JPS6064767A - Power source device for arc welding machine - Google Patents

Abstract

PURPOSE:To provide a titled device which prevents malfunction of circuits and short circuit breakdown with a DC welding power source using an inverter by prohibiting outputting of the other phase for specified time and reoutputting of the own phase pulses for specified time as well after outputting of the own pulses of transistors. CONSTITUTION:The pulses made into clock pulses by an IC17 enter flip-flop circuits 20-23 via NAND circuits 18, 19. The blocks 20, 23 regulate reoutputting of the pulses for specified time (28mus) after outputting the pulses. The blocks 21, 22 regulate outputting of the other pulses for specified time (5mus) after outputting of the pulses. The respective tansistors of an inverter circuit are regulated by such regulation via AND circuits 24-27, by which the malfunction and the overcurrent breakdown owing to a short circuit are prevented.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a welding power supply device, and more specifically, it uses a frequency higher than the commercial power frequency to supply a welding load to the welding load via a transformer, rectifier, and reactor. The present invention relates to a power supply device for an arc welding machine that supplies direct current.

[Background of the invention]

FIG. 1 is an overall configuration diagram of a bath contact type power supply previously developed by the present applicant, and the circuit will first be explained. In the figure,
1 is a rectifier that rectifies a three-phase AC power supply to an AC full DC power supply, 2
is a smoothing capacitor, :ll;t) transistors T1 to T4
It is a switching circuit (inverter) configured as a bridge with a diode Dl-D<k connected between the collector and emitter.
3k By alternately turning on and off, DC current is output as AC power at a frequency much higher than the commercial power frequency. 4 is a transformer, into which the AC output of the switching circuit 3 is input; 5.6 is a rectifier that is inserted into the secondary side of the transformer 4 and converts it into DC current; 6 is a reactor, which supplies the smoothed DC current to the welding load 7; 8 is a shunt installed between the middle point of the tertiary winding of the transformer 4 and the load 7, which detects the welding current flowing to the load 7, and amplifies it with the error amplifier 9. and is connected to one terminal of the differential amplifier 10. This is a reference voltage generator for setting the 1lfl output. Its output is connected to the child terminal of the differential amplifier 10, and the difference signal from the current detection signal by the shunt 8 is amplified and inputted to the comparator 12 as an output control signal. It is. Reference numeral 13 denotes a sawtooth voltage generator, the output signal of which is input to one terminal of the comparator 12 and to the signal distribution circuit 14. The comparator 12 compares the sawtooth voltage with the output control signal of the differential amplifier 10, and if the output control signal is thicker, the transistors T1. T4 and T2 + Ts k
Generates a pulse signal that turns on.

That is, the signal distribution circuit 14 inputs the sawtooth wave signal from the voltage generator 13 and the output of the comparator 12, and uses a transistor drive circuit 15 that has a transistor with a high switching speed and a delay circuit function that can arbitrarily adjust the switching speed. , 16' are turned on alternately, and the respective transistors 'rt + 'r4 and T2 + T3t' are turned on alternately.
This is what is turned on.

According to the circuit configured in this way, the following problems remain. That is, in the output vl of the differential amplifier 10,
When an instantaneous noise Q as shown in FIG. 2 is added, the output v2 of the comparator 12 generates short pulses alternately over a short period of time. This is the output v3. of the transistor drive circuit 15, 1.6. By adjusting the timing of V4, for example, the output pulse causes other transistors T2 r Ts k to become conductive before the transistors T1+T4'1 are turned off, resulting in a short circuit of the power supply. In addition, if the noise pulse width is too short, it may occur as a pulse signal (even if it is 7, the final stage transistor may not be turned on, and although it will not cause a short circuit of the power supply, as shown in the V5 waveform in Figure 2) The excitation current flows through the transformer twice in succession with the same polarity as the output pulse.As a result, the transformer becomes saturated and an overcurrent flows through the switching transistor, causing element destruction.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of conventional residual techniques and to provide a highly reliable welding power source that does not operate due to noise pulses.

[Summary of the invention]

The features of the present invention include a first comparison circuit that fully compares the welding load detection value and a reference voltage for output setting, and a first comparison circuit that fully compares the output of the first comparison circuit with the sawtooth voltage setting circuit output, and outputs an output control signal. A second comparator circuit that generates a signal whose width is controlled accordingly, and a pulse distribution circuit that receives the output of the second comparator circuit and outputs all the pulse signals that drive all the switching circuits for creating high-frequency alternating current. At the same time, the switching circuits of other phases are not turned on for a predetermined time after the pulse width-controlled pulse of the own phase is output, and the switching circuits of the own phase are all turned on for a predetermined time after the pulse of the own phase is output. Equipped with an interlock circuit to prevent it from turning on.
The point is that the switching circuit is not operated by pulses due to noise signals and the like.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described in detail with reference to FIGS. 3 and 4.

FIG. 3 is a diagram in which a pulse discrimination control circuit, that is, an interlock circuit that interlocks a pulse width-controlled signal, is provided as a measure to prevent pulse width.

In the figure, 17 indicates all ICs, which are for outputting clock pulses for forming all interlock circuits. 18
, 19 is a NAND circuit, 20.2], 22, 23U flip-flop circuit;
23 is the off time of the output pulse, and the flip-flop 2
], 22 are for setting and outputting the on-time of the output pulse. 241-j: An AND circuit that takes the output logical product of the NAND AND circuit 1 and the flip-flop circuit side; 5 is an AND circuit that takes the output logical product of the NAND circuit 1 and the flip-flop circuit B; 26 is the AND circuit that takes the logical product of the output of the NAND circuit 1 and the flip-flop circuit B; AND circuit that takes logical product, 27 is A
This is an AND circuit that takes the logical product of the outputs of the ND circuit 5 and the 7-rigged flop circuit 21, and the output of these AND circuits is output as a pulse that is not affected by noise or pulses.

The input and output pulse waveforms in the circuit of FIG. 3 are as shown in FIG. 4, and will be explained together with the same time chart.

Normally, the clock/4' pulse (a) and (fl) are alternately output by the output of the IC17, and the AND circuit 2
Normal pulses are obtained from the output terminals 6 and 27, which activates a switching circuit for creating high frequency alternating current at temperatures not shown in the figure. The operating state is shown by the e-res waveform (al), (up to the middle of fl, the current value is output/4'rus (if noise suddenly occurs in fl, after that)
The positive and negative pulse waveforms tend to reverse. However, an interlock is applied to the signal whose noise or response width has been controlled at the stage when the noise or response occurs. In other words, the first time (5 μS) after the self-phase pulse turns off.
is locked so that the switching circuits of other phases are not turned on.

Then, the self-phase pulse is controlled to be on, and an interlock is applied to prevent the self-phase switching circuit from turning on from the 20th time (28 ps). This eliminates abnormal reversals of pulses caused by noise noise, and even though there is a slight time difference, normal polarity discrimination is performed from the time the noise pulse is generated, and the transistor (or FET) that creates high-frequency alternating current. Control switching. In other words, / caused by Soi 46s etc.
It no longer outputs iQ pulses of the same polarity continuously due to the influence of f pulses, resulting in short circuits in the power supply, which was a problem with conventional circuits.

It can solve problems such as transformer saturation.

〔Effect of the invention〕

As is clear from the above embodiments, according to the present invention, i
Since a circuit is provided to interlock the + pulse width controlled signal to prevent continuous output of pulses of the same polarity, problems such as switching circuit malfunction, power supply short circuits, and transformer saturation can be solved.

[Brief explanation of the drawing]

Fig. 1 is an overall configuration diagram of an arc welding power supply device previously developed by the applicant, Fig. 2 is a time chart for explaining the operation of the device, and Fig. 3 is an embodiment of the present invention. FIG. 4 is a diagram showing the pulse discrimination control circuit section of the arc welding power supply device, and FIG. 4 is a diagram explaining the circuit operation.
D circuit n...Flip-flop circuit, 24-27...
・AND circuit. Representative Patent Attorney Tadashi Akimoto Figure 1

Claims (1)

[Claims] A power supply device for a welding machine that converts the rectifier circuit output into an AC current with a higher frequency than the commercial AC power frequency and uses it as a DC load power source via a transformer and rectifier.・Reference voltage for welding load detection value and output setting. a first comparator circuit that compares the output of the first comparator circuit with the output of the sawtooth voltage setting circuit, and a second comparator circuit that generates a signal whose pulse width is controlled in accordance with an output control signal; a pulse distribution circuit that obtains the output of the second comparison circuit and outputs a full pulse signal for driving the switching circuit for creating the high-frequency alternating current, and outputs the pulse width-controlled self-phase pulse. It is equipped with an interlock circuit that locks the switching circuit of the other phase so that it does not turn on for a predetermined time after the /4' pulse of the own phase is output, and locks the switching circuit of the own phase so that it does not turn on for a predetermined time after the /4' pulse of the own phase is output. A power supply device for an arc welding machine with f:%.