Control circuit and control device for preventing welding machine from generating impact current
By combining welding current feedback and arc ignition current control unit, the problem of impact current at the moment of arc ignition of the welding machine is solved, the current is increased slowly, the welding quality is improved and the wear of tungsten needle is reduced.
Patent Information
- Application Number
- CN202520590986.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2025-03-31
- Publication Date
- 2026-02-24
- Estimated Expiration
- 2035-03-31
AI Technical Summary
Existing welding machines generate an inrush current at the moment of arc initiation, which causes the tungsten needle to burn out, spatter, perforation of thin workpieces, and grooves to form on thick workpieces during arc initiation, affecting welding quality. Furthermore, the frequent replacement of tungsten needles results in a waste of labor and materials.
The welding current feedback unit determines the working status of the welding machine. The arc ignition current control unit gradually increases the given value of the PI circuit to the given voltage of the potentiometer at the moment of arc ignition. Combined with the PI voltage control unit, the welding machine is clamped to 9.7V when it is unloaded to prevent the generation of inrush current.
It effectively controls the gradual increase of arc-starting current, avoids the generation of inrush current, improves welding quality, and reduces the wear and replacement frequency of tungsten needles.
Smart Images
Figure CN223932786U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of electromechanical product technology, specifically to a control circuit and control device for preventing welding machines from generating inrush current. Background Technology
[0002] Currently, welding machines on the market generate inrush current at the moment of arc initiation. This inrush current can cause the tungsten needle to burn out and cause spatter, as well as perforation and deformation of thin workpieces, and grooves in the arc initiation of thick workpieces, severely affecting the welding quality. In addition, after the tungsten needle is severely burned out, it needs to be replaced and ground frequently, resulting in a significant waste of labor and materials. It is also impossible to operate when welding precision parts, causing great inconvenience to users.
[0003] Therefore, the present invention aims to provide a control circuit and control device to prevent welding machines from generating inrush current, so as to solve the aforementioned problems. Utility Model Content
[0004] The technical problem to be solved by this utility model is to address the issue of inrush current generated at the moment of arc ignition in existing welding machines. The purpose is to provide a control circuit and control device to prevent inrush current in welding machines. By sampling the output current through a welding current feedback unit, it can determine whether the welding machine is in the arc ignition state. When arc ignition occurs, the arc ignition current control unit gradually increases the PI circuit setpoint from 0V to the potentiometer setpoint voltage at the moment of arc ignition, thereby controlling the arc ignition current to gradually increase from 0A to the welding current. Furthermore, the PI voltage control unit clamps the PI circuit setpoint to 9.7V when the welding machine is unloaded, thus solving the technical problem of arc ignition inrush current generated in welding machines.
[0005] This utility model is achieved through the following technical solution:
[0006] A control circuit for preventing inrush current in a welding machine includes a first node for receiving welding feedback current, a second node connected to the given input terminal of the welding machine's PI circuit, a welding current feedback unit, an arc ignition current control unit, and a PI voltage control unit.
[0007] The first connection terminal of the welding current feedback unit is connected to the first node, the second connection terminal of the welding current feedback unit is connected to the first connection terminal of the arc ignition current control unit, and the third connection terminal of the welding current feedback unit is connected to the first connection terminal of the PI voltage control unit.
[0008] The second connection terminal of the arc ignition current control unit is connected to the second node and the second connection terminal of the PI voltage control unit, and the third connection terminal of the arc ignition current control unit is connected to the input terminal of the operating voltage.
[0009] Furthermore, the welding current feedback unit includes a first diode, a first resistor, a second resistor, a first capacitor, and a first transistor; the first node is connected to the anode of the first diode, the cathode of the first diode is connected to the first terminal of the first resistor, and the second terminal of the first resistor is connected to the base of the first transistor; the collector of the first transistor is connected to the first terminal of the arc-starting current control unit, and the emitter of the first transistor is grounded; one end of the parallel connection of the second resistor and the first capacitor is connected between the second terminal of the first resistor and the base of the first transistor, and the other end of the parallel connection of the second resistor and the first capacitor is connected between the emitter of the first transistor and the ground terminal.
[0010] Furthermore, when the first node is at a high level, the welding feedback current received by the first node passes through the first diode, the first resistor, the second resistor, and the first capacitor in sequence, and is then input to the base of the first transistor to turn on the first transistor; when the first node is at a low level, the first transistor is turned off.
[0011] Furthermore, the arc-starting current control device includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second diode, a second capacitor, a third capacitor, and an optocoupler; the LED anode of the optocoupler is connected to the collector of the first transistor; the first connection terminal of the third resistor is connected to the operating voltage input terminal, and the second connection terminals of the third resistor and the first connection terminals of the fourth resistor are both connected between the LED anode of the optocoupler and the collector of the first transistor; the second connection terminal of the fourth resistor is connected to the cathode of the second diode, the anode of the second diode is connected to the first connection terminal of the second capacitor, the second connection terminal of the second capacitor is grounded, and the LED cathode of the optocoupler... The first terminal of the second capacitor is connected between the positive terminal of the second diode and the first terminal of the second capacitor; the collector of the photodetector of the optocoupler is connected to the first terminal of the sixth resistor, the second terminal of the sixth resistor is connected to the working voltage input terminal, the first terminal of the fifth resistor is connected between the collector of the photodetector of the optocoupler and the first terminal of the sixth resistor, and the second terminal of the fifth resistor is grounded; the emitter of the photodetector of the optocoupler is connected to the second terminal of the second node and the PI voltage control unit, the first terminal of the third capacitor is connected between the emitter of the photodetector of the optocoupler and the second terminal of the PI voltage control unit, and the second terminal of the third capacitor is grounded.
[0012] Furthermore, when the LED anode voltage of the optocoupler is clamped, the optocoupler is not conducting, and the voltage of the second node is clamped at 0.7V. The voltage across the second capacitor discharges rapidly through the second diode and the fourth resistor, so that the voltage across the second capacitor is clamped at 0.7V to complete the arc initiation preparation.
[0013] When the LED anode voltage of the optocoupler is not clamped, the working voltage output from the working voltage input terminal passes sequentially through the third resistor, the LED anode of the optocoupler, and the LED cathode of the optocoupler to charge the second capacitor, and the optocoupler is turned on.
[0014] When the optocoupler is turned on, the working voltage output from the working voltage input terminal is divided by the sixth and fifth resistors. The voltage across the fifth resistor passes sequentially through the collector and emitter of the photodetector of the optocoupler to charge the third capacitor, thereby increasing the voltage of the second node. The voltage of the second node is then output to the given input terminal of the PI circuit of the welding machine. After the second capacitor is fully charged, the optocoupler is turned off.
[0015] Furthermore, the PI voltage control unit includes a seventh resistor, an eighth resistor, a fourth capacitor, a second transistor, and a third diode; the first terminal of the seventh resistor is connected between the cathode of the first diode and the first terminal of the first resistor, and the second terminal of the seventh resistor is connected to the base of the second transistor; the collector of the second transistor is connected to the cathode of the third diode, and the emitter of the second transistor is grounded; one end of the parallel connection of the eighth resistor and the fourth capacitor is connected between the second terminal of the seventh resistor and the base of the second transistor, and the other end of the parallel connection of the eighth resistor and the fourth capacitor is connected between the emitter of the second transistor and the ground terminal.
[0016] Furthermore, when the first node is at a high level, the welding feedback current received by the first node passes through the first diode, the seventh resistor, the eighth resistor and the second capacitor in sequence, and is then input to the base of the second transistor to turn on the second transistor.
[0017] Furthermore, after the second transistor is turned on, the voltage across the third capacitor is clamped at 0.7V through the third diode and the second transistor to prepare for the gradual increase of the arc current for the next welding operation; when the first node is at a low level, the second transistor is turned off.
[0018] Furthermore, the operating voltage input terminal receives an operating voltage of +15V1.
[0019] Furthermore, the welding feedback current is acquired by setting a Hall sensor on the output line of the welding machine.
[0020] This utility model also provides a control device for preventing welding machines from generating inrush current. The control device includes a PCD circuit board, on which the control circuit for preventing welding machines from generating inrush current as described above is printed.
[0021] Compared with the prior art, this utility model has the following advantages and beneficial effects:
[0022] In this invention, the welding current feedback unit samples the output current to determine whether the welding machine is in the arc-starting state. When the arc starts, the arc-starting current control unit gradually increases the PI circuit setpoint from 0V to the potentiometer setpoint voltage at the moment of arc start-up, thereby controlling the arc-starting current to gradually increase from 0A to the welding current. The PI voltage control unit also clamps the PI circuit setpoint to 9.7V when the welding machine is unloaded, thus solving the technical problem of generating arc-starting impact current in the welding machine. Attached Figure Description
[0023] To more clearly illustrate the technical solutions of the exemplary embodiments of this utility model, the drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this utility model and should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort. In the drawings:
[0024] Figure 1 This is a circuit diagram of a control circuit for preventing inrush current from being generated in a welding machine, as described in this embodiment. Detailed Implementation
[0025] The exemplary embodiments of this disclosure are described below with reference to the accompanying drawings, including various details of the embodiments to aid understanding, and should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope of this disclosure. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.
[0026] In this disclosure, unless otherwise stated, the use of terms such as "first," "second," etc., to describe various elements is not intended to limit the positional, temporal, or importance relationships of these elements; such terms are merely used to distinguish one element from another. In some examples, the first element and the second element may refer to the same instance of that element, while in other cases, based on the context, they may refer to different instances.
[0027] The terminology used in the description of the various examples in this disclosure is for the purpose of describing particular examples only and is not intended to be limiting. Unless the context explicitly indicates otherwise, an element may be one or more unless the number of elements is specifically limited. Furthermore, the term "and / or" as used in this disclosure covers any one of the listed items and all possible combinations thereof.
[0028] Example 1
[0029] See Figure 1 , Figure 1 A circuit diagram of a control circuit for preventing inrush current in a welding machine is shown. The control circuit includes a first node A for receiving welding feedback current, a second node B connected to the given input terminal of the welding machine's PI circuit, a welding current feedback unit, an arc ignition current control unit, and a PI voltage control unit.
[0030] The first connection terminal of the welding current feedback unit is connected to the first node A, the second connection terminal of the welding current feedback unit is connected to the first connection terminal of the arc ignition current control unit, and the third connection terminal of the welding current feedback unit is connected to the first connection terminal of the PI voltage control unit.
[0031] The second connection terminal of the arc ignition current control unit is connected to the second node B and the second connection terminal of the PI voltage control unit, and the third connection terminal of the arc ignition current control unit is connected to the input terminal of the working voltage.
[0032] Specifically, in this embodiment, the welding current feedback unit is used to determine the working state of the welding machine, which is either an unloaded state or an arc-starting state. When the first node A is at a high level, the welding machine is in an unloaded state; when the first node A is at a low level, the welding machine is in an arc-starting state. The arc-starting current control unit is used to control the welding machine to gradually increase the PI given voltage from 0V to the given value when the arc starts, so as to prevent the generation of inrush current. The PI voltage control unit is used to make it easy to clamp the PI circuit given value to 9.7V when the welding machine is unloaded.
[0033] Furthermore, the welding current feedback unit includes a first diode V1, a first resistor R1, a second resistor R2, a first capacitor C1, and a first transistor Q1; the first node A is connected to the anode of the first diode V1, the cathode of the first diode V1 is connected to the first connection terminal of the first resistor R1, and the second connection terminal of the first resistor R1 is connected to the base of the first transistor Q1; the collector of the first transistor Q1 is connected to the first connection terminal of the arc-starting current control unit, and the emitter of the first transistor Q1 is grounded; one end of the parallel connection of the second resistor R2 and the first capacitor C1 is connected between the second connection terminal of the first resistor R1 and the base of the first transistor Q1, and the other end of the parallel connection of the second resistor R2 and the first capacitor C1 is connected between the emitter of the first transistor Q1 and the ground terminal.
[0034] Furthermore, when the first node A is at a high level, the welding feedback current received by the first node A passes through the first diode V1, the first resistor R1, the second resistor R2 and the first capacitor C1 in sequence, and is then input to the base of the first transistor Q1, so that the first transistor Q1 is turned on; when the first node A is at a low level, the first transistor Q1 is turned off.
[0035] It should be noted that in this embodiment, when the first node A is at a high level, the first transistor Q1 is turned on, and the LED anode voltage of the optocoupler N1 will be clamped to 0V; when the first node A is at a low level, the first transistor Q1 is turned off, and the LED anode of the optocoupler N1 generates voltage through the working voltage input, and the optocoupler N1 is turned on.
[0036] Furthermore, the arc-starting current control device includes a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a second diode V2, a second capacitor C2, a third capacitor C3, and an optocoupler N1; the LED anode of the optocoupler N1 is connected to the collector of the first transistor Q1; the first connection terminal of the third resistor R3 is connected to the working voltage input terminal, and the second connection terminals of the third resistor R3 and the first connection terminals of the fourth resistor R4 are both connected between the LED anode of the optocoupler N1 and the collector of the first transistor Q1; the second connection terminal of the fourth resistor R4 is connected to the cathode of the second diode V2, the anode of the second diode V2 is connected to the first connection terminal of the second capacitor C2, the second connection terminal of the second capacitor C2 is grounded, and the optocoupler N1... The cathode of LED 1 is connected between the positive terminal of the second diode V2 and the first terminal of the second capacitor C2; the collector of the photodetector of optocoupler N1 is connected to the first terminal of the sixth resistor R6, the second terminal of the sixth resistor R6 is connected to the working voltage input terminal, the first terminal of the fifth resistor R5 is connected between the collector of the photodetector of optocoupler N1 and the first terminal of the sixth resistor R6, and the second terminal of the fifth resistor R5 is grounded; the emitter of the photodetector of optocoupler N1 is connected to the second terminal of the second node B and the second terminal of the PI voltage control unit, the first terminal of the third capacitor C3 is connected between the emitter of the photodetector of optocoupler N1 and the second terminal of the PI voltage control unit, and the second terminal of the third capacitor C3 is grounded.
[0037] Furthermore, when the LED anode voltage of optocoupler N1 is clamped, optocoupler N1 is not conducting, and the voltage of the second node B is clamped at 0.7V. The voltage across the second capacitor C2 is rapidly discharged through the second diode V2 and the fourth resistor R4, so that the voltage across the second capacitor C2 is clamped at 0.7V to complete the arc initiation preparation.
[0038] When the LED anode voltage of optocoupler N1 is not clamped, the working voltage output from the working voltage input terminal passes through the third resistor R3, the LED anode of optocoupler N1, and the LED cathode of optocoupler N1 in sequence, charging the second capacitor C2, and the optocoupler N1 is turned on.
[0039] When optocoupler N1 is turned on, the working voltage output from the working voltage input terminal is divided by the sixth resistor R6 and the fifth resistor R5. The voltage across the fifth resistor R5 passes sequentially through the collector and emitter of the photodetector of optocoupler N1, charging the third capacitor C3 and increasing the voltage at the second node B. The voltage at the second node B is then output to the given input terminal of the welding machine's PI circuit. After the second capacitor C2 has finished charging, optocoupler N1 is turned off.
[0040] It should be noted that in this embodiment, when the first transistor Q1 is turned on and the LED anode voltage of the optocoupler N1 is clamped to 0V, the voltage across the second capacitor C2 is rapidly discharged through the second diode V2 and the fourth resistor R4, so that the voltage across the second capacitor C2 is clamped to 0.7V to complete the arc preparation work. At this time, the optocoupler N1 is not turned on, and the voltage of the second node B is 0.7V.
[0041] When the first transistor Q1 is off, and the LED anode of optocoupler N1 generates voltage through the working voltage input, the +15V1 working voltage charges the second capacitor C2 through the third resistor R3, the LED anode of optocoupler N1, and the LED cathode of optocoupler N1. During the charging process, optocoupler N1 is turned on, and the charging time is the gradual rise time of the arc current. When the second capacitor C2 is fully charged, optocoupler N1 is turned off. When optocoupler N1 is turned on, the +15V1 working voltage is divided by the sixth resistor R6 and the fifth resistor R5. The voltage across the fifth resistor R5 passes sequentially through the collector and emitter of the photodetector of optocoupler N1, charging the third capacitor C3, which increases the voltage at the second node B. The voltage at the second node B is output to the given input terminal of the welding machine's PI circuit, causing the arc current to rise slowly without inrush current. At the same time, the charging process of the third capacitor C3 is the process of the arc current rising slowly.
[0042] Furthermore, the PI voltage control unit includes a seventh resistor R7, an eighth resistor R8, a fourth capacitor C4, a second transistor Q2, and a third diode V3; the first terminal of the seventh resistor R7 is connected between the cathode of the first diode V1 and the first terminal of the first resistor R1, and the second terminal of the seventh resistor R7 is connected to the base of the second transistor Q2; the collector of the second transistor Q2 is connected to the cathode of the third diode V3, and the emitter of the second transistor Q2 is grounded; one end of the parallel connection of the eighth resistor R8 and the fourth capacitor C4 is connected between the second terminal of the seventh resistor R7 and the base of the second transistor Q2, and the other end of the parallel connection of the eighth resistor R8 and the fourth capacitor C4 is connected between the emitter of the second transistor Q2 and the ground terminal.
[0043] Furthermore, when the first node A is at a high level, the welding feedback current received by the first node A passes through the first diode V1, the seventh resistor R7, the eighth resistor R8 and the second capacitor C2 in sequence, and is then input to the base of the second transistor Q2, so that the second transistor Q2 is turned on.
[0044] Furthermore, after the second transistor Q2 is turned on, the voltage across the third capacitor C3 is clamped at 0.7V through the third diode V3 and the second transistor Q2 to prepare for the gradual increase of the arc-starting current for the next welding operation; when the first node A is at a low level, the second transistor Q2 is turned off.
[0045] It should be noted that in this embodiment, when the first node A is at a high level, the second transistor Q2 and the third diode V3 are turned on, clamping the voltage of the third capacitor C3 to 0.7V, preparing for the gradual increase of the welding arc current; when the first node A is at a low level, the second transistor Q2 and the third diode V3 are turned off, the voltage of the third capacitor C3 stops clamping, and slowly increases under the working voltage, the voltage of the second node B gradually increases, and the voltage of the second node B is directly input to the given input terminal of the PI circuit, so that the arc current increases slowly without impact current.
[0046] Furthermore, the operating voltage input terminal is set to +15V1.
[0047] Furthermore, the welding feedback current is acquired by setting a Hall sensor on the output line of the welding machine.
[0048] Workflow: When the welding machine is unloaded, the voltage at the first node A is high. After passing through the first diode V1, the first branch passes through the first resistor R1, the second resistor R2, and the first capacitor C1, reaching the base of the first transistor Q1. This turns on the first transistor Q1, clamping the LED anode voltage of the optocoupler N1 to 0V. Optocoupler N1 is then cut off, preventing the third capacitor C3 from charging, and the voltage across the third capacitor is 0.7V. Simultaneously, the voltage across the second capacitor C2 passes through the second diode V2 and the fourth resistor R4 to the first transistor Q1. The collector discharges rapidly, clamping the voltage across the second capacitor C2 to around 0.7V, preparing for the next arc initiation. The voltage at the first node passes through another branch of the first diode V1 to the seventh resistor R7, the eighth resistor R8, and the fourth capacitor C4 to the base of the second transistor Q2, causing the second transistor Q2 to conduct. The voltage across the third capacitor C3 passes through the third diode V3 to the collector of the second transistor Q2, where it is clamped. At this time, the voltage at the second node is 0.7V, and the input voltage of the PI circuit is clamped to 0.7V, preparing for the arc initiation.
[0049] When the welding machine is welding, the voltage at the first node A becomes low, at which point the first transistor Q1 and the second transistor Q2 are cut off. The +15V1 working voltage charges the second capacitor C2 through the third resistor R3, the LED anode and the LED cathode of the optocoupler N1, and the optocoupler N1 is turned on. The charging time of the second capacitor C2 is the conduction time of the optocoupler. At the same time, the +15V1 working voltage charges the third capacitor C3 through the sixth resistor R6, the seventh resistor R5, and the photodetector collector and the photodetector emitter of the optocoupler N1. The voltage across the third capacitor C3 increases slowly, causing the voltage at the second node to increase slowly. The input voltage of the PI circuit also increases slowly, and the welding current increases slowly, thus preventing overshoot current. When the third capacitor C3 is fully charged, the voltage value at the second node is determined by a given value, and the welding current is controlled by the given value.
[0050] Example 2
[0051] This utility model also provides a control device for preventing welding machines from generating inrush current. The control device includes a PCD circuit board, on which a control circuit for preventing welding machines from generating inrush current is printed as described above.
[0052] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of this utility model. It should be understood that the above description is only a specific embodiment of this utility model and is not intended to limit the scope of protection of this utility model. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this utility model should be included within the scope of protection of this utility model.
Claims
1. A control circuit for preventing inrush current from being generated in a welding machine, characterized in that, The control circuit includes a first node for receiving welding feedback current, a second node connected to the given input terminal of the welding machine's PI circuit, a welding current feedback unit, an arc ignition current control unit, and a PI voltage control unit. The first connection terminal of the welding current feedback unit is connected to the first node, the second connection terminal of the welding current feedback unit is connected to the first connection terminal of the arc ignition current control unit, and the third connection terminal of the welding current feedback unit is connected to the first connection terminal of the PI voltage control unit. The second connection terminal of the arc ignition current control unit is connected to the second node and the second connection terminal of the PI voltage control unit, and the third connection terminal of the arc ignition current control unit is connected to the input terminal of the operating voltage.
2. The control circuit for preventing inrush current from being generated in a welding machine according to claim 1, characterized in that, The welding current feedback unit includes a first diode, a first resistor, a second resistor, a first capacitor, and a first transistor. The first node is connected to the anode of the first diode, the cathode of the first diode is connected to the first terminal of the first resistor, and the second terminal of the first resistor is connected to the base of the first transistor. The collector of the first transistor is connected to the first terminal of the arc-starting current control unit, and the emitter of the first transistor is grounded. One end of the parallel connection of the second resistor and the first capacitor is connected between the second terminal of the first resistor and the base of the first transistor, and the other end of the parallel connection of the second resistor and the first capacitor is connected between the emitter of the first transistor and the ground terminal.
3. The control circuit for preventing inrush current from being generated in a welding machine according to claim 2, characterized in that, When the first node is at a high level, the welding feedback current received by the first node passes through the first diode, the first resistor, the second resistor, and the first capacitor in sequence, and is then input to the base of the first transistor to turn on the first transistor; when the first node is at a low level, the first transistor is turned off.
4. The control circuit for preventing inrush current from being generated in a welding machine according to claim 2, characterized in that, The arc-starting current control device includes a third resistor, a fourth resistor, a fifth resistor, a sixth resistor, a second diode, a second capacitor, a third capacitor, and an optocoupler. The LED anode of the optocoupler is connected to the collector of a first transistor. The first terminal of the third resistor is connected to the operating voltage input terminal. The second terminals of the third resistor and the first terminals of the fourth resistor are both connected between the LED anode of the optocoupler and the collector of the first transistor. The second terminal of the fourth resistor is connected to the cathode of the second diode. The anode of the second diode is connected to the first terminal of the second capacitor. The second terminal of the second capacitor is grounded. The LED cathode of the optocoupler is connected to... The photodetector collector of the optocoupler is connected to the first connection terminal of the sixth resistor, the second connection terminal of the sixth resistor is connected to the operating voltage input terminal, the first connection terminal of the fifth resistor is connected between the photodetector collector of the optocoupler and the first connection terminal of the sixth resistor, and the second connection terminal of the fifth resistor is grounded; the photodetector emitter of the optocoupler is connected to the second node and the second connection terminal of the PI voltage control unit, the first connection terminal of the third capacitor is connected between the photodetector emitter of the optocoupler and the second connection terminal of the PI voltage control unit, and the second connection terminal of the third capacitor is grounded.
5. A control circuit for preventing inrush current from being generated in a welding machine according to claim 4, characterized in that, When the LED anode voltage of the optocoupler is clamped, the optocoupler is not conducting, and the voltage of the second node is clamped at 0.7V. The voltage across the second capacitor is rapidly discharged through the second diode and the fourth resistor, so that the voltage across the second capacitor is clamped at 0.7V to complete the arc initiation preparation. When the LED anode voltage of the optocoupler is not clamped, the working voltage output from the working voltage input terminal passes sequentially through the third resistor, the LED anode of the optocoupler, and the LED cathode of the optocoupler to charge the second capacitor, and the optocoupler is turned on. When the optocoupler is turned on, the working voltage output from the working voltage input terminal is divided by the sixth and fifth resistors. The voltage across the fifth resistor passes sequentially through the collector and emitter of the photodetector of the optocoupler to charge the third capacitor, thereby increasing the voltage of the second node. The voltage of the second node is then output to the given input terminal of the PI circuit of the welding machine. After the second capacitor is fully charged, the optocoupler is turned off.
6. The control circuit for preventing inrush current from being generated in a welding machine according to claim 4, characterized in that, The PI voltage control unit includes a seventh resistor, an eighth resistor, a fourth capacitor, a second transistor, and a third diode. The first terminal of the seventh resistor is connected between the cathode of the first diode and the first terminal of the first resistor, and the second terminal of the seventh resistor is connected to the base of the second transistor. The collector of the second transistor is connected to the cathode of the third diode, and the emitter of the second transistor is grounded. One end of the parallel connection of the eighth resistor and the fourth capacitor is connected between the second terminal of the seventh resistor and the base of the second transistor, and the other end of the parallel connection of the eighth resistor and the fourth capacitor is connected between the emitter of the second transistor and the ground terminal.
7. The control circuit for preventing inrush current from being generated in a welding machine according to claim 6, characterized in that, When the first node is at a high level, the welding feedback current received by the first node passes through the first diode, the seventh resistor, the eighth resistor and the second capacitor in sequence, and is then input to the base of the second transistor to turn on the second transistor. Furthermore, after the second transistor is turned on, the voltage across the third capacitor is clamped at 0.7V through the third diode and the second transistor to prepare for the gradual increase of the arc-starting current for the next welding operation; when the first node is at a low level, the second transistor is turned off.
8. The control circuit for preventing inrush current from being generated in a welding machine according to claim 1, characterized in that, The operating voltage input terminal receives an operating voltage of +15V.
9. A control circuit for preventing inrush current from being generated in a welding machine according to claim 1, characterized in that, The welding feedback current is obtained by setting a Hall sensor on the output line of the welding machine.
10. A control device for preventing inrush current from being generated in a welding machine, characterized in that, The control device includes a PCD circuit board, on which a control circuit for preventing the welding machine from generating inrush current is printed as described in any one of claims 1-9.