JP2018187645A - Welding power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a welding power supply device capable of restraining the occurrence of an arc shortage.SOLUTION: A welding power supply device A1 comprises a voltage superimposing circuit 6 for superimposing reignition voltage on an output to a welding load when the polarity of an output current of an inverter circuit 7 changes. The voltage superimposing circuit 6 comprises a reignition capacitor 62 which is charged with the reignition voltage, a charging circuit 63 for charging the reignition capacitor 62 with the reignition voltage, and a discharging circuit 64 for discharging the reignition voltage charged in the reignition capacitor 62. A target voltage of the reignition voltage is variable, and the charging circuit 63 executes charging until the reignition voltage reaches the target voltage.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. 10 is a diagram illustrating an example of a welding system provided with a conventional welding power source device. The welding system shown in FIG. 10 includes a welding torch B and a welding power source device A100 that supplies electric power to the welding torch B. The welding power supply device A100 converts AC power from the commercial power source D into DC power, inputs the DC power to the inverter circuit 7, converts the AC power into AC power by the inverter circuit 7, and outputs the AC power. The voltage superimposing circuit 600 superimposes the re-ignition voltage when the polarity of the output current of the inverter circuit 7 is switched. The voltage superimposing circuit 600 includes a re-ignition capacitor 62, a charging circuit 63, and a discharging circuit 64. The charging circuit 63 charges the re-ignition capacitor 62 to a predetermined voltage. The discharge circuit 64 discharges the re-ignition voltage charged in the re-ignition capacitor 62 and superimposes it on the output of the inverter circuit 7. Charging circuit 63 and discharging circuit 64 are controlled by control circuit 800. In welding power supply device A100, since the re-ignition voltage is superimposed when the polarity of the output current of inverter circuit 7 switches, the occurrence of arc interruption is suppressed.

Japanese Patent Laid-Open No. 06-91369

  However, in the welding power source apparatus A100, there is a case where there is a difference in the effect of suppressing the arc break depending on the use environment or use state. For example, when the output current is small, the effect of suppressing arc breakage is small, and arc breakage may occur. Further, depending on the material and thickness of the workpiece W, the type and flow rate of the welding gas used during welding, the type of the welding torch B, and the like, the effect of suppressing arc breakage may be small.

  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 apparatus provided by the first aspect of the present invention includes: an inverter circuit that converts DC power to AC power and outputs the AC power to a welding load; and the polarity of the output current of the inverter circuit is switched. A voltage superimposing circuit for superimposing a re-ignition voltage on an output to a load, the voltage superimposing circuit being charged with the re-ignition voltage; and A charging circuit for charging an ignition voltage; and a discharge circuit for discharging the re-ignition voltage charged in the re-ignition capacitor, wherein a target voltage of the re-ignition voltage is variable, and the charging The circuit is charged until the re-ignition voltage reaches the target voltage. According to this configuration, the charging circuit performs charging until the re-ignition voltage reaches the target voltage. The target voltage is variable and can be changed according to the use environment and use state of the welding power supply device. In a situation where the effect of suppressing the arc break is small, the superimposed re-ignition voltage can be increased by increasing the target voltage and increasing the re-ignition voltage charged in the re-ignition capacitor. Thereby, generation | occurrence | production of an arc break can be suppressed more.

  In a preferred embodiment of the present invention, the welding power supply device further includes a control circuit that controls the output current of the inverter circuit to a target current, and the control circuit corresponds to the target current. A target voltage setting unit for setting the target voltage is provided. According to this configuration, the target voltage corresponding to the target current can be set. By setting the target voltage to be higher as the target current is smaller, when the target current is smaller and the output current is smaller, a higher re-ignition voltage can be charged and discharged.

  In a preferred embodiment of the present invention, the welding power supply device further includes a control circuit that controls the output current of the inverter circuit to a target current, and the control circuit corresponds to the output current. A target voltage setting unit for setting the target voltage is provided. According to this configuration, the target voltage corresponding to the output current can be set. By setting the target voltage to be higher as the output current becomes smaller, a higher re-ignition voltage can be charged and discharged when the output current is smaller.

  In a preferred embodiment of the present invention, the control circuit includes a discharge time setting unit that sets a corresponding discharge time according to the target current or the output current, and the discharge circuit is set The re-ignition voltage is discharged during the discharge time. According to this configuration, the discharge time can be changed according to the target current or the output current. By setting the discharge time to be longer as the target current or the output current is smaller, the re-ignition voltage can be discharged for a longer time when the output current is smaller. Therefore, the occurrence of arc break can be further suppressed.

  In a preferred embodiment of the present invention, the welding power source apparatus further includes a detection unit that detects an arc break and a target voltage change unit that increases the target voltage when the detection unit detects an arc break. ing. According to this configuration, the target voltage can be increased when an arc break occurs. Thereby, the tolerance with respect to an arc break can be improved automatically.

  In a preferred embodiment of the present invention, the detection unit includes a current sensor that detects an output current of the inverter circuit, and detects an arc break based on a current value detected by the current sensor. According to this configuration, it is possible to appropriately detect an arc break.

  In a preferred embodiment of the present invention, the voltage superimposing circuit superimposes the re-ignition voltage only when the current output to the workpiece of the welding load is switched from positive to negative. According to this configuration, it is possible to superimpose a re-ignition voltage when an arc break is more likely to occur, so that the occurrence of an arc break can be suppressed. Furthermore, when the arc break is relatively difficult to occur, the re-ignition voltage is not superimposed, so that power loss can be reduced.

  In a preferred embodiment of the present invention, the voltage superimposing circuit superimposes when the current output to the workpiece of the welding load is switched from positive to negative and when the current is switched from negative to positive. Different re-ignition voltages. According to this configuration, it is possible to suppress the occurrence of arc break by increasing the re-ignition voltage superimposed when arc break is more likely to occur. Furthermore, the loss of power can be reduced by reducing the re-ignition voltage that is superimposed when it is relatively difficult for the arc break to occur.

  According to the present invention, the charging circuit charges until the re-ignition voltage reaches the target voltage. The target voltage is variable and can be changed according to the use environment and use state of the welding power supply device. In a situation where the effect of suppressing the arc break is small, the superimposed re-ignition voltage can be increased by increasing the target voltage and increasing the re-ignition voltage charged in the re-ignition capacitor. Thereby, generation | occurrence | production of an arc break 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 which shows the waveform of each signal of the welding power supply device concerning a 1st embodiment. It is a flowchart which shows the production | generation process of the charging circuit drive signal which the charge control part which concerns on 1st Embodiment performs. It is a time chart which shows the waveform of each signal in the modification of the discharge control part which concerns on 1st Embodiment. 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 control circuit of the welding power supply apparatus which concerns on 3rd and 4th embodiment. (A) is a block diagram which shows the control circuit of the welding power supply device which concerns on 5th Embodiment, (b) is a flowchart which shows the production | generation process of a charging circuit drive signal. It is a time chart which shows the waveform of each signal of the welding power supply device concerning a 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.

  1-3 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 showing waveforms of respective signals of the welding power source apparatus A1. 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 voltage superimposing circuit 6, an inverter circuit 7, a control circuit 8, a current sensor 91, and a voltage sensor 92. Yes.

  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 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 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 side winding and a secondary side winding. Each input terminal of the primary winding is connected to each output terminal of the inverter circuit 2. Each output terminal of the secondary winding 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 and the secondary side winding and is input to the rectifier circuit 4. Since the secondary side winding is insulated from the primary side winding, it is possible to prevent the current input from the commercial power source D from flowing into the secondary side circuit.

  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 “inverter circuit” of the present invention.

  The voltage superimposing circuit 6 is arranged between the rectifying circuit 4 and the inverter circuit 7 and when the polarity of the output current of the inverter circuit 7 is switched, a high voltage is applied between the output terminals a and b of the welding power source device A1. Is superimposed. 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 voltage superimposing 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 superimposed on 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 an insulated forward converter. The charging circuit 63 includes a drive circuit 63a for driving the isolated forward converter. 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 boost chopper circuit or the like instead of the insulated forward converter.

  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). As a result, the re-ignition voltage charged in the re-ignition capacitor 62 is discharged and is superimposed on the output voltage of the rectifier circuit 4 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. 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 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 target voltage setting 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 based on the effective value and the target current (effective value) input from the target current setting unit 82, the inverter A drive signal for controlling the switching element of the circuit 2 is generated and output to the inverter circuit 2.

  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 the re-ignition voltage can be superimposed 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 target voltage setting unit 87 sets the target voltage of the re-ignition voltage that charges the re-ignition capacitor in the charge control unit 86. The target voltage setting unit 87 sets a target voltage according to the target current input from the target current setting unit 82 (current effective value that is a control target of the output current of the inverter circuit 2). The target voltage setting unit 87 stores a correspondence relationship between the target current and the target voltage as a table, and sets a target voltage corresponding to the input target current. For example, the target voltage setting unit 87 sets the target voltage to 300 V when the target current is 200 A, and sets the target voltage to 350 V when the target current is 50 A. Note that these values are merely examples and are not limited. In general, when the target current becomes small, the output current becomes small. Therefore, even if the same re-ignition voltage is superimposed when the polarity changes, there is a high possibility that an arc break will occur. Accordingly, the target voltage of the re-ignition voltage is set higher as the target current becomes smaller. The target voltage may be associated with each target current that can be input, or may be associated with each target current within a predetermined range. In the present embodiment, the target voltage is set based on the correspondence stored in the table, but the present invention is not limited to this. For example, an arithmetic expression may be set, and the target voltage may be calculated and set from the input target current. For example, when an arithmetic expression suitable for the above example is expressed by a linear simple arithmetic expression, if the input target current is I ₀ , the target voltage is expressed as V ₀ = (− 1/3) I ₀ +1100/3. be able to.

  The charging control unit 86 controls the charging circuit 63. The charge control unit 86 is input from the discharge circuit drive signal input from the discharge control unit 85, the instantaneous value of the voltage across the re-ignition capacitor 62 input from the voltage sensor 92, and the target voltage setting unit 87. Based on the target voltage, a charging circuit drive signal for controlling the charging circuit 63 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 is switched on when the discharge drive signal input from the discharge control unit 85 is switched from on to off (time t3, t7 in FIG. 3), and the re-ignition capacitor When the inter-terminal voltage 62 becomes the target voltage (time t4, t8 in FIG. 3), a pulse signal that turns off is generated and output as a charging circuit drive signal (see FIG. 3D).

  In the present embodiment, the target voltage is variable and is set by the target voltage setting unit 87. FIG. 3 shows a case where 300 V is set as the target voltage during the period when the target current is set to 200 A, and 350 V is set as the target voltage during the period where the target current is set to 50 A. Yes. During the period in which the target current is set to 200 A, the charging circuit drive signal is turned on (time t3 in FIG. 3), charging of the re-ignition capacitor 62 is started, and the voltage across the terminals of the re-ignition capacitor 62 is When the target voltage reaches 300 V (time t4), the charging circuit drive signal is turned off and charging is stopped. Further, during the period in which the target current is set to 50 A, the charging circuit drive signal is turned on (time t13 in FIG. 3), charging of the re-ignition capacitor 62 is started, and between the terminals of the re-ignition capacitor 62 When the voltage reaches 350 V, which is the target voltage (time t14), the charging circuit drive signal is turned off and charging is stopped. In this way, the charging control unit 86 controls the charging circuit 63 so that charging is performed until the voltage between the terminals of the re-ignition capacitor 62 reaches the target voltage set by the target voltage setting unit 87.

  Next, the processing procedure of the generation process of the charging circuit drive signal will be described with reference to the flowchart shown in FIG.

  FIG. 4 is a flowchart showing a charging circuit drive signal generation process performed by the charging control unit 86. The process is started when the inverter circuit 7 is started for welding, and is ended when the inverter circuit 7 is stopped.

  First, the target voltage Vref of the re-ignition voltage is set (S1). Specifically, the target voltage setting unit 87 inputs the target voltage Vref determined based on the target current of the output current of the inverter circuit 2 to the charging control unit 86. Next, an off signal (low level signal) of the charging circuit drive signal is generated and output to the charging circuit 63 (S2). Then, it is determined whether or not the fall of the discharge circuit drive signal is detected (S3). Specifically, it is determined whether or not the discharge circuit drive signal input from the discharge controller 85 has been switched from on to off. When the falling is detected (S3: YES), the process proceeds to step S4. If not detected (S3: NO), the process returns to step S2. That is, step S2 is performed until a falling edge is detected, and a charging circuit drive signal that is an off signal is generated and output.

  Next, an on signal (high level signal) of the charging circuit driving signal is generated and output to the charging circuit 63 (S4). Then, it is determined whether or not the inter-terminal voltage Vc of the re-ignition capacitor 62 is smaller than the target voltage Vref (S5). Specifically, the terminal voltage Vc input from the voltage sensor 92 is compared with the set target voltage Vref, and it is determined whether or not the terminal voltage Vc is smaller than the target voltage Vref. If the inter-terminal voltage Vc is smaller than the target voltage Vref (S5: YES), the process returns to step S4. That is, step S4 is performed until the inter-terminal voltage Vc reaches the target voltage Vref, and a charging circuit drive signal that is an ON signal is generated and output. When the inter-terminal voltage Vc is equal to or higher than the target voltage Vref (S5: NO), the process returns to step S1. Thus, a charging circuit driving signal for one cycle is generated. Then, the target voltage Vref is reset and a charging circuit driving signal for the next one cycle is generated.

  The generation process of the charging circuit drive signal shown in the flowchart of FIG. 4 is an example, and is not limited to the above-described process.

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

  According to the present embodiment, the target voltage setting unit 87 sets the target voltage corresponding to the target current (current effective value that is the control target of the output current of the inverter circuit 2) input from the target current setting unit 82 to the charge control unit. Set to 86. The charging control unit 86 controls the charging circuit 63 to charge so that charging is performed until the voltage between the terminals of the re-ignition capacitor 62 reaches the target voltage set by the target voltage setting unit 87. Since the target voltage is set to be higher as the target current is smaller, when the target current is smaller and the output current is smaller, a higher re-ignition voltage can be charged and discharged. Thereby, generation | occurrence | production of an arc break 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 superimpose the re-ignition voltage.

  In the present embodiment, the case where the waveform of the output current is a substantially rectangular wave (see FIG. 3B) has been described, but the present invention is not limited to this. 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.

  Moreover, although this embodiment demonstrated the case where a re-ignition voltage was superimposed when the polarity of the output current of welding power supply device A1 changed, it is not restricted 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 superimposed only when switching from positive polarity to reverse polarity, and the re-ignition voltage may not be superimposed when switching from reverse polarity to positive polarity. A modification in this case will be described with reference to FIG. In this modification, only the method of generating the discharge circuit drive signal by the discharge control unit 85 is changed.

  FIG. 5 is a time chart showing the waveform of each signal in the modification. FIG. 5A shows a switching drive signal generated by the polarity switching control unit 83, which is the same as that shown in FIG. FIG.5 (b) has shown the output current of welding power supply device A1, and is the same as what is shown in FIG.3 (b). FIG. 5C shows a discharge circuit drive signal generated by the discharge control unit 85. FIG. 5D shows a charging circuit drive signal generated by the charging control unit 86. FIG. 5E shows the voltage between the terminals of the re-ignition capacitor 62.

  The discharge control unit 85 according to the modified example generates the discharge circuit drive signal so that it is turned on when the polarity of the output current of the welding power source device A1 changes from positive polarity to reverse polarity. Specifically, the discharge control unit 85 switches on when the switching drive signal (see FIG. 5A) switches from on to off (time t1, t11 in FIG. 5), and switches on. After that, when a discharge time has elapsed (time t3, t13 in FIG. 5), a pulse signal that is turned off is generated and output as a discharge circuit drive signal (see FIG. 5C). The discharge controller 85 switches the switching drive signal from OFF to ON (time t5, t15 in FIG. 5) and when the discharge time has elapsed after switching to OFF (time t7 in FIG. 5). At t17), the discharge circuit drive signal is not switched.

  Since the discharge circuit drive signal generated by the discharge controller 85 (see FIG. 5C) is different from the discharge drive signal shown in FIG. 3C, the charge circuit drive signal generated by the charge controller 86 (FIG. 5D )) And the voltage between terminals of the re-ignition capacitor 62 (see FIG. 5E) have waveforms different from those shown in FIGS. 3D and 3E, respectively.

  In the modified example, the arc break is more likely to occur, and the re-ignition voltage is superimposed when switching from the positive polarity to the reverse polarity. Therefore, the occurrence of the arc break can be suppressed. In addition, it is relatively difficult for arc breaks to occur, and re-ignition voltage is not superimposed when switching from reverse polarity to positive polarity. Therefore, re-ignition voltage is also superimposed 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. For example, even if the polarity switching frequency in the case shown in FIG. 5 is doubled, the battery can be charged up to the target voltage before discharging.

  Further, when switching from reverse polarity to positive polarity, a lower re-ignition voltage may be superimposed than when switching from positive polarity to reverse polarity. That is, when the target voltage setting unit 87 switches from the positive polarity to the reverse polarity according to the target current input from the target current setting unit 82, the target voltage setting unit 87 switches from the reverse polarity to the positive polarity. A second target voltage (<first target voltage) may be set. Then, the charge control unit 86 charges the re-ignition voltage for discharging when switching from the positive polarity to the reverse polarity until the voltage between the terminals of the re-ignition capacitor 62 becomes the first target voltage. The charging circuit 63 is controlled so as to charge the re-ignition voltage for discharging when switching from positive to negative until the voltage across the terminals of the re-ignition capacitor 62 reaches the second target voltage. Even in this case, the loss in the current limiting resistor 64b can be reduced. In addition, without providing the target voltage setting unit 87, a first target voltage when switching from positive polarity to reverse polarity, and a second target voltage (<first target voltage) when switching from reverse polarity to positive polarity May be set as a fixed value.

  When the re-ignition voltage is superimposed only when switching from positive polarity to reverse polarity as in the above modification, the voltage superimposing 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 voltage superimposing circuit 6 is arranged on the output side of the inverter circuit 7.

  In the welding power source device A2, the voltage superimposing circuit 6 is disposed on the output side of the inverter circuit 7, and is re-ignited between the output terminals a and b so as to increase the potential of the output terminal b (welding torch B). The voltage is superimposed. The discharge circuit 64 is conductive when the switching drive signal (see FIG. 5A) is switched from ON to OFF (time t1 in FIG. 5), and the polarity of the output current (see FIG. 5B). Is changed (time t2 in FIG. 5), the re-ignition capacitor 62 is discharged, and the re-ignition voltage is superimposed between the output terminals a and b.

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

  FIG. 7A is a diagram showing a welding power source device A3 according to the third embodiment, and is a block diagram showing the control circuit 8. As shown in FIG. In FIG. 7A, the same or similar elements as those of the control circuit 8 according to the first embodiment (see FIG. 1) are denoted by the same reference numerals. In FIG. 7A, the description of the configuration other than the control circuit 8 is omitted (the same applies to FIGS. 7B and 8A). As shown in FIG. 7A, the welding power source device A3 is related to the first embodiment in that the target voltage setting unit 87 sets the target voltage according to the output current, not the target current of the output current. Different from welding power supply device A1.

  The target voltage setting unit 87 according to the third embodiment receives the instantaneous value of the output current detected by the current sensor 91 and calculates an effective value. Then, the target voltage is set according to the effective value. The target voltage setting unit 87 stores a correspondence table that is set such that the target voltage increases as the effective value of the output current decreases, and sets the target voltage corresponding to the calculated effective value of the output current. To do.

  According to the third embodiment, the target voltage setting unit 87 sets the target voltage corresponding to the actual effective value of the output current in the charging control unit 86. Since the target voltage is set higher as the output current becomes smaller, when the output current becomes smaller, a higher re-ignition voltage can be charged and discharged. Therefore, the same effect as that of the first embodiment can be obtained.

  FIG. 7B is a diagram showing a welding power source device A4 according to the fourth embodiment, and is a block diagram showing the control circuit 8. As shown in FIG. 7B, the same or similar elements as those of the control circuit 8 (see FIG. 1) according to the first embodiment are denoted by the same reference numerals. As shown in FIG. 7 (b), the welding power supply device A4 includes a discharge time setting unit 88, and is different from the welding power supply device A1 according to the first embodiment in that the discharge time is changed according to the target current. Different. The discharge control unit 85 according to the first embodiment sets the discharge time to a fixed predetermined time. In the discharge control unit 85 according to the fourth embodiment, the discharge time is set by the discharge time setting unit 88.

  The discharge time setting unit 88 sets the discharge time in the discharge control unit 85. The discharge time setting unit 88 sets the discharge time according to the target current input from the target current setting unit 82 (current effective value that is a control target of the output current of the inverter circuit 2). The discharge time setting unit 88 stores a correspondence relationship between the target current and the discharge time as a table, and sets the discharge time corresponding to the input target current based on the table. For example, the discharge time setting unit 88 sets the discharge time to 300 ms when the target current is 200 A, and sets the discharge time to 350 ms when the target current is 50 A. Note that these values are merely examples and are not limited. In the present embodiment, the discharge time is set longer as the target current becomes smaller. The discharge time may be associated with each target current that can be input, or may be associated with each target current within a predetermined range. Moreover, in this embodiment, although discharge time is set based on the correspondence memorize | stored in the table, it is not restricted to this. For example, an arithmetic expression may be set and the discharge time may be calculated and set from the input target current.

  The discharge control unit 85 according to the fourth embodiment is turned on when the switching drive signal is switched, and is turned off when the discharge time set by the discharge time setting unit 88 has elapsed after being switched on. Is generated and output as a discharge circuit drive signal. The discharge circuit 64 receives a discharge circuit drive signal from the discharge controller 85, and discharges while the discharge circuit drive signal is on. Therefore, the discharge circuit 64 discharges for the set discharge time. That is, the discharge is performed for a longer time as the output current becomes smaller.

  In the fourth embodiment, the same effect as that of the first embodiment can be obtained. In the fourth embodiment, the re-ignition voltage can be discharged for a longer time as the output current becomes smaller. Therefore, the occurrence of arc break can be further suppressed. Note that the discharge time setting unit 88 may set the discharge time according to the output current instead of the target current of the output current. That is, the discharge time setting unit 88 receives the instantaneous value of the output current detected by the current sensor 91, calculates the effective value, and the discharge time setting unit 88 is set to increase the discharge time as the effective value of the output current decreases. A discharge time corresponding to the calculated effective value may be set based on the relationship table.

  8 and 9 are diagrams for explaining a welding power source device A5 according to the fifth embodiment. FIG. 8A is a block diagram showing the control circuit 8 of the welding power source device A5. In FIG. 8A, the same or similar elements as those of the control circuit 8 (see FIG. 1) according to the first embodiment are denoted by the same reference numerals. FIG. 8B is a flowchart showing a charging circuit drive signal generation process performed by the charging control unit 86 according to the fifth embodiment. FIG. 9 is a time chart showing waveforms of signals of the welding power source device A5. As shown in FIG. 8 (a), the welding power source device A5 includes an arc break detection unit 89, and the welding power source device according to the first embodiment is configured to increase the target voltage when arc break is detected. Different from A1. In the charging control unit 86 according to the first embodiment, the target voltage is set by the target voltage setting unit 87, but the charging control unit 86 according to the fifth embodiment sets the initial value fixed as the first target voltage. When the arc break detector 89 detects an arc break, the target voltage is increased.

  The arc break detecting unit 89 detects that an arc break has occurred. The arc break detector 89 receives the instantaneous value of the output current detected by the current sensor 91. When the arc break occurs, the output current continues to be “0” (see the circled portion in FIG. 9B). The arc break detector 89 determines that an arc break has occurred when the instantaneous value of the output current detected by the current sensor 91 continues to be “0”, and sends a detection signal to the charge controller 86. Output. The arc break detecting unit 89 may detect that an arc break has occurred based on the output voltage instead of the output current. In this case, an inter-terminal voltage between the output terminal a and the output terminal b is detected by a voltage sensor (not shown). When an arc break occurs, a re-ignition voltage is applied to the output voltage. Therefore, the arc break detection unit 89 determines that an arc break has occurred when the voltage between the terminals detected by the voltage sensor exceeds a threshold value for distinguishing between the load voltage and the re-ignition voltage. The signal is output to the charging control unit 86. It should be noted that arc break detection based on the output current and arc break detection based on the output voltage may be performed, and if both are detected, it may be determined that an arc break has occurred, either of which has been detected. In this case, it may be determined that an arc break has occurred.

  The charge control unit 86 according to the fifth embodiment includes a discharge circuit drive signal input from the discharge control unit 85, an instantaneous value of the voltage across the re-ignition capacitor 62 input from the voltage sensor 92, and arc break detection. Based on the detection signal input from the unit 89, a charging circuit drive signal is generated and output to the charging circuit 63. A predetermined initial value is preset for the target voltage. When the detection signal is input from the arc break detector 89, the charging controller 86 increases the set target voltage value by a predetermined value ΔV. As the predetermined value ΔV, for example, a value of 10% of the initial value of the target voltage is set. For example, when the initial value of the target voltage is 300 V, the charging control unit 86 increases the target voltage to 330 V when the first detection signal is input, and when the second detection signal is input, Increase the target voltage to 360V. The predetermined value ΔV may be a fixed value (for example, 30 V) regardless of the initial target voltage. Further, it may be increased by a predetermined ratio (for example, 10%). In the present embodiment, the charging control unit 86 corresponds to the “target voltage changing unit” of the present invention.

  FIG. 8B is a flowchart showing a charging circuit drive signal generation process performed by the charging control unit 86 according to the fifth embodiment. The process is started when the inverter circuit 7 is started for welding, and is ended when the inverter circuit 7 is stopped.

  First, an off signal (low level signal) of the charging circuit drive signal is generated and output to the charging circuit 63 (S11). And it is discriminate | determined whether the fall of the discharge circuit drive signal was detected (S12). Specifically, it is determined whether or not the discharge circuit drive signal input from the discharge controller 85 has been switched from on to off. When the falling is detected (S12: YES), the process proceeds to step S13. When not detected (S12: NO), it returns to step S11. That is, step S11 is performed until a falling edge is detected, and a charging circuit drive signal that is an off signal is generated and output.

  Next, it is determined whether or not an arc break has been detected (S13). Specifically, it is determined whether or not a detection signal is input from the arc break detection unit 89. When the arc break is detected (S13: YES), the predetermined value ΔV is added to the target voltage Vref (S14), and the process proceeds to step S15. If no arc break is detected (S13: NO), the process proceeds to step S15.

  Next, an on signal (high level signal) of the charging circuit drive signal is generated and output to the charging circuit 63 (S15). Then, it is determined whether or not the inter-terminal voltage Vc of the re-ignition capacitor 62 is smaller than the target voltage Vref (S16). Specifically, the inter-terminal voltage Vc input from the voltage sensor 92 is compared with the target voltage Vref, and it is determined whether or not the inter-terminal voltage Vc is smaller than the target voltage Vref. When the inter-terminal voltage Vc is smaller than the target voltage Vref (S16: YES), the process returns to step S15. That is, step S15 is performed until the inter-terminal voltage Vc reaches the target voltage Vref, and a charging circuit drive signal that is an ON signal is generated and output. When the inter-terminal voltage Vc is equal to or higher than the target voltage Vref (S16: NO), the process returns to step S11. Thus, a charging circuit driving signal for one cycle is generated.

  The generation process of the charging circuit drive signal shown in the flowchart of FIG. 8B is an example, and is not limited to the above.

  FIG. 9 is a time chart showing waveforms of signals of the welding power source device A5. FIG. 9A shows a switching drive signal generated by the polarity switching control unit 83, which is the same as that shown in FIG. FIG.9 (b) has shown the output current of welding power supply device A1, and is the same as what is shown in FIG.3 (b). FIG. 9C shows a discharge circuit drive signal generated by the discharge control unit 85. FIG. 9D shows a charging circuit drive signal generated by the charging control unit 86. FIG. 9E shows the voltage between the terminals of the re-ignition capacitor 62.

  In the time chart shown in FIG. 9, since the instantaneous value of the output current continues to be “0”, an arc break is detected at time tx (see the circled portion in FIG. 9B). Then, the target voltage Vref is increased by a predetermined value ΔV. Therefore, after that, charging is performed until the voltage between the terminals of the re-ignition capacitor 62 reaches the increased target voltage Vref. Since the re-ignition voltage charged in the re-ignition capacitor 62 is not discharged when the arc is cut off, the voltage between the terminals of the re-ignition capacitor 62 at time tx does not decrease (see FIG. 9 (e)). Therefore, the next charging is completed in a short time (see FIG. 9D). After the target voltage Vref is increased, the re-ignition voltage that is superimposed when the polarity changes increases, so that no arc break occurs.

  In the fifth embodiment, when the arc break detecting unit 89 detects an arc break, the target voltage of the terminal voltage of the re-ignition capacitor 62 is increased. Therefore, since the re-ignition voltage superimposed when the polarity changes is increased, arc breakage is less likely to occur. In the fifth embodiment, by increasing the target voltage every time an arc break occurs, an optimum target voltage can be set according to the use environment and use state, and the resistance to arc break can be automatically improved. it can.

  In order to prevent the target voltage from becoming too high, if the arc break does not occur until a predetermined time elapses after the target voltage is increased, the target voltage is returned to the value before the target voltage is increased. You may do it. Further, instead of returning to the original value, only half of the increase may be returned. In the present embodiment, the initial value of the target voltage is a fixed value, but the present invention is not limited to this. The target voltage setting unit 87 according to the first embodiment may be provided so that the target voltage setting unit 87 sets an initial value of the target voltage.

  In the first to fifth embodiments, the case where the welding power supply devices A1 to A5 are used in the TIG welding system has been described. However, the present invention is not limited 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.

  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 3: Transformer 4: Rectification circuit 5: DC reactor 6: Voltage superposition circuit 61: Diode 62: Re-ignition capacitor 63: Charging Circuit 63a: Drive circuit 63b: Switching element 64: Discharge circuit 64a: Switching element 64b: Current limiting resistor 7: 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: Target voltage setting unit 88: Discharge time setting unit 89: Arc break detection unit 91: Current sensor 92: Voltage sensor a, b: Output terminal B: Welding torch D : Commercial power supply W: Workpiece

Claims (8)

An inverter circuit that converts DC power into AC power and outputs it to the welding load;
A voltage superimposing circuit for superimposing a re-ignition voltage on the output to the welding load when the polarity of the output current of the inverter circuit is switched;
With
The voltage superimposing circuit is
A re-ignition capacitor charged with the re-ignition voltage;
A charging circuit for charging the re-ignition capacitor with the re-ignition voltage;
A discharge circuit for discharging the re-ignition voltage charged in the re-ignition capacitor;
With
The target voltage of the re-ignition voltage is variable,
The charging circuit performs charging until the re-ignition voltage reaches the target voltage.
A welding power supply device characterized by that. A control circuit for controlling the output current of the inverter circuit to a target current;
The control circuit includes a target voltage setting unit that sets the corresponding target voltage according to the target current.
The welding power supply device according to claim 1. A control circuit for controlling the output current of the inverter circuit to a target current;
The control circuit includes a target voltage setting unit that sets the corresponding target voltage according to the output current.
The welding power supply device according to claim 1. The control circuit includes a discharge time setting unit that sets a corresponding discharge time according to the target current or the output current,
The discharge circuit discharges the re-ignition voltage during the set discharge time;
The welding power supply device according to claim 2 or 3. A detector for detecting an arc break;
When the detection unit detects an arc break, a target voltage changing unit that increases the target voltage;
Further equipped with,
The welding power supply device according to any one of claims 1 to 4. The detector is
A current sensor for detecting an output current of the inverter circuit;
Based on the current value detected by the current sensor, arc breakage is detected.
The welding power supply device according to claim 5. The voltage superimposing circuit superimposes the re-ignition voltage only when the current to be output to the workpiece of the welding load is switched from positive to negative.
The welding power supply device according to any one of claims 1 to 6. The voltage superimposing circuit varies the re-ignition voltage to be superimposed when the current output to the workpiece of the welding load is switched from positive to negative and when the current is switched from negative to positive.
The welding power supply device according to any one of claims 1 to 6.

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