JPH0412583A - Laser oscillator - Google Patents

Abstract

PURPOSE:To stabilize the laser output without depending on the change of power supply voltage, by detecting the voltage between terminals of a primary side smoothing capacitor, changing the switching of a switching low voltage power supply, and controlling the output power of a switching high voltage power supply. CONSTITUTION:A switching low voltage power supply 21 is installed, which is equipped with a rectifier 22 on the input side of a switching high voltage power supply 4, a smoothing capacitor 23, and a switching element 24. The voltage between terminals of a primary side smoothing capacitor 12 of the switching high voltage power supply 4 is detected, and the switching frequency or the switching-ON time of the switching low voltage power supply 2 is changed under a specified switching operation frequency, according to the above detected voltage, thereby controlling the output power of the switching high voltage power supply 4. Hence the voltage between the terminals of the primary side smoothing capacitor 12 is not changed when a power supply voltage is changed, so that the laser output can be stabilized.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a laser oscillator for generating laser light used in cutting, welding, heat treatment, and the like.

2. Description of the Related Art The structure of a conventional general laser oscillator will be explained with reference to FIG. one or more discharge tubes la and one
A laser resonator 1 consisting of a laser resonator 1 is provided with a set of discharge electrodes consisting of an anode 2 and a cathode 3 for each discharge tube la, lb. In FIG. 6, two sets of discharge tubes 1a, lb
are arranged symmetrically to form a discharge section, and a current is supplied from a switching high-voltage power supply 4 to each discharge electrode 2.3. Further, an output mirror 5 and a termination mirror 6 are arranged at both ends of the laser resonator 1, and a substantially E-shaped circulation tube body 7 is located near the cathode 3 at both ends and near the anode 2 at the center. are connected to form a circulation path for the gaseous laser medium. This circulation pipe body 7 is provided with a blower 8 for circulating the gas laser medium and a heat exchanger 9 for cooling the gas laser medium. The laser resonator 1 also includes an anode 2 and a cathode 3 of each discharge tube 1a, lb.
A discharge starting auxiliary ring 10 electrically connected to the anode 2 or the cathode 3 is disposed on the outer circumferential portion between the anode 2 and the cathode 3.

FIG. 7 shows the configuration of the switching high voltage power supply 4 in the laser oscillator. After receiving and rectifying the three-phase 200V by the primary rectifier 11, the primary smoothing capacitor 12 reduces voltage ripples, the switching element 13 switches to convert it into a pulse train, and sends power to the high frequency transformer 14. The high-frequency transformer 14 sends power to the secondary side and generates a high voltage on the secondary side, which is rectified by a high-speed high-voltage secondary rectifier 15 and then smoothed by a high-voltage secondary capacitor 16. A voltage is applied to the anode 2 and cathode 3 of the laser resonator 1, respectively.

Inside the laser resonator 1, a glow discharge occurs between the anode 2 and the cathode 3 to excite the internal gas laser medium and generate laser light.

On the other hand, the drive circuit 20 receives signals from an output setting circuit 18 that determines the switching-on time based on a command from the output command setting circuit 17, and a switching frequency setting circuit 19 that sets a reference switching frequency to set the switching-on time. determine the switching frequency and generate the drive signal. This drive signal is applied to the gate of the switching element 13 to generate a pulse signal.

In a laser oscillator configured in this way, the gas flow direction, the discharge direction, and the laser beam oscillation axis are coaxial, so the discharge and the gain distribution formed by the discharge are concentric when viewed from the optical axis direction. It has good symmetry and is said to have good processing performance such as cutting using the output laser light.

Problems to be Solved by the Invention However, in such conventional laser oscillators, when the voltage between the terminals of the primary side smoothing capacitor 12 changes due to fluctuations in the power supply voltage, the output power on the secondary side changes proportionally. There was also a problem that the laser output fluctuated.

The present invention solves these conventional problems, and aims to provide a laser oscillator that can stabilize laser output without depending on fluctuations in power supply voltage.

Means for Solving the Problems In order to achieve the above object, the present invention provides a switching low-voltage power supply having a rectifier, a smoothing capacitor, and a switching element on the input side of a switching high-voltage power supply, and the primary side smoothing capacitor of the switching high-voltage power supply is The output power of the switching high-voltage power supply is controlled by detecting the voltage between the terminals of 12 and changing the switching frequency or switching-on time of the switching low-voltage power supply to a predetermined switching operating frequency according to the detected voltage. This is what I did.

According to the present invention, with the above configuration, even if the power supply voltage fluctuates, the voltage between the terminals of the primary side smoothing capacitor does not fluctuate, and the laser output can be stabilized.

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

Since this embodiment utilizes the same switching high voltage power supply as the conventional example shown in FIG. 7, the same elements will be described with the same reference numerals.

In FIG. 1, 1 is a laser resonator, 2 and 3 are discharge electrodes, and 4 is a switching high voltage power supply. 11 is a primary rectifier, 12 is a primary smoothing capacitor, 13 is a switching element, 14 is a high frequency transformer, 15 is a secondary rectifier for high speed and high voltage, 16 is a secondary capacitor for high voltage, and 17 is an output command. A setting circuit, 18 is an output setting circuit, 19 is a switching frequency setting circuit, and 20 is a drive circuit.

21 is a switching low voltage power supply provided on the input side of the switching high voltage power supply 4. 22 is a rectifier circuit that receives AC input from a commercial power supply, 23 is a smoothing capacitor, and 24 is a switching element, the output of which is input to the primary rectifier 11 of the switching high-voltage power supply 4. 25 is a voltage detector for detecting the voltage between the terminals of the primary side smoothing capacitor 12, 26 is a reference voltage signal generator for generating a reference voltage, and 27 is a voltage detector 25 and a reference voltage signal generator 26.
28 is an output setting circuit (FM circuit) that sets the output of the switching low voltage power supply 21 based on the output of the differential amplifier 27.
, 29 is a switching-on time setting circuit that sets the switching-on time of the switching low-voltage power supply 21, and 30 is a drive circuit that drives the switching element 24 based on the outputs of the output setting circuit 28 and the switching-on time setting circuit 29.

Next, the operation of the above embodiment will be explained. When AC 200V from a commercial power supply is input to the rectifier 22 of the switching low-voltage power supply 21, it is first rectified by the rectifier 22, smoothed by the smoothing capacitor 23 to become DC, and converted to a pulse train by the switching element 24. The switching frequency and switching-on time at this time are controlled by the drive circuit 30. The pulse signal output from the switching element 24 is rectified again by the primary rectifier 11, smoothed by the primary smoothing capacitor, and converted again into a high-frequency pulse train by the switching element 13. The switching frequency and switching on time of the switching element 13 are controlled by the drive circuit 20. The output of the switching element 13 is boosted by the high frequency transformer 14, rectified again by the secondary rectifier 15, and then connected to the secondary smoothing capacitor 16.
It is smoothed and becomes a high voltage direct current, and the laser resonator 1
is applied to the discharge electrodes 2 and 3 of.

Inside the laser resonator 1, the glow discharge between the discharge electrodes 2.3 excites the internal gas laser medium and oscillates a laser beam.

On the other hand, within the switching low voltage power supply 21, the voltage detector 2
5 is the primary side smoothing capacitor 1 of the switching high voltage power supply 4
The voltage between the two terminals is detected, and its output is sent to the differential amplifier 27. In the differential amplifier 27, the voltage detector 25
The output voltage is compared with the reference voltage from the reference voltage signal generation circuit 26, and the difference is amplified and sent to the output setting circuit 28 of the switching low voltage power supply 21. Drive circuit 30
receives the switching frequency set value generated by the output setting circuit 28 and the switching on time set value fixed by the switching on time setting circuit 29, and controls the switching element 24 in the switching low voltage power supply 21. Note that the switching frequency set by the output setting circuit 28 is twice or more the switching frequency of the switching high-voltage power supply 4 in order to speed up control response.

Figure 2 shows when the voltage between the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 swings to the + side with respect to the reference voltage (A), when it is equal to the reference voltage (B), and when it swings to the - side. For each case (C), drive circuit 3
An example of a control signal generated from 0 is shown.

Now, when the voltage across the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 decreases, the switching low-voltage power supply 21 is adjusted according to the width of the voltage drop with respect to the reference voltage between the terminals so that the output power of the switching high-voltage power supply 4 is constant. Increase the switching frequency (in case of C). Furthermore, when the voltage between the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 increases, the switching frequency of the switching low-voltage power supply 21 is lowered (in the case of A) in accordance with the voltage increase relative to the reference voltage between the terminals. The output power of the power source 4 is controlled to be constant.

FIG. 3 compares the relationship between the variation rate of the power supply voltage and the variation rate of the output power in the case of using this embodiment and the case of the conventional example. As is clear from this figure, by detecting the voltage between the terminals of the primary side smoothing capacitor 12 of the switching high-voltage power supply 4 and controlling the switching frequency of the switching low-voltage power supply 21 according to the fluctuation width with respect to the reference terminal-terminal voltage. The output power from the switching high voltage power supply 4 can output stable laser light without depending on the power supply voltage.

FIG. 4 shows a second embodiment of the present invention.
The difference from the embodiment shown in FIG. 1 is the switching low voltage circuit 2 shown in FIG.
1 is the switching low voltage circuit 31, and the output setting circuit (FM circuit) 28 is the output setting circuit (PWM circuit) 3.
2, and the switching-on time setting circuit 29 has become the switching frequency setting circuit 33. Along with this, the drive circuit 34 has also been changed to operate in accordance with the human power signal.

Next, the operation of the main part of this second embodiment will be explained. Inside the switching low voltage power supply 31, a voltage detector 25 detects the voltage between the terminals of the primary side smoothing capacitor 12 of the switching high voltage power supply 40, and its output is sent to the differential amplifier 27.

In the differential amplifier 27, the output voltage of the voltage detector 25 is compared with the reference voltage from the reference voltage signal generation circuit 26, and the difference is amplified and sent to the output setting circuit (PWM circuit) 32 of the switching low voltage power supply 31. . The drive circuit 34 uses the switching-on time setting value generated by the output setting circuit (PWM circuit) 32 and the switching frequency setting circuit 33.
In response to the fixed switching frequency set value, the switching element 24 in the switching low voltage power supply 31 is controlled. Note that the switching frequency set by the switching frequency setting circuit 33 is a frequency that is twice or more the switching frequency of the switching high voltage power supply 4 in order to speed up control response.

Figure 5 shows cases in which the voltage between the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 swings to the + side with respect to the reference voltage (A), when it is equal to the reference voltage (B), and when it swings to the - side. For each of (C), the drive circuit 34
shows an example of a control signal generated by

Now, when the voltage across the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 decreases, the switching low-voltage power supply 31 is adjusted according to the voltage drop width with respect to the reference voltage between the terminals so that the output power of the switching high-voltage power supply 4 is constant. (in case of C). Furthermore, when the voltage between the terminals of the primary smoothing capacitor 12 of the switching high-voltage power supply 4 increases, the switching-on time of the switching low-voltage power supply 31 is narrowed (in case of Control the output power of the high voltage power supply to be constant. In this embodiment as well, output characteristics similar to those shown in FIG. 3 can be obtained.

In this way, by detecting the voltage between the terminals of the primary side smoothing capacitor 12 of the switching high-voltage power supply 4 and controlling the switching-on time of the switching low-voltage power supply 31 according to the fluctuation range with respect to the reference terminal-terminal voltage, the switching high-voltage power supply The output power from 4 can output stable laser light without depending on the power supply voltage.

Effects of the Invention As is clear from the above description, according to the present invention, the laser output does not fluctuate in proportion to the power supply voltage, and the reliability of laser processing can be greatly improved.

[Brief explanation of drawings]

Fig. 1 is a block diagram of a high voltage power supply for a laser oscillator showing one embodiment of the present invention, Fig. 2 is a signal waveform diagram showing control operations in the same embodiment, and Fig. 3 shows the effects of the same embodiment in a conventional example. FIG. 4 is a block diagram of the high voltage power supply according to the second embodiment of the present invention, and FIG.
FIG. 6 is a block diagram showing a general example of a conventional laser device, and FIG. 7 is a block diagram of a switching high-voltage power supply in the conventional example. 1...Laser resonator, la, lb...discharge tube, 2゜3...discharge electrode, 4...switching high voltage power supply, 5
...Output mirror 6...Terminal mirror, 7...Circulation pipe body, 8...Blower, 9...Heat exchanger, 10...
Discharge start auxiliary ring, 11...Primary side rectifier, 12.
...Primary side smoothing capacitor, 13...Switching element, 14...High frequency transformer, -15...Secondary side rectifier, 16...Secondary side capacitor, 17...Output command setting circuit, 18... Output setting circuit (PWM circuit),
19... Switching frequency setting circuit, 20... Drive circuit, 21... Switching low voltage power supply, 22...
- Rectifier, 23... Smoothing capacitor, 24... Switching element, 25... Voltage detector, 26... Reference voltage signal generator, 27... Differential amplifier, 28... Output setting circuit (FM circuit), 29... Switching on time setting circuit, 30... Drive circuit, 31... Switching low voltage power supply, 32... Output setting circuit (PWM
circuit), 33... switching frequency setting circuit, 34
...Drive circuit.

Claims (4)

[Claims] (1) A primary rectifier installed on the primary side of the high-frequency transformer to rectify the AC input, a primary smoothing capacitor to smooth the rectified DC, and convert the smoothed DC into a pulse train. a switching high voltage power supply having a switching element for rectifying the AC input provided on the input side of the primary rectifier, a smoothing capacitor for smoothing the rectified DC input, and a smoothing capacitor for smoothing the rectified DC input; a switching low-voltage power supply having a switching element for converting a direct current into a pulse train; A laser oscillator characterized by controlling the output power of a switching high voltage power supply. (2) The laser oscillator according to claim (1), wherein the switching low-voltage power supply changes the switching frequency using a switching operating frequency that is twice or more the switching frequency of the switching high-voltage power supply. (3) The laser oscillator according to claim (1), wherein the switching low voltage power supply controls the output power of the switching high voltage power supply by changing the switching on time instead of the switching frequency of the switching element. (4) The laser oscillator according to claim (3), wherein the switching low-voltage power supply changes the switching-on time using a switching operating frequency that is twice or more the switching frequency of the switching high-voltage power supply.