Marx topology nanosecond pulse power supply adaptive current limiting short circuit protection system

Abstract

The Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system proposed in the present invention is mainly divided into two parts: a current limiting module and an automatic quick-cut module. The current limiting module is integrated in the main circuit of the Marx generator. Through reasonable parameter design, when overcurrent occurs, the semiconductor switch tube can be transferred from the constant current area to the variable resistance area, thereby limiting the large current in the circuit. The function of the current limiting module is to limit the current amplitude, protect the switch tube from damage in a relatively short time, and provide sufficient time for the subsequent overcurrent protection module to operate. The automatic quick-cut module is used to deal with the situation of a long-term short circuit at the output end. It includes a short-circuit detection unit, a protection logic processing unit, and a protection action unit. A fault signal is generated by detecting whether the output end of the Marx generator is short-circuited, and an action signal is generated after signal processing, and finally the disconnection of the distribution switch of the main power circuit is controlled.

Description

Technical Field

[0001] The invention belongs to the field of pulse power supplies and relates to a Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system. Background Art

[0002] High-voltage pulse power supplies currently used in the field of plasma gas discharges cannot directly implement protection designs for the high-voltage output interface due to the extremely high voltage and current rates they output. In particular, overcurrent protection functions struggle to achieve rapid power cutoff, rendering them incapable of protecting the entire system. Furthermore, the pulse voltage output by the power supply generally requires a very high and adjustable frequency, such as varying within a range of 1Hz to 10kHz. This requires the overcurrent protection circuit to have wide frequency compatibility and excellent resistance to high-frequency noise interference. Furthermore, the power supply topology based on the Marx generator utilizes a large number of semiconductor switching devices. Designing a protection circuit for each switching device would complicate the design of the entire overcurrent protection circuit, reduce the performance of the protection circuit, and make it difficult to provide overcurrent protection for all semiconductor switching devices.

[0003] Currently, pulse power technology is developing rapidly, and nanosecond pulse power supplies based on Marx generator technology have garnered widespread attention and recognition. However, numerous challenges remain in their application, requiring further optimization. Research on nanosecond pulse power supplies based on Marx generator technology involves multiple aspects, including semiconductor devices, control methods, and topology. To achieve fast rising edges and stable pulse output, fully controlled devices such as IGBTs and SiC-MOSFETs are used as switches to isolate capacitor charging and discharging. However, when the output is short-circuited, the pulse current flowing through the switching device far exceeds its tolerance. Therefore, the design of overcurrent protection circuits is particularly important.

[0004] Currently, research on the design of current-limiting and short-circuit protection circuits for Marx pulse generators is divided into two main directions: one is protection design for semiconductor switching devices such as IGBTs, and the other is protection design starting from the output end. Switching transistor protection is mainly achieved by designing a passive protection circuit for the switching tube. When an overcurrent occurs, the gate voltage of the switching transistor is clamped, thereby achieving soft shutdown of the semiconductor switching device. Overcurrent detection at the output end mainly uses pulse current detection technology to detect whether there is an overcurrent phenomenon. Once an overcurrent is detected, the circuit is immediately disconnected to protect the switching tube.

[0005] The currently used overcurrent-short-circuit protection scheme requires a relatively long protection reaction time, at least on the order of μs, which may cause overcurrent damage to the switching transistor and is not suitable for nanosecond pulse power supplies. When the load is inductive or capacitive, the instantaneous current value will exceed the preset current limit point of the power supply when the power supply is started or shut down, causing the overcurrent protection circuit to malfunction.

[0006] Overcurrent-short-circuit protection methods disclosed in patents such as CN112821349A, CN111490687A, and CN106026010B, on the one hand, require a long reaction time for the protection circuit, making them unsuitable for nanosecond pulse power supplies. On the other hand, by presetting the overcurrent value in the circuit, the power supply automatically disconnects when the output current reaches the overcurrent value. However, the output current amplitude varies with the load connected to the power supply, requiring constant adjustment of the set overcurrent threshold, which is very complicated. Moreover, these overcurrent-short-circuit protection methods cannot handle the condition of a normal short circuit at the output end.

[0007] Moreover, when the nanosecond pulse power supply outputs low-frequency pulse power, the output voltage will be zero, resulting in the problem that the short-circuit state of the output cannot be accurately judged. Summary of the Invention

[0008] 1. Technical problems to be solved:

[0009] Most of the existing overcurrent protection scheme designs of nanosecond pulse power supplies based on Marx generators are difficult to cope with the working conditions of long-term short circuit at the output end. They only have current limiting protection function and cannot realize the whole machine shutdown function.

[0010] 2. Technical solution:

[0011] In order to solve the above problems, the present invention provides

[0012] A Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system includes a current limiting module and an automatic quick-cut module. The current limiting module is integrated into the main circuit of the Marx generator to limit the current amplitude, protect the switch tube from damage in a relatively short time, and provide sufficient time for the subsequent overcurrent protection module to operate. The automatic quick-cut module is arranged at the output end of the nanosecond pulse power supply and includes a short-circuit detection unit, a protection logic processing unit, and a protection action unit. The short-circuit detection unit detects whether the output end voltage of the Marx pulse generator is zero to determine whether a short circuit has occurred. The protection logic processing unit distinguishes between short-circuit conditions and normal conditions to prevent the zero output end voltage of the Marx generator during normal operation from being mistaken for a short circuit. The protection action unit turns off the gate signal of the distribution switch when a short-circuit condition is determined.

[0013] The current limiting module includes a non-inductive resistor connected in series, and the source of each voltage-driven switching device is connected in series with a non-inductive resistor R1~R n , adopts constant voltage driving mode, and the driving voltage is the sum of the gate-source voltage and the resistor voltage divider.

[0014] The method for determining the inductor resistance is as follows: note the resistance R i ~R n The resistance is R, and its size must satisfy the constraints of two inequalities:

[0015] U G -I O R>U GS (th)

[0016] U G -I max R≤U GS (th), where U G — is the output voltage of the constant voltage drive; I O — is the output current when the circuit is working normally; U GS(th) — is the turn-on voltage of the switch tube; I max — is the maximum pulse current that the switch tube can withstand, that is, the maximum current allowed to pass through the circuit. When the IGBT flows through the short-circuit current:

[0017]

[0018] Where: β PNP — is the common emitter gain of the parasitic PNP transistor of the IGBT; μ ns — is the average mobility of electrons in the channel; C ox — is the oxide capacitance per unit area; Z— is the channel width; L CH — is the channel length; U th — is the gate-emitter threshold voltage. The short-circuit current formula is linearized: I SC =G fs (U ge -U′ th ) where U' th This is the equivalent gate turn-on voltage after linearization of the transfer characteristic curve. According to the transfer characteristic curve in the data sheet, when a resistor is connected in series with the source, I SC =G fs (U GS -U′ th )=G fs (U G -I SC RU′ th ), we can deduce that:

[0019] I SC Should be less than the maximum pulse current I that the switch tube can withstand max Right now:

[0020] The constraint relationship of the resistor R is as follows:

[0021] The size of the resistor R is determined according to the above relationship.

[0022] The short-circuit detection unit determines the high and low level states of the output end of the optocoupler chip by the operating state of the high-voltage silicon stack when the power supply is running, thereby judging whether the output end of the Marx pulse generator is short-circuited. Specifically, when the power supply is operating normally, the high-voltage silicon stack is in the cut-off state. At this time, the current flows through the diode of the optocoupler chip, and the chip is turned on. At this time, the output end of the short-circuit detection is low level; when the power supply is short-circuited, the high-voltage silicon stack diode is in the on state. Due to the presence of the voltage regulator tube Z, the voltage of the negative electrode on the input side of the optocoupler chip is clamped, so that the light-emitting diode at the input end of the optocoupler chip is in the cut-off state. At this time, the output end detection circuit will output a high level. According to the state of the output end of the short-circuit detection circuit, it is judged whether the power supply is operating normally.

[0023] The protection logic processing unit introduces the switch tube drive signal S and combines the two signals S2 and S1 to distinguish between short-circuit conditions and normal conditions. Specifically, when the power supply is in normal working condition, the high and low levels of the two are staggered. When a short circuit occurs, the short-circuit detection signal S1 remains at a high level. The protection logic processing unit is set to activate short-circuit protection when signals S1 and S2 are simultaneously at a high level.

[0024] It also includes an RS holding circuit, which immediately latches the fault signal once a short circuit overcurrent occurs, so that the protection can operate reliably in the event of a short circuit overcurrent.

[0025] When the fault signal OUT is at a high level, the transistor of the protection action unit is turned on, and after the relay coil is energized, the normally closed auxiliary switch thereof is controlled to be turned off, thereby turning off the gate signal of the distribution switch.

[0026] 3.Beneficial effects:

[0027] The invention adopts a protection strategy that combines current limiting and short-circuit protection. It not only provides overcurrent protection, but also quickly cuts off the power input of the circuit when the output end is short-circuited, fundamentally protecting the switch tube from damage. Moreover, the current limiting module of the present invention is passive protection, with simple parameter design and good economic efficiency. The present invention performs AND logic processing on the digital output signal of the short-circuit detection unit and the drive signal of the discharge switch transistor of the Marx topology to accurately determine whether the power output end is actually in a short-circuit state, and can automatically and quickly cut off the protection module circuit to control the distribution switch of the charging energy storage power supply to protect the power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is the overall framework diagram of the overcurrent protection system.

[0029] Figure 2 This is the output characteristic diagram of the N-channel enhancement MOS tube.

[0030] Figure 3 This is the current limiting protection structure diagram of the nth switching tube.

[0031] Figure 4 It is a linear fitting diagram.

[0032] Figure 5 This is the schematic diagram of the short-circuit detection circuit.

[0033] Figure 6 This is the current flow diagram when the power supply is outputting normally.

[0034] Figure 7 This is a diagram of current flow when the power supply is short-circuited.

[0035] Figure 8 This is the principle block diagram of the automatic quick-cut protection module.

[0036] Figure 9 is a timing diagram of signals S1 and S2.

[0037] Figure 10 Schematic diagram of the protection action unit circuit.

[0038] Figure 11 This is the topology diagram of the nanosecond pulse power supply circuit without adding a current limiting resistor.

[0039] Figure 12 This is a schematic diagram of the drain current of SiC MOSFET when the output terminal is short-circuited.

[0040] Figure 13 This is the topology diagram of the nanosecond pulse power supply circuit with added current limiting resistors

[0041] Figure 14 This is a schematic diagram of the drain current of SiC MOSFET after adding a current limiting resistor.

[0042] Figure 15 It is a fault signal generating circuit.

[0043] Figure 16 It is the power supply waveform.

[0044] Figure 17 It simulates a sudden short circuit during normal operation.

[0045] Figure 18 This is the S1 waveform when a short circuit occurs suddenly under normal conditions.

[0046] Figure 19 This is a schematic diagram of the AND gate output and latch output. DETAILED DESCRIPTION

[0047] The present invention will be described in detail below with reference to the accompanying drawings.

[0048] like Figure 1 As shown, the present invention provides a Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system including a current limiting module and an automatic quick-cut module. The current limiting module is integrated in the main circuit of the Marx generator. Through reasonable parameter design, when overcurrent occurs, the semiconductor switch tube (MOSFET, IGBT, etc.) can be transferred from the constant current area to the variable resistance area, thereby limiting the large current in the loop. The function of the current limiting module is to limit the current amplitude, protect the switch tube from damage in a relatively short time, and provide sufficient time for the subsequent overcurrent protection module to operate. The automatic quick-cut module is used to deal with the situation of a long-term short circuit at the output end, and it includes a short-circuit detection unit, a protection logic processing unit, and a protection action unit. A fault signal is generated by detecting whether the output end of the Marx generator is short-circuited, and an action signal is generated after signal processing, and finally the disconnection of the distribution switch of the main power circuit is controlled.

[0049] The present invention analyzes the characteristics of the switching transistor device and adds a current sampling resistor to the source (emitter) of the switching transistor. When a short circuit occurs in the circuit or under high current conditions, the voltage on the current sampling resistor is instantly increased, thereby reducing the switching transistor U GS The driving voltage amplitude allows the switching transistor to enter the linear constant current working area in a short time of overcurrent state, and the equivalent impedance R between the drain and source of the transistor DS_ON It becomes larger instantly, thus playing the role of automatic current limiting of the series discharge circuit of the Marx topology, achieving the purpose of protecting the entire power supply.

[0050] At the same time, in order to solve the problem that the current limiting module cannot cope with the normal short circuit, an automatic fast-cut module is added to the output end of the nanosecond pulse power supply. The proposed high-speed short-circuit detection circuit can quickly detect whether the output end of the nanosecond pulse power supply is in a normal short-circuit state.

[0051] When the nanosecond pulse power supply outputs low-frequency pulse power, the output voltage will be zero, resulting in the problem that the short-circuit state of the output end cannot be accurately judged. It is proposed to combine the output signal of the short-circuit state detection circuit with the switching transistor drive signal to jointly judge whether the nanosecond pulse power supply is in a short-circuit state under actual circumstances.

[0052] Compared to existing overcurrent protection schemes for nanosecond pulse power supplies based on Marx generators, most of these schemes struggle to cope with long-term output short-circuit conditions, providing only current limiting protection but failing to achieve full system shutdown. The present invention employs a combined current limiting and short-circuit protection strategy, not only providing overcurrent protection but also rapidly shutting off the circuit's power input in the event of an output short-circuit, fundamentally protecting the switching transistor from damage. Furthermore, the current limiting module of the present invention employs passive protection, resulting in simple parameter design and excellent economical performance.

[0053] Figure 2 This is the output characteristic of an N-channel enhancement-mode MOS transistor, which can switch between constant current, cutoff, and variable resistance regions. Typically, MOSFETs are designed to switch between the constant current and cutoff regions during operation. Generally, this is done by simply controlling the on / off of the switch, switching between the constant current and cutoff regions, thereby achieving the pulsed voltage output of the Marx pulse generator. When the switch operates in the non-saturated region, it acts like a resistor whose resistance varies with the characteristics. The increase in the equivalent resistance in the circuit naturally acts as a current limiter.

[0054] Figure 3 In order to design a current limiting protection scheme, a small non-inductive resistor R1~R n , and adopts constant voltage drive mode, the drive voltage is the sum of the gate source voltage and the resistor voltage divider. According to the actual parameters of the pulse power supply, the size of the non-inductive resistor in series is reasonably designed. The power supply is not affected by the resistors R1 to R n Once the output end is broken, the current flowing through the switch tube increases. At this time, the resistors R1 to R n The increase in the voltage divider will reduce the voltage between the corresponding switch gate and source, and the current in the loop will naturally be clamped at a lower level.

[0055] A suitable current sampling resistor is connected in series to the source of each discharge switch transistor to establish a responsive adaptive current limiting parameter model, thereby dynamically reducing the transistor drive voltage U GS The ability to realize adaptive current limiting function in the discharge stage.

[0056] When the drain current is large, the transconductance G fs represents the drain current i DWith the gate-source voltage U GS The relationship between the transconductance G fs According to the transfer characteristic curve in the data sheet of the switch tube, D A linear fit is performed over a larger range.

[0057] According to feasibility analysis, the source resistor in series must first meet the requirements that under normal operation, the resistor voltage division will not affect the normal opening of the switch tube, and secondly, it must meet the requirements that once the circuit overcurrent occurs, the switch tube can enter the variable resistance area. n The resistance is R, and its size must satisfy the constraints of two inequalities:

[0058] U G -I O R>U GS (th)

[0059] U G -I max R≤U GS (th)

[0060] in,

[0061] U G — is the output voltage of the constant voltage drive;

[0062] I0—is the output current when the circuit is working normally;

[0063] U GS(th) — is the turn-on voltage of the switch tube;

[0064] I max —The maximum pulse current that the switch tube can withstand, that is, the maximum current allowed to pass through the circuit.

[0065] When a short-circuit current flows through the IGBT:

[0066]

[0067]

[0068] Where: β PNP — is the common emitter gain of the parasitic PNP transistor of the IGBT; μ ns — is the average mobility of electrons in the channel;

[0069] C ox — is the oxide capacitance per unit area; Z— is the channel width

[0070] L CH — is the channel length; U th — is the gate-emitter threshold voltage.

[0071] In order to clearly obtain the relationship between the short-circuit current and the gate voltage of the switch tube, the short-circuit current formula is linearized, as shown in the following example: Figure 4 As shown, there are:

[0072] I SC =G fs (U ge -U′ th )

[0073] where U' th This is the equivalent gate turn-on voltage after linearizing the transfer characteristic curve. Based on the transfer characteristic curve in the datasheet and the current limiting design of this solution, when a resistor is connected in series with the source, the following is true:

[0074] I SC =G fs (U GS -U′ th )=G fs (U G -I SC RU′ th )

[0075] It can be deduced that:

[0076]

[0077] It can be seen that I SC Should be less than the maximum pulse current I that the switch tube can withstand max Right now:

[0078]

[0079] Therefore, the constraint relationship of the resistor R can be obtained as follows:

[0080]

[0081] Therefore, the size of the resistor R can be determined based on the above relationship. In addition, based on the principle of minimum loss and minimum impact on normal operation, a smaller R value should be selected as much as possible.

[0082] Figure 5 This is the schematic diagram of the short-circuit detection circuit. The function of the short-circuit detection circuit is to determine the high and low level states of the output end of the optocoupler chip by the operating state of the high-voltage silicon stack when the power supply is running, thereby judging whether the output end of the Marx pulse generator is short-circuited.

[0083] When the power supply is operating normally, Figure 6 As shown, the high-voltage silicon stack is in the cut-off state. At this time, the current flows through the diode of the optocoupler chip, and the chip is turned on. At this time, the output end of the short-circuit detection is low level;

[0084] When the power supply is short-circuited, Figure 7 As shown in the figure, the high-voltage silicon stack diode is in the on state. Due to the presence of the voltage regulator Z, the voltage at the negative electrode of the optocoupler chip input side is clamped, causing the light-emitting diode at the input end of the optocoupler chip to be in the off state. At this time, the output detection circuit will output a high level. The state of the output end of the short-circuit detection circuit can be used to determine whether the power supply is operating normally.

[0085] When the circuit is short-circuited, Figure 7 As shown, the high-voltage silicon stack is in the on state.

[0086] The high-speed short-circuit state detection circuit at the high-voltage pulse power output end of the high-voltage silicon stack combined with the optocoupler detection circuit can reliably detect whether the high-voltage pulse power supply is in a normal short-circuit state, and output an isolated weak current characterization detection signal with strong anti-noise interference capability.

[0087] In order to deal with the problem of normal short circuit at the output end that cannot be solved by the current limiting scheme, an automatic fast-cut protection module is proposed, such as Figure 8 As shown in the figure, it primarily consists of a short-circuit detection circuit, an RS signal holding circuit, and an action circuit. The short-circuit detection circuit monitors the Marx pulse generator to determine whether a short circuit has occurred. Furthermore, since the output voltage is a pulse signal, the Marx generator may experience zero output voltage during normal operation. To prevent malfunction of the short-circuit protection in this situation, a switch drive signal S2 is introduced. By combining these two signals with S1, the short-circuit condition can be distinguished from the normal operating condition.

[0088] In addition, since the output voltage is a pulse signal, the Marx generator may also have a zero output voltage during normal operation. To avoid malfunction of the short-circuit protection in this case, a switch drive signal S2 is introduced. By combining the two signals S2 and S1, the short-circuit condition can be distinguished from the normal condition.

[0089] The digital output signal of the short-circuit detection unit and the driving signal of the Marx topology discharge switch transistor are processed by AND logic to accurately determine whether the power output end is actually in a short-circuit state. The automatic fast-cut protection module circuit of the present invention controls the distribution switch of the charging energy storage power supply to turn off, thereby protecting the power supply.

[0090] Figure 9 This is a timing diagram of signals S1 and S2. When the power supply is in normal working condition, the high and low levels of the two are staggered. When a short circuit occurs, the short circuit detection signal S1 remains high. Therefore, the protection logic is set to activate short circuit protection when signals S1 and S2 are high at the same time.

[0091] It is proposed to combine the short-circuit state signal of the power supply output end and the discharge switch transistor drive signal of the Marx topology into the output short-circuit state judgment condition, which solves the problem of misjudgment of the output end being at a low level under low-frequency nanosecond pulse output conditions.

[0092] When designing the circuit, S1 and S2 are passed through the AND gate to generate a signal indicating whether a short circuit fault has occurred. To avoid interference and ensure that the protection can reliably operate in the event of a short circuit overcurrent, it is necessary to design an RS holding circuit to latch the fault signal immediately once a short circuit overcurrent occurs.

[0093] Last passed Figure 9 The action protection circuit shown in the figure, when the fault signal OUT is high, Figure 9 The transistor shown is turned on, and after the relay coil is energized, it controls its normally closed auxiliary switch to be turned off, thereby turning off the gate signal of the distribution switch, ultimately protecting the power supply.

[0094] In order to verify the effectiveness of the solution of the present invention, simulation experiments and verification analysis of the current limiting module and the automatic fast switching module were carried out using Saber simulation software. Figure 11 This is a simulation circuit for a nanosecond pulse power supply without a current limiting resistor. The DC input voltage is set to 1000V during simulation. Each Marx unit consists of a 100nF capacitor, two diodes, and a SiC MOSFET model C2M0080120D, thus forming a four-stage Marx circuit. By directly short-circuiting the output terminal, the oscilloscope system in Saber can be used to observe the drain current waveform of the SiC MOSFET. Figure 11 As shown in the figure, without any protection, the SiC MOSFET will continue to withstand a continuous pulse current of 112.5A, and the MOSFET will be damaged.

[0095] During the simulation experiment, by short-circuiting the output terminal directly, the oscilloscope system in Saber can be used to observe the drain current waveform of SiCMOSFET. Figure 12 As shown in the figure, without any protection, the SiC MOSFET will continue to withstand a continuous pulse current of 112.5A, and the MOSFET will be damaged.

[0096] In response to the above overcurrent situation, a resistor is connected in series with the source of SiC MOSFET. Figure 13 The overcurrent scheme circuit is constructed and the R selected during the scheme verification simulation is given. e The resistance is 0.1Ω.

[0097] Figure 14After adding the current limiting resistor, the drain circuit of the SiC MOSFET is shown when the output end is short-circuited. It can be seen that compared with 100A without current limiting measures, the drain current is clamped to 50A, which effectively protects the MOS tube.

[0098] The simulation results demonstrate the feasibility of the overcurrent protection scheme proposed in the previous section. The above analysis shows that when the output is short-circuited, without a current-limiting resistor, the current flowing through the SiC MOSFET can reach approximately 100A. However, by adding a series source resistor, the current through the SiC MOSFET is clamped to approximately 50A, significantly protecting the MOSFET. Furthermore, due to the low resistance of the series resistor, the resulting losses are also minimal. The output current of the pulse power supply during normal operation is much lower than during a short-circuit. Therefore, the clamping effect of the resistor is minimal during normal operation and does not affect the normal operation of the power supply.

[0099] The short-circuit detection circuit detects the output of the power supply in different working states, and then further analyzes it in combination with the fault signal trigger circuit. Figure 15 It is a fault signal generating circuit. The power supply "shuchu" simulates the output signal of the short-circuit detection circuit when the Marx pulse generator works normally; the power supply "pwm" simulates the PWM waveform of the switch tube drive signal; the power supply "guzhang" simulates the output signal of the short-circuit detection circuit when the output end of the Marx pulse generator is short-circuited. Its waveform is shown in the figure below. Figure 16 shown.

[0100] The simulated working condition of this simulation experiment is that the load at the output end of the Marx pulse generator is normal within 0~5ms, and the response of the fault signal generating circuit after the load is suddenly short-circuited at 5ms. Figure 17 The circuit structure shown simulates the waveform of the short circuit detection signal S1 during this period of time. The waveform of S1 is as follows: Figure 18 As shown:

[0101] AND gate output and latch output, such as Figure 19 As shown:

[0102] Among them: pwm is the drive signal S2, n_710 is the short-circuit detection output signal S1, n_614 is the AND gate output, and n_685 is the RS latch output.

[0103] As can be seen, the Marx pulse generator operates normally from 0 to 5 ms. During this time, the AND gate output S3 remains low, the latch output is also low, and the relay does not operate. At 5 ms, the Marx pulse generator load suddenly shorts, causing the short-circuit detection signal S1 (n_710) to remain high. As soon as the PWM drive signal S2 (pwm) reaches a high level, meaning the transistor is turned on, the AND gate output (n_614) immediately changes to 1, and the latch registers the fault state. Its (n_685) output becomes high, acting as a fault signal, which is fed into the actuation circuit to control the relay's operation. This ultimately achieves automatic quick-cut functionality.

[0104] The final experimental test results verified the feasibility of the overcurrent protection scheme composed of the current limiting protection module and the automatic fast-cut module proposed in the present invention.

[0105] The present invention can not only realize the short-circuit fault protection function, but also has the adaptive current limiting function of transient pulse large current, thereby ensuring the safety of power supply output; it has a wide frequency applicability and very good resistance to high-frequency noise interference; it realizes protection action through simple discrete components and basic logic gate circuits, and there is no need to design a protection circuit for each switching device in the power supply. The circuit is simple, the cost is low, and it is conducive to promotion.

Claims

1. A Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system, characterized by: It includes a current limiting module and an automatic quick-cut module. The current limiting module is integrated in the main circuit of the Marx generator to limit the current amplitude, protect the switch tube from damage, and provide time for the subsequent overcurrent protection module to operate; the automatic quick-cut module is set at the output end of the nanosecond pulse power supply, and includes a short-circuit detection unit, a protection logic processing unit and a protection action unit. The short-circuit detection unit detects whether the output voltage of the Marx pulse generator is zero to determine whether a short circuit occurs; the protection logic processing unit distinguishes between short-circuit conditions and normal conditions to avoid the situation where the output voltage of the Marx generator is zero during normal operation being mistaken for a short circuit; the protection action unit turns off the gate signal of the distribution switch when the short-circuit condition is determined. The current limiting module includes a series-connected non-inductive resistor, and the source of each voltage-driven switching device is connected in series with a non-inductive resistor R1~R n , using a constant voltage drive mode, the driving voltage is the sum of the gate-source voltage and the resistor voltage divider. The method for determining the non-inductive resistor is: record the resistors R1~R n The resistance is R, and its size must satisfy the constraints of two inequalities: U G -I O R>U GS (th) U C -I max R≤U GS (th), where U G — is the output voltage of the constant voltage drive; I O — is the output current when the circuit is working normally; U GS(th) — is the turn-on voltage of the switch tube; I max — is the maximum pulse current that the switch tube can withstand, that is, the maximum current allowed to pass through the circuit. When the IGBT flows through the short-circuit current: Where: β PNP — is the common emitter gain of the parasitic PNP transistor of the IGBT; μ ns — is the average mobility of electrons in the channel; C ox — is the oxide capacitance per unit area; Z— is the channel width; L CH — is the channel length; U th — is the gate-emitter threshold voltage, and the short-circuit current formula is linearized: AND SC =G fs (IN ge -IN' th ) where U' th This is the equivalent gate turn-on voltage for linearizing the transfer characteristic curve. According to the transfer characteristic curve in the data sheet, when a resistor is connected in series with the source, the voltage is: I SC = G fs (U GS - U') th ) = G fs (U G - I SC R - U') th Derived: I SC Should be less than the maximum pulse current I that the switch tube can withstand max Right now: The constraint relationship of the resistor R is as follows: The size of the resistor R is determined according to the above relationship.

2. The Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system according to claim 1, characterized in that: The short-circuit detection unit determines the high and low level states of the output end of the optocoupler chip by the operating state of the high-voltage silicon stack when the power supply is running, thereby judging whether the output end of the Marx pulse generator is short-circuited. Specifically, when the power supply is operating normally, the high-voltage silicon stack is in the cut-off state. At this time, the current flows through the diode of the optocoupler chip, and the chip is turned on. At this time, the output end of the short-circuit detection is low level; when the power supply is short-circuited, the high-voltage silicon stack diode is in the on state. Due to the presence of the voltage regulator tube Z, the voltage of the negative electrode on the input side of the optocoupler chip is clamped, so that the light-emitting diode at the input end of the optocoupler chip is in the cut-off state. At this time, the output end detection circuit will output a high level. According to the state of the output end of the short-circuit detection circuit, it is judged whether the power supply is operating normally.

3. The Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system according to claim 1, characterized in that: The protection logic processing unit introduces the switch tube drive signal S2, and combines the two signals S2 and S1 to distinguish between short-circuit conditions and normal conditions. Specifically, when the power supply is in normal working condition, the high and low levels of the two signals are staggered. When a short circuit occurs, the short-circuit detection signal S1 remains at a high level. The protection logic processing unit is set to short-circuit protection when signals S1 and S2 are simultaneously at a high level.

4. The Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system according to claim 1, characterized in that: It also includes an RS holding circuit that latches the fault signal immediately once a short circuit overcurrent occurs.

5. The Marx topology nanosecond pulse power supply adaptive current limiting short-circuit protection system according to claim 1, characterized in that: When the fault signal OUT is at a high level, the transistor of the protection action unit is turned on, and after the relay coil is energized, the normally closed auxiliary switch thereof is controlled to be turned off, thereby turning off the gate signal of the distribution switch.

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