Compact Marx generator based on impact ionization semiconductor device

Abstract

The invention discloses a compact Marx generator based on an impact ionization semiconductor device, and relates to the field of a pulse power technology and a power semiconductor device crossing technology. Comprising N stages of sub Marx generators which are cascaded in sequence, and each sub Marx generator comprises an impact ionization semiconductor device, a first charging isolation element, a second charging isolation element, an energy storage unit, a first ground capacitor and a second ground capacitor; for any stage of sub Marx generator, the first end of the impact ionization semiconductor device is connected with the first end of the first charging isolation element, the first end of the first ground capacitor and the first end of the energy storage unit, the second end of the first ground capacitor is grounded, the second end of the impact ionization semiconductor device is connected with the first end of the second charging isolation element, and the second end of the second charging isolation element is grounded. The second end of the second charging isolation element is connected with the second end of the energy storage unit and the first end of the second ground capacitor, and the second end of the second ground capacitor is grounded. According to the compact Marx generator, the conduction safety is improved.

Description

Technical Field

[0001] This application relates to the cross-technical field of pulsed power technology and power semiconductor devices, and in particular to a compact Marx generator based on an impulse ionization semiconductor device. Background Technology

[0002] The current main development trend in pulsed power technology is towards high peak power and high average power. The Marx generator is a classic circuit for generating high-voltage pulses. While Marx generators based on high-power gas switches can easily generate high-power pulses ranging from hundreds of kilovolts to megavolts and from thousands of amperes to hundreds of kiloamperes, they are limited by the short lifespan and low repetition frequency of the gas switches, making it difficult to meet the future demands for long lifespan and high repetition rate operation in the pulsed power technology field. All-solid-state Marx generators using semiconductor devices can operate at repetitive frequencies, have long lifespans, and have broad application prospects.

[0003] Current all-solid-state Marx generators using semiconductor devices are developing towards modularity, miniaturization, and high frequency. All-solid-state Marx generators often use fully controllable semiconductor devices, which suffers from limited power capacity and complex isolation drive circuits. Marx generators using avalanche transistors do not require isolation drive circuits and have extremely fast response times, but their power capacity is lower. Regardless of the semiconductor device used, achieving high repetition rates and high power operation faces challenges such as complex circuitry, a large number of required components, and high equipment costs.

[0004] Researchers have discovered that semiconductor devices containing pn junctions can achieve sub-nanosecond turn-on under reverse bias of the pn junction, triggered by a rapid overvoltage pulse. This gate-controlled turn-on is called a impulse ionization wave or delayed ionization wave, and impulse ionization semiconductor devices have been fabricated based on this special effect. Theoretically, semiconductor devices based on the impulse ionization principle have enormous application potential and could potentially replace gas switches and existing semiconductor devices as the mainstream components in future repetition frequency Marx generators.

[0005] However, the safe operating conditions of impulse ionization semiconductor devices are quite stringent. Generally, the maximum rise rate of the overvoltage front is required to be above 1 kV / ns, and the overvoltage multiple is about twice the rated breakdown voltage of the device. This leads to the problem that Marx generators made using impulse ionization semiconductor devices have difficulty in safely turning on the device. Summary of the Invention

[0006] Therefore, it is necessary to provide a compact Marx generator based on an impact ionization semiconductor device to address the aforementioned technical problems.

[0007] The following technical solution is adopted in this specification: This specification provides a compact Marx generator based on a shock ionization semiconductor device, comprising: N The sub-Marx generators are cascaded in series. Each sub-Marx generator includes an impulse ionization semiconductor device, a first charging isolation element, a second charging isolation element, an energy storage unit, a first capacitor to ground, and a second capacitor to ground. For any level of sub-Marx generator, the first end of the impulse ionization semiconductor device is connected to the first end of the first charging isolation element, the first end of the first ground capacitor and the first end of the energy storage unit, respectively. The second end of the first ground capacitor is grounded. The second end of the impulse ionization semiconductor device is connected to the first end of the second charging isolation element. The second end of the second charging isolation element is connected to the second end of the energy storage unit and the first end of the second ground capacitor, respectively. The second end of the second ground capacitor is grounded. The second terminal of the first charging isolation element of the first stage sub-Marx generator is connected to the DC high voltage power supply. The second terminal of the first charging isolation element of the other stage sub-Marx generators is connected to the first charging isolation element of the corresponding previous stage sub-Marx generator. The second terminal of the second charging isolation element of the last stage sub-Marx generator is also connected to the load. The pn junction capacitance of the impulse ionization semiconductor device is smaller than the capacitance values ​​of the first to ground capacitance and the second to ground capacitance. Specifically, by triggering the pulse source to turn on the impulse ionization semiconductor device in the first-stage sub-Marx generator or the preceding sub-Marx generators, after the impulse ionization semiconductor device in any sub-Marx generator is turned on, the energy storage unit of the preceding stage charges the second ground capacitor. The second ground capacitor forms a fast-edge overvoltage. This voltage is applied to the two ends of the impulse ionization semiconductor device in the following stage after being divided by the two ground capacitors of the following stage, so that the impulse ionization semiconductor device in the following sub-Marx generator is turned on, so that the impulse ionization semiconductor devices in the entire compact Marx generator are turned on in sequence, and a high-voltage, high-current pulse is output on the load.

[0008] Optionally, the compact Marx generator includes two triggering methods: The first triggering method is to apply overvoltage to the first-stage or several-stage impulse ionization semiconductor devices by using a trigger pulse source. The trigger pulse source used in the first triggering method needs to be able to charge the reverse-biased pn junction of the impulse ionization semiconductor device with a large current to achieve the impulse ionization condition of the pn junction. The second triggering method involves connecting a compact Marx generator in series with a trigger pulse source. The overvoltage generated by the operation of the trigger pulse source causes the impulse ionization semiconductor devices in the compact Marx generator to break down sequentially. The trigger pulse source used in the second triggering method needs to have the same current carrying capacity as the compact Marx generator, and have a sufficiently high amplitude and a sufficiently small leading edge to ensure the safe conduction of the impulse ionization semiconductor devices in the compact Marx generator.

[0009] Optionally, after the impulse ionization semiconductor device of the preceding sub-Marx generator is triggered by the fast pulse output by the trigger pulse source, the potential at one end of the energy storage unit changes, generating an overvoltage on the next-stage impulse ionization semiconductor device, causing it to conduct impulse ionization.

[0010] Optionally, the fast pulses transmitted step by step are assisted by voltage division by the two ground-connected capacitors in each sub-Marx generator, so that most of them are applied to the two ends of the impulse ionization semiconductor device. The impulse ionization semiconductor device satisfies the following during the step-by-step conduction process: ; in, yes m -1 level accumulated pulse voltage, It is the charging voltage of the energy storage unit. It is the first m The accumulated pulse voltage after the stage switch is turned on. It is a pulse from m -1 level m The attenuation coefficient of stage transmission.

[0011] Optionally, the impulse ionization semiconductor device is a device including at least one pn junction, or the impulse ionization semiconductor device uses a Schottky junction or an N / N junction. + Devices with special junctions constructed by doping gradients; shock ionization semiconductor devices are unidirectional or bidirectional pressure-bearing devices; shock ionization semiconductor devices are bipolar or multipolar devices; When the impact ionization semiconductor device is a two-electrode device, it is impact ionization and conduction is achieved through the overvoltage between the two electrodes. When the impulse ionization semiconductor device is a triode device, two poles are used while the other pole is left floating. Alternatively, a trigger signal is generated by the pre-amplifier and applied to the trigger pole. The impulse ionization semiconductor device turns on under the simultaneous action of the trigger pole signal and the overvoltage between the other two poles.

[0012] The above-mentioned technical solutions adopted in this specification can achieve the following beneficial effects: In the compact Marx generator provided in this specification, the front-end circuit charges the second ground capacitor of the current stage through a series energy storage unit connected to the impulse ionization semiconductor device. Due to the compact structure of this compact Marx generator, the inductance of each sub-Marx generator is small, and the equivalent capacitance of the second ground capacitor and the subsequent circuit is small. A fast-rising-edge overvoltage will be formed on the second ground capacitor. Since the pn junction capacitance of the impulse ionization semiconductor device in the subsequent sub-Marx generator is much smaller than the energy storage unit capacitance and smaller than the first and second ground capacitors, the overvoltage formed across the impulse ionization semiconductor device in the subsequent sub-Marx generator after voltage division not only has a sufficient amplitude but also a sufficient voltage rise rate, ensuring that the impulse ionization semiconductor device in the subsequent sub-Marx generator meets the safe conduction conditions. By proceeding in sequence, the impulse ionization semiconductor devices in the entire compact Marx generator can be reliably and safely turned on in sequence. Attached Figure Description

[0013] The accompanying drawings, which are included to provide a further understanding of this application and form part of this application, illustrate exemplary embodiments and are used to explain this application, but do not constitute an undue limitation of this application. In the drawings:

[0014] Figure 1 This specification provides a schematic diagram of a compact Marx generator based on an impact ionization semiconductor device. Figure 2 This is a schematic diagram of another compact Marx generator based on an impact ionization semiconductor device, provided for the purposes of this specification.

[0015] Explanation of reference numerals in the attached figures: 101. Sub-Marx generator; 201. Impact ionization semiconductor device; 202. First charging isolation element; 203. Second charging isolation element; 204. Energy storage unit; 205. First capacitor to ground; 206. Second capacitor to ground; 207. DC high voltage power supply; 208. Load; 209. Trigger pulse source. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this specification clearer, the technical solutions of this application will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments in this specification without creative effort are within the scope of protection of this application.

[0017] This impulse ionization turn-on phenomenon has been observed in various diodes, transistors, thyristors, fast ionization thyristors (FID), deep level thyristors (DLD), silicon avalanche sharpeners (SAS), shock-ionized thyristors (SID), breakover diodes (BOD), and thyristor surge suppressors (TSS). The turn-on speed is directly related to parameters such as the pn junction thickness, material breakdown field strength, overvoltage amplitude, and rise time, and is typically much faster than conventionally triggered fully controlled semiconductor devices, similar to that of avalanche transistors. Generally, the faster the applied pulse leading edge, the higher the impulse ionization voltage, the faster the turn-on speed, and the better the pulse steepening effect. Applying the pulse steepening characteristic of this switch in the Marx generator promises to achieve a progressively steepening effect in the output pulse while simultaneously enabling multi-level voltage superposition output. In this topology, semiconductor devices operate in a fast pulse overvoltage turn-on mode, eliminating the need for high-voltage isolation drive, significantly simplifying the circuit and ensuring reliable sequential turn-on.

[0018] In the existing technology, researchers have proposed several solutions: (1) A nanosecond high voltage pulse driven thyristor overcurrent conduction device and method: using a spiral pulse generation module to output a nanosecond high voltage pulse to trigger the thyristor to enter the impulse ionization mode for conduction. This scheme can only be used to trigger a single device to enter the impulse ionization mode.

[0019] Furthermore, this solution provides a common chip thyristor impulse ionization triggering method and pulse source structure. Its impulse ionization triggering is limited to a single thyristor with a certain structure, without taking into account that semiconductor switches or structures with pn junctions generally have or even have better impulse ionization pulse steepening effects. At the same time, its topology is relatively simple and does not take into account the voltage superposition approach for multi-stage applications of impulse ionization devices.

[0020] (2) A pulse power supply based on avalanche tube Marx generator and LTD circuit: its front stage adopts external triggering, and the rear stage is self-triggered under the overvoltage formed by the action of the front stage. Due to the use of avalanche tube, the device has low voltage and small current.

[0021] This scheme proposes a topology for an LTD pulse generator based on Marx circuits, whose self-triggering principle simplifies the drive circuit. However, this scheme is based on avalanche diodes, and due to the current and voltage limitations of the avalanche diodes during conduction, achieving high voltage output levels still results in a very complex circuit structure. Furthermore, due to the inherent stage limitations of the circuit topology, energy transfer efficiency decreases significantly at higher output voltages, leading to increased design difficulty and manufacturing costs.

[0022] (3) Research on a compact solid-state Marx generator: A half-bridge structure is formed by connecting a P-type switch as a charging tube and an N-type switch as a discharging tube in series and driving them simultaneously with the same signal. A 24-stage solid-state Marx generator is built using a common primary-side through-hole magnetic ring driving scheme, and a high-voltage square wave pulse of 10 kV, 1 kHz, and 5 μs is obtained on a 10 kΩ resistive load. This scheme uses fully controlled devices and focuses on solving the isolation driving scheme.

[0023] This device uses a half-bridge circuit to simultaneously drive both the discharge and charging transistors, reducing the number of drive circuits by half compared to multi-stage Marx circuits. However, since the main switch is a MOSFET, its multi-stage operation still involves considerable complexity, and factors such as high-voltage isolation must be considered. Furthermore, the withstand voltage rating of individual switches remains relatively low, placing higher demands on the number of pulse source stages and their reliability.

[0024] (4) A Marx generator triggered by impulse ionization wave mode: The Marx generator is constructed using semiconductor devices that operate based on impulse ionization mode, but this scheme does not utilize the compact Marx generator to compress the pulse leading edge step by step, thereby forming overvoltage pulses sufficient to cause safe impulse ionization on the semiconductor devices inside the Marx generator.

[0025] This scheme utilizes semiconductor devices operating in impulse ionization mode to construct a Marx generator. However, it fails to leverage the small single-stage inductance and large capacitance to ground characteristic of compact Marx generators to achieve pulse sharpening at each stage; it does not consider the large pn junction capacitance of high-voltage, high-current semiconductor devices, which means that the impulse ionization semiconductor devices cannot obtain sufficient overvoltage to achieve the impulse ionization effect when overvoltage occurs; it does not utilize the large capacitance to ground, which can increase the overvoltage division ratio on the semiconductor device and thus promote impulse ionization; it does not utilize the characteristics of progressively increasing voltage rise and progressively compressing leading edge, which make the impulse ionization of semiconductor devices increasingly safe and faster; and it does not utilize the adjustment of the main capacitor and capacitance to ground to achieve the function of adjusting the output voltage waveform.

[0026] Furthermore, the mainstream switch in the pulse power technology field is the gas switch, which has the advantage of high power, but suffers from problems such as low repetition frequency, limited lifespan, and a certain probability of self-discharge. Semiconductors can be used to construct small pulse power devices with high repetition frequency, but generally have limited power capacity and slow response speed (except for avalanche tubes). Future large pulse power devices require ultra-high power, high repetition frequency operation, and long lifespan, while some medium-sized pulse power devices require fast waveform leading edges. Using high-power, fast-response impulse ionization semiconductor devices to construct pulse power devices is a highly advantageous technical route. The Marx generator is a widely used topology in pulse power technology. The safe operating conditions of impulse ionization semiconductor devices are quite stringent, generally requiring a maximum overvoltage leading edge rise rate of more than 1 kV / ns and an overvoltage multiple of about twice the device's rated breakdown voltage. To meet the safe operating requirements of impulse ionization semiconductor devices, some special measures must be taken. Using a compact Marx generator is a technical path that just meets many of the limiting factors.

[0027] Based on this, the present invention designs a compact Marx generator based on the principle of impulse ionization of semiconductor devices. This compact Marx generator provides a new solution for nanosecond and even sub-nanosecond pulse power supplies.

[0028] This invention utilizes the large capacitance to ground characteristic of compact Marx generators to increase the overvoltage sharing ratio of downstream semiconductor devices when upstream semiconductor devices operate, thereby overcoming the problem that the large capacitance of high-power semiconductor devices makes it difficult to form overvoltages.

[0029] This invention utilizes the characteristics of progressively increasing voltage and progressively compressing pulse leading edge, which make the ionization of semiconductor devices increasingly safe and faster, to achieve safe operation of a compact Marx generator and further compression of the pulse leading edge.

[0030] This invention adjusts the output voltage waveform by adjusting the main capacitor and the capacitor to ground, including forming an approximate square wave and forming a pulse waveform that is high at the beginning and low at the end or low at the beginning and high at the end.

[0031] The impact ionization semiconductor devices permitted to be used in this invention can be various structures containing a reverse-biased pn junction, but utilizing the impact ionization effect of the pn junction under fast-edge overvoltage, including but not limited to diodes, transistors, thyristors, gate turn-off thyristors (GTO), MOS-controlled thyristors (MCT), super gate turn-off thyristors (SGTO), integrated gate-commutated thyristors (IGCT), FID, DLD, SAS, TSS, SID, BOD, PIN diodes, etc.

[0032] The technical solutions provided by the various embodiments of this application are described in detail below with reference to the accompanying drawings.

[0033] Figure 1 This is a schematic diagram of a compact Marx generator based on an impact ionization semiconductor device, as described in this specification. The compact Marx generator specifically includes: N The sub-Marx generators 101 are cascaded in sequence. Each sub-Marx generator 101 includes an impulse ionization semiconductor device 201, a first charging isolation element 202, a second charging isolation element 203, an energy storage unit 204, a first capacitor to ground 205, and a second capacitor to ground 206.

[0034] For any level of sub-Marx generator 101, the first end of the impulse ionization semiconductor device 201 is connected to the first end of the first charging isolation element 202, the first end of the first ground capacitor 205, and the first end of the energy storage unit 204, respectively. The second end of the first ground capacitor 205 is grounded. The second end of the impulse ionization semiconductor device 201 is connected to the first end of the second charging isolation element 203. The second end of the second charging isolation element 203 is connected to the second end of the energy storage unit 204 and the first end of the second ground capacitor 206, respectively. The second end of the second ground capacitor 206 is grounded.

[0035] The second terminal of the first charging isolation element 202 of the first-stage sub-Marx generator 101 is connected to the DC high-voltage power supply 207. The second terminal of the first charging isolation element 202 of the other sub-Marx generators 101 is connected to the first charging isolation element 202 of the corresponding previous sub-Marx generator 101. The second terminal of the second charging isolation element 203 of the last sub-Marx generator 101 is also connected to the load 208. The pn junction capacitance of the impulse ionization semiconductor device 201 is smaller than the capacitance values ​​of the first ground capacitance 205 and the second ground capacitance 206.

[0036] Specifically, by triggering the pulse source 209 to turn on the impulse ionization semiconductor device 201 in the first-stage sub-Marx generator 101 or the previous few stages of the sub-Marx generator 101, after the impulse ionization semiconductor device 201 in any stage of the sub-Marx generator 101 is turned on, the energy storage unit 204 of the current stage charges the second ground capacitor 206, and the second ground capacitor 206 forms a fast leading edge overvoltage. This voltage is applied to the two ends of the impulse ionization semiconductor device 201 of the next stage after being divided by the two ground capacitors of the next stage, so that the impulse ionization semiconductor device 201 in the next stage of the sub-Marx generator 101 is turned on, so that the impulse ionization semiconductor devices 201 in the entire compact Marx generator are turned on in sequence, and a high voltage and high current pulse is output on the load 208.

[0037] After the impulse ionization semiconductor device 201 in each stage sub-Marx generator 101 is turned on, its preceding circuit will charge the second ground capacitor 206 of the preceding stage through the energy storage unit 204 connected in series with the impulse ionization semiconductor device 201. Due to the compact structure of this Marx generator, the inductance of each stage sub-Marx generator 101 is small, and the equivalent capacitance of the second ground capacitor 206 and the subsequent circuit is small. A fast-rising-edge overvoltage will be formed on the second ground capacitor 206. Since the pn junction capacitance of the impulse ionization semiconductor device 201 in the subsequent stage sub-Marx generator 101 is much smaller than that of the preceding stage sub-Marx generator 101, the preceding stage sub-Marx generator 101 will charge the second ground capacitor 206 through the energy storage unit 204 connected in series with the impulse ionization semiconductor device 201. The energy storage unit 204 has a capacitance smaller than the first and second ground capacitances 206. Therefore, the voltage divided across the impulse ionization semiconductor device 201 in the subsequent sub-Marx generator 101 forms an overvoltage with sufficient amplitude and a sufficient voltage rise rate, ensuring that the impulse ionization semiconductor device 201 in the subsequent sub-Marx generator 101 meets the safe conduction conditions. By doing this sequentially, the impulse ionization semiconductor device 201 in the entire compact Marx generator can be reliably and safely turned on in sequence, and output a high-voltage, high-current pulse on the load 208.

[0038] The compact Marx generator includes two triggering methods: The first triggering method is to apply overvoltage to the first-stage impulse ionization semiconductor device 201 or the impulse ionization semiconductor devices 201 of the previous stages through the trigger pulse source 209. At this time, the trigger pulse sources 209 are not grounded to each other. The trigger pulse source 209 used in the first triggering method needs to be able to charge the reverse biased pn junction of the impulse ionization semiconductor device 201 with a large current to achieve the impulse ionization condition of the pn junction. Figure 1 This is the first triggering method.

[0039] The trigger pulse source 209 of the first triggering method requires high amplitude and short leading edge to charge the reverse bias pn junction of the semiconductor device with a large current, so as to achieve the impact ionization condition of the pn junction.

[0040] The second triggering method involves connecting the trigger pulse source 209 in series with the compact Marx generator. The overvoltage generated by the trigger pulse source 209 causes the sequential breakdown of each stage of the impulse ionization semiconductor device 201 in the compact Marx generator. The trigger pulse source 209 used in this second method needs to have the same current carrying capacity as the compact Marx generator, and possess a sufficiently high amplitude and a sufficiently small leading edge to ensure the safe conduction of the impulse ionization semiconductor device 201 in the compact Marx generator. For example... Figure 2 As shown, Figure 2 This is a schematic diagram of the second triggering method.

[0041] The trigger pulse source 209 for both triggering methods includes, but is not limited to, using pulse transformers, spiral transformers, Tesla transformers, various Marx circuits, various LTD circuits, various TVA pulse sources, etc. as driving sources, and including, but not limited to using gas switches, magnetic switches and semiconductor devices as switching or steepening measures.

[0042] It should be noted that the implementation technology of the trigger pulse source 209 of the compact Marx generator of the present invention is not limited. The present invention provides two ways to apply the trigger pulse source 209 to the compact Marx generator. In fact, the trigger pulse source 209 is not necessarily limited to the pre-stage of the compact Marx generator, but may also be applied to the intermediate stage or the post-stage.

[0043] The impulse ionization semiconductor device 201, which turns on rapidly under fast-leading overvoltage, is used as the switch for the compact Marx generator. Compared with gas switches, it has the advantage of repetitive frequency operation, and compared with other semiconductor devices, it has the advantages of fast operation speed and high power capacity.

[0044] The compact Marx generator uses a shock ionization semiconductor device 201, which can be replaced by some commercial semiconductor devices with low manufacturing process requirements. Therefore, it is widely available, has a low cost, and is not subject to "bottleneck" problems.

[0045] When the front-end of the compact Marx generator is turned on, the impulse ionization semiconductor device 201 in the subsequent stage is subjected to overvoltage. Since the discharge mode is CLC circuit discharge, and the reverse-biased pn junction of the subsequent semiconductor device, which is part of the load 208, is a nonlinear device, during the discharge process, the capacitance of the reverse-biased pn junction of the impulse ionization semiconductor device 201 in the subsequent sub-Marx generator 101 gradually decreases. The residual inductance freewheeling current of the sub-Marx generator 101 charges the nonlinear capacitance of the reverse-biased pn junction, causing the overvoltage of the subsequent semiconductor device to rise faster and faster, which is beneficial to the safe turn-on of the semiconductor device.

[0046] This invention utilizes the small residual inductance of the compact Marx generator single-stage sub-Marx generator 101. The discharge cycle of the preceding capacitor to the subsequent equivalent capacitor (the capacitance to ground as seen from the output of the sub-Marx generator 101) through the inductor is short, enabling step-by-step compression of the pulse leading edge. The step-by-step voltage increase and leading edge compression result in increasingly safer impact ionization of subsequent semiconductor devices, faster device operation, and further compression of the output pulse leading edge.

[0047] This invention utilizes the large capacitance to ground characteristic of compact Marx generators to increase the overvoltage sharing ratio of subsequent semiconductor devices when the front-stage impulse ionization semiconductor device 201 operates, overcoming the problem that the large capacitance of the pn junction of the semiconductor device makes it difficult to form overvoltage when it is reverse biased.

[0048] The compact Marx generator established in this invention requires that the capacitance to ground (first ground capacitor 205, second ground capacitor 206), the reverse-biased pn junction capacitance of the impulse ionization semiconductor device 201, and the energy storage element capacitance in the circuit satisfy a certain relationship, so that the discharge pulse can be progressively increased by superposition. After the impulse ionization semiconductor device 201 of the preceding sub-Marx generator 101 is triggered by the fast pulse output by the trigger pulse source 209, the potential at one end of the energy storage unit 204 changes rapidly, generating an overvoltage on the next-stage impulse ionization semiconductor device 201, causing it to conduct impulse ionization. Since the fast pulse discharge circuit is composed of the capacitances of each stage of energy storage elements, the reverse-biased pn junction capacitance of the impulse ionization semiconductor device 201, and the capacitance to ground, when the pulse is transmitted to the next-stage sub-Marx generator 101, it will be divided by a series of capacitors, and finally applied to the first stage. m The voltage across the 201-stage impulse ionization semiconductor device is not complete. m -1) times the charging voltage, but rather the result of voltage division by a series of capacitors in the subsequent stage and the reverse-biased pn junction capacitor of the impulse ionization semiconductor device 201. That is, the fast pulses transmitted stage by stage are assisted by the two ground-based capacitors in each stage of the sub-Marx generator 101, so that most of them can be applied to the two ends of the impulse ionization semiconductor device 201. Therefore, to output a high-voltage fast pulse, not only is a compact circuit and low inductance required, but the impulse ionization semiconductor device 201 must also meet the following requirements during the stage-by-stage conduction process:

[0049] ; in, It is the pulse voltage accumulated from the previous stage. This is the charging voltage of energy storage unit 204. It is the first m The accumulated pulse voltage after the stage switch is turned on. It is a pulse from ( m -1) Level mThe attenuation coefficient of stage transmission is determined by the capacitance of each stage and stray capacitance. Only when the circuit meets this condition can the pulse obtain an increasing peak voltage during the stage-by-stage switching process.

[0050] The output voltage waveform can be adjusted by regulating the main capacitor and the capacitor to ground, for example, to form an approximate square wave.

[0051] In one embodiment, the shock ionization semiconductor device 201 is a device including at least one pn junction, or the shock ionization semiconductor device 201 uses a device including a Schottky junction or an N-type junction. + This refers to a device with a special junction constructed from a doping gradient. Under a high voltage applied at the fast leading edge, the voltage-bearing pn junction or special junction achieves impulse ionization conduction. Optionally, if a switching device such as a thyristor contains multiple pn junctions, the bias direction with better pulse characteristics and higher repetition lifetime should be preferred. The impulse ionization semiconductor device 201 does not limit the type of semiconductor material and can use various semiconductor materials including silicon, silicon carbide, gallium nitride, diamond, etc.

[0052] The impulse ionization semiconductor device 201 used in this invention can be either unidirectional voltage-bearing / unidirectional impulse ionization conduction (e.g., a diode) or bidirectional voltage-bearing / bidirectional impulse ionization conduction (e.g., a thyristor, a back-to-back diode, or a TSS). Bidirectional voltage-bearing means that the impulse ionization semiconductor device 201 can withstand forward or reverse voltage. When biased in either direction, a reverse-biased pn junction acts as the working pn junction, bearing the voltage and quickly conducting when an overvoltage occurs. A unidirectional voltage-bearing impulse ionization semiconductor device 201 bears voltage in one direction and can quickly conduct when an overvoltage occurs; it cannot bear voltage in the other direction and conducts directly.

[0053] Alternatively, the impulse ionization semiconductor device 201 can also be a combination of various pressure-bearing and conduction types, such as thyristors and diodes connected in reverse parallel.

[0054] Optionally, the impulse ionization semiconductor device 201 can be a two-electrode device or a multi-electrode device. When the impulse ionization semiconductor device 201 is a two-electrode device, it is impulse-ionized and turned on by an overvoltage between the two electrodes. When the impulse ionization semiconductor device 201 is a three-electrode device, two electrodes are used while the other electrode is left floating. Alternatively, a trigger signal is generated by a pre-stage and applied to the trigger electrode (or gate, base). The impulse ionization semiconductor device 201 then turns on under the simultaneous action of the trigger electrode signal and the overvoltage between the other two electrodes. For example, if the impulse ionization semiconductor device 201 is a thyristor, the first and second terminals can be cathodes or anodes, and the gate is left floating.

[0055] Two-electrode devices have two electrodes, a cathode and a anode, and are activated by impulse ionization through an overvoltage between the two electrodes. Multi-electrode devices, such as transistors and thyristors, are typically used with two electrodes while the third electrode is left floating, and are activated by impulse ionization through an overvoltage between the two electrodes; or, a trigger signal is generated by a preceding stage and applied to the trigger electrode (gate, base, etc.), and the device is activated under the combined action of the trigger electrode signal and the overvoltage between the other two electrodes.

[0056] When each semiconductor switch 201 is in the blocking state, each energy storage unit 204 and each semiconductor switch 201 are connected in parallel, and the energy storage units 204 are connected in parallel with each other. Simultaneously, each energy storage unit 204 is charged by an external high-voltage power supply 207. When each semiconductor switch 201 is in the conducting state, each energy storage unit 204 and each semiconductor switch 201 are connected in series, and the energy storage units 204 are connected in series with each other. High-voltage pulses are output through the discharge of each energy storage unit 204. Thus, this compact Marx generator can achieve the functions of parallel charging and series discharging.

[0057] Regarding the charging of the compact Marx generator: charging can be done in parallel, in cascade, or different parts can use different charging methods or different charging voltages. Figure 1 and Figure 2 The invention presents a cascaded charging scheme for a compact Marx generator. The compact Marx generator provided by this invention can also employ a parallel charging scheme with resistor isolation.

[0058] Figure 1 and Figure 2 The given charging isolation element is a resistor, but it can also be an inductor, a combination of inductors and resistors, a coupled inductor, or even a semiconductor device such as a diode or silicon stack (in which case it is necessary to ensure that the charging isolation element does not conduct under overvoltage).

[0059] Based on the topology and shock ionization semiconductor device 201 used in the compact Marx generator, the charging power supply may be positive, negative, or both.

[0060] Regarding the polarity of the compact Marx generator: The impulse ionization semiconductor device 201 used in a compact Marx generator can be either bidirectionally voltage-bearing or unidirectionally voltage-bearing. Voltage-bearing means it can withstand voltage; a compact Marx generator composed of a bidirectionally voltage-bearing device can be charged in both positive and negative directions, resulting in two polarities of output. A compact Marx generator composed of a unidirectionally voltage-bearing device can be charged in either positive or negative direction, resulting in two polarities of output.

[0061] Regarding the capacitance to ground of the compact Marx generator: Compact Marx generators must have a certain capacitance to ground. This capacitance can be stray capacitance, such as the capacitance of a metal structure to the casing (or ground); it can also be a solid capacitor. The capacitance of the impulse ionization semiconductor device 201 is relatively large, making it difficult to generate overvoltages. Therefore, stray capacitance is often used to help generate overvoltages on the semiconductor device. It is possible to add electrodes to the compact Marx generator to provide electric field shielding and also increase the capacitance to ground (shielding electrodes or capacitance-enhancing electrodes).

[0062] Regarding the structural form of the compact Marx generator: The impulse ionization semiconductor device 201 can be multiple impulse ionization semiconductor devices 201 connected in parallel.

[0063] Energy storage unit 204 can be multiple energy storage units 204 connected in parallel. Energy storage unit 204 can be various capacitive components such as capacitors, transmission lines, artificial transmission lines, pulse forming networks, Blumlein lines, etc.

[0064] Alternatively, the impact ionization semiconductor device 201 and the energy storage unit 204 can be configured into branches, with multiple branches connected in parallel to perform the functions of energy storage and conduction.

[0065] The impulse ionization semiconductor device 201 can be used in parallel, in series, or in a combination of both. For example, if the current capacity of the impulse ionization semiconductor device 201 is insufficient, multiple devices can be connected in parallel; if the rated voltage is insufficient, multiple devices can be connected in series; they can also be connected in parallel followed by series, or series followed by parallel. Series connection is used to improve the withstand voltage level, while parallel connection is used to increase the current carrying capacity. Different series and parallel connection structures can also be designed according to actual needs such as power capacity and RC parameters.

[0066] Compact Marx generators may be made coaxially, or they may be mounted on a printed circuit board (PCB) or other insulating support, or a single stage may be made on a PCB and then multiple stages may be stacked.

[0067] Compact Marx generators may use gas, liquid, or solid insulation. Gases include various gases such as air, SF6, and nitrogen; liquids include various insulating liquids such as transformer oil, silicone oil, and capacitor oil; and solids include various solids such as epoxy resin, aerosol, and silicone rubber.

[0068] This invention avoids the complex isolation drive circuit of traditional solid-state Marx circuits; by directly utilizing the impact ionization effect of pn junctions, it is easy to achieve high voltage, high current and fast leading edge output; due to the use of semiconductor devices with the characteristics of repetitive frequency operation and long lifespan, this invention can generate both ultrafast leading edge (sub-nanosecond) short pulses (nanoseconds) and fast leading edge (nanoseconds or tens of nanoseconds) long pulses (microseconds).

[0069] This invention proposes combining the high voltage, high current, fast operation, high repetition frequency, and long lifespan characteristics of the impulse ionization semiconductor device 201 with the low inductance and high capacitance to ground characteristics of the compact Marx generator. During discharge, the reverse-biased pn junction capacitance of the impulse ionization semiconductor device 201 in the subsequent sub-Marx generator 101 gradually decreases. The residual inductance of the sub-Marx generator 101 freewheels and charges the nonlinear capacitance of this reverse-biased pn junction, causing the overvoltage rise rate of the subsequent semiconductor device to increase faster and faster. The small residual inductance of the single-stage sub-Marx generator 101 and the short discharge cycle of the preceding capacitor to the equivalent capacitance of the subsequent stage (the capacitance to ground as seen from the output of the sub-Marx generator 101) result in a progressively compressed pulse leading edge. In the compact Marx generator, the impulse ionization semiconductor device 201 operates progressively, with increasingly better operating conditions, higher output voltage, and a faster leading edge.

[0070] The output waveform of the compact Marx generator can be adjusted by changing the main capacitor and the capacitor to ground, thereby changing the voltage divider by changing the capacitor parameters. It is possible to output an approximate square wave waveform.

[0071] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

Claims

1. A compact Marx generator based on an impulse ionization semiconductor device, characterized in that, include: N The sub-Marx generators are cascaded in series. Each sub-Marx generator includes an impulse ionization semiconductor device, a first charging isolation element, a second charging isolation element, an energy storage unit, a first capacitor to ground, and a second capacitor to ground. For any level of sub-Marx generator, the first end of the impulse ionization semiconductor device is connected to the first end of the first charging isolation element, the first end of the first ground capacitor and the first end of the energy storage unit, respectively. The second end of the first ground capacitor is grounded. The second end of the impulse ionization semiconductor device is connected to the first end of the second charging isolation element. The second end of the second charging isolation element is connected to the second end of the energy storage unit and the first end of the second ground capacitor, respectively. The second end of the second ground capacitor is grounded. The second terminal of the first charging isolation element of the first stage sub-Marx generator is connected to the DC high voltage power supply. The second terminal of the first charging isolation element of the other stage sub-Marx generators is connected to the first charging isolation element of the corresponding previous stage sub-Marx generator. The second terminal of the second charging isolation element of the last stage sub-Marx generator is also connected to the load. The pn junction capacitance of the impulse ionization semiconductor device is smaller than the capacitance values ​​of the first to ground capacitance and the second to ground capacitance. Specifically, by triggering the pulse source to turn on the impulse ionization semiconductor device in the first-stage sub-Marx generator or the preceding sub-Marx generators, after the impulse ionization semiconductor device in any sub-Marx generator is turned on, the energy storage unit of the preceding stage charges the second ground capacitor. The second ground capacitor forms a fast-edge overvoltage. This voltage is applied to the two ends of the impulse ionization semiconductor device in the following stage after being divided by the two ground capacitors of the following stage, so that the impulse ionization semiconductor device in the following sub-Marx generator is turned on, so that the impulse ionization semiconductor devices in the entire compact Marx generator are turned on in sequence, and a high-voltage, high-current pulse is output on the load.

2. The compact Marx generator according to claim 1, characterized in that, The Marx generator includes two triggering methods: The first triggering method is to apply overvoltage to the first-stage or several-stage impulse ionization semiconductor devices by using a trigger pulse source. The trigger pulse source used in the first triggering method needs to be able to charge the reverse-biased pn junction of the impulse ionization semiconductor device with a large current to achieve the impulse ionization condition of the pn junction. The second triggering method involves connecting a compact Marx generator in series with a trigger pulse source. The overvoltage generated by the operation of the trigger pulse source causes the impulse ionization semiconductor devices in the compact Marx generator to break down sequentially. The trigger pulse source used in the second triggering method needs to have the same current carrying capacity as the compact Marx generator, and have a sufficiently high amplitude and a sufficiently small leading edge to ensure the safe conduction of the impulse ionization semiconductor devices in the compact Marx generator.

3. The compact Marx generator according to claim 1, characterized in that, After the impulse ionization semiconductor device of the preceding sub-Marx generator is triggered by the fast pulse output by the trigger pulse source, the potential at one end of the energy storage unit changes, generating an overvoltage on the next-stage impulse ionization semiconductor device, causing it to conduct impulse ionization.

4. The compact Marx generator according to claim 1, characterized in that, The fast pulses, transmitted stage by stage, are voltage-divided by the two ground-connected capacitors in each stage of the Marx generator, allowing most of them to be applied to the two ends of the impulse ionization semiconductor device; the impulse ionization semiconductor device satisfies the following during the stage-by-stage conduction process: ； in, yes m -1 level accumulated pulse voltage, It is the charging voltage of the energy storage unit. It is the first m The accumulated pulse voltage after the stage switch is turned on. It is a pulse from m -1 level m The attenuation coefficient of stage transmission.

5. The compact Marx generator according to claim 1, characterized in that, A shock ionization semiconductor device is a device that includes at least one pn junction, or a shock ionization semiconductor device that uses a Schottky junction or an N-type junction. + Devices with special junctions constructed by doping gradients; shock ionization semiconductor devices are unidirectional or bidirectional pressure-bearing devices; shock ionization semiconductor devices are bipolar or multipolar devices; When the impact ionization semiconductor device is a two-electrode device, it is impact ionization and conduction is achieved through the overvoltage between the two electrodes. When the impulse ionization semiconductor device is a triode device, two poles are used while the other pole is left floating. Alternatively, a trigger signal is generated by the pre-amplifier and applied to the trigger pole. The impulse ionization semiconductor device turns on under the simultaneous action of the trigger pole signal and the overvoltage between the other two poles.

Images