JPS63226087A - Pulsed laser device - Google Patents

Abstract

PURPOSE:To facilitate high speed charging of a laser primary capacitor and reduce the repetition period of laser oscillation by a method wherein the output of an AC source circuit which stops driving when a voltage between both the terminals of the primary capacitor reaches a predetermined voltage is inputted to a Schenkel circuit and the continuity operation of a switching element for charge transfer is performed synchronizing with the stop of driving. CONSTITUTION:An AC source circuit (composed of, for instance, an inverter 2, a transformer 3 and so forth) which starts driving in accordance with a starting instruction and a voltage doubler rectifier circuit 1 are connected in series in a manner of plural stages as a charging circuit for a primary capacitor C8. A comparing circuit 5 generates an output when a predetermined voltage and the voltage of the smoothing capacitor C8 of the final stage of a Schenkel circuit 4 to which the output of the AC source circuit is inputted are compared and coincide with each other. The smoothing capacitor C8 also serves as the laser primary capacitor and stops driving of the AC source circuit in accordance with the output of the comparing circuit 5 and, synchronizing with the stop of driving, performes the continuity operation of a switching element S for charge transfer.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a pulse laser device that excites an excimer laser, a nitrogen laser, or the like by pulse discharge.

<Prior art> In a pulsed laser device, in order to generate a pulsed discharge between a pair of main discharge electrodes arranged in a laser medium gas,
For example, a capacitance transfer type circuit as shown in FIG. 3 is used. In this circuit, a switching element S such as a thyratron is held in a cut-off state, a primary capacitor C is charged via a resistor R and a reactor L, and when the primary capacitor reaches a predetermined charging voltage, switching is performed. Motoko S
conducts to transfer the charge of the primary capacitor C to the secondary capacitor (peaking capacitor) CP, and when the charging voltage of this secondary capacitor CP reaches a high voltage, a pulse discharge occurs between the main discharge electrode pair Ed. .

As a power source for charging the primary capacitor C, a DC stabilized power source P is conventionally used as shown in FIG.

<Problems to be Solved by the Invention> In the circuit shown in FIG. 3, the primary capacitor C is discharged to zero voltage every time the laser discharges, and from that state is charged by the DC stabilized power supply P. Therefore, a large current flows in the initial stage of charging the primary capacitor C, and the DC stabilized power supply P cannot withstand this current. To solve this problem, a resistor R is inserted for current limiting as shown in FIG. This limits the current within the usage range of the DC stabilized power supply P, but by suppressing the peak current, the average current that can be taken out also decreases, and as a result, the primary capacitor C cannot be adjusted to a specified value. There was a problem in that the time required to charge up to the voltage was long, and the repetition period of laser oscillation was restricted.

<Means for Solving the Problems> The present invention has been made to provide a pulse laser device that can charge the above-mentioned primary capacitor C at high speed, thereby shortening the repetition period of laser oscillation. The structure of the circuit will be explained with reference to FIG. 1 corresponding to the embodiment.The feature of the present invention is that the circuit starts driving in response to a start command as a charging circuit for a primary capacitor (day 0). A Schenkel circuit 4 is formed by connecting an AC power circuit (for example, an inverter 2, a transformer 3, etc.) and a voltage doubler rectifier circuit in series, and receives the output of the above AC power circuit as an input, and a Schenkel circuit 4 that uses the output of the above AC power circuit as an input. It has a comparator circuit 5 that compares the voltages of the smoothing capacitor C8 at the final stage of 4 and generates an output when they match.The capacitor CI+ is also used as the laser primary capacitor, and the output of the comparator circuit 5 is used to supply an AC power supply. The structure is such that the driving of the circuit is stopped and, in synchronization with this, the switching element S for charge transfer is made conductive.

<Operation> If the Schenkel circuit 4 is configured with, for example, a four-stage voltage doubler rectifier circuit, the voltage of the smoothing capacitor C8 in the final stage is as follows.
After the AC power supply circuit is started, the voltage asymptotically approaches to a voltage eight times its output voltage over time. If the comparator circuit 5 detects that the voltage of the capacitor C8 has reached the target voltage and stops the AC power supply circuit, an arbitrary voltage can be obtained across the capacitor C1l, which also serves as a primary capacitor.

By activating the switching element S in synchronization with this, the charge in the capacitor C3 is transferred to the secondary capacitor C2 as in the conventional device, and a pulse discharge is generated between the main discharge electrode pair Ed. Here, in the charging operation of the capacitor C, there is no need to suppress the peak current as in the conventional case, and charging can be performed at the highest possible speed, and the laser oscillation cycle can be shortened.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.

Rectifier circuit 1 uses commercial 3-phase AC 200V as an input signal, and
It outputs C280V and supplies it to the inverter 2. The inverter 2 converts the DC 280V into a 280V rectangular wave with a switching frequency of 25kHz, for example. This 280v
The rectangular wave is boosted by the next stage transformer 3 and converted into a 5kV rectangular wave. The above rectifier circuit 1. The inverter 2 and the transformer 3 form an AC power supply circuit, the 5 kV rectangular wave output of which is provided to the input of the Schenkel circuit 4.

The Schenkel circuit 4 is a circuit in which a voltage doubler rectifier circuit formed by two capacitors, e.g., C3 and C2+, and two diodes, e.g., D+ and D2, are connected in series in multiple stages. is obtained. In this embodiment, a four-stage voltage doubler rectifier circuit constitutes a Schenkel circuit, and therefore a maximum DC voltage of 40 kV can be obtained across the final stage capacitor C8. This final stage capacitor C6 also serves as the primary capacitor of the capacitance transfer type circuit for laser discharge.

That is, a reactor L is connected in series to the capacitor C6, a secondary capacitor (peaking capacitor) CP and a pair of main discharge electrodes Ed in the laser medium gas are connected in parallel to the reactor L, and further in parallel to the capacitor C6. A switching element S such as a cyrotron is inserted in the .

The voltage across the capacitor C8 is the voltage dividing resistor RI + R2
The measured value is introduced into the comparator circuit 5. Comparison circuit 5 is configured to compare the voltage measurement value with a preset set voltage, and to supply a stop command to inverter 2 when the voltage across capacitor C8 matches the set voltage. Further, in synchronization with this, a trigger circuit (not shown) of the switching element S is activated to perform a conduction operation.

Next, we will discuss the effect. FIG. 2 is a diagram showing the voltage across the capacitor C1l and the operation timing of the device.

When a start command is given to the inverter 2 when the electric charge of each capacitor in the Schenkel circuit 4 is zero, the capacitors Cz and C
The voltages of a, Ch, and Cs are 2.
The voltage asymptotically approaches 4.6.8 times the voltage over time, but the capacitor C1 is charged toward 40 kV as described above. When the voltage of this capacitor C8 reaches the desired set voltage, the inverter 2 is stopped by a signal from the comparator circuit 5, and in synchronization with this, for example, when the switching element S is made conductive at the same time, the set voltage is reached. The charge in the capacitor CI is transferred to the secondary capacitor C2, and a laser discharge is instantaneously generated in the main discharge electrode pair Ed. This causes the voltage of capacitor C8 to become zero. Next, after an appropriate period of time, the minimum value of which is determined by the repeatable cycles of other components of the laser device, a start command is issued to the inverter 2 again.
Repeat the above operations. In this way, the laser primary capacitor, that is, capacitor C, is used only when laser discharge is required.
1, and as soon as the charging voltage reaches the set voltage, laser discharge will occur.

In the above embodiment, the rectifier circuit 1. Inverter 2 and transformer 3
Although the rectangular wave output of an AC power supply circuit consisting of It goes without saying that the circuit 4 can be constructed by connecting any plurality of stages of voltage doubler rectifier circuits in series.

<Effects of the Invention> As explained above, according to the present invention, the smoothing capacitor at the final stage of the Schenkel circuit also serves as the primary capacitor of the pulse laser device, and when the driving is started in response to a startup command, the primary capacitor described above is The output of the AC power supply circuit, which stops driving when the voltage across both ends reaches the set voltage, is input to the Schenkel circuit, and switching is performed to transfer the charge of the laser primary capacitor to the secondary capacitor in synchronization with the driving stop. Since the element is configured to conduct a conductive operation, the laser primary capacitor can be charged at high speed without suppressing the peak current as in the conventional case, and the repetition period of laser oscillation can be shortened. . For example, in the embodiment shown in FIG.
The capacity is 2nl;'.

When C8 is 30 nF, the time required for the voltage across capacitor C3 to reach 20 kV is several msec, which allows the laser oscillation frequency to be reduced from the conventional 50 Hz.
It is possible to improve the frequency from about 100 Hz to about 100 Hz.

Furthermore, since the laser primary capacitor is charged only when laser discharge is necessary, the efficiency of the power supply is improved and, if a ceramic capacitor is used, its lifespan is extended.

[Brief explanation of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment of the present invention, FIG. 2 is an explanatory diagram of the voltage of the capacitor C6 and the operation timing of the device, and FIG. 3 is a diagram showing an example of the circuit configuration of a conventional pulse laser device. 1... Rectifier circuit 2... Inverter 3... Transformer 4... Schenkel circuit 5... Comparison circuit C1~Ca, Cp... Capacitor D, ~D8... Diode Ed... Main For discharge electrode...Reactor R,, R2...Voltage dividing resistor S...Switching element

Claims (1)

[Claims] The electric charge of the primary capacitor charged to a predetermined voltage is transferred to the secondary capacitor by the conduction operation of the switching element, and the charging voltage of the secondary capacitor charged by this transfer is transferred between the electrode pair in the laser medium gas. In a laser device that performs pulse discharge excitation by applying a voltage, an AC power supply circuit that starts driving in response to a start command and a voltage doubler rectifier circuit are connected in series in multiple stages, and the output of the AC power supply circuit is input. It has a Schenkel circuit and a comparison circuit that compares the set voltage with the voltage of the final stage smoothing capacitor of the Schenkel circuit and generates an output when they match, and the final stage smoothing capacitor is connected to the primary capacitor. A pulsed laser device, characterized in that the output of the comparison circuit is used to stop the drive of the AC power supply circuit, and in synchronization with this, the switching element is made conductive.