JPH05152653A - Power supply device for laser pumping lamp - Google Patents

Abstract

PURPOSE:To accurately control a current supplied to a lamp with satisfactory response. CONSTITUTION:In a power supply device for a laser pumping lamp according to the present invention, there is provided a circuit for applying a current control signal VC to a current control device 3 by receiving a current setting signal VIN as a current control circuit 10 for providing the current control signal VC applied to the current control device 3 for controlling a current to be fed to the laser pumping lamp 1. Herein, the circuit is provided which is to apply the current control signal VC to the current control device 3 such that a current is adapted to flow through the current control device 3, which is proportional to the current setting signal VIN by negatively feeding back a signal V2 corresponding to a current I detected by a current detection element 4 to an input side. Hereby, there is ensured accurate current control with satisfactory response.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply unit for a laser pumping lamp used as a power supply for a flash lamp for pumping a solid laser medium.

[0002]

2. Description of the Related Art As a power supply device for a laser excitation lamp, for example, the device disclosed in Japanese Patent Application Laid-Open No. 1-223789 is known.

In short, the device disclosed in the above publication enables on / off control of the current supplied from the DC power supply to the flash lamp by means of a switching element, and detects the current supplied to the flash lamp. By changing the ON / OFF pulse width of the switching element according to the current, the current supplied to the flash lamp can be controlled to a predetermined value.

[0004]

By the way, in recent years, a laser medium is excited by a flash lamp to cause laser oscillation, and the intensity of laser light generated by this laser oscillation is monitored to make the laser light intensity a predetermined intensity. So that
There is a demand to control the current supplied to the flash lamp. In order to meet this demand, it is necessary to precisely adjust the current supplied to the flash lamp within one energization time to the flash lamp. That is, since the time for energizing the flash lamp once is usually several hundreds to several hundreds of μsec, it is necessary to accurately control the current to a predetermined value within this time.

However, since the above-mentioned conventional device controls the current by the on / off control, it is theoretically impossible to perform the current control in an instantaneous time shorter than the on / off cycle. Here, the ON / OFF cycle is regulated by the rising characteristics of the discharge current determined by the impedance of the discharge circuit including the flash lamp, and cannot be shortened further. For example,
As a general flash lamp, consider a case where a flash lamp 6F3 (trade name) manufactured by ILC is used and discharged at a charging voltage of 500V. When the line resistance is set to 0.1 ohm, the peak current of 640A is reached. About 6
A rise time of 0 μsec is required. Therefore, for example, 600A from this peak current by ON / OFF control.
In order to perform the control to reduce the current up to, the on / off cycle must be set to about 100 μsec. That is, it is not possible to change the current in a time shorter than this cycle, and therefore, in the above-described conventional device, it is necessary to precisely adjust the current supplied to the flash lamp within one energization time of the flash lamp. We cannot fully meet the above requests. Moreover, in this control, since the current flowing through the flash lamp is an average value of repeated on / off, the control accuracy has a certain limit.

As described above, the conventional device has a problem that the control response and the control accuracy are not sufficient depending on the application.

The present invention has been made under the background described above, and an object thereof is to provide a power supply device for a laser excitation lamp capable of controlling the current supplied to the lamp with good response and accurately. It is what

[0008]

In order to solve the above-mentioned problems, the present invention provides (1) a laser excitation lamp, a DC power supply for supplying electric power for causing the laser excitation lamp to emit light, and a DC power supply. A current control element for controlling a current flowing through the laser excitation lamp with a current control signal, a current control circuit for obtaining a current control signal of the current control element, and a current flowing from the DC power supply to the laser excitation lamp. The current control circuit is a circuit for inputting a current setting signal and applying a current control signal to the current control element, which corresponds to the current detected by the current detection element. A circuit for adding a current control signal to the current control element so that a current proportional to the current setting signal flows through the current control element by negatively feeding back the signal to the input side. The configuration is characterized by that.

As a mode of the configuration 1, (2)
In the power supply device for the laser excitation lamp of configuration 1, an isolation power supply insulated from the DC power supply is used as a current control circuit power supply for driving the current control circuit, and the common potential of the current control circuit power supply is The configuration is characterized in that it is made common to the anode potential of the laser excitation lamp and that the current setting signal is input to the current control circuit via an isolation amplifier.

Further, as an aspect of the configuration 1 or 2,
(3) In the power supply device for the laser excitation lamp of configuration 1 or 2, the current setting signal is a signal related to an external physical quantity that changes in association with the light emission of the laser excitation lamp. The current flowing through the current control element is controlled so that the external physical quantity has a predetermined value.

[0011]

According to the above configuration 1, the signal corresponding to the current detected by the current detecting element is negatively fed back to the input side so that the current proportional to the current setting signal flows through the current controlling element. Since the current control signal is applied to, it is possible to control the current instantaneously and also to perform precise control. Moreover, the control state can be easily set to the optimum state according to the application by changing the negative feedback amount.

According to the configuration 2, the isolation power supply insulated from the DC power supply is used as the power supply for the current control circuit, and the common potential of the power supply for the current control circuit is common to the anode potential of the laser excitation lamp. In addition, the current setting signal is input to the current control circuit via the isolation amplifier, so the anode potential of the laser excitation lamp will not change even if negative feedback is applied directly to the input side. Since the change does not affect the operation of the current control circuit, the laser excitation lamp can be used with the cathode grounded. As a result, it becomes possible to apply the preliminary current and the trigger voltage applied to the laser excitation lamp from a route different from the application route of the DC power supply.

Further, according to the configuration 3, for example, when the intensity of the laser light obtained by exciting the laser medium with the laser exciting lamp is selected as the external physical quantity, the oscillated laser light has a predetermined intensity. It becomes possible to control.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing a main configuration of a power supply device for a laser excitation lamp according to an embodiment of the present invention, FIG. 2 is a diagram showing an overall configuration of one embodiment, and FIG. 3 is a diagram showing a current control circuit. FIG. 4 is an operation explanatory diagram, and FIG. 4 is an operation explanatory diagram of the current control circuit when the negative feedback amount is changed. Hereinafter, a power supply device for a laser excitation lamp according to an embodiment will be described in detail with reference to these drawings.

1 and 2, reference numeral 1 is a flash lamp which is a laser excitation lamp, reference numeral 2 is a DC main power supply, reference numeral 3 is a current control element, reference numeral 4 is a current detection element, reference numeral 11 is an isolation power supply, and reference numeral Reference numeral 12 is a controller that sends out a current setting signal, and reference numeral 13 is an isolation amplifier.

In FIG. 2, the flash lamp 1 includes:
Light emission power is supplied from the DC main power source 2 through the current control element 3, the current detection element 4, and the backflow prevention diode 5.

The flash lamp 1 is composed of a lamp such as a xenon flash lamp. The flash lamp 1 includes a simmer power supply 6 for passing a preliminary current through the flash lamp 1, a resistor 7 and a backflow prevention diode 8.
It is connected in parallel with the DC power supply 2 via. Further, a simmer starter 9 for starting energization of a preliminary current from a simmer power source 6 is connected to the flash lamp 1. The flash lamp 1 emits light in accordance with the current flowing through the flash lamp 1 by passing a pulse current from the DC power supply 2 in a state where a preliminary current is supplied by the simmer power supply 6. In this embodiment, a DC power source of 1600 V and 1000 mA was used as the simmer power source 6. The simmer starter 9 applies a high voltage pulse of about 10 KV to the flash lamp 1.

The DC main power supply 2 comprises a charging power supply 21 and a charging capacitor 22. In this embodiment, a 500V, 2.5A DC power source is used as the charging power source 21, and the capacity of the charging capacitor 22 is 8.
Two electrolytic capacitors having a withstand voltage of 400 V at 2 mF were connected in series to obtain a capacitor having a capacity of 4.1 mF and a withstand voltage of 800 V. As a result, when the discharge amount per pulse is set to 60 J and the number of pulse repetitions is set to 20 pps or less, the voltage drop of the charging voltage is set to several percent (30
It can be kept below about V), and if charged at 2.5 A, charging is completed within 40 msec.

The current control element 3 is composed of a field effect transistor (FET), its drain (D) terminal is connected to the DC main power source 2 side, and its source (S) terminal is the anode (A) of the flash lamp 1. The gate (G) terminal is connected to the current control circuit 10 while being connected to the side. That is, by controlling the voltage applied to the gate of the current control element 3 by the current control circuit 10, the current between the drain and the source is controlled to control the current flowing to the flash lamp 1. In this embodiment, as the current control element 3, 24 FETs having a breakdown voltage of 700 V and a maximum continuous drain current of 7.8 A were used in parallel. Thus, considering the voltage applied to the current control element 3 (voltage obtained by subtracting the voltage applied to the flash lamp 1 from the voltage of the DC main power supply 2) and the flowing current, the pulse width 3
If 00 μsec or less, up to 600 A is within the safe operation area of the FET. In addition, as such FET,
For example, IRF PE manufactured by International Rectifier
50 (trade name) can be used.

The current detecting element 4 is composed of a precision shunt resistor R _{3 having a} resistance of 5 mΩ and produces a voltage V ₂ across the resistor, which is proportional to the current passing through the resistor.

The current control circuit 10 is driven by the isolation power supply 11 and negatively feeds back the voltage V ₂ corresponding to the current detected by the current detection element 4 to the input side, and the controller 12 via the isolation amplifier 13. A current control signal V is applied to the current control element 3 so that a current proportional to the input current setting signal V _IN flows through the current control element 3.
_G is applied.

FIG. 1 is a diagram showing a detailed structure of a current control circuit 10 which is a main part structure of one embodiment.

In FIG. 1, the current setting signal V _IN is supplied to the base (B) of the transistor Tr ₂ via the input resistor R _4.
Added to. The collector (C) of the transistor Tr ₂ is connected to the + 15V power supply of the isolation power supply 11, while the emitter (E) is connected to the −15V power supply of the isolation power supply 11 via the resistor R ₅ (1K ohm). ing. Further, the emitter (E) of the transistor Tr ₂ is connected to the base (B) of the transistor Tr ₁ via the resistor R _1, and
The base (B) of r ₁ is connected to the current detecting element 4 via the resistor R _2.
Is connected to one end, that is, the connection side to the current control element 3. The collector (C) of the transistor Tr ₁ is connected to the drain (G) of the current control element 3 and also connected to the + 15V power source of the isolation power source 11 via the resistor R ₆ (510 ohm), while The emitter (E) is connected to the common of the isolation power supply 11, and is also connected to the other end of the current detection element 4, that is, the connection side to the flash lamp 1.

According to the above circuit configuration, the drain-source current I of the current control element 3 is expressed by the following equation (1).

I = − {R ₂ / (R ₁ · R ₃ )} V _IN + {V _BE1 + (R ₂ / R ₁ ) V _BE1 + R ₂ · i ₀ } / R ₃ (1) However, In the formula (1), V _BE1 is a transistor Tr
₁ base-emitter voltage, i ₀ is the transistor T
It is the collector current of r ₁ . FIG. 3 is a graph showing the equation (1). In FIG. 3, the vertical axis represents the drain-source current I of the current control element 3, and the horizontal axis represents the current setting signal V _IN . As is apparent from FIG. 3, the drain-source current I of the current control element 3 is proportional to the current setting signal V _IN , and the relationship between the two is represented by a straight line with an angle θ. Here, the angle θ is the arctangent of the coefficient of the first term on the right side of the equation (1), and I _OFFSET is the second term on the right side.
The value of the term. That is, θ = tan ⁻¹ {R ₂ / (R ₁ ·
R ₃ )}, I _OFFSET = {V _BE1 + (R ₂ / R ₁ ) V _BE1
+ R ₂ · i ₀ } / R ₃ .

Therefore, as the current setting signal V _IN ,
If you use a pulse that rises from + V _B to the negative side,
The relationship between the pulse wave height V _{INA of} V _IN (horizontal axis) and the current I (vertical axis) is as shown in FIG. In FIG. 4, each straight line is a straight line when the resistance R ₂ is changed.
That is, by changing the resistance R ₂ , the amount of negative feedback can be changed to change the slope of the straight line, and appropriate control can be performed.

The isolation power supply 11 is a power supply that floats between the input side (primary side) and the output side (secondary side). In this embodiment, a two-output power supply COP02 (made by TDK Corporation) SH) (trade name) was used.

The controller 12 has a pulse wave height of 0 to 1
5V, pulse width 100～300Myusec, in which the repetition frequency is a built-in pulse generator capable of delivering an arbitrary rectangular wave range 0～20Pps, the current setting signal V _IN
Is transmitted. That is, a signal for repeatedly causing the flash lamp 1 to emit light within this repeating frequency range is transmitted.

The isolation amplifier 13 is a device having a function of electrically insulating the input circuit and the output circuit by floating the input terminal. In this embodiment, the isolation amplifier ISO106 manufactured by Nippon Burr Brown Co., Ltd. is used. (Trade name) was used.

In the above structure, the flash lamp 1
In order to repeatedly emit light at a predetermined repetition frequency, first, the simmer power source 6 is turned on by the simmer starter, and a simmer current (preliminary current) of about 100 mA is applied to the flash lamp 1. Next, the controller 12 is operated to send a current setting signal (pulse) corresponding to the light emission time, the light emission repetition period, and the light emission intensity (current value flowing to the flash lamp 1) to the current control circuit 10. As a result, a current according to the current setting signal flows through the current control element 3, causing the flash lamp 1 to emit light.

According to this embodiment, the current control circuit 10
Is the voltage (V that corresponds to the current detected by the current detection element 4
₂ ) is negatively fed back to the input side to apply the current control signal V _B to the current control element 3 so that the current I proportional to the current setting signal V _IN flows to the current control element 3. In addition, instantaneous current control becomes possible, and precise control becomes possible. Moreover, the control state can be easily set to the optimum state according to the application by changing the negative feedback amount.

An isolation power supply 11 insulated from the DC main power supply 2 is used as a power supply for driving the current control circuit 10, and the common (P point) potential of the isolation power supply 11 is the anode of the flash lamp 1. (Q
Point) Since the current setting signal V _IN is input to the current control circuit 10 via the isolation amplifier 13 while being common to the potential, even if negative feedback is directly applied to the input side. Since the change in the anode potential of the flash lamp 1 does not affect the operation of the current control circuit 10, the flash lamp 1 can be used with the cathode grounded. As a result, the simmer current applied to the flash lamp 1 and the trigger voltage of the simmer starter 9 can be applied from a route different from the application route of the DC main power supply 2.

Also, the controller 12 is controlled by an external control signal corresponding to an external physical quantity so that the current setting signal to be sent changes depending on this external signal. When a signal related to the intensity of the laser light obtained by exciting the laser medium is selected, the oscillation laser light can be controlled to have a predetermined appropriate intensity.

For example, when processing a material having a high surface reflection such as stainless steel with an oscillating laser beam, it is necessary to irradiate a high-power laser beam at the initial stage of processing, but the surface is altered and absorbed. If the laser output is not reduced from the time when the rate starts to increase, excessive processing will occur. Therefore, in such a case, the physical quantity that depends on the absorption coefficient of the workpiece (external physical quantity) is selected as the external control signal, so that the oscillation laser light intensity is controlled to always be the optimum intensity for processing. It is possible to perform desired processing. Further, for example, when processing a work piece in which a plurality of different kinds of materials are mixed and the light absorption coefficient is different depending on the processing place, the physical quantity depending on the absorption coefficient of the work piece is externally controlled. By selecting the signal as a signal, the intensity of the oscillated laser light can be controlled so as to be always the optimum intensity for processing, and desired processing can be performed.

In the above-described embodiment, the FET is used as the current control element, but an IGBT (Insulated Gate Transistor), a giant transistor or the like having the same function may be used.

Although the parallel feedback parallel injection method is used as the negative feedback method in the current control circuit in the above embodiment, the parallel feedback series injection method may be used.

[0037]

As described in detail above, the power supply device for the laser excitation lamp according to the present invention is used as a current control circuit for obtaining a current control signal to be applied to the current control element for controlling the current flowing through the laser excitation lamp. , A circuit for inputting a current setting signal and applying the current control signal to the current control element, in which a signal corresponding to the current detected by the current detection element is negatively fed back to the input side and proportional to the current setting signal. By providing the circuit for applying the current control signal to the current control element so that the current flows through the current control element, it is possible to perform accurate current control with good responsiveness.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an overall configuration of an embodiment.

FIG. 3 is an operation explanatory diagram of a current control circuit.

FIG. 4 is an operation explanatory diagram of a current control circuit when the amount of negative feedback is changed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Flash lamp, 2 ... DC main power supply, 3 ... Current control element, 4 ... Current detection element, 10 ... Current control circuit, 11 ... Isolation power supply, 12 ... Controller, 13 ... Isolation amplifier.

Claims (3)

[Claims] 1. A laser excitation lamp, a DC power supply for supplying electric power for causing the laser excitation lamp to emit light, and a current control element for controlling a current flowing from the DC power supply to the laser excitation lamp by a current control signal. A current control circuit that obtains a current control signal of the current control element, and a current detection element that detects a current flowing from the DC power supply to the laser excitation lamp, and the current control circuit is a current setting signal. Is a circuit for inputting a current control signal to the current control element, wherein a signal corresponding to the current detected by the current detection element is negatively fed back to the input side to generate a current proportional to the current setting signal. A power supply device for a laser excitation lamp, comprising a circuit for applying a current control signal to the current control element so as to flow to the current control element. 2. The power supply device for a laser excitation lamp according to claim 1, wherein an isolation power supply insulated from said DC power supply is used as a power supply for a current control circuit which drives said current control circuit, and this current is used. The common potential of the power supply for the control circuit is made common with the anode potential of the lamp for laser excitation, and the current setting signal is input to the current control circuit via an isolation amplifier. Power supply device for the characteristic laser excitation lamp. 3. The power supply device for a laser excitation lamp according to claim 1, wherein the current setting signal is associated with an external physical quantity that changes in association with the light emission of the laser excitation lamp. A power supply device for a laser excitation lamp, wherein a current flowing through the current control element is controlled so that the external physical quantity has a predetermined value by using a signal.