JP2019025503A - Welding power supply device - Google Patents

Abstract

To provide a welding power supply device which can further suppress arc interruption.SOLUTION: A welding power supply device A1 comprises: an inverter circuit 2 for controlling an output; a rectification circuit 4 for rectifying high-frequency power which is outputted from the inverter circuit 2; an inverter circuit 7 which converts DC power, which is outputted from the rectification circuit 4, into AC power, and outputs the same to a welding load; a reignition circuit 6 which applies a reignition voltage to the output of the welding load when a polarity of output current of the inverter circuit 7 is changed; and a control circuit 8 which outputs an output control driving signal for driving the inverter circuit 2. The reignition circuit 6 charges a part of output power of the inverter circuit 2 in order to apply the reignition voltage. The control circuit 8 increases a frequency of the output control driving signal without changing a pulse width thereof when it is determined that a duty ratio of the output control driving signal becomes small, and therefore, an amount of charge of the reignition circuit 6 is insufficient.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a welding power source apparatus for AC arc welding.

  In AC arc welding, arc breakage is likely to occur when the polarity of the output current is switched. In order to suppress the arc break, a welding power supply apparatus that applies a high voltage (re-ignition voltage) at a timing at which the polarity of the output current switches is known. An example of such a welding power source apparatus is disclosed in Patent Document 1.

  FIG. 8 is a block diagram showing an example of a conventional welding power supply device, and shows the overall configuration of the welding system. The welding system shown in FIG. 8 includes a welding torch B and a welding power source device A100 that supplies electric power to the welding torch B. The welding power source device A100 converts AC power input from the commercial power source D into DC power using the rectifying and smoothing circuit 1, and converts it into high frequency power using the inverter circuit 2. Then, the voltage is transformed by the transformer 3, converted to DC power by the rectifier circuit 4, converted to AC power by the inverter circuit 7, and output. The re-ignition circuit 6 applies a re-ignition voltage when the polarity of the output current of the inverter circuit 7 is switched. The re-ignition circuit 6 is supplied with a part of the high-frequency power output from the inverter circuit 2 from the auxiliary winding 3 c of the transformer 3, and charges the re-ignition capacitor 62 by the charging circuit 63. Then, the electric power charged in the re-ignition capacitor 62 is discharged by the discharge circuit 64. The control circuit 800 controls switching of the inverter circuit 2 and the inverter circuit 7. Further, the control circuit 800 controls the charging circuit 63 and the discharging circuit 64 to control the timing of charging and discharging the re-ignition voltage. In welding power supply apparatus A100, since the re-ignition voltage is applied when the polarity of the output current of inverter circuit 7 is switched, the occurrence of arc break is suppressed.

  In addition, the welding power source apparatus A100 includes an overcurrent detection circuit 88. The overcurrent detection circuit 88 is a circuit that detects an overcurrent of the output current of the welding power source apparatus A100. The overcurrent detection circuit 88 outputs an overcurrent detection signal to the control circuit 800 when the current detected by the current sensor 91 becomes an overcurrent. When an overcurrent detection signal is input, the control circuit 800 decreases the voltage supplied to the inverter circuit 7 by reducing the pulse width of the drive signal output to the inverter circuit 2 and reducing the duty ratio. Thus, the output power of the inverter circuit 7 is suppressed.

Japanese Patent Application Laid-Open No. 07-96367

  In the welding power source apparatus A100, when an overcurrent is detected, the duty ratio of the output voltage waveform of the inverter circuit 2 becomes small, so the voltage supplied to the re-ignition circuit 6 and rectified and smoothed becomes low. In this case, it takes a long time to charge the re-ignition capacitor 62 to a predetermined voltage (the charging speed is slow). When the charging speed is reduced, the re-ignition capacitor 62 may be discharged before it is sufficiently charged. If the battery is discharged in a state where charging is insufficient, the voltage applied to the output of the inverter circuit 7 becomes low, the energy for re-ignition becomes insufficient, and an arc break occurs.

  The present invention has been conceived under the circumstances described above, and an object of the present invention is to provide a welding power supply apparatus that can further suppress the occurrence of arc breakage.

  The welding power supply device provided by the first aspect of the present invention includes a first inverter circuit for controlling output, a rectifier circuit for rectifying high-frequency power output from the first inverter circuit, and the rectifier circuit. When the polarity of the output current of the second inverter circuit that converts the DC power output from the converter into AC power and outputs it to the welding load is switched, the output to the welding load is re-pointed. A re-ignition circuit for applying an arc voltage; and a control circuit for outputting an output control drive signal for driving the first inverter circuit, wherein the re-ignition circuit is an output of the first inverter circuit. A part of the electric power is charged to apply the re-ignition voltage, and the control circuit has insufficient charge amount of the re-ignition circuit due to a decrease in the duty ratio of the output control drive signal. Then If it is sectional, the pulse width of the output control drive signal is characterized by a higher frequency as is. According to this configuration, the control circuit increases the frequency without changing the pulse width of the output control drive signal when the charge amount of the re-ignition circuit is insufficient because the duty ratio of the output control drive signal is reduced. As a result, the waveform of the high-frequency voltage output from the first inverter circuit also changes in the same manner as the output control drive signal, and the voltage rectified and smoothed by being supplied to the re-ignition circuit becomes high. Therefore, the charging speed of the re-ignition capacitor is increased. Thereby, since it can charge so that the charge amount of a re-ignition circuit may not run short, generation | occurrence | production of arc interruption can be suppressed more.

  In a preferred embodiment of the present invention, the re-ignition circuit includes a re-ignition capacitor that is charged with the re-ignition voltage, and a voltage sensor that detects a voltage between terminals of the re-ignition capacitor. The control circuit determines that the amount of charge is insufficient when the voltage between the terminals is smaller than the threshold voltage at a predetermined timing based on the timing at which the polarity of the output current of the second inverter circuit is switched. According to this configuration, since it is possible to appropriately determine that the amount of charge is insufficient, it is possible to cope with the amount of charge not being insufficient. Therefore, generation | occurrence | production of an arc break can be suppressed more.

  In a preferred embodiment of the present invention, when the duty ratio is less than or equal to a predetermined value at a predetermined timing based on the timing at which the polarity of the output current of the second inverter circuit is switched, Judge that there is a shortage. According to this configuration, since it is possible to appropriately determine that the amount of charge is insufficient, it is possible to cope with the amount of charge not being insufficient. Therefore, generation | occurrence | production of an arc break can be suppressed more.

  In a preferred embodiment of the present invention, the control circuit increases the frequency of the output control drive signal when the re-ignition voltage can be charged to the target voltage after increasing the frequency of the output control drive signal. Revert. According to this configuration, since the period during which the frequency of the output control drive signal is increased is limited, the effect of increasing the frequency is limited.

  In a preferred embodiment of the present invention, the control circuit further includes an overcurrent detection circuit that detects an overcurrent of the output current of the second inverter circuit, and the control circuit detects the overcurrent by the overcurrent detection circuit. In this case, the pulse width of the output control drive signal is reduced. According to this configuration, even when the pulse width of the output control drive signal is reduced due to overcurrent detection, the frequency is increased while maintaining the pulse width of the output control drive signal, so that the occurrence of arc interruption can be further suppressed. .

  In a preferred embodiment of the present invention, the control circuit sets a target current setting unit that alternately sets a first target current and a second target current smaller than the first target current as a target current; A current control unit configured to generate the output control drive signal based on the target current and a detected value of the output current of the second inverter circuit, wherein the target current is changed from the first target current to the first current. When the target current is switched to 2, the pulse width of the output control drive signal is reduced. According to this configuration, even when the pulse width of the output control drive signal becomes small when the target current is switched, the occurrence of arc break can be further suppressed.

  In a preferred embodiment of the present invention, the control circuit increases the frequency at a rate corresponding to a decrease rate of the pulse width of the output control drive signal. According to this configuration, the frequency of the output control drive signal can be set to an appropriate frequency.

In a preferred embodiment of the present invention, the control circuit sets the remaining time until the timing when the polarity of the output current of the second inverter circuit is switched to T, the reduction rate of the pulse width to W, and a predetermined coefficient. When α is set, the rate F for increasing the frequency is
F = α / (W · T)
Calculate as According to this configuration, the frequency of the output control drive signal can be set to a more appropriate frequency.

  According to the present invention, the control circuit increases the frequency while maintaining the pulse width of the output control drive signal as it is when the charge amount of the re-ignition circuit is insufficient because the duty ratio of the output control drive signal is reduced. As a result, the waveform of the high-frequency voltage output from the first inverter circuit also changes in the same manner as the output control drive signal, and the voltage rectified and smoothed by being supplied to the re-ignition circuit becomes high. Therefore, the charging speed of the re-igniting capacitor is increased. Thereby, since it can charge so that the charge amount of a re-ignition circuit may not run short, generation | occurrence | production of arc interruption can be suppressed more.

It is a block diagram which shows the welding power supply device which concerns on 1st Embodiment. It is a circuit diagram which shows the charge circuit and discharge circuit which concern on 1st Embodiment. It is a time chart for demonstrating control of a re-ignition circuit, and has shown the waveform of each signal of a welding power supply device. It is a time chart for demonstrating overcurrent suppression control, and has shown the waveform of each signal of a welding power supply device. It is a flowchart which shows the current control switching process which the current control part which concerns on 1st Embodiment performs. It is a block diagram which shows the welding power supply device which concerns on 2nd Embodiment. It is a block diagram which shows the welding power supply device which concerns on 3rd thru | or 5th embodiment. It is a block diagram which shows an example of the conventional welding power supply device.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  1-5 is a figure for demonstrating the welding power supply device which concerns on 1st Embodiment. FIG. 1 is a block diagram showing a welding power source device A1, and shows the overall configuration of the welding system. FIG. 2 is a circuit diagram showing an example of the charging circuit 63 and the discharging circuit 64 of the welding power source apparatus A1. FIG. 3 is a time chart for explaining the control of the re-ignition circuit 6, and shows waveforms of signals of the welding power source apparatus A1. FIG. 4 is a time chart for explaining the overcurrent suppression control, and shows waveforms of signals of the welding power source device A1. FIG. 5 is a flowchart showing a current control switching process performed by the current control unit 81.

  As shown in FIG. 1, the welding system includes a welding power source device A1 and a welding torch B. The welding system is, for example, a TIG welding system that performs AC arc welding. The welding power source device A1 converts AC power input from the commercial power source D and outputs it from the output terminals a and b. One output terminal a is connected to the workpiece W by a cable. The other output terminal b is connected to the electrode of the welding torch B by a cable. The welding power supply device A1 generates an arc between the tip of the electrode of the welding torch B and the workpiece W to supply electric power. Welding is performed by the heat of the arc. Since the combination of the welding torch B, the workpiece W, and the generated arc is the load of the welding power source device A1, the combination of these is described as “welding load”.

  The welding power supply device A1 includes a rectifying / smoothing circuit 1, an inverter circuit 2, a transformer 3, a rectifying circuit 4, a DC reactor 5, a re-ignition circuit 6, an inverter circuit 7, a control circuit 8, an overcurrent detection circuit 88, a current sensor 91, And a voltage sensor 92.

  The rectifying / smoothing circuit 1 converts AC power input from the commercial power source D into DC power and outputs the DC power. The rectifying / smoothing circuit 1 includes a rectifying circuit for rectifying an alternating current and a smoothing capacitor for smoothing.

  The inverter circuit 2 is, for example, a single-phase full bridge type PWM control inverter, and includes four switching elements. The inverter circuit 2 converts the DC power input from the rectifying / smoothing circuit 1 into high-frequency power by switching the switching element according to the output control drive signal input from the control circuit 8, and outputs the high-frequency power. The inverter circuit 2 only needs to convert DC power into AC power, and may be, for example, a half-bridge type or an inverter circuit having another configuration. The inverter circuit 2 corresponds to the “first inverter circuit” of the present invention.

  The transformer 3 transforms the high-frequency voltage output from the inverter circuit 2 and outputs it to the rectifier circuit 4. The transformer 3 includes a primary winding 3a, a secondary winding 3b, and an auxiliary winding 3c. Each input terminal of the primary winding 3 a is connected to each output terminal of the inverter circuit 2. Each output terminal of the secondary winding 3 b is connected to each input terminal of the rectifier circuit 4. The output voltage of the inverter circuit 2 is transformed according to the turn ratio of the primary side winding 3 a and the secondary side winding 3 b and is input to the rectifier circuit 4. Each output terminal of the auxiliary winding 3 c is connected to each input terminal of the charging circuit 63. The output voltage of the inverter circuit 2 is transformed according to the turn ratio of the primary winding 3 a and the auxiliary winding 3 c and is input to the charging circuit 63. Since the secondary winding 3b and the auxiliary winding 3c are insulated from the primary winding 3a, the current input from the commercial power source D is prevented from flowing to the secondary circuit and the charging circuit 63. be able to.

  The rectifier circuit 4 is a full-wave rectifier circuit, for example, and rectifies high-frequency power input from the transformer 3 and outputs the rectified circuit to the inverter circuit 7. The rectifier circuit 4 only needs to rectify high-frequency power, and may be a half-wave rectifier circuit, for example. The direct current reactor 5 smoothes the direct current that the rectifier circuit 4 outputs to the inverter circuit 7.

  The inverter circuit 7 is, for example, a single-phase full-bridge type PWM control inverter and includes four switching elements. The inverter circuit 7 converts the DC power input from the rectifier circuit 4 into AC power and outputs it by switching the switching element according to the switching drive signal input from the control circuit 8. The inverter circuit 7 only needs to convert DC power into AC power, and may be, for example, a half-bridge type or an inverter circuit having another configuration. The inverter circuit 7 corresponds to the “second inverter circuit” of the present invention.

  The re-ignition circuit 6 is disposed between the rectifier circuit 4 and the inverter circuit 7, and when the polarity of the output current of the inverter circuit 7 is switched, the re-ignition circuit 6 is high between the output terminals a and b of the welding power source device A1. Apply voltage. The high voltage is for improving the re-ignition property at the time of polarity switching, and may be referred to as “re-ignition voltage” below. The re-ignition circuit 6 includes a diode 61, a re-ignition capacitor 62, a charging circuit 63 and a discharging circuit 64.

  The re-ignition capacitor 62 is a capacitor having a predetermined electrostatic capacity or more, and is charged with a re-ignition voltage to be applied to the output of the welding power source device A1. The re-ignition capacitor 62 is connected in parallel to the rectifier circuit 4. The re-ignition capacitor 62 is charged by the charging circuit 63 and discharged by the discharging circuit 64.

  The charging circuit 63 is a circuit for charging the re-ignition capacitor 62 with a re-ignition voltage, and is connected to the re-ignition capacitor 62 in parallel. FIG. 2A is a diagram illustrating an example of the charging circuit 63. As shown in FIG. 2A, in the present embodiment, the charging circuit 63 includes a rectifying / smoothing circuit 63c and an insulating forward converter 63d. The rectifying / smoothing circuit 63c includes a rectifying circuit for full-wave rectifying the AC voltage and a smoothing capacitor for smoothing, and converts the high-frequency voltage input from the auxiliary winding 3c of the transformer 3 into a DC voltage. The circuit configuration of the rectifying / smoothing circuit 63c is not limited. The insulated forward converter 63d boosts the DC voltage input from the rectifying / smoothing circuit 63c and outputs the boosted DC voltage to the re-ignition capacitor 62. The insulated forward converter 63d includes a drive circuit 63a for driving the switching element 63b. The drive circuit 63a outputs a pulse signal for driving the switching element 63b based on a charge circuit drive signal input from a charge control unit 86 described later. The drive circuit 63a outputs a predetermined pulse signal to the switching element 63b while the charging circuit drive signal is on (for example, a high level signal). As a result, the re-ignition capacitor 62 is charged. On the other hand, the drive circuit 63a does not output a pulse signal while the charging circuit drive signal is off (for example, a low level signal). Therefore, charging of the re-ignition capacitor 62 is stopped. That is, the charging circuit 63 switches between a state where the re-ignition capacitor 62 is charged and a state where it is not charged based on the charging circuit drive signal. Instead of providing the drive circuit 63a, the charge control unit 86 may directly input a pulse signal as a charge circuit drive signal to the switching element 63b. Further, the configuration of the charging circuit 63 is not limited. The charging circuit 63 may include a step-up chopper circuit or the like instead of the insulated forward converter 63d.

  The discharge circuit 64 discharges the re-ignition voltage charged in the re-ignition capacitor 62 and is connected to the re-ignition capacitor 62 in series. FIG. 2B is a diagram illustrating an example of the discharge circuit 64. As shown in FIG. 2B, the discharge circuit 64 includes a switching element 64a and a current limiting resistor 64b. In the present embodiment, the switching element 64a is an IGBT (Insulated Gate Bipolar Transistor). The switching element 64a may be a bipolar transistor, a MOSFET (Metal Oxide Semiconductor Field Effect Transistor), or the like. The switching element 64 a and the current limiting resistor 64 b are connected in series and are connected in series to the re-ignition capacitor 62. The emitter terminal of the switching element 64a is connected to the positive terminal of the rectifier circuit 4, and the collector terminal of the switching element 64a is connected to one terminal of the current limiting resistor 64b. The current limiting resistor 64b may be connected to the emitter terminal side of the switching element 64a. In addition, a discharge circuit drive signal is input to the gate terminal of the switching element 64a from a discharge control unit 85 described later. The switching element 64a is turned on while the discharge circuit drive signal is on (for example, a high level signal). Thereby, the re-ignition voltage charged in the re-ignition capacitor 62 is discharged via the current limiting resistor 64b. On the other hand, the switching element 64a is turned off while the discharge circuit drive signal is off (for example, a low level signal). Thereby, the discharge of the re-ignition voltage is stopped. That is, the discharge circuit 64 switches between a state where the re-ignition capacitor 62 is discharged and a state where it is not discharged based on the discharge circuit drive signal. The configuration of the discharge circuit 64 is not limited.

  The diode 61 is connected in parallel to the discharge circuit 64, the anode terminal is connected to the positive terminal of the input of the inverter circuit 7, and the cathode terminal is connected to the re-ignition capacitor 62. The diode 61 causes the re-ignition capacitor 62 to absorb the transient voltage of the input voltage of the inverter circuit 7.

  The current sensor 91 detects the output current of the welding power source device A1, and in this embodiment, the current sensor 91 is disposed on a connection line that connects one output terminal of the inverter circuit 7 and the output terminal a. The current sensor 91 detects an instantaneous value of the output current and inputs it to the control circuit 8 and the overcurrent detection circuit 88. In this embodiment, the case where the current flows from the inverter circuit 7 toward the output terminal a is positive, and the case where the current flows from the output terminal a toward the inverter circuit 7 is negative. The arrangement position of the current sensor 91 is not limited.

  The voltage sensor 92 detects the voltage between the terminals of the re-ignition capacitor 62. The voltage sensor 92 detects an instantaneous value of the inter-terminal voltage and inputs it to the control circuit 8.

  The overcurrent detection circuit 88 is a circuit that detects an overcurrent of the output current of the welding power source device A1. The overcurrent detection circuit 88 calculates an effective value from the instantaneous value of the output current input from the current sensor 91, and determines that it is an overcurrent when the effective value is greater than a predetermined current threshold. When the overcurrent detection circuit 88 detects an overcurrent, it outputs an overcurrent detection signal to the control circuit 8.

  The control circuit 8 is a circuit for controlling the welding power source device A1, and is realized by, for example, a microcomputer. The control circuit 8 receives the instantaneous value of the output current from the current sensor 91, and receives the instantaneous value of the voltage across the terminals of the re-ignition capacitor 62 from the voltage sensor 92. Then, the control circuit 8 outputs drive signals to the inverter circuit 2, the inverter circuit 7, the charging circuit 63, and the discharging circuit 64, respectively. The control circuit 8 includes a current control unit 81, a target current setting unit 82, a polarity switching control unit 83, a waveform target setting unit 84, a discharge control unit 85, a charge control unit 86, and a timing detection unit 87.

  The current control unit 81 controls the inverter circuit 2. The current control unit 81 calculates an effective value from the instantaneous value of the output current input from the current sensor 91, and performs PWM based on the effective value and the target current (effective value) input from the target current setting unit 82. By the control, an output control drive signal for controlling the switching element of the inverter circuit 2 is generated and output to the inverter circuit 2. In addition, when an overcurrent detection signal is input from the overcurrent detection circuit 88, the current control unit 81 stops PWM control and performs overcurrent suppression control for suppressing overcurrent. When the overcurrent is eliminated and the overcurrent detection signal is no longer input from the overcurrent detection circuit 88, the current control unit 81 stops the overcurrent suppression control and restarts the PWM control. Details of the overcurrent suppression control will be described later.

  The polarity switching control unit 83 controls the inverter circuit 7. The polarity switching control unit 83 performs switching for controlling the switching elements of the inverter circuit 7 based on the instantaneous value of the output current input from the current sensor 91 and the current waveform target value input from the waveform target setting unit 84. A drive signal is generated and output to the inverter circuit 7.

  The discharge controller 85 controls the discharge circuit 64. The discharge control unit 85 generates a discharge circuit drive signal for controlling the discharge circuit 64 based on the switching drive signal input from the polarity switching control unit 83 and outputs the generated discharge circuit drive signal to the discharge circuit 64. The discharge circuit drive signal is also input to the charge control unit 86.

  As shown in FIG. 3, the output current (see FIG. 3B) of the welding power source device A <b> 1 changes according to the switching drive signal (see FIG. 3A). The switching drive signal shown in FIG. 3 (a) is positive when the output terminal a (workpiece W) is positive, negative when the output terminal b (welding torch B) is on, and output terminal a (workpiece) when it is off. The object W) is negative, and the output terminal b (welding torch B) is positive. The output current of the welding power source device A1 decreases from the time when the switching drive signal is switched from on to off (time t1 in FIG. 3), passes the zero (time t2 in FIG. 3), and then reaches the minimum current after the polarity changes. Value (time t3 in FIG. 3). Further, the output current of the welding power source device A1 increases from when the switching drive signal is switched from OFF to ON (time t5 in FIG. 3), and after zero (time t6 in FIG. 3), after the polarity is changed. The maximum current value is reached (time t7 in FIG. 3). The discharge controller 85 generates a discharge circuit drive signal so as to be turned on when the polarity of the output current of the welding power supply device A1 changes. Specifically, the discharge controller 85 turns on when the switching drive signal is switched (time t1, t5 in FIG. 3), and turns off when the discharge time has elapsed after switching on. A switching pulse signal is generated and output as a discharge circuit drive signal (see FIG. 3C). The discharge time is a time during which the discharge state is continued, and a predetermined time longer than the time until the polarity of the output current changes is set. In the present embodiment, since the predetermined time is set as the time until the instantaneous value of the output current becomes the maximum current value or the minimum current value, the discharge circuit drive signal shown in FIG. Switched off at t7. Actually, the timing at which the instantaneous value of the output current becomes the maximum current value or the minimum current value does not always coincide with the timing at which the discharge circuit drive signal is switched off.

  Note that the method by which the discharge control unit 85 generates the discharge circuit drive signal is not limited to this. Since it is sufficient that a re-ignition voltage can be applied when the polarity of the output current of the welding power source device A1 changes, the discharge circuit drive signal may be turned on before the polarity is changed and turned off after the polarity is changed. For example, the discharge circuit drive signal may be switched off when an instantaneous value of the output current is input from the current sensor 91 and a predetermined time elapses after the instantaneous value of the output current becomes zero. Further, switching may be performed when the instantaneous value of the output current reaches the maximum current value or the minimum current value. Actually, since the instantaneous current value input from the current sensor 91 fluctuates slightly, it is determined that the maximum current value is reached when the instantaneous current value is equal to or greater than a predetermined first threshold value. What is necessary is just to judge that it became the minimum electric current value when it became below a predetermined 2nd threshold value. In addition, instead of receiving the switching drive signal from the polarity switching control unit 83, the discharge control unit 85 receives the current waveform target value from the waveform target setting unit 84, and when the current waveform target value is switched, The circuit drive signal may be switched on. Also in this case, the waveform of the discharge circuit drive signal is the same as that in the case of switching based on the switching drive signal. Alternatively, the discharge circuit drive signal may be switched on when the instantaneous value of the output current decreases from the maximum current value or increases from the minimum current value. Also in this case, the waveform of the discharge circuit drive signal is the same as that in the case of switching based on the switching drive signal. Further, a first threshold value smaller than the maximum current value and larger than zero and a second threshold value larger than the minimum current value and smaller than zero are set, and the discharge circuit drive signal is set so that the instantaneous value of the output current is the first threshold value and the second threshold value. It may be switched on when entering the range between and off when switching out of the range. Even in this case, the discharge circuit drive signal is turned on before the polarity is changed and turned off after the polarity is changed.

  The charging control unit 86 controls the charging circuit 63. The charging control unit 86 controls the charging circuit 63 based on the discharge circuit drive signal input from the discharge control unit 85 and the instantaneous value of the voltage across the re-ignition capacitor 62 input from the voltage sensor 92. The charging circuit drive signal for generating the charging circuit is generated and output to the charging circuit 63.

  As shown in FIG. 3, the voltage between the terminals of the re-ignition capacitor 62 (see FIG. 3E) is turned on (time t1 in FIG. 3) when the discharge circuit drive signal (see FIG. 3C) is turned on. When the polarity of the output current (see FIG. 3B) changes (time t2 in FIG. 3), it decreases due to the discharge of the re-ignition capacitor 62. It is necessary to charge the re-ignition capacitor 62 with the re-ignition voltage by the next discharge timing (time t6 in FIG. 3). Further, when the re-ignition capacitor 62 is charged to the target voltage, it is not necessary to perform further charging. The charging control unit 86 generates a charging circuit drive signal so as to be turned on after the re-ignition capacitor 62 is discharged until the re-ignition capacitor 62 reaches the target voltage. Specifically, the charge control unit 86 switches on when the discharge circuit drive signal input from the discharge control unit 85 switches from on to off (time t3, t7 in FIG. 3), and re-ignitions. When the voltage between the terminals of the capacitor 62 reaches the target voltage (time t4, t8 in FIG. 3), a pulse signal that is turned off is generated and output as a charging circuit drive signal (see FIG. 3D).

The timing detector 87 detects the timing for comparing the voltage across the terminals of the re-ignition capacitor 62 with the threshold voltage V ₀ in the overcurrent suppression control described later. Specifically, the timing detection unit 87 detects a comparison timing that is a predetermined time T before the next switching timing of the switching drive signal based on the switching drive signal input from the polarity switching control unit 83. Since the switching drive signal is periodically switched, the comparison timing can be detected by measuring the time from the previous switching timing. Strictly speaking, there is a time difference between the switching drive signal switching timing and the output current polarity switching timing (time t1 and time t2 in FIG. 3), but the time difference is sufficiently smaller than the predetermined time T. It can be said that the comparison timing is a timing that is a predetermined time T before the timing at which the polarity is switched. Note that the timing detector 87 may detect the comparison timing based on the current waveform target value output by the waveform target setting unit 84 instead of the switching drive signal output by the polarity switching control unit 83. The timing detector 87 may detect the comparison timing by other methods. The timing detection unit 87 outputs a timing signal to the current control unit 81 when the comparison timing is detected.

  Next, the overcurrent suppression control performed by the current control unit 81 will be described.

  The overcurrent suppression control is control that the current control unit 81 performs by stopping the PWM control while the overcurrent detection signal is input from the overcurrent detection circuit 88. The current control unit 81 normally performs PWM control, and performs feedback control so that the effective value of the output current of the welding power source device A1 matches the target current input from the target current setting unit 82. . However, when an overcurrent detection signal is input from the overcurrent detection circuit 88, the current control unit 81 stops PWM control and performs overcurrent suppression control for suppressing overcurrent. In the overcurrent suppression control, the current control unit 81 fixes and fixes the pulse width of the output control drive signal in the immediately preceding PWM control by a predetermined ratio (for example, half) in order to suppress overcurrent. An output control drive signal in which is reduced is generated and output. As a result, the output voltage waveform of the inverter circuit 2 has a reduced duty ratio, and the DC voltage supplied to the inverter circuit 7 is reduced. Therefore, the output power of the inverter circuit 7 is suppressed and the overcurrent is suppressed.

  FIG. 4 is a time chart for explaining overcurrent suppression control. FIG. 4A shows the output voltage waveform of the inverter circuit 2. FIG. 4B shows the waveform of the effective value of the output current of the welding power source device A1. FIG. 4C shows the waveform of the output voltage of the rectifying / smoothing circuit 63 c of the charging circuit 63. FIG. 4D shows a waveform of the voltage Vc between the terminals of the re-ignition capacitor 62.

  At time t11, the output current of the welding power source device A1 increases rapidly, and is larger than the current threshold indicated by the broken line (see FIG. 4B). As a result, the overcurrent detection circuit 88 detects the overcurrent and outputs an overcurrent detection signal to the control circuit 8. The control circuit 8 stops the PWM control and starts the overcurrent suppression control at time t12 due to the input of the overcurrent detection signal. In the overcurrent suppression control, the pulse width of the output control drive signal output to the inverter circuit 2 is fixed to half of the pulse width in the immediately preceding PWM control. Therefore, the pulse width of the output voltage waveform of the inverter circuit 2 is also halved (see FIG. 4A). As a result, the output voltage of the inverter circuit 2 is rectified and smoothed, and the DC voltage input to the inverter circuit 7 decreases. Note that the waveform of the DC voltage input to the inverter circuit 7 is the same as the waveform of FIG. When the DC voltage input to the inverter circuit 7 decreases, the output current of the inverter circuit 7 (output current of the welding power supply device A1) decreases (see FIG. 4B), and the overcurrent is suppressed. .

  However, since the output voltage of the rectifying / smoothing circuit 63c also decreases (see FIG. 4C), the charging speed of the inter-terminal voltage Vc of the re-ignition capacitor 62 decreases (see FIG. 4D). The slope of the inter-terminal voltage Vc after time t12 is smaller than the slope before time t12. If the charging speed remains unchanged, there is a possibility that the amount of charge of the re-ignition capacitor 62 is insufficient when the re-ignition voltage is discharged (time t16).

In the overcurrent suppression control according to the present embodiment, it is determined whether or not the charge amount of the re-ignition capacitor 62 is insufficient. If the charge amount is insufficient, the pulse width of the output control drive signal is kept as it is and the frequency is increased. Output. Specifically, the current control unit 81 compares the inter-terminal voltage Vc of the re-ignition capacitor 62 with the threshold voltage V ₀ when the timing signal is input from the timing detection unit 87 in the overcurrent suppression control, When the inter-terminal voltage Vc is smaller than the threshold voltage V ₀ , it is determined that the amount of charge of the re-ignition capacitor 62 is insufficient. In this case, the current control unit 81 generates and outputs an output control drive signal with a high frequency (for example, 1.5 times) while maintaining the pulse width as it is. As a result, the waveform of the high-frequency voltage output from the inverter circuit 2 also changes in the same manner as the output control drive signal, and the output voltage of the rectifying / smoothing circuit 63c of the charging circuit 63 increases. Therefore, the charging speed of the re-ignition capacitor 62 is increased. Thereby, it can charge so that the charge amount of the re-ignition capacitor | condenser 62 may not run short.

In the time chart shown in FIG. 4, a timing signal is input from the timing detector 87 at a time t13, which is a predetermined time T before the time t16 when the polarity is switched, and the inter-terminal voltage Vc and the threshold voltage V at this time are input. ₀ is compared. Since the inter-terminal voltage Vc is smaller than the threshold voltage V ₀ , the frequency is increased to 1.5 times at the time t14 while keeping the pulse width of the output control drive signal as it is. Therefore, the output voltage waveform of the inverter circuit 2 is similarly 1.5 times the frequency with the pulse width unchanged (see FIG. 4A). As a result, the output voltage of the rectifying / smoothing circuit 63c is increased (see FIG. 4C), and the charging speed of the inter-terminal voltage Vc of the re-ignition capacitor 62 is increased (see FIG. 4D). The slope of the inter-terminal voltage Vc after time t14 is larger than the slope before time t14. Thereafter, at time t15, the inter-terminal voltage Vc becomes the target voltage, charging is stopped, and discharging is performed at time t16 (see FIG. 4D).

The threshold voltage V ₀ and the predetermined time T are preliminarily determined based on the decrease rate of the pulse width of the output control drive signal and the increase rate of the frequency so that it can be appropriately determined that the charge amount of the re-ignition capacitor 62 is insufficient. Is set. If the predetermined time T is lengthened, the threshold voltage V ₀ can be set to a relatively small value. On the other hand, if the predetermined time T is shortened, the threshold voltage V ₀ needs to be a relatively large value. The frequency increase rate F may be calculated from the pulse width decrease rate W and the predetermined time T according to the following equation (1). Α is a predetermined coefficient. For example, when α = 7.5 × 10 ⁻⁵ , T = 0.1 ms, and W = 0.5 (half), F = 1.5. Note that the frequency increase rate F may be a reciprocal of the pulse width decrease rate W (for example, if the pulse width is halved, the frequency is doubled) without considering the predetermined time T.
F = α / (W · T) (1)

  When the inter-terminal voltage Vc reaches the target voltage and charging is stopped, the frequency of the output control drive signal is restored. The output control drive signal is generated at the original frequency until the next comparison timing (when the timing signal is input from the timing detector 87). That is, every time the comparison timing arrives, it is determined whether or not the charge amount is insufficient. Only when it is determined that the charge amount is insufficient, the frequency of the output control drive signal is increased only until the completion of charging. Note that the timing for restoring the frequency of the output control drive signal is not limited to when charging is stopped, and may be when the polarity is switched or when discharging is performed. Since the period for increasing the frequency of the output control drive signal is limited, the influence on the suppression of overcurrent is limited.

  FIG. 5 is a flowchart illustrating a process (hereinafter referred to as “current control switching process”) performed by the current control unit 81 to switch the current control between the PWM control and the overcurrent suppression control. This process is executed while the welding power source device A1 supplies power for welding to the welding torch B. The current control unit 81 normally performs PWM control, and outputs an output control drive signal generated by PWM control to the inverter circuit 2.

  First, it is determined whether or not an overcurrent is detected (S1). Specifically, it is determined whether or not an overcurrent detection signal is input from the overcurrent detection circuit 88. If no overcurrent is detected (S1: NO), the process returns to step S1 and waits until an overcurrent is detected. When an overcurrent is detected (S1: YES), the pulse width of the output control drive signal is reduced (S2). Specifically, the pulse width of the output control drive signal in the immediately preceding PWM control is reduced and fixed at a predetermined ratio (for example, half), and an output control drive signal with a reduced duty ratio is generated and output. Thereby, it switches from PWM control to overcurrent suppression control.

Next, it is determined whether or not the comparison timing has come (S3). Specifically, it is determined whether or not a timing signal is input from the timing detector 87. If it is not the comparison timing (S3: NO), the process returns to step S3 and waits until the comparison timing is reached. When the comparison timing is reached (S3: YES), the inter-terminal voltage Vc of the re-ignition capacitor 62 is detected (S4). Specifically, the inter-terminal voltage Vc input from the voltage sensor 92 is acquired. Next, it is determined whether or not the terminal voltage Vc is smaller than the threshold voltage V ₀ (S5). When the terminal voltage Vc is smaller than the threshold voltage V ₀ (S5: YES), it is determined that the charge amount of the re-ignition capacitor 62 is insufficient, the frequency of the output control drive signal is increased (S6), and the process proceeds to step S7. move on. Specifically, an output control drive signal with an increased frequency is generated and output without changing the pulse width of the immediately preceding output control drive signal. On the other hand, when the inter-terminal voltage Vc is equal to or higher than the threshold voltage V ₀ (S5: NO), it is determined that the re-ignition capacitor 62 is not insufficiently charged even in this state, and without changing the frequency of the output control drive signal Proceed to step S7.

  Next, it is determined whether or not charging of the re-ignition capacitor 62 is completed (S7). Specifically, the terminal voltage Vc input from the voltage sensor 92 is acquired, and it is determined whether or not the terminal voltage Vc has reached the target voltage. When the charging is not completed (S7: NO), the process returns to step S7 and waits until the charging is completed. When the charging is completed (S7: YES), the frequency of the output control drive signal is restored (S8). In step S7, instead of determining whether or not the charging is completed, it may be determined whether or not the polarity is switched or whether or not the discharging is performed.

  Next, it is determined whether or not the elapsed time after the overcurrent is detected has passed the set time (S9). If the set time has not elapsed (S9: NO), it is determined whether or not the overcurrent has been eliminated (S10). Specifically, it is determined whether or not the overcurrent detection signal is no longer input from the overcurrent detection circuit 88. If the overcurrent has not been eliminated (S10: NO), the process returns to step S3, and steps S3 to S10 are repeated. In step S9, when the set time has elapsed (S9: YES), the generation of the output control drive signal is stopped and the current control switching process is terminated in order to prevent an adverse effect due to overcurrent. When the generation of the output control drive signal is stopped, the inverter circuit 2 is stopped and the output of the welding power supply device A1 is stopped. In step S10, when the overcurrent is eliminated (S10: YES), the control returns to PWM control (S11), and the process returns to step S1. Specifically, an output control drive signal generated by PWM control is output to the inverter circuit 2.

  The current control switching process shown in the flowchart of FIG. 5 is an example, and is not limited to the above.

  Next, the operation and effect of the welding power source apparatus A1 according to this embodiment will be described.

According to this embodiment, the current control unit 81 normally performs PWM control, but when an overcurrent detection signal is input from the overcurrent detection circuit 88, the current control unit 81 stops PWM control and performs overcurrent suppression control. . In the overcurrent suppression control, the current control unit 81 reduces and fixes the pulse width of the output control drive signal in the immediately preceding PWM control by a predetermined ratio (for example, half), and decreases the duty ratio. Is generated and output. The current control unit 81 compares the inter-terminal voltage Vc of the re-ignition capacitor 62 with the threshold voltage V ₀ when the timing signal is input from the timing detection unit 87. Then, when the inter-terminal voltage Vc is smaller than the threshold voltage V ₀ , the current control unit 81 determines that the charge amount of the re-ignition capacitor 62 is insufficient, and increases the frequency while maintaining the pulse width (for example, 1.. 5 times) Output control drive signal is generated and output. As a result, the waveform of the high-frequency voltage output from the inverter circuit 2 also changes in the same manner as the output control drive signal, and the output voltage of the rectifying / smoothing circuit 63c of the charging circuit 63 increases. Therefore, the charging speed of the re-ignition capacitor 62 is increased. Thereby, since it can charge so that the charge amount of the re-ignition capacitor | condenser 62 may not run short, generation | occurrence | production of arc interruption can be suppressed more.

  According to the present embodiment, the discharge circuit 64 controls the discharge based on the discharge circuit drive signal input from the discharge control unit 85. The discharge circuit drive signal (see FIG. 3C) is turned on when the switching drive signal (see FIG. 3A) is switched. After the switch is turned on, the polarity of the output current is changed. It turns off when the discharge time longer than the time elapses. Therefore, when the polarity of the output current of the welding power source device A1 changes, the discharge circuit drive signal is always on, so the discharge circuit 64 can appropriately apply the re-ignition voltage.

In this embodiment, when the inter-terminal voltage Vc is smaller than the threshold voltage V ₀ at the comparison timing, it is determined that the charge amount of the re-ignition capacitor 62 is insufficient. Is not limited to this. For example, it may be determined that the charge amount is insufficient when the duty ratio is smaller than a predetermined value at the comparison timing. Further, it may be determined that the amount of charge is insufficient when the duty ratio is smaller than a predetermined value regardless of the comparison timing. Further, when the pulse width becomes small due to overcurrent detection, it may be determined unconditionally (regardless of the duty ratio) that the amount of charge is insufficient.

  In the present embodiment, the case where the waveform of the output current is a substantially rectangular wave has been described (see FIG. 3B), but is not limited thereto. The waveform of the output current may be a sine wave. The waveform target setting unit 84 outputs a sine wave signal as the current waveform target value, and the polarity switching control unit 83 outputs the instantaneous value of the output current input from the current sensor 91 and the current waveform target value input from the waveform target setting unit 84. If the switching drive signal is generated based on the above, the waveform of the output current can be a sine wave. If the waveform of the output current is a sine wave, the generated arc becomes wider, so that the welding mark can be made wider. Moreover, the sound generated from welding power supply device A1 can be suppressed.

  In the present embodiment, the case where the re-ignition voltage is applied when the polarity of the output current of the welding power source device A1 changes has been described, but the present invention is not limited to this. Generally, the output terminal a (workpiece W) is positive and the output terminal b (welding torch B) is negative, so that the output terminal a (workpiece W) is negative and the output terminal b (welding torch) is positive. It is known that arc breaks tend to occur when B) switches to the reverse polarity, which is positive. Therefore, the re-ignition voltage may be applied only when switching from positive polarity to reverse polarity, and the re-ignition voltage may not be applied when switching from reverse polarity to positive polarity. In this case, the timing detection unit 87 may detect the comparison timing based on the timing at which the polarity is switched to the reverse polarity among the timing at which the polarity is switched. In this modified example, since the re-ignition voltage is applied when switching from the positive polarity to the reverse polarity, which is more likely to cause an arc break, the occurrence of an arc break can be suppressed. In addition, it is relatively difficult for arc breaks to occur, and re-ignition voltage is not applied when switching from reverse polarity to positive polarity, so re-ignition voltage is also applied when switching from reverse polarity to positive polarity. In comparison, the loss at the current limiting resistor 64b can be reduced. In addition, since the time from discharge of the re-ignition voltage to the next discharge becomes longer, it is possible to cope with the case where the polarity switching frequency becomes higher.

  When the re-ignition voltage is applied only when switching from positive polarity to reverse polarity as in the above modification, the re-ignition circuit 6 may be disposed on the output side of the inverter circuit 7. This case will be described below as a second embodiment.

  FIG. 6 is a block diagram showing a welding power source apparatus A2 according to the second embodiment, and shows the overall configuration of the welding system. In FIG. 6, the same or similar elements as those of the welding system according to the first embodiment (see FIG. 1) are denoted by the same reference numerals. In FIG. 6, the control circuit 8 is illustrated in a simplified manner. As shown in FIG. 6, the welding power supply device A2 is different from the welding power supply device A1 according to the first embodiment in that the re-ignition circuit 6 is arranged on the output side of the inverter circuit 7.

  In the welding power source device A2, the re-ignition circuit 6 is disposed on the output side of the inverter circuit 7, and re-points between the output terminals a and b so as to increase the potential of the output terminal b (welding torch B). An arc voltage is applied. The discharge circuit 64 is conductive when the switching drive signal (see FIG. 3A) is switched from ON to OFF (time t1 in FIG. 3), and the polarity of the output current (see FIG. 3B). Is changed (time t2 in FIG. 3), the re-ignition capacitor 62 is discharged, and a re-ignition voltage is applied between the output terminals a and b.

  In the second embodiment, the same effect as that of the first embodiment can be obtained.

  FIG. 7 shows an embodiment in which the power supply source to the charging circuit 63 is changed. Fig.7 (a) is a block diagram which shows welding power supply device A3 which concerns on 3rd Embodiment. In Fig.7 (a), the same code | symbol is attached | subjected to the element which is the same as that of the welding system which concerns on 1st Embodiment (refer FIG. 1), or similar. In FIG. 7A, the configuration downstream of the re-ignition circuit 6 and the description of the control circuit 8 are omitted (the same applies to FIGS. 7B and 7C). As shown in FIG. 7A, the welding power source A3 is different from the first embodiment in that each input terminal of the charging circuit 63 is connected to each output terminal of the secondary winding 3b of the transformer 3. It differs from welding power supply device A1 which concerns. In the third embodiment, the same effect as that of the first embodiment can be obtained. Further, according to the third embodiment, it is not necessary to provide the auxiliary winding 3c in the transformer 3. Therefore, a simpler configuration can be obtained.

  FIG. 7B is a block diagram showing a welding power source device A4 according to the fourth embodiment. In FIG.7 (b), the same code | symbol is attached | subjected to the element similar or similar to the welding system (refer FIG. 1) which concerns on 1st Embodiment. As shown in FIG. 7B, the welding power source device A4 includes a charging circuit 63 ′ instead of the charging circuit 63, and each input terminal of the charging circuit 63 ′ is connected to each output terminal of the rectifying circuit 4. It differs from welding power supply device A1 concerning a 1st embodiment by a point.

  The charging circuit 63 'is obtained by omitting the rectifying circuit from the rectifying / smoothing circuit 63c of the charging circuit 63 (see FIG. 2A). Since the output voltage of the rectifier circuit 4 is input to the charging circuit 63 ', no rectifier circuit is required. In the fourth embodiment, the same effect as that of the first embodiment can be obtained. Further, according to the fourth embodiment, the charging circuit 63 ′ can be configured simpler than the charging circuit 63.

  FIG.7 (c) is a block diagram which shows welding power supply device A5 which concerns on 5th Embodiment. In FIG.7 (c), the same code | symbol is attached | subjected to the element which is the same as that of the welding system which concerns on 1st Embodiment (refer FIG. 1), or similar. As shown in FIG.7 (c), welding power supply A5 is welding power supply A1 which concerns on 1st Embodiment by the point by which each input terminal of the charging circuit 63 is connected to each output terminal of the inverter circuit 2, respectively. And different. In the fifth embodiment, the same effect as that of the first embodiment can be obtained. Further, according to the fifth embodiment, it is not necessary to provide the auxiliary winding 3c in the transformer 3. Therefore, a simpler configuration can be obtained.

  In the first to fifth embodiments, the case where the pulse width of the output control drive signal is reduced as a countermeasure against overcurrent has been described. However, the present invention is not limited to this. The present invention can also be applied when the pulse width of the output control drive signal is reduced for other reasons. For example, when performing pulse current output, the target current setting unit 82 alternately sets a first target current and a second target current smaller than the first target current as the target current. In this case, when the target current is switched from the first target current to the second target current, the pulse width of the output control drive signal becomes small. Also, when the target current set by the target current setting unit 82 is small, the pulse width of the output control drive signal is small. Even in these cases, the same effects as those of the first embodiment can be obtained by applying the present invention.

  Moreover, although the said 1st thru | or 5th embodiment demonstrated the case where welding power supply device A1 thru | or A5 was used for the TIG welding system, it is not restricted to this. The welding power source apparatus according to the present invention can also be used for other semi-automatic welding systems. Moreover, the welding power supply apparatus which concerns on this invention can be used also for the fully automatic welding system by a robot, and can also be used for a covering arc welding system. Further, the present invention can be applied not only to a welding power supply device dedicated to AC output but also to a welding power supply device for both AC and DC.

  The welding power supply device according to the present invention is not limited to the above-described embodiment. The specific configuration of each part of the welding power source apparatus according to the present invention can be varied in design in various ways.

A1, A2, A3, A4, A5: Welding power supply device 1: Rectification smoothing circuit 2: Inverter circuit (first inverter circuit)
3: Transformer 3a: Primary winding 3b: Secondary winding 3c: Auxiliary winding 4: Rectifier circuit 5: DC reactor 6: Re-ignition circuit 61: Diode 62: Re-ignition capacitors 63, 63 ': Charging Circuit 63a: Drive circuit 63b: Switching element 63c: Rectification smoothing circuit 63d: Insulated forward converter 64: Discharge circuit 64a: Switching element 64b: Current limiting resistor 7: Inverter circuit (second inverter circuit)
8: Control circuit 81: Current control unit 82: Target current setting unit 83: Polarity switching control unit 84: Waveform target setting unit 85: Discharge control unit 86: Charge control unit 87: Timing detection unit 88: Overcurrent detection circuit 91: Current sensor 92: Voltage sensor a, b: Output terminal B: Welding torch D: Commercial power supply W: Workpiece

Claims (8)

A first inverter circuit for controlling the output;
A rectifying circuit for rectifying high-frequency power output from the first inverter circuit;
A second inverter circuit that converts the DC power output from the rectifier circuit to AC power and outputs the AC power to the welding load;
A re-ignition circuit that applies a re-ignition voltage to the output to the welding load when the polarity of the output current of the second inverter circuit switches;
A control circuit for outputting an output control drive signal for driving the first inverter circuit;
With
The re-ignition circuit charges a part of the output power of the first inverter circuit to apply the re-ignition voltage;
When it is determined that the charge amount of the re-ignition circuit is insufficient due to a decrease in the duty ratio of the output control drive signal, the control circuit increases the frequency without changing the pulse width of the output control drive signal. To
A welding power supply device characterized by that. The re-ignition circuit is
A re-ignition capacitor charged with the re-ignition voltage;
A voltage sensor for detecting a voltage between terminals of the re-ignition capacitor;
With
The control circuit determines that the amount of charge is insufficient when the voltage between the terminals is smaller than a threshold voltage at a predetermined timing based on the timing at which the polarity of the output current of the second inverter circuit switches.
The welding power supply device according to claim 1. The control circuit determines that the charge amount is insufficient when the duty ratio is equal to or less than a predetermined value at a predetermined timing based on a timing at which the polarity of the output current of the second inverter circuit is switched.
The welding power supply device according to claim 1. The control circuit restores the frequency of the output control drive signal when the re-ignition voltage can be charged to the target voltage after increasing the frequency of the output control drive signal.
The welding power supply device according to any one of claims 1 to 3. An overcurrent detection circuit for detecting an overcurrent of the output current of the second inverter circuit;
The control circuit reduces a pulse width of the output control drive signal when the overcurrent detection circuit detects an overcurrent;
The welding power supply device according to any one of claims 1 to 4. The control circuit includes:
A target current setting unit that alternately sets a first target current and a second target current smaller than the first target current as a target current;
A current control unit that generates the output control drive signal based on the target current and a detected value of the output current of the second inverter circuit;
With
When the target current is switched from the first target current to the second target current, the pulse width of the output control drive signal is reduced.
The welding power supply device according to any one of claims 1 to 5. The control circuit increases the frequency at a rate corresponding to a reduction rate of the pulse width of the output control drive signal;
The welding power supply device according to claim 5 or 6. The control circuit includes:
When the remaining time until the timing at which the polarity of the output current of the second inverter circuit is switched is T, the reduction rate of the pulse width is W, and the predetermined coefficient is α, the rate F for increasing the frequency is:
F = α / (W · T)
Calculate as
The welding power supply device according to claim 5 or 6.

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