Driving circuit of thyristor arc welding machine

Abstract

A driving circuit of a thyristor arc welding machine includes a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect tube Q1, first to fourth transistors, a first timer U1, a second timer U2, a photocoupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, first to third diodes, a light emitting diode D4, first to twenty-first resistors, and first to tenth capacitors. In this way, overcurrent protection can be achieved without stopping or restarting, and the working efficiency is high.

Description

Technical Field

[0001] The invention relates to the technical field of stud welding equipment, in particular to a driving circuit of a thyristor drawn arc welding machine. Background Art

[0002] When welding, the existing stud welding equipment will form a large current interval in the latter part of its driving waveform. Excessive current will cause the electronic components in the welding gun of the stud welding equipment to work under an overload state, which may cause burning or reduce the service life. The existing stud welding equipment overcurrent protection shuts down the entire circuit when the current is detected to be greater than a predetermined value, thus causing shutdown. If it needs to continue working, it needs to be restarted, affecting work efficiency. Summary of the invention

[0003] In view of this, the present invention provides a driving circuit for a thyristor arc welding machine which can achieve overcurrent protection without stopping or restarting and has high working efficiency, so as to solve the above problems.

[0004] A driving circuit of a thyristor arc welding machine, comprising a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect tube Q1, a first transistor Q2, a second transistor Q3, a third transistor Q4, a fourth transistor Q5, a first timer U1, a second timer U2, a photoelectric coupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, a first diode D1, a second diode D2, a third diode D3, a light emitting diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, and a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a tenth capacitor C10; a first input end of the rectifier bridge BR is connected to the positive electrode AC+ of an AC power supply, and a second input end of the rectifier bridge BR is connected to the negative electrode AC- of the AC power supply through a fuse FUSE; a first output end of the rectifier bridge BR is connected to a first end of the welding gun electromagnetic coil L1, and a second output end The first output terminal of the welding gun is connected to the ground, and is connected to the first output terminal of the rectifier bridge BR through the first resistor R1, and the second output terminal is also connected to the first output terminal through the first capacitor C1; the second end of the welding gun electromagnetic coil L1 is connected to the drain of the field effect tube Q1; the source of the field effect tube Q1 is grounded through the second resistor R2, and the gate is grounded through the third resistor R3; the grounding terminal of the first timer U1 is grounded, and the output terminal is connected to the base of the first transistor Q2 and the base of the second transistor Q3 through the fourth resistor R4; the collector of the first transistor Q2 is grounded, and the emitter is connected to the gate of the field effect tube Q1 through the sixth resistor R6; the collector of the second transistor Q3 is connected to the reset terminal of the first timer U1 through the seventh resistor R7, and the emitter is connected to the emitter of the first transistor Q2. The output end of the first timer U1 is also connected to the first end of the second capacitor C2 through the fifth resistor R5, and the second end of the second capacitor C2 is grounded; the control end of the first timer U1 is grounded through the third capacitor C3, the threshold end is grounded through the fourth capacitor C4 and is connected to the output end of the first NAND gate NAND1 through the eighth resistor R8; the output end of the first NAND gate NAND1 is also connected to a first DC power supply VDD through the ninth resistor R9, and the first input end and the second input end of the first NAND gate NAND1 are both connected to the first DC power supply VDD through the tenth resistor R10; the discharge end of the first timer U1 is connected to the first input end of the second NAND gate NAND2, and is also connected to the power supply end of the first timer U1 through the eleventh resistor R11;The second input end of the second NAND gate NAND2 is connected to the node between the fifth resistor R5 and the second capacitor C2, and the output end of the second NAND gate NAND2 is connected to the first input end or the second input end of the first NAND gate NAND1; the power supply end of the first timer U1 is connected to the first DC power supply VDD and is also grounded through the fifth capacitor C5; the base of the third transistor Q4 is connected to the source of the field effect transistor Q1 through the twelfth resistor R12, the collector is connected to the first DC power supply VDD through the fourteenth resistor R14, and the emitter is grounded; The base of the third transistor Q4 is also grounded through the thirteenth resistor R13, and the sixth capacitor C6 is connected in parallel with the thirteenth resistor R13; the grounding end of the second timer U2 is grounded, the trigger end is connected to the collector of the third transistor Q4, and is also grounded through the fifteenth resistor R15, and the seventh capacitor C7 is connected in parallel with the fifteenth resistor R15; the reset end of the second timer U2 is connected to the first DC power supply VDD through the sixteenth resistor R16, and is also grounded through the eighth capacitor C8; the threshold end of the second timer U2 is grounded through the ninth capacitor C9, and the power supply end is connected to the first DC power supply VDD. The collector of the fourth triode Q5 is connected to the reset terminal of the first timer U1, and is also connected to the anode of the second diode D2. The cathode of the second diode D2 is grounded through the seventeenth resistor R17. The tenth capacitor C10 is connected in parallel with the seventeenth resistor R17. The base of the fourth triode Q5 is connected to the anode of the third diode D3. The cathode of the third diode D3 is connected to the first DC power supply VDD through the nineteenth resistor R19. The emitter of the fourth triode Q5 is grounded and connected to the fourth triode Q5 through the eighteenth resistor R18. The positive input terminal in+ of the photocoupler U3 is connected to a second DC power supply VCC, the negative input terminal in- is connected to the anode of the light-emitting diode D4, and the cathode of the light-emitting diode D4 is connected to the output terminal of the inverter NOT through the 20th resistor R20; the input terminal of the inverter NOT is connected to the second DC power supply VCC through the 21st resistor R21; the negative output terminal out- of the photocoupler U3 is connected to the output terminal of the second timer U2, and the positive output terminal out+ is connected to the anode of the third diode D3. ;

[0005] Furthermore, the second end of the welding gun electromagnetic coil L1 is also connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the first end of the welding gun electromagnetic coil L1.

[0006] Compared with the prior art, the driving circuit of the thyristor arc welding machine of the present invention includes a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect transistor Q1, a first transistor Q2, a second transistor Q3, a third transistor Q4, a fourth transistor Q5, a first timer U1, a second timer U2, a photocoupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, a first diode D1, a second diode D2, a third diode D3, a light emitting diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first resistor R10, a second resistor R11, a second resistor R12, a third resistor R13, a fourth resistor R14, a fifth resistor R15, a sixth resistor R16, a seventh resistor R17, an eighth resistor R18, an ninth resistor R19, a first resistor R20, a second resistor R21, a second resistor R22 a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a tenth capacitor C10; a first input end of the rectifier bridge BR is connected to a positive electrode AC+ of an AC power source, and a second input end of the rectifier bridge BR is connected to a negative electrode AC- of the AC power source through a fuse FUSE. ; The first output end of the rectifier bridge BR is connected to the first end of the welding gun electromagnetic coil L1, the second output end is grounded, and is connected to the first output end of the rectifier bridge BR through the first resistor R1, and the second output end is also connected to the first output end through the first capacitor C1; the second end of the welding gun electromagnetic coil L1 is connected to the drain of the field effect transistor Q1; the source of the field effect transistor Q1 is grounded through the second resistor R2, and the gate is grounded through the third resistor R3; the ground end of the first timer U1 is grounded, and the output end is connected to the base of the first transistor Q2 and the base of the second transistor Q3 through the fourth resistor R4; the collector of the first transistor Q2 is grounded, and the emitter is connected to the gate of the field effect transistor Q1 through the sixth resistor R6; the second transistor The collector of Q3 is connected to the reset terminal of the first timer U1 through the seventh resistor R7, and the emitter is connected to the emitter of the first transistor Q2; the output terminal of the first timer U1 is also connected to the first terminal of the second capacitor C2 through the fifth resistor R5, and the second terminal of the second capacitor C2 is grounded; the control terminal of the first timer U1 is grounded through the third capacitor C3, the threshold terminal is grounded through the fourth capacitor C4 and is connected to the output terminal of the first NAND gate NAND1 through the eighth resistor R8; the output terminal of the first NAND gate NAND1 is also connected to a first DC power supply VDD through the ninth resistor R9, and the first input terminal and the second input terminal of the first NAND gate NAND1 are both connected to the first DC power supply VDD through the tenth resistor R10;The discharge end of the first timer U1 is connected to the first input end of the second NAND gate NAND2, and is also connected to the power supply end of the first timer U1 through the eleventh resistor R11; the second input end of the second NAND gate NAND2 is connected to the node between the fifth resistor R5 and the second capacitor C2, and the output end of the second NAND gate NAND2 is connected to the first input end or the second input end of the first NAND gate NAND1; the power supply end of the first timer U1 is connected to the first DC power supply VDD, and is also grounded through the fifth capacitor C5; the base of the third transistor Q4 is connected to the field effect transistor Q4 through the twelfth resistor R12. The source of the transistor Q1 is connected, the collector is connected to the first DC power supply VDD through the fourteenth resistor R14, and the emitter is grounded; the base of the third transistor Q4 is also grounded through the thirteenth resistor R13, and the sixth capacitor C6 is connected in parallel with the thirteenth resistor R13; the grounding end of the second timer U2 is grounded, the trigger end is connected to the collector of the third transistor Q4, and is also grounded through the fifteenth resistor R15, and the seventh capacitor C7 is connected in parallel with the fifteenth resistor R15; the reset end of the second timer U2 is connected to the first DC power supply VDD through the sixteenth resistor R16, and is also grounded through the eighth capacitor C8; the second The threshold end of the timer U2 is grounded through the ninth capacitor C9, and the power end is connected to the first DC power supply VDD; the collector of the fourth transistor Q5 is connected to the reset end of the first timer U1, and is also connected to the anode of the second diode D2, the cathode of the second diode D2 is grounded through the seventeenth resistor R17, and the tenth capacitor C10 is connected in parallel with the seventeenth resistor R17; the base of the fourth transistor Q5 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the first DC power supply VDD through the nineteenth resistor R19, the emitter of the fourth transistor Q5 is grounded, and is connected through the tenth The eight resistors R18 are connected to the base of the fourth transistor Q5; the positive input terminal in+ of the photocoupler U3 is connected to a second DC power supply VCC, the negative input terminal in- is connected to the anode of the light-emitting diode D4, and the cathode of the light-emitting diode D4 is connected to the output terminal of the inverter NOT through the twentieth resistor R20; the input terminal of the inverter NOT is connected to the second DC power supply VCC through the twenty-first resistor R21; the negative output terminal out- of the photocoupler U3 is connected to the output terminal of the second timer U2, and the positive output terminal out+ is connected to the anode of the third diode D3. In this way, overcurrent protection can be achieved without stopping or restarting, and the working efficiency is high. ; BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The embodiments of the present invention are described below in conjunction with the accompanying drawings, wherein:

[0008] Figure 1 A circuit diagram of a drive circuit for a thyristor drawn arc welding machine provided by the present invention. DETAILED DESCRIPTION

[0009] The specific embodiments of the present invention are further described in detail below based on the accompanying drawings. It should be understood that the description of the embodiments of the present invention herein is not intended to limit the protection scope of the present invention.

[0010] Please refer to Figure 1 The driving circuit of the thyristor arc welding machine provided by the present invention includes a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect tube Q1, a first transistor Q2, a second transistor Q3, a third transistor Q4, a fourth transistor Q5, a first timer U1, a second timer U2, a photocoupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, a first diode D1, a second diode D2, a third diode D3, a light emitting diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth Resistor R6, seventh resistor R7, eighth resistor R8, ninth resistor R9, tenth resistor R10, eleventh resistor R11, twelfth resistor R12, thirteenth resistor R13, fourteenth resistor R14, fifteenth resistor R15, sixteenth resistor R16, seventeenth resistor R17, eighteenth resistor R18, nineteenth resistor R19, twentieth resistor R20, twenty-first resistor R21, first capacitor C1, second capacitor C2, third capacitor C3, fourth capacitor C4, fifth capacitor C5, sixth capacitor C6, seventh capacitor C7, eighth capacitor C8, ninth capacitor C9, tenth capacitor C10.

[0011] A first input terminal of the rectifier bridge BR is connected to the positive electrode AC+ of an AC power source, and a second input terminal of the rectifier bridge BR is connected to the negative electrode AC- of the AC power source through a fuse FUSE. The voltage of the AC power source is 75V.

[0012] The first output end of the rectifier bridge BR is connected to the first end of the welding gun electromagnetic coil L1, and the second output end is grounded and connected to the first output end of the rectifier bridge BR through the first resistor R1. The second output end is also connected to the first output end through the first capacitor C1.

[0013] The second end of the welding gun electromagnetic coil L1 is connected to the drain of the field effect transistor Q1; the source of the field effect transistor Q1 is grounded through the second resistor R2, and the gate is grounded through the third resistor R3.

[0014] The second end of the welding gun electromagnetic coil L1 is also connected to the anode of the first diode D1 , and the cathode of the first diode D1 is connected to the first end of the welding gun electromagnetic coil L1 .

[0015] The first timer U1 and the second timer U2 both have 8 pins, of which pin 1 is the ground terminal, pin 2 is the trigger terminal (low level trigger), pin 3 is the output terminal, pin 4 is the reset terminal (low level trigger), pin 5 is the control terminal, pin 6 is the threshold terminal, pin 7 is the discharge terminal, and pin 8 is the power supply terminal.

[0016] The ground terminal of the first timer U1 is grounded, and the output terminal is connected to the base of the first transistor Q2 and the base of the second transistor Q3 through the fourth resistor R4; the collector of the first transistor Q2 is grounded, and the emitter is connected to the gate of the field effect transistor Q1 through the sixth resistor R6; the collector of the second transistor Q3 is connected to the reset terminal of the first timer U1 through the seventh resistor R7, and the emitter is connected to the emitter of the first transistor Q2.

[0017] The output end of the first timer U1 is also connected to the first end of the second capacitor C2 through the fifth resistor R5, and the second end of the second capacitor C2 is grounded.

[0018] The control end of the first timer U1 is grounded through the third capacitor C3, the threshold end is grounded through the fourth capacitor C4, and is also connected to the output end of the first NAND gate NAND1 through the eighth resistor R8. The output end of the first NAND gate NAND1 is also connected to a first DC power supply VDD through the ninth resistor R9, and the first input end and the second input end of the first NAND gate NAND1 are both connected to the first DC power supply VDD through the tenth resistor R10.

[0019] The discharge end of the first timer U1 is connected to the first input end of the second NAND gate NAND2, and is also connected to the power supply end of the first timer U1 through the eleventh resistor R11. The second input end of the second NAND gate NAND2 is connected to the node between the fifth resistor R5 and the second capacitor C2, and the output end of the second NAND gate NAND2 is connected to the first input end or the second input end of the first NAND gate NAND1.

[0020] A power supply terminal of the first timer U1 is connected to the first DC power supply VDD and is also grounded via a fifth capacitor C5.

[0021] The base of the third transistor Q4 is connected to the source of the field effect transistor Q1 through the twelfth resistor R12, the collector is connected to the first DC power supply VDD through the fourteenth resistor R14, and the emitter is grounded. The base of the third transistor Q4 is also grounded through the thirteenth resistor R13, and the sixth capacitor C6 is connected in parallel with the thirteenth resistor R13.

[0022] In this way, the first timer U1 is set to the working mode of the Schmitt trigger.

[0023] The grounding terminal of the second timer U2 is grounded, the triggering terminal is connected to the collector of the third transistor Q4, and is also grounded through the fifteenth resistor R15, and the seventh capacitor C7 is connected in parallel with the fifteenth resistor R15.

[0024] The output terminal of the second timer U2 is used to output a delay signal TDL.

[0025] A reset terminal of the second timer U2 is connected to the first DC power supply VDD through a sixteenth resistor R16, and is also grounded through an eighth capacitor C8.

[0026] The threshold end of the second timer U2 is grounded through a ninth capacitor C9, and the power supply end is connected to the first DC power supply VDD.

[0027] In this way, the second timer U2 is set to the monostable working mode.

[0028] The collector of the fourth transistor Q5 is connected to the reset terminal of the first timer U1 and also to the anode of the second diode D2. The cathode of the second diode D2 is grounded through the seventeenth resistor R17. The tenth capacitor C10 is connected in parallel to the seventeenth resistor R17.

[0029] The base of the fourth transistor Q5 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the first DC power supply VDD through the nineteenth resistor R19, the emitter of the fourth transistor Q5 is grounded and connected to the base of the fourth transistor Q5 through the eighteenth resistor R18.

[0030] The photocoupler U3 has a positive input terminal in+, a negative input terminal in−, a positive output terminal out+ and a negative output terminal out−.

[0031] The positive input terminal in+ of the photocoupler U3 is connected to a second DC power source VCC, and the voltage of the second DC power source VCC is 15V.

[0032] The negative input terminal in- of the photocoupler U3 is connected to the anode of the light-emitting diode D4, the cathode of the light-emitting diode D4 is connected to the output terminal of the inverter NOT through the 20th resistor R20, the input terminal of the inverter NOT is connected to the enable terminal EN of a controller, and is used to receive the enable signal of the enable terminal EN. The input terminal of the inverter NOT is also connected to the second DC power supply VCC through the 21st resistor R21.

[0033] The negative output terminal out- of the photocoupler U3 is connected to the output terminal of the second timer U2 to receive the output delay signal TDL.

[0034] The positive output terminal out+ is connected to the anode of the third diode D3.

[0035] The following is an explanation of the working process:

[0036] The rectifier bridge BR is used to convert AC power into DC power to drive the welding gun electromagnetic coil L1 to work. The field effect tube Q1 is used to control the on and off of the welding gun electromagnetic coil L1. When the field effect tube Q1 is turned on, the second end of the welding gun electromagnetic coil L1 is grounded through the second resistor R2 to form a loop, otherwise the second end of the welding gun electromagnetic coil L1 is open.

[0037] The field effect tube Q1 is driven by a totem pole driving unit composed of a first transistor Q2 and a second transistor Q3, and the totem pole driving unit is driven by the output end of the first timer U1. When the output end of the first timer U1 outputs a high level, the first transistor Q2 and the second transistor Q3 are both turned on, so that the field effect tube Q1 is turned on, and the welding gun electromagnetic coil L1 works.

[0038] The first timer U1 continuously outputs pulses driven by the charging and discharging of the eleventh resistor R11 and the fifth capacitor C5, so that the supply voltage of the welding gun electromagnetic coil L1 is also in a discontinuous state. Since the current of the welding gun electromagnetic coil L1 will not drop immediately, the electromagnet of the welding gun can maintain the attracted state, and the heating of the electromagnet is reduced at the same time.

[0039] The third transistor Q4 samples the current flowing through the welding gun electromagnetic coil L1 through the twelfth resistor R12 and the second resistor R2.

[0040] When the sampling current is greater than or equal to a certain value, the third transistor Q4 is turned on, and the trigger end of the second timer U2 is pulled to a low level, so that the output end of the second timer U2 outputs a high level. At this time, the photoelectric coupler U3 is blocked, and the fourth transistor Q5 is turned on, so that the reset end of the first timer U1 is pulled to a low level, the first timer U1 is reset, and the output end of the first timer U1 does not output, thereby making the first transistor Q2 and the second transistor Q3 both cut off, the field effect tube Q1 cut off, and the welding gun electromagnetic coil L1 stops working.

[0041] When the sampling current is less than the set value, the photocoupler U3 is turned on, the fourth transistor Q5 is turned off, and then the output end of the first timer U1 outputs a high level again, the first transistor Q2 and the second transistor Q3 are both turned on, the field effect transistor Q1 is turned on, and the welding gun electromagnetic coil L1 continues to work. In this way, chopping is achieved when the current of the welding gun electromagnetic coil L1 is large.

[0042] The enable signal of the enable terminal EN of the controller controls the on-off of the photocoupler U3 at the same time, thereby realizing the control of the welding gun electromagnetic coil L1.

[0043] When the field effect transistor Q1 is turned off, the electric energy stored in the welding gun electromagnetic coil L1 is discharged through the first diode D1.

[0044] The first NAND gate NAND1 and the second NAND gate NAND2 are used to stabilize the waveform.

[0045] Compared with the prior art, the driving circuit of the thyristor arc welding machine of the present invention includes a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect transistor Q1, a first transistor Q2, a second transistor Q3, a third transistor Q4, a fourth transistor Q5, a first timer U1, a second timer U2, a photocoupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, a first diode D1, a second diode D2, a third diode D3, a light emitting diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a first resistor R10, a second resistor R11, a second resistor R12, a third resistor R13, a fourth resistor R14, a fifth resistor R15, a sixth resistor R16, a seventh resistor R17, an eighth resistor R18, an ninth resistor R19, a first resistor R20, a second resistor R21, a second resistor R22 a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a tenth capacitor C10; a first input end of the rectifier bridge BR is connected to a positive electrode AC+ of an AC power source, and a second input end of the rectifier bridge BR is connected to a negative electrode AC- of the AC power source through a fuse FUSE. ; The first output end of the rectifier bridge BR is connected to the first end of the welding gun electromagnetic coil L1, the second output end is grounded, and is connected to the first output end of the rectifier bridge BR through the first resistor R1, and the second output end is also connected to the first output end through the first capacitor C1; the second end of the welding gun electromagnetic coil L1 is connected to the drain of the field effect transistor Q1; the source of the field effect transistor Q1 is grounded through the second resistor R2, and the gate is grounded through the third resistor R3; the ground end of the first timer U1 is grounded, and the output end is connected to the base of the first transistor Q2 and the base of the second transistor Q3 through the fourth resistor R4; the collector of the first transistor Q2 is grounded, and the emitter is connected to the gate of the field effect transistor Q1 through the sixth resistor R6; the second transistor The collector of Q3 is connected to the reset terminal of the first timer U1 through the seventh resistor R7, and the emitter is connected to the emitter of the first transistor Q2; the output terminal of the first timer U1 is also connected to the first terminal of the second capacitor C2 through the fifth resistor R5, and the second terminal of the second capacitor C2 is grounded; the control terminal of the first timer U1 is grounded through the third capacitor C3, the threshold terminal is grounded through the fourth capacitor C4 and is connected to the output terminal of the first NAND gate NAND1 through the eighth resistor R8; the output terminal of the first NAND gate NAND1 is also connected to a first DC power supply VDD through the ninth resistor R9, and the first input terminal and the second input terminal of the first NAND gate NAND1 are both connected to the first DC power supply VDD through the tenth resistor R10;The discharge end of the first timer U1 is connected to the first input end of the second NAND gate NAND2, and is also connected to the power supply end of the first timer U1 through the eleventh resistor R11; the second input end of the second NAND gate NAND2 is connected to the node between the fifth resistor R5 and the second capacitor C2, and the output end of the second NAND gate NAND2 is connected to the first input end or the second input end of the first NAND gate NAND1; the power supply end of the first timer U1 is connected to the first DC power supply VDD, and is also grounded through the fifth capacitor C5; the base of the third transistor Q4 is connected to the field effect transistor Q4 through the twelfth resistor R12. The source of the transistor Q1 is connected, the collector is connected to the first DC power supply VDD through the fourteenth resistor R14, and the emitter is grounded; the base of the third transistor Q4 is also grounded through the thirteenth resistor R13, and the sixth capacitor C6 is connected in parallel with the thirteenth resistor R13; the grounding end of the second timer U2 is grounded, the trigger end is connected to the collector of the third transistor Q4, and is also grounded through the fifteenth resistor R15, and the seventh capacitor C7 is connected in parallel with the fifteenth resistor R15; the reset end of the second timer U2 is connected to the first DC power supply VDD through the sixteenth resistor R16, and is also grounded through the eighth capacitor C8; the second The threshold end of the timer U2 is grounded through the ninth capacitor C9, and the power end is connected to the first DC power supply VDD; the collector of the fourth transistor Q5 is connected to the reset end of the first timer U1, and is also connected to the anode of the second diode D2, the cathode of the second diode D2 is grounded through the seventeenth resistor R17, and the tenth capacitor C10 is connected in parallel with the seventeenth resistor R17; the base of the fourth transistor Q5 is connected to the anode of the third diode D3, the cathode of the third diode D3 is connected to the first DC power supply VDD through the nineteenth resistor R19, the emitter of the fourth transistor Q5 is grounded, and is connected through the tenth The eight resistors R18 are connected to the base of the fourth transistor Q5; the positive input terminal in+ of the photocoupler U3 is connected to a second DC power supply VCC, the negative input terminal in- is connected to the anode of the light-emitting diode D4, and the cathode of the light-emitting diode D4 is connected to the output terminal of the inverter NOT through the twentieth resistor R20; the input terminal of the inverter NOT is connected to the second DC power supply VCC through the twenty-first resistor R21; the negative output terminal out- of the photocoupler U3 is connected to the output terminal of the second timer U2, and the positive output terminal out+ is connected to the anode of the third diode D3. In this way, overcurrent protection can be achieved without stopping or restarting, and the working efficiency is high. ;

[0046] The above are only preferred embodiments of the present invention and are not intended to limit the protection scope of the present invention. Any modification, equivalent substitution or improvement within the spirit of the present invention is included in the scope of the claims of the present invention.

Claims

1. A driving circuit for a thyristor drawn arc welding machine, characterized in that: Including a rectifier bridge BR, a fuse FUSE, a welding gun electromagnetic coil L1, a field effect tube Q1, a first transistor Q2, a second transistor Q3, a third transistor Q4, a fourth transistor Q5, a first timer U1, a second timer U2, a photocoupler U3, a first NAND gate NAND1, a second NAND gate NAND2, an inverter NOT, a first diode D1, a second diode D2, a third diode D3, a light emitting diode D4, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12, and a thirteenth resistor R1 3. a fourteenth resistor R14, a fifteenth resistor R15, a sixteenth resistor R16, a seventeenth resistor R17, an eighteenth resistor R18, a nineteenth resistor R19, a twentieth resistor R20, a twenty-first resistor R21, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, and a tenth capacitor C10; a first input end of the rectifier bridge BR is connected to a positive electrode AC+ of an AC power source, and a second input end of the rectifier bridge BR is connected to a negative electrode AC- of the AC power source through a fuse FUSE; a first output end of the rectifier bridge BR is connected to a first end of a welding gun electromagnetic coil L1, and a second output end is grounded, and a first The resistor R1 is connected to the first output end of the rectifier bridge BR, and the second output end is also connected to the first output end through the first capacitor C1; the second end of the welding gun electromagnetic coil L1 is connected to the drain of the field effect tube Q1; the source of the field effect tube Q1 is grounded through the second resistor R2, and the gate is grounded through the third resistor R3; the ground end of the first timer U1 is grounded, and the output end is connected to the base of the first transistor Q2 and the base of the second transistor Q3 through the fourth resistor R4; the collector of the first transistor Q2 is grounded, and the emitter is connected to the gate of the field effect tube Q1 through the sixth resistor R6; the collector of the second transistor Q3 is connected to the reset end of the first timer U1 through the seventh resistor R7, and the emitter is connected to the emitter of the first transistor Q2; the first The output end of the timer U1 is also connected to the first end of the second capacitor C2 through the fifth resistor R5, and the second end of the second capacitor C2 is grounded; the control end of the first timer U1 is grounded through the third capacitor C3, the threshold end is grounded through the fourth capacitor C4 and is connected to the output end of the first NAND gate NAND1 through the eighth resistor R8; the output end of the first NAND gate NAND1 is also connected to a first DC power supply VDD through the ninth resistor R9, and the first input end and the second input end of the first NAND gate NAND1 are both connected to the first DC power supply VDD through the tenth resistor R10; the discharge end of the first timer U1 is connected to the first input end of the second NAND gate NAND2, and is also connected to the power supply end of the first timer U1 through the eleventh resistor R11;The second input end of the second NAND gate NAND2 is connected to the node between the fifth resistor R5 and the second capacitor C2, and the output end of the second NAND gate NAND2 is connected to the first input end or the second input end of the first NAND gate NAND1; the power supply end of the first timer U1 is connected to the first DC power supply VDD and is also grounded through the fifth capacitor C5; the base of the third transistor Q4 is connected to the source of the field effect transistor Q1 through the twelfth resistor R12, the collector is connected to the first DC power supply VDD through the fourteenth resistor R14, and the emitter is grounded; The base of the third transistor Q4 is also grounded through the thirteenth resistor R13, and the sixth capacitor C6 is connected in parallel with the thirteenth resistor R13; the grounding end of the second timer U2 is grounded, the trigger end is connected to the collector of the third transistor Q4, and is also grounded through the fifteenth resistor R15, and the seventh capacitor C7 is connected in parallel with the fifteenth resistor R15; the reset end of the second timer U2 is connected to the first DC power supply VDD through the sixteenth resistor R16, and is also grounded through the eighth capacitor C8; the threshold end of the second timer U2 is grounded through the ninth capacitor C9, and the power supply end is connected to the first DC power supply VDD. The collector of the fourth triode Q5 is connected to the reset terminal of the first timer U1, and is also connected to the anode of the second diode D2. The cathode of the second diode D2 is grounded through the seventeenth resistor R17. The tenth capacitor C10 is connected in parallel with the seventeenth resistor R17. The base of the fourth triode Q5 is connected to the anode of the third diode D3. The cathode of the third diode D3 is connected to the first DC power supply VDD through the nineteenth resistor R19. The emitter of the fourth triode Q5 is grounded and connected to the fourth triode Q5 through the eighteenth resistor R18. The positive input terminal in+ of the photocoupler U3 is connected to a second DC power supply VCC, the negative input terminal in- is connected to the anode of the light-emitting diode D4, and the cathode of the light-emitting diode D4 is connected to the output terminal of the inverter NOT through the 20th resistor R20; the input terminal of the inverter NOT is connected to the second DC power supply VCC through the 21st resistor R21; the negative output terminal out- of the photocoupler U3 is connected to the output terminal of the second timer U2, and the positive output terminal out+ is connected to the anode of the third diode D3. ; 2. The driving circuit of the thyristor drawn arc welding machine as claimed in claim 1, characterized in that: The second end of the welding gun electromagnetic coil L1 is also connected to the anode of the first diode D1, and the cathode of the first diode D1 is connected to the first end of the welding gun electromagnetic coil L1.

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