CN210099175U

CN210099175U - double-MCU digital PI and PWM control multifunctional welding machine

Info

Publication number: CN210099175U
Application number: CN201920357870.2U
Authority: CN
Inventors: 孙敏; 魏继昆; 朱宣东; 陈法庆; 朱宣辉
Original assignee: Zhejiang Kende Mechanical and Electrical CO Ltd
Current assignee: Zhejiang Kende Mechanical and Electrical CO Ltd
Priority date: 2019-03-20
Filing date: 2019-03-20
Publication date: 2020-02-21
Anticipated expiration: 2029-03-20

Abstract

The utility model relates to a double-MCU digital PI and PWM control multifunctional welder and a circuit structure thereof, which adopts a switch power circuit; a control circuit which is composed of double microprocessor digital PI and PWM as cores is adopted, and a means of replacing a hardware circuit by software as far as possible is utilized; the circuit board is divided into the power board and the control board to solve the problems, so that the output control of two welding methods of manual electric arc welding and argon arc welding is realized, the VRD low no-load voltage output and the welding parameter digital presetting and displaying functions are realized, the problem of poor network voltage fluctuation resistance of the welding machine is solved, the volumes of the control board and the whole machine are reduced, the weight of the whole machine is reduced, and the power-volume ratio of the welding machine is improved; because the integration level of the control circuit is improved, the connecting lines between the circuit boards are reduced, the reliability of the welding machine is further improved, and the manufacturing process of the welding machine is simplified.

Description

double-MCU digital PI and PWM control multifunctional welding machine

Technical Field

The utility model relates to a multi-functional welding machine of two MCU digit PI and PWM control belongs to contravariant welding machine technical field.

Technical Field

The sales volume of the inverter welding machine is large, and the application range is wide. However, such a welding machine has different welding methods and functions, different structural designs of circuits, circuit boards and the whole machine, different control principles and modes, different layout and connection modes of the circuit boards and the whole machine, or different connection complexity, and completely different production processes and manufacturing processes of the products. These all affect the performance, reliability, production efficiency, transportation costs, etc. of the product, ultimately affecting the market competitiveness of the product.

At present, in domestic and foreign markets, the rated current of a small inverter welder is generally 80-200A (load duration rate is 100-20%). For such welder products, if the design is not good, the following problems can occur: 1) the net pressure fluctuation resistance is poor. This phenomenon is more pronounced when the supply voltage varies more. For example, in some welding machines, when the input power voltage of the power supply grid is low, such as below 180VAC, even if a thin welding electrode is used, the welding machine cannot perform welding normally, so that the application range of the welding machine is limited to a certain extent; 2) the control circuit has low integration level and complex circuit, which leads to the reduction of the working reliability of the welding machine circuit. This is especially true in the case of multiple welding methods and functional outputs of the welder. For example, the conventional welding machine adopting two welding methods of manual arc welding and argon arc welding controlled by an analog circuit has complicated method conversion control circuit. Because of the control output requirements of different welding methods, some welders with unsatisfactory design also have two sets of PI (proportional plus integral control circuit) analog control circuits, and in addition, a PWM (pulse width modulation) control circuit consisting of analog device circuits. This causes the circuit to be complicated, the circuit board and the whole machine have large size, the power volume ratio (the rated output current is multiplied by the rated output voltage divided by the volume) is small and so on; 3) the circuit board has many blocks and complicated connecting lines. Examples of the circuit board include (input and output) rectifying boards, IGBT driving boards, display circuit boards, control circuit boards, IGBT inverter boards, and the like. Therefore, how to solve the problems and develop a welding machine with good structure and performance, simple and advanced manufacturing process and high working reliability is a topic generally concerned by electric welding machine developers.

SUMMERY OF THE UTILITY MODEL

The utility model can adopt the international universal power supply of 220V-240V, 50 or 50Hz, has two welding methods of manual arc welding and argon arc welding, and utilizes the touch key to select; having a VRD (low no-load voltage output) function and a VRD indication; having over-temperature protection control and indication; digitally displaying welding current parameters; the circuit composed of the 8-bit MCU microprocessor as a core controls the display of welding parameters and the detection of overheating signals; the 32-bit MCU microprocessor is a circuit formed by cores, and realizes the selection and control of two welding methods of manual arc welding and argon arc welding and the VRD output function; current given signal and current negative feedback digital PI (proportion + integral) operation control; digital operation is carried out to control PWM signal output; VRD, over-temperature and over-current protection, argon arc welding (TIG) and manual arc welding (MMA) control state indication.

By using a switching power supply circuit; a control circuit which is formed by taking double microprocessors as cores is adopted, and a means of replacing a hardware circuit by software as far as possible is utilized; the circuit board is divided into a power board and a control board to solve the problems; the output control of two welding methods of manual electric arc welding and argon arc welding, VRD and welding parameter digital presetting and displaying functions are realized, the problem of poor network voltage fluctuation resistance of the welding machine is solved, the volumes of a control panel and the whole machine are reduced, the weight of the whole machine is reduced, and the power-volume ratio of the welding machine is improved; because the integration level of the control circuit is improved, the connecting lines between the circuit boards are reduced, the reliability of the welding machine is further improved, and the manufacturing process of the welding machine is simplified.

The following technical scheme is adopted for achieving the purpose:

the utility model discloses the shell part of welding machine. The method mainly comprises the following steps: the front panel, chassis bottom plate, chassis outer cover or shell, braces, rear panel.

The utility model discloses spare part of installation on the front panel of welding machine mainly has: the welding machine comprises a positive electrode output quick connector seat assembly, a negative electrode output quick connector seat assembly, a control panel (arranged in the welding machine and fixed on a front panel, and the control panel comprises an overheating protection indicator lamp, a current digital display meter, a VRD function indicator lamp, an argon arc welding indicator lamp, a manual arc welding indicator lamp, a welding method selection button, a current regulator, other circuits and electronic component parts thereof which are designed on the panel in a layout mode).

The utility model discloses spare part of installation mainly has on the rear panel of welding machine: a power switch, a power supply wire, and a cooling fan (arranged inside the welding machine and fixed on the rear panel). And cold air is conducted from an air inlet hole at the rear part of the welding machine case. Can make some heating devices or spare parts in the welding machine have good cooling effect.

The utility model discloses the inside of welding machine, the spare part of installation mainly has: the power board (including many circuits and its electronic components of the overall arrangement design on this board), (have certain thickness) the insulation board, connect between negative polarity output terminal and power board (made with copper or aluminium strip with certain thickness and width) the connecting piece, connect between positive polarity output terminal and (install on the power board) the aluminium radiator of the fast recovery diode (made with copper or aluminium strip with certain thickness and width) the connecting piece, two insulation fixed supporting feet and its fastening screw of power board, and the connecting wire or control line between some circuits.

The utility model discloses the circuit board design of welding machine is two parts, firstly the power board, secondly the control panel. A large number of patch devices are adopted in each part of the control panel, and a small number of devices are plug-in type. The production of the circuit board mainly adopts advanced process processing technologies such as automatic device assembly, welding and the like, and only a small number of devices need to be installed and welded in a manual mode. Because the digital control circuit formed by using double microprocessor chips as cores is adopted, the integration level of the circuit is higher than that of the control circuit formed by using a separation device and an analog circuit, so that a plurality of control tasks or works are solved by combining software and hardware, and the digital control circuit has advantages over the separation device and the analog control circuit in the aspects of control circuit and performance. The size of the circuit board and the product is reduced, the weight and the transportation cost of the welding machine are reduced, the control connecting lines among the circuit boards are few, the manufacturing process is simplified, and the production is more convenient.

The utility model adopts the switch power circuit; a control circuit which is formed by taking double microprocessors as cores is adopted, and a means of replacing a hardware circuit by software as far as possible is utilized; and the circuit board is divided into a power board and a control board to solve the problems. The output control and overheating and overcurrent protection control of two welding methods of manual electric arc welding and argon arc welding are realized, the VRD and welding parameter digital presetting and displaying functions are realized, the problem of poor network voltage fluctuation resistance of the welding machine is solved, the volumes of a control panel and the whole machine are reduced, the weight of the whole machine is reduced, and the power-to-volume ratio of the welding machine is improved. Because the integration level of the control circuit is improved, the connecting lines between the circuit boards are reduced, the reliability of the welding machine is further improved, and the manufacturing process of the welding machine is simplified.

The utility model discloses welding machine, a small amount of spare part specification parameter on the accessible adjustment circuit board form the product of different output rated current and load persistence rate to different current classes and load persistence rate requirements. For example, the current class, number (e.g., two IGBT switches in parallel for use as one IGBT switch; circuit board design needs to be modified at the same time) and heat sink size of the IGBT devices in the half-bridge inverter circuit are changed; changing the model and parameters of a commutation capacitor in a half-bridge inverter circuit; changing the model, parameters and quantity of the fast recovery diodes; changing the specifications and parameters of an inverter main transformer and an output filter reactor; the half-bridge inverter circuit is changed into a single-end inverter circuit, a full-bridge inverter circuit and the like, so that series products with different specifications can be easily formed. Such as 200A/28V, 180A/27.2V, 160A/26.4V, 140A/25.6V, 120A/24.8V and other specifications. These variations, of course, aim to match the production costs of the product with the specifications and performance specifications of the respective machine. Thus, each specification and model of welding machine can realize better cost control. This enhances the market competitiveness of the developed product. The utility model discloses the circuit principle of welding machine, circuit board and complete machine structural design have own unique part. This is also the fundamental object of the patent protection.

Drawings

FIG. 1 is a schematic structural view of an exemplary welder made with the present invention;

FIG. 2 is a schematic diagram of a main circuit portion of a power board of the welder;

FIG. 3 is a schematic diagram of the switching power circuit portion on the power board of the welder;

FIG. 4 is a schematic diagram of a portion of an electrical snubber circuit on the power board of the welder;

FIG. 5 is a schematic diagram of the +3.3V DC power supply circuit portion on the control board of the welder;

FIG. 6 is a schematic diagram of a portion of the drive circuitry on the power board of the welder;

FIG. 7 is a schematic diagram of the interface circuit portions on the power and control boards of the welder;

FIG. 8 is a schematic diagram of the control circuit portion of the 32-bit microprocessor on the control board of the welder;

FIG. 9 is a schematic diagram of the control circuit portion of the 8-bit microprocessor on the control board of the welder;

the names of the components in the drawings are as follows: 1. a harness; 2. a chassis housing; 3. a housing screw; 4. IGBT radiating fins; 5. an electrolytic capacitor EC 1; 6. an electrolytic capacitor EC 2; 7. IGBT radiating fins; 8. a fast recovery diode output heat sink; 9. a main transformer; 10. a power board; 11. a power board support leg; 12. a control panel; 13. a current regulator and a knob; 14. a chassis base plate; 15. a front panel; 16. a positive polarity output quick coupling; 17. a negative polarity output quick connector; 18. a bottom screw; 19. a fan or cooling fan; 20. a fan screw; 21. a rear panel; 22. a power line; 23. and a power switch.

Detailed Description

The utility model relates to a two MCU digit PI and the multi-functional welding machine of PWM control, welding machine can adopt 220V ~ 240V, 50 or 50 Hz's international general power supply. The method has two welding methods of manual arc welding and argon arc welding, and the touch key is used for selection; having VRD functionality and a VRD indication; having over-temperature protection control and indication; digitally displaying welding current parameters; the circuit composed of 8-bit microprocessor as core controls the display of welding parameters; the 32-bit microprocessor is a circuit formed by cores, and selection and control of two welding methods of manual arc welding and argon arc welding are realized; current given signal and current negative feedback digital PI (proportion + integral) operation control; digitally controlling PWM signal output; VRD, overheating, argon arc welding (TIG) and manual arc welding (MMA) control state indication.

FIG. 1 is a schematic structural design of an exemplary welder made using the present invention. Attached table 1 is a list of the major components in the schematic. As shown in the attached fig. 1 and the attached table 1, the main components are explained as follows:

1) a front panel portion. The utility model discloses spare part of installation on the front panel of welding machine mainly has: positive and negative output quick

connector mount assemblies

16, 17. Note that: the numbers in parentheses represent the serial numbers of the major components in fig. 1. Hereinafter, the description will not be repeated), and a control board 12 (installed inside the welding machine and fixed to the front panel. Comprises an overheating protection indicator lamp, a current digital display meter, a VRD function indicator lamp, an argon arc welding indicator lamp, a manual arc welding indicator lamp, a welding method selection button, a current regulator 13, and other circuits and electronic component parts thereof which are designed on the board).

The control panel is provided with an overheating protection indicator lamp, a current digital display meter, a VRD function indicator lamp, an argon arc welding indicator lamp, a manual arc welding indicator lamp, a welding method selection key and a current regulator 13, and is also provided with a control circuit part which takes 8-bit and 32-bit single-chip microcomputer or microprocessor as a core. These circuits, mainly include: +3.3V DC power supply circuit; manual welding or argon arc welding method selection and inverter circuit output parameter (current, voltage) control; current given parameters, detection of current negative feedback signals, and PWM pulse width output regulation and control; controlling overheat protection; and a display control circuit of the current parameter.

2) A back panel portion. The utility model discloses spare part of installation mainly has on the rear panel of welding machine: a power switch 23, a power supply wire 22, and a cooling fan 19 (installed inside the welding machine and fixed on the rear panel). And cold air is conducted from an air inlet hole at the rear part of the welding machine case. Can make some heating devices or spare parts in the welding machine have good cooling effect.

3) The utility model discloses the shell part of welding machine. The method mainly comprises the following steps: front panel 15, chassis bottom plate 14, chassis outer cover or shell 2, braces 1, back panel 21.

4) The utility model discloses the inside part of welding machine. The parts installed mainly include: a power board 10 including many circuits and electronic components thereof designed on the board, an insulating board (having a certain thickness), a connector (made of copper or aluminum bars having a certain thickness and width) connected between the negative polarity output terminal and the power board, a connector (made of copper or aluminum bars having a certain thickness and width) connected between the positive polarity output terminal and the aluminum heat sink 8 of the fast recovery diode (mounted on the power board), two insulating fixing legs 11 and fastening screws thereof of the power board, and a connection lead or control line between some circuits.

The power board circuit of the power board mainly includes: a power-on buffer control circuit; an input rectifying and filtering circuit; a switching power supply circuit or a working voltage generating circuit; an IGBT drive control circuit; an IGBT half-bridge inverter main circuit; and a primary current detection circuit of the inverter transformer.

The devices on the power board 10 comprise a rectifier bridge, a filter electrolytic capacitor, an IGBT, an inverter main transformer 9,

radiators

4 and 7 of the IGBT, a pin sheath of an IGBT tube, a radiator 8 of a fast recovery diode, a relay, a driving transformer, a switching power supply transformer, an output connecting piece, and a plurality of electronic components and the like.

The pins of the IGBT are sleeved by pin sheaths and then welded to the power board 10. The utility model discloses an adopt pin sheath mode to solve IGBT's dustproof performance problem. By adopting the technical measures, the phenomenon that some conductive metal dust on the working site is adsorbed between pins of devices such as IGBT tubes and the like and on a control circuit board after the inverter welding machine is used for a long time can be avoided. Without causing a reduction in creepage distance. The device and control circuitry are not prone to failure. This improves the reliability of the welder operation to a certain extent.

The radiator of the IGBT and the radiator of the fast recovery diode are fixed to the power board 10 by screws, respectively. The power plate 10 is fixed on the bottom of the machine floor 14 by two power plate feet 11. The secondary middle tap conductive part of the inverter transformer 9 on the power board 10 is connected to the output negative polarity end of the welding machine through a connecting piece and a screw nut. The radiator of the fast recovery diode is connected to the output positive polarity end of the welding machine through a connecting piece and a screw. The upper part of the rear board of the chassis bottom board 14 is fixed with the upper rear part of the power board through a connecting piece. Through the above assembling and connecting mode, the main parts of the inverter welding machine of the utility model form a whole. Due to the arrangement of the direct current cooling fan 19 with large air volume and high speed (5000-6000 rpm/min), the cooling efficiency of key parts of the heating main power (such as all IGBTs, all fast recovery diodes, all radiators, a rectifier bridge, an inverter main transformer and the like) can be improved. The load duration rate during large current output is also improved. If the output current of the welder is small, the load hold up rate will be higher. Therefore, the problem of short welding time is solved. Meanwhile, the failure rate of devices or parts such as IGBT (insulated gate bipolar transistor) or fast recovery diode, inverter transformer and the like is effectively reduced.

The utility model discloses a welding machine, its main control board part is connected with the power board part circuit of welding machine through the socket or the connector of this on-board design and their connecting wire. There are not many external connection lines between the boards. Unlike other welding machines with multi-circuit board structure, there are many control connecting lines between circuit boards, which not only has many manufacturing processes and complex production process, but also occupies large space, making the whole machine large in size and heavy in weight. Owing to adopt the utility model discloses a circuit board structure and circuit design, the size of reducible circuit board and complete machine reduces product weight, production and cost of transportation. Because the control lines are few, the production and processing procedures of the welding machine are few, the manufacturing process is greatly simplified, and the production is more convenient. In addition, a control circuit which is formed by taking double microprocessors as cores is also adopted in the circuit, and a plurality of functions of the control circuit are realized by adopting software. Therefore, the circuit is simplified, the integration level of the circuit is improved, and the control functions of manual welding and argon arc welding selection, state indication and parameter control, VRD low voltage output, parameter digital display and the like can be conveniently realized.

From the control function of the welding machine circuit, the control of the power-on buffer circuit is mainly completed; input rectification and filtering; generating a switching power supply circuit or a direct current power supply; IGBT drive control; IGBT half-bridge inversion conversion control; detecting the primary current of the inverter transformer; controlling the output parameters (current and voltage) of an inverter circuit of a manual welding or argon arc welding method; current given parameters, detection of current negative feedback signals, and digital PI and PWM pulse width output regulation and control; controlling overheat protection; and displaying and controlling the work of the current parameter. Finally, under the action of the control circuit, various control requirements of manual electric arc welding and argon arc welding are realized.

The utility model discloses the theory of operation of above-mentioned each part circuit of welding machine is briefly described as follows:

the control circuit board of the welding machine is divided into a power board and a control board. The circuit designed by the layout on the power board comprises the MB interface on the left side in the figure 2 (without the power switch S1 in the figure), the figure 3, the figure 4, the figure 6 and the figure 7 and the RT 1-RT 2 interface parts. The circuit designed on the control board comprises ZB and SIP3 x 2 interfaces on the right side in figures 5 and 7, and parts of figures 8 and 9.

FIG. 2 is a schematic diagram of the main circuit portion of the power board 10 of the welding machine according to the present invention, and it can be seen from FIG. 2 that the main circuit of the welding machine mainly comprises a power switch 23 (a 25A or 30A switch can be selected according to the magnitude of the output current of the welding machine), a rectifier or rectifier bridge B1, EC 1-EC 2 electrolytic capacitors (a 470 mu F/400V or 680 mu F/400V capacitor can be selected according to the magnitude of the output current of the welding machine), resistors R7 and R8, IGBTs 1 and IGBT2, resistors R13-R16 and capacitors CC 1-CC 5, an inverter main transformer T1, a T3 primary bus current detection transformer, D1-D3 output rectifying fast recovery diodes, resistors R17-R20 and capacitors CC 7-CC 8, a positive (+) OUT terminal 16 and an output OUT terminal 17, and a cooling FAN1 configured with 24V DC high-speed FAN (-) is not shown in FIG. 2, but rather the FAN via FAN1 plug in fig. 4).

When the welder is powered on, the power switch S1 is connected with the power of the power grid. Alternating current from a power grid is rectified by the PTC thermistor and the B1 rectifier bridge to be changed into pulsating direct current. And then charging the EC 1-EC 2 electrolytic capacitor. The voltage on the electrolytic capacitor of EC 1-EC 2 gradually rises and finally becomes more stable direct current of + 310V. The EC 1-EC 2 electrolytic capacitor plays a role in filtering. The resistors R7 and R8 are mainly used for releasing high voltage stored in the electrolytic capacitors of EC 1-EC 2 when the welding machine does not work by power on, so that the phenomenon of electric shock to a human body is prevented. CC3 is the input antijam filter capacitance. The contact K1B of the relay is connected in parallel with two ends of the PTC thermistor, and forms an electrifying buffer circuit together with the relay K1A and a control circuit thereof (see figure 4).

In fig. 4, the operation time of the relay K1A lags behind the closing time of the power switch S1 (23). The power-on buffer circuit is controlled by a power-on buffer circuit consisting of a U3 tube, a voltage regulator tube Z3, a resistor R6 and a capacitor C5. Namely, the K1A relay is operated in a delayed mode, when the charging voltage on the electrolytic capacitor of EC 1-EC 2 rises to a certain value, and the switching power supply circuit generates VCC and-12V direct-current power supply voltage, the voltage regulator tube Z3 breaks down and stabilizes the voltage, and the K1A relay operates after the U3 tube is conducted. After the action, its contact K1B closed PTC thermistor's branch road, short circuit PTC thermistor, just can make the utility model discloses the normal contravariant work of welding machine, direct current bus heavy current flows through from the contact K1B of relay. Therefore, the design of the power-on buffer circuit is to prevent the power switch S1 from being burnt out due to the fact that no voltage exists on the electrolytic capacitors of EC 1-EC 2 at the moment of switching on the power switch S1, and the electrolytic capacitors are equivalent to short circuits, which can form large power-on surge current. The function of the power-on buffer circuit is to limit the surge current by using the time delay action of the K1A relay and a method of connecting the PTC thermistor in series. The resistance of the PTC thermistor increases as the temperature thereof increases. Therefore, the power-on buffer circuit can play a better protection role.

In FIG. 4, the K1A relay can select 25A/24V and 30A/24V relays according to different output currents of the welding machine.

In the attached figure 2, the +310V direct current is supplied to a half-bridge inverter main circuit which is composed of IGBT 1-IGBT 2 tubes, a T1 inverter main transformer 9, D1-D3 fast recovery diodes, a T3 primary bus current detection transformer, a converter capacitor CC1 and CC2 on one hand. The functions are as follows: through an IGBT drive control circuit (see figure 6), under the control of PWM pulse width modulation signals generated by a control board 12, a circuit schematic diagram of the part and other related parts), the alternating on-off control of the IGBT1 and the IGBT2 is realized through the action of two groups of alternating drive signals of G1, E1, G2 and E2, and finally, a half-bridge main circuit consisting of the IGBT1, the IGBT2, the commutation capacitor CC1 and the commutation capacitor CC2 forms an inversion process to convert high-voltage direct current into medium-frequency (dozens of KHz) alternating current. The T1 inverter transformer realizes voltage reduction and conversion of large current output. The D1-D3 fast recovery diodes convert the medium-frequency alternating current output by the inverter transformer T1 into direct current, and then voltage and current are output from terminals OUT (+) and OUT (-). OUT (+) represents the positive polarity output of the welder; OUT (-) represents the negative output of the welder.

On the other hand, the +310V direct current is supplied to a switching power supply circuit which is composed of a T2 switching power supply transformer (provided with four windings, namely N1, N2, N3 and N4, N1 is a primary winding, and the other windings are secondary windings), TVS, Z and Z1-Z2 voltage regulators, D4-1, D4, D6 and D23 diodes, an IC1 switching power supply control chip (TOP 264 VG), and surrounding resistors R1-R5, R21, capacitors C1-C4, EC3, EC5 and an optical coupler U2 (comprising two parts of U2A and U2B), thereby generating VCC-12V power supply voltage and supplying the voltage to other control circuits for live working. A circuit consisting of a primary winding N1 and a secondary winding N4 of a T2 switching power supply transformer, TVS and Z voltage-stabilizing tubes around the primary winding N1 and the secondary winding N4, diodes D4 and D4-1, resistors R1 and R21, capacitors C1-C2, EC5 and an IC1 switching power supply control chip (TOP 264 VG) is connected to +310V through a plug J1 and belongs to a high-voltage or strong-current loop. In order to ensure the safety of the control circuit, in fig. 3, a U2 EL817 photocoupler is used for isolation. The core control chip of the switching power supply is an IC1, i.e., a TOP264VG chip. The weak current or low-voltage circuit part of the switching power supply part consists of secondary windings N2 and N3 of a T2 switching power supply transformer, and a D6 diode, a D23 diode, a Z1-Z2 voltage-stabilizing tube, resistors R2-R5, capacitors C3-C4, EC3 and a U2 light-emitting diode part of U2A of an optical coupler. The cathode end of the D6 outputs VCC direct current voltage between the 'ground' of the weak current circuit part; the anode terminal of D23 outputs 12V DC voltage between the "ground" of the weak current circuit part. The high-voltage or strong-current circuit and the weak-current or low-voltage circuit part of the switching power supply circuit are designed on the power circuit board.

For further detailed understanding of the operating principle of this part of the circuit of the switching power supply, it is necessary to understand the related operating principle and knowledge of the switching power supply and the TOP264VG switching power supply control chip, which are in space, and only a brief description is made here; in a word, the switch power supply control circuit part can respectively obtain VCC-12V power supply voltage at two output voltage circuit parts of the switch power supply circuit. For use with various other devices and circuits. For example, a voltage between VCC and-12V supplies 24V DC high speed FAN FAN 1; to the K1A relay control circuit. According to the circuit and principle of the switching power supply part, the utility model does not adopt a general control transformer and a related voltage conversion circuit to generate the two power supply voltages. The circuit takes +310V from the main loop. The volume and size, the weight of switching transformer are far less than general control transformer, and this just reduces the utility model discloses the cost of welding machine has promoted the technological added value of welding machine.

The utility model discloses a switching power supply circuit has following advantage: under the condition of power grid voltage fluctuation, even in the voltage fluctuation range of 130 VAC-270 VAC, the switching power supply circuit can still generate stable VCC-12V power supply voltage. This ensures the normal operation of other control circuits of the welder. Experiments show that: under the action of the control circuit of the utility model, when the input power voltage of the power grid is lower, such as 130VAC, a thin welding rod is adopted, and the welding machine can also carry out normal welding; if the power supply voltage rises to no more than 270VAC, the welding performance of the welder is not affected. Therefore, the network voltage fluctuation resistance of the welding machine is improved, and the application range of the welding machine is expanded. Therefore, the problem of poor net pressure fluctuation resistance is solved.

FIG. 6 is a schematic diagram of the drive circuit portion on the power board of the welder. The drive circuit mainly controls the IGBT switch in the inverter circuit through the drive circuit under the action of PWM (pulse width control signal) generated by a 32-bit U2 microprocessor. The composition of the driving circuit comprises two parts of circuits: one part of the design is arranged on the power board, and the other part of the design is arranged on the control board. The control board circuit part belongs to a low-voltage or weak-current control part, the power board circuit part belongs to a high-voltage or strong-current control part, and the electrical isolation of the two parts is realized by a QDB driving transformer. Therefore, the reliability of the operation of the two circuit portions can be secured. 2 IGBTs and 2 driving circuits (4 can be used according to different output currents of the welding machine, each 2 is a group and is used in parallel, the circuit board design needs to be synchronously modified, and the driving circuit form of each part is basically consistent. Specific driving circuits are described as follows: 1) in fig. 6, the driving circuit on the power board is a circuit composed of a QDB driving transformer (divided into a primary and two secondary) and diodes D9-D10, resistors R9-R12, and capacitors SC 1-SC 2 at the periphery thereof. The circuit design of this part is laid out on the power board. As shown in fig. 6 and 7, the primary PWMA and PWMB of the QDB drive transformer are connected to

pins

5 and 6, respectively, of the receptacle MB on the power board. The control board can be correspondingly connected with the

pins

5 and 6 of the socket ZB on the control board through a connecting wire or a control wire, and finally connected with a driving circuit on the other part of the control board; the control terminals of G1 and E1 and the control terminals of G2 and E2 are respectively connected to corresponding IGBTs in the half-bridge inverter circuit in the attached figure 2. The IGBT can be controlled to be switched on and off under the action of the control signal, so that the inversion transformation is realized; 2) in the figure 8, a driving circuit on a control board consists of a U3 and U4 (SVD 1055 SA) driving chip, triodes Q1-Q6, voltage-regulator tubes Z1-Z2, diodes D5-D6, resistors R11-R19, capacitors C8-C11 and C14-C15, and the driving circuit is divided into two parts. One ends of the capacitors C14 and C15 are connected with a circuit power supply VCC, and the other ends are connected with the ground end of the circuit power supply. The ends of D1 and D2 of the U3 (SVD 1055 SA) driving chip are connected together and connected with a parallel circuit consisting of a resistor R15, a capacitor C9 and a capacitor C10. The rear end of the parallel circuit of the resistor R15, the capacitor C9 and the capacitor C10 is a PWMA control end which is connected to a pin 5 of a ZB socket on a control board. The D1 and D2 terminals of the U4 driver chip are connected together and are connected with the PWMB control terminal, which is connected to the 6-pin ZB socket on the control board. A control line connected with the ZB socket is correspondingly connected with the MB socket on the power board to realize the connection with the other part of the driving circuit on the power board; s1 of U3 connects VCC; s2 is connected to ground; one end of a resistor R11 is connected with a pin 18 of a 32-bit U2 microprocessor (STM 32F030K6T 6), the other end of the resistor R11 is connected with a base electrode of an NPN type triode Q1, an emitter electrode of Q1 is respectively connected with a collector electrode and a ground end of a PNP type triode Q3, a collector electrode of Q1 is respectively connected with a base electrode of resistors R12 and Q3 and a base electrode of an NPN type triode Q2, the other end of R12 and a collector electrode of Q2 are connected with VCC, a resistor R13 is connected between an emitter electrode of Q2 and an emitter electrode of Q3, an emitter electrode of Q3 is connected with a G2 end of a U3 driving chip, an emitter electrode of Q2 is respectively connected with an anode end of a capacitor C8 and a stabilivolt Z1, and the other end of a capacitor C8 is connected with a; the anode of the diode D5 is connected with VCC, the cathode of the diode D5 is connected with the resistor R14, and the other end of the resistor R14 is connected with the G1 end of the U3 driving chip; similarly, one end of a resistor R18 is connected with the 19 pin of the U2 microprocessor, the other end of the resistor R18 is connected with the base of an NPN type triode Q4, the emitter of the Q4 is respectively connected with the collector of a PNP type triode Q6 and the ground, the collector of a Q4 is respectively connected with the bases of resistors R19 and Q6 and the base of an NPN type triode Q5, the other end of R19 and the collector of Q5 are connected with VCC, a resistor R17 is connected between the emitter of Q5 and the emitter of Q6, the emitter of Q6 is connected with the G2 end of a U4 driving chip, the emitter of Q5 is respectively connected with the anode ends of a capacitor C11 and a stabilivolt Z2, and the other end of a capacitor C11 is connected with the cathode of a Z2 and is connected with the G; the anode of the diode D6 is connected with VCC, the cathode of the diode D6 is connected with the resistor R16, and the other end of the resistor R16 is connected with the G1 end of the U4 driving chip; the circuit structure forms of two parts of a driving circuit on a control board are basically completely consistent, and the difference is that a front-stage circuit at the control end of the PWMA is a parallel circuit of three devices, namely a resistor R15, a capacitor C9 and a capacitor C10; on the control board, input control signals to the drive circuit are finally output by pins 18 and 19 of the U2 by a 32-bit U2 microprocessor according to control software and algorithms. The control signal input by the driving circuit is a group of square wave pulse signals. The square wave pulse signal has a fixed frequency. Is one of important parameters for guaranteeing the work of the IGBT switch. This time is determined by the software parameter settings of the U2 chip. The disclosure of the disclosure and the technical secrecy is not repeated here. It should be noted that: the PWM signal is a signal for determining the output voltage and current of the main inverter circuit of the welding machine.

FIG. 7 is a schematic diagram of the interface circuit portions on the power and control boards of the welder. In fig. 7, the MB interface is designed on the power board. And the ZB interface is designed on the control board. The two are connected together according to the corresponding relationship. FIG. 8 is a schematic diagram of the control circuit portion of a 32-bit microprocessor on the control board of the welder. Fig. 5 is a portion of the control board circuitry, which is a typical voltage regulator circuit in which the +3.3V dc voltage generated is supplied to the two microprocessor circuits on the control board for operation.

In fig. 7, the interface with SIP3 × 2 symbol is the control program programming interface of the 32-bit U2 microprocessor. A pin 1 of the interface is connected with an NRTS end of U2, a pin 2 of the interface is connected with an SWCLK end of U2, a pin 3 of the interface is connected with a SWDIO end of U2, pins 4 and 6 of the interface are connected with +3.3V, and a pin 5 of the interface is connected with ground. The well-written control software is written into the U2 microprocessor through the interface.

The 32-bit microprocessor control circuit part mainly comprises a current setting circuit part, a current feedback circuit part, a welding method selection and state indication circuit part, a digital PI (proportion + integration) operation control circuit part and a PWM (pulse width) operation control circuit part, and the structure of a specific circuit is as follows: the 1 pin and the 5 pin of the 32-bit U2 microprocessor are connected with +3.3V and connected with a capacitor C3 to be grounded; the pin 17 of the U2 is connected with +3.3V and connected with a capacitor C7 to be grounded; pin 31 and pin 2 of U2 are grounded; pin 23 of U2 is a SWDIO terminal; pin 24 of U2 is a SWCLK terminal; a pin 4 of U2 is an NRTS terminal, a pin 4 of U2 is connected with a resistor R3 and is connected to +3.3V through R3, a pin 4 of U2 is connected with a capacitor C1-1 and is connected to the ground through C1; the resistor R28 is connected with a Chang (TIG argon arc welding/MMA manual welding) selection key in series, one end of the Chang key is grounded, the other end of the Chang key is also connected with the resistor R27 and is connected to the pin 2 of the U2 through the R27, and the other end of the R28 resistor is connected with + 3.3V; an IF1 current feedback signal end from a current detection transformer T3 connected in series in an inverter circuit is connected to one end of an alternating current input end of a D1-D4 diode full bridge rectifier through a resistor R4, an IF2 current feedback signal of the current detection transformer is connected to the other end of the alternating current input end of the D1-D4 diode full bridge rectifier through a resistor R5, a negative polarity output end of the rectifier is grounded, a positive polarity output end of the rectifier is connected with a resistor R2 and is connected to pins 6 and 7 of a U2 microprocessor through a R2 resistor, and a capacitor C1, a resistor R1 and a R1+ are connected between the positive and negative polarity output ends of the rectifier in parallel; the resistor R7-1 IS connected with the RI current adjusting potentiometer in series, the other end of the resistor R7-1 IS connected with +3.3V, the middle sliding or variable end (AD-IS end) of the RI current adjusting potentiometer IS respectively connected with the capacitor C5, the resistor R8 and the resistor R10, the other end of the capacitor C5 IS grounded, the other end of the resistor R8 IS connected with the 9 pin of the U2 microprocessor, the other end of the resistor R10 IS connected with the sampling signal end (3 pin of U5) of the display circuit 8-bit MCU microprocessor U5 (STM 8S003F 3), and the other end of the RI current adjusting potentiometer IS grounded; the pin 10 of the U2 microprocessor is respectively connected with a capacitor C4, a resistor R7 and a resistor R6, the other ends of the capacitor C4 and the resistor R7 are grounded, and the other end of the resistor R6 is connected with + 3.3V; the 14 feet of the U2 microprocessor are connected with the anode of an LED diode indicator lamp of an MMA manual welding method, the 15 feet of the U2 are connected with the anode of an LED diode indicator lamp of a TIG argon arc welding method, the 26 feet of the U2 are connected with the anode of a VRD diode LED indicator lamp, the 27 feet of the U2 are connected with the anode of an OP or O.H overheating protection LED diode indicator lamp, and the cathodes of the four indicator lamps are connected with the 20 feet of the U2 microprocessor; the PWM (pulse width control signal) output by pins 18 and 19 of U2 is connected to the drive circuit of the IGBT through resistors R11 and R18, respectively; after 8 pins (P-T ends) of the U2 microprocessor chip are connected with resistors R26, R25 and R24 which are connected in series, the other end of the R24 is connected with 13 pins of an 8-bit microprocessor U5 in the display circuit, the middle node of the resistor R26 and the R25 is connected with a capacitor C23 and then grounded, and the middle node of the resistor R25 and the R24 is connected with a capacitor C22 and then grounded.

In fig. 7, 8 and 9, RT1 and RT2 sockets or terminal wires are connected to the overheat protector. The overheat protector is installed on an aluminum radiator of the IGBT on the power board. The control circuit of the 8-bit U5 microprocessor judges whether the welder is overheated or not by detecting the level states of the 19 pin and the 20 pin of the U5 microprocessor under the action of control software. If an overheating event is detected, a P-T level signal is sent via pin 13 of the U5 microprocessor. Under the action of control software, the control circuit of the 32-bit U2 microprocessor can judge whether the welder is overheated or not by detecting the 8-pin or P-T level state of the U2 microprocessor. If the overheating phenomenon is detected, the output of the digital PWM signal is stopped, namely the output of the welding machine is stopped, so that the overheating protection control is realized. OP (O.H) is an overheat protection indicator lamp, which is installed on the control board of the welder. When the overheating phenomenon occurs, the lamp is lighted. The TIG light emitting diode is a TIG welding or argon arc welding indicator lamp and is arranged on a control panel of the welding machine. The MMA light emitting diode is MMA welding or manual arc welding indicator light and is also arranged on a control board of the welding machine. CHANG is a TIG (argon arc welding)/MMA (manual arc welding) welding method selection key or a touch key. RI is the current regulating potentiometer of the welder. A circuit formed by a 32-bit U2 microprocessor and peripheral devices thereof is a control circuit and is one of core circuits on the control board. The current given signal given by the RI current adjusting potentiometer is input to a 9-pin signal sampling end of a 32-bit U2 microprocessor through a resistor R8 and the like, and is detected and sampled by the 32-bit microprocessor to obtain a current given value Ug required by the output current negative feedback PI (proportion + integration) digital operation of the 32-bit processor, on the other hand, the current given signal is also transmitted to a 3-pin of an 8-bit microprocessor of a display control circuit through a resistor R10 in the figure 9, and the latter can determine the current value displayed by a nixie tube under the action of a control program through sampling; IF1 and IF2 current feedback signals detected by a current transformer T3 are rectified and converted by D1-D4 to obtain negative feedback signals controlled by output current, the current negative feedback signals are input to 6 and 7 pin signal sampling ends of a 32-bit U2 microprocessor through a resistor R2, the 32-bit microprocessor is used for detecting and sampling to obtain a current negative feedback value Ufi required by 32-bit processor output current negative feedback digital PI operation, and then the current negative feedback value Ufi is compared with a given Ug current signal in the 32-bit U2 microprocessor under the action of control software. The Uk control signal output by the U2 microprocessor control software determines the signal output by the digital PWM (pulse width control) operation of the U2 bit microprocessor U2 control software, namely the PWM pulse width signal output by the signal terminals of

pins

18 and 19 of the U2 microprocessor. The two groups of signals have certain working frequency and certain dead time, and the time width of the pulse signals depends on the current given and current negative feedback parameter values participating in PI operation. When parameters of the Ug current given signal and the current negative feedback Ufi signal are changed, the time width of the PWM pulse signal is changed, and finally, the output voltage and the current of the welding machine are adjusted and controlled by controlling an IGBT switch in the inverter main circuit so as to meet the performance control requirement of manual electric arc or argon arc welding. If the signal detected by the current transformer T3 is too large, namely, the overcurrent phenomenon occurs, the control circuit can close the pulse output of PWM, so that the welding machine stops outputting current, and the overcurrent protection is realized.

FIG. 9 is a schematic diagram of the 8-bit microprocessor control circuit portion on the welder control board. That is, the display control circuit part mainly comprises a nixie tube circuit, a nixie tube LED drive circuit and an 8-bit MCU microprocessor control circuit part, and the structure of the specific circuit is as follows: in FIG. 9, U5 is an 8-bit MCU singlechip (STM 8S003F 3). DISPLAY is a digital tube component (e.g., CPS03631AG or AR). TM1652 is an LED driving chip of a nixie tube. The 1 pin of the nixie tube is connected to the 8 pins of the driving chip, the 2 pins of the nixie tube are connected to the 7 pins of the driving chip, the 3 pins of the nixie tube are connected to the 5 pins of the driving chip, the 4 pins of the nixie tube are connected to the 4 pins of the driving chip, the 5 pins of the nixie tube are connected to the 2 pins of the driving chip, the 7 pins of the nixie tube are connected to the 3 pins of the driving chip, the 8 pins of the nixie tube are connected to the 15 pins of the driving chip, the 9 pins of the nixie tube are connected to the 14 pins of the driving chip, the 10 pins of the nixie tube are connected to the 6 pins of the driving chip, the 11 pins of the nixie tube are connected to the 9; the 10 pins of the nixie tube driving chip are grounded, the 1 pin is connected with +3.3V, and the +3.3V power supply end is grounded through a capacitor C25; the 16 pins of the nixie tube driving chip are respectively connected with the 2 pins of the U5 and the resistor R30, and the other end of the resistor R30 is connected with + 3.3V; the 3-pin connection resistor R10 of the U5 IS connected with the middle sliding end (AD-IS end) of the current regulation potentiometer in the figure 8 through a resistor R10; the 4 pins of the U5 are connected with the 4 pins of the SWIM program programming interface, and simultaneously connected with a resistor R29 and a capacitor C24, the other end of the resistor R29 is connected with +3.3V and the 1 pin of the programming interface, and the other end of the capacitor C24 is grounded; the 3 pin of the SWIM programming interface is grounded, and the 2 pin of the programming interface is connected with the 18 pin of the U5 microprocessor; pin 7 of U5 is connected to ground; the pin 8 of U5 is connected with capacitor C20 and then grounded; the pin 9 of the U5 is connected with +3.3V, and is grounded through a capacitor C21; the pin 13 of the U5 is connected with the serially connected resistors R24, R25 and R26 and then connected with the pin 8 (P-T end) of the 32-bit U2 microprocessor chip in the figure 8, the middle node of the resistor R26 and the R25 is connected with the capacitor C23 and then grounded, and the middle node of the resistor R25 and the R24 is connected with the capacitor C22 and then grounded; a pin 19 of the U5 is respectively connected with a capacitor C19 and a resistor R23, the other end of the capacitor C19 is grounded, the other end of the resistor R23 is respectively connected with a capacitor C18, a resistor R22 and an RT1 end, the other end of the capacitor C18 is grounded, the other end of the resistor R22 is connected with +3.3V, and the RT1 end is connected to a pin 1 corresponding to a ZB socket on the control board; 20 feet of the U5 are respectively connected with a capacitor C17 and a resistor R21, the other end of the capacitor C17 is grounded, the other end of the resistor R21 is respectively connected with a capacitor C16, a resistor R20 and an RT2 end, the other end of the capacitor C16 is grounded, the other end of the resistor R20 is connected with +3.3V, and the RT2 end is connected to 2 feet corresponding to a ZB socket on the control board.

In fig. 9, the interface with the SWIM symbol is the control program programming interface of an 8-bit U5 microprocessor. The well-written control software is written into the U5 microprocessor through the interface.

Under the action of the DISPLAY control circuit of the 8-bit U5 microprocessor and the control software thereof, the DISPLAY nixie tube can DISPLAY the current parameter value of the welding machine by matching with the current adjusting potentiometer on the control panel of the welding machine.

How two MCU microprocessors work in particular involves much knowledge of the microprocessor control, and needs to be known about the relevant information. The description of the relationship between the sections is not repeated here.

In fig. 8 and 9, RT1 and RT2 sockets or terminal wires are connected to the overheat protector. The overheat protector is installed on an aluminum radiator of the IGBT on the power board. The control circuit of the 8-bit U5 microprocessor judges whether the welding machine is overheated or not by detecting the level states of the 19 pin and the 20 pin of the U5 microprocessor. Under the control software, if an overheating event is detected, a P-T level signal is sent via pin 13 of the U5 microprocessor. Under the action of control software, the control circuit of the 32-bit U2 microprocessor can judge whether the welder is overheated or not by detecting the 8-pin or P-T level state of the U2 microprocessor. If an overheating event is detected, the output of the digital PWM signal, i.e., the output of the welder, is stopped. Under the action of a cooling fan of the welding machine, when the temperature of the IGBT radiator is reduced to a certain degree or when the overheating phenomenon in the welding machine is eliminated, the control circuit can continue to output the PWM control signal. While the overheat indicator lamp is turned off. This achieves welder overtemperature protection control.

The simple control process of the output characteristic of the manual electric arc welding of the welding machine of the utility model is illustrated by taking manual welding as an example, which is briefly described as follows:

after the switch S1 on the back panel of the welder is closed to switch on the power supply source for a short time (during this time, the welder circuit is powered on and buffered, and has a certain time delay control), the control boards inside the welder work in a charged mode. The MMA manual welding can be selected through a welding method key on the front panel, and of course, the VRD function can be further selected under the condition that the MMA is selected. The VRD function represents the low no-load voltage output of the welding machine, namely the direct current voltage below 20V is output by the welding machine under the condition of no welding, and the operation safety of a welding machine user is further ensured. If VRD is not selected, a microprocessor digital PWM pulse width control circuit in the welding machine generates a pulse signal with a large duty ratio, so that a drive circuit of the IGBT works, the IGBT is in an alternative 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 detects the mutual inductor through the T3 current, and the output current signal can be detected. After signal processing, the signal is used as a current negative feedback control signal to be compared with a digital PI link of welding current given signals in 32-bit microprocessing. And the compared difference signal is subjected to digital PI regulation control and then is input into the digital PWM control of the microprocessor, and the result is output PWM control signals which have certain pulse width or duty ratio, so that the output current and voltage of the welding machine are determined, and the accurate control of the output current parameters is realized. And the output characteristic of the welding machine meets the requirement of manual arc welding. Further, when the welding current given signal is unchanged, the current detected by the welding machine 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 increase of the current, and after the digital PI control, the pulse width or the duty ratio of the output PWM signal 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 which is active only when the current has reached the set value Ug of the welding current potentiometer. Thereafter, as the current increases slightly, the voltage decreases much. When the voltage drops below a certain value, the control circuit can increase the pulse width or the duty ratio of the digital PWM along with the reduction of the voltage, so that the welding current is increased according to set parameters, and finally the dropping characteristic of constant current band dragging is formed. The practical test result shows that: the thrust current of the welding machine of the utility model is about dozens of A (ampere). The current cutoff negative feedback set point is different when the welding current set signal changes, but the other control processes are similar. In this way, between the minimum and maximum potentiometer settings, numerous droop characteristics can be obtained. Such control is also a basic requirement for satisfying manual arc welding. For further understanding of the current feedback, digital PI and PWM and output characteristic control processes, reference may be made to other related control principle descriptions. The argon arc welding output control is similar to that of manual welding, except that the output current is not controlled by external dragging current under low voltage. Therefore, the control of the argon arc welding will not be described here.

The above is the explanation of the welding machine of the present invention. Because the utility model discloses the detailed structural design and the circuit schematic diagram of attached figure 1~ attached figure 9 and PCB board component screen printing overall arrangement have been given, consequently, to the people that has welding machine structure and circuit reading ability (or possess relevant knowledge), can read completely. The circuit diagram is a silent language. However, even if more are explained, they are difficult for people without circuit reading ability (or knowledge of the associated circuits). In view of the space, only the major portions of the disclosure are set forth herein to provide the reader with a better understanding of the relevant principles of operation and processes.

As can be seen from the above description, the present invention has its own unique design ideas and methods. Not only realized the manual welding of welding machine and control such as argon arc welding method output, moreover, the control circuit who designs, including their circuit board and the relation of connection each other to and the complete machine structural design of welding machine, all make the utility model discloses the welding machine product has the root cause place of technical advantages such as control performance is good, welding machine compact structure, also is the important guarantee that satisfies product high efficiency and low-cost production, high reliability, manufacturing process technical advancement. The protection content of the utility model discloses a patent application just lies in protecting the structure and the control circuit design of this kind of welding machine.

The above is a detailed description of the present invention in connection with specific welder configurations and circuits and control functions, and it is not to be construed that the practice of the present invention is limited to those descriptions. It is right other technical personnel in technical field do not deviate from the utility model discloses under the prerequisite of design, can also make a plurality of other deductions and transform, these all should regard as belonging to the utility model discloses the scope of protection.

Claims

1. A double-MCU digital PI and PWM control multifunctional welding machine mainly comprises a shell part and an internal control part, wherein the shell part comprises a front panel, a chassis bottom plate, a chassis outer cover or a shell and a rear panel; the internal control part mainly comprises a drive circuit part, and is characterized in that: the drive circuit part comprises two parts of circuits, wherein one part of the circuit is used for designing a power board circuit arranged on a power board, and the other part of the circuit is used for designing a control board circuit arranged on a control board; the control panel circuit part belongs to a low-voltage or weak-current control part, the power panel circuit part belongs to a high-voltage or strong-current control part, and the two parts are electrically isolated by a QDB driving transformer; the driving circuit on the power board comprises a QDB driving transformer and a circuit consisting of diodes D9-D10, resistors R9-R12 and capacitors SC 1-SC 2 on the periphery of the QDB driving transformer, and the circuit of the QDB driving transformer is laid on the power board; the primary PWMA and PWMB ports of the QDB driving transformer are respectively connected to the 5 pins and the 6 pins of the socket on the power board, can be correspondingly connected with the 5 pins and the 6 pins of the socket on the control board through connecting wires or control lines, and are finally connected with a driving circuit on the other part of the control board; 2) the driving circuit on the control board comprises a driving chip U3, a driving chip U4, triodes Q1-Q6, voltage-regulator tubes Z1-Z2, diodes D5-D6, resistors R11-R19, capacitors C8-C11 and C14-C15, the circuit is divided into two parts, one ends of the capacitors C14 and C15 are connected with a circuit power supply VCC, and the other ends of the capacitors C14 and C15 are connected with the ground end of the circuit power supply; the ends D1 and D2 of the driving chip U3 are connected together and are connected with a parallel circuit consisting of a resistor R15, a capacitor C9 and a capacitor C10; the rear end of a parallel circuit of three devices of a resistor R15, a capacitor C9 and a capacitor C10 is a PWMA control end and is connected to a pin 5 of a socket on a control board; the D1 and D2 ends of the U4 driving chip are connected together and connected with the control end of the PWMB, and the PWMB is connected to the 6 pins of the socket on the control board; the control line connected with the socket is correspondingly connected with the socket on the power board to realize the connection with the other part of the driving circuit on the power board; s1 of the driving chip U3 is connected with VCC; s2 of the driver chip is connected to ground; one end of a resistor R11 is connected with the 18 pin of a 32-bit U2 microprocessor, the other end of the resistor R11 is connected with the base of an NPN triode Q1, the emitter of the Q1 is respectively connected with the collector of a PNP triode Q3 and the ground end, the collector of a Q1 is respectively connected with the bases of resistors R12 and Q3 and the base of an NPN triode Q2, the other end of R12 and the collector of Q2 are connected with VCC, a resistor R13 is connected between the emitter of Q2 and the emitter of Q3, the emitter of Q3 is connected with the G2 end of a U3 driving chip, the emitter of Q2 is respectively connected with the anode ends of a capacitor C8 and a voltage regulator Z1, the other end of a capacitor C82 8 is connected with the cathode of Z1 and is connected with the G86; the anode of the diode D5 is connected with VCC, the cathode of the diode D5 is connected with the resistor R14, and the other end of the resistor R14 is connected with the G1 end of the U3 driving chip; similarly, one end of a resistor R18 is connected with the 19 pin of the U2 microprocessor, the other end of the resistor R18 is connected with the base of an NPN type triode Q4, the emitter of the Q4 is respectively connected with the collector of a PNP type triode Q6 and the ground, the collector of a Q4 is respectively connected with the bases of resistors R19 and Q6 and the base of an NPN type triode Q5, the other end of R19 and the collector of Q5 are connected with VCC, a resistor R17 is connected between the emitter of Q5 and the emitter of Q6, the emitter of Q6 is connected with the G2 end of a U4 driving chip, the emitter of Q5 is respectively connected with the anode ends of a capacitor C11 and a stabilivolt Z2, and the other end of a capacitor C11 is connected with the cathode of a Z2 and is connected with the G; the anode of the diode D6 is connected with VCC, the cathode of the diode D6 is connected with the resistor R16, and the other end of the resistor R16 is connected with the G1 end of the U4 driving chip; the circuit structure forms of two parts of a driving circuit on a control board are basically completely consistent, and the difference is that a front-stage circuit at the control end of the PWMA is a parallel circuit of three devices, namely a resistor R15, a capacitor C9 and a capacitor C10; on the control board, input control signals to the drive circuit are finally output by pins 18 and 19 of the U2 by a 32-bit U2 microprocessor according to control software and algorithms.

2. The dual-MCU digital PI and PWM controlled multifunctional welder of claim 1, wherein: the front panel is provided with a positive and negative output quick connector seat assembly and a control panel, and the outer side of the control panel is provided with an overheating protection indicator lamp, a current digital display meter, a VRD function indicator lamp, an argon arc welding and manual arc welding indicator lamp, a welding method selection key, a current regulator, other circuits and electronic components thereof which are designed on the panel in a layout way;

the control panel is arranged in the welding machine and fixed on the front panel; the control board is also provided with control circuit systems which are formed by taking 8-bit and 32-bit singlechips or microprocessors as cores, and the circuit systems mainly comprise a +3.3V direct-current power supply circuit, a manual welding or argon arc welding method selection and inverter circuit output parameter control circuit, a current given parameter and current negative feedback signal detection circuit, an overheating protection control circuit, a current parameter display control circuit and PWM pulse width output regulation and control.

3. The dual-MCU digital PI and PWM controlled multifunctional welder of claim 2, wherein: the power board is provided with a plurality of circuits, electronic components and insulating boards thereof, a connecting piece connected between the negative polarity output end and the power board, a connecting piece connected between the positive polarity output end and the aluminum radiator of the fast recovery diode, two insulating fixing support legs of the power board and connecting leads or control lines between partial circuits.

4. The dual-MCU digital PI and PWM controlled multifunctional welder of claim 1, wherein: the power board circuit part of the power board mainly comprises an upper electricity buffer control circuit, an input rectification and filter circuit, a switching power supply circuit or a working voltage generating circuit, an IGBT drive control circuit, an IGBT half-bridge inversion main circuit and an inversion transformer primary current detection circuit.

5. The dual-MCU digital PI and PWM controlled multifunctional welder as claimed in claim 4, characterized in that: the input rectifying and filtering circuit is connected with a power supply of a power grid through a power switch S1, alternating current from the power grid firstly passes through a PTC thermistor and then is rectified by a B1 rectifier bridge to be changed into pulsating direct current, then electrolytic capacitors of EC 1-EC 2 are charged, the voltage on the electrolytic capacitors of EC 1-EC 2 is gradually increased and finally is changed into more stable direct current of +310V, the electrolytic capacitors of EC 1-EC 2 play a role in filtering, and the resistors R7 and R8 are mainly used for releasing high voltage stored in the electrolytic capacitors of EC 1-EC 2 when the welding machine is not electrified to work, so that the electric shock phenomenon on a human body is prevented; the capacitor CC3 is an input anti-interference filter capacitor, and a contact K1B of the relay is connected in parallel with two ends of the PTC thermistor and forms a power-on buffer circuit together with the relay K1A.

6. The dual-MCU digital PI and PWM controlled multifunctional welder as claimed in claim 5, characterized in that: the +310V direct current is supplied to a half-bridge inverter main circuit consisting of IGBT 1-IGBT 2 tubes, a T1 inverter main transformer (9), D1-D3 fast recovery diodes, a T3 primary bus current detection transformer, a converter capacitor CC1 and CC 2.

7. The dual-MCU digital PI and PWM controlled multifunctional welder as claimed in claim 5, characterized in that: the +310V direct current is supplied to a switching power supply circuit which consists of a T2 switching power supply transformer, TVS, Z and Z1-Z2 voltage-stabilizing tubes, D4-1, D4, D6 and D23 diodes, an IC1 switching power supply control chip, and resistors R1-R5, R21, capacitors C1-C4, EC3, EC5 and an optocoupler U2 around the switching power supply circuit; the switch power supply circuit generates VCC-12V power supply voltage and supplies the VCC-12V power supply voltage to other control circuits and the like for live working; the circuit formed by a primary winding N1 and a secondary winding N4 of the T2 switching power supply transformer, TVS, a Z voltage regulator tube, diodes D4 and D4-1, resistors R1 and R21, capacitors C1-C2, EC5 and an IC1 switching power supply control chip around the primary winding N1 and the secondary winding N4 are connected to +310V through a plug J1 and belong to a high-voltage or strong-current loop; in order to ensure the safety of a control circuit, a U2 photoelectric coupler is adopted for isolation, and a weak current or low-voltage circuit part of a switching power supply part consists of secondary windings N2 and N3 of a T2 switching power supply transformer, and a U2A light-emitting diode part of D6 and D23 diodes, Z1-Z2 voltage-stabilizing tubes, resistors R2-R5, capacitors C3-C4, EC3 and U2 optical couplers around the secondary windings; the cathode end of the D6 outputs VCC direct current voltage between the 'ground' of the weak current circuit part; the anode end of D23 outputs-12V DC voltage between the earth of the weak current circuit part; the high-voltage or strong-current circuit and the weak-current or low-voltage circuit part of the switching power supply circuit are arranged on the power board.

8. The dual-MCU digital PI and PWM controlled multifunctional welder of claim 2, wherein: the control panel comprises a 32-bit microprocessor control circuit, the 32-bit microprocessor control circuit mainly comprises a current giving part, a current feedback part, a welding method selection and state indication part, a digital PI operation part and a PWM operation control circuit part, and the structure of the specific circuit is as follows: the 1 pin and the 5 pin of the 32-bit U2 microprocessor are connected with +3.3V and connected with a capacitor C3 to be grounded; the pin 17 of the U2 is connected with +3.3V and connected with a capacitor C7 to be grounded; pin 31 and pin 2 of U2 are grounded; pin 23 of U2 is a SWDIO terminal; pin 24 of U2 is a SWCLK terminal; a pin 4 of U2 is an NRTS terminal, a pin 4 of U2 is connected with a resistor R3 and is connected to +3.3V through R3, a pin 4 of U2 is connected with a capacitor C1-1 and is connected to the ground through C1; the resistor R28 is connected with the CHANG selection key in series, one end of the CHANG key is grounded, the other end of the CHANG key is also connected with the resistor R27 and is connected with the pin 2 of the U2 through R27, and the other end of the resistor R28 is connected with + 3.3V; an IF1 current feedback signal end from a current detection transformer T3 connected in series in an inverter circuit is connected to one end of an alternating current input end of a D1-D4 diode full bridge rectifier through a resistor R4, an IF2 current feedback signal of the current detection transformer is connected to the other end of the alternating current input end of the D1-D4 diode full bridge rectifier through a resistor R5, a negative polarity output end of the rectifier is grounded, a positive polarity output end of the rectifier is connected with a resistor R2 and is connected to pins 6 and 7 of a U2 microprocessor through a R2 resistor, and a capacitor C1, a resistor R1 and a R1+ are connected between the positive and negative polarity output ends of the rectifier in parallel; the resistor R7-1 is connected with the RI current adjusting potentiometer in series, the other end of the resistor R7-1 is connected with +3.3V, the middle sliding or variable end of the RI current adjusting potentiometer is respectively connected with the capacitor C5, the resistor R8 and the resistor R10, the other end of the capacitor C5 is grounded, the other end of the resistor R8 is connected with the 9 pin of the U2 microprocessor, the other end of the resistor R10 is connected with the sampling signal end of the 8-bit MCU microprocessor U5 of the display circuit, and the other end of the RI current adjusting potentiometer is grounded; the pin 10 of the U2 microprocessor is respectively connected with a capacitor C4, a resistor R7 and a resistor R6, the other ends of the capacitor C4 and the resistor R7 are grounded, and the other end of the resistor R6 is connected with + 3.3V; the 14 feet of the U2 microprocessor are connected with the anode of an LED diode indicator lamp of an MMA manual welding method, the 15 feet of the U2 are connected with the anode of an LED diode indicator lamp of a TIG argon arc welding method, the 26 feet of the U2 are connected with the anode of a VRD diode LED indicator lamp, the 27 feet of the U2 are connected with the anode of an overheat protection LED diode indicator lamp, and the cathodes of the four indicator lamps are connected with the 20 feet of the U2 microprocessor; the PWM output by the pin 18 and the pin 19 of the U2 is connected to a driving circuit of the IGBT through resistors R11 and R18 respectively; the 8 pins of the U2 microprocessor chip are connected with the resistors R26, R25 and R24 which are connected in series, the other end of the R24 is connected with the 13 pin of the 8-bit microprocessor U5 in the display circuit, the middle node of the resistor R26 and the R25 is connected with the capacitor C23 and then grounded, and the middle node of the resistor R25 and the R24 is connected with the capacitor C22 and then grounded.

9. The dual-MCU digital PI and PWM controlled multifunctional welder of claim 2, wherein: the overheat protection control circuit also comprises an overheat protector, and the overheat protector is arranged on an aluminum radiator of the IGBT on the power board; the control circuit of the 8-bit U5 microprocessor judges whether the welder has an overheating phenomenon or not by detecting the level states of the 19 pin and the 20 pin of the U5 microprocessor under the action of control software, if the overheating phenomenon is detected, a P-T level signal is sent out by the 13 pin of the U5 microprocessor, and the control circuit of the 32-bit U2 microprocessor can judge whether the welder has the overheating phenomenon or not by detecting the 8 pin or the P-T level state of the U2 microprocessor under the action of the control software; if the overheating phenomenon is detected, the output of the digital PWM signal is stopped, namely the output of the welding machine is stopped, so that the overheating protection control is realized.