JP2000349375A - Laser power unit and laser - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance reliability by optimizing the control cycle of the switching of the switching element of a laser power unit. SOLUTION: The waveform of the current to be supplied to a laser stimulation lamp 7 or a semiconductor laser for stimulating a laser medium is set to correspond to each switching control of a switching element 2. Then, each switching control is decided by comparing the magnitude of the current preset in a microcomputer control unit 8 and that of the monitored instant current flowing to a laser stimulation lamp 7 by a current detector 6 by means of the microcomputer control unit 8, and the current waveform is set according to the result.

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 comprising a chopper circuit for instantaneous value control by an electric monitor and capable of freely controlling an output waveform, and a laser device using the same.

[0002]

2. Description of the Related Art In recent years, as a power supply for a solid-state laser, a type capable of freely controlling an output waveform centering on a pulse laser has become mainstream. In the case of a lamp-pumped pulse laser, the output current needs to be about 500 A at the maximum and a response of about 0.5 ms is required. In order to realize this response with a conventional DC-DC converter using an LC filter, high-frequency switching of 100 kHz or more is required, but at present, high-power switching elements that satisfy this requirement are not generally found.

For this reason, in the techniques disclosed in Japanese Patent Publication No. Hei 7-59146 and Japanese Patent Laid-Open Publication No. Hei 10-242550, a chopper circuit for instantaneous current monitor value control is used. These techniques differ from DC-DC converters in that no capacitors are present in the final filter of the circuit.

That is, in the technique disclosed in Japanese Patent Publication No. Hei 7-59146, the following control is performed using a chopper circuit for instantaneous current value control. (1)
The magnitude of the output current monitor is compared with that of the output command to obtain a control pulse signal which becomes 1 when output monitor ≦ output command and becomes 0 when output monitor> output command. (2) Obtain a synchronized pulse signal in which the control pulse signal is synchronized with the edge of a certain clock pulse. (3) Switching is controlled when the synchronization pulse 1 corresponds to the switch ON and the synchronization signal 0 corresponds to the switch OFF. By such control through these three steps, an output current having a certain amplitude (defined as ripple) is obtained based on the output command value.

The technique described in Japanese Patent Application Laid-Open No. 10-242550 is a modification of the method of the current command value in the technique described in Japanese Patent Publication No. 7-59146. In other words, the upper limit and the lower limit of the current are set by the current threshold value setting device, and the generation method of the switching signal is partially changed. In this method, the upper limit and the lower limit are set to control the ripple width of the output current and also to control the number of times the switch is turned on / off.

For example, when the temperature of the switching element rises excessively, the set value is corrected so that the upper and lower limits (ripple width) of the current increase. As a result, the number of times of switch ON / OFF switching is reduced (however, output ripple is increased), and a brake is applied to the temperature rise of the element. In addition, a method has been proposed in which the power before and after the switching element is measured, and the upper and lower limit setting widths are corrected according to the difference. As described above, a function of detecting overload of the switching element and reducing heat generation of the element by reducing the number of times of switching ON / OFF is provided.

This function is described in Japanese Patent Publication No. Hei 7-59146.
The operation reliability of the switching unit, which has been a problem in the technology described in Japanese Patent Application Laid-Open No. H10-205, has been improved to some extent.

[0008]

However, in the system of the technique described in Japanese Patent Publication No. Hei 7-59146, the switching cycle cannot be determined unlike the PWM control used in the conventional DC-DC converter. The switching control is performed by synchronizing the result of the magnitude comparison between the output current monitor and the output command value with the clock pulse, and its cycle always changes.

In this case, a substantial switch ON / OFF is performed.
The number of times of switching is determined by the condition of (number of times of ON / OFF switching) ≤ (frequency of clock pulse), but the exact number of times depends on the impedance characteristics of the load, the L value of the filter unit, the value of the input DC voltage source, etc. It is not determined because it depends greatly.

[0010] As a result, it is extremely difficult to estimate the loss of the switching section, and it is a major issue to secure the reliability of the switching circuit.

Therefore, the product design in this case includes loss,
It is necessary to select an expensive switching element having an excellent capability with respect to a switching frequency, and to allow for a sufficient margin for cooling. As a result, an increase in the cost of the laser power supply cannot be avoided.

The technique described in Japanese Patent Application Laid-Open No. 10-242550 is the same as the technique described in Japanese Patent Publication No. 7-59146 in that switching is self-excited control. For this reason, the load on the switching element is monitored during the laser operation, the upper and lower limits of the output current are constantly corrected, and the number of times of switch ON / OFF switching is adjusted. This may cause a new problem that the ripple width of the waveform changes randomly.

Further, the number of times the switch is turned on / off varies depending on the impedance characteristic of the load, the L value of the filter unit, the value of the input DC voltage source, etc., and it is necessary to adjust the upper and lower limits of the current each time. Becomes For this reason, even in the case of the technology described in Japanese Patent Application Laid-Open No. H10-242550, an expensive switching element having excellent capability is selected,
It is inevitable that a sufficient margin is expected for the cooling.

A laser power supply using a chopper circuit for instantaneous value control of a current monitor capable of freely controlling an output waveform with any of these high-speed responses (for example, Japanese Patent Publication No. Hei 7-59146).
And Japanese Patent Application Laid-Open No. 10-242550), since the number of times of switching ON / OFF is accompanied by uncertainty, it is extremely difficult to estimate the switching loss. Was causing the problem of rising prices.

The present invention has been made based on these circumstances, and it is determined whether or not the switching loss is within a safe operating range by checking the switching control of the switching element, and based on the determination result, the switching of the switching element is performed. It is an object of the present invention to provide a laser power supply device in which the control cycle is optimized, the reliability of the switching control is improved, and the cost is reduced by appropriately designing the switching circuit, and a laser device using the same.

[0016]

According to the first aspect of the present invention, an electric waveform to be supplied to a laser excitation source is set in correspondence with each switching control of a switching element, and this switching control is performed every time. In a laser power supply device that determines and compares a preset set electrical value with an instantaneous value of an electrical monitor flowing to the laser excitation source and performs control based on the result, the preset set electrical value includes a plurality of set electrical values. A laser power supply device characterized in that the value is a value.

According to the second aspect of the present invention,
The switching control of the switching element is ON / O
A laser power supply device which counts the number of times of FF switching and changes the cycle of the switching control according to the counted number.

According to the third aspect of the present invention,
The switching control of the switching element is ON / O
A laser power supply device characterized by adding an electrical monitor instantaneous value at the time of FF switching, and changing a control cycle of the switch according to the added value.

According to the means of the invention of claim 4,
ON by switching control of the switching element
In the case of the above, electricity is supplied from the DC power supply to the laser excitation source via the inductance, and in the case of OFF, the electricity is fed back via the diode by the back electromotive force of the inductance, and based on the result, the laser A laser power supply device for setting an electric waveform to be supplied to an excitation source.

According to the fifth aspect of the present invention,
The comparison between the set electrical value and the instantaneous value of the electrical monitor flowing to the laser excitation source is performed by sequentially moving up from the shorter one of the switching control cycles of the set electrical value to the longer one. It is a laser power supply device characterized by the following.

According to the means of the invention of claim 6,
A laser device which operates using the above laser power supply device.

[0022]

Embodiments of the present invention will be described below with reference to the drawings. In the following, control is performed by monitoring a current value as an example, but a voltage value or a power value may be monitored. In short, it suffices if the electric value (a generic term for the above three values) can be monitored.

FIG. 1 is a configuration diagram of a laser power supply device showing an example of an embodiment of the present invention. That is, 1 is a DC power supply that rectifies and smoothes a commercial power supply by using a rectifying element and a capacitor (not shown), and 2 is a high-speed switching transistor that switches ON / OFF the current from the DC power supply 1, an FET, and an IGBT. 3 is a driver for driving the switching element, 3 is a driver for driving the switching element, 4 is an inductor, 5 is a current feedback diode, 6 is a current detector, 7 is a laser excitation lamp serving as a load of a DC power supply, and 8 is a laser power supply. A microcomputer control unit 9 for performing control is a user waveform setting device that is arbitrarily set by a user having a time resolution of 0.1 ms according to a processing target.

FIGS. 2A and 2B are schematic graphs of current waveform data in which the control cycle is changed, all of which are preset in the microcomputer. That is, when the current is 250 A and the time is 1.0 ms in the microcomputer control unit 8, the control cycle of the switch is previously set to 10 μs, 20 μs,
Five types of current waveform data corresponding to each of 25 μs, 50 μs, and 100 μs are stored.

FIG. 3 shows an output current waveform set by the user with the user waveform setting device. The output current waveform set by the user with the user waveform setting unit 9 is arbitrarily set by the user in accordance with the processing target, and the microcomputer control unit 8
Thus, the current waveform data set in the microcomputer control unit 8 is converted into the optimal current waveform data in accordance with the switching control every time.

Next, control of the microcomputer control unit 8 will be described. 4A and 4B are explanatory diagrams of control of the microcomputer control unit 8, FIG. 4A is an explanatory diagram of current setting data corresponding to switching control, FIG. 4B is an explanatory diagram of a switching control timing signal, (C) is switch ON
FIG. 4 is an explanatory diagram of / OFF switching control, and FIG. 7D is an explanatory diagram of an output current waveform.

As an example, the switching control cycle is 1
The case of 00 μs will be described. Upon receiving the output start command, the microcomputer control unit 8 forcibly turns ON the first switching control. During this ON operation,
Output current △ l is theoretically _{△ l = [(V in -V} out) / L] × dt ( Equation _{1) V in:} input DC voltage V _out: output voltage L: Inductor dt: increased by switching the control cycle .

In the actual control, at the timing when the first switching control is completed, the current monitor instantaneous value obtained via the current detector 6 shown in FIG. Captures as a current monitor value. This current monitor instantaneous value is immediately compared with the first current set value of the waveform data set corresponding to the switching control, and is reflected in the second switching control.

When the result of the magnitude comparison by the control of the microcomputer control unit 8 is (current monitor instantaneous value) <(current set value), the switching control is turned on, and conversely, (current monitor instantaneous value) ≧ (current set value) )), It turns off.

Subsequently, when the timing for ending the second switching control comes, the microcomputer control unit 8 fetches the current monitoring instantaneous value of the current detector 6 as in the case of the first switching control, and outputs the second current set value and the second current set value. Compare large and small. The result is reflected in the third switching control. The fourth and subsequent switching controls are performed in a similar process.

While the switch is off, the output current Δl changes theoretically as follows.

Δl = − [V _out / L] × dt (Equation 2) V _out : output voltage L: inductor dt: switching control cycle period When the switch is OFF, the current of the inductor 4 is generated by the back electromotive force of the inductor 4. The current waveform is fed back via the feedback diode 5 to converge the current waveform to the current waveform stored in the microcomputer control unit 8.

In this embodiment, the output condition set by the user is a rectangular wave having a pulse width of 1 ms, 250 A and a repetition of 50 Hz as shown in FIGS. 3 and 4A. Is that the safe operating range at 250A operation is (switching frequency) ≤ 5KH
z.

Next, the process of adjusting the control cycle of the switch of the switching element 2 will be described.

As described above, the microcomputer control unit 8
When the user sets an output waveform in the user waveform setting device 9, the output waveform is controlled by the switching control of the switching element 2 (the control cycle is, for example, 10 μm, 20 μm, 25 μm, 50 μm).
4 are stored as the current setting data shown in FIG. At the same time, the number of times of switching ON / OFF of the switching element 2 permitted per one pulse in the 250A operation is calculated. In the case of the above-described embodiment, the upper limit of the switching frequency of the switching element 2 at 250 A operation is 5 kHz.
At this time, since a rectangular wave pulse of 50 Hz is repeatedly output, the switching element 2 is assigned a switching frequency of 5 kHz / 50 Hz = 100 times per pulse. As a result, ON / O permitted per pulse
The number of FF switching is 200 times. This is defined as the number of ON / OFF operations at the loss limit, and the value is stored in the microcomputer control unit 8.

The optimum switching control period of the switching element 2 is determined by the ON / OFF count of the microcomputer control unit 8 when the DC power supply 1 is actually temporarily operated by one pulse output.
The number of times of switching OFF and the number of times of ON / OFF switching at the loss limit are compared and determined (this is called a switching control check).

In order to reduce the current ripple of the output current waveform, the shorter the control cycle is, the better it is.
If the number of times of / OFF switching exceeds the loss limit number, the switching loss threatens the safety region. Therefore, this switching control check is to check the optimal switching control cycle in which both are satisfied, and is performed in the following procedure.

(1) Switching control cycle is 10 μs
Tentatively operates the DC power supply 1 for one pulse,
The number of times of switching OFF is counted.

(2) The result is expressed as the loss limit O
This is compared with the number of N / OFF switching. If the number of times of ON / OFF switching is less than the number of times of ON / OFF switching at the loss limit, 10 μs becomes the proper clock as it is. Conversely, if this loss exceeds the ON / OFF switching limit number of times, it means that the switching loss threatens the safety region. Therefore, it is necessary to increase the switching control cycle to reduce the number of ON / OFF switching. In such a case, (3) the switching control cycle is increased until the number of times of ON / OFF switching becomes lower than the limit number of losses. In this embodiment, 20 μs → 25 μs → 50 μs →
ON / OFF by increasing the control cycle to 100 μs
The switching is continued until the number of switching falls below the loss limit. The switching control cycle at the time when the number of times of ON / OFF switching falls below the loss limit number is selected as the optimum value.

Through the above process, the switching loss of the switching element 2 enters the safe operation area, and the optimum switching control cycle with the smallest output current ripple can be determined.

FIGS. 5A to 5E are graphs of output current waveforms in each switching control cycle of the switching element 2 used in the above embodiment. That is, as the control cycle becomes longer, the loss becomes smaller, but the current ripple becomes larger. Therefore, the performance of the waveform control is not degraded when the control cycle is increased.

This switching control check is performed every time the output setting (pulse waveform, repetition) of the user changes, and the optimum switching control cycle included in the output condition is always selected. When a laser irradiation start command is received from the user, the output control of the laser power supply is started at the optimal switching control cycle.

As described above, according to the laser power supply of the present invention, the current waveform supplied to the lamp or the semiconductor laser for exciting the laser medium is set in correspondence with each switching control, and each switching control is performed by the microcomputer. The microcomputer control unit compares the current set value preset in the control unit with the instantaneous value of the current monitor flowing to the laser excitation lamp 7 by the current detector, and determines the magnitude comparison result by the microcomputer control unit. When (current monitor instantaneous value) <(current set value), the switching control at that time is turned ON. On the other hand, when (current monitor instantaneous value) ≧ (current set value), the switching control at that time is turned off, and the number of times of switching ON / OFF is reduced, so that the overload on the switching element can be reduced. It is possible to always operate a load such as a laser excitation lamp with an optimum waveform.

In the above embodiment, the switch O
Although the optimal switching control cycle was determined by counting the number of N / OFF switching, the switch ON / OFF
Instead of counting the number of times of switching, the result of adding the instantaneous value of current monitoring at the time of ON / OFF switching,
A method of determining an optimal switching control cycle is also effective.

Next, an embodiment in which the above-described laser power supply device is used for a laser device will be described.

FIG. 6 is a block diagram of a laser processing device showing a use state of a laser power supply device used in a solid-state laser device according to an embodiment of the present invention. In the figure,
The same reference numerals and symbols as those of the laser power supply according to the embodiment of the present invention indicate the same or corresponding components as those of the above-described embodiment of the laser power supply device. Omitted.

That is, the laser oscillator 15 which oscillates using the lamp light source 4 as an excitation source is composed of a solid-state laser medium such as YAG or a resonator not shown in the solid-state laser device. From the laser oscillator 15, a laser beam transmission means 16 including an optical fiber or a mirror is connected to the processing machine 17. The processing machine 17 includes a processing head (not shown), a driving device, a gas supply device, and the like. Further, the processing machine 17 is connected to a controller 18 for setting a speed command of a driving device of the processing machine 17, a current command to the laser power supply device, and setting and controlling processing conditions such as a material and a shape of a workpiece. . The controller 18 is connected to the microcomputer control unit 8. Therefore, the laser oscillator 15
The laser beam 19 emitted from the laser beam is radiated to the workpiece 20 via the laser beam transmission means 16 and the processing machine 17 and is provided for a target processing.

Next, the operation of the laser device according to this embodiment will be described. Electric energy is supplied to the laser excitation lamp 7 from the DC power supply 1 and converted into light. Using this light energy as an excitation source, the laser oscillator 15 oscillates and generates a laser beam 19. Laser beam 19
Is irradiated onto the workpiece 20 via the laser beam transmission means 16 and the processing machine 17, and desired processing such as drilling, cutting, welding, and surface modification is performed. At this time, when the user sets appropriate processing conditions in the controller 18 according to the purpose and type of processing, a waveform is set by the user waveform setting device 9 based on the processing conditions.

The output from the processing machine 17 and the DC power supply 1 is controlled by the waveform setting of the user waveform setting unit 9, so that the ripple of the laser output can be reduced and good processing quality can be obtained.

The processing conditions are given to the controller 18 by a recording medium such as a floppy disk, and the processing can be performed automatically.

The user waveform setting device 9 may be incorporated in the controller 18 in some cases.

[0052]

According to the present invention, the switching power loss in the laser power supply device is changed as needed according to the load impedance characteristic, the L value of the filter section, the value of the input DC voltage source, the output waveform setting of the laser, and the like. It is possible to determine in real time whether or not the laser is in a safe operation range, and to obtain a laser power supply device in which the control cycle of the switch is optimized, the reliability of the switching is increased, and the cost is reduced by appropriately designing the switching circuit. .

Further, it is possible to improve the operation reliability of the switching section and to largely reduce the component cost of the switching circuit.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of a laser power supply device of the present invention.

FIGS. 2A to 2E are schematic graphs of current waveform data according to the present invention, in which a control cycle previously set in a microcomputer control unit is changed.

FIG. 3 is a schematic diagram of an output current waveform set by a user of the present invention in a user waveform setting device.

FIGS. 4A to 4D are explanatory diagrams of the contents of control by a microcomputer control unit in the present invention.

FIGS. 5A to 5E are graphs of output current waveforms in each switching control cycle of the switching element according to the present invention.

FIG. 6 is a block diagram of a laser processing apparatus showing a use state of a laser power supply device used for a solid-state laser oscillator according to an embodiment of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... DC current, 2 ... Switching element, 4 ... Inductor, 5 ... Current feedback diode, 6 ... Current detector, 7 ... Laser excitation lamp, 8 ... Microcomputer control unit, 9 ... User waveform setting device

Claims (6)

[Claims] An electric waveform to be supplied to a laser excitation source is set in correspondence with each switching control of a switching element, and each switching control is performed by setting a preset electric value and flowing to the laser excitation source. A laser power supply device that performs a determination based on a comparison with an instantaneous value of an electric monitor and performs control based on the result, wherein the preset set electric value is a plurality of values. 2. The switching device according to claim 1, wherein the switching control of the switching element is performed by counting the number of times of ON / OFF switching and changing a cycle of the switching control according to the counted number. Laser power supply. 3. The switching control of the switching element is performed by adding an electrical monitor instantaneous value at the time of ON / OFF switching and changing a control cycle of the switch according to the added value. Item 2. A laser power supply device according to item 1. 4. The switching control of the switching element supplies electricity to the laser excitation source from a DC power supply via an inductance when the switching element is turned on, and supplies the electricity with a back electromotive force of the inductance when the switching element is turned off. The laser power supply device according to any one of claims 1 to 3, wherein feedback is performed via a diode, and an electric waveform to be supplied to the laser excitation source is set based on the result. 5. A comparison between the set electrical value and an instantaneous value of an electrical monitor flowing to the laser excitation source, wherein a plurality of the set electrical values are sequentially increased from a shorter cycle of the switching control to a longer one. The laser power supply device according to claim 1, wherein the comparison is made by comparing the values. 6. A laser device which operates using the laser power supply device according to claim 1. Description: