Current control circuit of electric welding machine and electric welding machine

Abstract

The present application discloses a current control circuit and a welding machine for a welding machine. The current control circuit includes a transformer, a welding current control module, and a welding load module. The transformer receives the voltage input by the power supply system and outputs it to the welding current control module. The welding current control module is respectively connected to the transformer and the welding load module to control the average current value of the welding load module. The present application provides a new architecture for a welding machine. By controlling the average current magnitude at the welding point or the position of the welding load through the welding current control module, it is possible to avoid the problems of increased power, increased energy consumption, increased heat generation, affecting or damaging other component structures in the vicinity, causing the welding machine to burn out, and short service life.

Description

Technical Field

[0001] This application relates to the technical field of welding machines, and particularly to a current control circuit and a welding machine for a welding machine. Background Art

[0002] The traditional aging method for welding machines is to use high-power resistors as simulated loads for burn-in aging. The load resistor aging method dissipates all the output power of the welding machine in the air in the form of heat, which causes a great waste of electrical energy; due to the different output voltage and current specifications of different welding machines, different load resistors need to be equipped, which leads to a large amount of manual labor to switch different load resistors according to different output specifications of the welding machine before aging, resulting in a waste of manpower; since the load resistor generates a large amount of heat, causing the environmental temperature to rise, this will reduce the insulation of surrounding equipment, thereby shortening its service life.

[0003] How to control the welding current of the welding machine to control other effects caused by excessive heat generation of the welding machine has become an urgent problem to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a current control circuit and a welding machine for a welding machine, to control the magnitude of the welding current at the load, and to avoid damage to the welding machine caused by excessive current and excessive heat, affecting the service life of spot welding.

[0005] This application discloses a current control circuit for a welding machine. The current control circuit includes a transformer, a welding current control module, and a welding load module. The transformer receives the voltage input from the power supply system and outputs it to the welding current control module. The welding current control module is respectively connected to the transformer and the welding load module to control the average current value of the welding load module.

[0006] Optionally, the transformer is a △ / Y type three-phase transformer. The transformer includes a primary winding, a secondary winding, and a magnetic core disposed between the primary winding and the secondary winding. The secondary winding is connected to the power supply system. The primary winding includes a first end, a second end, and a third end. The welding current control module includes a first bridge arm, a second bridge arm, and a third bridge arm. The first bridge arm includes a first switching power tube and a first resistor. The second bridge arm includes a second switching power tube and a second resistor. The third bridge arm includes a third switching power tube and a third resistor. The first common connection point and the second common connection point of the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to both ends of the welding machine load module. The midpoints of the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the first end, the second end, and the third end of the primary winding.

[0007] Optionally, a first diode is arranged in parallel between the input and output ends of the first resistor, a second diode is arranged in parallel between the input and output ends of the second resistor, and a third diode is arranged in parallel between the input and output ends of the third resistor. The output end of the first diode is connected to the midpoint of the first bridge arm, the output end of the second diode is connected to the midpoint of the second bridge arm, and the output end of the third diode is connected to the midpoint of the third bridge arm. The input end of the first diode, the input end of the second diode and the input end of the third diode are respectively connected to the welding load module through the second common connection point.

[0008] Optionally, the current control circuit further includes a fourth diode, an input end of the fourth diode is connected to the second common connection point, and an output end of the fourth diode is connected to the primary winding.

[0009] Optionally, the welding load module includes a load resistor, one end of the load resistor is connected to the first common connection point, and the other end of the load resistor is connected to the second common connection point.

[0010] Optionally, the welding load module includes a load resistor and a load current detection circuit, one end of the load current detection circuit is connected to the load, and the other end is connected to the welding current control module.

[0011] Optionally, the current control circuit includes a timing control drive module, which is respectively connected to the control ends of the first switch power tube, the second switch power tube and the third switch power tube, and controls the first switch power tube, the second switch power tube and the third switch power tube to be turned on or off in a time-sharing manner; wherein the phase difference between the current waveforms of the first switch power tube, the second switch power tube and the third switch power tube is 120°.

[0012] Optionally, the first switching power tube, the second switching power tube and the third switching power tube are gallium nitride devices of the same model and specification.

[0013] Optionally, the timing control driving module includes a PWM control circuit, the PWM control circuit generates a first drive signal and outputs it to the control end of the first switch power tube, the PWM control circuit generates a first drive signal and outputs it to the control end of the first switch power tube, the PWM control circuit generates a second drive signal and outputs it to the control end of the second switch power tube, and the PWM control circuit generates a third drive signal and outputs it to the control end of the third switch power tube;

[0014] Wherein, the falling edge of the first driving signal and the rising edge of the second driving signal are at the same moment, the falling edge of the second driving signal and the rising edge of the third driving signal are at the same moment, and the time durations between the rising edges and the falling edges of the first driving signal, the second driving signal, and the third driving signal are the same.

[0015] This application also discloses a welding machine, which includes the current control circuit as described in any one of the above, and the current control circuit controls the welding current of the welding machine.

[0016] This application changes the current control circuit of the welding machine, sets up a new architecture of the welding machine, and controls the average current magnitude at the welding point or the position of the welding load through the welding current control module, so as to avoid the increase in the power of the welding machine, the increase in energy consumption, and thus the increase in heat generation, which affects other component structures around. Moreover, this application does not require adding additional circuits or related structures that are heavy and large in volume, and avoids the increase in the weight or volume of the welding machine from affecting its use. Description of the Drawings

[0017] The included drawings are used to provide a further understanding of the embodiments of the present application, which form a part of the specification, are used to illustrate the implementation manners of the present application, and are used to explain the principles of the present application together with the text description. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts. In the drawings:

[0018] Figure 1 is a schematic diagram of a partial circuit structure of an exemplary welding machine of the present application;

[0019] Figure 2 is a schematic diagram of the current control circuit module of the welding machine according to the first embodiment of the present application;

[0020] Figure 3 is a schematic diagram of the current control circuit of the welding machine according to the second embodiment of the present application;

[0021] Figure 4 is a waveform diagram of the power transistor of the current control circuit of the welding machine according to the second embodiment of the present application;

[0022] Figure 5 is a schematic diagram of the working circuit of the current control circuit of the welding machine according to the third embodiment of the present application;

[0023] Figure 6 is a schematic diagram of the current control circuit of the welding machine according to the third embodiment of the present application;

[0024] Figure 7Schematic diagram of the current control circuit of the electric welding machine according to the fourth embodiment of the present application;

[0025] Figure 8 Schematic diagram of the welding load voltage waveform of the current control circuit of the electric welding machine according to the fourth embodiment of the present application;

[0026] Figure 9 Schematic diagram of the structure of the electric welding machine according to the fifth embodiment of the present application.

[0027] Among them, 100, electric welding machine; 200, current control circuit; 300, transformer; 310, primary winding; 320, secondary winding; 330, magnetic core; 400, welding current control module; 410, first bridge arm; 420, second bridge arm; 430, third bridge arm; 440, first common connection point; 450, second common connection point; 500, welding load module; 510, load current detection circuit; 600, timing control drive module; 610, PWM control circuit;

[0028] A1 - first end; A2 - second end; A3 - third end; D1 - first diode; D2 - second diode; D3 - third diode; D4 - fourth diode; M1 - first switching power transistor; M2 - second switching power transistor; M3 - third switching power transistor; RL1 - first resistor; RL2 - second resistor; RL3 - third resistor; R - load resistor. Detailed implementation manners

[0029] It should be understood that the terms, the specific structures and functional details disclosed herein are only for the purpose of describing specific embodiments, which are representative, but the present application can be specifically implemented in many alternative forms and should not be construed as being limited only to the embodiments set forth herein.

[0030] In the description of the present application, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating relative importance or implicitly indicating the number of the indicated technical features. Thus, unless otherwise specified, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features; the meaning of "a plurality" is two or more. The term "comprising" and any deformation thereof mean non-exclusive inclusion, and there may be or add one or more other features, integers, steps, operations, units, components and / or their combinations.

[0031] In addition, terms indicating orientation or positional relationships such as "center", "horizontal", "upper", "lower", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are described based on the orientation or relative positional relationships shown in the drawings. They are only for the purpose of simplifying the description of the present application and do not indicate that the indicated devices or components must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the present application.

[0032] In addition, unless otherwise clearly specified and limited, the terms "install", "connect", and "couple" should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, or the internal communication of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present application can be understood according to specific circumstances.

[0033] The present application will be described in detail below with reference to the drawings and optional embodiments.

[0034] Referring Figure 1 As shown, as an example architecture of a welding machine, it can also avoid excessive power and excessive heat generation that may damage the welding machine. Specifically, this architecture includes a main circuit power supply, the load and circuit corresponding to the transformer, and components such as capacitors. By turning on the upper and lower bridge arms, and determining the conduction angle of thyristors G1 - G according to the current collected by the shunt, this architecture has a simple structure, inexpensive components, and is easy to control. However, due to the characteristics of thyristors, once turned on, when the voltage across the source and drain of the thyristor is not zero, it will not turn off, and the current will keep flowing. And because the welding power of the welding machine is generally very large, it often causes large arc oscillations. When the voltage across the thyristor is at the voltage trough, there is a parasitic oscillation voltage, and this phenomenon will cause the thyristor to be misfired all the time. This is the characteristic of the thyristor, and externally, only the oscillation voltage can be minimized as much as possible, but this phenomenon cannot be completely eliminated.

[0035] Referring Figure 2 As shown, as the first embodiment of the present application, a current control circuit 200 of a welding machine 100 is disclosed. The current control circuit 200 includes a transformer 300, a welding current control module 400, and a welding load module 500. The transformer 300 receives the voltage input from the power supply system and outputs it to the welding current control module 400. The welding current control module 400 is respectively connected to the transformer 300 and the welding load module 500 to control the average current value of the welding load module 500.

[0036] This embodiment proposes a novel architecture for a welding machine 100. The current control circuit 200 in the welding machine 100 is improved. A welding current control module 400 is provided, which is respectively connected to the transformer 300 and the welding load module 500, to control the average current value of the welding load module 500, avoiding the increase in the power of the welding machine 100, the increase in energy consumption, and thus the increase in heat generation, which may affect other component structures around it. Moreover, this application does not require adding additional circuits or related structures that are heavy and large in volume, avoiding the influence on the use due to the increase in the weight or volume of the welding machine 100. Compared with the above example structure, the number of components is reduced, which is beneficial to cost reduction.

[0037] Refer to Figures 3 to 4 As shown, as the second embodiment of this application, it is a further refinement of the above first embodiment. The transformer 300 is a Δ / Y type three-phase transformer 300. The transformer 300 includes a primary winding 310, a secondary winding 320, and a magnetic core 330 provided between the primary winding 310 and the secondary winding 320. The secondary winding 320 is connected to the power supply system. The primary winding 310 includes a first end A1, a second end A2, and a third end A3. The welding current control module 400 includes a first bridge arm 410, a second bridge arm 420, and a third bridge arm 430. The first bridge arm 410 includes a first switching power transistor M1 and a first resistor RL1. The second bridge arm 420 includes a second switching power transistor M2 and a second resistor RL2. The third bridge arm 430 includes a third switching power transistor M3 and a third resistor RL3. The first common connection point 440 and the second common connection point 450 of the first bridge arm 410, the second bridge arm 420, and the third bridge arm 430 are respectively connected to both ends of the welding machine load module. The midpoints of the first bridge arm 410, the second bridge arm 420, and the third bridge arm 430 are respectively connected to the first end A1, the second end A2, and the third end A3 of the primary winding 310. Generally, the welding load module 500 includes a load resistor R, and the load resistor R can also be understood as a welding point. One end of the load resistor R is connected to the first common connection point 440, and the other end is connected to the second common connection point 450. The three resistors are all dummy loads, and the diodes in parallel with them play a role in freewheeling and three-phase current balancing. By polling different time switching power devices, the load can obtain different voltages.

[0038] Generally, the current control circuit 200 includes a timing control driving module 600, which is respectively connected to the control ends of the first switch power tube M1, the second switch power tube M2 and the third switch power tube M3, and controls the first switch power tube M1, the second switch power tube M2 and the third switch power tube M3 to be turned on or off in a time-sharing manner; wherein the phase difference between the current waveforms of the first switch power tube M1, the second switch power tube M2 and the third switch power tube M3 is 120°, the first switch power tube M1, the second switch power tube M2 and the third switch power tube M3 are gallium nitride devices of the same model and specification, which are introduced from a common industrial power grid through a △ / Y-type three-phase transformer 300, and the welding current can be accurately obtained by collecting the current and operating the GaN device, and the power tube is changed from a thyristor to a bidirectionally controlled GaN power tube, which is a switch device that can be bidirectionally turned on and off, so that the control method has a lot of freedom and a lot of freedom in design.

[0039] Furthermore, the present application mainly adopts an AC welding machine architecture, and the average current is obtained by opening the conduction pin or PWM, so the timing control driving module 600 includes a PWM control circuit 610, the PWM control circuit 610 generates a first drive signal and outputs it to the control end of the first switch power tube M1, the PWM control circuit 610 generates a first drive signal and outputs it to the control end of the first switch power tube M1, the PWM control circuit 610 generates a second drive signal and outputs it to the control end of the second switch power tube M2, and the PWM control circuit 610 generates a third drive signal and outputs it to the control end of the third switch power tube M3; wherein the falling edge of the first drive signal and the rising edge of the second drive signal are at the same time, the falling edge of the second drive signal and the rising edge of the third drive signal are at the same time, and the duration between the rising edge and the falling edge of the first drive signal, the second drive signal and the third drive signal are the same.

[0040] like Figures 5 to 6As shown in the figure, as the third embodiment of the present application, it is a further limitation of the above-mentioned second embodiment. A first diode D1 is arranged in parallel between the input end and the output end of the first resistor RL1, a second diode D2 is arranged in parallel between the input end and the output end of the second resistor RL2, and a third diode D3 is arranged in parallel between the input end and the output end of the third resistor RL3. The output end of the first diode D1 is connected to the midpoint of the first bridge arm 410, the output end of the second diode D2 is connected to the midpoint of the second bridge arm 420, and the output end of the third diode D3 is connected to the midpoint of the third bridge arm 430. The input ends of the first diode D1, the second diode D2, and the third diode D3 are respectively connected to the welding load module 500 through the second common connection point 450.

[0041] The current control circuit 200 further includes a fourth diode D4. The input end of the fourth diode D4 is connected to the second common connection point 450, and the output end of the fourth diode D4 is connected to the primary winding 310.

[0042] Specifically, the rising edge moment is the t1 moment, the falling edge moment is the t2 moment, M1 corresponds to the first phase or phase A, M2 corresponds to the second phase or phase B, and M3 corresponds to the third phase or phase C. At the t1 moment of M1, among the remaining two phases, there must be one phase lower than the 0 point. Generally, the third phase is the lowest. So the starting loop is loop ① in the following figure. As time goes by, the voltage difference between the second phase and the third phase gradually decreases. If the voltage of the second phase is equal to that of the third phase, and if this is not the t2 moment at this time, it will become loop ②. Generally, when the voltage of the second phase is equal to that of the third phase, it is the t2 moment and M1 is turned off. When M1 is turned off, at this time, waiting for the t1 moment of M2 to turn on, repeating the working process of M1. After M2 completes this process, M3 starts this process, and then returns to M1, repeating this process. By controlling t1 and t2, the time of each phase during t1 - t2 is made the same, realizing current balance at the load.

[0043] Reference Figure 7 and Figure 8 As shown in the figure, as the fourth embodiment of the present application, it is a further improvement of the above-mentioned embodiment. The welding load module 500 includes a load resistor R and a load current detection circuit 510. One end of the load current detection circuit 510 is connected to the load, and the other end is connected to the welding current control module 400. The load detection circuit includes a shunt and an ammeter, which can detect the changed current in real time to ensure the accuracy of the welding current obtained and avoid the welding current exceeding the preset current value and causing the welding machine 100 to burn out due to heat.

[0044] In addition, a voltmeter corresponding to the welding load is provided within the welding load module 500 for detecting the voltage waveform and magnitude at the welding point. By controlling the operating times of M1, M2, and M3, the voltage magnitude across the welding load is changed, and the change in the voltage magnitude is used to verify again whether the power at the welding load exceeds the preset power, thereby preventing the welding machine 100 from being damaged by excessive heat generated due to excessive power.

[0045] Reference Figure 9 As shown, as the fifth embodiment of the present application, a welding machine 100 is disclosed. The welding machine 100 includes the current control circuit 200 described in any of the above embodiments. The current control circuit 200 controls the welding current of the welding machine 100. The welding machine 100 further includes other software and hardware structures. However, the main improvement of the present application lies in the current control circuit 200 part, and other structures are not protected, so other structures will not be introduced one by one.

[0046] It should be noted that the inventive concept of the present application can form a very large number of embodiments. However, due to the limited space of the application documents, it is impossible to list them all. Therefore, on the premise of no conflict, the above-described embodiments or technical features can be combined arbitrarily to form new embodiments. After the combination of each embodiment or technical feature, the original technical effect will be enhanced.

[0047] The above content is a further detailed description of the present application in combination with specific optional implementation manners. It cannot be determined that the specific implementation of the present application is only limited to these descriptions. For those of ordinary skill in the technical field to which the present application pertains, without departing from the concept of the present application, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present application.

Claims

1. A current control circuit for a welding machine, characterized in that It includes a transformer, a welding current control module, and a welding load module. The transformer receives the voltage input from the power supply system and outputs it to the welding current control module. The welding current control module is respectively connected to the transformer and the welding load module to control the average current value of the welding load module. The transformer is a △ / Y type three-phase transformer, which includes a primary winding, a secondary winding, and a magnetic core disposed between the primary winding and the secondary winding. The secondary winding is connected to the power supply system. The primary winding includes a first end, a second end, and a third end. The welding current control module includes a first arm, a second arm, and a third arm. The first arm includes a first switching power tube and a first resistor. The second arm includes a second switching power tube and a second resistor. The third arm includes a third switching power tube and a third resistor. The first common connection point and the second common connection point of the first arm, the second arm, and the third arm are respectively connected to both ends of the welding load module. The midpoints of the first arm, the second arm, and the third arm are respectively connected to the first end, the second end, and the third end of the primary winding. The current control circuit includes a timing control and drive module, which is respectively connected to the control ends of the first switching power tube, the second switching power tube, and the third switching power tube to control the conduction or cutoff of the first switching power tube, the second switching power tube, and the third switching power tube. Among them, the phase difference between the current waveforms of the first switching power tube, the second switching power tube, and the third switching power tube is 120°.

2. The current control circuit of the electric welding machine according to claim 1, characterized in that, A first diode is arranged in parallel between the input end and the output end of the first resistor. A second diode is arranged in parallel between the input end and the output end of the second resistor. A third diode is arranged in parallel between the input end and the output end of the third resistor. The output end of the first diode is connected to the midpoint of the first arm. The output end of the second diode is connected to the midpoint of the second arm. The output end of the third diode is connected to the midpoint of the third arm. The input ends of the first diode, the second diode, and the third diode are respectively connected to the welding load module through the second common connection point.

3. The current control circuit of the electric welding machine according to claim 2, characterized in that, The current control circuit further includes a fourth diode. The input end of the fourth diode is connected to the second common connection point, and the output end of the fourth diode is connected to the primary winding.

4. The current control circuit of the electric welding machine according to any one of claims 1-3, characterized in that, The welding load module includes a load resistor. One end of the load resistor is connected to the first common connection point, and the other end is connected to the second common connection point.

5. The current control circuit of the electric welding machine according to any one of claims 1-3, characterized in that, The welding load module includes a load resistor and a load current detection circuit. One end of the load current detection circuit is connected to the load, and the other end is connected to the welding current control module.

6. The current control circuit of the electric welding machine according to claim 1, characterized in that, The first switching power tube, the second switching power tube, and the third switching power tube are gallium nitride devices of the same model and the same specification.

7. The current control circuit of the electric welding machine according to claim 1, characterized in that The timing control and drive module includes a PWM control circuit. The PWM control circuit generates a first drive signal and outputs it to the control terminal of the first switching power transistor. The PWM control circuit generates a first drive signal and outputs it to the control terminal of the first switching power transistor. The PWM control circuit generates a second drive signal and outputs it to the control terminal of the second switching power transistor. The PWM control circuit generates a third drive signal and outputs it to the control terminal of the third switching power transistor; Wherein, the falling edge of the first drive signal and the rising edge of the second drive signal are at the same moment, the falling edge of the second drive signal and the rising edge of the third drive signal are at the same moment, and the durations between the rising edge and the falling edge of the first drive signal, the second drive signal, and the third drive signal are the same.

8. A welding machine, characterized in that, It includes the current control circuit according to any one of claims 1-7, and the current control circuit controls the welding current of the electric welder.

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