MARX generator protection circuit with adjustable ignition pulse width

Abstract

The utility model provides an ignition pulse width adjustable MARX generator protection circuit, and belongs to the technical field of electric vacuum emission, the protection circuit comprises a sampling circuit, the sampling circuit comprises a current transformer and a sampling resistor R1, the current transformer is arranged between a high-voltage ignition signal generated by an MARX generator and a load, and the sampling resistor R1 is arranged on a secondary winding of the circuit transformer; the comparison circuit comprises a comparator, a first resistor R2 and a second resistor R3, the same-direction end of the comparator is connected with the current transformer, the reverse-direction end of the comparator is connected with a voltage division network formed by the first resistor and the second resistor, and the comparison circuit is used for comparing the sampling voltage of the high-voltage ignition signal with a set protection threshold voltage; the pulse width adjusting circuit comprises a monostable multivibrator, a third resistor and a capacitor, and the monostable multivibrator is grounded through a resistance-capacitance network formed by the capacitor and the third resistor; and the control circuit is connected with the pulse width adjusting circuit.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric vacuum emission, and particularly relates to a MARX generator protection circuit with adjustable spark pulse width. BACKGROUND

[0002] With the development of electric vacuum emission equipment towards miniaturization and high power, the required pulse modulator needs to be smaller in size and higher in voltage grade. At present, the pulse modulator mainly realizes the output of high-voltage pulses through two ways: one is the pulse transformer scheme, which relies on an ultra-high transformer turns ratio to obtain the pulse high voltage required by the cathode of an electric vacuum device; the other is the MARX generator scheme, which realizes the step-by-step superposition output of pulse voltage through the principle of parallel charging and series discharging of capacitors, and obtains the pulse high voltage required by the cathode of an electric vacuum device.

[0003] Although the high-voltage transformer scheme has a relatively simple principle and requires fewer power semiconductor devices that are not easy to damage, it occupies a relatively large volume to meet the miniaturization requirement, and due to the very high turns ratio, the parasitic parameters (such as leakage inductance and parasitic capacitance) are very large, which will cause excessively high peak voltage and strong electromagnetic interference problems during pulse operation.

[0004] The MARX generator scheme controls the volume within a relatively small range because it does not require a large high-voltage pulse transformer due to the principle of parallel charging and series discharging of capacitors. However, the semiconductor switching devices used in the MARX scheme are prone to damage in the case of high-voltage sparking, so a MARX generator protection circuit is needed in the case of high-voltage sparking.

[0005] The existing MARX generator protection circuit under high-voltage sparking samples the high-voltage sparking current through a current transformer, then converts the current sampling signal into a voltage signal, and compares it with the set protection threshold. When working normally, the comparator outputs a low level, and the control circuit displays a normal working state. When high-voltage sparking occurs, the cathode current will rapidly increase, the current sampling signal of the current transformer will instantaneously become large, exceeding the set protection threshold, and the comparator sends out a high level. This signal is sent to the control circuit, which quickly cuts off the control pulse to prevent the output of pulse high voltage, thereby controlling the high-voltage sparking current of the circuit and protecting the semiconductor devices in the working circuit. However, the high-voltage sparking pulse is usually narrow, and the high level output by the comparator in the existing protection circuit has a relatively short maintenance time. In extreme cases, the control circuit does not have time to respond before the high level of the comparator disappears, and the pulse control signal continues to be output, resulting in the damage of semiconductor devices. SUMMARY

[0006] The purpose of the present application is to provide a MARX generator protection circuit with adjustable ignition pulse width to solve or alleviate at least one problem in the background art.

[0007] The technical solution of the present application is: a MARX generator protection circuit with adjustable ignition pulse width, comprising:

[0008] A sampling circuit comprising a current transformer and a sampling resistor R1, the current transformer being arranged between a high-voltage ignition signal generated by the MARX generator and a load, and the sampling resistor R1 being arranged in the secondary winding of the current transformer, the sampling circuit being used to sample the high-voltage ignition signal to generate a sampling voltage;

[0009] A comparison circuit comprising a comparator and first and second resistors R2 and R3, the same direction end of the comparator being connected to the current transformer, and the opposite direction end being connected to a voltage dividing network comprising the first and second resistors, the comparison circuit being used to compare the sampling voltage of the high-voltage ignition signal with a set protection threshold voltage, and output a high-level pulse signal of a first width when high-voltage ignition occurs;

[0010] A pulse width adjustment circuit, the pulse width adjustment module comprising a monostable multivibrator, a third resistor and a capacitor, the monostable multivibrator being grounded through a resistor-capacitor network comprising the third resistor and the capacitor, and the pulse width of the high-voltage pulse signal being adjusted to output a high-voltage pulse signal of a second width when the comparison circuit outputs a high-voltage pulse signal of the first width is detected;

[0011] A control circuit connected to the pulse width adjustment circuit, the control circuit being used to cut off the pulse control signal of the MARX generator and turn off the high-voltage pulse output when a high-voltage pulse signal of the second width output by the pulse width adjustment circuit is detected, so as to protect the semiconductor components of the MARX generator.

[0012] In an optional embodiment of the present application, the high-voltage ignition signal is a current signal, and the high-voltage ignition signal sampled by the current transformer is converted into a voltage signal through the sampling resistor R1.

[0013] In an optional embodiment of the present application, the protection threshold voltage is adjusted by adjusting the resistance values of the first resistor R2 and the second resistor R3.

[0014] In an optional embodiment of the present application, the first width is tens of nanoseconds to hundreds of nanoseconds.

[0015] In an optional embodiment of the present application, the second width is greater than the first width, and the second width Tw is proportional to R*C, where R is the resistance value of the third resistor Rt, and C is the capacitance value of the capacitor Ct.

[0016] The MARX generator protection circuit with adjustable ignition pulse width provided in the present application can prevent the high-voltage ignition signal from not being recognized, and continuing to ignite when the next high-voltage ignition pulse arrives, thereby damaging the semiconductor devices in the MARX circuit, thereby greatly reducing the probability of damage to semiconductor devices due to high-voltage ignition and improving the reliability of the MARX generator. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions provided by this application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of this application.

[0018] Figure 1 This is a schematic diagram of a MARX circuit commonly used in vacuum devices.

[0019] Figure 2 This is a schematic diagram of the protection circuit of the MARX generator with adjustable ignition pulse width of this application. DETAILED DESCRIPTION

[0020] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0021] like Figure 1 The following diagram shows the circuit diagram of a MARX generator commonly used in vacuum devices. The MARX generator consists of multiple charge-discharge units, including a front diode D11, a rear diode D12, and a capacitor C1 and a switch Q1 connected in parallel between the front and rear diodes. Before a drive pulse arrives, the front-stage power supply Vin charges the capacitors C1 through Cn in the charge-discharge units through the inductor L. When the pulse arrives, the switches Q1 through Qn turn on simultaneously, discharging the capacitors in series. The voltage applied to the load is now n times the input voltage: nVin (ignoring the diode voltage drop). The load pulse width is controlled by the drive pulse. This generates a high-voltage modulated pulse that meets the operating requirements of vacuum devices.

[0022] In order to effectively protect the semiconductor device when striking, the common practice is to connect a current transformer in series in the load circuit. When high-voltage striking occurs, the current transformer samples the current signal of the over-load, converts it into a voltage signal through a resistor, and inputs it into the same phase end of a comparator. The voltage signal is compared with the protection threshold input into the opposite phase end of the comparator. When the sampled voltage signal is higher than the protection threshold during high-voltage striking, the comparator outputs a high level, which is sent to the control circuit. The control circuit quickly cuts off the high-voltage pulse to limit the striking current and protect the switch tube. However, since the striking signal is a transient signal, the pulse is usually narrow, and the high level output by the comparator is maintained for a very short time. In some conditions, the control circuit cannot identify the high level, and cannot cut off the high-voltage pulse in time, resulting in continuous striking of the converter or damage to the switch tube.

[0023] In order to solve the problem that the pulse is too narrow during high-voltage striking, the high level of the comparator is maintained for a very short time, the control circuit fails to identify the fault signal, and the output high-voltage pulse cannot be cut off in time, resulting in damage to the semiconductor device, the application provides a MARX generator protection circuit with adjustable striking pulse width.

[0024] As shown in Figure 2 The MARX generator protection circuit with adjustable striking pulse width provided by the application comprises a sampling circuit 10, a comparison circuit 20, a pulse width adjusting circuit 30 and a control circuit 40.

[0025] The sampling circuit 10 comprises a current transformer and a sampling resistor R1. The current transformer is arranged between the high-voltage striking signal HV of the cathode of the MARX generator and the load. The high-voltage striking signal line of the cathode of the MARX generator passes through the current transformer to form the primary of the current transformer. The sampling resistor R1 is arranged in the secondary of the current transformer, and is used to form a loop in the secondary of the current transformer, so as to facilitate sampling of the high-voltage striking signal and converting the sampled current signal into a voltage signal.

[0026] The comparison circuit 20 comprises a comparator and a first resistor R2 and a second resistor R3. The same direction end of the comparator is connected to the current transformer of the sampling circuit 10. The opposite direction end of the comparator is connected to the first resistor R2 and the second resistor R3 to form a voltage dividing network for forming a protection threshold voltage. The comparator compares the sampling voltage of the high-voltage striking signal on the sampling resistor R1 with the protection threshold voltage formed by the voltage dividing network. When the sampling voltage is lower than the protection threshold voltage, the comparator outputs a low level pulse signal, and the protection circuit works normally. When high-voltage striking occurs, the sampling voltage will instantaneously increase and exceed the set protection threshold voltage, and the comparator outputs a relatively narrow high level pulse signal. Usually, the relatively narrow high level pulse signal is in the order of nanoseconds, and is between tens of nanoseconds and hundreds of nanoseconds.

[0027] It should be noted that the protection threshold voltage is obtained by dividing the auxiliary power voltage Vcc by the first resistor R2 and the second resistor R3 in the present application, and thus the appropriate protection threshold voltage can be obtained by controlling the resistance values of the first resistor R2 and the second resistor R3, which is smaller than the sampling voltage during high voltage sparking and larger than the sampling voltage during no high voltage sparking.

[0028] The pulse width adjusting circuit 30 comprises a monostable multivibrator (also called monostable flip-flop) and a third resistor Rt and a capacitor Ct, which constitute a bridge between the comparison circuit and the control circuit, and are used for converting the narrow pulse signal output by the comparator into a wide pulse signal which can be accurately recognized by the control circuit 40. The pulse width output by the pulse width adjusting circuit 30 is larger than the pulse width output by the comparator circuit 20, which is realized by adjusting the resistance value of the third resistor Rt and / or the capacitance value of the capacitor Ct, satisfying the formula of pulse width T∝R*C, wherein R is the resistance value of the third resistor Rt and C is the capacitance value of the capacitor Ct.

[0029] The control circuit 40 is arranged at the rear side of the pulse width adjusting circuit 30, and when the output of the monostable multivibrator is detected as low level, the pulse control signal is normally output; when the output of the monostable multivibrator is detected as high level of wide pulse, the pulse control signal is quickly turned off, and the high voltage pulse is stopped from being output, thereby playing a role of protecting the semiconductor components.

[0030] The high voltage sparking pulse width adjustable MARX generator protection circuit provided by the present application is based on the conventional high voltage sparking protection circuit, and by increasing the monostable multivibrator and reasonably configuring the external resistance and capacitance parameters, the narrow pulse signal generated by high voltage sparking which is not easily recognized by the control circuit is converted into a wide pulse signal which is more easily recognized by the control circuit and has adjustable pulse width, thereby avoiding the situation that the high voltage sparking signal in the protection circuit is not recognized, and the high voltage sparking pulse comes again to continue sparking, and thus the semiconductor components in the MARX circuit are damaged, thereby greatly reducing the probability of damaging the semiconductor components due to high voltage sparking, improving the reliability of the MARX generator, and being very suitable for use as the sparking protection circuit of the MARX pulse generator in the field of electric vacuum emission.

[0031] The above merely provides a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any changes or replacements easily thought of by those skilled in the art within the technical scope disclosed by the present application should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A protection circuit for a spark width adjustable MARX generator, characterized in that, The application relates to a protection circuit for a high-voltage pulse generator, which comprises the following parts: a sampling circuit, which comprises a current transformer and a sampling resistor R1, the current transformer is arranged between a high-voltage sparking signal generated by a MARX generator and a load, and the sampling resistor R1 is arranged in a secondary winding of the current transformer, and the sampling circuit is used for sampling the high-voltage sparking signal to generate a sampling voltage; a comparison circuit, which comprises a comparator and a first resistor R2 and a second resistor R3, the same direction end of the comparator is connected with the current transformer, and the reverse end is connected with a voltage dividing network composed of the first resistor and the second resistor, and the comparison circuit is used for comparing the sampling voltage of the high-voltage sparking signal with a set protection threshold voltage, and outputs a high-level pulse signal with a first width when high-voltage sparking occurs; a pulse width adjusting circuit, which comprises a monostable multivibrator, a third resistor and a capacitor, the monostable multivibrator is grounded through a resistance-capacitance network composed of the capacitor and the third resistor, and when the comparison circuit outputs the high-voltage pulse signal with the first width, the pulse width of the high-voltage pulse signal is adjusted to output a high-voltage pulse signal with a second width; a control circuit, which is connected with the pulse width adjusting circuit, and when the pulse width adjusting circuit outputs the high-voltage pulse signal with the second width, the control circuit cuts off the pulse control signal of the MARX generator and turns off the high-voltage pulse output, so as to protect semiconductor components of the MARX generator.

2. The spark width adjustable MARX generator protection circuit of claim 1, wherein, The high-voltage sparking signal is a current signal, and the high-voltage sparking signal sampled by the current transformer is converted into a voltage signal through the sampling resistor R1.

3. The spark width adjustable Marx generator protection circuit of claim 1, wherein, The protection threshold voltage is adjusted by adjusting the resistance values of the first resistor R2 and the second resistor R3.

4. The spark width adjustable MARX generator protection circuit of claim 1, wherein, The first width is tens of nanoseconds to hundreds of nanoseconds.

5. The spark width adjustable MARX generator protection circuit of claim 1, wherein, The second width is greater than the first width, and the second width Tw is proportional to R*C, wherein R is the resistance value of the third resistor Rt, and C is the capacitance value of the capacitor Ct.

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