CN109877425B - IGBT contravariant multifunctional welding machine - Google Patents
IGBT contravariant multifunctional welding machine Download PDFInfo
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- CN109877425B CN109877425B CN201811492199.9A CN201811492199A CN109877425B CN 109877425 B CN109877425 B CN 109877425B CN 201811492199 A CN201811492199 A CN 201811492199A CN 109877425 B CN109877425 B CN 109877425B
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Abstract
The invention relates to an IGBT inversion multifunctional welding machine; the power supply is 220-240V single-phase, the inside of the welding machine is designed into a left-right structure, and one side of the welding machine is provided with a circuit board, a cooling fan and other components; the other side is provided with a wire feeding mechanism and other parts; the circuit board is designed into two blocks, namely an operation and nixie tube display control board, so that the selection and state indication of three welding methods can be realized; 2T/4T/VRD function selection and status indication; selecting and indicating states; parameter options and adjustment control thereof; display of parameters and unit or symbol indication; the main control board mainly comprises an inversion main circuit, a switching power supply circuit, an inversion PWM and IGBT driving circuit, a wire feeding and electromagnetic valve control circuit and an output characteristic control circuit; the welding machine provided by the invention has multiple functions, and solves the problems of narrow application range and poor welding operation interface of a single-function welding machine.
Description
Technical Field
The invention relates to a structure and a circuit of an IGBT inversion multifunctional welding machine; belongs to the technical field of inverter welding machines.
Technical Field
At present, the market competition of the inverter MIG/MAG gas shielded welder product is very strong, not only is the advancement and advantages of the technology embodied, but also the inverter MIG/MAG gas shielded welder product is greatly dependent on the aspects of the circuit of the welder, the function and structural design of the welder and the like.
In the markets at home and abroad, the rated current of the IGBT inverter MIG/MAG gas shielded welder is usually 160-650A (load duration rate is 100-35%). Most of the welding machine products are MIG/MAG gas shielded welding or manual welding functions of a single power supply, and the operation interface is too simple. The application range is limited to a certain extent.
For the multifunctional MIG/MAG gas shielded welding machine with the functions of manual arc welding, argon arc welding and the like, the applicability is stronger, so that the application range is wider. The product sales will be more competitive in the market. However, such welding machines have different circuit, circuit board and whole machine structural designs, different control principles and modes, different layout and connection modes of the circuit board and the whole machine, or different connection complexity, and completely different production procedures and manufacturing processes of products. These all affect the production and transportation costs of the product. For example, some welders on the market have control boards that are divided into several pieces that are individually secured to the frame. And each control panel is connected by a plurality of connecting wires. Not only needs to process a lot of control connecting wires, but also the circuit board occupies a large space, and the whole machine is large in size and heavy in weight. The manufacturing cost of the product is very high, and the market competitiveness of the product is weakened. The novel control technology is adopted to realize multifunction, nixie tube display and touch key operation, single encoder parameter setting is realized, the technical added value of the product is improved, and meanwhile, the cost is reduced, so that the product competition in the international market is facilitated. Therefore, on the premise of low cost, the development of multifunctional inverter welding machines with high technical content has a certain technical difficulty. This is also a problem to be solved by the present invention.
Disclosure of Invention
The welding machine has the functions of three welding methods of manual arc welding, argon arc welding and MIG/MAG gas shielded welding; the power supply is 220-240V single-phase; the inside of the device adopts a left layout structure and a right layout structure. One side is provided with a circuit board, a cooling fan and other parts; and the other side is provided with parts such as a wire feeding mechanism. And devices on the front and rear panels, such as a power switch, an operation and nixie tube display circuit board, a fan, an air inlet nozzle, an electromagnetic air valve, an output quick connector seat, an European type welding gun interface and the like are additionally arranged. For the control board circuit part, the circuit board is designed into two circuit boards, namely an operation and nixie tube display control circuit board and a main control board. The design is functionally that: the inverter main circuit consists of an input filter circuit, a power-on buffer circuit, an input rectifying and filtering circuit, four IGBT tubes and an inverter main transformer of capacitors C6-C9, C15-C16, Q3-Q7 and Q4-Q6, an output fast recovery diode rectifying and filtering reactor and the like; a switching power supply circuit; an inversion PWM and IGBT drive control circuit; control circuits such as wire feeding, electromagnetic valves and the like; an output characteristic control circuit; and a nixie tube display and operation control circuit and the like. The circuits are connected together according to the schematic circuit diagram relationship of the invention. Can meet various control requirements and state indication of three welding methods of manual welding, argon arc welding and MIG/MAG gas shielded welding. For example, by the circuit of the present invention, it is conveniently achieved that: 1) Function conversion of manual welding, argon arc welding and gas shield welding and indication of the state of an indicator lamp; 2) Control of output characteristics, parameter display, state indication and the like of manual welding and argon arc welding; 3) Manually welded VRD function control and VRD status indication; 4) The gas shielded welding wire inspection or test wire inspection and gas inspection or test gas inspection control and the indication lamp indication; 2T or 4T mode switching control of a welding gun switch and state indication of an indicator lamp; controlling the timing of gas supply in advance and gas closing in delay; flat characteristic output control; voltage, current or wire feed speed, inductance, burn-back time and wire diameter selection, adjustment, etc., and parameter unit indication. From the function of the circuit, the method mainly has the functions of generating a direct current power supply, regulating PWM pulse width, driving and controlling an IGBT tube, controlling the input and output welding parameters (such as current, voltage and the like) of an inverter circuit of three welding methods, selecting and controlling the welding methods, controlling the switch operation mode of a welding gun, controlling the display of a nixie tube and the like. Finally, under the action of a control circuit, the control performance requirements of three welding methods of manual arc welding, argon arc welding and MIG/MAG gas shielded welding are respectively realized. The method has obvious technical characteristics and performance advantages in similar products. In addition, the electronic components on the control circuit boards are mounted on the circuit boards in a large-size mode through automatic and small-amount manual plug-in. Many small-sized electronic components are directly mounted and soldered to the circuit board by means of automatic mounting. Therefore, the production and manufacturing process of the circuit board can be simplified, and the manufacturing cost is reduced. And secondly, the connection control lines between the circuit boards are reduced as much as possible, the production process and the production efficiency of the product are improved, and the whole machine is small in size and light in weight. That is, the design concept and the mode of the invention reduce the size of the product and the transportation cost. Meanwhile, series products with different specifications can be easily formed by adjusting a small number of parts (such as an inversion main transformer, an output reactor, an IGBT model and the like). Therefore, the welding machine provided by the invention has the advantages that the welding method is multifunctional, the operation interface is good, the comprehensive performance of the welding machine is improved, and the circuit principle, the circuit board and the whole machine structural design of the welding machine are unique.
The invention relates to an IGBT inversion multifunctional welding machine, which has three welding method functions of manual arc welding, argon arc welding and MIG/MAG gas shielded welding. And displaying by using a nixie tube and indicating the state of an LED indicator lamp, and operating by using a touch key. And parameter adjustment or setting is carried out by adopting a parameter selection key in combination with a single encoder.
The power supply of the welding machine is single-phase 220-240V, and the frequency is 50 or 60Hz.
The welding machine adopts a left layout structure and a right layout structure. And the left side is provided with parts such as a wire feeding mechanism, a wire feeding disc shaft and the like. The wire reel shaft is mounted on a middle partition plate inside the welding machine. The wire feeding mechanism is arranged on the bottom plate, is close to the front panel of the welding machine, and is connected with the European gas shielded welding gun seat arranged on the front panel. The other side of the right side is provided with parts such as a main control board, a cooling fan, a reactor and the like. And some circuits and devices on the front and back panels, such as a power switch, an operation and nixie tube display control circuit board, a fan, an air inlet nozzle, an electromagnetic air valve, an output quick connector seat, an European type welding gun interface and the like are additionally arranged. Inside the welder, the internal mechanical part of the welder is separated from the main control board part by a middle partition board. In this structure, the main control panel is surrounded by a metal casing composed of a middle partition, a casing, a bottom plate, a rear panel and a front panel. Can isolate electromagnetic interference and prevent electromagnetic radiation. In addition, the cooling air duct has better cooling air duct for power devices on the circuit board, such as a radiator, an IGBT tube, a fast recovery diode and the like, and better cooling is obtained, so that the working reliability of the welding machine is ensured.
The components mounted on the front panel of the welding machine mainly comprise: the welding gun comprises a copper head of an European type welding gun interface assembly, a black output quick connector assembly, a red output quick connector assembly and an operation and nixie tube display control panel.
For the operation and nixie tube display control panel part, the control panel is provided with a nixie tube display when seen from the outside of the welding machine. Below the display, there are provided: 1) A welding method of gas shielded welding (MIG)/argon arc welding (TIG)/manual welding (MMA) selects keys and corresponding indicator lamps. The gas shielded welding (MIG)/argon arc welding (TIG)/manual welding (MMA) function conversion button is used for selecting three corresponding welding methods and is provided with corresponding indicator lamps for indication; 2) A 2T (2 steps)/4T (4 steps)/VRD (no-load low voltage output at the time of manual welding) function selection button and corresponding indicator lamp. The 2T (2 steps)/4T (4 steps) mode gas shield welding gun switch conversion or VRD function selection buttons are used for gun switch operation mode and VRD function selection. The 2T mode is to start gas shielded welding by pressing a gun switch. And when the welding gun switch is loosened, the welding is stopped. The 4T mode is to start gas-shielded welding by pressing a gun switch, to continue welding by releasing the gun switch, to press the gun switch again, to finish welding, and to stop welding by releasing the gun switch. VRD refers to the selection of no-load low voltage output control in the manual welding (MMA) state. I.e. if MMA is selected, the VRD function can be selected. After the VRD is selected, if the welder is not performing a welding operation, i.e., is idling, the welder output voltage may be low, below 20 VDC. Thus, the welding machine can be used more safely; 3) And a wire detecting or testing wire/gas detecting or testing gas selecting button and a corresponding indicator lamp. The wire detection or test wire feeding function can be used for detecting whether wire feeding is normal or not during gas shielded welding, and can also be used for realizing slow or intermittent feeding of welding wires under the action of a control circuit during welding wire installation, so that the welding wires can be conveniently installed to extend out of the head of the welding gun. The gas detection or test gas supply function can be used for detecting whether gas supply is normal or not during gas shielded welding or can be used for matching with the flow regulation of a gas flowmeter; 4) Current, voltage units (e.g., A, V) indicator lights and wire feed symbol indicator lights.
On the right side of the display, there is provided: 1) A parameter option key; 2) A parameter adjustment encoder. In the case of a manual welding (MMA) method, the adjustable parameter is the welding current. Other welding parameters (such as arc striking current and thrust current) are set in a built-in way through control software, and the user is not required to adjust the welding parameters; in the case of selecting an argon arc welding (TIG) method, the adjustable parameter is the welding current; in the case of gas shielded welding (MIG) methods, the adjustable parameters are welding voltage, wire feed speed, wire diameter, re-ignition time of the welding arc at arc initiation.
A parameter "option" button for selecting the corresponding adjustable welding parameters for each welding method; and the welding parameter adjusting knob is used for adjusting the corresponding welding parameters under each welding method.
The overheat protection state indication is used to indicate whether an overheat state occurs. When the temperature of the internal device is too high and exceeds the action temperature of the temperature relay, on one hand, the overheat phenomenon can be displayed through the nixie tube under the action of the control circuit; alternatively, the welder may be stopped from welding or outputting. Under the condition that the welding machine does not output, the temperature of the heating device can be reduced due to the action of the cooling fan. When the temperature is reduced to the recovery action temperature of the thermal protector, the thermal protector is recovered, and the overheat phenomenon of the welding machine is eliminated. The overheat indication is not displayed. Meanwhile, the welding machine can be used for welding again. The design is convenient for the welder operator to select and use.
The parts installed on the rear panel of the welding machine mainly comprise a power switch, a power supply wire with a plug, a cooling fan, a protective gas inlet nozzle, an electromagnetic air valve, a welding machine grounding screw, a mark and the like. Cold air enters from an air inlet at the rear part of the welding machine case, so that some heating devices or parts on the circuit board have good cooling effect. The design of the air duct and the cooling mode is also one of the important reasons for realizing larger current of the welding machine.
For the control board circuit part, the circuit board is designed into two circuit boards, namely an operation and nixie tube display control circuit board and a main control board. The main design in terms of function is: the inverter main circuit consists of an input filter circuit, a power-on buffer circuit, an input rectifying and filtering circuit, four IGBT tubes and an inverter main transformer of capacitors C6-C9, C15-C16, Q3-Q7 and Q4-Q6, an output fast recovery diode rectifying and filtering reactor and the like; a switching power supply circuit; an inversion PWM and IGBT drive control circuit; control circuits such as wire feeding, electromagnetic valves and the like; an output characteristic control circuit; and circuits such as operation and nixie tube display control. The circuits are connected together according to the schematic circuit diagram relationship of the invention. Can meet various control requirements and state indication of three welding methods of manual welding, argon arc welding and MIG/MAG gas shielded welding. For example, by the circuit of the present invention, it is conveniently achieved that: 1) Manual welding, argon arc welding and gas shield welding function conversion and LED state indication of three methods; 2) Output characteristics and parameter display, current and voltage unit indication and other control of manual welding and argon arc welding; 3) Manually welded VRD function control and LED status indication; 4) The gas shielded welding wire inspection or test wire inspection and gas inspection or test gas inspection control and LED state indication; 2T or 4T mode conversion control and LED state indication of a welding gun switch; controlling the timing of gas supply in advance and gas closing in delay; flat characteristic output control; voltage, current or wire feed speed, inductance, burn-back time and wire diameter selection, adjustment, etc., and parameter unit indication. From the function of the circuit, the method mainly has the functions of generating a direct current power supply, regulating PWM pulse width, driving and controlling an IGBT tube, controlling the input and output welding parameters (such as current, voltage and the like) of an inverter circuit of three welding methods, selecting and controlling the welding methods, controlling the switch operation mode of a welding gun, controlling the display of a nixie tube and the like. Finally, under the action of a control circuit, the control performance requirements of three welding methods of manual arc welding, argon arc welding and MIG/MAG gas shielded welding are respectively realized. The method has obvious technical characteristics and performance advantages in similar products. In addition, the electronic components on the control circuit boards are mounted on the circuit boards in a large-size mode through automatic and small-amount manual plug-in. Many small-sized electronic components are directly mounted and soldered to the circuit board by means of automatic mounting. Therefore, the production and manufacturing process of the circuit board can be simplified, and the manufacturing cost is reduced. And secondly, the connection control lines between the circuit boards are reduced as much as possible, the production process and the production efficiency of the product are improved, and the whole machine is small in size and light in weight.
The welding machine with different current levels and load duration requirements can form products with different output rated currents and load duration by adjusting a small number of specification parameters of parts on a circuit board, so that the products are serialized. For example, changing the current level and heat sink size of the IGBT device; changing the model and parameters of the fast recovery diode; the specification, parameters and the like of the inversion main transformer and the output filter reactor are changed, so that series products with different specifications can be easily formed. Of course, these variations aim to match the manufacturing costs of the product with the specifications and performance indicators of the corresponding machine. In this way, optimal cost control can be achieved for each size welder. This promotes the market competitiveness of the developed product.
The welding machine provided by the invention has the use functions of three welding methods, so that the problems of narrow application area and poor operation interface of a single-function welding machine are solved, and the welding machine has better adaptability than a single-function welding machine. The good circuit and the structural design thereof are also the advantages of the invention, and are also important guarantees for meeting the requirements of high-efficiency and low-cost production, high reliability and advanced manufacturing technology. The circuit principle, the circuit board and the whole machine structural design of the welding machine have own unique points. The protection of the patent application is to protect the circuit and the structural design of the welding machine.
Drawings
FIG. 1 is a schematic illustration of an exemplary welder made with the present invention;
table 1 the names of the components in fig. 1 are as follows:
| numbering device | Name of the name |
| 1 | Handle |
| 2 | Handle |
| 3 | Door holder |
| 4 | Side cover plate |
| 5 | Welding gun interface of wire feeder |
| 6 | Wire feeder |
| 7 | Polarity-switching terminal I |
| 8 | Polarity switching binding post II |
| 9 | Wire feeding disc shaft |
| 10 | Middle partition board |
| 11 | Shell screw |
| 12 | Power switch |
| 13 | Wire fixing device |
| 14 | Power line |
| 15 | Electromagnetic air valve |
| 16 | Cooling fans or fans |
| 17 | Rear plastic mask |
| 18 | Shell bottom plate |
| 19 | Plastic wind scooper |
| 20 | Circuit board fixing support |
| 21 | Main control panel |
| 22 | Wind deflector |
| 23 | Hall sensor |
| 24 | Front plastic mask |
| 25 | Negative pole output quick-operation joint |
| 26 | Positive pole output quick-operation joint |
| 27 | Display and operation control circuit board |
| 28 | Fast recovery diode |
| 29 | Electrolytic capacitor |
| 30 | Rectifier bridge |
| 31 | Relay device |
| 32 | Driving transformer |
| 33 | IGBT |
| 34 | Auxiliary power supply transformer |
| 35 | Main transformer |
| 36 | Output reactor |
FIG. 2 is a schematic structural view of a main control panel portion of an exemplary welder of the present invention;
FIG. 3 is a schematic block diagram of the welder of the present invention;
FIG. 4 is a schematic diagram of the welder's operation and nixie tube display control circuitry of the present invention;
FIG. 5 is a schematic diagram of a portion of the power circuit on the main control board of the welder of the present invention;
FIG. 6 is a schematic diagram of a wire feed control circuit portion of the main control board of the welder of the present invention;
FIG. 7 is a schematic diagram of a Pulse Width Modulation (PWM) circuit portion on a welder main control board of the present invention;
FIG. 8 is a schematic diagram of a portion of a current, voltage, etc. parameter control circuit on a main control board of the welder of the present invention.
Detailed Description
As shown in fig. 1, fig. 2 and table 1. FIG. 1 is a schematic diagram of the structural design of an MIG/MAG gas shielded IGBT inverter welding machine with manual arc welding and argon arc welding functions. Table 1 is a main component list of the structural design schematic. Fig. 2 is a schematic structural view of a portion of the main control board 21 in an exemplary welder structure. The main components of the welding machine comprise:
1) And a wire feeding part. Mainly comprises the following steps: a wire reel shaft 9, a wire feeding mechanism 6, an European gas shielded welding gun interface copper head 5 and a wire feeding control circuit part on a main control panel for gas shielded welding. The wire feeder 6 and wire feed spool 9 are mounted on an inner intermediate plate 10. The wire feeder 6 is adjacent to the welder front panel 24. The wire feeding mechanism 6 is correspondingly connected with the European gas shielded welding gun interface copper head 5 arranged on the front panel 24. During gas shield welding, a gas shield welding gun is connected with the copper head 5 of the European gas shield welding gun interface in a matching way. The wire is mounted to the wire spool 9. The wire may be fed to the wire feeder 6 after installation. And then the copper head 5 is conveyed to the head of the welding gun connected with the copper head through the European gas shielded welding gun interface. The welding wire can be led out from the contact tip of the gas shielded welding gun under the control of the circuit through the wire feeding wheel and the pressing wheel of the wire feeding mechanism 6. During gas shielded welding, the wire feeding speed of the welding wire is controlled by the circuit board and the corresponding potentiometer. The welding current can be changed by adjusting the wire feeding speed. The protective gas interface on the copper head 5 of the European gas shielded welding gun interface is connected to the electromagnetic gas valve 15 through a gas pipe. The shielding gas is accessed from outside the welder to the gas input of the solenoid valve 15. After the gas cylinder is opened, under the control action of a welding machine circuit, the electromagnetic gas valve 15 can be turned on and off, so that the shielding gas is connected into the welding gun and flows out from the head of the welding gun, and the metal protection of a welding area is realized. When manual welding is performed, the wire feeding part is not controlled.
2) A housing portion. Comprises a handle 1, a casing 2, a door catch 3, a side cover plate 4 and a bottom plate 18, which contain foot pads on the bottom plate of the welding machine.
3) A rear plastic panel 17 portion. The parts installed on the back panel mainly comprise: the power switch 12, the power supply line 14, the line fixing device 13, the cooling fan 16, the air joint or the air inlet nozzle of the protection gas, the electromagnetic air valve 15 and the like. The power cord 14 is connected to a power supply grid. The power switch 12 controls the on or off of the welder power. The cooling fan 16 performs forced air cooling on some parts inside the welding machine. The cooling fan 16 is located at the rear of the welder and the cool air is taken from an air inlet at the rear of the rear panel of the welder cabinet. Some heating devices or parts of the upper part of the main control board 21, such as IGBT and radiator, fast recovery diode and radiator, etc. can be cooled well. The design of the air duct and the cooling mode is beneficial to guaranteeing the working reliability of a circuit of the welding machine, and is also one of important reasons for realizing larger current and high load persistence of the welding machine.
4) A front plastic panel 24 portion. The installed parts mainly comprise: the European style welding gun interface assembly copper head 5, a black output quick connector assembly 25, a red output quick connector assembly 26, an aviation socket, an operation and display control panel 27.
For the operation and nixie tube display control panel 27 portion, from the outside of the welder, there is provided: 1) A welding method of gas shielded welding (MIG)/argon arc welding (TIG)/manual welding (MMA) selects keys and corresponding indicator lamps. The gas shielded welding (MIG)/argon arc welding (TIG)/manual welding (MMA) function conversion button is used for selecting three corresponding welding methods and is provided with corresponding indicator lamps for indication; 2) A 2T (2 steps)/4T (4 steps)/VRD (no-load low voltage output at the time of manual welding) function selection button and corresponding indicator lamp. The 2T (2 steps)/4T (4 steps) mode gas shield welding gun switch conversion or VRD function selection buttons are used for gun switch operation mode and VRD function selection. The 2T mode is to start gas shielded welding by pressing a gun switch. And when the welding gun switch is loosened, the welding is stopped. The 4T mode is to start gas-shielded welding by pressing a gun switch, to continue welding by releasing the gun switch, to press the gun switch again, to finish welding, and to stop welding by releasing the gun switch. VRD refers to the selection of no-load low voltage output control in the manual welding (MMA) state. I.e. if MMA is selected, the VRD function can be selected. After the VRD is selected, if the welder is not performing a welding operation, i.e., is idling, the welder output voltage may be low, below 20 VDC. Thus, the welding machine can be used more safely; 3) And a wire detecting or testing wire/gas detecting or testing gas selecting button and a corresponding indicator lamp. The wire detection or test wire feeding function can be used for detecting whether wire feeding is normal or not during gas shielded welding, and can also be used for realizing slow or intermittent feeding of welding wires under the action of a control circuit during welding wire installation, so that the welding wires can be conveniently installed to extend out of the head of the welding gun. The gas detection or test gas supply function can be used for detecting whether gas supply is normal or not during gas shielded welding and can also be used for matching with the flow regulation of a gas flowmeter; 4) Current, voltage units (e.g., A, V) indicator lights and wire feed symbol indicator lights.
On the right side of the display, there is provided: 1) A parameter option key; 2) A parameter adjustment encoder. In the case of a manual welding (MMA) method, the adjustable parameter is the welding current. Other welding parameters (such as arc striking current and thrust current) are set in a built-in way through control software, and the user is not required to adjust the welding parameters; in the case of selecting an argon arc welding (TIG) method, the adjustable parameter is the welding current; in the case of gas shielded welding (MIG) methods, the adjustable parameters are welding voltage, wire feed speed, wire diameter, re-ignition time of the welding arc at arc initiation.
A parameter "option" button for selecting the corresponding adjustable welding parameters for each welding method; and the welding parameter adjusting knob is used for adjusting the corresponding welding parameters under each welding method. The overheat protection state indication is used to indicate whether an overheat state occurs.
When the temperature of the internal device is too high and exceeds the action temperature of the temperature relay, on one hand, the overheat phenomenon can be displayed through the nixie tube under the action of the control circuit; alternatively, the welder may be stopped from welding or outputting. Under the condition that the welding machine does not output, the temperature of the heating device can be reduced due to the action of the cooling fan. When the temperature is reduced to the recovery action temperature of the thermal protector, the thermal protector is recovered, and the overheat phenomenon of the welding machine is eliminated. The overheat indication is not displayed. Meanwhile, the welding machine can be used for welding again. The design is convenient for the welder operator to select and use.
5) The main control board comprises an inversion main circuit which consists of an input filter circuit, a power-on buffer circuit, an input rectifying and filtering circuit, capacitors C6-C9, C15-C16, Q3-Q7, Q4-Q6, an inversion main transformer, an output fast recovery diode rectifying and filtering reactor and the like; a switching POWER supply circuit (POWER section); an inverter PWM and IGBT drive control circuit (MIG 140 section); control circuits (mot parts) for wire feeding, solenoid valves and the like; and an output characteristic control circuit (control section). Specific circuits and parts thereof are shown in the related figures 3 and 5-8.
6) And an operation and nixie tube display control circuit board. As shown in fig. 3 and 4. An operating and nixie tube display control circuit board 27) which is connected to the other circuit parts of the welder by a CON7 plug (corresponding to the CON1 plug in fig. 4) in fig. 3. On the nixie tube display and operation control circuit board 27), the circuit mainly comprises a U2 microprocessor (STM 32F103RCT 6), common anode nixie tubes DS1 and DS2, a Gas check key K2, a TIG (argon arc welding)/MMA (manual welding)/MIG (Gas shielded welding) welding method selection key K3, a 2T/4T welding gun switch operation mode, a VRD function selection key K4, a Parameters Selection (parameter option) key K6, a BMQ parameter adjustment encoder K1 and an air supply control optocoupler U3 (a signal terminal is SQ). When air is supplied, the SQ signal is at a high level), and an optocoupler U4 (the signal terminal is SS) for controlling wire supply. When wire feeding, SS signal is low level), overheat or overcurrent detection and control circuit (signal terminal is OC), IND inductance parameter adjustment control circuit (including KR 1-KR 3 relay and its peripheral components. The relays may be operated individually or two or three relays may be operated simultaneously. By controlling the different relay actions, the corresponding series resistance values are different, so that they adjust for different di/dt (current rate of change), which is indicative of the corresponding inductance IND values being different. Eight combinations of actions of the relay are provided, so that the inductance IND value can be changed between 1 and 8. ) The voltage detection circuit (the signal terminal is UDP), the current detection circuit (the signal terminal is IDP), the PWMU output voltage conversion circuit (the output of which is a Ug voltage given control signal), the output current conversion circuit (the output of which is an IgOUT current given control signal), the output voltage conversion circuit (the output of which is a UgOUT voltage given control signal) and the like. The function of this partial circuit is: 1) Three welding methods of TIG (argon arc welding)/MMA (manual welding)/MIG (gas shielded welding) are selected and controlled. And the U2 microprocessor control system realizes the conversion and control of three welding methods by detecting the state of the key K3. And each time the K3 key is pressed, a welding method is changed. And when the key is operated for a plurality of times, different welding methods are sequentially and circularly changed. When MMA is selected, the MMA-EN terminal signal is high, and the MIG-EN terminal signal is low. When MIG is selected, the MMA-EN terminal signal is low, and the MIG-EN terminal signal is high. GUN-CHECK is used for detecting a welding GUN switch signal. By detecting, it can be confirmed whether the gun switch is pressed. When MIG welding is performed, if a welding gun is pressed, the welding process requirements of MIG welding or gas shielded welding are correspondingly controlled. For example, controlling the delivery of a shielding gas; controlling wire feeding or welding current; controlling output voltage of a welding machine and the like; 2) And 2T/4T welding gun switch operation mode and VRD function selection control are realized. And the U2 microprocessor control system realizes the switching operation mode and VRD function conversion of two (2T and 4T) welding guns by detecting the state of the key K4. Under the condition that the gas shield welding method is selected, the operation mode of the 2T or 4T welding gun switch is changed once every time the K4 key is pressed. And when the key is operated for a plurality of times, the key is changed in sequence and circularly. The VRD (low no-load voltage output when the welder is not welding) function is set only for the manual welding method. That is, only when the manual welding method is selected, the VRD function can be selected through the K4 key. When the manual welding method is selected, but the VRD function is not selected, the welding machine outputs higher no-load voltage when no-load. Otherwise, outputting low voltage when the VRD is output; 3) The selection and control of the Gas check and the Wire check are realized. Under the condition of selecting the Gas shielded welding method, the microprocessor control system realizes the conversion of Gas check or Wire check by detecting the state of the key K2. Each time the K2 key is pressed, a detection mode is changed; 4) The selection of the corresponding welding parameters (the selection is realized through a Parameters Selection parameter selection key K6) and the adjustment control (when the parameter items are selected, the BMQ encoder K1 is used for carrying out specific parameter adjustment) under each welding method are realized. Under each selected welding method, the corresponding welding parameters of the welding method can be changed through Parameters Selection parameter option keys K6 and BMQ parameter adjustment encoders K1. For example, in the case of selected manual welding or argon arc welding, the corresponding welding parameters are only welding currents. The output current (parameter) during welding can be changed by adjusting the BMQ encoder K1. In the case of selecting a gas shield welding method, the welding parameters that can be selected are: the welding wire diameter (three welding wires of 0.6, 0.8 and 1.0 mm), inductance (IND value can be selected between 1 and 8), arc characteristics during gas-shielded welding can be influenced by changing inductance parameters, so that the welding process, stability, splashing and weld seam forming can be changed), fine adjustment of welding voltage (can be changed between +/-5V of standard values), welding voltage and welding current or wire feeding speed are set in a unified adjustment mode, namely, the wire feeding speed or welding current is changed, the corresponding welding voltage standard value can be changed accordingly, the fine adjustment of the welding voltage can play a role of increasing or reducing on the basis of the standard values; 5) The display of various states, parameters and units of the welding machine can be realized. Under the control of the microprocessor control system, the following can be displayed: welding current and symbol (A) thereof during manual welding, or welding current and symbol (A) thereof; welding current and sign (A) of the welding current during argon arc welding; welding current and sign (A) or wire feeding speed and sign, voltage and sign (V) during gas shield welding. That is, under the control of the U2 microprocessor control system, the LED of the corresponding welding method symbol (e.g. TIG, MMA, MIG) in the three welding methods can be lightened. For example, VD5 when illuminated, represents the selection of MIG (gas shielded welding). When VD6 is on, TIG (argon arc welding) is selected. VD7 when lit, represents MMA (manual welding or manual arc welding) selected; welding current and sign (a) thereof, or welding current and sign (a) thereof and VRD function sign when manual welding. When VD3 is on, the unit indicating the display parameter is "a" (amperes). When VD10 is on, the VRD function (low no-load voltage output function at the time of manual welding) is selected; welding current and sign (A) of the welding current during argon arc welding; and parameters such as welding current and sign (A), voltage and sign (V) and the like during gas shielded welding. When VD4 is on, the unit indicating the display parameter is "V" (volt). Further, VD8 when illuminated, represents a 2T gun switch mode of operation selected. VD9 when illuminated, represents a 4T gun switch mode of operation was selected. When VD11 is on, this represents the selection of Gas Check operation. When VD11 is on, wire Check operation is selected. VD1, when illuminated, represents the selection of the IND (inductance) parameter option. When VD2 is on, a SPEED parameter option is selected on behalf of the user; 6) And the detection and output conversion control of current and voltage real-time welding parameters are realized. IDP represents the actual current signal from the output current detection circuit. UDP represents the actual current signal from the output voltage detection circuit. The U2 microprocessor control system is used for controlling the output characteristics of the welding machine by detecting given welding parameters and finally outputting control parameters, and converting the control parameters into UgOUT voltage given control signals and IgOUT current given control signals of analog quantities through respective conversion circuits; 7) Overheat and overcurrent detection and control are realized. When an overheat or overcurrent abnormality is detected, the OC terminal signal of fig. 5 is low. Otherwise, no abnormality occurs. And the microprocessor control system judges whether the welding machine has overheat or overcurrent by detecting the OC or ICS signals. If the abnormal condition exists, a corresponding control signal is sent out to perform corresponding control and display. For example, the signal of the Tc connection CON8 interface in fig. 3 is an overheat signal. The CON8 interface is connected to a normally open temperature relay. And the temperature relay is tightly attached to an aluminum alloy radiator of the Q3-Q7 IGBT or the D7-D12 output fast recovery diode. And when the temperature relay acts, the overheat phenomenon of the main power device is indicated. At this time, in fig. 8, tc is pulled down to low level (GND), and at the same time, the control circuit turns off PWM signal PWM-STOP; the OC/OT end sends corresponding signals to the panel display and operation control interface circuit, and the welding machine output or welding work is stopped through the detection and control of the display and operation control circuit, so that the welding machine is prevented from being burnt out due to overheat. Under the effect of the cooling fan, when the temperature of the aluminum alloy radiator is reduced to a certain degree, the overheating phenomenon in the welding machine is eliminated, and when the thermal protector is recovered, the control circuit can continue to output PWM control signals. While the overheat indication is eliminated. This achieves overheat protection of the welder.
As shown in fig. 1 and in table 1. The welder of the present invention, two sets of output quick connector assemblies 25, 26) are used to connect electrode holder cables and workpiece holder cables, respectively, during manual arc welding. The polarity during connection can be used for determining the connection mode according to the type and the requirement of the welding rod. Red, representing a positive output; black, representing a negative output; in argon arc welding, the argon arc welding gun is connected to a negative polarity output quick connector assembly 25, while a positive polarity output quick connector assembly 26 is connected to the workpiece being welded. The air pipe of the welding gun is connected to the air supply system through an externally connected air pipe; the welding gun is connected to the copper head 5 of the European welding gun interface assembly during gas shield welding. The black output quick connector assembly 25 is typically used to connect a workholder weld cable. This connection is called a reverse connection or reverse polarity connection. Of course, since the red binding post 8 and the black binding post 7 are respectively connected to the positive and negative polarity ends of the output of the circuit board inversion main circuit, the positive polarity connection mode conversion of the welding output can be realized by using the two binding posts through the wiring position exchange of the internal connecting wires of the welding machine. Whether reverse connection or reverse polarity connection or positive connection is adopted depends on the type of the gas shielded welding wire and the requirements of the welding process.
If the components on the circuit board of the welding machine are plug-in type electronic components or parts, the automatic and manual plug-in and welding modes are mainly adopted to finish the processing of the circuit board. And for a large number of patch type electronic components on the circuit board, the automatic patch and welding modes are all adopted to finish the processing of the circuit board. It is supposed that if all components and parts are not of a patch type, the size of the circuit board is necessarily large. This increases the size and weight of the welder; if there are many control connection lines between circuit boards like other welding machines with multiple circuit board structures, the manufacturing process is necessarily more and the production process is complex. The invention fully considers the influence factors. Through repeated design, the circuit board has small size, compact structure and less connection control lines, so the circuit board of the welding machine has less production and processing procedures, greatly simplifies the manufacturing process and is more convenient to produce. The design and the processing technology can ensure that the production of the product has high production efficiency, and simultaneously, the error rate and the manufacturing cost are low, thereby being beneficial to improving the market competitiveness of the product.
In addition, in terms of structural design, as shown in fig. 1, the inner left mechanical part of the welder is separated from the right main board circuit part by a middle partition plate. The main control board circuit on the right side is surrounded by a case composed of a middle partition board, a case, a bottom board, a rear panel and a front panel. Can isolate high-current strong electromagnetic interference, limit electromagnetic radiation and improve the reliability of the welding machine.
The drawings 3-8 together form a complete control circuit schematic diagram of the welding machine. The control circuit boards are additionally provided with a plurality of connecting control wires and parts, and are connected together according to a circuit schematic diagram. From the control function of the related circuit, the invention mainly completes the work of input filtering, the generation of the direct current voltage-stabilizing power supply of each circuit, the selection and control of welding methods, the operation of 'wire inspection' or 'wire test', 'gas inspection' or 'gas test', PWM pulse width adjustment, IGBT tube driving and inversion control, output rectification conversion, the control of the output parameters (current or wire feeding speed, voltage) of the inversion circuit corresponding to the three welding methods, and the like. Finally, under the action of a control circuit, the control requirements of manual arc welding (MMA), argon arc welding (TIG) and MIG/MAG gas shielded welding are respectively realized.
The working principle of the welder circuit of the invention is briefly described as follows:
as shown in fig. 1 and 3. The main circuit of the welding machine mainly comprises a power input switch S1, an input filter circuit, a power-on buffer circuit, a rectifier DB1, filter electrolytic capacitors C8-C9, capacitors C6-C7 and C15-C16, four IGBT tubes Q3 and Q7 and Q4 and Q6, a main transformer T1, a main transformer primary current detection transformer L3, six MU6030 fast recovery diodes D7-D12, an output current filter inductor L2, an output Hall current detection sensor (current sensor), a plurality of input and output resistors, input and output filter capacitors, anti-interference capacitors, resistors and other parts and electronic components.
Referring to fig. 3, 220V to 240V input power supply voltage is connected to a power supply switch S1. The power supply of the power grid is connected through a power switch S1 on the rear panel of the welding machine. Alternating current from a power grid firstly passes through an input filter circuit consisting of resistors R1-R2 and capacitors C2-C3. The circuit has the main effects of reducing the interference of a power grid power supply to the circuit of the inverter welding machine and improving the working reliability of the welding machine.
Referring to fig. 3, the input ac power is rectified by a rectifier DB1 to become pulsating dc power after passing through a power-on buffer circuit portion composed of elements such as RR1 and RR2 thermistors, a relay K1, a field effect transistor Q1, a diode D2, a voltage regulator D3, and the like. And charging the C8-C9 electrolytic capacitors, gradually increasing the voltage, and finally changing the capacitor into a relatively stable high-voltage direct current.
Referring to fig. 3, after rectifying by a rectifier (30) DB1 and filtering by an electrolytic capacitor, the obtained high-voltage direct current is supplied to an inversion main circuit composed of four IGBT tubes (such as K75T 60) of capacitors C6 to C9 and C15, Q3 and Q7 and Q4 and Q6, a T1 inversion main transformer and D7 to D12 (such as MU 6030) fast recovery diodes, an L2 output current filter reactor or inductor, an output hall current detection sensor (400A/4 v) and the like. The functions of the device are mainly as follows: the high-voltage direct-current bus voltage is converted into medium-frequency (tens of KHz) alternating current. The T1 inversion main transformer realizes voltage reduction and conversion of high-current output. The fast recovery diode D7-D12 (such as MU 6030) converts the medium frequency alternating current output by the inverter transformer into direct current. Because the current waveform transformed by the method is pulsating and unstable, the stability of the welding process is not facilitated, and therefore, an L2 output current filter reactor or inductor is adopted for filtering. The output current waveform becomes stable, which is beneficial to obtaining high-quality welding seams.
On the other hand, referring to fig. 3, a high-voltage dc bus voltage is supplied to the switching POWER supply circuit (in fig. 3, there is a green circuit portion of the POWER letter) through the plug CON 1. The schematic diagram of the specific switching power supply is shown in fig. 5. The working principle of this part of the switching power supply is briefly described here. The switching power supply circuit is composed of a T3 switching power supply transformer, a Q30 MOS tube, D83, D85-D87 fast diodes, U16 (UC 3845 integrated PWM circuit), U18-U20 integrated voltage stabilizer, resistors, capacitors and other devices around the U18-U20 integrated voltage stabilizer, and generates +5V, +15V, +24V, -15V power supply voltages which are supplied to other corresponding control circuits and the like for electrified work. The input power is connected to the high voltage dc bus voltage +310V. Therefore, the circuit composed of UC3845 controlled by the PWM of the switching power supply U16 and peripheral resistance and capacitance thereof belongs to a high-voltage loop. In order to ensure the safety of the control circuit, in fig. 5, a PC817 photo coupler of U17 is used for isolation. The core control chip of the switching power supply PWM control small board is U16, namely UC3845 PWM pulse width regulator. The peripheral resistance and capacitance can set the relevant parameters of the operation. As to how to determine, a view of relevant usage information or instructions for UC3845 is required. And will not be repeated here. In a word, the pulse output by the 6 pins of the U16 chip is a driving pulse with a certain working frequency, so that the Q30 MOS tube in fig. 5 is in an on-off working state. In the voltage output circuit part of the T3 switching power supply transformer, +5V, +15V, +24V and-15V power supply voltages are obtained respectively. For other control circuits to work. In addition, as can be seen from the circuit and schematic diagram of the switching power supply, the present invention does not employ a conventional control transformer and associated voltage conversion circuitry to generate the several power supply voltages. The circuit takes power from the high-voltage direct-current bus voltage +310V in the main loop. The size, the dimension and the weight of the switch transformer are far smaller than those of a common control transformer, so that the cost of the welding machine is reduced, and the technical added value of the welding machine is improved.
In fig. 3, the power-on buffer circuit part is composed of components such as RR1 and RR2 thermistors, a relay K1, a field effect transistor Q1, a diode D2, a voltage stabilizing tube D3 and the like. The operation time of the K1 relay is delayed from the closing time of the power switch S1. I.e. the K1 relay is time-lapse operated. When the charging voltage on the C8-C9 electrolytic capacitor is stable, the K1 relay acts, and the contacts close the RR1 and RR2 thermistors, so that the heavy current flows between the contacts 3-4 of the K1 relay when the welding machine works in normal inversion. Such a circuit is called a power-on buffer circuit. Mainly prevents the power switch from being turned on instantly, and because the C8-C9 electrolytic capacitor has no voltage, which is equivalent to short circuit, a larger surge current is formed to burn the power switch S1. The power-on buffer circuit has the function of limiting surge current by connecting the thermistors RR1 and RR2 in series in the moment of closing. The resistance values of the RR1 and RR2 thermistors increase as the temperature increases. Therefore, the power-on buffer circuit can play a better role in protection. The power-on buffer part circuit is realized by the following control mode: in fig. 3, the +24v voltage is developed later than when the welder power switch S1 is turned on. The voltage across capacitor C5 is stepped up after the +24v voltage is applied. Because R6 and C5 constitute an integrating circuit. When the voltage on the capacitor C5 rises to a certain value, the MOS transistor Q1 can be turned on. Thus, the K1 relay will operate.
Referring to fig. 3 and 7, the T2 driving transformer, the U13 integrated PWM chip (SG 3525A), and diodes, voltage stabilizing tubes, resistors, capacitors, etc. around the same constitute the inverter PWM, driving circuit and overcurrent and overheat protection control circuit parts of the Q3 and Q7 and Q4 and Q6 IGBT tubes. The circuit forms of the Q3 and Q7 and the Q4 and Q6 IGBT tubes and the two driving parts are basically identical. Because the PWM signals output by the 11 pin and the 14 pin of the U13 chip have small driving power, the power amplification is needed to be carried out through a driving control circuit formed by devices such as Q26-Q29, U14 and U15. And then the T2 drives the isolation transformer to control the on-off working states of the Q3 and Q7 and Q4 and Q6 IGBT tubes. In fig. 7, the output control signals of pins 11 and 14 of the U13 chip are two sets of PWM square wave pulse signals. The square wave frequency is fixed, with tens of KHz. It is determined by the resistor and capacitor parameters (e.g., R171 and C83, etc.) of the RT, CT pin connections of the chip. The two sets of square wave pulse signals have a fixed time difference in time, also known in the art as dead time. The method is one of important parameters for ensuring the alternate work of the two groups of switches of the IGBT. This time is determined by the peripheral device (e.g., R171 and C83, etc.) parameter settings of the U13 chip. As to how to determine, it is known to look at the relevant usage information or instructions of the U13 chip. And will not be repeated here. What needs to be explained here is: the PWM pulse width modulation signal output by the U13 chip is a signal for determining the output voltage and current of the welding machine inverter main circuit. Its pulse width depends on: 1) The manual welding (MMA) control state is determined by a welding current given signal and an output current feedback signal. The object or target of the control is the output current magnitude. At idle, the feedback signal is small. The control circuit generates a PWM pulse signal with larger duty ratio, so that two groups of IGBTs (insulated gate bipolar transistors) Q3 and Q7 and Q4 and Q6 are in an alternate conduction state, and finally the inverter main circuit outputs no-load voltage. When the operator adjusts the potentiometer of the welding current on the front panel and performs welding, the control circuit can detect the output current signal through the hall sensor (400A/4 v) in fig. 3. In one aspect, an output current signal is obtained for display by a welder ammeter. The digital display of the current is effected under the influence of other control circuits, mainly the operating and display control circuits of the parts of figures 3 and 4. On the other hand, the detected current signal is subjected to signal amplification or the like by other control circuits (mainly, the output characteristic control circuits of fig. 3 and 8), and is used as a current negative feedback control signal to be compared with a welding current given signal. And (3) comparing the difference signals, performing PI (proportion and integral) regulation control, and controlling the pulse width or duty ratio of the output PWM chip of the welding machine by the output result to determine the output current and voltage of the welding machine, so as to realize accurate control of the output current parameters. And the output characteristic of the welder is the falling characteristic of the constant current belt out-of-band pull. Further, when the welding current given signal is unchanged, the current detected by the welder circuit increases, and after the given set value is reached, the difference value between the welding current given signal and the current negative feedback control signal decreases along with the current increase, and after PI control, the pulse width or duty ratio of the welder output PWM chip decreases, and the output voltage of the welder decreases. This process is called current cut-off negative feedback control. I.e. a feedback control that only works after the current has reached the set point of the welding current potentiometer. Thereafter, the voltage drops much with a small increase in current. When the voltage is reduced to below 16V, the control circuit can increase the pulse width or duty ratio of the output PWM chip of the welding machine along with the reduction of the voltage, so that the welding current is increased according to the set parameters, and finally the reducing characteristic of the constant current out-of-band pull is formed. The current cutoff negative feedback set point is different when the welding current given signal changes, but the other control processes are similar. In this way, between the minimum and maximum settings of the potentiometer, a myriad of drop characteristics are obtained. Such control is also essential to meet the requirements of manual arc welding. 2) In the argon arc welding (TIG) control state, the control process is very similar to that of the manual welding. The output characteristic of the welder is set to be constant current drop characteristic without performing the pull-out stage control of 16V or less. 3) In the gas shield welding control state, the given welding voltage signal and the feedback output voltage signal are determined together. The object or target of the control is the output voltage magnitude. And voltage negative feedback PI control is adopted. When no load is applied, similar to manual welding control, a larger PWM pulse width signal is still output, and no-load voltage is obtained. After loading, the control is different from that of manual welding. The output characteristic control of the gas shield welding machine is flat, but not the descending characteristic of constant current out-of-band dragging. The method is characterized in that: the load current changes greatly, while the output voltage changes little, and remains relatively stable. Only when a given voltage signal changes will the output voltage change significantly. The above control process is realized by a corresponding control circuit.
Referring to fig. 3 and 7, L3 is a primary current detecting transformer or current detector for detecting primary current signals of the main transformer in the inverter main circuit. The outputs LP1 and LP2 are sent to control circuits such as inverted PWM pulse width modulation and IGBT driving (fig. 3 shows the green part of MIG140, and the specific circuit is shown in fig. 7). It is mainly to check if the inversion main circuit has over-current phenomenon. If overcurrent occurs, the overcurrent indicator lamp VD in fig. 7 is turned on; VS1 (SCR thyristor) is conducted, the cathode potential of D77 diode is pulled down to low level (GND), triode Q24 is cut off, Q25 is conducted, PWM signals output by pins 11 and 14 of U13 chip are closed, driving control signals of four IGBT tubes Q3 and Q7 and Q4 and Q6 in the inverter main circuit of the welding machine are closed, and the welding machine is closed for output. Meanwhile, the nixie tube of the panel can indicate overheating phenomenon; the OC/OT terminal also sends out a corresponding signal.
In fig. 3 and fig. 7, the control circuit parts (in fig. 3, the green part of MIG140 is shown in fig. 7) of the inversion PWM pulse width modulation and the IGBT driving, and the outputs G1 and E1, G2 and E2 are two groups of PWM pulse signals respectively, so as to control the on-off states of two groups of IGBT switching tubes of Q3 and Q7 and Q4 and Q6 in the inversion main circuit. The pulse width of the PWM signal is controlled by the PWM-GD input given signal. The presence or absence of a PWM signal depends on PWM-STOP and Tc. For example, the signal of the Tc connection CON8 interface in fig. 3 is an overheat signal. The CON8 interface is connected to a normally open temperature relay. And the temperature relay is tightly attached to the aluminum alloy radiator of the Q3, Q7 IGBT or D7-D12 output fast recovery diode. And when the temperature relay acts, the overheat phenomenon of the main power device is indicated. At this time, in fig. 7, tc is pulled down to low level (GND), and at the same time, the control circuit turns off the PWM signal; the OC/OT end sends corresponding signals to the panel display and operation control interface circuit, and the display and operation control circuit detects and controls the display and operation control circuit to enable the nixie tube on the panel to indicate overheating. Preventing the welding machine from burning out due to overheat. Under the effect of the cooling fan, when the temperature of the aluminum alloy radiator is reduced to a certain degree, the overheating phenomenon in the welding machine is eliminated, and when the thermal protector is recovered, the control circuit can continue to output PWM control signals. While the overheat indication is eliminated. This achieves overheat protection of the welder. The PWM-STOP is derived from the current, voltage and output characteristic control circuit (see fig. 8). When the welder does not output voltage or current, the PWM-STOP signal can close the PWM signal, so that the two groups of IGBT switching tubes Q3 and Q7 and Q4 and Q6 in the inversion main circuit are in an off state.
As shown in fig. 3 and 4. The operating and nixie tube display control circuit board is connected with other circuit parts of the welding machine through a CON7 plug (corresponding to the CON1 plug in fig. 4) in fig. 3. On a nixie tube display and operation control circuit board, the circuit mainly comprises three welding method selection keys K3, 2T/4T welding gun switch operation mode and VRD function selection keys K4 and Parameters Selection (parameter option) keys K6, a BMQ parameter adjustment encoder K1, an optocoupler U3 for controlling air supply (when a signal terminal is SQ. air supply, SQ signals are high level), an optocoupler U4 for controlling air supply (when a signal terminal is SS. air supply, SS signals are low level), an overheat or overcurrent detection and control circuit (when a signal terminal is OC) and an IND inductance parameter adjustment control circuit (comprising KR 1-KR 3 relays and peripheral components thereof), by controlling the operation of different relays, the corresponding series resistance values are different, so that the relays regulate different di/dt (current change rate), and the different current change rates represent that the corresponding inductance IND values are different, eight types of relay operation combination modes exist, thus the inductance IND values can be changed between 1 and 8), a voltage detection circuit (the signal terminal is UDP), a current detection circuit (the signal terminal is IDP), a PWMU output voltage conversion circuit (the output of which is Ug voltage given control signal), an output current conversion circuit (the output of which is IgOUT current given control signal), a voltage conversion circuit (the output of which is IgOUT current given control signal), an output voltage conversion circuit (the output of which is a UgOUT voltage given control signal), and the like. The function of this partial circuit is: 1) Three welding methods of TIG (argon arc welding)/MMA (manual welding)/MIG (gas shielded welding) are selected and controlled. And the U2 microprocessor control system realizes the conversion and control of three welding methods by detecting the state of the key K3. And each time the K3 key is pressed, a welding method is changed. And when the key is operated for a plurality of times, different welding methods are sequentially and circularly changed. When MMA is selected, the MMA-EN terminal signal is high, and the MIG-EN terminal signal is low. When MIG is selected, the MMA-EN terminal signal is low, and the MIG-EN terminal signal is high. GUN-CHECK is used for detecting a welding GUN switch signal. By detecting, it can be confirmed whether the gun switch is pressed. When MIG welding is performed, if a welding gun is pressed, the welding process requirements of MIG welding or gas shielded welding are correspondingly controlled. For example, controlling the delivery of a shielding gas; controlling wire feeding or welding current; controlling output voltage of a welding machine and the like; 2) 2T/4T welding gun switch operation mode and VRD function selection and control are realized. And the U2 microprocessor control system realizes the switching operation mode and VRD function conversion of two (2T and 4T) welding guns by detecting the state of the key K4. Under the condition that the gas shield welding method is selected, the operation mode of the 2T or 4T welding gun switch is changed once every time the K4 key is pressed. And when the key is operated for a plurality of times, the key is changed in sequence and circularly. The VRD (low no-load voltage output when the welder is not welding) function is set only for the manual welding method. That is, only when the manual welding method is selected, the VRD function can be selected through the K4 key. When the manual welding method is selected, but the VRD function is not selected, the welding machine outputs higher no-load voltage when no-load. Otherwise, outputting low voltage when the VRD is output; 3) The selection and control of the Gas check and the Wire check are realized. Under the condition of selecting the Gas shielded welding method, the microprocessor control system realizes the conversion of Gas check or Wire check by detecting the state of the key K2. Each time the K2 key is pressed, a detection mode is changed; 4) The selection of the corresponding welding parameters (the selection is realized through a Parameters Selection parameter selection key K6) and the adjustment control (when the parameter items are selected, the BMQ encoder K1 is used for carrying out specific parameter adjustment) under each welding method are realized. Under each selected welding method, the corresponding welding parameters of the welding method can be changed through Parameters Selection parameter option keys K6 and BMQ parameter adjustment encoders K1. For example, in the case of selected manual welding or argon arc welding, the corresponding welding parameters are only welding currents. The output current (parameter) during welding can be changed by adjusting the BMQ encoder K1. In the case of selecting a gas shield welding method, the welding parameters that can be selected are: the welding wire diameter (three welding wires of 0.6, 0.8 and 1.0 mm), inductance (IND value can be selected between 1 and 8), arc characteristics during gas-shielded welding can be influenced by changing inductance parameters, so that the welding process, stability, splashing and weld seam forming can be changed), fine adjustment of welding voltage (can be changed between +/-5V of standard values), welding voltage and welding current or wire feeding speed are set in a unified adjustment mode, namely, the wire feeding speed or welding current is changed, the corresponding welding voltage standard value can be changed accordingly, the fine adjustment of the welding voltage can play a role of increasing or reducing on the basis of the standard values; 5) The display of various states, parameters and units of the welding machine can be realized. Under the control of the microprocessor control system, the following can be displayed: welding current and symbol (A) thereof during manual welding, or welding current and symbol (A) thereof; welding current and sign (A) of the welding current during argon arc welding; welding current and sign (A) or wire feeding speed and sign, voltage and sign (V) during gas shield welding. That is, under the control of the U2 microprocessor control system, the LED of the corresponding welding method symbol (e.g. TIG, MMA, MIG) in the three welding methods can be lightened. For example, VD5 when illuminated, represents the selection of MIG (gas shielded welding). When VD6 is on, TIG (argon arc welding) is selected. VD7 when lit, represents MMA (manual welding or manual arc welding) selected; welding current and sign (a) thereof, or welding current and sign (a) thereof and VRD function sign when manual welding. When VD3 is on, the unit indicating the display parameter is "a" (amperes). When VD10 is on, the VRD function (low no-load voltage output function at the time of manual welding) is selected; welding current and sign (A) of the welding current during argon arc welding; and parameters such as welding current and sign (A), voltage and sign (V) and the like during gas shielded welding. When VD4 is on, the unit indicating the display parameter is "V" (volt). Further, VD8 when illuminated, represents a 2T gun switch mode of operation selected. VD9 when illuminated, represents a 4T gun switch mode of operation was selected. When VD11 is on, this represents the selection of Gas Check operation. When VD11 is on, wire Check operation is selected. VD1, when illuminated, represents the selection of the IND (inductance) parameter option. When VD2 is on, a SPEED parameter option is selected on behalf of the user; 6) And the detection and output conversion control of current and voltage real-time welding parameters are realized. IDP represents the actual current signal from the output current detection circuit. UDP represents the actual current signal from the output voltage detection circuit. The U2 microprocessor control system is used for controlling the output characteristics of the welding machine by detecting given welding parameters and finally outputting control parameters, and converting the control parameters into UgOUT voltage given control signals and IgOUT current given control signals of analog quantities through respective conversion circuits; 7) Overheat and overcurrent detection and control are realized. When an overheat or overcurrent abnormality is detected, the OC terminal signal of fig. 5 is low. Otherwise, no abnormality occurs. And the microprocessor control system judges whether the welding machine has overheat or overcurrent by detecting the OC or ICS signals. If the abnormal condition exists, a corresponding control signal is sent out to perform corresponding control and display. For example, the signal of the Tc connection CON8 interface in fig. 3 is an overheat signal. The CON8 interface is connected to a normally open temperature relay. And the temperature relay is tightly attached to an aluminum alloy radiator of the Q3-Q7 IGBT or the D7-D12 output fast recovery diode. And when the temperature relay acts, the overheat phenomenon of the main power device is indicated. At this time, in fig. 8, tc is pulled down to low level (GND), and at the same time, the control circuit turns off PWM signal PWM-STOP; the OC/OT end sends corresponding signals to the panel display and operation control interface circuit, and the welding machine output or welding work is stopped through the detection and control of the display and operation control circuit, so that the welding machine is prevented from being burnt out due to overheat. Under the effect of the cooling fan, when the temperature of the aluminum alloy radiator is reduced to a certain degree, the overheating phenomenon in the welding machine is eliminated, and when the thermal protector is recovered, the control circuit can continue to output PWM control signals. While the overheat indication is eliminated. This achieves overheat protection of the welder.
See fig. 8. The PWM pulse width modulation signal output by the PWM-GD is a signal for determining the output voltage and current of the welding machine inverter main circuit. Its pulse width depends on: 1) In the manual welding, the welding current given signal Ig and the output current feedback signal if+ are determined together. The object or target of the control is the output current magnitude. At idle, the feedback signal is small. The control circuit generates a PWM-GD pulse signal with larger duty ratio, so that two groups of IGBTs (insulated gate bipolar transistors) Q3, Q7, Q4 and Q6 are in the maximum conduction state, and finally the inverter main circuit outputs no-load voltage. When the operator adjusts Ig to a given current and performs welding, the control circuit detects an output current if+ feedback signal through an output hall current detection sensor (400A/4 v). After being processed by the U5A and peripheral circuits thereof, on one hand, the output Current signal displayed by the welder ammeter is obtained through circuit conversion into Current, and the display of the ammeter digital display meter is realized. On the other hand, the detected amplified current feedback signal is compared with a welding current given Ig signal. The compared difference signals pass through a current PI (proportion plus integral) control circuit formed by a post-stage operational amplifier U6B and the like, the output result PWM-GD controls the pulse width or duty ratio of a welding machine output PWM chip, the output current and voltage of the welding machine are determined, and the accurate control of output current parameters is realized. And the output characteristic of the welder is the falling characteristic of the constant current belt out-of-band pull. Further, when the welding current given Ig signal is unchanged, as the detected current feedback if+ signal increases, and after the set value of the given Ig is reached, the difference between the welding current given signal and the current negative feedback control signal decreases with the increase of the current, and after the control, the pulse width or the duty ratio of the output PWM-GD of the welding machine decreases, and the output voltage of the welding machine decreases. This process is called current cut-off negative feedback control. I.e. a feedback control that only works after the current has reached the set point of the welding current potentiometer. Thereafter, the voltage drops much with a small increase in current. When the voltage is reduced to below 16V, the control circuit can increase the pulse width or duty ratio of the output PWM chip of the welding machine along with the reduction of the voltage, so that the welding current is increased according to the set parameters, and finally the reducing characteristic of the constant current out-of-band pull is formed. The current cutoff negative feedback set point is different when the welding current given signal changes, but the other control processes are similar. In this way, between the minimum and maximum settings of the potentiometer, a myriad of drop characteristics are obtained. Such control is also essential to meet manual arc welding. 2) In the gas shield welding control state, a welding voltage given Ug signal and an output voltage feedback signal Uf+ are determined together. The object or target of the control is the output voltage magnitude. The voltage negative feedback PI control is performed by a circuit constituted by an operational amplifier U5C and the like. When no load is applied, similar to manual welding control, a larger PWM pulse width signal is still output, and no-load voltage is obtained. After loading, the control is different from that of manual welding. The output characteristic control of the gas shield welding machine is flat, but not the descending characteristic of constant current out-of-band dragging. The method is characterized in that: the load current changes greatly, while the output voltage changes little, and remains relatively stable. Only when a given voltage signal changes will the output voltage change significantly. The above control process is realized by a corresponding control circuit. It can be seen from fig. 8 that changing the set point of the inductor given potentiometer, di/dtb and di/dta will change, which will affect the PWM-GD signal, eventually changing the characteristics of the welding arc.
For the control circuit portion of fig. 3 (the portion having mot letter in the drawing) and the wire feeding and solenoid valve of fig. 6, the voltages from the switching power supply circuit are +15v, +24v. A wire feed motor with a rated voltage of 24V is connected between MOT+ and MOT-, and belongs to one component part of the wire feed machine in fig. 1. When output voltage exists between the MOT+ terminal and the MOT-terminal, the wire feeding motor connected to the interface runs, and wire feeding control can be realized. Otherwise, the wire feeder does not rotate or feed wires. SWA and SWB are gun switch detection signals. When the welding GUN switch is loosened or not closed, the voltage stabilizer D19 breaks down, the Q3 triode is conducted, the light emitting diode in the optical coupler U2 chip emits light, and the output stage triode is conducted, so that the GUN CHECK is in a low level (GND level). Conversely, when the GUN switch is closed, the GUN CHECK is high. The GUN CHECK control signal is coupled to FIG. 4. The microprocessor control system of fig. 4 can know whether the welding GUN switch is closed or not during gas shielded welding by detecting the level of the GUN CHECK control signal. The wire feeding control U4 chip is a PWM pulse width modulator, and the periphery of the wire feeding control U4 chip is provided with a plurality of diodes, resistors, capacitors and the like. The 8 and 11 pin output ends of the U4 chip generate square wave pulse signals with fixed frequency. The frequency and dead time are determined by R46 and C33. PWM control signals output by the 8 pin and the 11 pin of the U4 chip pass through a circuit formed by D33, D34, Q13 and the like to control the Q14 MOS tube. The rotating speed of the wire feeding motor is controlled by controlling the on-off time of the Q14 MOS tube. The width of the PWM control pulse is determined by a given wire feed speed value Ig. Changing the Ig given size can change the pulse width and ultimately the wire feed speed. That is, ig represents wire feed speed or current control during gas shield welding. When the Ig value is changed during gas shield welding, the wire feeding speed or welding current is changed. The D37 diode group is a freewheeling diode and eliminates adverse effect of counter potential of the wire feeding motor on Q14. R58, Q2 MOS pipe and control circuit thereof constitute the dynamic braking control circuit of the wire feeding motor. The SS/EN of fig. 6 is connected to the SS side of fig. 4. This is a control signal that implements "check" or "try-feed", or manual or jog-feed. When the SS/EN or SS terminal signal in figure 4 is high, the Q2 MOS tube is conducted, the resistor R58 is turned on, so that the energy stored in the motor winding is quickly released through the R58, and the power consumption braking control is carried out on the wire feeding motor, so that the wire feeding motor is quickly stopped rotating, and wire feeding is stopped. In this way, the welding wire does not extend out of the gas shield of the welding gun head too much, which affects the normal operation of welding. Conversely, when the SS/EN or SS terminal signal in fig. 4 is low, the Q2 MOS transistor is not turned on. In addition, a certain Ig given value exists, so that the wire feeding motor rotates to perform wire feeding action. When the detected welder output current is in the normal range, the signal level of the ICS terminal is +15V. The wire feeding control is not limited; when the detected welder output current is too large and exceeds the set limit value, the signal level of the ICS terminal is low-15V. At this time, the wire feeding motor can be stopped to rotate, and the wire feeding is not performed. This achieves protection of the butt welding machine. In fig. 6, electromagnetic air valves are connected to both ends of GAS and GND. GAS/EN is connected to the SQ terminal in fig. 4. This is an air supply control signal that controls the solenoid valve. When the control level of the GAS/EN or SQ terminal is high, Q9 is turned on, the regulator D18 breaks down and stabilizes the voltage, so that Q8 is turned on, and the electromagnetic valve connected to the GAS port operates. Otherwise, the electromagnetic valve is closed. Thus, the on/off control of the shielding gas can be realized.
In FIG. 6, during GAS shield welding, control of GAS feed, wire feed, welding process, etc. can be achieved by detecting the GUN CHECK GUN switch level signal, and combining the SS/EN or SS, GAS/EN or SQ, ig and ICS signals. The control of the air, wire and current given Ig signals is also closely related to the 2T/4T state control signals in fig. 4. Further description is provided below.
See fig. 6 and 4. MIG gas shield welding and 2T GUN operation are selected, and GUN CHECK is high when GUN switches SWA and SWB are closed. In one aspect, the GAS/EN or SQ signal in FIG. 4 is set high. Q9 is conducted, the voltage stabilizing tube D18 breaks down, voltage is stabilized, the Q8 field effect tube is conducted, the GAS terminal is conducted to be +24V, and the electromagnetic air valve acts, so that protective GAS can be conveyed to a welding area of the welding gun end for protection. On the other hand, due to the Ig signal given by wire feeding, under the action of the U4 chip TL494 and the peripheral circuit thereof, the square wave pulse PWM control signals output by pins 8 and 11 of the U4 chip TL494 pass through the circuits formed by D33, D34, Q13 and the like to control the Q14 MOS tube. The on-off time of the Q14 MOS tube is controlled, so that the rotating speed of the wire feeding motor is controlled, and the welding wire is driven to be fed. Thereafter, the arc is ignited and the welding process begins. The width of the PWM control pulses during welding is determined by a given wire feed speed value Ig. The pulse width can be changed by changing the given size, and finally the size of the wire feeding speed is changed. In effect, the magnitude of the welding current is changed. When the SS/EN or SS terminal signal in figure 4 becomes high level after the welding gun switch is loosened, the Q2 MOS tube is conducted, the resistor R58 is turned on, so that the energy stored in the motor winding is quickly released through the R58, the power consumption braking control is carried out on the wire feeding motor, and the wire feeding motor is enabled to rapidly stop rotating and stop feeding wires. In this way, the welding wire does not extend out of the gas shield of the welding gun head too much, which affects the normal operation of welding. Meanwhile, the GAS/EN or (in fig. 4) SQ is changed into low level, Q9 is cut off or not conducted, the voltage stabilizing tube D18 cannot break down or stabilize voltage, the Q8 field effect tube is not conducted, the GAS terminal cannot be connected with +24V, the electromagnetic air valve does not act, and the protective GAS cannot be conveyed.
See fig. 6 and 4. When MIG gas shield and 4T GUN operation is selected, the GUN CHECK is high when GUN switches SWA and SWB are closed. In one aspect, the GAS/EN or SQ signal in FIG. 4 is set high. Q9 is conducted, the voltage stabilizing tube D18 breaks down, voltage is stabilized, the Q8 field effect tube is conducted, the GAS terminal is conducted to be +24V, and the electromagnetic air valve acts, so that protective GAS is conveyed to a welding area for protection. On the other hand, due to the Ig signal given by wire feeding, under the action of the U4 chip TL494 and the peripheral circuit thereof, the square wave pulse PWM control signals output by pins 8 and 11 of the U4 chip TL494 are used for controlling the Q14 MOS tube. The on-off time of the Q14 MOS tube is controlled, so that the rotating speed of the wire feeding motor is controlled, and the welding wire is driven to be fed. Thereafter, the arc is ignited and the welding process begins. When the GUN switch is released, the GAS/EN or SQ signal in fig. 4 remains high, although the GUN CHECK signal goes low, and the solenoid valve continues to operate to deliver shielding GAS to the weld. At the same time, there is still a wire feed given the Ig signal and the wire feed is maintained under its control. In the welding process, the wire feeding speed or the welding current can be changed by changing the size of a given Ig. The welding process will still proceed. When the GUN switches SWA and SWB are turned on again, the GUN CHECK goes high. The air and wire feed and welding process continues to remain. When the GUN switch is released again, the GUN CHECK signal goes low. The Ig signal is turned off and the wire feed is stopped. At the same time, Q2 in fig. 6 will be on, and dynamic braking control is performed on the wire feed. The GAS/EN or SQ signal in fig. 4 goes low and Q9 is off. Q8 will not be turned off immediately because of the capacitor C27, the capacitor C27 will be discharged gradually, and the electromagnetic valve connected between GAS and ground will be closed with hysteresis, thereby realizing the control of hysteresis. Eventually, the shielding gas stops being delivered. The welding process ends.
See fig. 6 and fig. 4. "check" or "try feed", or manual or jog feed control: when MIG on the control panel, i.e., MIG/MAG gas shield welding, is selected and when the "wire check" or "wire test" key K2 on the control panel, i.e., the "wire check" or "wire test" key of fig. 4, is pressed, SS/EN or (in fig. 4) SS outputs a low level signal to perform the "wire check" or "wire test" operation control. At this time, the fet Q2 in fig. 6 is not turned on, and the dynamic braking circuit of the wire feeding motor is turned off. Meanwhile, the GAS/EN or SQ (in the attached figure 4) is at a low level, so that Q9 is not conducted, the voltage stabilizing tube D18 cannot break down and stabilize voltage, the Q8 field effect tube is not conducted, the GAS terminal cannot be connected with +24V, the electromagnetic air valve does not act, and the protective GAS cannot be conveyed. Meanwhile, a certain wire feeding set value Ig is input to an IN input end of the U4 TL494, under the action of the U4 TL494 and a peripheral circuit thereof, pins 8 and 11 of the U4 TL494 output certain square wave pulse PWM control signals, and the Q14 MOS tube is controlled after passing through a circuit formed by D33, D34, Q13 and the like. The on-off time of the Q14 MOS tube is controlled, so that the wire feeding motor rotates according to the set control rotating speed to drive the welding wire to feed. Thereby realizing the control of the inching wire feeding process. The wire feeding operation by inching can lead the welding wire to extend out of the head of the welding gun by a certain length, namely about 10 mm. During the inching wire feeding period, the electromagnetic valve does not act, and the welding machine does not output voltage or current. The inching wire feeding control is mainly convenient for a user to install welding wires into a welding gun. The speed of the jog feed is not very fast because the feed is too fast, which is inconvenient for the installation of the welding wire. Typically much less than the wire feed speed at the time of welding.
For the purposes of the present invention, where MIG/MAG gas shield welding is selected, the welding parameters that may be selected are: wire diameter, inductance, trim welding voltage, and burn back time. 1) The diameter parameters of the welding wire are three of 0.6, 0.8 and 1.0 mm. Different wire feed speed set points affect the signal output of the wire feed control circuit PWM. That is, the rotational speed of the wire feed motor may be varied. It is well known that thin wire melts quickly and the required wire feed speed is correspondingly greater. Conversely, the thick wire melts slowly and the wire feed speed is correspondingly slower. The selection control of the wire diameter, i.e. the circuit set to meet the above requirements, is a good control way to make the thick-thin wire welding control circuit better adapted. And is also convenient for users to use in welding operation. 2) The inductance parameter can be selected between 1 and 8. The change of inductance parameters can affect the arc characteristics during gas shield welding, so that the welding process, stability, splash size, weld formation and the like can be changed. 3) The trim welding voltage may vary between + -5V of the standard value. The welding voltage and the welding current or the wire feeding speed are set in a unified adjustment mode, namely, the wire feeding speed or the welding current is changed, and the corresponding welding voltage standard value can be changed accordingly. And the welding voltage is finely adjusted, so that the welding voltage can be increased or reduced on the basis of a standard value. The welding parameters can be properly adjusted by the user according to the actual welding conditions. 4) The burn-back time parameter may vary between 0 and 1S. The size of the back firing time can change the control state of the gas shielded welding arc-receiving stage of the welding machine. Different back firing time can have an influence on the welding process in the stage of the near end, namely the welding seam arc pit filling in the arc receiving stage, the bead removal of the welding wire head, the arc re-ignition and the like. In summary, by changing the parameters, the control circuit can change the arc characteristics by adjusting the PWM signal of the wire feeding control circuit, the output characteristics of the welding machine, and the PWM signal of the driving circuit, and finally, changing the wire feeding speed (actually, the welding current), the output voltage, and the like of the welding machine, thereby finally realizing different welding processes.
The above is a brief description of the control process of each circuit board portion and three soldering methods of the present invention. The circuit principle is relatively complex to illustrate. The above only gives the idea and results of control. But since the invention has been presented with a detailed schematic diagram of the circuit, it is fully readable by a person having circuit reading capabilities (or knowledge of the relevant circuit). The circuit diagram is also a silent language. But even more explanation is difficult for those without circuit reading capabilities (or without knowledge of the relevant circuitry). In view of the foregoing, this patent specification will only be presented in a major portion thereof to provide a better understanding of the principles and processes associated with such operations. With respect to other controls, it is well known to analyze and understand in conjunction with circuit diagrams.
From the above description, it is apparent that the present invention has its own unique design ideas and methods. The power supply of the welding machine is 220-240V, and the frequency is 50 or 60Hz. The control circuit and the structural design of the welding machine can realize the control of the output and the like of three welding methods of the welding machine, are the root causes of the technical advantages of good control performance, compact welding machine structure and the like of the welding machine product, and are important guarantees for meeting the technical advancement of high-efficiency and low-cost production, high reliability and manufacturing process of the product. The invention patent application is to protect the structure and circuit of the welder.
The foregoing is a detailed description of the invention in connection with specific welder structures and circuit boards and control functions, and it is not to be construed that the practice of the invention is limited to such descriptions. It will be apparent to those skilled in the art that many other embodiments and variations can be made without departing from the spirit of the invention, and these should be considered as falling within the scope of the invention.
Claims (1)
1. An IGBT contravariant multifunctional welding machine which is characterized in that: the inside of the welding machine is in a left-right layout structure, and the internal mechanical part of the welding machine is separated from the main control panel part through a middle partition board; a wire feeding part is arranged at one side of the left side; the wire feeding part wire reel shaft is arranged on a middle partition plate in the welding machine; the wire feeding mechanism is arranged on the bottom plate, is close to the front panel of the welding machine, and is connected with the European gas shielded welding gun seat on the front panel; the main control board, the cooling fan and the reactor are arranged on the other side of the right side; the front panel of the welding machine is provided with: the welding gun comprises a copper head of an European type welding gun interface assembly, a black output quick connector assembly, a red output quick connector assembly and an operation and nixie tube display control panel; a power switch, a power supply wire with a plug, a cooling fan, a protective gas inlet nozzle and an electromagnetic air valve are arranged on the rear panel of the welding machine; for the circuit part of the main control board of the welding machine, the circuit board is designed into two pieces, namely an operation and nixie tube display control circuit board and a main control board;
The operation and nixie tube display control circuit board part is connected with other circuit parts of the welding machine through a plug; the circuit of the operation and nixie tube display control circuit board mainly comprises a microprocessor, two common anode nixie tubes, a gas detection and wire detection key, an argon arc welding/manual welding/gas shield welding three welding method selection key, a 2T/4T welding gun switch operation mode and VRD function selection key, a parameter option key, a parameter adjustment encoder, two optical couplers for controlling gas supply and wire supply, an overheat or overcurrent detection and control circuit, an inductance parameter adjustment control circuit, a voltage detection circuit, a current detection circuit, an output voltage conversion circuit, an output current conversion circuit and an output voltage conversion circuit; under the control of the microprocessor control system, according to the selection of a user and the welding state, the welding current during manual welding and argon arc welding can be displayed; welding current or wire feeding speed and voltage during gas shielded welding can be displayed; the light emitting diode corresponding to the options of manual welding, argon arc welding, gas shielded welding, 2T, 4T, VRD, gas detection and wire detection can be lightened; the microprocessor control system is used for detecting given welding parameters, finally outputting control parameters, and respectively converting the control parameters into voltage given analog quantity and current given control signals through a current-voltage conversion circuit for controlling the output characteristics of the welding machine; the microprocessor control system judges whether the welding machine has overheat or overcurrent phenomenon by detecting OC or ICS signals; when the temperature relay acts, the control circuit turns off the PWM signal; the OC/OT end sends corresponding signals to the panel display and operation control interface circuit, and the welding machine output or welding work is stopped through the detection and control of the display and operation control circuit, so that the welding machine is prevented from being burnt out due to overheat; under the action of the cooling fan, when the temperature of the aluminum alloy radiator is reduced to a certain degree, the overheating phenomenon in the welding machine is eliminated, and when the thermal protector is recovered, the control circuit can continue to output PWM control signals;
The wire feeding part comprises a wire reel shaft (9), a wire feeding mechanism (6), an European gas shielded welding gun interface copper head (5) and a wire feeding control circuit part on a main control board, wherein the wire reel shaft is used for gas shielded welding; the wire feeding mechanism (6) and the wire feeding disc shaft (9) are arranged on the inner middle partition plate (10); the wire feeding mechanism (6) is close to the front panel (24) of the welding machine, and the wire feeding mechanism (6) is correspondingly connected with the European gas shielded welding gun interface copper head (5) arranged on the front panel (24); during shielded welding, a gas shielded welding gun is connected with an European gas shielded welding gun interface copper head (5) in a matched manner, a welding wire is mounted on a wire reel shaft (9), the welding wire can be fed into a wire feeding mechanism (6) after being mounted, then is fed into a welding gun head connected with the welding wire through the European gas shielded welding gun interface copper head (5), and can extend out of a conductive nozzle of the gas shielded welding gun under the control of a circuit through a wire feeding wheel and a pressing wheel of the wire feeding mechanism (6), when the gas shielded welding is carried out, the wire feeding speed of the welding wire is controlled by a circuit board and a corresponding potentiometer, the welding current can be changed by adjusting the wire feeding speed, a protective gas interface on the European gas shielded welding gun interface copper head (5) is connected to an electromagnetic gas valve (15) through a gas pipe, and after the gas cylinder is opened, the electromagnetic gas valve (15) can be opened and disconnected under the control of a welding machine circuit, so that the protective gas is connected into the welding gun, and flows out of the welding gun head, and metal protection of a welding area is realized; when manual welding is performed, the wire feeding part is not controlled;
The main control board comprises an input filter circuit, a power-on buffer circuit, an input rectifying and filtering circuit, an inversion main circuit, a switching power supply circuit, an inversion PWM and IGBT driving control circuit, a wire feeding and electromagnetic valve control circuit and an output characteristic control circuit;
220V-240V input power supply voltage is connected to a power supply switch S1, a power supply of a power grid is connected through the power supply switch S1 on a rear panel of the welder, and then the power supply is connected through an input filter circuit consisting of a resistor and a capacitor;
the input alternating current is rectified by a rectifier DB1 to become pulsating direct current after passing through a power-on buffer circuit part consisting of a thermistor, a relay K1, a field effect transistor Q1, a diode D2 and a voltage stabilizing tube D3, and the pulsating direct current charges a C8-C9 electrolytic capacitor, the voltage is gradually increased, and finally the pulsating direct current becomes relatively stable high-voltage direct current;
rectifying by a rectifier (30), and filtering by an electrolytic capacitor, wherein the obtained high-voltage direct current is supplied to an inversion main circuit consisting of a capacitor, four IGBT tubes, an inversion main transformer, a fast recovery diode, an output current filter reactor or inductor and an output Hall current detection sensor; the inverter main circuit converts the high-voltage direct-current bus voltage into medium-frequency alternating current, the inverter main transformer realizes voltage reduction and conversion of high-current output, the fast recovery diode converts the medium-frequency alternating current output by the inverter transformer into direct current, the converted current waveform is pulsating and unstable, the stability of the welding process is not facilitated, the L2 output current filter reactor or inductor is adopted for filtering, and thus the output current waveform becomes stable, and the welding seam with high quality is facilitated to be obtained;
The high-voltage direct-current bus voltage is supplied to the switching power supply circuit, the switching power supply circuit is composed of a switching power supply transformer, a MOS tube, a fast diode, an integrated PWM circuit, an integrated voltage stabilizer and resistor and capacitor devices around the switching power supply circuit, and the switching power supply circuit generates +5V, +15V, +24V, -15V power supply voltages and supplies the power supply voltages to other corresponding control circuits and the like for electrified operation;
the driving transformer, the integrated PWM chip, the diode, the voltage stabilizing tube, the resistor, the capacitor and the inversion PWM of the IGBT tube and the IGBT driving control circuit part around the integrated PWM chip, wherein the integrated PWM chip outputs PWM signals to have small driving power, the driving control circuit is required to amplify the power, and then the driving transformer is used for controlling the on-off working state of the IGBT tube; the output control signals of the integrated PWM chip are two groups of PWM square wave pulse signals, the frequency of square waves is fixed, the two groups of square wave pulse signals have a fixed time difference in time, and are also called dead time in the profession, the time is determined by the parameter setting of peripheral devices of the chip, the PWM pulse width modulation signals output by the chip are signals for determining the output voltage and the current of an inverter main circuit of the welding machine, and when the pulse width of the PWM pulse width modulation signals depends on the control state of manual welding (MMA), the given welding current signals and the feedback current signals are determined together; the object or target of control is the output current magnitude; when no load exists, the feedback signal is very small; the control circuit generates a PWM pulse signal with larger duty ratio to enable the two groups of IGBTs to be in an alternate conduction state, on the other hand, the detected current signal is processed by signal amplification and the like and is used as a current negative feedback control signal, the current negative feedback control signal is compared with a welding current given signal, proportional and integral regulation control is carried out on the compared difference signal, the output result controls the pulse width or duty ratio of the welding machine output PWM chip, the size of the welding machine output current and voltage is determined, and the accurate control of the output current parameter is realized;
The output characteristic control circuit is subjected to signal amplification processing, and is used as a current negative feedback control signal, and is compared with a welding current given signal, and proportional and integral regulation control is carried out on the compared difference signal, so that the output result controls the pulse width or duty ratio of the output PWM chip of the welding machine, the output current and voltage of the welding machine are determined, and the accurate control of the output current parameters is realized; the output characteristic of the welder is the descending characteristic of constant current out-of-band dragging; further, when the welding current given signal is unchanged, the current detected by the welder circuit increases, and after the given set value is reached, the difference value between the welding current given signal and the current negative feedback control signal decreases along with the current increase, and after proportional and integral control, the pulse width or duty ratio of the welder output PWM chip decreases, and the output voltage of the welder decreases, which is the process of so-called current cut-off negative feedback control; namely, feedback control which only works when the current reaches the set value of the welding current potentiometer; with a small increase in current, the voltage drops much; when the voltage is reduced below 16V, the control circuit can increase the pulse width or the duty ratio of the output PWM chip of the welding machine along with the reduction of the voltage, so that the welding current is increased according to the set parameters, and finally the reducing characteristic of the constant current strip tail is formed; the load current changes greatly, the output voltage changes very little, and the load current is kept relatively stable; the control process is realized by a corresponding control circuit only when the given voltage signal changes and the output voltage changes greatly.
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