Compenstation scheme for the voltage droop of solid-state marx modulators
a solid-state marx modulator and compensation circuit technology, applied in pulse generators, pulse techniques, pulse train generators, etc., can solve the problems of increasing the duration of the voltage pulse, time constant, and great challenges, and achieves high storage electric energy, easy operation, and higher compensation voltage
Inactive Publication Date: 2012-12-27
CHEN PING +2
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Benefits of technology
[0011]Solid-state switches can turn on / off thousands of times or more per second if their on / off time is on the order of microsecond or shorter. The present invention provides a high voltage compensation cell (HVCC) design for the voltage droop compensation of solid-state Marx modulators, incorporating the advantages of the fast speed of electrically triggered solid-state switches which are easy to operate and have the ability of electrical current interruption, with additional inductive component to resist any abrupt change of current in the circuitries. The compensation voltage output by a HVCC is smoothly raised to match the voltage droop of the MC bank of the Marx modulator and maintain a flat voltage output of the entire Marx modulator. The HVCCs designed with the scheme in the present invention have a charge voltage as high as that of the MCs of the Marx modulators, thus eliminating the need for additional charge voltage source, as in the vernier regulator. The HVCCs have high stored electric energy, so a single HVCC can actively compensate the voltage droop of the MC bank of the Marx modulator in multiple times and provide higher compensation voltage.
[0012]The new compensation circuitry that utilizes HVCCs in series as a HVCC bank operates with an intelligent control system. An example of the intelligent control systems is a computer control system with the capability of voltage variation detection and feedforward correction (see paper of D. Yu, Particle Accelerator Conference 1993). If the voltage of the MC bank of the Marx modulator droops to a level that a compensation action is needed, the intelligent control system will trigger the solid-state switches of a HVCC to release its electric energy. The inductive components in the compensation circuitry of the HVCC will prevent its entire voltage from adding all at once to that of the MC bank of the Marx modulator, thus narrow the pulse flattop fluctuation range and smooth out the voltage compensation actions. Said controllable compensation actions can be repeated many times as long as the stored energy in the compensation circuitry remains sufficient. Using this multiple compensation principle, the number of CCs is reduced and the design of the compensation circuitry is simplified. The voltage droop of the MC banks of the Marx modulators is controlled within the range required by their loads.
[0014]The present invention applies to designing a compensation circuitry of long-pulse Marx modulators which are used by particle accelerators and radars, and Marx pulsers that output high voltage pulses used in weapon effect simulators, fusion research devices, lasers etc. The invention also applies to a Marx pulser operating with a small load or outputting a long pulse. The compensation circuitry comprising a HVCC bank that has a plurality of HVCCs in series enables an entire Marx modulator to maintain a constant voltage output. In addition to these applications, the compensation scheme in the present invention applies to low-voltage pulsers with several kilovolts or less, as the compensation circuitries can be easily scaled down.
Problems solved by technology
However, a great challenge appears if the Marx modulator has a long output pulse or a small load.
A reduction in the time constant or an increase of the voltage pulse duration would lead to a significant voltage reduction at the end of a long voltage pulse, which is generally not acceptable for an rf load such as a klystron.
To limit the voltage droop in a narrow range that is required by the load, designers of the Marx modulator need to increase the time-constant t. Since the load is normally not changeable, the total capacitance, Cm, of the Marx modulator need to be increased dramatically, which is equivalent to increasing the total stored electrical energy of the Marx modulator and will incur a great amount of expense.
However, problems exist in these compensation cell designs.
Second, the VCs cannot provide flexible compensation.
Third, many VCs are needed for a Marx modulator with a long output pulse because the VC's storage energy is low and its compensation ability is limited by the low voltage.
Fourth, the low charge voltage results in large ohmic loss due to increased charge current, thus diminishing the efficiency, or the energy utilization ratio.
All of these problems not only complicate the circuit design, but also increase the cost of the circuitry with uncertain compensation results because a plurality of VCs in the compensation circuitry increase the parasitic inductance and may cause uncontrollable fluctuation during the flat top of the pulsed voltage output.
Furthermore, the footprint of the Marx modulator expands as more VCs are added.
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first embodiment
[0027]FIG. 2a illustrates the present invention of the high voltage compensation cell, or HVCC. The HVCC topology shown in FIG. 2a includes HVCC main switch 32 with its isolated switch drive 40, HVCC charge switch 36 with its isolated switch drive 42, HVCC energy storage capacitor 34, HVCC bypass diode 38, compensation inductor 44, and compensation diode 46. All of the isolated switch drives in the HVCC accept control signals from an intelligent control system of the Marx modulator, such as a computer control system and / or a feedforward system, which can detect the voltage variations on the Marx modulator's load through devices such as a voltage divider parallel to or in series of the load. The intelligent control system of the Marx modulator is not included in the HVCC topology in this figure since it controls the entire Marx modulator, not only a cell of the modulator. An example of the intelligent control system used in the integrated Marx modulator can be found in FIG. 4, where ...
second embodiment
[0030]The second embodiment can be viewed in two separate parts (see FIG. 3b). The left part in FIG. 3b is a buck converter. When this part works in switching mode power supply (SMPS), it has a variable output voltage that is related to the voltage of HVCC energy storage capacitor 34 and the duty cycle of HVCC main switch 32. However, the SMPS mode is not used in compensation actions. Instead, in the present invention, HVCC main switch 32 is triggered by said intelligent control system through its isolated switch drive 40 whenever compensation is needed. HVCC energy storage capacitor 34 is charged to a high voltage, which can be identical to that of MC, so that it stores sufficient electric energy to be used in the ensuing compensation actions. The right part in FIG. 3b is the same as the topology of a MC, where direct compensation capacitor 52, in the position of energy storage capacitor 14 in FIG. 1, receives the regulated compensation energy from the left part and thus functions ...
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A novel design scheme for the compensation circuitry of solid-state Marx modulators has been described for enhancing the compensation ability of the compensation cells of solid-state Marx modulators and simplifying the entire circuitry of the modulator. High-speed solid-state switches are adopted in the new compensation cell for the control of the compensation actions. Inductive components and diodes are adopted in the design scheme to smooth the flattop of the voltage pulse output by the Marx modulator.
Description
GOVERNMENT RIGHTS[0001]This invention was made with government support under Grant No. DE-FG02-08ER85052 awarded by the U.S. Energy Department. The government may have certain rights in the invention.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention comprises a new design scheme for a compensation circuitry for the output voltage pulse of a solid-state Marx modulator. Specifically, design and utilization methods of high voltage compensation cells (HVCCs) are introduced into a high-voltage solid-state Marx modulator for counteracting the voltage droop of its output pulse when the Marx modulator is used in high-power and long-pulse applications. Inductive components regulated by solid-state switches are used in the HVCCs for reliably compensating the voltage droop of the long output pulse (around millisecond order) of the Marx modulator. The invention is also applicable to solid-state Marx pulsers that have a large voltage droop in output voltage pulses.[0...
Claims
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IPC IPC(8): H03K3/017
CPCH03K7/08H03K17/74H03K17/063H03K3/57
InventorCHEN, PINGLUNDQUIST, MARTIN L.YU, DAVID U.L.
OwnerCHEN PING