JPH0149592B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for controlling a pulse arc welding power source that performs welding while feeding a consumable electrode.

[Technical Background of the Invention] Generally, the pulsed arc welding method, in which a consumable electrode (hereinafter referred to as a wire) is fed to a welding area for welding, makes the droplets at the tip of the molten wire into fine particles for smooth transition. (hereinafter referred to as spray transfer),
And by keeping the arc length constant,
The purpose is to generate a stable arc to obtain uniform welding results and to obtain a welded product with less spatter. This wire is supplied with a base current that is low enough to prevent spray transfer, that is, below a critical current value, and a pulsed current that periodically becomes a high current that exceeds the critical current value, thereby causing spray transfer.

Prior to explaining the present invention, the transfer of molten metal from the tip of a wire in arc welding using a consumable electrode will be explained.

Generally, in arc welding using a consumable electrode, when the welding current is small, the wire tip melted by arc heat becomes a molten ball at the wire tip supported by surface tension while its volume is small. It's getting old and staying. As the amount increases over time, it will gradually sag due to gravity, eventually overcoming surface tension and falling. The droplets that fall at this time are large, several times the diameter of the wire, and their frequency is low.

On the other hand, if the welding current is gradually increased, the number of grains will also gradually increase in proportion to this, but when a certain current value is exceeded, there is a current where the number of grains increases dramatically, and in this case, the number of grains increases dramatically at the same time. The volume per grain decreases dramatically. In addition, the migration speed of the particles at this time is much faster than the speed of natural fall due to gravity.

The reason for this is that, in addition to gravity, the molten ball at the tip of the wire is subjected to a force in the direction of squeezing the molten ball due to the welding current, and an electromagnetic focusing force (generally called the pinch effect) due to the welding current. It is thought that when the welding current becomes large, this becomes sufficiently stronger than gravity, causing the molten spheres to separate from the tip of the wire when they are relatively small.

The welding current value at which this transfer form suddenly changes is called the critical current, the droplet transfer form at a current value lower than the critical current is called globular transfer, and the transfer form at a current value higher than the critical current is called spray transfer. There is. This critical current varies depending on the diameter of the wire used, the material, the surface treatment state, the protrusion length of the welding torch from the power supply tip, the composition of the shielding gas used, etc., and usually depends on each case. It is determined by experiment.

Next, we will examine the effect of pulsed current on welding results in pulsed arc welding. In pulsed arc welding, the pulse current elements for maintaining smooth spray transition include the peak value Ip of the pulse current and the pulse duration time (hereinafter referred to as pulse width) tp. Among these, the pulse current peak value Ip is the most important factor that has the effect of detaching the droplet from the tip of the molten wire by a pinch force proportional to ^Ip2 , and the pulse current value Ip is larger than the critical current. If the pulse current value Ip becomes small, the fine droplets will migrate, and conversely, if the pulse current value Ip becomes small, the large droplets will migrate irregularly. Therefore, unless the pulse current value Ip is maintained at a constant value higher than this critical current value, smooth spray transfer cannot be performed. Furthermore, as a condition for detaching the droplet from the tip of the molten wire, a predetermined pulse width tp is also required, but since detachment of the droplet is due to pinch force, the pulse width tp is determined by the above-mentioned pulse current value Ip. This is an important requirement that affects droplet detachment in relation to By selecting appropriate values for these, the cycle of the pulse current and the cycle of droplet transfer can be matched, and smooth spray transfer can be achieved.

[Prior Art and Problems to be Solved by the Invention] In arc welding using pulsed current as described above, the peak value Ip of the pulsed current and the pulse value tp, which is its duration, are important requirements. Among these, setting the pulse peak value Ip to a predetermined value is
This can be achieved relatively easily by using methods such as using a pulse current power supply with approximately constant current characteristics, or using feedback control to suppress the pulse peak value to a constant current when extracting pulse current from a DC power supply with constant voltage characteristics. . However, the pulse width tp is usually determined by controlling the time from its rise to its fall.

However, the actual pulse current waveform is strongly influenced by the power supply voltage, the impedance of the output circuit cable of the welding machine, the arc length, the wire protrusion length, etc. The effective width changes, and stable spray transfer in which pulse current and droplet transfer are synchronized cannot be expected.

The cause of this will be explained using a diagram. FIG. 1 is a connection diagram showing a conventional example of a control device for this type of pulse arc welding power source. In the same figure, 1 is a DC power supply for supplying pulse current, and 2 is a DC power supply 1.
3 is a DC reactor, and 4 is a DC power supply for supplying a base current sufficient to maintain an arc to the welding current. Reference numeral 5 denotes a pulse waveform control circuit that outputs a signal for determining the conduction amount and conduction period of the current control element 2, and a pulse oscillation circuit that generates pulses with a constant amplitude and frequency is usually used. Reference numeral 6 denotes a drive circuit for converting the output of the pulse waveform control circuit 5 into a signal suitable for controlling the current control element 2. Also 31,
32 is an output terminal, and 10 is a flywheel diode.

In the device shown in FIG. 1, the current control element 2 becomes conductive in response to the output signal from the pulse waveform control circuit 5. As a result, the consumable electrode 7 and the workpiece 8 are connected between the output terminals 31 and 32 with an output cable.
Then, a current in which a pulse current corresponding to the output signal from the pulse waveform control circuit 5 is superimposed on the output current of the base current DC power source 4 is output, and a pulse welding arc 9 is generated.

In this way, in the conventional device, the amount of conduction of the current control element is controlled so that the pulse width is determined by the pulse waveform control circuit 5. will be examined in detail. Figure 2a shows the equivalent circuit on the load side on the right side from the output terminals 31 and 32 of the device in Figure 1, and r _l and Ll are the resistance of the output circuit from the output terminal to the arc generation point, which is the welding load, and The inductance component is shown, and Ea and r _a are the welding voltage of the arc load and the resistance at the protruding length portion of the consumable electrode wire beyond the power supply part. Also, reactor 3 is connected in series to the pulse current circuit.
The inductance of is Lo.

Consider a case where, in such a circuit configuration, a rectangular waveform drive signal having a width tp as shown in FIG. 2c is supplied from the pulse waveform control circuit 5 to the current control element 2. At this time, if the output voltage of the pulse DC power supply 1 is _E1 , the resistance and inductance of the output circuit are R= _r1 + _ra , and L= _L1 +Lo, then the pulse output current
As shown by A in Figure 2b, Ip increases toward the steady voltage (E ₁ -E _a )/R with a rising time constant L/R. rises along a curve. This current stops increasing at time _t1 when it reaches the peak current Ip determined by the peak value of the output signal of the pulse waveform control circuit 5, and thereafter is maintained at approximately one constant value. When the output of the pulse waveform control circuit 5 becomes zero at time t ₃ after time tp, the current control element 2 is cut off, and the electromagnetic energy (1/2・LoIp ² ) stored in the reactor 3 during this pulse period tp is is emitted through the flywheel diode 10.

Here, consider a case where the power supply voltage fluctuates and the output voltage of the DC power supply 1 drops from _E1 to _E2 . At this time, as shown by B in Figure 2b, the pulse current rises with the same time constant L/R toward the steady current (E ₂ - E _a )/R, which is lower than the previous value, so its rising speed is delayed, and the time t ₂ at which the set current Ip is reached is later than t ₁ in the case of A where the power supply voltage is high.

On the other hand, the output of the pulse waveform control circuit 5 to the current control element 2 becomes zero at time _t3 regardless of fluctuations in the power supply current, and the current decreasing speed is 1/2 of the electromagnetic energy stored in the reactor 3.LoIp ²
Since it is the same value, it will not change. As a result, the time during which the set current is held at the value of Ip becomes shorter even though the command signal is the same, and the true pulse time width that is effective for spray transfer becomes narrower and becomes insufficient. As can be seen from the above equation, the rate of rise of the pulse current is determined not only by the power supply voltage but also by r _l and Ll, which are related to the cable length, the welding voltage Ea, which is determined by the arc length, and r, which is related to the wire protrusion length. It is similarly affected by each component of _a . Therefore, the pulse current waveform changes its appearance from moment to moment, and no matter how accurately the waveform of the command signal from the pulse waveform control circuit 5 is constant, it is only the bottom of the output pulse current waveform, that is, the rising edge of the pulse current. Since the pulse current is only controlled from the time to the moment of fall, the width of the pulse current above the critical current that is effective for spray transfer cannot be regulated, and the droplets of the consumable electrode synchronize with the period of the pulse current. Welding with smooth spray transfer cannot be performed.

[Means for Solving the Problems] The present invention has been made to improve the above-mentioned conventional control method, and the present invention is made by changing the width of the pulse current to a constant current other than zero, especially when droplets are transferred to a spray. By controlling the period during which the current exceeds the critical current to a predetermined value, pulsed arc welding is realized in which spray transfer is always stable regardless of fluctuations in external conditions.

[Embodiment] FIG. 3 is a connection diagram showing an example of a device implementing the present invention. In the figure, parts having the same functions as those of the apparatus shown in FIG. 1 are given the same reference numerals. 11 is a current detector for detecting the output current i, 12 is a reference current setting device for determining the pulse time, and the output Ix is determined experimentally depending on the material and diameter of the wire used or the composition of the shielding glass. Set approximately equal to the critical current for spray migration required. 13 is a comparator that compares the output i of the current detector 11 and the output Ix of the reference current setter 12 and generates an output signal when i≧Ix, and 14 is an oscillator for determining the frequency of the pulse current. The pulse frequency control circuit 15 is a time limit circuit that starts a time limit based on the output of the comparator 13 and ends the time limit after a time determined by a time limit setter 16. Reference numeral 17 denotes a pulse signal generation circuit that outputs a signal that continues from the time when the output signal of the pulse frequency control circuit 14 is received until the time limit of the time limit circuit 15 ends. A flip-flop circuit is used which is reset by the expiration of the timer of circuit 15. The pulse DC power supply 1' is a power supply whose output current is always set to a constant pulse peak value by a pulse peak current setting device 18, and the pulse DC power supply 1' is connected to the current control element 2'. A switching element is used to open and close the output. The operation of the apparatus shown in FIG. 3 will be explained with reference to the explanatory diagram shown in FIG. When the pulse frequency control circuit 14 outputs the signal p at a predetermined period as shown in FIG. This output tp
As a result, the drive circuit 6 makes the switching element 2' conductive, and the output of the pulsed DC power source is supplied to the welding part. This pulse current is detected by a current detector 11 and compared with a set value Ix of a reference current setter 12. The pulse current that has risen from time 0 increases according to the time constant of its output circuit, and when i≧Ix, the comparator 13 outputs an output and causes the time limit circuit 15 to start the time limit. The time limit circuit 15 starts counting time from this time and ends the time limit after a predetermined time t _x determined by the time limit setter 16. The pulse signal generating circuit 17 stops its output when the time limit circuit 15 expires. As a result, switching element 2' is also cut off, and then pulse frequency control circuit 14
The cut-off state continues until the output from is supplied.

In the device shown in the figure, fluctuations in the power supply voltage, cable length, welding voltage, wire protrusion length, etc., cause fluctuations in the impedance of the output circuit.
Consider a case in which the rising speed of the pulse current decreases from that shown by the solid line in a of FIG. 4 to that shown by the broken line. First, if the pulse current that rises from time 0 has a fast rise speed as shown by the solid line, the current i is set at a relatively early time _t1 to the set value Ix of the reference current setting device 12.
reach. The time limit circuit 15 starts timing from this time _t1 , and the set time _tx is set as shown in FIG. 4c.
Since the time period ends at time _t3 after
continues for t _p1 from to t ₃ . At time _t3 , when the output signal of the pulse signal generation circuit 17 disappears, the switching element 2' is cut off, so that the output current i is generated by releasing the electromagnetic energy stored in the reactor 3 through the flywheel diode 10 at a certain time. Decrease by a constant.

On the other hand, when the rising speed is slow as shown by the broken line, the current i reaches the set value Ix at time _t2 later than in the case of the solid line, but the time limit circuit 15
As shown in FIG. 4e, the timer starts counting from time _t2 and completes the time limit at time _t4 after the set time _tx . As a result, the switching element 2' continues to conduct from time 0 to _t4 . Therefore, if the reference current Ix is set to a value approximately equal to the critical current that is effective for spray transfer of droplets, the pulse current will always have the time width necessary for stable spray transfer. . It is desirable to determine this reference current Ix within a range that is at least the critical current at which droplets transfer to the spray and does not exceed the peak value of the output current, but even if it is smaller than the critical current, if it is close to the critical current, then Similar effects can be expected.

In this way, the peak current Ip and pulse time width tp
Stable welding is possible by controlling the However, in arc welding, the arc length may change due to unevenness of the workpiece, fluctuations in the position of the welding torch, or slight discrepancies between the wire feeding speed and the amount of wire melting. On the other hand, if the peak current Ip and time width tp are controlled constant, the average value of the current used to heat and melt the wire will also be kept constant even when the arc length changes. There is no long-term self-control effect. As a result, once the arc length changes due to any of the causes mentioned above, it cannot be recovered. Therefore, for example, if there is a slight slowdown in the wire feeding speed relative to the wire melting speed, this will immediately grow and lead to wire burnback or protrusion.

In order to prevent this phenomenon, the welding voltage Ea should be detected as shown by the dashed line in Fig. 3.
This may be supplied to the pulse frequency control circuit 14, and the frequency of the generated command pulse may be controlled in accordance with Ea. That is, if the pulse frequency is increased while keeping the pulse time width tp constant, the average value of the welding current increases, and the amount of wire melting also increases accordingly. Therefore, when the arc length becomes shorter and the welding voltage becomes lower, if the pulse frequency is increased in inverse proportion to this, the average value of the pulse current will increase, which will increase the amount of wire melted and reduce the arc. Recovery based on length. Conversely, when the arc length becomes longer and the welding voltage becomes higher, if the frequency is reduced in inverse proportion to this, the amount of wire melting is reduced and the arc length is restored to its original value. Also, the average value of welding current is
As shown by the broken line in FIG. 3, the welding voltage is detected and used as a command signal for the time limit setting device 16 of the time limit circuit 15, and the pulse time width tp is changed in accordance with the welding voltage while keeping the pulse frequency constant. This method also allows automatic control of the arc length.

Further, the wire feeding speed is generally determined depending on the wire thickness and the welding current value used. Therefore, it is necessary to adjust the wire feeding speed and the average value of the pulse current in conjunction with each other. In this case, welding conditions can be uniformly adjusted by changing the pulse time width tp or the pulse frequency approximately in proportion to the wire feeding speed. At this time as well, self-control of the arc length due to power supply characteristics cannot be expected with respect to changes in arc length, so the welding voltage is detected and the pulse time width or pulse frequency is controlled in approximately inverse proportion to this. It becomes possible to implement automatic arc length control.

Figure 3 shows an example of a method in which a power source whose peak value is controlled to a constant value is used as a pulse supply DC power source, and the output of this DC power source is opened and closed by a switching element connected in series to the output circuit. However, the pulse supply DC power supply is not limited to this, and a DC power supply with substantially constant voltage characteristics may be used, and in this case, both the pulse time width and the peak value may be controlled by a current control element. FIG. 5 is a connection diagram showing an embodiment of a system in which both the pulse time width and the peak value are analog-controlled by a current control element. In this figure, parts having the same functions as those in FIGS. 1 and 3 are given the same reference numerals. Further, the current detector 11' is different from the case shown in FIG. 3 and is a current detector that detects only pulse current. 19 is the output i of the current detector 11' and the output Ip of the peak current setting device 18.
For example, a subtracter is used to obtain the difference (Ip-i) between both signal values. 2
0 is a second comparator that compares the output i of the current detector 11' and the output Ix of the reference current setter 12 and generates an output when i≧Ix, and 21 is the first and second comparator.
This is a signal synthesis circuit which receives as input the outputs of the comparators 19 and 20 and the output of the pulse frequency control circuit 14.
If a subtracter is used to obtain
A pulse command signal that starts from the rising edge of the output signal of No. 4 and ends after a predetermined time after the output signal of the second comparator is generated is outputted and supplied to the drive circuit 6 to control the conduction of the current control element 2. It is something to do. This signal synthesis circuit may be of any type as long as it has the above-mentioned functions, and an example thereof is shown in FIG. FIG. 6 shows the signal synthesis circuit 21 of the device shown in FIG.
FIG. 2 is a connection diagram showing the input/output section of the section. In the figure, reference numeral 15' denotes a timer circuit 1 which starts counting the timer upon receiving the output of the second comparator 20 and ends after the timer set by the timer setter 16'. This corresponds to the time limit circuit 15 in the example. 22 is a flip-flop circuit which is set by the rise of the output of the pulse frequency control circuit 14 and reset by the end of the time limit of the time limit circuit 15';
This is an analog switch circuit that allows the output to pass through while it is at a high level and transmits it to the drive circuit 6.

FIG. 7 is a connection diagram showing an embodiment of a signal synthesis circuit configured to perform control using a switching method, in which the first comparator 19' compares the peak current setting value Ip and the detected current value i. An example of using a circuit that generates a signal that makes the current control element conductive only when I<Ip is shown below.

In the figure, reference numeral 24 denotes an AND circuit that receives the outputs of the first comparator 19' and the flip-flop circuit 22.
This circuit outputs a signal that makes the switching element 2 conductive only while the flip-flop circuit 22 is generating an output and the pulse current is smaller than the reference current Ip.

When using the example circuit of FIG. 7 as a signal synthesis circuit, the current control element 2 is used not as an analog circuit but as a switching element.
Not only is more stable control possible, but the capacitance of the element can be reduced because only the loss during switching needs to be borne.

In addition, in the signal synthesis circuit shown in FIG. It may also be input together with the signal to perform chopper control on the output signal.

In the embodiment shown in Fig. 5, as in Fig. 3, the pulse period is measured from the time when the reference current Ix is exceeded, regardless of the rise speed of the pulse current. Since the width of the pulse current after it becomes effective for transition is always constant, stable welding can always be performed.
In the embodiment shown in FIG. 5, either a signal corresponding to the welding voltage is obtained and used as the frequency command for the pulse frequency control circuit 14, or it is supplied to the time limit setting circuit 16' to set the time limit of the time limit circuit 15'. By setting a command, it is possible to automatically recover from fluctuations in welding voltage due to fluctuations in arc length. Further, by determining the pulse frequency or pulse time width in accordance with the wire feeding speed, it becomes possible to adjust the wire feeding amount and the average value of the pulse current in an integrated manner.

In the embodiments of FIGS. 3 and 5, the pulse signal generation circuit 17 and the signal synthesis circuit 21 are flip-flop circuits that are set by a signal from a pulse frequency control circuit and reset by the end of a time limit circuit, as explained in each case. In addition, if the width of the output pulse of the pulse frequency control circuit 14 is relatively wide and sufficiently covers the rise time of the pulse current as shown in FIG. is received by the OR circuit and the total output is d or f in Figure 4.
It is also possible to obtain a continuous signal like this.

Furthermore, in each embodiment, the drive circuit 6 is not particularly necessary if the output of the pulse signal generation circuit or signal synthesis circuit in the previous stage is sufficient. In addition, the current detector may be one that detects the entire output current including the base current, or one that detects only the pulse current. In each case, this base current is detected when setting the reference current Ix. Just consider it.

Further, when a small current signal for causing a base current to flow through the drive circuit 6 is superimposed on the output signals of the pulse signal generation circuit and the signal synthesis circuit, the DC power supply 4 for supplying the base current can be omitted. In this case, if the current detector 11 in FIG. 5 is used as a detector that detects the total output current including the base current, as in the example in FIG. It can be configured to control the

[Effects of the Invention] As described above, according to the present invention, the pulse time width, which is the most important requirement in pulsed arc welding, is controlled as the duration at a value that is effective for actual spray transfer of droplets. So,
Even if there are fluctuations in the power supply voltage, changes in the impedance of the output circuit due to replacement of the connected output cable, or changes in the arc voltage, the pulse time width can always be maintained at the required width, and the pulse current can be accurately synchronized. This allows the droplets to be transferred by spraying, resulting in extremely stable welding.

[Brief explanation of drawings]

Fig. 1 is a connection diagram showing a control method in conventional pulse arc welding, Figs. 2 a to c are explanatory diagrams for explaining the operation of the apparatus shown in Fig. 1, and Fig. 3 shows an embodiment of the present invention. Connection diagrams, FIGS. 4a to 4f are explanatory diagrams for explaining the operation of the embodiment of FIG. 3, FIG. 5 is a connection diagram showing another embodiment of the present invention, and FIGS. 6 and 7 are FIG. 6 is a connection diagram showing an example of the internal structure of the signal synthesis circuit in the embodiment of FIG. 5; 1...DC power supply, 2...Current control element, 2'...
...Switching element, 11...Current detector, 12
...Reference current setter, 13...Comparator, 14...
Pulse frequency control circuit, 15, 15'... Time limit circuit, 17... Pulse signal generation circuit, 18... Peak current setting device, 19, 19'... First comparator,
20... second comparator, 21... signal synthesis circuit,
22...flip-flop circuit, 23...analog switch, 24...AND circuit.

Claims (1)

[Scope of Claims] 1. In pulsed arc welding, which is performed while feeding a consumable electrode to a welding part at a predetermined speed, the peak value of the output current is maintained at a constant value, and the pulsed current is started to flow at a predetermined repetition frequency. and a pulsed arc that terminates the pulsed current period after a predetermined time elapses from the time when the instantaneous value of the output current exceeds a predetermined reference value to a value that is approximately equal to a critical current value that can cause the consumable electrode to spray transfer. How to control a welding power source. 2. In pulse arc welding, which is performed while feeding a consumable electrode to the welding part at a predetermined speed, a DC power source that outputs a DC current of a predetermined peak value, and switching that opens and closes the output of the DC power source to make it pulse-like. an element, a reference current setter set to a value Ix substantially equal to a critical current value that can cause spray transfer of the consumable electrode, a current detector that detects an output current i, and a current detector configured to cause a pulsed current to flow at a predetermined period. a pulse frequency control circuit for repetition, an output signal Ix of the reference current setter, and an output signal i of the current detector;
a comparator that generates an output when i≧Ix, a time limit circuit that starts timing based on the output signal of the comparator, and a time limit circuit that starts timing from the time when the output signal of the pulse frequency control circuit is received. A control device for a power source for pulsed arc welding, comprising a pulse signal generation circuit that outputs a signal that continues until the end of a time limit, and a drive circuit that makes the switching element conductive in accordance with the output signal of the pulse signal generation circuit. 3. The control device according to claim 2, wherein the pulse frequency control circuit is a circuit that generates a pulse with a frequency corresponding to a welding voltage. 4. The control device according to claim 2, wherein the pulse frequency control circuit is a circuit that generates pulses at a frequency corresponding to the feeding speed of the consumable electrode. 5. According to any one of claims 2 to 4, the time limit circuit is a circuit that starts a time limit based on the output signal of the comparator and ends the time limit after a time corresponding to the welding voltage. control device. 6. Any one of claims 2 to 4, wherein the time limit circuit is a circuit that starts a time limit based on the output signal of the comparator and ends the time limit after a time corresponding to the feeding rate of the consumable electrode. The control device according to one of the above. 7 In pulsed arc welding, which is performed while feeding a consumable electrode to the welding part at a predetermined speed, a DC power supply and
a current control element for controlling the output of the DC power supply in a pulsed manner, a peak current setting device for setting a peak value Ip of the output current, and a value Ix approximately equal to a critical current that can cause spray transfer of the consumable electrode a reference current setting device to be determined, a current detector for detecting the output current i, a pulse frequency control circuit for repeating the flow of the pulse current at a predetermined period, an output signal Ip of the peak current setting device and the current detection. a first comparator that compares the output signal i of the pulse current detector, and a first comparator that compares the output signal Ix of the reference current setter with the output signal i of the pulse current detector and generates an output when i≧Ix. 2 comparators and said first and second comparators;
a signal synthesis circuit that receives the output of the comparator and the output of the pulse frequency control circuit and outputs a signal for determining a pulse current value and a pulse time width; and a signal synthesis circuit that controls the current according to the output signal of the signal synthesis circuit. A control device for a power source for pulsed arc welding, comprising a drive circuit for making an element conductive. 8 The first comparator is a subtracter that obtains a difference signal (Ip-i) between the output signal Ip of the peak current setter and the output signal i of the current detector, and the signal synthesis circuit is a subtracter that obtains a difference signal (Ip-i) between the output signal Ip of the peak current setter and the output signal i of the current detector a time limit circuit that starts timing based on the output of the comparator; a pulse time control circuit that outputs a signal that continues from the time when the output signal of the pulse frequency control circuit is received until the end of the time limit of the time limit circuit; 8. The control device according to claim 7, further comprising an analog switch circuit that transmits the output of the first comparator to the drive circuit while the time control circuit is generating the output. 9 The first comparator is a comparator that compares the output Ip of the peak current setter and the output signal i of the current detector and generates a signal that makes the current control element conductive only when i<Ip. , the signal synthesizing circuit includes a timer circuit that starts timing based on the output of the second comparator, and a signal that continues from the time when the output signal of the pulse frequency control circuit is received until the end of the timer of the timer circuit. a pulse time control circuit to output, an output of the pulse time control circuit and the first pulse time control circuit;
8. The control device according to claim 7, comprising an AND circuit whose inputs are the output of the comparator and the output of the comparator. 10. The control device according to any one of claims 7 to 9, wherein the pulse frequency control circuit is a circuit that generates a pulse with a frequency corresponding to a welding voltage. 11. The control device according to any one of claims 7 to 9, wherein the pulse frequency control circuit is a circuit that generates pulses with a frequency corresponding to the feeding rate of the consumable electrode. 12. The signal synthesis circuit is a circuit that outputs a signal that rises due to the output of the pulse frequency control circuit and falls after a time corresponding to the welding voltage from the output signal of the second comparator as a pulse time width signal. The control device according to any one of items 7 to 11. 13. Claim 7, wherein the signal synthesis circuit is a circuit that outputs a signal that rises and falls after a time corresponding to the feeding rate of the consumable electrode as a pulse time width signal based on the output of the pulse frequency control circuit.
The control device according to any one of items 1 to 11.