Pulse Circuit Research Articles

A portable time-domain LED fluorimeter for nanosecond fluorescence lifetime measurements.

Fluorescence lifetime measurements are becoming increasingly important in chemical and biological research. Time-domain lifetime measurements offer fluorescence multiplexing and improved handling of interferers compared with the frequency-domain technique. In this paper, an all solid-state, filterless, and highly portable light-emitting-diode based time-domain fluorimeter (LED TDF) is reported for the measurement of nanosecond fluorescence lifetimes. LED based excitation provides more wavelengths options compared to laser diode based excitation, but the excitation is less effective due to the uncollimated beam, less optical power, and longer latency in state transition. Pulse triggering and pre-bias techniques were implemented in our LED TDF to improve the peak optical power to over 100 mW. The proposed pulsing circuit achieved an excitation light fall time of less than 2 ns. Electrical resetting technique realized a time-gated photo-detector to remove the interference of the excitation light with fluorescence. These techniques allow the LED fluorimeter to accurately measure the fluorescence lifetime of fluorescein down to concentration of 0.5 μM. In addition, all filters required in traditional instruments are eliminated for the non-attenuated excitation/emission light power. These achievements make the reported device attractive to biochemical laboratories seeking for highly portable lifetime detection devices for developing sensors based on fluorescence lifetime changes. The device was initially validated by measuring the lifetimes of three commercial fluorophores and comparing them with reported lifetime data. It was subsequently used to characterize a ZnSe quantum dot based DNA sensor.

Custom integrated circuit design for ultrasonic therapeutic CMUT array

This paper presents the design of a highly flexible and programmable transmit beam-former ASIC using a high voltage (HV) 0.35 μm CMOS technology to be flip-chip bonded to a 4 × 4 CMUT array for ultrasound therapeutic applications. However, proposed IC can be used as a transmitter circuitry in color Doppler 3D imaging applications. In our proposed chip, each CMUT element is provided by an 8-bit shift register, an 8-bit comparator, a one-shot circuit with adjustable pulse width, a programmable pulse train generator and a HV pulser circuit. The interface electronics can generate two types of outputs with programmable focusing delays to 16 ultrasound transducer elements in different modes: The first mode is for generating single pulses in which the one-shot circuits adjust the width of the pulses from a few nanoseconds to 650 ns with enough resolution for different operating frequencies of ultrasound transducer. The second one has been considered for generating controllable pulse trains with output frequencies in the range of 1---10 MHz. At final stage the amplitudes of single pulses or pulse trains are increased up to 45 V using HV pulsers. Using an external control system like FPGA, the pulser circuit fires correspondent CMUT element when its stored shift register value is identical with the value of global counter.

Quantitative Characterization of the Liquid Crystal Doped With Nanoscaled Tin-Doped Indium Oxide Under High Electric Fields

In this paper, a pulse circuit was designed to simulate the source of an electrostatic discharge (ESD). This high-voltage source was successfully used in ESD tests to precisely control the voltage exerted on the liquid crystal (LC) cells. In addition, the characteristics of the samples under ESD were measured by a more precise pulse source. According to the measurement of the relaxation of the sticking images, the behavior of the tin-doped indium oxide (ITO) nanoparticles in the LC was investigated in detail. It was confirmed that the amount of ITO may affect the speed of releasing high-voltage charges after the attack of ESD. In addition, we tried to estimate the resistivity and density of the conductive ITO bridges.

A solid-state generator with pulsed excitation of the oscillating circuit

A solid-state high-frequency damping oscillation pulse generator based on a pulsed excitation circuit is designed. The frequency of high-frequency oscillations reaches units of megahertz with a pulse repetition rate in the continuous mode of up to 1 kHz. The frequency of output pulses determines the power consumption from the supply mains that does not exceed 700 W. In this case, the peak power of output pulses reaches hundreds of kilowatts with a generator efficiency of up to 65%, if the optimal resistive load is used. The main area of the generator application is the generation of low-temperature atmospheric-pressure plasma.

Identification and ranging of reservoir boundary in horizontal wells geosteering

Abstract To make quantitative measurement of the distance between the drilling tool and the reservoir boundary in horizontal well drilling, this paper presented the method of “layer-detection ranging”, established the physical and mathematic models and designed the circuit supporting the method. Moreover, the simulation experiment was made to verify the method's feasibility. With the method, the reservoir boundary was detected and the distance between it and the drilling tool was measured through transmitting directional high-frequency electromagnetic waves and receiving reflection waves, in process of measurement while drilling (MWD) in the horizontal well drilling. Two “layer-detection ranging” circuits, i.e. high-voltage narrow pulse and single frequency modulating pulse, were designed. Based on the circuit theory, a “layer-detection ranging” system was established and three media were used for simulation experiment. The results show that: more details of the reservoir are acquired from received waveforms using the high-voltage narrow pulse circuit, and the received waveforms are more easily identified and discriminated using the single frequency modulating pulse circuit; under the conditions of different media and distances, the relative error between the true distance and the distance measured with the “layer-detection ranging” method is less than 5%, suggesting that the method is reliable.

Design and Study on Efficient Triggering Circuit for Reversely Switched Dynistor

The main characteristics of reversely switched dynistor (RSD) are infinite series, long lifetime, turning on in microseconds to nanoseconds, high-current rise rate (100 kA/μs), and ability of passing through large current (several kiloamperes). With these advantages, RSD has a great potential of application in repetition rate pulsed power technology and the future HVdc field. To resolve the problem of residual voltage of RSD caused by insufficient precharge, which leads to nonuniform turn-on of RSD, this paper, based on the conduction mechanism of RSD devices, describes precharge circuit design requirements and establishes a second order circuit model to study the resonant triggering circuit of RSD. It is found that reducing precharge inductor can effectively increase precharge current, resulting in reducing the turn-on voltage of RSD. Finally, design for three improved circuit topologies (full-bridge, intense pulsed, and two-step triggering circuit) are presented and experiments show that these improved circuit topologies can enhance the precharge efficiency and reduce the turn-on voltage of RSD.

A design of negative high voltage nanosecond pulse circuit

A design of negative high voltage nanosecond pulse circuit

Математическая модель силовой схемы главных электроприводов прокатных станов

A mathematical model of the power circuit of the main electric drive of cold rolling mill 2.0 m is described. Mathematical model includes a transformer and an active rectifier. A distinctive feature of the power circuit the main drive is to use a transformer with a serial connection of primary windings. To implement the twelve pulse circuit the secondary windings of transformers have different groups of connections. The algorithm for generating the input voltage of the active rectifier is made on the model by comparing the switching angles with the reference signal increases linearly over the period of the supply voltage. Switching angles are calculated based on the method of pulse-width modulation with the selective harmonic elimination. Active rectifier model allows obtaining the phase voltages at the input capacitors relative zero point and calculating the primary currents of transformers, which is due to the difference in the flow network and EMF voltage at the input of the active rectifier. The simulation results are used to assess the electromagnetic compatibility powerful active rectifiers with supply mains and select transistors switching angles to minimize THD voltage.

Efficiency Study of a 2.2 kV, 1 ns, 1 MHz Pulsed Power Generator Based on a Drift-Step-Recovery Diode

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.

Design and Simulation of the Avalanche Transistor Pulse Generator

Ultra-wideband wireless communication technology is brought, in the coal mine communications in this paper in order to raising the safe level of communication in coal mine. Ultra-wideband wireless communication is a system which is transmitted by the extremely narrow pulse transmission. An avalanche transistor is the core of extremely narrow pulse circuit. Narrow pulse wave form can be simulated by multisim software. Acquiring the results of simulation is the extremely narrow pulse whose pulse amplitude ranging from 10 v to dozens v and pulse width is about 3 seconds. In addition to this circuit carries on the theoretical analysis, the results is quite consistent with the simulation value in this paper.

Development of a Pulsed DC Power Supply for Generating Cold Plasma Jet

This paper discusses a lithium battery-driven cold plasma jet at atmospheric pressure with a pulsed power supply of design and its simulation. H.V. DC(High voltage directed current) and pulsed discharge circuit comprise of the entire pulse power system. H.V. DC circuit using TIs TMS320F28335 chips as the core of the circuit control module, the chip improves the stability of the H.V.DC circuits. Pulsed discharge circuit design plays a crucial impact on the formation of the narrowed pulses. A new double pulsed discharge circuit is designed by the proposed program. As discharge experiment shown finally, the steep narrowed pulse of pulsed power supply can be used to stabilize the output of the pulsed front.

Electromagnetic coupling through apertures and shielding effectiveness of a metallic enclosure housing electro-optic pockels cell in a high power laser system

This paper presents mathematical analysis and measurement results of electromagnetic couplings through a pair of intentional apertures in a metallic enclosure and its effect on the electromagnetic shielding effectiveness. The enclosure houses an electro-optical device (Pockles cell) and its high voltage drive circuitry. Two different aperture shapes i.e. rectangular and circular of equal areas are compared over frequency range of 200 MHz to 2 GHz. Pockels cells are commonly used in applications involving fast switching of polarization to block or transmit laser light. Pockels cell assemblies are housed in metallic enclosures to reduce noise emissions from high voltage pulser circuits driving the cell and to minimize the field couplings from external sources which may result into spurious switching of the cell. However, apertures are required in the enclosure to enable the laser beam to be incident on the Pockels cell and for onward transmission of the modulated beam. The apertures result into reduced shielding effectiveness of the metallic enclosure and increase in noise couplings. There is a need to understand the effect of apertures and to properly select their shapes and sizes such that the electromagnetic noise couplings are kept to a minimum acceptable level. Apart from the functional requirements of a reliable and noise free system operation, this issue is also important to meet the growing and stringent demands of electromagnetic compatibility. The analysis and measurements presented in this work pertain to the noise couplings from an external source into the enclosure through two differently shaped apertures i.e. rectangular and circular. For the comparison purpose, the planar areas of the apertures for the two cases are kept equal. The analysis and measurement techniques described in this work will be of interest to designers of electrical and electro-optical components for laser systems.

激光电源脉冲功率切换电路仿真分析

激光电源脉冲功率切换电路仿真分析

Design of Vehicle Taillight Circuit with Mechanical Properties in Mechanical Engineering

The vehicle taillights control circuit with mechanical properties is composed of a clock pulse circuit, a switch control circuit, three hexadecimal circuit, decoding and display drive circuit, taillight display. The circuit is simulated with Multisim. The simulation results show that vehicle taillight display can make pedestrians and other vehicles understand clearly the occurrence of the vehicle’s dynamic change, thus which can prevent the occurrence of traffic accidents effectively.

高重复频率脉冲功率技术及其应用:(4)半导体开关的特长与局限性

Power semiconductor devices have been used for repetitive pulsed power generation, due to their advantages in stability, reliability, and lifetime. On the other hand, their limitations in power capability and noise vulnerability are expected to be overcome by using various techniques in gate control and circuit configuration. In this paper, some pulse circuit methods to improve the working ability of semiconductor switches are introduced, including using a number of devices in series and parallel, voltage superposition, combination and complementation of switching devices.

Hardware Design of a New Instrument to Control the Heat Pulse and Measure the Temperature of Stratum

In this work, we report the design of a new instrument including one heat pulse circuit and three temperature measure circuits. Heat pulse control circuit can control the heating time of heater strip. The heating power is 0.5W and the duty time of every heat pulse is 8s. Three temperature measure circuits can measure the change of stratum’s temperature before and after accurately. The temperature resolution is 0.001°C, precision is 0.01°C and sampling rate is 1 Hz. The instrument can save the temperature data for every measure process. It is also provided with the data communication interface. The data saved in the instrument can export to computer through the interface. The instrument can measure the stratum’s temperature easily and reliably. The instrument will play a role in the studies of hydrogeology and environmental geology besides the application of Shallow Geothermal heat

Schmitt Trigger with Controllable Hysteresis Using Current Conveyors

Active elements working in the current or mixed mode are still attractive for the design of analog functional blocks. The current conveyor (CC) was defined already in 1968. This paper deals with hysteresis comparators using second generation current conveyor. The comparator is basically a pulse circuit. In these circuits, the maximum rate of change in the output voltage is required during switching from one state to another. In comparators with operational amplifiers the switching time is given by the slew rate of the operational amplifier used, which is not too high. If a current conveyor is used, the time of switching the comparator gets shorter. The comparator is capable to operate at a higher frequency bands and if it is used, for example, in converters, a higher operating frequency can be reached. The connection of an inverting and a non-inverting comparator with adjustable hysteresis is shown as a practical implementation. Using the AD844, results of experimental measurements are presented that confirm the theoretical assumptions and the results of computer simulation.

Short Pulse Generation With On-Chip Pulse-Forming Lines

We report our results on pulse-forming-line (PFL)-based CMOS pulse generator studies. Through simulations, we clarify the effects of PFL length, switch speed, and switch resistance on the output pulses. We model and analyze CMOS pulse generators with on-chip transmission lines (TLs) as PFLs and CMOS transistors as switches. In a 0.13- μm CMOS process with a 500- μm long PFL, post-layout simulations show that pulses of 10.4-ps width can be obtained. High-voltage and high-power outputs can be generated with other pulsed power circuits, such as Blumlein PFLs with stacked MOSFET switches. Thus, the PFL circuit significantly extends short and high-power pulse generation capabilities of CMOS technologies. A CMOS circuit with a 4-mm-long PFL is implemented in the commercial 0.13- μm technology. Pulses of ~116-ps duration and 205-300-mV amplitude on a 50-Ω load are obtained when the power supply is tuned from 1.2 to 1.6 V. Measurement connection setup is the main reason for the discrepancies among measurements, modeling, and simulation analyses.

Design on Ultra Wide Band Pulse Waveform

Abstract It is found that design on Pulse signal waveform plays an important role in the Ultra Wide Band (UWB) communication system. Since design on ordinary pulse waveform can not take into account the constrain conditions of UWB both in time domain and frequency domain, there is poor application in practice. Therefore, UWB pulse transmitting circuit is designed based on analysis of ordinary Gaussian pulse circuit. Firstly, ordinary Gaussian pulse circuit is improved by adding attenuation network and high-pass filter; then main parameters of pulse transmitting circuit are optimized by using particle swarm optimization (PSO) algorithm so that output waveform can meet standard of UWB waveform design. Simulation experiment and interference test show that various performance indexes of pulse waveform meet technical requirements of UWB system.

Electrothermal theory approach for numerical approximation of the μ-EDM process

A fundamental study of microelectric discharge machining (μ-EDM) based on the physics of single spark and electrothermal theory has been carried out. The machining phenomena in the μ-EDM process are investigated through simulations using finite element method. By creating the single-discharge crater, the topography is measured using an atomic force microscope and the simulation results compared with the experimental result. A temperature distribution along the radius and depth of the workpiece is thus reported. For verification purpose, single-discharge experiments with RC pulse circuit are performed with tungsten carbide as the electrode and stainless steel as the workpiece. The diameter-to-depth ratios of the crater obtained by the simulation and the experiments are 2.92 and 2.67, respectively. The simulation results are found to be in close agreement with experimental results.