JPH031714A - Pulse generating circuit - Google Patents

Abstract

PURPOSE:To obtain permanent service life and to improve the stability and reliability by constituting a switch with series connection of semiconductors and conducting the switch when an overvoltage is generated across each semiconductor and by interrupting the high voltage power supply. CONSTITUTION:Plural FETs 8 being components of a switch are connected in series and the voltage across each FET 8 is detected by a 1st detection circuit 9 and the entire voltage of the switch is detected by a 2nd detection circuit 10. When an overvoltage is applied to the entire switch and the FET 8 due to fluctuation of power voltage or circuit trouble and exceeds a reference voltage set by the detection circuits 9, 10, a high signal is inputted to a protection circuit 11 to conduct the FET 8 forcibly through an OR circuit 13, then destruction of the FET 8 due to breakdown over is prevented. Simultaneously, since a high voltage power supply 1 is interrupted, the secondary defect such as power supply short-circuit due to switch conduction is prevented. Thus, the service life is permanent, and a pulse generating switch high stability and reliability is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a high-voltage, high-current switch forming a pulse generation circuit used in a pulsed laser or the like.

[Conventional technology]

Figure 4 shows, for example, the magazine r C0PPERVAPORLA
SER5C〇85 OF AGE J (LASERFO
CUS, JULY, 1982) is a pulse generation circuit for a conventional copper vapor laser. Hereinafter, the present invention will be described using a pulse generation circuit for a copper vapor laser as an example.

In Figure 4 I, (1) is a high voltage power supply, (2) is a charging reactor, (3) is a charging diode, (4) is a main capacitor for charging and discharging, (5) is a charging resistor, (6) is a thyratron switch, and (7) is a laser tube.

Next, the operation will be explained. The high voltage (several KV to tens of KV) generated from the high voltage power supply (1) is transferred to the reactor (2
), the main capacitor (4) is charged through the diode (3) and the charging resistor (5).Next, when the thyratron switch (6) becomes conductive, the main capacitor (4)
The voltage stored in is applied to the laser tube (7) through the thyratron switch (6). At this time, the impedance of the laser tube (7) is significantly smaller than the resistance value of the charging resistor (5), so the current flowing through the thyratron switch (6th ζ) mainly flows through the laser tube (7). ) is excited and produces laser oscillation.

Generally, in the case of a copper vapor laser, if a steeper pulse voltage is applied to the laser tube (7), a higher laser output is achieved, so a thyratron switch (6) used as a switch requires switching of several tons. be done.

[Problems to be Solved by the Invention] As described above, in the conventional Nohalus generation circuit used in ζ-copper vapor lasers, etc., the pulse voltage supplied to the laser tube (7) is made steeper to increase laser efficiency. In order to achieve this, the switches used in the pulse generation circuit are
A thyratron switch (6) was used for high power and capable of switching on at several tens of nSeC. However, since the thyratron switch (6) is a vacuum tube, it has a finite lifespan and must be replaced frequently. Furthermore, since the thyratron switch (6) is handmade, there are problems with quality stability, such as individual variations in current rise and switching time, which affect laser efficiency.

This invention was made to solve the above-mentioned problems, and aims to provide a pulse generation switch that has no lifespan and is highly stable and reliable.

[Means to solve the problem]

The pulse generating circuit according to the present invention has a switch configured by connecting semiconductors in series, and detects the voltage of the semiconductor to turn on the switch in the event of an abnormality and to cut off the high voltage power supply. be.

[Effect]

In the pulse generating circuit according to the present invention, the switch is constructed by connecting semiconductors in series, and when an excessive voltage is applied to each semiconductor, the switch is made conductive and the high voltage power supply is cut off. It is possible to prevent the damage caused by Q, and to provide a highly stable pulse generation circuit with short life span.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

Section 1 (Here, (8) is FET 1 (9) is FET
The first detection circuit detects the voltage across both ends of the switch, the second detection circuit detects the voltage across the entire switch, the protection circuit σ, the signal generation circuit 4, and the first OR circuit a4.

FIG. 2 shows an embodiment of the second detection circuit αq in FIG. 1, in which (14a) and (14b) are voltage dividing resistors, rabbit is a comparator, and σQ is a flip-flop. FIG. 3 shows an embodiment of the protection circuit aυ in FIG. 1, and aη is a second OR circuit.

Next, the operation will be explained. In order to improve the stability of the switch and shorten its lifespan, it is necessary to convert the thyratron, which is a vacuum tube, into a semiconductor. Several KV to several 10 KV, several 10 n as achieved by Cycitron
A single semiconductor capable of 5ec switching cannot currently exist. Semiconductor FETs, etc. that achieve switching of several tens of nSeC have a maximum withstand voltage of only about I KV, so in order to obtain a withstand voltage of several KV to several tens of KV0'', it is necessary to connect multiple high-speed semiconductors such as FETs in series. However, if a switch is constructed by connecting high-speed semiconductors in series, if an overvoltage occurs in the switch or semiconductor due to abnormality due to fluctuations in power supply voltage or malfunction of the circuit, automatic self-destruction as seen in the Thyratron may occur. The protection will not work, and there is a risk that the semiconductor will be destroyed due to overvoltage breakdown.

Therefore, in this invention, as shown in FIG.
A plurality of FETs (8) are connected in series and have a withstand voltage of several KV to several tens of KV as a whole, but the voltage across each FET (g) is detected by the first detection circuit (9), And the voltage across the entire switch is detected by the second detection circuit αQ.

As shown in FIG. 2, the signal detected by the second detection circuit σQ is divided by voltage dividing resistors (14a) and (14b), and further compared with the reference voltage VREF. As a result, if VREF is small, the comparator q outputs a signal HIGH, the flip-flop σQ becomes HIGH, and the signal is input to the protection circuit (b). The output signal of the first detection circuit (9) having a similar configuration is also input to the protection circuit qυ. The signal input to the protection/protection circuit 4 is processed by a second OR circuit as shown in FIG.
) is entered. The signal generating circuit 0'3 generates a conductive signal during normal operation, and this signal is inputted to the first OR circuit side. Further, the reference voltage is applied to the first detection circuit (9
), ζ is set around the value obtained by dividing the withstand voltage of the FET (8), and the second detection circuit (for 1G, ζ is set around the value obtained by dividing the withstand voltage of the switch).

With the above configuration, even if an excessive voltage is applied to the entire switch and FET due to fluctuations in the power supply voltage or circuit trouble, the first detection circuit (9) and the second detection circuit will be able to set the voltage. When the reference voltage exceeds the reference voltage, a HIGH signal is automatically input to the protection circuit qυ, and the FET (a) can be forcibly made conductive through the first OR circuit. As a result, destruction of the FET (8) due to overvoltage resistance can be prevented. Furthermore, since the high-voltage power supply (1) is also cut off at the same time, secondary disasters such as short circuits of the power supply due to switch conduction can be prevented.

In the above embodiment, the voltage of the entire switch is detected by the second detection circuit QO, but the reliability is lowered, but the second detection circuit αQ is not provided, and the first detection circuit (9) is used. Overvoltage may be detected only by

In addition, although FET was used as the semiconductor in the above embodiment, SI
It may be a T, IGBT, SI thyristor, transistor, thyristor, etc.

As described above, according to the present invention, in a pulse generating circuit that charges a high voltage from a high voltage power source to a main capacitor and supplies the voltage of the main capacitor to a load through a switch, the switch is configured by connecting semiconductors in series, detects the voltage applied to both ends of each semiconductor, and when an overvoltage occurs, the switch is made conductive and the high voltage power supply is cut off, so it has a short lifespan and is stable. This has the effect of providing a highly reliable device.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a pulse generation circuit according to an embodiment of the invention, FIG. 2 is a circuit diagram showing a second detection circuit according to an embodiment of the invention, and FIG. 3 is an embodiment of the invention. FIG. 4 is a circuit diagram showing a protection circuit according to an example, and FIG. 4 is a circuit configuration diagram showing a conventional pulse generation circuit. (1) is the high voltage power supply, (4J is the main capacitor, (7) is the laser tube, (8) is the FET, (9) is the first detection circuit, is the protection circuit, and (b) is the signal generation circuit. In addition, in the figures, the same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] In a pulse generation circuit that charges a high-voltage voltage from a high-voltage power supply to a main capacitor and supplies the voltage of the main capacitor to a load through a switch, the switch is configured by connecting multiple semiconductors in series, and the voltage is generated at both ends of each semiconductor. a detection circuit for detecting the voltage at which the voltage is applied; and a protection circuit for outputting a conductive signal to each of the semiconductors and shutting off the high voltage power supply when the output from the detection circuit is equal to or higher than a reference value. generation circuit.