JPH0929454A - Synchronization inverter welding power source - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high reliability welded part with stabilized quality by forcedly resetting a ramp signal of PWMI each time a welding drive control signal is inputted so as to make welding power at each welding time constant. SOLUTION: A reset signal generating part 10 receives a welding drive control signal S3, further a reset signal RST, which resets a ramp signal with a pulse width sufficiently narrower than a period of a lamp signal at the same time as the welding drive control signal S3 is turned on, is generated. A PWM control part 11 receives the signal RST from the reset signal generating part 10, and a function to forcedly reset the lamp signal is added, so that the welding drive control signal S3 and lamp signal are synchronized. At the same time the welding drive control signal S3 is turned on, the reset signal RST is generated and the ramp signal is forcedly reset, thus, the pulse widths of inverter drive signals S11, S12 are made equal from welding start, the welding drive control signal S3 is turned on, the actual welding start timing is always made constant.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a welding power source, and more particularly to a control circuit for making an actual welding start timing constant from a welding start signal.

[0002]

2. Description of the Related Art FIG. 3 shows a block diagram of a conventional inverter welding power source, and FIG. 4 shows an operation timing chart of an inverter drive unit of the conventional inverter welding power source. As shown in FIG. 3, the conventional inverter welding power source basically includes a rectifying / smoothing section 1, an inverter section 2, a welding transformer 3, a rectifying section 4, a welding current detecting element 5, welding heads 6a and 6b, and
Amplifying and multiplying unit 7, PWM (Pulse Width Mo
duration) control unit 8 and welding condition setting unit 9.

The operation of the conventional inverter welding power source will be described with reference to FIG. As is well known, commercial three-phase alternating current is input to the rectifying / smoothing unit 1, rectified and smoothed, and then input to the inverter unit 2. The inverter unit 2 is composed of four transistors, and the inverter drive signals S1 and S2 of a predetermined frequency sufficiently higher than the commercial AC frequency from the PWM control unit 8 divide the four transistors into two sets of transistors and alternately. A high frequency AC rectangular wave is output by turning on / off.

The high frequency AC rectangular wave output from the inverter unit 2 is supplied to the primary coil of the welding transformer 3 to generate a low voltage, large current pulse in the secondary coil. The low-voltage, high-current pulse generated in the secondary coil is converted into direct current by the rectifying unit 4 composed of a pair of diodes, and the welding current IW corresponding thereto is converted into the welding heads 6a, 6b.
And resistance heat is generated in the object to be welded.

Next, the generation of the inverter drive signals S1 and S2 of the PWM control section 8 will be described by taking welding power as an example. A hall element 5 is provided to detect the welding current IW, and a voltage V1 proportional to the welding current IW detected by the hall element 5 is input to one of the amplification / multiplication units 7. Also,
A voltage drop corresponding to the resistance value of the object to be welded occurs between the welding heads 6a and 6b. This dropped voltage V2 is similarly input to the other side of the amplification / multiplication unit 7. This amplification multiplication unit 7
Then, the current obtained by converting the voltage V1 into a current and the drop voltage V2 are amplified and multiplied to obtain the welding power PW.

The PWM control unit 8 uses a commercially available PWM IC to generate a ramp signal S4 having a frequency determined by an external timing resistor and capacitor, and uses the welding power setting value PS of the welding condition setting unit 9 as the welding power setting value PS. The inverter drive signals S1 and S are set so that the welding power PW from the amplification / multiplication unit 7 matches.
Generate 2. This is shown in FIG. FIG.
In (A), a welding drive control signal S3 for starting and ending welding from a sequence control unit (not shown),
(B) is a ramp signal S4 generated by the PWM IC,
(C) is a control level P obtained by feeding back the welding power PW from the amplification / multiplication unit 7 to match it with the welding power value PS from the welding condition setting unit 9, and (D) is a ramp signal S4 and control level. Inverter drive signals S1 and (E) obtained by comparing with P are also inverter drive signals S2.

[0007]

As shown in FIG. 4, since the welding drive control signal S3 and the ramp signal S4 are asynchronous, the inverter drive signals S1 and S2 at the start and end of welding.
The pulse width of is different from that at other times and changes at every welding operation. As a result, the welding start timing finally obtained is delayed, the welding power as a whole is changed, and even if welding is performed under the same welding conditions, the actual power will differ for each welding. there were. The present invention has been made to solve the above problems, and an object of the present invention is to provide a synchronous inverter welding power supply which has a simple structure and enables welding under uniform conditions for each welding.

[0008]

The present invention is obtained from a voltage detecting section for detecting a voltage applied to a work piece, a current detecting section for detecting a current flowing through the work piece, and the current detecting section. Amplifying and multiplying unit for multiplying the measured current value and the measured voltage value obtained from the voltage detection unit to calculate the electric power value supplied to the workpiece, the welding current for constant current control, or the constant voltage Welding condition control section for setting welding voltage for control or welding power for constant power control as welding conditions, inverter section composed of transistor for converting DC to AC, and welding drive control signal , So that the power value from the amplification multiplication unit and the welding power value from the welding condition setting unit match, or the voltage value from the voltage detection unit and the welding voltage value from the welding condition setting unit match Or the above Inverter control section having a pulse width modulation circuit as a main constituent element for controlling the conduction time of the transistor forming the inverter section so that the measured current value from the flow detection section and the welding current value from the welding condition setting section match. In the inverter welding power source having, a reset pulse generation unit that receives the welding drive control signal and resets the ramp signal of the inverter control unit is provided.

[0009]

According to the present invention, the PWM is applied at every welding drive signal.
By forcibly resetting the ramp signal of the IC, the pulse width of the inverter drive signal can be made the same at the start of welding and at other times, so that welding can be performed under uniform conditions for each welding. .

[0010]

1 is a block diagram of a synchronous inverter welding power source showing an embodiment of the present invention, and FIG. 2 is a timing chart diagram for explaining the operation of the synchronous inverter welding power source. In FIG. 1, reference numerals 1 to 7 and 9 are the same as those assigned the same reference numeral in FIG. 1, and 10 receives the welding drive control signal S3 and the welding drive control signal S3 is turned on. At the same time,
A reset signal generation unit that generates a reset signal RST that resets the ramp signal S4 with a pulse width that is sufficiently narrower than the cycle of the ramp signal S4, and the PWM control unit 11 is functionally equivalent to that given the reference numeral 8 in FIG. Although equivalent, a function of forcibly resetting the ramp signal S4 in response to the reset signal RST from the reset signal generator 10 is added, so that the welding drive control signal S3 and the ramp signal S4 can be synchronized. ing. This is shown in FIG. In FIG. 2, (A) is a welding drive control signal S3 for starting and ending welding from a sequence control unit (not shown), (B) is a reset signal RST from a reset signal generating unit 10, and (C) is the PWM IC. Is generated from the welding power PW and the welding power value PS, and (E) is an inverter drive signal S obtained by comparing the ramp signal S4 with the control level P.
Similarly, 11 and (F) are inverter drive signals S12. By doing so, the reset signal RST is generated at the same time that the welding drive control signal S3 is turned on, and the ramp signal S4 is forcibly reset. From the beginning, they are equal, and the actual welding start timing after the welding drive control signal S3 is turned on is always constant.

[0011]

According to the present invention, as described above,
Since the ramp signal S4 of the PWM IC is forcibly reset every time the welding drive control signal S3 is input, the pulse widths of the inverter drive signals S11 and S12 become the same width at the start of welding and at other times. Therefore, the welding power for each welding is constant, and stable and reliable welding with stable quality can be performed.

[Brief description of drawings]

FIG. 1 is a block diagram of a synchronous inverter welding power source showing an embodiment of the present invention.

FIG. 2 is a timing chart illustrating the operation of the synchronous inverter welding power source of FIG.

FIG. 3 is a block diagram of a conventional inverter welding power source.

FIG. 4 is a timing chart illustrating the operation of the inverter welding power source of FIG.

[Explanation of symbols]

 1 Rectifying / smoothing part 1 2 Inverter part 3 Welding transformer 4 Rectifying part 5 Hall element 6a, 6b Welding head 7 Amplifying and multiplying part 8 11 PWM control part 9 Welding condition setting part 10 Reset signal generating part

Claims (1)

[Claims] 1. A voltage detector for detecting a voltage applied to a workpiece, a current detector for detecting a current flowing through the workpiece, a measured current value obtained from the current detector, and the voltage detector. Amplification and multiplication unit that calculates the electric power value supplied to the workpiece by multiplying the measured voltage value obtained from the unit, the welding current for constant current control, or the welding voltage for constant voltage control, or A welding condition setting unit that sets welding power for constant power control as a welding condition, an inverter unit configured by a transistor that converts direct current to alternating current, and a power from the amplification multiplication unit that receives a welding drive control signal. So that the value and the welding power value from the welding condition setting unit match, or the voltage value from the voltage detecting unit and the welding voltage value from the welding condition setting unit match, or from the current detecting unit Measured current value In an inverter welding power source having an inverter control section having a pulse width modulation circuit as a main constituent element for controlling the conduction time of a transistor forming the inverter section so that the welding current values from the welding condition setting section match each other, A synchronous inverter welding power source, comprising: a reset pulse generation unit that receives the welding drive control signal and resets a ramp signal of the inverter control unit.