JPH08187575A - Power unit for dc arc welding - Google Patents

Abstract

PURPOSE: To prevent a switching element from damage due to biased magnetization of a transformer by providing appropriate non-operating time synchronizing to oscillating frequency of modulation reference signal oscillating circuit and turning a first and second switching element alternately to ON or OFF. CONSTITUTION: A subtracting pulse width modulation signal V21a and adding pulse width modulation signal V21b are inputted in a synchronizing circuit 25. First switching elements 4a, 4d and second switching elements 4b, 4c are converted to a first synchronizing signal V25a and second synchronizing signal V25b, the first switching elements 4a, 4d and second switching elements 4b, 4c are respectively turned to ON or OFF. Thus, the integral signal V18 proportional to the magnetic flux of transformer 6 is controlled so as not to increase in one direction, the magnetic flux of transformer 6 is not increased in one direction, the magnetic flux density of iron core is not reached to the saturated magnetic flux density.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a DC arc welding power supply device which prevents a transformer from being magnetized.

[0002]

[Prior art]

[Prior Art 1] FIG. 1 is a circuit diagram of a power supply device for DC arc welding according to prior art 1. In the figure, reference numeral 1 is a three-phase commercial power source having a constant current characteristic, and this three-phase commercial power source is converted into a DC voltage by the first rectifying circuit 2 and the smoothing capacitor 3. 4a and 4d are first switching elements, 4b and 4c are second switching elements,
These switching elements 4a to 4d are switching power transistors arranged in a full bridge type.

A synchronous circuit 25, which will be described later, gives a predetermined rest time to the first switching elements 4a and 4d and the second switching elements 4b and 4c to alternately conduct or non-conduct them, thereby generating a DC voltage. Converted to AC pulse voltage and output each positive and negative voltage. This AC pulse voltage is converted into an AC pulse voltage suitable for the load by the transformer 6 having the primary winding 6a and the secondary winding 6b, and the second rectifier circuit 7 and the filter reactor 8 that output the output voltage V0. Is converted to a DC voltage by and. This DC voltage is supplied to the welding load PA including the electrode 9, the arc 30, and the workpiece 10.

The electromagnetic energy stored in the leakage inductance 11 of the transformer 6 is supplied to the feedback diodes 5a through 5d during the rest period between the first switching elements 4a and 4d and the second switching elements 4b and 4c. 5d
Is fed back to the smoothing capacitor 3 via. In addition, the electromagnetic energy stored in the filter reactor 8 is
It is returned to the electrode 9 and the object to be welded 10 via the rectifying circuit 7.

An output current detection circuit 24 detects an output current and outputs an output current detection signal V24. 1
Reference numeral 3 denotes an output current setting circuit, which is an output current setting signal V1.
3 is output. The current value of the welding load PA is determined by the value of the output current setting signal V13. 23 is P
An output current compensating circuit including an ID (Proportion Integration Differential) compensating circuit and the like, which receives an output current detection signal V24 and an output current setting signal V13,
The output current compensation signal V23 for keeping the output current constant is output. Reference numeral 19 denotes a modulation reference signal oscillation circuit, which outputs a modulation reference signal V19. Reference numeral 21 denotes a pulse width modulation circuit for determining the conduction time ratio of the switching elements 4a to 4d, which inputs the modulation reference signal V19 and the output current compensation signal V23 and outputs the pulse width modulation signal V21.

Reference numeral 25 denotes a synchronizing circuit, which receives the pulse width modulation signal V21 and the modulation reference signal V19 and outputs the first synchronizing signal V25a and the second synchronizing signal 25b to the modulation reference signal oscillating circuit 19. Output in synchronization with the oscillation cycle. 16
Is a base circuit, and when the first synchronization signal V25a is input, the base signal V16a of the switching element 4a
And the base signal V16d of the switching element 4d are output, and when the second synchronization signal V25b is input, the base signal V16b of the switching element 4b and the base signal V16c of the switching element 4c are output to output the first switching element 4a. And 4d and the second switching elements 4b and 4c are not turned on at the same time to prevent breakage of the switching elements 4a to 4d.

FIG. 2 is a diagram showing the waveform of the output signal of each part of the circuit diagram shown in FIG. In FIG. 2, (A) shows the waveform of the output V19 of the modulation reference signal oscillation circuit 19,
(B) shows the waveform of the output V23 of the output current compensation circuit 23, (C) shows the waveform of the output V21 of the pulse width modulation circuit 21, and (D) shows the waveform of the output V25a of the synchronization circuit 25. 8E shows the waveform of the output V25b of the synchronization circuit 25.

At time t = t0, the switching element 4a is activated by the operation of a welding start switch (not shown).
The switching operation of 4d to 4d is started. Welding load P
When the output current compensation signal V23 changes as shown in FIG. 7B due to a change in A, a rapid change in the output current setting signal V13, or the like, the switching elements 4a to 4d.
The first synchronization signal V25a and the second synchronization signal V25b for turning on the switch change as shown in FIGS. As a result, the ON time of the first switching elements 4a and 4d is equal to the ON time of the second switching elements 4b and 4d.
It becomes shorter than the ON time of c, the magnetic flux of the iron core of the transformer 6 increases in one direction, and magnetic bias occurs. When this state continues and the magnetic flux density of the iron core of the transformer 6 reaches the saturation magnetic flux density, the inductance of the primary side of the transformer 6 becomes very small, and as a result, the switching elements 4a to 4d exceed the rating. An electric current may flow and cause destruction.

[Prior Art 2] FIG. 3 is a circuit diagram of a power supply device for DC arc welding according to the prior art 2. FIG. 1 is a diagram showing a power supply device that solves the problem of the conventional technique 1 shown in FIG. 1, in which a bias magnetic prevention capacitor 17 is connected in series with the primary winding 6a of the transformer 6. The other circuits are the same as those in FIG.

In FIG. 3, the first switching elements 4a and 4d of the voltage applied to the primary winding 6a of the transformer 6 are shown.
When the integrated value of the ON time of 1 is different from the integrated value of the ON time of the second switching elements 4b and 4c, a current having a DC component flows in the bias magnetic prevention capacitor 17. The voltage applied across the primary winding 6a of the transformer 6 is increased or decreased by the DC voltage generated across the bias magnetizing prevention capacitor 17 due to this DC current component. As a result, the first switching element 4 of the voltage applied to the primary winding 6a of the transformer 6
The integrated value of the ON time of a and 4d becomes equal to the integrated value of the ON time of the second switching elements 4b and 4c,
Since the magnetic flux of the iron core of the transformer 6 is proportional to the integrated value of the voltage applied to the primary winding 6a, it is possible to prevent magnetic bias.

In FIG. 3, the first switching element 4
During the ON time of a and 4d, the bias magnetic prevention capacitor 17
The voltage Vc at both ends increases in the direction of the arrow shown in FIG.
On the contrary, during the ON time of the second switching elements 4b and 4c, the voltage Vc across the demagnetization preventing capacitor 17 increases in the direction opposite to the arrow. The voltage across the primary winding 6a of the transformer 6 is a DC voltage obtained by converting the voltage of the three-phase commercial power source 1 by the first rectifier circuit 2 and the smoothing capacitor 3 and the voltage across the bias magnetizing prevention capacitor 17 Vc. And the integrated value of the ON time of the first switching elements 4a and 4d of the voltage applied to the primary winding 6a of the transformer 6,
The integrated value of the ON time of the second switching elements 4b and 4c becomes equal.

For example, when the ON time of the first switching elements 4a and 4d becomes longer than the ON time of the second switching element, the voltage Vc across the bias magnetic prevention capacitor 17 changes in the direction of the arrow shown in FIG. Occurs in. Transformer 6
Since the voltage between both ends of the primary winding 6a becomes the difference between the above-mentioned DC voltage and the voltage Vc across the bias magnetic prevention capacitor 17, the transformers are turned on during the ON time of the first switching elements 4a and 4d. The voltage across the primary winding 6a of 6 becomes smaller than the DC voltage. On the contrary, during the ON time of the second switching elements 4b and 4c, the voltage across the primary winding 6a of the transformer 6 becomes larger than the DC voltage. As a result, the switching time of the first switching elements 4a and 4d is 1
The primary winding 6a of the transformer 6 at the integrated value of the voltage across the secondary winding 6a and the ON time of the second switching elements 4b and 4c
Since the integrated value of the voltage across both ends becomes equal, it is possible to prevent magnetic bias.

[Prior Art 3] FIG.
FIG. 38 is a circuit diagram of a DC arc welding power supply device of Conventional Art 3 disclosed in No. 38. In the figure, 31 is a second current detection circuit inserted in the primary side of the transformer 6,
The primary current detection signal V31 is output. Reference numeral 12 denotes a bias magnetic discriminating circuit, which detects a DC component from the primary current detection signal V31 and outputs a bias magnetic discriminating signal V12 proportional to the DC component. Reference numeral 14 is a reference time correction circuit that determines the ON time of the switching elements 4a to 4d. The bias magnetic discriminating signal V12 and the output current setting signal V13 are input to the output current setting signal V13. Of the added modulation reference signal V14a and the output current setting signal V13
And a subtraction modulation reference signal V14b having a value obtained by subtracting the eccentricity determination signal V12. That is, the eccentricity determination signal V1
When 2 is positive, the addition modulation reference signal V14a increases,
The subtraction modulation reference signal V14b decreases. Declination determination signal V
When 12 is negative, the addition modulation reference signal V14a decreases and the subtraction modulation reference signal V14b increases.

The first and second pulse width modulation circuits 15a and 15b perform pulse width modulation on the addition modulation reference signal V14a and the subtraction modulation reference signal V14b, respectively, to obtain first and second pulse width modulation signals V15a and V15b. Are output respectively. Reference numeral 16 denotes a base circuit, which is used for the switching element 4 while the addition modulation reference signal V15a is being input.
The base signal V16b of b and the base signal V16c of the switching element 4c are output to turn on the second switching elements 4b and 4c. In addition, the base circuit 16 outputs the base signal V16a of the switching element 4a and the base signal V16d of the switching element 4d while the subtraction modulation reference signal V15b is being input, and turns on the first switching elements 4a and 4d. .

As described above, when the bias magnetizing discrimination signal V12 is positive, the ON time of the first switching elements 4a and 4d is increased and the O of the second switching elements 4b and 4c is increased.
N hours are reduced. On the contrary, when the magnetic bias discrimination signal V12 is negative, the ON time of the first switching elements 4a and 4d is reduced, and the O of the second switching elements 4b and 4c is reduced.
N hours increase. When the bias magnetic discriminating circuit 12 discriminates that a DC component is generated in the primary side current of the transformer 6 by such control, the ON time of the switching elements 4a to 4d is controlled so as to reduce the DC component. To do. The prior art 3 attempts to prevent the switching elements 4a to 4d from being destroyed by using the circuit described above.

[0030]

Prior Art 2 shown in FIG.
In order to prevent the demagnetization of the transformer 6, the demagnetization prevention capacitor 17 is connected in series with the transformer 6, so that when the output capacity of the power supply becomes large, the demagnetization prevention capacitor 17 Has a large capacity and the power supply device becomes large. Further, in order to compensate for the decrease in the output voltage due to the voltage drop generated in the bias prevention capacitor 17, the winding ratio of the transformer 6 is made smaller than that when the bias prevention capacitor 17 is not provided, or Magnetism prevention capacitor 1
Since the capacity of 7 must be increased, the power supply device becomes expensive and becomes large in size. Further, if the capacity of the bias magnetic prevention capacitor 17 is increased, the voltage drop due to the direct current component is reduced, so that the effect of the bias magnetic prevention is reduced. Therefore, the capacity of the bias magnetic prevention capacitor 17 should be determined. Was difficult.

Also in the prior art 3 shown in FIG. 4, since the direct current component of the transformer 6 is controlled to be zero, the output current setting signal value is set or the welding load P is set.
If the output current value changes significantly due to fluctuations in A, etc.,
Whether the direct current component is generated in the primary side current due to the demagnetization of the iron core of the transformer 6, or the direct current component is generated in the primary side current of the transformer 6 due to the fluctuation of the welding load PA. There is a problem that the circuit does not operate normally because it cannot be distinguished.

[0040]

A direct-current arc welding power source device according to claim 1 is for rectifying a three-phase commercial power source 1 to obtain a direct-current voltage, and for smoothing the direct-current voltage. Smoothing capacitor 3, first switching elements 4a and 4d for converting DC voltage to high frequency AC pulse voltage and outputting positive and negative voltages, and second switching element 4b.
And 4c, a transformer 6 for converting a high frequency AC pulse voltage into an AC pulse voltage suitable for a load, and a second rectifying circuit 7 for rectifying the output of the transformer 6 and supplying the output voltage V0 to the welding load PA. In the power supply device for DC arc welding equipped with, the magnetic flux detection winding 6c that generates a winding output voltage value V10 proportional to the rate of change of the magnetic flux of the iron core of the transformer 6 and the winding output voltage value V10 are integrated. Integrating circuit 18 which outputs an integrated signal V18 and an output current detection signal V which detects an output current
The output current detection circuit 24 that outputs 24, the output current setting circuit 13 that outputs the output current setting signal V13 corresponding to the output current value, the output current detection signal V24, and the output current setting signal V13 are input and output. An output current compensation circuit that outputs an output current compensation signal V23 that has been subjected to one or more calculations of proportionality, integration, and differentiation with respect to the difference between the output current detection signal V24 and the output current setting signal V13 to keep the current constant. 23 and a modulation reference signal V1 having a constant frequency and a constant amplitude
Modulation reference signal oscillation circuit 19 for outputting 9 and integrated signal V
18 and the modulation reference signal V19 are input and the modulation reference signal V
Addition modulation reference signal V2 obtained by adding the integration signal V18 to 19
0b and a modulation signal correction circuit 20 that outputs a subtraction modulation reference signal V20a obtained by subtracting the integration signal V18 from the modulation reference signal V19, an output current compensation signal V23, an addition modulation reference signal V20b, and a subtraction modulation reference signal V20a. The pulse width modulation circuit 21 that outputs the addition pulse width modulation signal V21b and the subtraction pulse width modulation signal V21a, and the modulation reference signal V19, the addition pulse width modulation signal V21b, and the subtraction pulse width modulation signal V21a are input. Of the synchronization signal V25a and the second synchronization signal V25b are output in synchronization with the oscillation cycle of the modulation reference signal oscillation circuit 19.
When the first synchronizing signal V25a is input, the base signals V16a and V16 are applied to the first switching elements 4a and 4d.
A power supply device for DC arc welding, comprising: a base circuit 16 which outputs base signals V16a and V16d to the second switching elements 4b and 4c when 16d is output and a second synchronizing signal is input.

A DC arc welding power source device according to a second aspect of the present invention includes a first rectifying circuit 2 for rectifying a three-phase commercial power source 1 to obtain a DC voltage, and a smoothing capacitor 3 for smoothing the DC voltage. , First switching elements 4a and 4d and second switching elements 4b and 4c that convert a DC voltage into a high-frequency AC pulse voltage and output positive and negative voltages, and an AC pulse voltage suitable for a high-frequency AC pulse voltage as a load And the output voltage V by rectifying the output of the transformer 6
In the DC arc welding power supply device including the second rectifier circuit 7 for supplying 0 to the welding load PA, magnetic flux detection for generating a winding output voltage value V10 proportional to the rate of change of the magnetic flux of the iron core of the transformer 6. Winding 6c, an integrating circuit 18 that integrates the winding output voltage value V10 and outputs an integrated signal V18, an output current detection circuit 24 that detects an output current and outputs an output current detection signal V24, and an output current The output current setting circuit 13 that outputs the output current setting signal V13 corresponding to the value, and the output current detection signal V24 and the output current setting signal V13 are input to output the output current detection signal V13 in order to make the output current constant.
24 and the output current setting signal V13, an output current compensation circuit 23 that outputs an output current compensation signal V23 that has been subjected to at least one of proportional, integral and differential operations, an integral signal V18 and an output current compensation signal. An output compensation signal correction circuit for inputting V23 and outputting an addition output compensation signal V26a obtained by adding the integration signal V18 to the output current compensation signal V23 and a subtraction output compensation signal V26b obtained by subtracting the integration signal V18 from the output current compensation signal V23. 26, a modulation reference signal oscillation circuit 19 for outputting a modulation reference signal V19 having a constant frequency and a constant amplitude, a modulation reference signal V19 and an addition output compensation signal V2.
6a and the subtraction output compensation signal V26b are input, and the addition pulse width modulation signal V21b and the subtraction pulse width modulation signal V21 are input.
The pulse width modulation circuit 21 that outputs a and the modulation reference signal V19, the addition pulse width modulation signal V21b, and the subtraction pulse width modulation signal V21a are input to the first synchronization signal V25.
a and the second synchronizing signal V25b are output in synchronization with the oscillation cycle of the modulation reference signal oscillating circuit 19, and when the first synchronizing signal V25a is input, the first switching elements 4a and 4d are connected to the bases. Signals V16a and V16d
Is output and the second synchronizing signal is input, the base signals V16b and V16 are supplied to the second switching elements 4b and 4c.
It is a power supply device for DC arc welding that includes a base circuit 16 that outputs c.

[0050]

FIG. 5 is a circuit diagram of a DC arc welding power source device according to a first embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 1 are the same as those in the description of FIG. In FIG. 5, the switching elements 4 a to 4 d are turned on, a voltage is applied to the primary winding 6 a of the transformer 6, and a magnetic flux is generated in the iron core of the transformer 6. 6
c is a magnetic flux detecting winding wound around the iron core of the transformer 6, and a voltage proportional to the rate of change of the magnetic flux of the iron core is generated. 1
Reference numeral 8 denotes an integrating circuit, which outputs an integrated signal V18 obtained by integrating the winding output voltage value V10 of the magnetic flux detecting winding 6c. The integrated signal V18 increases in the positive direction during the ON time of the first switching elements 4a and 4d, and increases in the negative direction during the ON time of the second switching elements 4b and 4c.

FIG. 6 is a diagram showing an embodiment of the integrating circuit 18. In the figure, 41 and 42 are operational amplifiers, 43 to 45 are resistors, 46 is a capacitor, and E is ground.

In FIG. 5, reference numeral 20 denotes a modulation signal correction circuit which inputs the integration signal V18 and the modulation reference signal V19 and outputs the subtraction modulation reference signal V20a and the addition modulation reference signal V20b. The subtraction modulation reference signal V20a is a value obtained by subtracting the integration signal V18 from the modulation reference signal V19, and the addition modulation reference signal V20b is the modulation reference signal V19.
Is a value obtained by adding the integrated signal V18. FIG. 7 is a diagram showing an embodiment of the modulation signal correction circuit 20. In the figure, 51 to 54 are operational amplifiers, 55 to 64 are resistors, and E is an earth.

In FIG. 5, the pulse width modulation circuit 21 is
The output current compensation signal V23 and the subtraction modulation reference signal V20a and the addition modulation reference signal V20b are input, and the subtraction pulse width modulation signal V21a and the addition pulse width modulation signal V21b are input.
Is output. FIG. 8 is a diagram showing an embodiment of the pulse width modulation circuit 21. In the figure, 71 and 72 are comparators. For example, in the comparator 71, the addition modulation reference signal V20b and the output current compensation signal V23 are input, and the addition modulation reference signal V20b is output from the output current compensation signal V23. When is also larger, the added pulse width modulation signal V21b becomes H level. On the contrary, when the addition modulation reference signal V20b is smaller than the output current compensation signal V23, the addition pulse width modulation signal V21b becomes L level.

In FIG. 5, the synchronizing circuit 25 includes a subtraction pulse width modulation signal V21a and an addition pulse width modulation signal V21.
b is input, and the first synchronization signal V25a and the second synchronization signal V25b are output. The base circuit 16 receives the first synchronization signal V25a from the switching element 4a.
Output the base signal V16a of the switching element 4d and the base signal V16d of the switching element 4d and input the second synchronization signal V25b.
b and the base signal V16c of the switching element 4c are output, the first switching elements 4a and 4d and the second switching element are synchronized with the oscillation frequency of the modulation reference signal oscillating circuit 19 and an appropriate pause time is provided. 4b and 4
Alternately turns on and off c.

FIG. 9 is a diagram showing an embodiment of the base circuit 16. In the figure, 16a to 16d are base circuits of the switching elements 4a to 4d, respectively.
An embodiment of the base circuits 16a to 16d is shown in FIG.
In the figure, 81 and 82 are DC power supplies, 83 and 84 are switching elements such as transistors, 85 is a resistor, and E is ground.

O of the first switching elements 4a and 4d
The integrated value of the voltage generated in the magnetic flux detection winding 6c during N hours is larger than the integrated value of the voltage generated in the magnetic flux detection winding 6c during the ON time of the second switching elements 4b and 4c. At times, the ON time of the second switching elements 4b and 4c is lengthened, and at the same time, the ON time of the first switching elements 4a and 4d is controlled to be shortened. On the contrary, the first switching elements 4a and 4d are turned on.
When the integrated value of the voltage generated in the magnetic flux detection winding 6c during the time becomes smaller than the integrated value of the voltage generated in the magnetic flux detection winding 6c during the ON time of the second switching elements 4b and 4c. , So that the ON times of the first switching elements 4a and 4d are lengthened and at the same time the ON times of the second switching elements 4b and 4c are shortened.

FIG. 11 is a diagram showing the waveform of the output signal of each part of the circuit diagram shown in FIG. In FIG. 11, (A)
Shows a waveform of the output V19 of the modulation reference signal transmission circuit 19, which is a sawtooth wave having a constant frequency and a constant amplitude. (B)
Shows the waveform of the output V23 of the output current compensation circuit 23,
(C) shows the waveform of the output V18 of the integrating circuit 18,
(D) shows the waveform of the output V20a of the modulation signal correction circuit 20, and (E) shows the output V20 of the modulation signal correction circuit 20.
3B shows the waveform of b, FIG. 6F shows the waveform of the output V21a of the pulse width modulation circuit 21, FIG. 9G shows the waveform of the output V21b of the pulse width modulation circuit 21, and FIG. Shows the waveform of the output V25a, and (I) shows the waveform of the output V25b of the synchronizing circuit 25.

At time t = t0, the switching element 4a is activated by the operation of a welding start switch (not shown).
The switching operation of 4d to 4d is started. Welding load P
Even when the output current compensation signal V23 changes as shown in FIG. 11B due to a change in A or a rapid change in the output current setting signal V13, unlike the related art 1 shown in FIG. The modulation reference signal V19 shown in FIG. 11A is proportional to the magnetic flux of the transformer 6, and the integrated signal V18 shown in FIG.
The modulation signal correction circuit 20 which has input
Is corrected to the subtraction modulation reference signal V20a shown in FIG. 9 and the addition modulation reference signal V20b shown in FIG.

The subtraction modulation reference signal V20a and the addition modulation reference signal V20b are pulse-width modulated by the pulse width modulation circuit 21 to obtain the subtraction pulse width modulation signal V21a and the subtraction pulse width modulation signal V21a shown in FIG. The added pulse width modulation signal V21b shown is obtained. The subtraction pulse width modulation signal V21a and the addition pulse width modulation signal V21b are input to the synchronizing circuit 25 to turn ON or OFF the first switching elements 4a and 4d and the second switching elements 4b and 4c. H) the first synchronization signal V25a
Also, the first switching elements 4a and 4d and the second switching elements 4b and 4c are converted into the second synchronizing signal V25b shown in FIG.
Let it.

As described above, since the integrated signal V18 proportional to the magnetic flux of the transformer 6 is controlled so as not to increase in one direction, the magnetic flux of the transformer 6 does not increase in one direction. The magnetic flux density of the iron core 6 does not reach the saturation magnetic flux density. Therefore, the switching elements 4a to 4
It is possible to prevent d from being destroyed by the biased magnetism of the transformer 6.

FIG. 12 is a circuit diagram of a DC arc welding power source device according to a second embodiment of the present invention. In the figure, the same reference numerals as those in FIG. 5 are the same as those in FIG.
Differences will be described. The first embodiment shown in FIG. 5 shows the case where the DC arc welding power supply device has a constant current characteristic, whereas the second embodiment shown in FIG. 12 is a DC arc welding power supply device. The case of constant voltage characteristics is shown. In FIG. 12, reference numeral 32 is an output voltage detection circuit for detecting an output voltage, which outputs an output voltage detection signal V32. An output voltage setting circuit 34 outputs the output voltage setting signal V34, and the voltage value of the welding load PA is determined by the value of the output voltage setting signal V34. An output voltage compensation circuit 33 receives the output voltage detection signal V32 and the output voltage setting signal V34 and outputs the output voltage compensation signal V33 for keeping the output voltage constant. The output voltage compensation signal V33 is input to the pulse width modulation circuit 21.
The description of the other circuits is the same as the description of FIG.

FIG. 13 is a circuit diagram of a DC arc welding power source device according to a third embodiment of the present invention, FIG. 14 is a diagram showing an embodiment of an output compensation signal correction circuit 26, and FIG.
FIG. 14 is a diagram showing an embodiment of the pulse width modulation circuit 21 shown in FIG. 13. 13 to 15, the same reference numerals as those in FIGS. 5, 7 and 8 are the same as those in FIGS. 5, 7 and 8, and therefore will be omitted, and the different points will be described. 13 and 14, reference numeral 26 denotes an output compensation signal correction circuit, which inputs the integration signal V18 and the output current compensation signal V23 and outputs an addition output compensation signal V26a and a subtraction output compensation signal V26b. The addition output compensation signal V26a is
The subtraction output compensation signal V26b is a value obtained by adding the integration signal V18 to the output current compensation signal V23, and the subtraction output compensation signal V26b is a value obtained by subtracting the integration signal V18 from the output current compensation signal V23.

13 and 15, the pulse width modulation circuit 21 includes a modulation reference signal V19 and an addition output compensation signal V
26a and the subtraction output compensation signal V26b are input, and the subtraction pulse width modulation signal V21a and the addition pulse width modulation signal V21b are output.

FIG. 16 is a diagram showing the waveform of the output signal of each part of the circuit diagram shown in FIG. In FIG. 16, (A)
Shows a waveform of the output V19 of the modulation reference signal transmission circuit 19, which is a sawtooth wave having a constant frequency and a constant amplitude. (B)
Shows the waveform of the output V23 of the output current compensation circuit 23,
(C) shows the waveform of the output V18 of the integrating circuit 18,
(D) shows the waveform of the output V26a of the output compensation signal correction circuit 26, (E) shows the waveform of the output V26b of the output compensation signal correction circuit 26, and (F) shows the output of the pulse width modulation circuit 21. Shows the waveform of V21a, (G) shows the waveform of the output V21b of the pulse width modulation circuit 21, and (H) shows
The waveform of the output V25a of the synchronization circuit 25 is shown, and (I) is
The waveform of the output V25b of the synchronizing circuit 25 is shown.

At time t = t0, the switching element 4a is activated by the operation of a welding start switch (not shown).
The switching operation of 4d to 4d is started. Welding load P
Even when the output current compensation signal V23 changes as shown in FIG. 16B due to a change in A or a rapid change in the output current setting signal V13, etc., the figure is proportional to the magnetic flux of the transformer 6 ( The output compensation signal correction circuit 26 to which the integrated signal V18 shown in C) is input is corrected to the addition output compensation signal V26a shown in FIG. 7D and the subtraction output compensation signal V26b shown in FIG.

The addition output compensation signal V26a and the subtraction output compensation signal V26b are pulse-width modulated by the pulse width modulation circuit 21, and the subtraction pulse width modulation signal V21a and the subtraction pulse width modulation signal V21a shown in FIG. The added pulse width modulation signal V21b shown is obtained. The subtraction pulse width modulation signal V21a and the addition pulse width modulation signal V21b are input to the synchronizing circuit 25 to turn ON or OFF the first switching elements 4a and 4d and the second switching elements 4b and 4c. H) the first synchronization signal V25a
Also, the first switching elements 4a and 4d and the second switching elements 4b and 4c are converted into the second synchronizing signal V25b shown in FIG.
Let it.

As described above, since the integrated signal V18 proportional to the magnetic flux of the transformer 6 is controlled so as not to increase in one direction, the magnetic flux of the transformer 6 does not increase in one direction. The magnetic flux density of the iron core 6 does not reach the saturation magnetic flux density. Therefore, the switching elements 4a to 4
It is possible to prevent d from being destroyed by the biased magnetism of the transformer 6.

FIG. 17 is a circuit diagram of a DC arc welding power source device according to a fourth embodiment of the present invention. 13, the same symbols as those in FIG. 13 are the same as those in the description of FIG. The third embodiment shown in FIG. 13 shows the case where the DC arc welding power supply device has a constant current characteristic, whereas the fourth embodiment shown in FIG. 17 is a DC arc welding.
This shows the case where the welding power supply device has a constant voltage characteristic. In FIG. 17, reference numeral 32 is an output voltage detection circuit for detecting an output voltage, which outputs an output voltage detection signal V32.
Reference numeral 34 denotes an output voltage setting circuit, which is an output voltage setting signal V
34, and the voltage value of the welding load PA is determined by the value of the output voltage setting signal V34. An output voltage compensation circuit 33 receives the output voltage detection signal V32 and the output voltage setting signal V34 and outputs the output voltage compensation signal V33 for keeping the output voltage constant. The output voltage compensation signal V33 is input to the output compensation signal correction circuit 26. The description of the other circuits is the same as the description of FIG. 13.

In the first embodiment shown in FIG. 5, the second embodiment shown in FIG. 12, the third embodiment shown in FIG. 13 and the fourth embodiment shown in FIG. 17, the switching element is a full bridge type. However, the present invention can also be applied to the case of arranging in a half bridge type.

[0090]

As described above, the DC arc welding power supply device according to the present invention has a winding which is proportional to the rate of change of the magnetic flux of the iron core generated in the magnetic flux detecting winding wound around the iron core of the transformer. The integrated signal obtained by integrating the line output voltage value by the integrator circuit is input to the modulation signal correction circuit, and the integrated signal is added to the modulated reference signal output from the modulation reference signal oscillator circuit. The first switching element and the second switching element are synchronized with the oscillation frequency of the modulation reference signal oscillating circuit by providing an appropriate pause time by a circuit configuration in which the subtracted subtraction modulation reference signal is input to the pulse width modulation circuit. By alternately turning on and off the switching element of No. 1, there is no influence of fluctuations in welding load, etc., and the integral signal proportional to the magnetic flux of the transformer does not increase in one direction. Switching element can be prevented from being destroyed by the magnetic deflection of the transformer.

Furthermore, since it is not necessary to use a large-sized capacitor for preventing demagnetization, the DC arc welding power supply device can be constructed in a small size and at a low price regardless of the output capacity of the DC arc welding power supply device. .

As described above, the DC arc welding power source apparatus according to the present invention has a winding output proportional to the rate of change of the magnetic flux of the iron core generated in the magnetic flux detecting winding wound around the iron core of the transformer. The integrated signal obtained by integrating the voltage value by the integrator circuit is input to the output compensation signal correction circuit, and the integrated signal is added from the added output compensation signal and the output current compensation signal obtained by adding the integrated signal to the output current compensation signal output from the output current compensation circuit. The first switching element and the second switching element are provided in synchronization with the oscillation frequency of the modulation reference signal oscillation circuit by providing a circuit configuration such as inputting the subtracted subtraction output compensation signal to the pulse width modulation circuit and providing an appropriate pause time. ON or OF alternately with the switching element of
By setting F, the integrated signal proportional to the magnetic flux of the transformer does not increase in one direction without being affected by welding load fluctuations, etc. Can be prevented.

Further, since it is not necessary to use a large-sized capacitor for preventing demagnetization, the DC arc welding power supply device can be constructed in a small size and at a low price regardless of the output capacity of the DC arc welding power supply device. .

[Brief description of drawings]

FIG. 1 is a circuit diagram of a DC arc welding power supply device according to Related Art 1.

FIG. 2 is a diagram showing waveforms of output signals of respective parts of the circuit diagram shown in FIG.

FIG. 3 is a circuit diagram of a DC arc welding power supply device according to Related Art 2.

FIG. 4 is a circuit diagram of a power supply device for DC arc welding of Prior Art 3 disclosed in Japanese Patent Publication No. 3-43938.

FIG. 5 is a circuit diagram of a DC arc welding power supply device according to a first embodiment of the present invention.

FIG. 6 is a diagram showing an embodiment of an integrating circuit 18;

FIG. 7 is a diagram showing an embodiment of a modulation signal correction circuit 20.

FIG. 8 is a diagram showing an embodiment of a pulse width modulation circuit 21.

FIG. 9 is a diagram showing an example of a base circuit 16;

FIG. 10 is a diagram showing an embodiment of base circuits 16a to 16d.

11 is a diagram showing a waveform of an output signal of each part of the circuit diagram shown in FIG. 5;

FIG. 12 is a circuit diagram of a DC arc welding power source device according to a second embodiment of the present invention.

FIG. 13 is a circuit diagram of a DC arc welding power source device according to a third embodiment of the present invention.

FIG. 14 is a diagram showing an embodiment of an output compensation signal correction circuit 26.

15 is a pulse width modulation circuit 2 shown in FIG.
It is a figure which shows the Example of 1.

16 is a diagram showing waveforms of output signals of respective parts of the circuit diagram shown in FIG. 13.

FIG. 17 is a circuit diagram of a DC arc welding power source device according to a fourth embodiment of the present invention.

[Explanation of symbols]

 1 3-Phase Commercial Power Supply 2 First Rectifier Circuit 3 Smoothing Capacitor 4a (First) Switching Element 4b (Second) Switching Element 4c (Second) Switching Element 4d (First) Switching Element 5a For Feedback Diode 5b Feedback diode 5c Feedback diode 5d Feedback diode 6 Transformer 6a Primary winding 6b Secondary winding 6c Magnetic flux detection winding 7 Second rectifier circuit 8 Filter reactor 9 Electrode 10 Welding object 11 Leakage inductance 12 bias magnetic discriminating circuit 13 output current setting circuit 14 reference time correction circuit 15a first pulse width modulation circuit 15b second pulse width modulation circuit 16 base circuit 16a base circuit 16b base circuit 16c base circuit 16d base circuit 17 anti-bias magnetism Capacitor 18 Integrator circuit 19 Modulation reference signal oscillation 20 Modulation signal correction circuit 21 Pulse width modulation circuit 23 Output current compensation circuit 24 Output current detection circuit 25 Synchronization circuit 26 Output compensation signal correction circuit 30 Arc 31 Second current detection circuit 32 Output voltage detection circuit 33 Output voltage compensation circuit 34 Output Voltage setting circuit 41 operational amplifier 42 operational amplifier 43 resistance 44 resistance 45 resistance 46 capacitor 51 operational amplifier 52 operational amplifier 53 operational amplifier 54 operational amplifier 55 resistance 56 resistance 57 resistance 58 resistance 59 resistance 60 resistance 61 resistance 62 resistance 63 resistance 64 resistance 71 comparator 72 comparator 81 DC power supply 82 DC power supply 83 Switching element 84 Switching element 85 Resistance V0 Output voltage V10 Winding output voltage value V12 Demagnetization determination signal V13 Output current setting signal V14a Addition modulation reference signal V14b Arithmetic modulation reference signal V15a first pulse width modulation signal V15b second pulse width modulation signal V16a base signal V16b base signal V16c base signal V16d base signal V18 integration signal V19 modulation reference signal V20a subtraction modulation reference signal V20b addition modulation reference signal V21 Pulse width modulation signal V21a Subtraction pulse width modulation signal V21b Addition pulse width modulation signal V23 Output current compensation signal V24 Output current detection signal V25a First synchronization signal V25b Second synchronization signal V26a Addition output compensation signal V26b Subtraction output compensation signal V31 2 current detection signal V32 output voltage detection signal V33 output voltage compensation signal V34 output voltage setting signal Vc voltage across bias-preventing capacitor 17 PA welding load E ground

Claims (2)

[Claims] 1. A first rectifying circuit and a smoothing circuit for rectifying a three-phase commercial power source to obtain a DC voltage, and a first rectifying circuit for converting the DC voltage into a high-frequency AC pulse voltage and outputting each positive and negative voltage.
A switching element and a second switching element, a transformer for converting the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load, and a transformer for rectifying the output of the transformer and supplying the output voltage to a welding load. In a DC arc welding power supply device having a rectifier circuit, a magnetic flux detection winding that generates a winding output voltage value proportional to the rate of change of the magnetic flux of the iron core of the transformer, and the winding output voltage value An integrating circuit that integrates and outputs an integrated signal, an output current detection circuit that detects an output current and outputs an output current detection signal, an output current setting circuit that outputs an output current setting signal corresponding to an output current value, One of proportional, integral and derivative with respect to the difference between the output current detection signal and the output current setting signal for inputting the output current detection signal and the output current setting signal to make the output current constant An output current compensation circuit for outputting an output current compensation signal subjected to calculation of the above, the modulation reference signal oscillator for outputting a modulation reference signal of constant frequency and a constant amplitude,
Modulation signal correction for inputting the integration signal and the modulation reference signal and outputting an addition modulation reference signal obtained by adding the integration signal to the modulation reference signal and a subtraction modulation reference signal obtained by subtracting the integration signal from the modulation reference signal A circuit, a pulse width modulation circuit for inputting the output current compensation signal, the addition modulation reference signal and the subtraction modulation reference signal and outputting an addition pulse width modulation signal and a subtraction pulse width modulation signal, and the modulation reference signal And a synchronization circuit for inputting the addition pulse width modulation signal and the subtraction pulse width modulation signal and outputting a first synchronization signal and a second synchronization signal in synchronization with the oscillation cycle of the modulation reference signal oscillation circuit. A base signal is output to the first switching element when the first synchronization signal is input, and a base signal is output to the second switching element when the second synchronization signal is input. DC arc welding power supply apparatus comprising a base circuit for outputting a degree. 2. A first rectifying circuit and a smoothing circuit for rectifying a three-phase commercial power source to obtain a DC voltage, and a first rectifying circuit for converting the DC voltage into a high frequency AC pulse voltage and outputting each positive and negative voltage.
A switching element and a second switching element, a transformer for converting the high-frequency AC pulse voltage into an AC pulse voltage suitable for a load, and a transformer for rectifying the output of the transformer and supplying the output voltage to a welding load. In a DC arc welding power supply device having a rectifier circuit, a magnetic flux detection winding that generates a winding output voltage value proportional to the rate of change of the magnetic flux of the iron core of the transformer, and the winding output voltage value An integrating circuit that integrates and outputs an integrated signal, an output current detection circuit that detects an output current and outputs an output current detection signal, an output current setting circuit that outputs an output current setting signal corresponding to an output current value, One of proportional, integral and derivative with respect to the difference between the output current detection signal and the output current setting signal for inputting the output current detection signal and the output current setting signal to make the output current constant An output current compensation circuit that outputs an output current compensation signal that has been subjected to the above calculation, an addition output compensation signal that receives the integration signal and the output current compensation signal, and adds the integration signal to the output current compensation signal, An output compensation signal correction circuit that outputs a subtraction output compensation signal obtained by subtracting the integration signal from the output current compensation signal, a modulation reference signal oscillation circuit that outputs a modulation reference signal having a constant frequency and a constant amplitude, and the modulation reference signal. A pulse width modulation circuit which inputs the addition output compensation signal and the subtraction output compensation signal and outputs an addition pulse width modulation signal and a subtraction pulse width modulation signal, the modulation reference signal, the addition pulse width modulation signal and the A synchronization circuit for inputting the subtraction pulse width modulation signal and outputting a first synchronization signal and a second synchronization signal in synchronization with the oscillation cycle of the modulation reference signal oscillation circuit; A base circuit that outputs a base signal to the first switching element when the first synchronization signal is input and outputs a base signal to the second switching element when the second synchronization signal is input. Power supply for DC arc welding.