JP2020088031A - Power supply for laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a laser device having improved reliability.
A high frequency power supply applies a high frequency voltage V _RF to a resonance circuit including a capacitance of a pair of discharge electrodes. The overvoltage suppressing circuit 500 suppresses an overvoltage between both ends of the resonance circuit 210. The abnormality detector 600 stops the application of the high frequency voltage V _RF from the high frequency power supply 400 when detecting the abnormality.
[Selection diagram] Figure 2

Description

The present invention relates to a power supply device.

A laser processing apparatus is widely used as a processing tool for industry. A high output gas laser such as a CO ₂ laser is used for the laser processing apparatus. FIG. 1 is a block diagram of the laser device 100R. The laser device 100R includes a laser resonator 200 and a power supply device 250R. The laser resonator 200 includes a pair of discharge electrodes 202 and 204, a total reflection mirror 206, and a partial reflection mirror 208.

The pair of discharge electrodes 202 and 204 are provided in a gas chamber charged with a laser medium gas such as CO ₂ . A capacitance C exists between the pair of discharge electrodes 202 and 204. The capacitance C and the inductor L (inductor element or parasitic inductor) form a resonance circuit 210 having a resonance frequency f _RES .

The power supply device 250R applies the high frequency voltage V _RF to the resonance circuit 210. RF voltage _{V RF} frequency _{f RF} (hereinafter, referred to as the synchronization frequency) is set in the vicinity of the frequency _{f RES} of the resonant circuit. By applying the high frequency voltage V _RF , a discharge current flows between the pair of discharge electrodes 202 and 204. The discharge medium excites the laser medium gas to form a population inversion. The stimulated emission light reciprocates in the optical resonator formed by the total reflection mirror 206 and the partial reflection mirror 208, and is amplified by passing through the laser medium gas. A part of the amplified light is extracted as an output from the partial reflection mirror 208.

Power supply 250R includes a DC power supply 300 to generate a stabilized DC voltage _{V DC,} and a high frequency power supply 400 for converting the DC voltage _{V DC} to a high frequency voltage _{V RF.}

JP, 2018-39032, A JP, 2015-32746, A

As a result of examining the laser device 100R of FIG. 1, the present inventors have come to recognize the following problems.

When a contact failure or the like occurs in the discharge electrodes 202 and 204, the operation is performed in an open state. In the open state, the capacitance C is very small, and the resonance frequency of the resonance circuit has a very high value f _RES ′. In this state, if the high frequency voltage V _ac having the synchronous frequency f ₀ (f ₀ <f _RES ′) is continuously applied, a very high voltage exceeding the amplitude of the high frequency voltage V _RF is generated at the resonance frequency f _RES ′. When this high voltage is applied to the semiconductor element (that is, the power transistor) inside the high frequency power supply 400, the reliability decreases.

The present invention has been made in such a situation, and one of the exemplary objects of an aspect thereof is to provide a laser device having improved reliability.

An aspect of the present invention relates to a power supply device that drives a laser resonator including a pair of discharge electrodes. The power supply device includes a high-frequency power supply that applies a high-frequency voltage to a resonance circuit including a pair of discharge electrodes, an overvoltage suppression circuit that suppresses an overvoltage between both ends of the resonance circuit or an internal node of the high-frequency power supply, and an overvoltage suppression circuit. A series switch and an abnormality detector that turns on the switch when an abnormality is detected are provided.

The “abnormality” here is an abnormality that can cause an overvoltage in the power supply device. By providing the overvoltage suppressing circuit, the overvoltage can be suppressed and the semiconductor element included in the high frequency power supply can be protected when the resonance frequency of the resonance circuit largely deviates from the designed value. Further, in a situation where an overvoltage does not occur, by turning off the switch, it is possible to prevent a leak current from flowing through the overvoltage suppressing circuit, and it is possible to suppress noise due to the leak current.

The housing of the laser resonator may be grounded via a ground wire. The abnormality detector may detect the abnormality based on the current flowing through the ground wire.

The casing of the laser resonator is grounded via a ground wire, and the abnormality detector may detect the abnormality based on the potential of the casing.

The power supply device may further include notifying means for notifying the outside when the abnormality detector detects an abnormality.

The high frequency power supply may include an inverter and a transformer having a primary winding connected to the output of the inverter and a secondary winding connected to the laser resonator. The overvoltage suppressing circuit may be connected to the primary winding of the transformer.

The overvoltage suppression circuit may include at least one of a voltage suppressor, a surge protection device, and a gas arrester (surge arrester).

The overvoltage suppressing circuit may include a plurality of elements connected in series. When the capacitance of each element is large, connecting them in series can reduce the capacitance of the overvoltage suppressing circuit.

The overvoltage suppression circuit may include a capacitor that is 1/10 or less of the capacitance of the pair of discharge electrodes. In this case, since the capacitor serves as a load, it is possible to prevent the resonance frequency from becoming too high and suppress the overvoltage.

The overvoltage suppression circuit may include an LCR load. In this case, even if the discharge electrode becomes abnormal and opens, the resonance frequency can be prevented from becoming too high due to the LCR load, and the overvoltage can be suppressed.

It should be noted that any combination of the above constituent elements and constituent elements and expressions of the present invention that are mutually replaced among methods, devices, systems, etc. are also effective as an aspect of the present invention.

According to an aspect of the present invention, the reliability of the laser device can be increased.

It is a block diagram of a laser device. It is a block diagram of a laser device according to an embodiment. 3A and 3B are circuit diagrams showing a configuration example of the abnormality detector. 4A to 4D are circuit diagrams showing configuration examples of the overvoltage suppressing circuit. It is a circuit diagram which shows the specific structural example of a power supply device. It is a figure which shows the laser processing apparatus provided with a laser apparatus. FIGS. 7A and 7B are diagrams showing modified examples of the arrangement of the overvoltage suppressing circuit.

Hereinafter, the present invention will be described based on preferred embodiments with reference to the drawings. The same or equivalent constituent elements, members, and processes shown in each drawing are denoted by the same reference numerals, and duplicated description will be omitted as appropriate. Further, the embodiments are merely examples and do not limit the invention, and all the features and combinations thereof described in the embodiments are not necessarily essential to the invention.

FIG. 2 is a block diagram of the laser device 100 according to the embodiment. The laser device 100 includes a laser resonator 200 and a power supply device 250.

In FIG. 2, the laser resonator 200 is shown as an equivalent circuit. A capacitance C and a resistance component R are included between the pair of discharge electrodes 202 and 204. The capacitance C forms the resonance circuit 210 together with the inductor L. The resonance frequency of the resonance circuit 210 is f _RES . The inductor L includes at least one of an inductor component, wiring, and parasitic inductance of a substrate.

The power supply device 250 applies the high frequency voltage V _RF to the resonance circuit 210. RF voltage _{V RF} frequency _{f RF} (hereinafter, referred to as the synchronization frequency) is set in the vicinity of the frequency _{f RES} of the resonant circuit. By applying the high frequency voltage V _RF , a discharge current flows between the pair of discharge electrodes 202 and 204. The laser medium gas is excited by the discharge current, and the population inversion is formed.

The power supply device 250 includes a DC power supply 300, a high frequency power supply 400, an overvoltage suppressing circuit 500, a switch SW1, an abnormality detector 600, and a notification unit 610. DC power supply 300, whose output is connected to the pair of DC link 310 (also referred to as DC link voltage) stabilized DC voltage to a predetermined voltage level to the DC link 310 to generate V _DC.

The input of the high frequency power supply 400 is connected to the DC link 310 and receives the DC link voltage V _DC . The high frequency power supply 400 generates a high frequency voltage V _RF having the same frequency (synchronization frequency) f _RF as the resonance frequency f _RES, and supplies the high frequency voltage V _RF to the laser resonator 200. The configuration of the high-frequency power supply 400 is not limited, but includes an H bridge circuit (inverter) 402 that converts the DC voltage V _DC into the AC voltage V _AC , and a transformer 404 that boosts the output voltage V _AC of the H bridge circuit 402. You can

The overvoltage suppressing circuit 500 is configured to suppress an overvoltage between both ends of the resonance circuit 210 or an internal node of the high frequency power supply. In FIG. 2, the overvoltage suppressing circuit 500 is connected to the connection node of the H bridge circuit 402 and the step-up transformer 404, and can suppress the overvoltage of the primary side voltage of the step-up transformer 404.

The switch SW1 is provided in series with the overvoltage suppressing circuit 500 in order to cut off the current path of the overvoltage suppressing circuit 500.

When the abnormality detector 600 detects an abnormality in the laser device 100, the abnormality detector 600 asserts the abnormality detection signal S _ABN and turns on the switch SW1. The "abnormality" referred to here is an abnormality that may cause an overvoltage in the power supply device 250, in other words, an abnormality that shifts the resonance frequency higher than the design value, such as a contact failure between the discharge electrodes 202 and 204 and a disconnection of the inductor L. The disconnection of the wiring connecting them, the disconnection (open) of the wiring, or the deterioration due to the deterioration increases the impedance. Incidentally power device 250, abnormality may assert the abnormality detection signal S _ABN after occurrence may assert the abnormality detection signal S _ABN with indication of abnormality appeared stage.

The notification means 610 notifies the outside of the abnormality detection by the abnormality detector 600. For example, the notification means 610 may be a direct notification means to the user, such as a buzzer, a lamp, or a display.

Alternatively, the notification unit 610 may be an interface connected to a system-side controller that controls a buzzer, a lamp, and a display. In this case, the notification unit 610 may indirectly notify the user of the occurrence of the abnormality. In this case, the controller on the system side can execute an appropriate protective action at an appropriate timing by using the notification of the abnormality occurrence as a trigger.

The above is the basic configuration of the power supply device 250. Next, the operation will be described.

When an abnormality (or a sign thereof) occurs in the laser apparatus 100, the abnormality detector 600 asserts the abnormality detection signal S _ABN and turns on the switch SW1. As a result, the overvoltage suppressing circuit 500 is connected to the high frequency power supply 400, and the overvoltage between the nodes to which the overvoltage suppressing circuit 500 is connected is suppressed.

On the other hand, in the normal state of the laser device 100, the abnormality detector 600 has negated the abnormality detection signal S _ABN , and the switch SW1 is off. Therefore, the overvoltage suppressing circuit 500 is disconnected from the high frequency power supply 400.

The above is the operation of the power supply device 250. According to this power supply device 250, by providing the overvoltage suppressing circuit 500, the overvoltage can be suppressed when the resonance frequency f _RES of the resonance circuit 210 deviates greatly from the design value, and the semiconductor element included in the high frequency power supply 400 or the like can be provided. Can be protected. Further, in a situation where an overvoltage does not occur, by turning off the switch SW1, it is possible to prevent a leak current from flowing through the overvoltage suppressing circuit 500, and it is possible to suppress noise due to the leak current.

The present invention extends to various devices and methods understood as the block diagram and circuit diagram of FIG. 2 or derived from the above description, and is not limited to a specific configuration. Hereinafter, more specific configuration examples and examples will be described in order to help understanding of the essence and operation of the invention and to clarify them, not to narrow the scope of the invention.

-Abnormality detector 600 If the detection speed of the abnormality detector 600 is slow, turn-on of the switch SW1 is delayed, and an overvoltage is generated during the delay time, which is not preferable. Therefore, the abnormality detector 600 is required to assert the abnormality detection signal S _ABN earlier than the timing at which the overvoltage suppressing circuit 500 should work effectively (that is, the timing at which the overvoltage actually occurs). Therefore, the high-speed abnormality detector 600 will be described below.

3A and 3B are circuit diagrams showing a configuration example of the abnormality detector 600. The laser resonator 200 is covered with a metal housing (gas chamber) 220, and the housing 220 is grounded via a ground wire 222.

The abnormality detector 600 of FIG. 3A determines the presence or absence of abnormality based on the current Ix flowing through the ground wire 222. More specifically, when the amplitude of the current Ix flowing through the ground wire exceeds a predetermined threshold value, it can be determined that the abnormality.

The abnormality detector 600 of FIG. 3B determines whether or not there is an abnormality based on the ground potential Vx of the housing 220. More specifically, when the amplitude of the potential Vx exceeds a predetermined threshold value, it can be determined as abnormal.

The above is a configuration example of the abnormality detector 600. Next, the operation principle of the abnormality detector 600 will be described. A parasitic capacitance Cp exists between the discharge electrode 202 and the housing 220 and between the discharge electrode 204 and the housing 220. When the laser resonator 200 is normal, a current of the designed resonance frequency f _RES flows in the laser resonator 200 (between the electrodes 202 and 204), and the influence of the parasitic capacitance Cp can be ignored. At this time, the parasitic capacitance Cp and the current Ix flowing through the ground line 222 are substantially zero, and the potential Vx of the housing 220 is substantially equal to the ground voltage.

When the wiring connected to the discharge electrode 202 or the discharge electrode 204 is broken or the impedance increases, the resonance frequency of the resonance circuit 210 becomes higher than the designed value, and a high-frequency current flows. A high-frequency current flows through the ground line 222 via the parasitic capacitance Cp having a small capacitance value. As a result, the potential Vx of the housing 220 becomes non-zero.

According to the abnormality detector 600 of FIGS. 3A and 3B, the shift of the resonance frequency of the resonance circuit 210 can be detected at high speed, and before the overvoltage actually occurs inside the power supply device 250. The switch SW1 can be turned on (or immediately if it occurs).

The method of detecting an abnormality of the abnormality detector 600 is not limited to this. Instead of using a method with low responsiveness, the threshold value for abnormality determination may be set strictly.

4A to 4D are circuit diagrams showing configuration examples of the overvoltage suppressing circuit 500. The overvoltage suppressing circuit 500 in FIG. 4A includes a gas arrester 502. When the voltage between the terminals of the gas arrester 502 exceeds the operation start voltage, the gas arrester 502 is short-circuited and the voltage ΔV across the overvoltage suppressing circuit 500 is suppressed.

Here, the electrostatic capacitance between both ends of the overvoltage suppressing circuit 500 is preferably smaller than ⅕ of the electrostatic capacitance of the pair of discharge electrodes. This is because if the electrostatic capacitance of the overvoltage suppressing circuit 500 is too large, the resonance frequency f _RES of the resonance circuit 210 will be shifted, which will affect the circuit operation. From this point of view, when the overvoltage suppressing circuit 500 is configured by the gas arrester 502 alone as shown in FIG. 4A, the electrostatic capacitance may be too large.

In such a case, as shown in FIG. 4B, a plurality of overvoltage suppressing elements (surge protection elements) may be connected in series. As a result, the electrostatic capacitance between both ends of the overvoltage suppressing circuit 500 becomes a combined capacitance of the electrostatic capacities of the plurality of overvoltage suppressing elements, and thus can be made smaller than the electrostatic capacities of the individual overvoltage suppressing elements.

More specifically, the overvoltage suppressing circuit 500 of FIG. 4B includes a gas arrester 502 and a varistor 504 connected in series. In this configuration, when the high voltage ΔV is applied across the overvoltage suppressing circuit 500, the inter-terminal voltage of the gas arrester 502 exceeds the operation start voltage and becomes a short circuit state, and the high voltage ΔV is applied to the varistor 504. As a result, a current flows according to the IV characteristic of the varistor 504, and the high voltage ΔV can be suppressed. Instead of the varistor 504, a general overvoltage suppressing element can be used, and for example, SPD (zinc oxide type arrester) or transorp may be used.

The overvoltage suppressing circuit 500 in FIGS. 4A and 4B operates in response to the overvoltage, but the present invention is not limited to this. The overvoltage suppressing circuit 500 does not operate in the abnormal open state of the laser resonator 200. It may be a circuit for preventing the occurrence of. Overvoltage suppression circuit 500 and more specifically, in the synchronizing frequency f _RF, a sufficiently high impedance compared to the resonant circuit 210, at frequencies higher than the synchronous frequency f _RF, may have a low impedance. The overvoltage suppressing circuit 500 in FIG. 4C includes a capacitor 506. The capacitance of the capacitor 506 is 1/5 or less, preferably 1/10 or less of the capacitance of the pair of discharge electrodes 202 and 204. Even if the open abnormality occurs, the capacitor 506 remains as a load, so that it is possible to prevent the resonance frequency from becoming too high and suppress the overvoltage.

The overvoltage suppressing circuit 500 in FIG. 4D includes an LCR load circuit. Even in the open state, it is possible to prevent the resonance frequency from becoming too high due to the LCR load, and suppress overvoltage.

The overvoltage suppressing circuit 500 may have a configuration in which some of the circuits illustrated in FIGS. 4A to 4D are connected in parallel.

FIG. 5 is a circuit diagram showing a specific configuration example of the power supply device 250. A control signal (excitation signal) S1 for instructing a light emission period (excitation period) and a stop period is input to the laser device 100, and intermittent operation is performed based on the excitation signal S1. For example, the excitation signal S1 is a pulse signal having a repetition frequency of about several kHz and a duty ratio of about 5%.

The high frequency power supply 400 includes an H bridge circuit (full bridge circuit) 402 and a step-up transformer 404. The high frequency power supply 400 includes two sets of an H bridge circuit 402 and a set 401 of a step-up transformer 404, which are connected in parallel. Of course, this set 401 may be configured with only one system. While the excitation signal S1 is at a level (for example, high) indicating the excitation section, the H bridge circuit 402 switches and applies the _AC voltage V _AC to the primary winding of the step-up transformer 404. The switching frequency of the H-bridge circuit 402 is the synchronization frequency f _RF and is set to, for example, about 2 MHz. As a result, a high frequency voltage V _RF generated by boosting the _AC voltage V _AC is generated in the secondary winding of the step-up transformer 404.

DC power supply 300 includes a bank capacitor 302 and a charging circuit 304. The bank capacitor 302 is provided between the DC links 306. The charging circuit 304 charges the bank capacitor 302 and keeps the voltage _VDC of the bank capacitor 302 constant.

During the excitation period, the H bridge circuit 402 performs a switching operation, so that the energy (charge) stored in the bank capacitor 302 is released, and the voltage level of the DC voltage V _DC decreases. The charging circuit 304 supplies a charging current to the bank capacitor 302 so as to compensate for the decrease in the voltage level of the DC voltage V _DC . That is, the DC power supply 300 also operates intermittently in synchronization with the excitation signal S1.

The DC power supply 300 may be composed of a DC/DC converter that operates steadily even during the excitation period.

(Use)
Next, the application of the laser device 100 will be described. FIG. 6 is a diagram showing a laser processing apparatus 900 including the laser apparatus 100. The laser processing apparatus 900 irradiates the object 902 with a laser pulse 904 to process the object 902. The type of the object 902 is not particularly limited, and examples of the type of processing include, but are not limited to, drilling and cutting.

The laser processing device 900 includes a laser device 100, an optical system 910, a control device 920, and a stage 930. The object 902 is placed on the stage 930 and fixed as necessary. The stage 930 positions the target object 902 according to the position control signal S2 from the control device 920, and relatively scans the irradiation position of the target object 902 and the laser pulse 904. The stage 930 can be uniaxial, biaxial (XY) or triaxial (XYZ).

The laser device 100 oscillates in response to a trigger signal (excitation signal) S1 from the control device 920 and generates a laser pulse 906. The optical system 910 irradiates the object 902 with a laser pulse 906. The configuration of the optical system 910 is not particularly limited, and may include a mirror group for guiding the beam to the object 902, a lens for beam shaping, an aperture, and the like.

The control device 920 comprehensively controls the laser processing device 900. Specifically, the control device 920 intermittently outputs the excitation signal S1 to the laser device 100. The control device 920 also generates a position control signal S2 for controlling the stage 930 according to data (recipe) describing the processing.

The present invention has been described above based on the embodiment. This embodiment is merely an example, and it will be understood by those skilled in the art that various modifications can be made to the combinations of their respective constituent elements and processing processes, and that such modifications are also within the scope of the present invention. is there. Hereinafter, such modified examples will be described.

Some modifications of the arrangement of the overvoltage suppressing circuit will be described. Although the overvoltage suppressing circuit 500 is connected between the H bridge circuit 402 and the step-up transformer 404 in FIG. 2, this is not the only case. FIGS. 7A and 7B are diagrams showing modified examples of the arrangement of the overvoltage suppressing circuit 500.

As shown in FIG. 7A, the overvoltage suppressing circuit 500 and the switch SW1 may be provided on the output node of the high frequency power supply 400, that is, on the secondary side of the step-up transformer 404. As a result, the overvoltage of the secondary-side voltage V _RF is suppressed, and thus the overvoltage of the primary side can be suppressed.

As shown in FIG. 7B, a set of the overvoltage suppressing circuit 500 and the switch SW1 may be provided in parallel with each of the switches (transistors) MH and ML that form the H bridge circuit 402.

The overvoltage suppressing circuit 500 and the switch SW1 may be provided on the laser resonator 200 side.

Some variations of the abnormality detection method by the abnormality detector will be described.

The abnormality detector may determine the abnormality based on the presence or absence of output light from the laser device. If the laser device does not emit light (or the amount of light decreases), it may be determined to be abnormal.

The abnormality detector may determine the abnormality based on the current component of the resonance frequency. The current flowing through the load (resonance circuit) or the output of the high frequency power supply is monitored, the resonance frequency component is extracted from the detected value, and when the current at the resonance frequency is small, it may be determined as abnormal.

The abnormality detector may determine the abnormality based on a current component other than the resonance frequency. The current flowing through the load (resonance circuit) or the output of the high frequency power supply is monitored, components other than the resonance frequency are extracted from the detected value, and when the current other than the resonance frequency is large, it may be determined as abnormal.

The abnormality detector may determine the abnormality based on the width of decrease in the input voltage of the high frequency power supply after the shot. When the laser emits light normally, the electric charge stored in the output capacitor (bank capacitor) of the DC power source is discharged, and the DC voltage drops. Therefore, the voltage of the bank capacitor is monitored, and when the voltage drop is small, it can be determined as abnormal.

The anomaly detector may determine the anomaly based on noise having a frequency higher than the resonance frequency. When the current becomes high frequency, high frequency radiation noise or conduction noise increases. This noise is detected by the antenna, and when the noise increases, it can be determined to be abnormal.

The abnormality detector may determine the abnormality based on the voltage between the pair of discharge electrodes. If a sufficient voltage is not detected across the resonance circuit even though the high frequency voltage is applied, it can be determined to be abnormal.

Although the present invention has been described by using specific words and phrases based on the embodiments, the embodiments only show one aspect of the principle and application of the present invention. Many modifications and changes in arrangement are possible without departing from the spirit of the present invention defined in the range.

100 laser device 200 laser resonator 202, 204 discharge electrode 206 total reflection mirror 208 partial reflection mirror 210 resonance circuit 250 power supply device 300 DC power supply 302 bank capacitor 304 charging circuit 400 high-frequency power supply 402 H bridge circuit 404 step-up transformer 500 overvoltage suppression circuit 502 Gas arrester 504 Varistor 600 Abnormality detector 610 Notification means

Claims (5)

A power supply device for driving a laser resonator including a pair of discharge electrodes,
A high frequency power source for applying a high frequency voltage to a resonance circuit including the capacitance of the pair of discharge electrodes;
Between both ends of the resonance circuit, or an overvoltage suppressing circuit for suppressing an overvoltage of an internal node of the high frequency power supply,
A switch provided in series with the overvoltage suppressing circuit,
An abnormality detector that turns on the switch when an abnormality is detected,
A power supply device comprising: The casing of the laser resonator is grounded via a ground wire,
The power supply device according to claim 1, wherein the abnormality detector detects the abnormality based on a current flowing through the ground wire. The casing of the laser resonator is grounded via a ground wire,
The power supply device according to claim 1, wherein the abnormality detector detects the abnormality based on a potential of the housing. 4. The power supply device according to claim 1, further comprising a notification unit that notifies the outside when the abnormality detector detects an abnormality. The high frequency power source,
An inverter,
A transformer having a primary winding connected to the output of the inverter and a secondary winding connected to the laser resonator;
Including,
The power supply device according to any one of claims 1 to 4, wherein the overvoltage suppressing circuit is connected to the primary winding of the transformer.

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