Pulse Circuit Research Articles

Influence of Matrix Circuit Switching Device Junction Capacitance on Piezoelectric Actuator Drive Performance

Piezoelectric actuators are widely used as fine-motion actuators for positioning devices. Current pulse driving reduces displacement hysteresis, and the drive circuit provides current pulses considered constant charge pulses to the piezoelectric actuator. The circuit for devices with multiple degrees of freedom using multiple piezoelectric actuators should be simple. Matrix circuits are used to drive liquid crystal displays to reduce the number of drive-circuit control signals and components. A group of 2 × 2 piezoelectric actuators was driven alternately using a 4-switch matrix circuit, and two field effect transistors were used as a fast matrix circuit switch. Piezoelectric actuator drive performance was studied in the case of using the current pulse circuit and the matrix circuit. When the matrix circuit drove actuators performing as capacitive loads, switching device junction capacitors adversely affected drive performance.

Pulsed Nano-Electrospray Ionization: Characterization of Temporal Response and Implementation with a Flared Inlet Capillary

The temporal response of pulsed nano-electrospray ionization mass spectrometry (nano-ESI-MS) was studied and its influence on ion formation and detection was characterized. Rise and decay times for the mass resolved ion current were determined to be 20 ± 3 msec and 61 ± 5 msec, respectively, which led to a maximum pulse rate of 12 Hz. Pulsed nano-ESI operation was demonstrated from a multi-sprayer source controlled by a high voltage pulsing circuit constructed in-house. The desired source mode of operation (e.g. pulsing or continuous) can be realized solely by controlling the voltage applied to each sprayer.

Kinetic modeling of active chlorine generation by low-amperage pulsating direct current in a circulating brine solution

A kinetic model was proposed to describe the generation of active chlorine species (ACS) in circulating 3% NaCl solution subjected to the treatments of low-amperage (0.01 A) pulsating direct current (PC) as a first step towards an effective circulation electrochemical brine disinfection process with low ACS level. The model was developed based on the mass balance between the electrochemical production and evaporation loss of ACS during the process, and found to predict reasonably well the sigmoidal ACS concentration profiles. Kinetic analysis revealed that at the same amperage, ACS was generated at a lower level by PC treatment than by normal direct current (DC) treatment through lowering of the frequency of current pulse and the capacity of condenser in the pulse circuit. This implies that PC could be more useful than DC for the delicate control of ACS at an appropriately low level during circulating electrochemical brine disinfection.

Cost-effective broad-band electrical impedance spectroscopy measurement circuit and signal analysis for piezo-materials and ultrasound transducers.

This paper explains the circuitry and signal processing to perform electrical impedance spectroscopy on piezoelectric materials and ultrasound transducers. Here, we measure and compare the impedance spectra of 2-5 MHz piezoelectrics, but the methodology applies for 700 kHz-20 MHz ultrasonic devices as well. Using a 12 ns wide 5 volt pulsing circuit as an impulse, we determine the electrical impedance curves experimentally using Ohm's law and fast Fourier transform (FFT), and compare results with mathematical models. The method allows for rapid impedance measurement for a range of frequencies using a narrow input pulse, digital oscilloscope and FFT techniques. The technique compares well to current methodologies such as network and impedance analyzers while providing additional versatility in the electrical impedance measurement. The technique is theoretically simple, easy to implement and completed with ordinary laboratory instrumentation for minimal cost.

Cost-effective broad-band electrical impedance spectroscopy measurement circuit and signal analysis for piezo-materials and ultrasound transducers

This paper explains the circuitry and signal processing to perform electrical impedance spectroscopy on piezoelectric materials and ultrasound transducers. Here, we measure and compare the impedance spectra of 2–5 MHz piezoelectrics, but the methodology applies for 700 kHz–20 MHz ultrasonic devices as well. Using a 12 ns wide 5 volt pulsing circuit as an impulse, we determine the electrical impedance curves experimentally using Ohm's law and fast Fourier transform (FFT), and compare results with mathematical models. The method allows for rapid impedance measurement for a range of frequencies using a narrow input pulse, digital oscilloscope and FFT techniques. The technique compares well to current methodologies such as network and impedance analyzers while providing additional versatility in the electrical impedance measurement. The technique is theoretically simple, easy to implement and completed with ordinary laboratory instrumentation for minimal cost.

3D Simulation of magnetic field distribution in electromagnetic forming systems with field-shaper

Impulse electromagnetic forming (IEMF) is an effective and powerful technique widely used for joining and shaping metals and field-shaper is a main part of the electromagnetic forming which has important effect on the distribution of magnetic field. In this technique, a metal work-piece is pushed to a die and formed by a pressure created using an intensive, transient magnetic field. This magnetic field is produced by passing a pulse of electric current through a forming coil in a pulsed power circuit. The produced transient magnetic field induces eddy currents in the surface of work-piece. Induced eddy currents in work-piece produce a magnetic field with reverse direction of initial magnetic field; this results in a mutual repulsion between coil and work-piece and in this way the work-piece is thrown toward the die. In this process created magnetic forces applied to work-piece are much like uniform, but in real applications, some regions of a work-piece have to be more deformed and therefore a much greater pressure has to be applied to these regions. The task of concentration of magnetic forces to some desired regions can be accomplished using field-shapers. Yu et al. [Yu, H., Li, C., Zhao, Z., Li, Z., 2005. Effects of field-shaper on magnetic pressure in electromagnetic forming. J. Mater. Process. Technol. 168, 245–249] have recently shown the effect of field-shaper on the distribution of the magnetic fields in electromagnetic forming, but because of the nature of 2D simulations some edge effects in real geometries could not be taken into consideration. In this paper, a 3D simulation using the FEA software MAXWELL has been applied to study the magnetic field distribution during an impulse electromagnetic forming process. Comparison of the 3D and 2D simulation results indicates that the maximum magnetic fields achieved in front of nodules of the field-shaper are about 15% stronger than those expected by 2D simulations. By changing the geometry of the field-shaper, the influence of the shape of the field-shaper on the distribution of the applied forces on the work-piece has been studied. Based on these simulations, some simple guidelines to design the field-shaper have been derived.

MULTIPLE PERIOD DOUBLING BIFURCATION ROUTE TO CHAOS IN PERIODICALLY PULSED MURALI–LAKSHMANAN–CHUA (MLC) CIRCUIT

In this paper, we study the effect of additional periodic forces in Murali–Lakshmanan–Chua (MLC) circuit. We show that the additional periodic forces of pulse type display novel dynamical features including multiple period doubling bifurcation route to chaos, followed by a rich variety of dynamical phenomena including enlarged periodic windows, attractor crises, distinctly modified bifurcation structures and so on. For certain types of periodic pulses, the circuit admits transcritical bifurcations preceding the onset of multiple period doubling bifurcations. We have characterized these dynamical behaviors using Lyapunov exponents, correlation dimension, Kaplan–Yorke dimension and power spectrum, which are found to be in good agreement with the experimental observations. We have also shown that the chaotic attractor becomes more complicated and their corresponding return maps are no longer simple for large n-periodic pulses, which has immense potential applications in secure communication. The above study facilitates one to generate any desired n-period doubling bifurcation behavior by applying n-periodic pulses to a chaotic system. Further, controlling and synchronization of chaos in this periodically pulsed MLC circuit have also been achieved by using suitable methods.

Multiple period-doubling bifurcation route to chaos in periodically pulsed Murali-Lakshmanan-Chua circuit-controlling and synchronization of chaos

We consider a simple nonautonomous dissipative nonlinear electronic circuit consisting of Chua's diode as the only nonlinear element, which exhibit a typical period doubling bifurcation route to chaotic oscillations. In this paper, we show that the effect of additional periodic pulses in this Murali-Lakshmanan-Chua (MLC) circuit results in novel multiple-period-doubling bifurcation behavior, prior to the onset of chaos, by using both numerical and some experimental simulations. In the chaotic regime, this circuit exhibits a rich variety of dynamical behavior including enlarged periodic windows, attractor crises, distinctly modified bifurcation structures, and so on. For certain types of periodic pulses, this circuit also admits transcritical bifurcations preceding the onset of multiple-period-doubling bifurcations. We have characterized our numerical simulation results by using Lyapunov exponents, correlation dimension, and power spectrum, which are found to be in good agreement with the experimental observations. Further controlling and synchronization of chaos in this periodically pulsed MLC circuit have been achieved by using suitable methods. We have also shown that the chaotic attractor becomes more complicated and their corresponding return maps are no longer simple for large n-periodic pulses. The above study also indicates that one can generate any desired n-period-doubling bifurcation behavior by applying n-periodic pulses to a chaotic system.

Analysis of a modular generator for high-voltage, high-frequency pulsed applications, using low voltage semiconductors (<1kV) and series connected step-up (1:10) transformers

This article discusses the operation of a modular generator topology, which has been developed for high-frequency (kHz), high-voltage (kV) pulsed applications. The proposed generator uses individual modules, each one consisting of a pulse circuit based on a modified forward converter, which takes advantage of the required low duty cycle to operate with a low voltage clamp reset circuit for the step-up transformer. This reduces the maximum voltage on the semiconductor devices of both primary and secondary transformer sides. The secondary winding of each step-up transformer is series connected, delivering a fraction of the total voltage. Each individual pulsed module is supplied via an isolation transformer. The assembled modular laboratorial prototype, with three 5 kV modules, 800 V semiconductor switches, and 1:10 step-up transformers, has 80% efficiency, and is capable of delivering, into resistive loads, -15 kV1 A pulses with 5 micros width, 10 kHz repetition rate, with less than 1 micros pulse rise time. Experimental results for resistive loads are presented and discussed.

Circuit dependence of the diameter of pulsed positive streamers in air

The diameter and branching structure of positive streamers in ambient air are investigated with a fast iCCD camera. We use different pulsed power circuits and find that they generate different spatial streamer structures. The electrodes have a point-plane geometry and a distance of 40 or 80 mm, and the peak voltages over the discharge gap are up to 60 kV. Depending on circuit and peak voltage, we observe streamers with diameters varying gradually between 0.2 and 2.5 mm. The streamer velocity increases with the diameter, ranging from 0.07 to 1.5 mm ns−1, while the current density within the streamers stays almost constant. The thicker streamers extend much further before they branch than the thinner ones. The pulsed power supplies are a switched capacitor supply with an internal resistance of 1 kΩ and a transmission line transformer supply with an impedance of 200 Ω; additional resistors change the impedance as well as the voltage rise time in the case of the capacitor supply. We observe that short rise times and low impedance create thick streamers close to the pointed electrode, while a longer rise time as well as a higher impedance create thinner streamers at the same peak voltage over the discharge.

Development of single frame X-ray framing camera for pulsed plasma experiments

A single-frame X-ray framing camera has been set up for fast imaging of X-ray emissions from pulsed plasma sources. It consists of two parts, viz. an X-ray pin-hole camera using an open-ended microchannel plate (MCP) detector coupled to a CCD camera, and a high voltage short duration gate pulse for the MCP. The camera uses a 10-Μm pin-hole aperture for imaging on the MCP detector with a magnification of 6 X. The high voltage pulser circuit generates a pulse of variable duration from 5 to 30 ns (at 70% of peak amplitude) with variable amplitude from 800 V to 1.25 kV, and is triggered through a laser pulse synchronized with the event to be recorded. The performance of the system has been checked by recording X-ray emission from a laser-produced copper plasma. A reduction factor of ∼ 6.5 is seen in the dark current contribution as the MCP gate pulse is decreased from 250Μs to 5 ns duration.

Gated x-ray detector for the National Ignition Facility

Two new gated x-ray imaging cameras have recently been designed, constructed, and delivered to the National Ignition Facility in Livermore, CA. These gated x-Ray detectors are each designed to fit within an aluminum airbox with a large capacity cooling plane and are fitted with an array of environmental housekeeping sensors. These instruments are significantly different from earlier generations of gated x-ray images due, in part, to an innovative impedance matching scheme, advanced phosphor screens, pulsed phosphor circuits, precision assembly fixturing, unique system monitoring, and complete remote computer control. Preliminary characterization has shown repeatable uniformity between imaging strips, improved spatial resolution, and no detectable impedance reflections.

Magnetic memory and current amplification devices using moving domain walls

A moving magnetic domain wall produces an electromotive force (emf). It is therefore possible to read the state of a magnetic memory device via the emf it produces when subjected to an interrogation pulse. It is also possible to amplify currents in pulse circuits, opening up the possibility of all magnetic logic circuits.

Multiple-gap spark gap switch

A triggered multiple-gap spark gap switch has been developed and tested under atmosphere. By means of an LCR trigger circuit, the multiple-gap switch can be used very reliably. For the same switching voltage (35.5kV), with increasing the number of gaps from 2 to 6, the switching current rise time is reduced from 13.5to6ns, and the energy efficiency is increased from 87% to 92%. An eight-gap switch was also tested, and the switching current rise time is much smaller than the usable rise time of the current probe (3.5ns). One interesting application of the multiple-gap switch is to improve the switching performance in the multiple-switch and transmission lines based pulsed power circuit. To verify this application, a six-gap switch was tested. In contrast to a single-gap switch, the output current rise time was improved from 21to11ns by the six-gap switch.

Novel pulse calorimetry taking nonuniform temperature distribution into account

A novel method for measuring the specific heat capacity by pulse heating has been developed to avoid the uncertainty due to nonuniform temperature distribution across a whole effective sample during the cooling period. This method restricts determining the heat capacity to the value corresponding to the peak temperature of the sample and uses the sample itself as a resistance thermometer to measure the effective temperature of the cooling sample. To measure the resistance of the cooling sample, a low current is applied to the sample even during the cooling by using field-effect transistors as the switching device of the pulse circuit. The specific heat capacity and electrical resistivity of molybdenum at temperatures above 1700K have been measured. Electrical resistivity measurements can also be corrected by a simple uncertainty estimation that involves comparing the resistivities measured at the end of heating and at the beginning of cooling, a further advantage of this method.

Ultrasound methods and implantable medical devices using same

An ultrasound method and medical devices using same provide for various techniques of sampling blood flow velocity, e.g., at several sampling rates. To minimize the energy required for ultrasound monitoring, pulsed Doppler signal packages provided by a pulsed ultrasound circuit are switched in such a way that the repetition rate is the lowest possible and yet sufficiently high to be able to record the blood flow velocity within the heart. For example, an ultrasound circuit may be activated only within a part of the cardiac cycle designated as the Doppler Measurement Interval (DMI); the ultrasound circuit may be switched between an on state and an off state during the DMI; and/or the ultrasound circuit may also be switched on and off in different sampling modes: detection mode and measurement mode (e.g., using different sampling rates).

Quench and recovery behaviors of Bi-2223/Ag HTS tapes under pulsed over-currents with different durations

Under pulsed over-currents with different durations, quench and recovery behaviors of Bi-2223/Ag HTS tapes have been observed. The experiment is carried out using a pulsed circuit. The HTS tapes are immersed in liquid nitrogen bath. The durations of the pulsed currents fed to HTS tapes are 2.78 ms, 1.97 ms, 1.58 ms, 1.22 ms, 1.11 ms and 0.91 ms, respectively. In order to confirm the critical current of the tapes, DC current is fed to the tapes firstly. The magnitude of the pulsed currents is about 100 A, which is about three times of the critical current of the tapes. The experimental result shows that the normal voltage generated by the over-current disappears fast after the end of the pulsed over-current. As the duration of the pulsed current decreases, the quench and recovery current tends to increase, and larger than the critical current of the tapes, which show that HTS tape has a good superconducting-to-normal conducting recovery characteristic under pulsed current with short duration. These results show that the application of HTS tapes for future pulsed power would be very promising.

Microstructure and tribological behaviour of super-hard Ti–Si–C–N nanocomposite coatings deposited by plasma enhanced chemical vapour deposition

In this study, a series of new quaternary Ti–Si–C–N nanocomposite coatings have been deposited on HSS substrate at 550 °C using an industrial set-up of pulsed direct circuit plasma enhanced chemical vapour deposition (PECVD) equipment with a gas mixture of TiCl 4/SiCl 4/H 2/N 2/CH 4/Ar. The composition of the coatings can be controlled through the adjustment of CH 4 flow rate and the mixing ratio of the chlorides. Detailed structural and chemical characterisations using transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) suggest the formation of a Ti (C, N)/a-C/a-Si 3N 4 nanocomposite structure. Ti (C, N) films show a (200) texture, which change to random orientation of the crystallites when the silicon content reaches about 9 at.%. The tribological behaviour of these coatings was investigated at room and elevated temperature. The results show that the nanocomposite Ti–Si–C–N coatings with low Si and high C contents have a lower friction coefficient of 0.17–0.35 at room temperature. The Ti–Si–C–N nanocomposite coating containing 12 at.% Si and 30 at.% C shows excellent tribological properties with a low friction coefficient of 0.30 and a low wear rate of 4.5 × 10 5 mm 3 N − 1 m − 1 at 550 °C.

Rotational motion of microsphere packs on acoustically excited surfaces

The generation of uniform rotational motion of polystyrene latex microsphere packs on silicon oxide dry surfaces in base-excited acoustic fields is demonstrated. The physics of microparticle dynamics on surfaces is substantially different from its counterparts in meso/macroscale due to the domination of intermolecular forces in microscale objects. The stability of packs presented in the current experimental study suggests that rolling resistance due to elasticity and adhesion plays an essential role in pack formation. The control of the rotational speed of microspheres with the pulse repetitive frequency of the pulser circuit is illustrated. The present work could lead to a motion excitation mechanism for microscale systems.

Solid-state ultra-wideband pulse generator: Application in bioeffect research

This article describes the design and characterization of an ultra-wideband (UWB) pulse generator suitable for biomedical research. The pulser generates nanosecond-long electromagnetic pulses of adjustable rise time, amplitude, and duration, permitting analysis of possible bioeffects over a range of pulse characteristics. Nanosecond rise-time pulses (2.4 ns) of 3.4 kV are achieved in a four-stage pulser circuit using ZTX415 transistors. This device has been used to assess exposure bioeffects to UWB pulses of the model system E. coli.