JP7106105B2 - pulse generator - Google Patents

Description

The present invention relates to a pulse generator capable of high-speed switching and capable of generating high-voltage, high-current pulses as an alternative to a thyratron.

Conventionally, thyratron switches (gas discharge tubes) are used to generate high current, high voltage pulses. A single thyratron switch can switch several tens of kV and several kA. A high switching speed is about 50 nanoseconds. In general, high-voltage and large-current switching speeds are slow, and high-speed switching up to about 50 nanoseconds has limits of performance of several tens of kV and about 2 kA.

As shown in FIG. 1, a circuit using a conventional thyratron switch is a gas-filled discharge tube 10 which is triggered between grids (1) and (2) with high voltage applied. As a result, a discharge is generated, and the anode and cathode become conductive. The thyratron switch requires a heater power supply, a reserver power supply, and a keep-alive power supply in order to discharge stably by the input signal of the trigger signal, and it is necessary to adjust each power supply according to the environmental conditions and the elapsed life of the thyratron. be.

As shown in FIG. 2, the thyratron switch 11a of the conventional pulse power supply circuit 11 is in an insulated state when there is no trigger signal. is charged via When a trigger signal is input to the thyratron switch 11a, it becomes conductive, and the charge accumulated in the capacitor 7 flows through the thyratron switch 11a. This current flows through resistor (2) and appears as a pulsed output across resistor (2) (pulse 8). An external power source connected to the thyratron switch 11a and a load circuit have various configurations, and can generate a positive or negative raw pulse or take out a square wave pulse.

The conventional thyratron switch 11a, as described above, is expensive and has a limited life in use, requiring periodic replacement. In addition, there is a problem in the stability with respect to the trigger signal, and the problem is that the operation changes depending on the temperature, usage environment, and the like. In addition, a pulse power supply using a thyratron switch requires a large installation space with a size of 3 meters square. Further, there is a demand for an improvement that requires a warm-up period of about two hours after turning on the power of the heater.

Efforts are therefore being made to realize the generation of high-current, high-voltage pulses with semiconductor switches. Recent semiconductor switch technology has advanced toward higher voltages and larger currents. However, since a single thyristor is insufficient in voltage and current, as shown in FIG. 3, to replace the thyratron, it is necessary to connect thyristors vertically and horizontally and simultaneously input trigger signals to each.

Therefore, each thyristor requires a large number of attached trigger circuits (gate drivers), which increases the volume. Additionally, the trigger circuit must operate at high voltages and must be specially constructed for isolation. At present, an interlock circuit for those failures must also be incorporated.

Conventional technologies for generating high-current and high-voltage pulses using semiconductor switches are not yet widely used because they result in larger volumes than thyratrons and are not inexpensive.

Here, the operating characteristics of the thyristor will be described with reference to FIG. A thyristor changes from off to on by applying a voltage (horizontal axis) and passing a gate current (vertical axis), and the current increases rapidly. Normally, the current between the anode and cathode is controlled by the gate current (I _G ). Even if the gate current (I _G ) is zero, an excess voltage that exceeds a certain voltage causes an electron avalanche in the semiconductor, turning the circuit on in the same way as when the gate current (I _G ) flows. Become. The voltage that switches at excess voltage is called the breakover voltage.

The switching speed of a thyristor that switches at a breakover voltage depends on the characteristics of each thyristor, but it is known that the switching speed in avalanche is faster than in normal operation. Since it is not used normally, it is not described or standardized as a characteristic of thyristors when it is marketed.

On the other hand, among commercially available semiconductor switching devices, thyristors or IGBTs are capable of switching large currents exceeding 1000A. However, the current situation is that the switching speed is only several hundred nanoseconds to microseconds, and does not fully satisfy the high-speed switching requirement.

Also, although FETs are capable of switching at a switching speed of 100 nanoseconds or less, a large number of FETs must be connected in parallel because the current per FET is as low as about 30 A. Furthermore, since the operating voltage per semiconductor is around 1 kV, it is necessary to connect 20 to several tens of switching devices in series in order to obtain a voltage of 20 kV to several tens of kV used in a thyratron. On the other hand, connecting FETs in series further slows the switching speed, so only microsecond pulse generation is currently implemented.

As described above, even with semiconductor switches that are becoming higher voltage and larger current, the current situation is that a pulse power supply with a switching speed of 100 nanoseconds or less at a large current exceeding 1000 A cannot be realized with a semiconductor switch.

NIM-A 796(2015)72-29 "Development of a high-power solid-state switch using static induction thyristors for a klystron modulator"

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a pulse generator capable of high-speed switching and capable of generating high-voltage, large-current pulses that can replace the thyratron.

(1)
An avalanche circuit in which a plurality of thyristors are connected in series and switches the thyristors with zero gate current, a trigger circuit that supplies a trigger signal to the lowest stage of the avalanche circuit, and a voltage that is evenly applied to the plurality of thyristors in the avalanche circuit. consists of an equal voltage supply circuit that supplies
By inputting the trigger signal to the lowest stage of the avalanche circuit,
By applying a DC high voltage from an external power supply to the switching circuit in which the thyristor is turned on and the avalanche circuit transitions from an insulated state to a low resistance state,
A pulse generator characterized by generating a high-voltage, high-current high-speed pulse to a load.
(2)
The pulse generator according to (1), wherein the high-speed pulse has a switching time of 100 nanoseconds or less.
(3)
The pulse generating device according to (1) or (2), wherein the high voltage is 20 kV or higher, and the high current is 400 A or higher.
and

Since the present invention switches using the avalanche mode of the thyristor, it can generate high voltage, high current pulses. As a result, the present invention can replace thyratron switches.

INDUSTRIAL APPLICABILITY The present invention is a pulse generator that operates a commercially available general-purpose thyristor in an avalanche mode, and is capable of stable multistage operation. A circuit for stably operating thyristors in avalanche mode in multiple stages can be used not only in series connection, but also in a Marx circuit configuration in which applied voltage is charged in parallel and discharged in series. Therefore, it is possible to lower the applied voltage compared to the thyratron.

In addition, the trigger circuit has a simple configuration and can perform switching operations faster than those of ordinary thyristors. Further, the circuit configuration is simple, so the volume is small, and the number of parts is small, so that the pulse generator is highly reliable.

Since high-speed switching is possible, the present invention can be applied to technical fields requiring high-voltage switches, such as high-voltage discharge, for example, electron gun power supplies and laser switching circuits.
Furthermore, the size of the high-voltage pulse power source used in the conventional thyratron switch was 3 meters square, but the size of the pulse power source using the pulse generator of the present invention can be increased to several tens of centimeters. I can. Therefore, it contributes to space saving of the installation place of the pulse power supply.
Further, since the pulse power source according to the present invention does not require a heater power source and a reservoir power source, it can be operated immediately after the power is turned on. In addition, long life and pulse stability, which are characteristics of semiconductors, can be expected.

A more specific application will be outlined below. Electron guns usually use high-voltage pulses of several microseconds, but by reducing this to pulses of 100 nanoseconds or less, discharge can be avoided, resulting in a compact and efficient electron gun. can be made.
In the conventional electron gun, the pulse voltage is further boosted using a pulse transformer to create a voltage of 100 kV or higher. Insulators with a range of Furthermore, it had to be insulated by gas to avoid edge discharge.
On the other hand, in the electron gun using the pulse power supply according to the present invention, a high voltage short pulse is realized, and not only the pulse power supply but also the electron gun itself does not discharge, so the insulator can be made as small as several centimeters. it becomes possible to

It is a circuit using a conventional thyratron switch. It is an example of a pulse power supply circuit using a thyratron switch. This is an example of a switch circuit that uses a semiconductor such as a thyristor and has the same function as a thyratron. 4 is a graph showing the relationship between voltage and current, which indicates operating characteristics of a thyristor; It is a switch circuit of the pulse generator of the present invention. FIG. 4 is an explanatory diagram of the operation of the pulse generator according to the present invention; It is an example of an output waveform of the pulse generator according to the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In addition, the present invention is not limited to the following embodiments.

As shown in FIGS. 5 and 6, the pulse generator 1 of the present invention includes a switching circuit 1a composed of an avalanche circuit 2, a trigger circuit 4, and an equal voltage supply circuit 6, which are configured by connecting a plurality of thyristors 2a in series; Similar to the pulse power supply circuit using the conventional thyratron switch shown in FIG. 2, which applies a high voltage to the switching circuit 1a, it includes a high voltage circuit, an output circuit for taking out a pulse output, and the like.

The avalanche circuit 2 is a circuit in which units having a gate input connected to a cathode are connected in series in order to make the gate current of the thyristor 2a zero.

The trigger circuit 4 creates a negative potential difference of around 1 kV in order to apply excess voltage to the lowest thyristor (thyristor (1)) of the avalanche circuit 2 .

In FIG. 5, the thyristor 2a is a normal gate switch to generate the trigger signal, but FETs or other switching devices can also be used.

The uniform voltage supply circuit 6 applies a constant voltage to each thyristor 2a of the avalanche circuit 2 using Zener diodes. The operation of the equal voltage supply circuit 6 is as follows.

A voltage close to the breakover voltage is applied to each thyristor 2a of the avalanche circuit 2, and when the trigger circuit 4 is activated, the cathode potential of the thyristor (1) drops to around 1 kV minus. Since a voltage close to the breakover voltage is already applied between the anode and the cathode of the thyristor (1), the potential of the cathode drops, exceeding the breakover voltage and turning on.
When the thyristor (1) is turned on, the potential of the cathode of the thyristor (2) is lowered and the thyristor (2) is also turned on, and all the thyristors (1) to (N) are turned on continuously. As a result, a conductive state (low resistance state) is established between A and B of the switching circuit 1a.

The present invention configured as described above generates a high-voltage, large-current pulse 7a in the same manner as a conventional thyratron switch, enabling high-speed switching.

FIG. 7 shows an example of output waveforms from 17 stages of thyristors (IXHX40N150V1HV, 1500V withstand voltage, manufactured by IXYS) used in the present invention. When 25 kV is applied to the capacitor and a 50Ω load resistor is used, the peak voltage is 22 kV, the peak current is 440 A, and the switching time (10-90%) is 20 ns.

The thyristor used in the present invention does not require parallel connection because the maximum peak current specification is 7.6 kA. Further, since each thyristor 2a of the avalanche circuit 2 does not require a gate signal, the switching circuit 1a has a very simple circuit configuration as compared with FIG.

1 pulse generator 1a switching circuit 2 avalanche circuit 2a thyristor 4 trigger circuit 6 equal voltage supply circuit 7 capacitor 7a pulse 10 discharge tube 11 pulse power supply circuit 11a thyratron switch

Claims (4)

an avalanche circuit in which a plurality of thyristors are connected in series to switch the thyristors at zero gate current ; a trigger circuit that adjusts the voltage of the avalanche circuit, and an equal voltage supply circuit that equally supplies the applied voltage to the plurality of thyristors of the avalanche circuit,
By exceeding the breakover voltage of the bottom thyristor of the avalanche circuit,
a switching circuit in which the thyristor is turned on and the avalanche circuit transitions from an insulated state to a low resistance state;
A pulse generator characterized by generating a high-voltage, high-current high-speed pulse to a load by applying a DC high voltage from an external power supply. 2. The pulse generator of claim 1, wherein said adjustment is to lower the potential of said cathode. 3. A pulse generator according to claim 1 or 2, wherein the applied voltage is close to the breakover voltage of the thyristor and does not exceed the breakover voltage. An avalanche circuit in which a plurality of thyristors are connected in series and switches the thyristors with zero gate current, a trigger circuit that supplies a trigger signal to the lowest stage of the avalanche circuit, and a voltage that is evenly applied to the plurality of thyristors in the avalanche circuit. consists of an equal voltage supply circuit that supplies
the applied voltage is a voltage close to the breakover voltage of the thyristor and does not exceed the breakover voltage;
By inputting the trigger signal to the lowest stage of the avalanche circuit,
a switching circuit in which the thyristor is turned on and the avalanche circuit transitions from an insulated state to a low resistance state;
A pulse generator characterized by generating a high-voltage, high-current high-speed pulse to a load by applying a DC high voltage from an external power supply.

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