Marx Bank Circuit Research Articles

Leakage current induced erratic switching in Si avalanche bipolar junction transistors under overvoltage states

Due to the erratic switching phenomenon of the Si avalanche bipolar junction transistor (ABJT) in the Marx bank circuit (MBC), an explanation of the leakage current trigger mode in the overvoltage state with a lack of displacement current is proposed. There are random switching properties (i.e., switching or non-switching) in the ABJT with emitter–base shorted, triggered by a voltage ramp to the overvoltage state temporarily with dV/dt rate close to 0 V/ns. The experimental conditions and characteristics of erratic behaviors are summarized. The optical visualization of the current channel in an erratic switching state is obtained, and the corresponding physical model of the leakage current trigger mode is established. It shows that the switching event occurs with the change in the position of the conductive channel. The process of emitter electron injection is caused by the leakage current in the overvoltage state instead of the displacement current. Meanwhile, the intensity of this trigger mode is weak, and the instability of the leakage current may cause the failure of switching. The study of erratic switching is of great significance for the working reliability of MBCs and failure analysis of ABJTs. The proposed explanation is validated by the agreement between the simulation results and the experimental observations.

High voltage nanosecond pulse generator based on avalanche transistor Marx bank circuit and linear transformer driver.

Avalanche transistor Marx bank circuits (MBCs) are widely used in high voltage repetitive nanosecond pulse generators, but problems exist with respect to increasing the output voltage due to the limited pulsed current. Accordingly, a novel topology based on an avalanche transistor MBC combined with a linear transformer driver is proposed, the latter of which exhibits advantageous stress distribution and modular structure. A four-module prototype with four units in each module is developed in the laboratory. The output characteristics are investigated by varying important parameters such as the main capacitance, the number of conducting units, the number of cascaded modules, and the trigger signal time delay. The test results verify the validity of the proposed topology. For a 50 Ω resistive load, the prototype can generate pulses with an amplitude of 10.9 kV, a rise time of 3.3ns, and a voltage superposition efficiency of 89%. The topology proposed in this paper may help to provide a method to further improve the output performance of avalanche transistor MBCs.

Development of a High Peak Voltage Picoseconds Avalanche Transistor Based Marx Bank Circuit

Avalanche transistor-based Marx bank circuit (MBC) is widely used to generate high voltage nanosecond pulses with high amplitude, high repetition rate, fast rise time, and low jitter. Researchers have tried to modify the circuit structure by using parallel or series avalanche transistors to increase peak power. However, in this work, the detailed process of analyzing and designing a compact Marx generator using avalanche transistors will be described. The purpose of this article is to report our experimental observations on the mechanism of operation of the MBCs. By studying the influence of amplitude and pulse width of the trigger circuit, a Gaussian pulse with a rising edge of 160 ps, full width at half maximum (FWHM) of 660 ps, and amplitude of 5000 V are obtained. The design improves the output voltage and pulse repetition frequency (PRF) effectively while reducing the use of the number of transistors. Based on the conventional principles of avalanche transistors and Marx circuit, a list of useful and interesting conclusions obtained from experiments will be reported.

Further Investigations on a Modified Avalanche Transistor-Based Marx Bank Circuit

Avalanche transistor-based Marx bank circuit (MBC) is widely used to generate nanosecond pulses with high amplitude, high repetition rate, fast rise time, and low jitter. Recently, the problem that avalanche transistors in the first several stages of $M \times N$ -stage MBC fail frequently has been alleviated by adopting auxiliary triggering topology (ATT). However, the reasons for improvement and the optimal design method have not been fully understood. In this article, a flexible $4\,\,\times10$ -stage MBC is developed to further investigate the output characteristics under different modified stages, capacitors, and loads through both experiments and simulations. The results show that on the one hand, adopting ATT will cause energy loss of the main capacitors to auxiliary triggering capacitors, which can decrease the output voltage; and on the other hand, transistors operating in the auxiliary triggering switching-ON mode have lower residual voltage than in the lower overvoltage switching-ON mode, which can increase the output voltage. This implies that there exists an optimal value of modified stages, which is 5 for the $4\,\,\times10$ -stage MBC. Besides, by adopting ATT, the waveform of output pulse changes, and the rising edge becomes faster. Finally, a repetitive nanosecond pulse generator is developed based on the optimized parameters, which can produce pulses with an amplitude of 9.04 kV, a rise time of 3.4 ns, a pulse width of 18.8 ns, and a maximum repetition rate of 1 kHz at the 75- $\Omega $ open-ended cable. Also, the feasibility of this modified MBC is validated by the preliminary experiments of driving atmospheric pressure plasma jet (APPJ).

High-voltage Pulse Generation Using Electrostatic Induction in Capacitor

Pulse power sources can produce high temperature or high-density extreme conditions within a short time. They have been introduced to various fields such as those in laser, fusion research, the production of plasma, shockwaves in water, water treatment, and exhaust gas treatments. Various high voltage pulse sources using insulated-gate bipolar transistor (IGBT) semiconductors with high voltage resistivity have been used. Also, Marx bank circuit is well known as an instrument that produces voltage pulses with low repetitive rates. These instruments have several advantages. However, their problems are a complex structure, high cost, and excessive weight. A simple method of producing high voltage pulses with short rising times based on electrostatic induction in external capacitor used for pulse power applications is proposed. The circuit has a simple structure and contains a minimum number of parts, which makes the instrument small and light weight. In fact, the generation of sawtoothed high voltage pulses with short rising times and low repetitive rates of a few 100 Hz was successfully conducted in experiments. Theoretical analysis was simultaneously undertaken. The numerically calculated results for generating high voltage pulses were goodly consistent with the experimental ones. Moreover, it has been confirmed that amplification of the output voltage by electro-hydrodynamics (EHD) electricity generation using a jet flame resulted in higher voltage pulses, lower electricity consumption, and high repetition rates.

A compact, low cost Marx bank for generating capillary discharge plasmas.

We describe in detail a low power Compact Marx Bank (CMB) circuit that can provide 20 kV, 500 A pulses of approximately 100-200 ns duration. One application is the generation of capillary discharge plasmas of density ≈1018 cm-3 used in laser plasma accelerators. The CMB is triggered with a high speed solid state switch and gives a high voltage output pulse with a ns scale rise time into a 50 Ω load (coaxial cable) with <4 ns voltage jitter. Its small size (10 cm × 25 cm × 5 cm) means that it can be placed right next to the capillary discharge in the target chamber to avoid the need to impedance match. The electrical energy required per discharge is <1 J, and the CMB can be run at shot repetition rates of ≳1 Hz. This low power requirement means that the circuit can easily be powered by a small lead acid battery and, therefore, can be floated relative to laboratory earth. The CMB is readily scalable and pulses >45 kV are demonstrated in air discharges.

Reliable Self-Starting Simmer Circuit for a Marx-Bank Driver

A reliable self-starting simmer circuit for use as a Marx-bank driver, in which a stable glow discharge is obtained using the high voltage main power supply instead of an additional simmer power supply, is presented. Highly energetic excitation sources having very short pulse width are needed in powerful dye and excimer lasers. For this reason, multi-stage Marx-bank circuit and LC inversion circuits have been developed. However, these circuits have defects in the interference between the main discharge circuit and the pre-ionization circuit, and an occasional switching failure of the spark gap switch, resulting in an unstable main discharge. The circuit presented seeks to address these issues.

Breakdown of transistors in Marx bank circuit

We reconsider the mode of operation of a Marx bank circuit and analyze the secondary breakdown of transistors with shorted emitter-base. The mechanism of breakdown of the transistor when a fast rising voltage pulse is applied across is investigated. The device exhibits chaotic behavior at the breakdown point where it can go into two possible modes of breakdown. A new explanation for the working of the circuit consistent with the experimental observations is proposed.

Nonuniform doping of the collector in avalanche transistors to improve the performance of Marx bank circuits

It is shown that the avalanche multiplication factor of transistors, which plays a key role in the functioning of the Marx bank circuit, can be considerably enhanced when the collector has a Gaussian doping profile, compared to uniform doping. The limiting of the maximum field in the collector, and the base push out are the events involved in the occurrence of the current mode second breakdown of avalanche transitors in the Marx circuit. Calculations show that the limiting of the maximum field, followed by the base push out, is the sequence conducive to the enhancement of the avalanche gain. Preliminary experimental assessment of the doping profiles of the same model of transistors from two different manufacturers supports the proposed idea.

The principle of operation of the avalanche transistor-based Marx bank circuit: A new perspective

The principle of operation of the transistor-based Marx bank circuit has been examined. It was experimentally observed that stage-wise increase of reverse voltage does not occur. This cannot be explained by the principle of operation understood so far. A new explanation, consistent with the experimental observations and associating current-mode second breakdown of transistors, is proposed. A few experimental observations made by earlier workers have also been justified in light of the new current-controlled mechanism.

A 110 J Highly Energetic Flashlamp-Pumped Dye Laser

A highly energetic flashlamp-pumped dye laser of 110 J output energy and overall efficiency of 1.1% is developed. For such a powerful laser particular considerations must be taken in order to reduce thermal distortion in the dye solution caused by high-energy pumping. The laser system is therefore composed of a laser head with a four-fold elliptical cylindrical reflector, extended Marx-bank driver circuit, a large aperture dye cell of 44 mm inner diameter and an unstable resonator.

A transistorized Marx bank circuit providing sub-nanosecond high-voltage pulses

An improved version of a Marx bank circuit has been developed using 2N5551/2N5550 transistors as switching elements in avalanche mode which provides a negative pulse of about 4 kV amplitude and <or=ns rise time. The circuit has about 14 ns delay and <or=ns jitter.

Applying the Marx bank circuit configuration to power MOSFETs

Power MOSFETs operated in a Marx bank circuit configuration are presented. This circuit is useful for generating high voltage (greater than 1 kV) nanosecond risetime pulses. After the design procedure is given an example circuit is designed which generates a -1800 V pulse with a 3-0 ns falltime into 50 Ω

A fast cavity dumper for a picosecond glass laser

A fast cavity dumper for picosecond glass laser has been made. The optical and electrical characterization of the cavity dumper is described. An avalanche transistor Marx bank generator drives the cavity dumper. Up to 5 kV peak amplitude and 1.5 ns fall time negative polarity step pulses are generated by the Marx bank circuit. With a capacitive load like Pockels cell the pulse fall time increases to 4 ns. Optical switching times as fast as 2 ns (10%–90%) are experimentally measured. The contrast ratio of 1000 is obtained after a double pass through an amplifier. Single picosecond pulses are produced with an energy jitter of 10%.

Coaxial Marx-Bank Driver and Flashlamp for Optical Excitation of Organic Dye Lasers

A flashlamp pumped laser system that utilizes a coaxial Marx-Bank driver circuit is described. The property of the Marx-Bank circuit, which is to charge storage capacitors in parallel but discharge them in series connection, affords the practical advantage that high applied voltages and flashlamp input energies may be attained with a relatively low dc charging voltage. The use of a coaxial flashlamp and circuit configuration minimizes total inductance so that short duration, high energy pulses efficient for dye laser excitation are obtained.

Etude d'un generateur d'impulsions tres haute tension (quelques kV) utilisant des transistors en regime d'avalanche

This paper describes a high voltage pulse generator using 18 avalanche transistors in a modified Marx bank circuit. For input pulses of about 500 mV this generator yields output pulse amplitudes of 1.7 kV, a delay of 7 ns and a rise time better than 3 ns. An analysis of the performances is given.