory damping to steady state on the order of several μs. We characterize the RF power response in the On state and find that high RF input power drives VO2 further into the metallic phase, indicating that electromagnetic radiation-switching of the phase transition may be possible. We measure S-parameter RF properties up to 13.5 GHz. Insertion loss is markedly flat at 2.95 dB across the frequency range in the On state, and sufficient isolation of over 25 dB is observed in the Off state. We are able to simulate the RF response accurately using both lumped element and 3D electromagnetic models. Extrapolation of our results suggests that optimizing device geometry can reduce insertion loss further and maintain broadband flatness up to 40 GHz.
92 citations
TL;DR: The use of switches having a non-null transition between the on and off state is taken into account and the impact on the radiation features is studied and verified through a set of numerical results also in comparative fashion with ordinary rectangular pulses.
Abstract: Time-modulated arrays (TMAs) are antenna systems where the transmitted or received signal is modulated by periodic time pulses. Several strategies have been proposed for defining the characteristics of the pulse sequence to control the antenna radiation pattern starting from the hypothesis of ideal radio-frequency (RF) switches with instantaneous rise and fall time. In this paper, the use of switches having a non-null transition between the on and off state is taken into account and the impact on the radiation features is studied and verified through a set of numerical results also in comparative fashion with ordinary rectangular pulses.
89 citations
TL;DR: In this paper, the bias margin and bit error rate of a low-power adiabatic quantum-flux-parametron (AQFP) gate were optimized in terms of both bit energy and bias margin.
Abstract: We optimized the circuit parameters of a low-power adiabatic quantum-flux-parametron (AQFP) gate in terms of both bit energy and bias margin and confirmed that the bit energy of the optimized gate with a rise time of 200 ps can be decreased to 6% of IcΦ0, where Ic is the critical current of the Josephson junctions and Φ0 is the single flux quantum. In addition, we investigated the effect of thermal noise on the operation of the optimized AQFP gate. The bias margins and bit error rate of the AQFP gate were examined at finite temperature through circuit simulations, in which the thermal noise was taken into account using the Monte Carlo method. The bias margin of the AQFP gate with bias margins of ±26% at zero temperature shrunk to ±19.4% at 4.2 K, but is still large enough for circuit applications.
62 citations
TL;DR: In this paper, the transient response of BOTDA and ROTDR sensors are obtained through solution of the mass, energy and heat transfer in soil and fiber cable, and it is shown that the mechanical rise time is of the order of a few minutes, which is in agreement with the experimental results of both sensors.
55 citations
TL;DR: In this paper, micro-electro-mechanic systems (MEMS) acoustic emission transducers are manufactured using an electroplating technique, and the transducers use a capacitance change as their transduction principle, and are tuned to the range 50?200?kHz.
Abstract: In this paper, micro-electro-mechanic systems (MEMS) acoustic emission (AE) transducers are manufactured using an electroplating technique. The transducers use a capacitance change as their transduction principle, and are tuned to the range 50?200?kHz. Through the electroplating technique, a thick metal layer (20??m nickel?+?0.5??m gold) is used to form a freely moving microstructure layer. The presence of the gold layer reduces the potential corrosion of the nickel layer. A dielectric layer is deposited between the two electrodes, thus preventing the stiction phenomenon. The transducers have a measured quality factor in the range 15?30 at atmospheric pressure and are functional without vacuum packaging. The transducers are characterized using electrical and mechanical tests to identify the capacitance, resonance frequency and damping. Ultrasonic wave generation using a Q-switched laser shows the directivity of the transducer sensitivity. The comparison of the MEMS transducers with similar frequency piezoelectric transducers shows that the MEMS AE transducers have better response characteristics and sensitivity at the resonance frequency and well-defined waveform signatures (rise time and decay time) due to pure resonance behavior in the out-of-plane direction. The transducers are sensitive to a unique wave direction, which can be utilized to increase the accuracy of source localization by selecting the correct wave velocity at the structures.
35 citations
TL;DR: In this article, a 2.2 kV, 1 ns pulsed power circuit with a single prime switch that utilizes a low-voltage dc power supply to pump and pulse the DSRD in the forward and reverse directions is presented.
Abstract: Drift-step-recovery diodes (DSRDs) are used in pulsed-power generators to produce nanosecond-scale pulses with a rise rate of the order of 1 kV/ns. A 2.2 kV, 1 ns pulsed power circuit is presented. The circuit features a single prime switch that utilizes a low-voltage dc power supply to pump and pulse the DSRD in the forward and reverse directions. An additional low-current dc power supply is used to provide a voltage bias in order to balance the DSRD forward with respect to its reverse charge. The DSRD was connected in parallel to the load. In order to study the circuit's efficiency, it was operated over a wide range of operating parameters, including the main and bias source voltages, and the trigger duration of the prime switch. A peak voltage of 2.2 kV with a rise time of less than 1 ns and a rise rate of 3 kV/ns was obtained, where the efficiency was 24%. A higher efficiency of 52% was obtained when the circuit was optimized to an output peak voltage of 1.15 kV. The circuit was operated in single-shot mode as well as in bursts of up to 100 pulses at a repetition rate of 1 MHz. The experimental results are supported by a PSPICE simulation of the circuit. An analysis of the circuit input and output energies with respect to the MOSFET and DSRD losses is provided.
34 citations
28 Oct 2013
TL;DR: In this paper, a high-frequency, digitally controlled high-brightness LED driver for automotive applications with fast dimming capabilities is presented, which exploits the inherent stabilizing effect of magnetic coupling, and combines it with a dedicated duty-cycle feedforward technique for step-reference response enhancement during dimming operation.
Abstract: This paper presents a high-frequency, digitally controlled High-Brightness LED driver for automotive applications with fast dimming capabilities. The power converter is based on the magnetically coupled C uk topology employing a single off-the-shelf SMT mutual inductor. The proposed digital control technique exploits the inherent stabilizing effect of magnetic coupling, and combines it with a dedicated duty-cycle feedforward technique for step-reference response enhancement during dimming operation. No direct sensing of the LED string current is performed, bypassing the disadvantage of the C uk topology of having an inverted output polarity. Furthermore, the magnetically coupled C uk topology is a single-switch solution and it provides inherent filtering of the input and output currents without introducing additional magnetic elements, strongly reducing the total required capacitance and maintaining the small form-factor required in the automotive environment. The paper discusses the theoretical and practical development of the proposed controller. Experimental tests on a 40 W, 1 A, 500 kHz prototype indicate a 0 to 1 A current rise time in the tens of microseconds time frame with excellent damping characteristics and regulation accuracy.
32 citations
TL;DR: In this article, the effect of cathode materials on the amplitude of the super-shortavalanche electron beam (SAEB) current and X-ray density during discharges in atmospheric-pressure air was investigated.
Abstract: In this work, experiments were performed to study the effect of cathode materials on the amplitude of the super-shortavalanche electron beam (SAEB) current and X-ray density during discharges in atmospheric-pressure air. In theexperiments, discharges were generated by three nanosecond-pulse generators in air gaps between a plane anode and atubular cathode made of different metals. The output pulse of the three generators had a rise time of 0.3, 1, 15 ns, anda full width at half maximum of 1, 2, 30–40 ns, respectively. For the generators with pulse rise-time of 0.3 and 1 ns,the cathodes used in these experiments were made of stainless steel, permalloy, titanium, niobium, copper, brass, andaluminum. For the generator with pulse rise-time of 15 ns, the cathodes were made of stainless steel, titanium, copper,and aluminum. When the rise time of the applied pulse is 0.3 ns, our experimental results show that the amplitude ofthe voltage across the gap depends on the cathode material and reaches its maximum value when a stainless steelcathode is used. It is also observed that, under such situation, the maximum amplitudes of the SAEB current occur atmaximum voltages across the gap when all other factors are equal. Furthermore, the amplitude of the SAEB currenthereof is found to depend not only on the material of the sharp edge of the tubular cathode, but also on the material ofthe side surface of the tubular cathode. When the rise time of the applied pulse is 1 ns, the experimental results showthat the average number of electrons in SAEB is also affected by the cathode materials. In addition, in the case that therise time of the voltage pulse is 15 ns and the gap spacing is 8 cm, the experimental results show that the cathodematerial has no effect on the voltage amplitude across the gap and the X-ray density. The increase of the pulserepetition frequency from 250 to 500 Hz under such condition can lead to a three-fold increase in X-ray density in arepetitive pulsed mode.Keywords: Air diffuse discharge; Cathode material; Nanosecond pulse; Super-short avalanche electron beam;X-ray density
30 citations
TL;DR: Pulser is capable to produce up to 1MHz pulse trains with positive 50V-1kV pulses with up to 10A peak output current and fully satisfies desired 1MHz bandwidth.
Patent•
31 May 2013TL;DR: In this paper, a power converter including a transformer and a full-bridge circuit including parallel-connected first and second arms, each including series-connected FETs, is described.
Abstract: A power converter including: a transformer in which first and second voltages are induced; a full-bridge circuit including parallel-connected first and second arms each including series-connected FETs; and a control circuit, wherein, within a given time period for which a voltage V2 is the first voltage, the control circuit performs control so that FETs in at least one arm are on for an on time period, and, when Pon, PX, PS, α, and β respectively denote a duration of the on time period, a duration of the given time period, a duration of a time period from the end of the on time period to a time point of transition from the first to second voltage, a rise time of a body diode of each FET, and a fall time of the body diode, Pon>(β/α)PS, 0≦PS<α, and Pon+PS≦PX are satisfied.
TL;DR: In this paper, the effect of the rise time of pulse voltage on the electrical properties of epoxy/TiO2 nanocomposites focusing on surface charge accumulation and decay was investigated.
Abstract: Polymeric insulating materials exposed to pulse voltage with a nanosecond rise time in pulsed power have drawn increasing attention. Surface charge accumulation and decay on the charged polymers are very important parameters related to discharge. Nanocomposite technology has been used to improve the electrical properties of polymeric insulating materials. Therefore, it must be confirmed whether the nanosecond rise time of pulse voltage on the dynamic behaviour of surface charge on polymeric nanocomposites is different from that without nanoparticles. In this paper, we attempted to clarify the effect of the rise time on the electrical properties of epoxy/TiO2 nanocomposites focusing on surface charge accumulation and decay. Samples were prepared by dispersing nano-scale TiO2 particles into epoxy (EX) by mixing with shear force. Corona charging tests were performed at room temperature with a relative humidity of ~40%. The charge distribution was measured by means of an electrostatic voltmeter. The results show that the rise time plays an important role in the accumulating charge as well as the charge decay rate and varies with the concentration of nanoparticles and charge polarity. It is suggested that charge dynamics are dependent upon the rise time.
TL;DR: In this article, a compact Marx generator based on pulse forming network (PFN) along with a peaking capacitor rated at 300 kV and 64 J was proposed. But the performance of the peaking capacitance was not evaluated.
Abstract: This paper presents the design and development of a compact Marx generator based on pulse forming network (PFN) along with a peaking capacitor rated at 300 kV and 64 J. Proposed scheme consists of identical PFNs connected across the charging and grounding resistors according to the Marx generator scheme. Modular construction of the Marx generator is useful in altering the stage capacitance to obtain varying pulse rise time and wave shapes at the output. A peaking capacitor connected at the output of the Marx generator significantly improves the rise time from 25 to 5 ns suitable for driving an antenna load. The effect of peaking capacitor on the intensity of far-field radiation is simulated using finite integration technique for a distance of 15, 20, 30, 40, and 50 m and the results are presented and discussed.
TL;DR: The results indicate the feasibility of rise time discrimination as a technique for measuring event DOI while maintaining sensitivity, timing and energy performance, in a well-known detector architecture.
Abstract: Clinical TOF PET systems achieve detection efficiency using thick crystals, typically of thickness 2-3 cm. The resulting dispersion in interaction depths degrades spatial resolution for increasing radial positions due to parallax error. Furthermore, interaction depth dispersion results in time pickoff dispersion and thus in degraded timing resolution, and is therefore of added concern in TOF scanners. Using fast signal digitization, we characterize the timing performance, pulse shape and light output of LaBr3:Ce, CeBr3 and LYSO. Coincidence timing resolution is shown to degrade by ~50 ps/cm for scintillator pixels of constant cross section and increasing length. By controlling irradiation depth in a scintillator pixel, we show that DOI-dependence of time pickoff is a significant factor in the loss of timing performance in thick detectors. Using the correlated DOI-dependence of time pickoff and charge collection, we apply a charge-based correction to the time pickoff, obtaining improved coincidence timing resolution of <; 200 ps for a uniform 4 × 4 × 30 mm3 LaBr3 pixel. In order to obtain both DOI identification and improved timing resolution, we design a two layer LaBr3[5%Ce]/LaBr3[30%Ce] detector of total size 4 × 4 × 30 mm3, exploiting the dependence of scintillator rise time on [Ce] in LaBr3:Ce . Using signal rise time to determine interaction layer, excellent interaction layer discrimination is achieved, while maintaining coincidence timing resolution of <; 250 ps and energy resolution <; 7% using a R4998 PMT. Excellent layer separation and timing performance is measured with several other commercially-available TOF photodetectors, demonstrating the practicality of this design. These results indicate the feasibility of rise time discrimination as a technique for measuring event DOI while maintaining sensitivity, timing and energy performance, in a well-known detector architecture.
26 May 2013
TL;DR: In this paper, a 10 kV-class SiC IGBT was used for a short-circuited load at a collector bias of 4500 V and showed a temperature-invariant, withstand time in excess of 20 μs.
Abstract: Open-base breakdown voltages as high as 10.5 kV (91% of theoretical avalanche limit and 125 V/μm), on-resistance of 110 mΩ-cm2 close to the unipolar limit of 94 mΩ-cm2, and current gain as high as 75 are measured on 10 kV-class SiC BJTs. Monolithic Darlington-connected BJTs fabricated on the same wafer yield current gains as high as 3400, and show Si BJT-like output characteristics with a differential on-resistance as low as 44 mΩ-cm2 in the saturation region and a distinct quasi-saturation region. Switching measurements performed at a DC link voltage of 5 kV and collector current of 8 A feature a collector current rise time as low as 30 ns during turn-on and collector voltage recovery time as low as 100 ns during turn-off. Very low turn-on and turn-off switching energies of 4.2 mJ and 1.6 mJ, respectively, are extracted from the switching transients, which are 19 and 25 times smaller than the corresponding switching energies reported on 6.5 kV Si IGBTs. When turnedon to a short-circuited load at a collector bias of 4500 V, the 10 kV BJT shows a temperature-invariant, withstand time in excess of 20 μs. Leakage currents <; 1μA (system limit) are measured, even after 234 hours of operation under a DC collector bias of 5000 V at elevated temperatures.
TL;DR: A parametric study was conducted to design a short-pulse Marx generator dedicated to this kind of application, and the best compromise was chosen to generate short-rise time high-voltage pulses with a low quantity of energy.
Abstract: The generation of high-power microwaves can be used in the field of military (protection of convoys and improvised explosive device neutralization) and civil applications (study of biological phenomena such as electroporation, treatment of waste water, and so on). The implementation of such systems requires the use of a high-voltage pulsed source capable of operating in repetitive mode at 100 Hz for a few seconds or at 1 Hz during several hours. A pulse forming line (PFL) is used to convert the monopolar output signal of the generator into a bipolar pulse, which is more suitable to feed an antenna. It induces significant constraints for the pulse generator, which has to supply a mismatched load. Further constraints such as weight, volume, and energy efficiency have to be considered to facilitate the integration of the system on mobile platforms. It also has to be easily remote-controlled to facilitate its use in an operational context. A parametric study was conducted to design a short-pulse Marx generator dedicated to this kind of application. The best compromise was chosen to generate short-rise time high-voltage pulses with a low quantity of energy. For higher energy levels, other stages with a higher capacity can easily be used, using our modular coaxial structure. The tested 11-stage short-pulse Marx generator, connected to a PFL, reached an output voltage of 420 kV, with a rise time , at a 40-kV charging voltage. Inductive charging circuits allow operation in repetitive mode up to 100 Hz during a few seconds. The generator was operated at 1 Hz during several hours using a remote-controlled charging unit. For mobile applications, the generator can be charged by a battery-powered power supply unit.
TL;DR: The system presented here was developed specifically for controlling the quantum state of trapped ions with sequences of multiple laser pulses, including composite and bichromatic pulses, and is widely applicable to other atomic systems ranging across quantum information processing, frequency metrology, atom interferometry, and single-photon generation.
Abstract: We demonstrate a system for fast and agile digital control of laser phase, amplitude and frequency for applications in coherent atomic systems. The full versatility of a direct digital synthesis radiofrequency source is faithfully transferred to laser radiation via acousto-optic modulation. Optical beatnotes are used to measure phase steps up to 2π, which are accurately implemented with a resolution of ≤ 10 mrad. By linearizing the optical modulation process, amplitude-shaped pulses of durations ranging from 500 ns to 500 ms, in excellent agreement with the programmed functional form, are demonstrated. Pulse durations are limited only by the 30 ns rise time of the modulation process, and a measured extinction ratio of > 5 × 10(11) is achieved. The system presented here was developed specifically for controlling the quantum state of trapped ions with sequences of multiple laser pulses, including composite and bichromatic pulses. The demonstrated techniques are widely applicable to other atomic systems ranging across quantum information processing, frequency metrology, atom interferometry, and single-photon generation.
TL;DR: Based on the electro-optic effect, a small size (mm), wide measuring-amplitude (MV/m), mono-shield structure, integrated electrooptic sensor is designed and developed as discussed by the authors.
Abstract: The spatial electric field is a key parameter for gas discharge research. Based on the electro-optic effect, a small size (mm), wide measuring-amplitude (MV/m), mono-shield structure, integrated electro-optic sensor is designed and developed. The ns-level time domain calibration system of the sensor is established. The calibration result shows that the output electric field is linear with the input signal, and the dynamic response time of the sensor is less than 2 ns. Using the developed sensors, the spatial electric field of a 1-m rod-plane air gap discharge is tested and the sudden step of an electric field is detected. As the imposed voltage increases, the probability and amplitude of the electric field step increased as well. This step phenomenon is confirmed to be the inception and development of a streamer; the confirmation is made by means of simultaneously captured photos. The rise time and the amplitude of the electric field step are discussed. Accordingly, the integrated electro-optic sensor will be a powerful tool for studying the mechanism of air gap discharges.
TL;DR: In this paper, a 5 kHz full power modulation experiment is demonstrated on a 170 GHz gyrotron, which employs a fast short-circuited switch between the anode and the cathode of the triode-type electron gun (single anode switch).
Abstract: A 5 kHz full power modulation experiment is demonstrated on a 170 GHz gyrotron. 5 kHz high-power and beam on/off modulation is achieved by employing a fast short-circuited switch between the anode and the cathode of the triode-type electron gun (single anode switch). Lower heat load on the cavity and the collector compared with continuous-wave operation realizes more than 1 MW oscillation with 1 MW designed gyrotron. The maximum achieved power is 1.16 MW with an electrical efficiency of 48%. In the high-efficiency operation, an unwanted mode oscillation is observed at the start-up phase of each pulse, which is induced by the slow voltage rise time of the anode. For faster rise of the anode voltage, another fast switch is inserted between an anode voltage divider and the anode (double anode switch). In the experiment, successful fast start-up of the anode voltage and minimized unwanted mode generation are observed.
TL;DR: An acoustic trap with miniaturized integrated transducers for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength, and the results emphasize the importance of selecting the proper drive frequency for long term handling of cells.
TL;DR: In this article, a dielectric barrier discharge (DBD) of coaxial geometry has been investigated, where the discharge cell was filled by 100 mbar of argon and driven by positive square voltage pulses with a rise time of 20 ns and 75 ns.
Abstract: A dielectric barrier discharge (DBD) of coaxial geometry has been investigated. The discharge cell was filled by 100 mbar of argon and driven by positive square voltage pulses with a rise time of 20 ns and 75 ns. The internal discharge characteristics such as the discharge current, the gas gap voltage, the instantaneous power and energy have been determined from measured current and voltage waveforms. The peculiarities of the experimental evaluation of the discharge parameters are discussed in detail. Special attention is paid to the accurate experimental determination of the key capacitance values of the DBD, namely the capacitance of the reactor cell Ccell and the capacitance of the dielectric barriers Cd. The influence of the capacitance value accuracy on precision of electrical characterization is demonstrated and it is shown that a small uncertainty in the Cd value leads to large errors in the evaluation of the gas gap voltage. Nevertheless, the obtained accuracy of the capacitance values allows the reliable comparison of the electrical DBD parameters. These are sensitive to the mode of discharge excitation. The shortening of the voltage rise time leads to the increase of the total and instantaneous energy as well as the peak power dissipated into the discharge. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
TL;DR: In this paper, a ripple-free step-pressure generator with a rise time below 1 ms was used to estimate the step dynamic pressure in the high-pressure range, and the estimated dynamic pressure was verified by analytical and experimental approaches.
Abstract: Recently, the need for calibration of dynamic pressure sensors has increased as calibration is required for more reliable measurements in advanced industries Up until recently, most dynamic sensors have been calibrated by reference sensors, which were calibrated by static pressure standards Dynamic calibrators are available, but in reality they are not traceable to the international standards In the high-pressure range, reliable high dynamic pressure instruments using step pressure generators and their standardization are required In this paper, step dynamic pressure without any ripple in the output signal was implemented by quick-opening valves Since the impulse caused by a trigger mechanism was minimized, a ripple-free step pressure with a rise time below 1 ms could be generated up to 830 MPa (120 000 psi) In addition, the generated step dynamic pressure was estimated based on the density equations in order to establish the high dynamic pressure standard The estimated dynamic pressure could be verified by analytical and experimental approaches
TL;DR: In this paper, a detailed experimental investigation of the currentvoltage characteristics of deca-nanometer gated-thyristors is presented, highlighting that strong differences exist between the static and the dynamic operation of these devices.
Abstract: This letter presents a detailed experimental investigation of the current-voltage characteristics of deca-nanometer gated-thyristors, highlighting that strong differences exist between the static and the dynamic operation of these devices. In particular, results reveal that the forward-breakover voltage determining thyristor turn-on does not depend only on the applied gate voltage, but also on the rise time of the applied gate pulse, decreasing for fast pulse fronts. This is explained in terms of a higher electron injection from the cathode to the anode triggering device turn-on when the gate switching time is shorter than that required for holes to leave the p-base.
TL;DR: In this paper, the measurement error of the parameters of the standard unidirectional impulse waveforms due to the distortion induced by the limited bandwidth of the measuring system is predicted.
Abstract: Analytical formulas derived here are capable of predicting the measurement error of the parameters of the standard unidirectional impulse waveforms due to the distortion induced by the limited bandwidth of the measuring system. The parameters subject to analysis are the rise time and the peak value. The standard waveforms considered are those defined in the IEC 61000-4-2 (electrostatic discharge), -4-4 (electrical fast transient/burst) and -4-5 (surge 1,2/50 μs and 8/20 μs) standards. The results obtained are of importance for the evaluation of the calibration uncertainty of the standard unidirectional impulse generators and associated coupling/decoupling networks as well as for the design of the corresponding measuring systems. Analytical predictions are confirmed by numerical simulations.
TL;DR: In this paper, the authors describe micro electrochemical machining (ECM) using the electrostatic induction feeding method and show that gap distance can be decr eased to several micro meters by using pulse durations shorter than several tens of nano seconds.
TL;DR: In this article, the authors proposed several topologies for pulsed generators based on an all solidstate Marx and a magnetic switch (MS) modulator utilizing insulated gate bipolar translators (IGBTs).
Abstract: An all solid-state Marx modulator utilizing Insulated Gate Bipolar Translators (IGBTs) is capable of outputting pulses with variable pulse width, repetitive pulse frequency and varying voltage amplitude. But the relatively slow turn-on speed of IGBT with high current loads result in slow rise time of output pulses. If a magnetic switch (MS) is combined with an all solid-state Marx, it will be quite simple to obtain nanosecond pulses with rise times under 100 ns. In this paper, several topologies for pulsed generators are proposed based on an all solidstate Marx and MS. When MS is connected in series with Marx, the rise time of the 200-Ampere load pulse is reduced from 560 ns to 85 ns. Besides, the switch-on loss of all IGBTs is considerably reduced. When a peaking capacitor is added, a 30 kV exponential decaying pulse with a rise time of 36 ns is obtained on a 100 ? resistor load. When the peaking capacitor is replaced by 20 m long pulse forming line (PFL), a 12.4 kV rectangular pulse with 223 ns pulse width (full width at half maximum), 44 ns rise time and 56 ns fall time is obtained on a 50 Ω resistor load. When the PFL is replaced by a Blumlein Transmission Line (BTL), the amplitude of the load voltage can be doubled on the price of a larger pre-pulse. Besides, generator with BTLs is quite proper for dielectric barrier discharge (DBD) loads. Experiments show that over 10 DBDs are excited in 4 μs under a single shot, which means extremely intense plasma is produced due to the accumulation effect. This phenomenon suggests great potential value for industrial applications.
TL;DR: In this paper, the scaling of the pressure rise time inside a gas pocket that is trapped between a gravity wave and a rigid structure during a slamming event was investigated, and the results showed that both the pressure amplitude and the rise time are scaled accurately for the investigated gas pocket slamming event.
16 Jun 2013
TL;DR: In this paper, the authors compared the performance of the planar and trench-3 IGBT switches for pulsed power applications and showed that the latter is more suitable for high average power, high pulse repetition rate applications.
Abstract: One of the key components of pulsed power technology is the switch, which is increasingly realized using semiconductor switches. Use of solid state switches, if properly designed, provides longer lifetime, reliability, and reduces maintenance as compared to the conventional spark gaps which are used in Marx generators or other devices for pulsed power applications today. An analysis of commercial semiconductor switches favors the IGBT for pulsed power applications, in particular for high average power, high pulse repetition rate applications, due to its widespread use in drive applications and its availability. High power IGBT modules rated at 4.5 kV / 800 A of two different technologies have been investigated in this work: the planar technology and the trench3 technology. Both types of semiconductor switches were tested in a special low inductance setup to characterize the IGBT for pulsed power applications. For this characterization, the development of a dedicated gate drive unit enables the IGBT to generate fast rise times for the collector current and fast fall times for the collector-emitter voltage. The results show that the planar technology is preferable for pulsed power applications. The IGBT with the planar technology was characterized at a DC link voltage of 4kV and a peak current of 2kA. The switching time of the IGBT stays in the region of 200ns (tfall time(20-80%)) of the collector-emitter voltage, while the rise time of the collector current is 160ns (trise time(10-90%)) with peak power losses of 1.41MW. The associated junction temperature of the chip will be increased by approximately 1K only. This allows to use the IGBT at higher pulse repetition rates (PRF) up to 2kHz, at a pulse duration of 1μs, without additional cooling. The switching speed of the IGBT can be influenced by the matching network and depends on the application which will be realized with the IGBT. The IGBT with the trench3 technology shows gate voltage oscillations at peak currents above 1 kA, which infers that the gate source capacitance will be slowly destroyed by overvoltage. These oscillations can be explained with the higher gate source capacitance of the trench3 technology as compared to the planar technology, in combination with the unavoidable gate inductance. The planar technology, on the other hand, is realized with a low inductance gate runner topology and can thus be used at shorter pulse rise times. The results present a commercial semiconductor which is suitable for a pulsed power application. The IGBT with the planar technology can be used with the right choice of the driver matching network for a pulsed power application. Furthermore there is no need to design a switch using small, discrete semiconductor devices. That saves cost and keeps the circuit development simple. Only the gate drive unit is developed in-house particularly for pulsed power applications. The technical functions and the economic efficiency are accordingly balanced as well.
TL;DR: The I-type sensor has coaxial cylinder shape, which consists of a brass inner conductor, a Teflon middle dielectric, and an aluminum outer conductor, and the measured attenuation ratio was in good agreement with the calculated ratio within 7.5%. The operational characteristics of the sensor were tested by measuring high-voltage pulses generated from a Blumlein pulse forming line as mentioned in this paper.
Abstract: D-dot sensors were designed and tested for the measurement of nanosecond high-voltage pulses. Computer simulation results showed that the I-type sensor has an acceptable response in a wide range of frequency among three types of sensors such as I, ∇, and T. The I-type sensor has coaxial cylinder shape, which consists of a brass inner conductor, a Teflon middle dielectric, and an aluminum outer conductor. Since I-type showed good linearity up to 1.2 GHz, we calibrated the sensor using relatively low frequencies. The attenuation ratio of the integrated signal of the D-dot sensor was calibrated against a standard high-voltage probe (Tektronix P6015, 75-MHz bandwidth). The measured attenuation ratio and standard deviation were 7.70×1012 and 0.0608×1012, respectively. The measured attenuation ratio was in good agreement with the calculated ratio within 7.5%. The operational characteristics of the sensor were tested by measuring nanosecond voltage pulses generated from a Blumlein pulse forming line. We measured high-voltage pulses having 300 kV, 5-ns pulsewidth, and 300-ps rise time using the designed D-dot sensor. The accuracy of the sensor enabled detection of several tens of picosecond differences in the rise time of the high-voltage pulses resulting from different gap distances in the peaking switch.