JPH02139981A - Discharge controller - Google Patents

Abstract

PURPOSE:To obtain a laser beam having a flat-top waveform by a method wherein a current applied to a continuous discharge lamp by the ON-OFF operation of a switching device is detected and the average value of the current is so control led as to be equal to a predetermined average current value. CONSTITUTION:An average current control circuit 8 controls a current applied to a continuous discharge lamp 3 so as to be a predetermined average current value and one terminal of a comparator 10 is connected to a junction between a current control circuit 7 and a feedback resistor R10 through an integral circuit 9. The voltage drop of the feedback resistor R10 is averaged by the integral circuit 9. The comparator 10 compares a voltage Ve corresponding to the voltage between both the terminals of the continuous discharge lamp 3 with a predetermined voltage Vc corresponding to the average current and gives the deviation voltage between the voltages Ve and Vc to a driving circuit 11. A DC source 13 is connected to the other terminal of the comparator 10 through a variable resistor 12 to obtain the predetermined voltage Vc. The driving circuit 11 ignites respective thyristors constituting a thyristor bridge 1 with a firing angle corresponding to the deviation voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a discharge control device applied, for example, to laser excitation.

(Prior Art) FIG. 3 is a block diagram of such a discharge control device, which is a technology disclosed in Japanese Patent Publication No. 56-54552. In the figure, L is an arc lamp, and a DC main power supply PS1 is connected to the arc lamp L through a diode D1 and the secondary side of a trigger transformer T1 in series.

Note that a trigger transformer drive circuit TC is connected to the secondary side of the trigger transformer T1. Further, PS2 is a booster circuit, and this booster circuit PS2 includes a charging resistor R.
1 and a storage capacitor C are connected, and a connection point between the charging resistor R1° and the storage capacitor C is connected to the secondary side of the trigger transformer Tl via a current limiting resistor R2. Furthermore, PS is a power source for pulsed light emission,
This pulse light emitting power source PS3 has a function of superimposing an AC output on the DC output of the DC main power source PS1.

Its configuration is such that the primary side of a transformer T2 is connected to the AC power supply ES via an on/off switch SW, the anode of a diode D1 is connected to the secondary side of this transformer T2 via a diode D2, and the anode of a diode D3 is connected to the secondary side of the transformer T2 via a diode D2. is connected between the secondary side of the transformer T2 and the diode D2.

With such a configuration, the storage capacitor C is charged by the output of the booster power supply PS2 via the charging resistor R1. Thereafter, at time t shown in FIG. 4, the trigger transformer drive circuit TC is driven to generate a trigger voltage, and this trigger voltage is boosted to a high voltage by the trigger transformer T1 and applied to the arc lamp L. This arc lamp L is activated by this trigger voltage, and the charge stored in the storage capacitor C is transferred to the arc lamp L through the current limiting resistor R2.
, which discharges the arc lamp L and reduces the voltage drop across it. In this way, when the voltage drop of the arc lamp L decreases, the DC main power supply PS1 is driven, and a sustaining discharge current is supplied to the arc lamp L via the diode D3+D1.

In this case, the current 11 supplied to the arc lamp L from the DC main power supply PS1 is set to the minimum discharge sustaining current value of the arc lamp L. Therefore, this minimum discharge sustaining current value ■1
As a result, the arc lamp L continuously emits a small amount of light and releases a small amount of light emission energy to the outside.

When the on/off switch SW is closed at time t2 in this state, the AC voltage from the AC power supply ES is transferred to the transformer T2.
+ Half-wave rectified by diode D2 and diode D1
It is supplied to the arc lamp L via the secondary side of the trigger transformer T1. As a result, as shown in FIG. 4, during the period t2-t3 of the positive half cycle of the AC voltage, the current 11
A positive current from the AC power supply ES is superimposed on the pulse current I2, and a pulse current I2 flows. However, during this period, the arc lamp L emits strong light and emits high light emission energy to the outside.

Next, in the period t3-14, the minimum discharge sustaining current 11 flows through the arc lamp L, and its light emission becomes minute. As a result,
When a laser medium is excited using the strong emission energy thus obtained, high-energy laser light can be oscillated. If this laser beam is used, it can be applied to welding metals and the like.

However, when performing actual welding, the laser beam is required to have a high output and a waveform that maintains energy for a predetermined period of time, that is, a flat-top waveform. However, in the above device, since the alternating current voltage is superimposed, the laser light does not have a flat-top waveform. This results in oscillation of a laser that is inappropriate for actual welding.

Further, the above device must be provided with two power sources, the DC main power source PS1 and the pulsed light emission power source PS3, making its configuration complicated.

(Problems to be Solved by the Invention) As described above, the waveform of the laser beam is inappropriate for actual welding, and the structure is also complicated.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a discharge control device with a simple configuration that can obtain laser light with a flat top waveform.

[Structure of the Invention] (Means for Solving the Problems) The present invention provides a DC power supply circuit that supplies a DC output to one continuous discharge lamp, and a current holding circuit that maintains the minimum current necessary for lighting the continuous discharge lamp. A current control circuit comprising a resistor connected in series to a continuous discharge lamp and a DC power supply circuit, and a high-speed switching element connected in parallel to the current holding resistor, and a high-speed element for controlling on/off of the high-speed switching element. The above-mentioned object is provided with a control circuit and an average current control circuit that detects the current flowing through the continuous discharge lamp by turning on and off a switching element and controls the average value of this current so that it becomes a predetermined average current value. This is a discharge control device that attempts to achieve the following.

(Function) By providing such a means, the high-speed switching element is controlled on/off by the high-speed element control circuit. In this case, during ON control, a large current flows from the DC power supply circuit through the continuous discharge lamp and the high-speed switching element, and during OFF control, a large current flows from the DC power supply circuit through the continuous discharge lamp and the current holding resistor to turn on the continuous discharge lamp. Minimum current flows. Thus, the continuous discharge lamp lights up, and the current value at this time is controlled to a predetermined average current value by the average current control circuit.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration diagram of a discharge control device. A three-phase AC power source is connected to the input side of the silice bridge circuit 1, and a filter circuit 2 composed of a coil and a capacitor is connected to the output side. Incidentally, the silice bridge circuit 1 and the filter circuit 2 constitute a DC power supply circuit. A continuous discharge lamp 3 for excitation is connected to the output terminal (+) of this filter circuit 2 via a diode DIO.
The high voltage side of the is connected. A booster circuit 4 is connected to the connection point between the diode DIO and the continuous discharge lamp 3, and the continuous discharge lamp 3 is equipped with a trigger electrode 5, and a trigger circuit 6 for generating a trigger signal is connected to the trigger electrode 5. It is connected. Further, the low voltage side of the continuous discharge lamp 3 is connected to the output terminal (-) of the filter circuit 2 via a feedback resistor RIO that constitutes a current control circuit 7 and an average current control circuit 8 in series. This average current control circuit 8 controls the current flowing through the continuous discharge lamp 3 to a predetermined average current value, and an integrating circuit 9 is connected to the connection point between the current control circuit 7 and the feedback resistor RIO. One end of the comparator 10 is connected. This integrating circuit 9 averages the voltage appearing across the feedback resistor RIO. The comparator 10 compares a voltage Vθ corresponding to the voltage across the continuous discharge lamp 3 with a set voltage Vc corresponding to the average current value, and provides a deviation voltage between these voltages ve and Vc to the drive circuit 11. Note that a variable resistor 12 is connected to the other end of the comparator 10.
A DC power supply 13 is connected through the terminal to obtain a set voltage VC. The drive circuit 11 fires each thyristor constituting the thyristor bridge circuit 1 at a firing angle according to the deviation voltage.

The current control circuit 7 adjusts the current supplied to the continuous discharge lamp 3 to a large current value and a minimum current value necessary for lighting the continuous discharge lamp 3, and is connected between the continuous discharge lamp 3 and the feedback resistor RIO. A current holding resistor Ra is connected to the current holding resistor Ra, and the drain-source of the field effect transistor Q is connected in parallel to the current holding resistor Ra. A high-speed element control circuit 14 is connected between the gate and source of this field effect transistor Q. This high-speed element control circuit 14 has the function of controlling the field effect transistor Q on and off in response to an on/off signal.

Further, a laser medium 15 such as YAG is arranged in parallel with the continuous discharge lamp 5, and a high reflection mirror 16 and an output mirror 17 are arranged in the longitudinal direction of this laser medium 15.

Next, the laser oscillation effect in the device configured as described above will be explained.

A high voltage is supplied from the booster circuit 4 to the continuous discharge lamp 3, and a trigger signal is transmitted from the trigger circuit 6 to the trigger electrode 5.
Send to. At the same time, when three-phase AC power is supplied to the Cyrisk bridge circuit 1, the Cyrisk bridge circuit 1 rectifies the three-phase AC power and sends it to the filter circuit 2.
This filter circuit 2 smoothes the rectified output. However, the DC current 1a output from the filter circuit 2 is supplied to the continuous discharge lamp 3 through the diode DIO.

By the way, if the field effect transistor Q is in the off state at this time, the current! a is a diode DIO1 continuous discharge lamp 3. Current holding resistor Ra and feedback resistor RI
flows through O. Therefore, the current value at this time is the minimum value IL necessary to discharge the continuous discharge lamp 3, as shown in FIG. Therefore, continuous discharge lamp 3
The emission energy of is very small.

In this state, when an on signal is applied to the high speed element control circuit 12 at time tlo, the high speed element control circuit 14 applies a voltage to the gate of the field effect transistor Q to turn the field effect transistor Q on. This causes the current IL to flow through the diode Din.

It flows through the continuous discharge lamp 3 and the feedback resistor RIO. Therefore, the current does not pass through the current holding resistor Ra, and the current 1a increases to a large value 1.0 as shown in FIG. It flows constantly. Therefore, at this time, the emission energy of the continuous discharge lamp 3 increases.

Thus, the laser medium 15 is excited, and the high reflection mirror 1
6 and the output mirror 17, a laser beam P is outputted. Then, when an off signal is applied to the high-speed element control circuit 14 at time tll, the high-speed element control circuit 14 turns the field effect transistor Q off.

However, the current 1a supplied to the continuous discharge lamp 3 becomes the minimum value IL necessary for discharging again. Next, period t1
When the field effect transistor Q is turned on again at 2-1it, a large current of 1° flows through the continuous discharge lamp 3. That is, the current 1a is modulated by the high-speed on/off of the field effect transistor Q. Note that the average value of the electric power supplied to the continuous discharge lamp 3 is set to be equal to or less than the rating of the continuous discharge lamp 3. Furthermore, even at this time, the comparator 8 applies feedback to the Sirisk bridge using the average current to stabilize the current.

In this way, in the above embodiment, 'current holding resistor R
A current control circuit 7 consisting of a and a field effect transistor Q
Since the current waveform is connected to the continuous discharge lamp 3, the current waveform supplied to the continuous discharge lamp 3 can be a rectangular wave with fast rise and fall, that is, a waveform with a flat top. Therefore, this current 1B
The laser light obtained by emitting light from the continuous discharge lamp 3 has the same waveform as the current Ia, so it has high output and lasts for a predetermined period of time, making it ideal for welding and the like. Furthermore, since the field effect transistor Q is turned off while it is on, it is possible to perform on/off control at high speed. For example, when the field effect transistor Q is on/off controlled with a duty ratio of 50%, 9.
Conversion can be performed at a rise time of about 5 ms and at a high speed of about kHz. Furthermore, since feedback is applied to the averaged current of the on-off controlled current and supplied to the continuous discharge lamp 3, the ripple in the current a is very small. for example,
When a current of 30 [A] is supplied to the continuous discharge lamp 3 in a YAG laser, the ripple rate is ±3% (effective value). Even if this current is controlled on and off, the stability of the flat top is comparable to that of continuous discharge. Furthermore, a current control circuit 7 and a high-speed element control circuit 1
4, the configuration is simple and simple.

Note that the present invention is not limited to the above-mentioned embodiment, and may be modified without departing from the spirit thereof. For example, although the Sirisk bridge circuit 1 and the filter circuit 2 are used as the DC power supply circuit, the present invention is not limited to this, and other circuit configurations may be used. In this case, a DC power supply circuit with slow response may be used. Furthermore, the high-speed switching element is not limited to the field effect transistor Q, but other elements may be used.

[Effects of the Invention] As described in detail above, according to the present invention, it is possible to provide a discharge control device with a simple configuration that can obtain laser light with a flat-top waveform.

[Brief explanation of the drawing]

1 and 2 are diagrams for explaining one embodiment of the discharge control device according to the present invention, in which FIG. 1 is a configuration diagram, FIG. 2 is an operation timing diagram, and FIGS. The figure is a diagram for explaining a conventional device. DESCRIPTION OF SYMBOLS 1... Cyrisk bridge circuit, 2... Filter circuit, 3... Continuous discharge lamp, 4... Booster circuit,
5... Trigger electrode, 6... Trigger circuit, 7... Current control circuit, 8... Average current control circuit, 9... Integrating circuit, 10... Comparator, 11... Drive circuit ,
12... Variable resistance, 13... DC power supply, 14...
High-speed element control circuit, Ra...current holding resistance, Q...
Field effect transistor, 15...Laser medium, 16.
...High reflection mirror 17... Output mirror applicant's agent Patent attorney Takehiko Suzue

Claims (1)

[Claims] a DC power supply circuit that supplies DC output to a continuous discharge lamp;
A current holding resistor is connected in series to the continuous discharge lamp and the direct current power supply circuit, and a high speed switching element is connected in parallel to the current holding resistor, so that the continuous discharge lamp has a minimum current necessary for lighting. a current control circuit consisting of a current control circuit, a high-speed element control circuit that controls on/off of the high-speed switching element, and a current flowing through the continuous discharge lamp due to the on/off of the switching element, and an average value of this current is determined in advance. 1. A discharge control device comprising: an average current control circuit that controls the average current value to be the average current value.