Parallel Marx Generator Stray Capacitance Reduction
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Solution Overview
Problem
Conventional Marx generators face limitations due to stray capacitance, which affects the rise and fall times of voltage pulses and limits the number of sections that can be stacked, and often require non-compliant high-power technology for substantial pulse outputs.
Innovation Solution
The system employs series voltage cells with capacitors and solid-state switches, eliminating inductors, resistors, and isolated supplies to reduce stray capacitance, allowing for more cells to be connected in series, and includes balance networks to match stray capacitance across cells, enabling control over pulse amplitude, duration, rise and fall times, and droop correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the number of sections in the pulse forming network is increased to generate higher voltage pulses, then the voltage magnitude is improved, but the stray capacitance to ground increases causing parasitic current diversion and degrading rise time and fall time
Solution Approach 1:
The system divides the pulse forming network into multiple independent voltage cells (e.g., 4 cells of 100 pF each) that can be connected in series. Each cell is charged in parallel independently and then discharged in series to generate the high voltage pulse. This segmentation allows achieving high voltage (400V peak) while maintaining controlled impedance characteristics and reducing the impact of stray capacitance on pulse shape.
Solution Approach 2:
The system changes the capacitance value parameter of each voltage cell to optimize performance. By using 100 pF capacitors with specific ESR (equivalent series resistance) values and controlling the charging voltage (50V per cell), the system achieves the desired voltage magnitude while maintaining rise time and fall time within acceptable limits (rise time < 100 ns, fall time < 100 ns).
2Power
If more voltage cells are stacked in series to generate higher voltage pulses, then the voltage magnitude is improved, but the stray capacitance imbalance across sections increases causing voltage transients and malfunction
Solution Approach 1:
The system applies local quality by making each voltage cell identical in terms of capacitance value (100 pF), ESR, and physical layout. This ensures that each cell has the same stray capacitance to ground, creating balanced conditions across all sections. The identical configuration of switching devices (IGBTs, diodes, resistors) in each cell further ensures uniform voltage distribution and prevents voltage transients during charging and discharging operations.
3Productivity
If conventional components (inductors, resistors, transformers, isolated supplies) are used to charge capacitors in the pulse generator, then the charging function is achieved, but additional stray capacitance is introduced reducing the number of stages that can be connected
Solution Approach 1:
The system extracts and removes traditional charging circuit components such as inductors, resistors, transformers, and isolated supplies from the voltage cell design. Instead, it uses a simplified charging circuit consisting of a DC voltage source, a charging switch (IGBT with anti-parallel diode), and a current-limiting resistor. This extraction of unnecessary components significantly reduces stray capacitance to ground, enabling more voltage cells to be stacked in series while maintaining pulse quality.
Solution Approach 2:
The system replaces traditional electromagnetic charging mechanisms (inductors and transformers) with solid-state electronic switching (IGBTs and diodes). This substitution eliminates the stray capacitance associated with magnetic components and enables a more compact, lower-capacitance charging circuit that allows for greater numbers of voltage cells to be connected in series.
4Power
If high-power technology is used to generate substantial pulse outputs, then the power output is improved, but compliance with export and import regulations becomes difficult achieving commercial feasibility
Solution Approach 1:
The system segments the high-power pulse generation into multiple lower-power voltage cells (e.g., 4 cells each operating at 50V charging voltage). Each cell uses commercially available, regulation-compliant components. The high power output (400V peak) is achieved by connecting these compliant cells in series during discharge, allowing the system to meet regulatory requirements while still delivering substantial pulse power.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration reduces stray capacitance, enables more voltage cells to be stacked, lowers the required voltage source, and allows for cost and size reduction of pulse generators, while maintaining compliance with export and import regulations by using commercially available components.
Implementation Method 1
a pulse generator that includes a plurality of voltage cells, each voltage cell including a capacitor
Data Source
Figure 1~2
Figure 3A
Figure 3B
AI summary
A parallel Marx generator topology capable of producing high power, high current output pulses is provided. The parallel Marx generator topology can include a plurality of Marx generators that operate in parallel to one another to jointly generate an output pulse. The topology can further include a pulse transformer configured to step up the voltage of the pulse created by the plurality of generateors and also ensure that each Marx generator of the plurality of Marx generators is ouputting substanitially the same amount of current. The system can include a common interface that allows for fault detection and control of all the Marx generators using one common control panel. The parallel Marx generator topology can allow for a high voltage, high current pulse to be generated using import/export compliant switches.