JPH03216279A - Power unit - Google Patents

Abstract

PURPOSE:To supply a peak current higher than a constant current value by providing a low voltage detection circuit to detect a voltage drop in an arc weld zone, inputting a drop signal of the detected voltage to a control circuit and obtaining a pulse width control signal to carry the peak current to a closed circuit. CONSTITUTION:The closed circuit is constituted of circuits including a DC power source, a switching element, the arc weld zone, etc. The low voltage detection circuit 22 to detect the voltage drop in the arc weld zone 4 is provided and the drop signal of the detected voltage is inputted to the control circuit 8 to obtain the pulse width control signal to carry the peak current to the closed circuit. When a welding rod is brought into contact with objects to be welded, the voltage in the arc weld zone is diminished to zero and on-time of the switching element 2 is lengthened by the drop signal of the voltage inputted to the control circuit 8 from the low voltage detection circuit 22 and the peak current higher than the constant current value can be carried to the closed circuit. Consequently, the power unit suitable for arc welding can be obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION INDUSTRIAL APPLICATION The present invention relates to a power supply device, and more specifically, to a power supply device comprised of a flow circuit and used for arc welding.

Conventional arc welding involves bringing the welding metal connected to the output of a power supply into contact with the object to be welded, passing a constant current from the power supply, raising the temperature to the point where arc discharge occurs, and then welding using arc heat. Welding is performed by melting and adhering it to the object to be welded.

The power supply equipment used for such arc welding is as follows:
A device constructed from a Cheetsuba circuit as shown in FIG. 5 is known. That is, in FIG. 5, a switching element 2, a reactor 5, an arc welding section 4 to which a welding rod 4-1 and a welding object 4-2 are attached, and a shunt 5 are connected in series to a storage battery 1 as a DC power source. are connected to form a closed circuit. Note that the diode 6 is for Fufuihui-μ, and the storage battery 1 is equipped with a charger 10 as necessary.
is connected. The switching element 2 is controlled in pulse width by a drive circuit 7 to obtain an appropriate output voltage, and is controlled by a current shunt 5 to obtain an appropriate constant current output predetermined according to the thickness of the welding salve. The output power is inputted to the drive circuit 7K via the control circuit 8 and the pulse width is controlled.

Next, the operation of the control circuit 8 will be explained. The control circuit 8 consists of a pwx'R conversion section 11 and a control power supply section 12, and a power supply line 13.1 is connected from the control power supply section 12 to the PWM conversion section 11.
Control power is supplied via 4. This control power source receives the storage battery 1 as an input and is stabilized by the control power source section 12. The PWM converter 11 includes an amplifier 15 and resistors 16, 17, 18, 1 connected to the input side of the amplifier 15.
9, and the amplifier 15 includes a resistor 16 and a resistor 19.
The series connection point with the resistor 17, the resistor 18,
It is configured to amplify the change in potential at the point where the resistor 17 and the resistor 18 are connected in series in the series circuit of the shunt 5. The output of the amplification fi15 is input to the PWM circuit 20, and its power is input to the drive circuit 7K via the bus A/bass amplifier circuit 21. Note that the explanation regarding the control of the output voltage by this control circuit 8 is omitted because it has no relation to the present invention.

In the power supply device having such a configuration, as shown in Fig. 4, a constant current output of 10 is obtained at the same time as the voltage between the arc welding part is made zero at time t0, and the welding rod 4-1 is melted and the welding target is welded. Arc welding of object 4-2 is performed.

Problems to be Solved by the Invention In the conventional power supply device as described above, since the constant current output is constant, the temperature rises to a point where arc discharge occurs when the welding box 4-1 and the welding object 4-2 are brought into contact. It takes a long time to do this, and if the temperature rise is insufficient, the arc discharge is interrupted and reliable welding cannot be performed.

Means for Solving the Problem In order to solve the problem, the power supply device of the present invention includes a DC power supply, a switching element for switching the output of the DC power supply, a reactor, a welding pipe, and an object to be welded. A control circuit that forms a closed circuit with an arc welding part to which the is attached and a shunt, and that inputs the output of the shunt and creates a bus width control signal to make the current flowing in the closed circuit a constant current. and a drive circuit that converts the output of the control circuit into a drive signal for the switching element, and a low voltage detection circuit that detects a drop in voltage across the arc welding part, The present invention is characterized in that it has a function of inputting a voltage drop signal to the control circuit and obtaining a bus width control signal for causing a peak current to flow through the closed circuit.

Effect With the above configuration, when the welding rod and the object to be welded come into contact, the voltage across the arc welding part becomes zero,
The voltage drop signal input from the low voltage detection circuit to the control circuit lengthens the on time of the switching element, allowing a peak current larger than the constant current value to flow through the closed circuit.

When the temperature of the contact portion between the welding tip and the object to be welded increases due to this peak current, the resistance increases and the voltage increases, and the operation of the low voltage detection circuit is canceled and the peak current decreases. Therefore, it is possible to reach a temperature at which arc discharge occurs in a short period of time. JI1! It is possible to carry out welding.

EXAMPLE The following is an explanation using examples. FIG. 1 is a circuit diagram of a power supply device according to the present invention, in which parts having the same functions as those in FIG. 6 are given the same reference numerals. A feature of the present invention is that a low voltage detection circuit 22 is added to the apparatus shown in FIG. Resistor 24 for voltage division
．． 25, a reference voltage section consisting of a resistor 26 and a constant voltage diode 27, a resistor 28, 29, and an amplifier 5.
0, a variable resistor 51, and a diode 3.
The cathode side of the diode 52 of the output section is connected to the resistor 17 in the PWM conversion section 11.
and the resistor 18.

By adding such a low voltage detection circuit 22,
When the welding rod 4-1 and the object to be welded 4-2 are brought into contact and the voltage between the arc welding part is reduced to zero, the output of the amplifier 30 becomes the control power supply voltage, and is output to the amplifier 15 via the variable resistor 51 and the diode 32. is input. Therefore, the potential of the inverting input terminal of the amplifier 15 increases, so the output of the amplifier 15 decreases, and a signal is sent to the drive circuit 7 via the PWM circuit 20 and the bus amplifier circuit 21 to increase the on-time of the mayfting element 20. is output, and when the voltage between the arc welding parts is made zero at time to as shown in FIG. 2, the peak current ip flows through the nutching element 2K. When the temperature of the contact portion with resistor 2 rises, the resistance increases, the voltage rises, and the potential at the connection point between resistor 24 and resistor 25 rises. As a result, the operation of the low voltage detection circuit 22 is canceled, the output of the amplifier 50 becomes zero, and the potential at the connection point between the resistors 17 and 18 becomes dependent on the voltage of the shunt 5, as shown in FIG. At time t1, peak current ip decreases to constant current value io. Therefore, the temperature can be raised to a temperature at which arc discharge occurs in a short time, and m* welding can be performed.

In the above embodiment, the variable resistor 25 is for adjusting the value of ip.

Effects of the Invention As described above, by adding a low voltage detection circuit, the present invention can supply a peak current larger than the constant current value from the power supply during welding, and the arc fB
A t-source device suitable for direct contact can be obtained.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply device of the present invention, FIG. 2 is a diagram of its operating characteristics, FIG. 3 is a circuit diagram of a conventional power supply device, and FIG. 4 is a diagram of its operating characteristics. 1...Storage battery 2...Switching element 4
...Arc welding part 5...Shunt 7...Drive circuit 8...Control circuit 11...PWM converter 1
2... Control [source section 20... PWM circuit 21...
・Pass/L' pass amplifier circuit 22...Low voltage detection circuit

Claims (1)

[Claims] A closed circuit is formed by a DC power source, a switching element for switching the output of the DC power source, a reactor, an arc welding section to which a welding rod and an object to be welded are attached, and a shunt, and the output of the shunt is a control circuit that creates a pulse width control signal that is input and makes the current flowing through the closed circuit a constant current; a drive circuit that converts the output of this control circuit into a drive signal for the switching element; and a low voltage detection circuit that detects a voltage drop, and a function of inputting a voltage drop signal detected by the low voltage detection circuit to the control circuit to obtain a pulse width control signal for causing a peak current to flow through the closed circuit. A power supply device comprising: