Multi-voltage inverter welding machine control circuit power supply method and inverter welding machine

Abstract

The invention discloses a multi-voltage inverter welding machine control circuit power supply method and an inverter welding machine, relates to the technical field of welding, and designs a power supply circuit, a driving circuit, an inverter circuit and a power supply transformer which are connected in sequence. Rectifying and filtering, BUCK voltage reduction and BUCK-BOOST conversion are sequentially carried out on the low-voltage alternating current to generate stable positive and negative power supply voltage to supply power to the driving circuit; a driving circuit is utilized, a PWM control strategy based on phase shift driving is adopted to drive an inverter circuit to operate, and the inverter circuit converts stable direct current in a main loop of the multi-voltage inverter welding machine into stable alternating current according to the PWM control strategy; the converted stable alternating current is connected to the primary side of the power transformer, and the secondary side of the power transformer supplies power to a control circuit and auxiliary tools of the multi-voltage inverter welding machine. According to the invention, only one power supply circuit is additionally arranged, so that stable power supply for the multi-voltage inverter welding machine is realized.

Description

Technical Field

[0001] The invention belongs to the technical field of welding, and in particular relates to a power supply method for a control circuit of a multi-voltage inverter welding machine and an inverter welding machine. Background Art

[0002] The principle of the inverter welding machine is to rectify the industrial frequency AC power into DC power, and then convert it into high-frequency AC power through the inverter circuit, and then use it for welding after rectification. Due to the characteristics of high efficiency and low cost, the inverter welding machine has more and more application scenarios and application scope. Considering that the power supply voltage between regions is not uniform, the inverter welding machine needs to be designed separately for different power supply voltages. In order to avoid this diversified design, the inverter welding machine is usually designed to adapt to multiple voltage inputs at the same time. That is, a multi-voltage inverter welding machine is proposed, which allows the input of multiple levels of voltage, such as AC 220V-575V input. Through this design, the inverter welding machine can be applied to different power supply voltage occasions, which is convenient for promotion and use.

[0003] The circuit composition of the inverter welding machine is generally divided into a control circuit and a power circuit, wherein the control circuit can perform the function of feedback and regulating the power circuit, and the power circuit is used to output the current and voltage for welding. Normally, the inverter welding machine reduces the voltage through the power transformer and then supplies power to its control circuit. The primary and secondary voltages of the power transformer are proportional, and the proportionality coefficient is determined by the number of turns of the winding. The change of the primary voltage will cause the secondary voltage to change accordingly. Since the multi-voltage inverter welding machine can input AC power with a wide range of voltages, this leads to the power supply of the control circuit also being a wide range of voltages. The wide range of AC power needs to be stabilized before it can be used to power the control circuit, so as to ensure the stability of subsequent operation.

[0004] In the prior art, voltage stabilization technologies such as switching power supplies or magnetic saturation transformers are usually used, but these technologies all have certain problems:

[0005] (1) A switching power supply or other DC power supply that allows a wide range of input is used to stabilize the wide range of AC power. However, in the design of the switching power supply, on the one hand, the reliability of the switching power supply with high voltage input is low, and the high-voltage components used in the high-voltage switching power supply circuit have large losses, which makes it difficult to design a high-power high-voltage switching power supply. On the other hand, the design of a switching power supply that allows a wide range of input of more than 2 times is complex and costly, especially when the wide range of input high voltage is more than 2 times. In addition, many components in the inverter welding machine require AC power supply, such as the wire feeder, gas meter auxiliary heating, AC cooling fan, and various electric tools that may be used in welding. Using DC power supplies such as switching power supplies to supply power cannot meet actual application requirements.

[0006] (2) Considering that the magnetic saturation transformer is a kind of power transformer, it allows multiple voltage inputs. However, the allowable input voltage range of the magnetic saturation transformer is relatively narrow, and is generally designed to allow ±15% voltage fluctuations. Voltage fluctuations exceeding the ±15% range will cause design difficulties, and designs exceeding ±30% voltage fluctuations are basically difficult to achieve. Therefore, it is not practical to use a magnetic saturation transformer to solve the power supply problem of the control circuit. Moreover, the volume of a high-power magnetic saturation transformer is very large, and the structural design requirements of the inverter welding machine are relatively high. The magnetic saturation transformer also has many disadvantages, such as the output voltage will be distorted, which is not conducive to the design of the subsequent control circuit power supply, the loss itself is large, electromagnetic interference will be generated during operation, and the matching resonant capacitor is required to be used together, resulting in high cost.

[0007] (3) The output stability of the power transformer can also be achieved by switching the transformer taps. However, multiple switches and control circuits are required for multiple voltage inputs. Whether the switch is switched manually or the switch is automatically switched by a matching control circuit, there is a risk of switching errors or mis-switching. Moreover, the switch switching process is usually performed under power, which may cause arcing of the switch contacts, thereby affecting the reliability of the switch. Therefore, this method has the problem of low power supply reliability. Summary of the invention

[0008] In order to solve the deficiencies of the above-mentioned prior art, the present invention provides a multi-voltage inverter welding machine control circuit power supply method and an inverter welding machine. Aiming at the problem that the inverter welding machine control circuit power supply is difficult to design, the stable voltage converted by the multi-voltage inverter welding machine after different input voltages is considered, and the stable voltage is used to design a power supply method for the control circuit, that is, by designing an inverter circuit and a corresponding phase-shifting driving strategy, the stable voltage is converted into a stable alternating current. After conversion by a power transformer, the alternating current can provide alternating current power supply for the welding machine control circuit and other components, machine auxiliary tools, etc., thereby realizing a simpler design and smaller size wide-range alternating current voltage stabilization and alternating current power supply.

[0009] In a first aspect, the present invention provides a method for powering a control circuit of a multi-voltage inverter welding machine.

[0010] A method for powering a control circuit of a multi-voltage inverter welding machine is provided, which designs a power supply circuit, a drive circuit, an inverter circuit and a power transformer connected in sequence, and comprises:

[0011] The power circuit is used to reduce the high voltage AC power to low voltage AC power, and the low voltage AC power is rectified and filtered, bucked and buck-boosted in sequence to generate stable positive and negative power supply voltages to power the drive circuit.

[0012] The inverter circuit is driven by a driving circuit and a PWM control strategy based on phase shift driving. The inverter circuit converts the stable direct current in the main circuit of the multi-voltage inverter welding machine into a stable alternating current according to the PWM control strategy.

[0013] The converted stable AC power is connected to the primary side of the power transformer, and the secondary side of the power transformer supplies power to the control circuit and auxiliary equipment of the multi-voltage inverter welding machine.

[0014] In a second aspect, the present invention further provides an inverter welding machine, which uses the multi-voltage inverter welding machine control circuit power supply method described in the first aspect to power a control circuit.

[0015] One or more of the above technical solutions have the following beneficial effects:

[0016] 1. The present invention provides a power supply method for a multi-voltage inverter welding machine control circuit and an inverter welding machine. Aiming at the problem that the inverter welding machine control circuit power supply is difficult to design, considering that in an inverter welding machine with multi-voltage power supply, in order to obtain the best welding performance, a boost or buck method (or a buck-boost method) is usually adopted to convert different input voltages into a stable voltage. For this reason, the present invention uses the stable voltage to design a power supply method for the control circuit. By designing an inverter circuit and the corresponding phase-shift driving strategy, the stable voltage is converted into a stable alternating current. After the alternating current is converted by a power transformer, it can provide alternating current power supply for the welding machine control circuit and other components, machine auxiliary tools, etc., thereby realizing a simpler design and smaller volume wide-range alternating current voltage stabilization and alternating current power supply, avoiding the disadvantages of using a high-voltage wide-range switching power supply, a magnetic saturation transformer or a switching transformer tap power supply method in a multi-voltage welding machine, effectively improving the power supply reliability and stability, reducing interference, and thus achieving the best welding performance.

[0017] 2. The present invention designs a power supply circuit and a power transformer combination for power supply. The power supply circuit converts the stable voltage based on different input voltage conversion into alternating current (such as alternating current square wave or sine wave, etc.). After the alternating current is converted by the power transformer, it provides alternating current power supply for the welding machine control circuit and other components, machine auxiliary tools, etc., solving the problem that the related circuits and components require alternating current power supply. The present invention can meet the power supply application of multi-voltage welding machines, and the output is alternating current, which can meet the application of other tools that require alternating current power supply. Compared with a single-voltage power supply welding machine, only one power supply circuit is added, the design is simple, the size is small, and it is easy to promote and use.

[0018] 3. In the present invention, a power supply scheme is formed by combining a power supply circuit design and a power transformer. By adjusting the number of turns of the power transformer, the power transformer can be designed to have the same voltage as the transformer output of a single-voltage power supply welding machine. In this way, the control circuits used in the multi-voltage welding machine and the components and auxiliary tools that require AC power supply can directly use the design scheme of the single-voltage welding machine, and no additional multi-voltage welding machine design is required, which can further simplify the design scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0020] Figure 1 A schematic diagram of a connection framework of a power supply circuit provided in a power supply method for a multi-voltage inverter welding machine control circuit according to an embodiment of the present invention;

[0021] Figure 2 A connection framework diagram of a power supply circuit in an embodiment of the present invention;

[0022] Figure 3 is a circuit diagram of a power supply circuit in an embodiment of the present invention;

[0023] Figure 4 is a circuit diagram of an inverter circuit and a driving circuit thereof in an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the distortion of the output square wave AC when using the traditional full-bridge drive;

[0025] Figure 6 A schematic diagram of a driving waveform generated by a phase-shift driving strategy in an embodiment of the present invention;

[0026] Figure 7 A schematic diagram of a circuit for generating a driving signal in an embodiment of the present invention;

[0027] Figure 8 A schematic diagram of another circuit for generating a driving signal in an embodiment of the present invention;

[0028] Fig. 9 The main circuit schematic diagram of the multi-voltage inverter welding machine in the embodiment of the present invention. DETAILED DESCRIPTION

[0029] It should be noted that the following detailed descriptions are exemplary only, are intended to describe specific embodiments, are intended to provide further explanation of the present invention, and are not intended to limit exemplary embodiments according to the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those of ordinary skill in the art to which the present invention belongs. In addition, it should also be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0030] Aiming at the problem that the power supply of the inverter welding machine control circuit is difficult to design, considering that in the inverter welding machine with multi-voltage power supply, in order to obtain the best welding performance, a step-up or step-down method (or step-up and step-down method) is usually adopted to convert different input AC voltages into stable DC voltages. On this basis, the present invention proposes a power supply method for the control circuit of a multi-voltage inverter welding machine. By designing a corresponding circuit (including a power supply circuit, a drive circuit, an inverter circuit and a power transformer), the inverter circuit in the circuit is used to invert the stabilized DC voltage in the main circuit of the inverter welding machine back to AC. The frequency of the AC is the industrial frequency, generally 50Hz or 60Hz, which is different from the high inverter frequency (tens of kHz) of the inverter welding machine. Since the DC input by the inverter circuit is a stable voltage, the AC after inversion is also a stable voltage, thereby realizing voltage stabilization processing of a wide range of AC.

[0031] Embodiment 1

[0032] This embodiment provides a method for powering a control circuit of a multi-voltage inverter welding machine, which designs a power supply circuit, a drive circuit, an inverter circuit and a power transformer connected in sequence, such as Figure 1 As shown, including:

[0033] The power circuit is used to reduce the high voltage AC power to low voltage AC power, and the low voltage AC power is rectified and filtered, bucked and buck-boosted in sequence to generate stable positive and negative power supply voltages to power the drive circuit.

[0034] The inverter circuit is driven by a driving circuit and a PWM control strategy based on phase shift driving. The inverter circuit converts the stable direct current in the main circuit of the multi-voltage inverter welding machine into a stable alternating current according to the PWM control strategy.

[0035] The converted stable AC power is connected to the primary side of the power transformer, and the secondary side of the power transformer supplies power to the control circuit and auxiliary equipment of the multi-voltage inverter welding machine.

[0036] First, for the above-mentioned power supply circuit, the power supply circuit is used to reduce the input high-voltage AC power to low-voltage AC power, and the low-voltage AC power is converted into DC power after rectification and filtering. The DC power is converted into stable positive and negative power supply voltages after BUCK step-down and BUCK-BOOST conversion to supply power to the drive circuit of the inverter circuit. In this embodiment, the power supply circuit includes a step-down circuit, a rectifier circuit, a BUCK step-down circuit, a PWM control circuit, a BUCK-BOOST conversion circuit, a pulse generating circuit, a positive power supply linear voltage regulator circuit, and a negative power supply linear voltage regulator circuit, and its working principle is as follows:

[0037] (1) The input high-voltage AC power is stepped down to low-voltage AC power by a transformer. The use of low-voltage AC power can better ensure the reliability of the power circuit and make the circuit design simpler;

[0038] (2) Low voltage AC is converted into smooth DC after rectification and filtering;

[0039] (3) The DC power is stepped down to a positive power supply voltage by a BUCK step-down circuit;

[0040] (4) The positive power supply voltage undergoes polarity inversion and voltage conversion after passing through the BUCK-BOOST conversion circuit to generate a negative power supply voltage. Preferably, in order to make the positive and negative power supplies more stable, a positive and negative power supply linear voltage stabilization circuit is added to the output circuit.

[0041] In this embodiment, the specific circuit structure of the power supply circuit is as follows: Figure 3 As shown, the positive power supply is generated by PWM control, the BUCK step-down circuit includes a switch tube KF4, the PWM control circuit includes a current-type PWM controller K3 (3842), and the pulse output pin (i.e., OUTP pin) of the PWM controller K3 is connected to the switch tube KF4, and the switch tube KF4 is turned on and off by the generated pulse, so as to perform voltage conversion. Further, the voltage conversion principle is: a smooth direct current is input to the input end of the switch tube KF4, and since KF4 is in a switching state, the output end of KF4 is a pulsed direct current, and the effective value of the output end is smaller than that of the input end, and the effective value of the output end can be calculated by multiplying the input end voltage by the KF4 conduction duty cycle.

[0042] The positive power linear voltage regulator circuit comprises a linear voltage regulator K4. The output of the BUCK step-down circuit is input to the linear voltage regulator K4 for voltage regulation to generate a positive power voltage.

[0043] Furthermore, the source of the switch tube KF4 is connected to the current detection resistor R22, and the current signal detected by the current detection resistor R22 is input to the ISE pin of the PWM controller K3. The ISE pin of the PWM controller K3 is connected to the current slope compensation circuit composed of the resistor R23 and the diode KF3, so that the feedback current in the full range can be detected. The feedback current here is the current flowing through the switch tube KF4. The current has two functions. First, the diode K3 is a current-type PWM controller, and the current needs to be introduced as the input of the PWM control comparator to make the PWM control more stable; second, the switch tube KF4 and other components in the loop can be protected from overcurrent by detecting the current. When the current exceeds the limit of the component, the protection measure is activated.

[0044] Furthermore, the voltage regulator K7, the optocoupler KF6 and their peripheral circuits constitute a voltage feedback circuit. In the present embodiment, K7 is a voltage regulator, and the voltage of its REF pin is stabilized at 2.5V; the voltage feedback circuit is connected to the COMP pin of the PWM controller K3. When the voltage of the REF pin of the voltage regulator K7 fluctuates, the current flowing through K7 changes, thereby changing the current in the light-emitting diode in the optocoupler KF6, and changing the current in the transistor in KF6 after transmission through the optocoupler, thereby changing the voltage at the COMP pin of the voltage comparator of the PWM controller K3, thereby performing PWM regulation.

[0045] In the above design, the COMP pin of K3 is used in the voltage feedback circuit, and the internal voltage error amplifier is skipped, so that the feedback is more timely. Specifically, there is a comparator unit inside the PWM controller K3, and the comparator has 2 inputs and 1 output, one of which is the VFB pin, and the other is the internal reference voltage source. The output of the comparator unit is connected to the COMP pin. Usually, the voltage feedback signal is processed and connected to the VFB pin, so that the voltage feedback signal (i.e. +VCC) is compared with the voltage reference source inside K3, and the comparator outputs different voltages, thereby affecting the output state of the OUTP pin, and then adjusting the on and off time of the KF4 switch tube. Considering that in this case, the voltage feedback needs to pass through the voltage comparator inside the device before it can affect the output, and there is a certain delay. Therefore, in this embodiment, the voltage feedback signal is directly processed and connected to the COMP pin (i.e. the output end of the voltage comparator inside K3), which is equivalent to not using the voltage comparator, so that the delay can be reduced.

[0046] Furthermore, the switch tube of the BUCK buck circuit is driven by a floating ground and requires a separate power supply. In this embodiment, a capacitor bootstrap circuit is designed as an isolated drive circuit. Since the drive reference GND of the switch tube KF4 in the BUCK buck circuit is not the same as the reference GND of the control circuit (i.e., the PWM controller K3 part of the circuit), when the drive circuit is not isolated, the reference grounds of the two parts of the circuit are different, which will cause heating and other problems. The reliability of the circuit is guaranteed by designing an isolated drive circuit. Among them, the drain of the switch tube KF4 is connected to the capacitor bootstrap circuit, which includes a diode RB3, a voltage regulator RC5, a bootstrap capacitor CE5 and a capacitor C13, wherein the key components are RB3 and CE5, and the reverse voltage of the diode RB3 is greater than the DC voltage of the switch tube KF4 when it is turned on and off, which is used to prevent the high voltage when the switch tube KF4 is turned on from back into the +V terminal, causing the voltage fluctuation of the +V terminal, and at the same time RB3 needs to have sufficient flow rate to drive the PWM controller and the switch tube by flowing enough current. In this embodiment, a fast recovery diode with a small leakage current is selected; the bootstrap capacitor CE5 is used to provide a charge not less than the gate charge of the switch tube KF4 required for conduction, and maintain its voltage during the conduction of the switch tube. The above design can realize isolated drive, and no additional isolated power supply is used, which is lower in cost.

[0047] Since the input and output voltages of the negative power supply circuit are stable and the adjustment range is very small, the negative power supply BUCK-BOOST circuit uses a switch tube KF5 driven by a fixed pulse width when designing. The pulse generating circuit includes a multivibrator composed of a 555 timer K6 and its peripheral circuits. The multivibrator generates a pulse signal with a fixed pulse width and inputs the pulse signal to the switch tube KF5. The switch tube KF5 is turned on and off according to the pulse signal to perform polarity reversal and voltage conversion. The output of the switch tube KF5 is input to the linear regulator K5 after voltage stabilization to generate a more stable negative power supply voltage.

[0048] Secondly, if Figure 4 The inverter circuit and its driving circuit shown in the figure adopt a full-bridge inverter circuit. The output of the full-bridge inverter circuit is connected to the power transformer. Due to the leakage inductance of the primary winding of the power transformer and the parasitic parameters of the switch tube, when the traditional full-bridge drive is adopted, there will be LC resonance after the IGBT is turned off, causing the output square wave AC to be distorted, such as Figure 5 To this end, this embodiment proposes a phase-shift driving strategy, and the driving waveform generated by this strategy is as follows Figure 6 As shown, specifically, the full-bridge inverter includes four switch tubes Q1 to Q4, the switch tubes Q1 and Q2 form a leading bridge arm, and the switch tubes Q3 and Q4 form a lagging bridge arm; the drive circuit includes a circuit for generating a drive signal, and the drive signal is generated based on a phase-shift drive strategy, and the phase-shift drive strategy is:

[0049] The leading bridge arm opens in advance and shuts down in advance; the lagging bridge arm opens with a delay and shuts down with a delay;

[0050] When the upper bridge arm is turned off, the diagonal switch tube is not turned off, and the lower bridge arm is turned on after the set small dead time, so that the parasitic capacitance of the upper and lower bridge arms and the primary leakage inductance of the power transformer do not resonate during the dead time. Furthermore, the principle of no longer resonating is: when LC resonates, it will produce an oscillation similar to a sine wave, and the oscillation period can be simply described as T=2πLC. When the designed dead time is much smaller than T, that is, the oscillation enters another working state of the circuit at the beginning, and the oscillation will no longer continue. Among them, the small dead time is set to <500uS, which can effectively avoid resonance.

[0051] In this embodiment, the driving signal generated by the phase-shift driving strategy is as follows: Figure 6 As shown, the driving circuit used to generate the phase-shift driving strategy is as follows Figure 7 As shown, UCC3895 is a dedicated phase-shift PWM controller, and its working process is: compare the given voltage signal with its internal reference source, output a pulse voltage with adjustable pulse width, and output it through four OUT pins to drive the four switching tubes in the full-bridge inverter. In addition, the frequency of the pulse voltage can be adjusted by the clock oscillation circuit.

[0052] As another embodiment, the following Figure 8 The microprocessor (MCU), DSP, etc. shown generate a phase-shift driving strategy.

[0053] Through the above design, the full-bridge inverter circuit is driven by the driving signal to output square wave alternating current, wherein the effective value of the square wave alternating current can be adjusted by adjusting the duty cycle.

[0054] Based on the above design, the main circuit schematic diagram of the multi-voltage inverter welding machine proposed in this embodiment is as follows: Fig. 9 As shown, the voltage stabilizing circuit can be a BOOST circuit, a BUCK circuit, or a BUCK-BOOST circuit. As long as it is an inverter welding machine that can generate stable direct current when multiple voltage inputs are used, the circuit described above can be used to achieve stable power supply.

[0055] Embodiment 2

[0056] This embodiment also provides an inverter welding machine, which is powered by the power supply method applicable to multi-voltage inverter welding machines proposed in the first embodiment.

[0057] The steps involved in the above embodiment 2 correspond to those in the method embodiment 1. For the specific implementation method, please refer to the relevant description part of the embodiment 1, which will not be described in detail here.

[0058] Those skilled in the art should understand that the modules or steps of the present invention described above can be implemented by a general-purpose computer device, or alternatively, they can be implemented by a program code executable by a computing device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. The present invention is not limited to any specific combination of hardware and software.

[0059] The above description is only a preferred embodiment of the present invention. Although the specific implementation mode of the present invention is described in conjunction with the accompanying drawings, it is not a limitation of the protection scope of the present invention. Those skilled in the art should understand that on the basis of the technical solution of the present invention, various modifications or variations that can be made by those skilled in the art without creative work are still within the protection scope of the present invention.

Claims

1. A method for powering a control circuit of a multi-voltage inverter welding machine, characterized in that: Design the power supply circuit, drive circuit, inverter circuit and power transformer connected in sequence, including: The power circuit is used to reduce the high voltage AC power to low voltage AC power, and the low voltage AC power is rectified and filtered, bucked and buck-boosted in sequence to generate stable positive and negative power supply voltages to power the drive circuit. The drive circuit is used to drive the operation of the inverter circuit by adopting a PWM control strategy based on phase shift drive. The inverter circuit converts the stable direct current in the main circuit of the multi-voltage inverter welding machine into stable alternating current according to the PWM control strategy. The converted stable AC power is connected to the primary side of the power transformer, and the secondary side of the power transformer supplies power to the control circuit and auxiliary equipment of the multi-voltage inverter welding machine.

2. A method for powering a multi-voltage inverter welding machine control circuit as claimed in claim 1, characterized in that: The power supply circuit includes a step-down circuit, a rectifier circuit, a BUCK step-down circuit, a PWM control circuit, a BUCK-BOOST conversion circuit, a pulse generation circuit, a positive power supply linear voltage stabilization circuit and a negative power supply linear voltage stabilization circuit; The high voltage AC is input into the power supply circuit, stepped down into low voltage AC by the step-down circuit, and then converted into DC after rectification and filtering; The DC power is stepped down to a positive power supply voltage through a BUCK step-down circuit controlled by a PWM control circuit; The positive power supply voltage is reversed in polarity and converted in voltage by the BUCK-BOOST conversion circuit to generate a negative power supply voltage.

3. A method for powering a multi-voltage inverter welding machine control circuit as claimed in claim 2, characterized in that: The BUCK step-down circuit includes a switch tube KF4, and the PWM control circuit includes a PWM controller K3. The pulse output pin of the PWM controller K3 is connected to the switch tube KF4, and the on and off time of the switch tube KF4 is controlled by the generated pulse, so as to perform voltage conversion; The positive power supply linear voltage regulator circuit includes a linear voltage regulator K4, and the output of the BUCK step-down circuit is input to the linear voltage regulator K4 for voltage stabilization to generate a positive power supply voltage.

4. A method for powering a multi-voltage inverter welding machine control circuit as claimed in claim 2, characterized in that: The BUCK-BOOST conversion circuit includes a switch tube KF5 driven by a fixed pulse width, and the pulse generating circuit includes a multivibrator composed of a 555 timer K6 and its peripheral circuits. The multivibrator generates a pulse signal with a fixed pulse width, and inputs the generated pulse signal to the switch tube KF5, and controls the on and off time of the switch tube KF5 according to the pulse signal, thereby performing polarity reversal and voltage conversion; The negative power supply linear voltage regulator circuit includes a linear voltage regulator K5, and the output of the BUCK-BOOST conversion circuit is input to the linear voltage regulator K5 for voltage stabilization to generate a negative power supply voltage.

5. A method for powering a control circuit of a multi-voltage inverter welding machine as claimed in claim 2, characterized in that: The COMP pin of the PWM controller K3 is connected to a voltage feedback circuit, which includes a voltage regulator K7, an optocoupler KF6 and its peripheral circuits; when the voltage of the REF pin of the voltage regulator K7 fluctuates, the current in the light-emitting diode in the optocoupler KF6 changes, and after transmission through the optocoupler, the current of the transistor in KF6 changes, causing the voltage at the COMP pin of the voltage comparator of the PWM controller K3 to change, thereby performing PWM regulation.

6. A method for powering a control circuit of a multi-voltage inverter welding machine as claimed in claim 3, characterized in that: The drain of the switch tube KF4 is connected to a capacitor bootstrap circuit, which includes a diode RB3, a voltage regulator RC5, a bootstrap capacitor CE5 and a capacitor C13, wherein the reverse voltage of the diode RB3 is greater than the DC voltage of the switch tube KF4 when it is turned on and off, and the bootstrap capacitor CE5 is used to provide a charge that is not less than the gate charge of the switch tube KF4 required for conduction.

7. A method for powering a control circuit of a multi-voltage inverter welding machine as claimed in claim 1, characterized in that: The inverter circuit adopts a full-bridge inverter circuit; wherein the full-bridge inverter includes four switch tubes Q1 to Q4, the switch tubes Q1 and Q2 form a leading bridge arm, and the switch tubes Q3 and Q4 form a lagging bridge arm; the PWM control strategy based on phase-shift drive is: The leading bridge arm opens in advance and shuts down in advance; the lagging bridge arm opens with a delay and shuts down with a delay; When the upper bridge arm is turned off, the diagonal switch tube is not turned off, and the lower bridge arm is turned on after a set small dead time.

8. A method for powering a control circuit of a multi-voltage inverter welding machine as claimed in claim 7, characterized in that: The small dead time is set to be less than 500uS.

9. A method for powering a control circuit of a multi-voltage inverter welding machine as claimed in claim 7, characterized in that: The full-bridge inverter circuit converts the stable direct current in the main circuit of the multi-voltage inverter welding machine into stable alternating current under the PWM control strategy based on phase-shift drive, and outputs distortion-free square wave alternating current; wherein the effective value of the square wave alternating current is adjusted by adjusting the duty cycle.

10. An inverter welding machine, characterized in that: The power supply is performed by adopting the multi-voltage inverter welding machine control circuit power supply method as described in any one of claims 1 to 9.

Images