JPH0653579A - Laser power supply - Google Patents

Abstract

(57) [Summary] [Purpose] To precisely control the lamp current waveform and obtain a desired peak value. [Structure] In the first laser power supply circuit 20, the switching transistor 26 is controlled by the switching control unit 36.
The switching operation is performed under the WM control to generate the first lamp current I1 controlled to have a desired waveform. In the second laser power supply circuit 50, the charging transistor 54 and the charging control unit 66 charge the capacitor 58 to a preset charging voltage, and the discharging transistor 60 and the discharging control unit 70 preset the capacitor 58. Then, the second lamp current I2 controlled to a desired peak value is generated by instantaneously discharging at an arbitrary timing. The main controller 80 controls or controls the respective operations of the first and second laser power supply circuits 20 and 50.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser power supply device for driving a laser excitation lamp for lighting.

[0002]

2. Description of the Related Art A laser excitation lamp is a lamp for oscillating a photoexcitation solid-state laser such as a YAG laser or a glass laser with optical energy, and a xenon lamp or a krypton lamp is often used.

In a conventional general laser power supply device for driving a lamp of this type, electric energy is once stored in a capacitor and then the stored energy is discharged instantaneously.
The discharge current is supplied to the lamp to light the lamp, and the emitted energy is applied to the laser medium to cause laser oscillation.

Recently, a large number of capacitors are connected in parallel in a bank type to an excitation lamp, and the capacitors are individually charged to arbitrary charging voltages and then discharged one after another to thereby discharge the large number of capacitors. It has also been practiced to obtain one desired lamp current waveform by connecting the bank discharge currents in sequence.

[0005]

The above-mentioned capacitor bank type laser power supply device can supply a lamp current having a high peak value to the excitation lamp, and thus can obtain a high laser output. Suitable for laser processing such as welding and drilling. However, the lamp current obtained by discharging the capacitor bank shows a fixed current waveform that rises sharply immediately after the start of discharge, reaches a peak value, and then drops sharply. Even if the method of controlling the waveform of the lamp current by connecting the discharge currents of the banks in a sequence is used, only the desired lamp current waveform is artificially generated. For example, the waveform may change smoothly or in small steps. The lamp current waveform cannot be obtained. For this reason, although it is possible to obtain a sufficiently high laser output for laser processing, it has been difficult to accurately meet today's diverse and complicated processing requirements.

The present invention has been made in view of such problems, and it is possible to precisely and arbitrarily control the waveform and the peak value of the lamp current, and it is possible to appropriately meet various laser processing requirements. An object of the present invention is to provide a laser power supply device capable of performing the above.

[0007]

In order to achieve the above object, a laser power supply device of the present invention is a laser power supply for supplying a lamp current to an excitation lamp for irradiating a laser medium with optical energy for laser oscillation. In the device, a first lamp current is supplied to the excitation lamp, the first lamp current having a desired waveform controlled by a switching operation of a switching element.
Laser power supply circuit, and a second laser power supply circuit that charges the capacitor to a desired charging voltage and then discharges the capacitor and supplies the discharge current as a second lamp current to the excitation lamp; The control means controls the first and second laser power supply circuits so that the second lamp currents are combined at a desired timing and supplied to the excitation lamp.

[0008]

In the first laser power supply circuit, the first lamp current controlled to have a desired waveform is obtained by switching the switching element by PWM control, for example. This first lamp current can be smoothly or stepwise controlled, but its peak value is limited. On the other hand, in the second laser power supply circuit, the second lamp current having a desired peak value according to the charging voltage is obtained by charging the capacitor to the desired charging voltage and then discharging the capacitor instantaneously. When the second lamp current and the first lamp current are combined and supplied to the excitation lamp, the excitation lamp has a controlled lamp current having a desired waveform and a desired peak value.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a circuit configuration of a laser power supply device according to an embodiment of the present invention. This laser power supply device supplies a lamp current to an excitation lamp 10 of a YAG laser for laser processing, for example. Y parallel to the excitation lamp 10
When the AG rod 12 is provided and the lamp 10 is turned on,
The light energy causes the YAG rod 12 to oscillate, and the laser light L emitted from both end surfaces of the YAG rod 12
B is repeatedly reflected between the pair of resonant mirrors 14 and 16 to be amplified and then output to the outside.

This laser power supply device is provided with two laser power supply circuits 20 and 50 of different current control systems as circuits for supplying a lamp current to the excitation lamp 10. A first lamp current I1 controlled to a desired waveform by the switching operation of the switching element is obtained from the first laser power supply circuit 20, and a desired peak value is obtained from the second laser power supply circuit 50 by the charge / discharge control means. A controlled second lamp current I2 is obtained.

The first laser power supply circuit 20 is constructed as follows. The input terminals of the three-phase full-wave rectifier circuit 22 are connected to the three-phase AC input terminals (U, V, W). The output terminal of the three-phase full-wave rectifier circuit 22 is the smoothing capacitor 2
4, the switching transistor 26 for waveform control, the coil 28 for smoothing, the capacitor 30, and the diode 32 are connected to the electrode terminal of the excitation lamp 10. The diode 34, which is connected in parallel with the capacitor 30 with the coil 28 interposed therebetween, constitutes a return circuit for returning the electromagnetic energy accumulated in the coil 28.

At the base of the switching transistor 26, the PWM control signal SA is supplied from the switching control unit 36.
Is provided as a switching control signal via the drive circuit 38. The PWM control signal SA turns on / off the switching transistor 26 at a high frequency, so that a pulse-width-modulated DC current having a chopper waveform is obtained at its collector terminal. The DC current of the chopper waveform is changed to the DC current of the envelope waveform corresponding to the pulse width by passing through the smoothing coil 28 and the capacitor 30, and this DC current is excited via the diode 32 as the first lamp current I1. It is supplied to the lamp 10.

In the switching control section 36 for performing the PWM control as described above, the main control section receives the starting signal ED for instructing the start / end of the first lamp current I1 and the current waveform reference signal Fi representing the desired current waveform. Given by 70. In addition, a current sensor 40 including, for example, a toroidal coil is provided in the current path of the first laser power supply circuit 20, and the current value measuring circuit 42 determines the current of the first lamp current I1 based on the output signal of the current sensor 40. Obtain the measured value. The switching control unit 36 receives the current measurement value MI1 from the current value measurement circuit 42, and performs PWM control by the feedback method so that the current measurement value MI1 follows the current waveform reference signal Fi from the main control unit 80.

As described above, in the first laser power supply circuit 20, the switching transistor 26 provided between the rectifier circuit 22 and the excitation lamp 10 is PWM-controlled to perform a switching operation so that a desired waveform is controlled. The obtained first lamp current I1 is obtained. However, the first laser power supply circuit 20 generates a desired current waveform by chopping the direct current at a substantially constant level from the rectification circuit 22 with the switching transistor 26 in small steps, so that the magnitude of the current value is large. Has a limit,
It does not mean that an arbitrary peak current value is obtained. But,
In this regard, a second laser power supply circuit 50 described later
Therefore, the present laser power supply device as a whole can obtain an arbitrary current peak value for practical use.

The second laser power supply circuit 50 is constructed as follows. The input terminals of the three-phase full-wave rectifier circuit 52 are connected to the three-phase AC input terminals (U, V, W). The output terminal of the three-phase full-wave rectifier circuit 22 is connected to a charging / discharging capacitor 58 via a charging switching transistor 54 and a charging coil 56.
The eight terminals are connected to the electrode terminals of the excitation lamp 10 through the discharging switching transistor 60 and the diode 62. The capacitor 58 can store a large amount of electric energy that can be used for laser processing.
For example, it has a capacitance of 10,000 to 20000 μF.

The voltage across the terminals of the capacitor 58, that is, the charging voltage VC is detected by the charging voltage detection circuit 64, and the detected charging voltage value MVC is given to the charging control unit 66.
The charging control unit 66 controls the charging voltage setting value F from the main control unit 80.
The control signal CS controls ON / OFF of the charging switching transistor 54 via the drive circuit 68 so that the charging of the capacitor 58 is stopped when the detected charging voltage MVC reaches the charging voltage set value Fv. To do. The discharge control unit 70 follows the timing signal TM1 from the main control unit 80 at a predetermined timing to cause the capacitor 5
8 to start the discharge switching transistor 60 via the drive circuit 72 by the control signal CS.
Control on and off.

As described above, in the second laser power supply circuit 50, the charging transistor 54 and the charging control unit 6 are provided.
6, the capacitor 58 is charged to a preset arbitrary charging voltage, and the discharging transistor 60 and the discharge control unit 70 instantly discharge the capacitor 58 at a preset arbitrary timing to obtain a desired peak value. A controlled second lamp current I2 is obtained.

The main controller 80 controls or supervises the operations of the first and second laser power supply circuits 20 and 50 as described above, and the current of the first lamp current I1 from the set value input unit 82. A trigger circuit 84 for taking in various setting values such as a waveform setting value, a peak value of the second lamp current I2 and a setting value of a combination pattern of those lamp currents I1 and I2, and applying a trigger TR to the lamp 10 It also controls. The laser power supply device is also provided with a simmer circuit (not shown) for stabilizing the discharge path in the excitation lamp 10.

FIG. 2 is a lamp current waveform diagram showing an example of the operation of the laser power supply device of this embodiment. In this example, in the first laser power supply circuit 20, the switching control unit 36 starts the operation at time t1 and the switching transistor 26 performs the switching operation by the PWM control, which corresponds to the preset reference waveform. For example, the first lamp current I having a trapezoidal waveform as shown in FIG.
1 is obtained and this first lamp current I1 is supplied to the excitation lamp 10 until time t3.

On the other hand, in the second laser power supply circuit 50, first, the charging control unit 66 operates to turn on the charging transistor 54 to charge the capacitor 58 to a preset charging voltage, and then the first lamp. At time t2 immediately after the current I1 finishes rising and reaches the flat level, the discharge control unit 70 is activated to turn on the discharge transistor 60, so that the capacitor 58 is instantly discharged, and the discharge voltage is changed according to the charging voltage. 2 has a peak value I P of, for example, FIG.
A discharge current is obtained as shown in (A), and this capacitor discharge current is instantaneously supplied to the excitation lamp 10 as the second lamp current I2.

As a result, the excitation lamp 10 shown in FIG.
As shown in (C), a lamp current that is a combination of the first lamp current I1 and the second lamp current I2 flows and YAG
A laser beam LB having a laser output corresponding to the combined lamp current (I1 + I2) is output from the rod 12.

In laser processing, an important parameter for melting the processed portion is the peak value of laser output,
Even if the time width is short, the required penetration can be obtained if there is a predetermined peak value. Therefore, by controlling the peak value of the second lamp current I2 to an optimum value, it is possible to obtain an appropriate laser output for melting an arbitrary workpiece. Further, in order to obtain the optimum processing quality according to the material, thickness, shape, etc. of the work piece, it is convenient to be able to control the overall pattern of the laser output waveform, in particular the rising and falling waveforms, arbitrarily and precisely, This point can be dealt with by selecting various waveforms of the first lamp current I1. As described above, in the present embodiment, the laser output waveform can be controlled arbitrarily and precisely, and can be controlled to an arbitrary peak value. Therefore, it is possible to appropriately meet a wide variety of laser processing requirements. You can

FIG. 3 shows some examples of lamp current waveforms according to this embodiment suitable for laser welding or cutting. Figure 3
The pattern shown in (A) of (1) is such that the starting end of the trapezoidal first lamp current I1 is made to rise steeply (almost vertically), and at the same time, the instantaneous pulsed second lamp current I2 is superimposed on it. The highest laser output is given to the welded part at the time of start-up, and thereafter the laser output corresponding to the waveform of the first lamp current I1 causes the nugget of the welded part to grow moderately, which is suitable for laser welding of aluminum materials. Is.

The pattern shown in FIG. 3B has a second lamp current I2 in the middle of the trapezoidal first lamp current I1.
The heated part of the welded part is heated (preheated) for a while by the laser output corresponding to the waveform of the first lamp current I1, and then the second instantaneous pulsed lamp current I2 is overlapped. The welded portion is melted by the laser output, and the nugget of the welded portion is moderately grown by the laser output corresponding to the first lamp current I1 from the end to the welding.
It is suitable when performing deep penetration welding.

The pattern of FIG. 3C is the first triangular wave pattern.
The second lamp current I2 is superposed on the apex of the lamp current I1 of No. 1, and is suitable for welding plated steel sheet. Of FIG.
The pattern (D) is a pattern in which the charge / discharge cycle of the capacitor 58 in the first laser power supply circuit 50 is increased and the second lamp current I2 is repeatedly superimposed on the first lamp current I1 at a constant level. Suitable for cutting. Besides, as shown in FIG. 3 (E), it is possible to alternately flow the second lamp current I2 and the first lamp current I1, or, as shown in FIG. 3 (F), It is also possible to have a pattern in which the second lamp current I2 is first made to flow for a plurality of pulses in succession and then the first lamp current I1 is made to flow. These patterns (A) to (F) are merely examples, and various other combinations of patterns are possible, and the waveform of the first lamp current I1 can be arbitrarily selected and changed.
It is also possible to adjust the pulse width of the lamp current I2 of.

FIG. 4 shows a circuit configuration of a laser power supply circuit according to a modification. In the figure, parts having the same configurations and functions as those in the above-mentioned embodiment are designated by the same reference numerals. In this modification, the first laser power supply circuit 20 'is composed of an inverter. The DC voltage output from the three-phase rectifier circuit 22 is four transistors 44A, 44B, 44C, 4
It is input to the inverter circuit composed of 4D. In response to the switching control signals Pa and Pb from the inverter control unit 48, the transistors 44A and 44D and the transistor 44 are
By alternately turning on and off B and 44C at a frequency sufficiently higher than the commercial frequency, a high-frequency AC rectangular pulse is obtained at the output terminal of this inverter circuit. The high frequency pulse from the inverter circuit is supplied to the primary coil of the welding transformer 46, and a low voltage / large current pulse is obtained in the secondary coil. This secondary pulse is converted into direct current by a rectifier circuit consisting of a pair of diodes 47A and 47B,
This DC secondary current is supplied to the excitation lamp 10 as the first lamp current I1. Transistors 44A-44
By controlling the switching operation of D by the PWM method, it is possible to obtain an arbitrary lamp current waveform I1 as in the above embodiment.

FIG. 5 shows a circuit configuration of a laser power supply circuit according to another modification. In this modification, two second laser power supply circuits 50A and 50B are provided in parallel, the peak values of the second lamp currents I2A and I2B are set arbitrarily, and the first values are set at arbitrary timings. Lamp current I1
Can be combined with. Similarly, a configuration in which three or more second laser power supply circuits 50A, 50B, ... Are provided in parallel is also possible. Note that in FIG. 5, various control units are omitted for convenience of illustration.

Although one embodiment of the present invention and some modified examples have been described above, the present invention is not limited to them and various modifications and changes can be made. For example, it is possible to use only one rectifier circuit 22, 52, and a single-phase rectifier circuit may be used. In addition, a protection circuit for protecting the switching element may be provided.

[0029]

As explained above, according to the laser power supply device of the present invention, the first laser power supply circuit generates the first lamp current controlled to a desired waveform, and the second laser power supply circuit is generated. 2nd controlled by the desired peak value by
Since the lamp current is generated and the first and second lamp currents are combined and supplied to the excitation lamp, the waveform of the laser output of the laser light emitted from the laser medium can be controlled arbitrarily and precisely. It is possible to control the peak value at any height and at any timing, and it is possible to appropriately meet today's diverse and complicated laser processing requirements.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a laser power supply device according to an embodiment of the present invention.

FIG. 2 is a lamp current waveform diagram showing an example of the operation of the laser power supply device of the embodiment.

FIG. 3 is a pattern diagram showing some examples of lamp current waveforms according to a preferred embodiment for laser welding or cutting.

FIG. 4 is a circuit diagram showing a circuit configuration of a laser power supply device according to a modification.

FIG. 5 is a circuit diagram showing a circuit configuration of a laser power supply device according to another modification.

[Explanation of symbols]

 10 Excitation Lamp 12 YAG Laser 20 First Laser Power Supply Circuit 26 Waveform Control Switching Transistor 36 Switching Control Section 50 Second Laser Power Supply Circuit 54 Charging Switching Transistor 58 Capacitor 60 Discharge Switching Transistor 66 Charging Control Section 70 Discharge control unit 80 Main control unit 82 Set value input unit

Claims (1)

[Claims] 1. A laser power supply device for supplying a lamp current to an excitation lamp for irradiating a laser medium with optical energy for laser oscillation, wherein a first lamp current controlled to a desired waveform by a switching operation of a switching element. A first laser power supply circuit for supplying the excitation lamp to the excitation lamp; and a second laser power circuit for supplying the excitation current to the excitation lamp as a second lamp current by discharging the capacitor after charging the capacitor to a desired charging voltage. A laser power supply circuit and control means for controlling the first and second laser power supply circuits so as to supply the excitation lamp with the first and second lamp currents combined at a desired timing. Characteristic laser power supply device.