Voltage isolation sampling method and circuit

Abstract

The application relates to the field of circuit control technology, in particular to a voltage isolation sampling method and circuit, which comprises the following steps: acquiring a voltage input signal; performing error amplification processing on the voltage input signal to output a characteristic voltage signal; and controlling an arc voltage output by a welding machine according to the characteristic voltage signal, wherein the characteristic voltage signal is in proportional relationship with the arc voltage. The application has the effect of realizing voltage isolation sampling with low cost and simple circuit.

Description

Technical Field

[0001] This application relates to the field of circuit control technology, and in particular to a voltage isolation sampling method and circuit. Background Technology

[0002] In the application of electric welding machines, there are many welding process parameters. Among them, arc voltage is a key parameter in welding specifications. It refers to the voltage between the welding torch tip and the workpiece, and it has the greatest impact on the stable combustion of the arc. The magnitude of the arc voltage depends on the arc length and the transition form of the molten droplets, and it has a significant impact on the stability of the welding process, weld formation, spatter, welding defects, and the mechanical properties of the weld. Therefore, in order to achieve corresponding control of the welding process, it is necessary to sample the arc voltage in real time.

[0003] Currently, most methods use linear optocoupler isolation feedback to sample the arc voltage of welding machines. For example, the voltage signal from the welding machine's output is processed by an operational amplifier circuit and then sent to a linear optocoupler. After isolation by the optocoupler, it is buffered by another operational amplifier circuit before outputting the sampled voltage value. The linear optocoupler has a feedback function. While this approach achieves good isolation sampling, it uses a linear optocoupler with feedback, which is expensive, leading to a higher overall cost for the sampling circuit. Summary of the Invention

[0004] To reduce the cost of arc voltage sampling circuits in welding machines, this application provides a voltage isolation sampling method and circuit.

[0005] Firstly, this application provides a voltage isolation sampling method, which adopts the following technical solution:

[0006] A voltage isolation sampling method, comprising:

[0007] Obtain the voltage input signal;

[0008] The voltage input signal is subjected to error amplification processing to output a characteristic voltage signal;

[0009] The arc voltage output by the welding machine is controlled according to the characteristic voltage signal, wherein the characteristic voltage signal is proportional to the arc voltage.

[0010] By adopting the above technical solution, based on the proportional relationship between the characteristic voltage signal and the arc voltage, the arc voltage output by the welding machine can be isolated and sampled by acquiring the value of the characteristic voltage signal, and the arc voltage can be controlled. Moreover, without using a linear optocoupler for voltage sampling, the circuit cost can be reduced.

[0011] Optionally, before performing error amplification processing on the voltage input signal, the method further includes:

[0012] The voltage input signal is buffered, and a buffered voltage signal is output.

[0013] The buffered voltage signal is amplified in reverse to output a current command signal;

[0014] The step of performing error amplification processing on the voltage input signal to output a characteristic voltage signal specifically involves:

[0015] The current reference signal is subjected to error amplification processing to output the characteristic voltage signal.

[0016] By adopting the above technical solution, the voltage input signal is buffered and inversely amplified before error amplification, thereby outputting a characteristic voltage signal. To a certain extent, the characteristic voltage signal can be made closer to the expected theoretical value of the arc voltage output by the welding machine.

[0017] Optionally, after performing error amplification processing on the voltage input signal and outputting the characteristic voltage signal, the method further includes:

[0018] The characteristic voltage signal is subjected to amplitude scaling conversion, and a voltage feedback signal is output.

[0019] The voltage feedback signal and the buffered voltage signal are superimposed to output a superimposed voltage signal.

[0020] The process of inverting and amplifying the buffered voltage signal to output a current command signal specifically involves:

[0021] The superimposed voltage signal is amplified in reverse to output the current command signal.

[0022] By adopting the above technical solution, the characteristic voltage signal is processed by operation and amplification to output a voltage feedback signal, which is then superimposed on the buffer voltage signal and then amplified in reverse to output a current command signal, forming a negative feedback system. The voltage feedback signal continuously corrects the output current command signal, which can improve the control accuracy of the arc voltage output by the welding machine.

[0023] Optional, also includes:

[0024] The output current of the welding machine is detected and a current feedback signal is output.

[0025] The current feedback signal and the current set signal are processed to obtain the current error signal;

[0026] The step of performing error amplification processing on the voltage input signal to output a characteristic voltage signal specifically involves:

[0027] The current error signal is amplified to output the characteristic voltage signal.

[0028] By adopting the above technical solution, the output current of the welding machine is detected in real time, and the output current feedback signal and the current given signal are processed by error amplification to obtain the characteristic voltage signal, which in turn controls the output of the welding machine, forming a negative feedback system. The current feedback signal continuously corrects the output characteristic voltage signal, which can improve the control accuracy of the welding machine's output arc voltage.

[0029] Optionally, controlling the arc voltage output by the welding machine based on the characteristic voltage signal specifically involves:

[0030] The characteristic voltage signal is converted into a square wave signal, and the frequency of the power supply is adjusted by the square wave signal, thereby controlling the arc voltage output by the welding machine.

[0031] By adopting the above technical solution, the characteristic voltage signal is converted into a square wave signal. The frequency of the welding machine power supply circuit is adjusted by the square wave signal, thereby changing the frequency of the output arc voltage and thus changing the output arc voltage value. By adjusting the input power frequency using a square wave, the output arc voltage can be indirectly changed, thus achieving isolation between the control circuit and the power supply circuit.

[0032] Secondly, this application provides a voltage isolation sampling circuit, which adopts the following technical solution:

[0033] A voltage isolation sampling circuit includes a voltage generation circuit for acquiring a voltage input signal, a sampling circuit for amplifying the voltage input signal and outputting a characteristic voltage signal, and a welding machine output control circuit for controlling the arc voltage output by a welding machine through the characteristic voltage signal, wherein the characteristic voltage signal is proportional to the arc voltage.

[0034] By adopting the above technical solution, the voltage generation circuit provides a voltage input signal to the sampling circuit, enabling the sampling circuit to output a characteristic voltage. The welding machine output control circuit controls the output of the welding machine based on the characteristic voltage. By acquiring the characteristic voltage, isolated sampling of the welding machine output arc voltage is achieved, and the cost is reduced by not using a linear optocoupler.

[0035] Optionally, a given signal generation circuit is provided between the voltage generation circuit and the sampling circuit. The given signal generation circuit includes a buffer unit for buffering the voltage input signal and outputting a buffered voltage signal, and an inverse amplification unit for inverse amplifying the buffered voltage signal and outputting a current given signal. The sampling circuit performs error amplification processing on the current given signal output by the inverse amplification unit and outputs the characteristic voltage signal.

[0036] By adopting the above technical solution, the voltage input signal is buffered and inversely amplified before error amplification, thereby outputting a characteristic voltage signal, which improves the accuracy of the characteristic voltage to a certain extent.

[0037] Optionally, the output of the sampling circuit is connected to a welding external characteristic control circuit, which is connected to a given signal generation circuit. The welding external characteristic control circuit performs amplitude proportional conversion on the characteristic voltage signal and outputs a voltage feedback signal. Then, the voltage feedback signal is superimposed with the buffer voltage signal output by the buffer unit to output a superimposed voltage signal. The superimposed voltage signal is then amplified by the inverting amplification unit and output as the current given signal.

[0038] By adopting the above technical solution, the welding external characteristic control circuit performs operational amplification processing on the characteristic voltage and outputs a voltage feedback signal. The voltage feedback signal is then fed back to the sampling circuit and superimposed on the buffered voltage input signal, jointly influencing the value of the current command signal. The feedback of the voltage feedback signal constitutes a negative feedback circuit, which continuously corrects the output current command signal, thereby improving the control accuracy of the welding machine output.

[0039] Optionally, the welding machine output control circuit includes a current sensor, which detects the output current of the welding machine and outputs the current feedback signal. After the current feedback signal and the current given signal are processed, the characteristic voltage signal is output after error amplification processing by the sampling circuit.

[0040] By adopting the above technical solution, the current sensor in the welding machine output control circuit provides a current feedback signal to the given signal generation circuit, forming a negative feedback control circuit. The current feedback signal continuously corrects the characteristic voltage signal of the output, making the control of the welding machine output more precise.

[0041] Optionally, the welding machine output control circuit includes a control circuit and a welding machine power supply circuit. The control circuit includes a PWM chip and an IGBT drive circuit. The PWM chip converts the characteristic voltage signal into a square wave signal. The square wave signal drives the IGBT drive circuit. The IGBT drive circuit adjusts the frequency of the welding machine power supply circuit, thereby controlling the welding machine power supply circuit to output the arc voltage of the welding machine.

[0042] By adopting the above technical solution, the PWM chip outputs a square wave signal based on the characteristic voltage signal, thereby controlling the welding output arc voltage. The PWM chip realizes the electrical isolation between the welding machine control circuit and the welding power supply circuit, and realizes isolated sampling of the welding machine output arc voltage.

[0043] In summary, this application includes at least one of the following beneficial technical effects:

[0044] 1. Based on the proportional relationship between the characteristic voltage signal and the arc voltage, the arc voltage output by the welding machine can be isolated and sampled by acquiring the value of the characteristic voltage signal, and the arc voltage can be controlled. Furthermore, the voltage sampling is not performed using a linear optocoupler, which can reduce circuit costs.

[0045] 2. The characteristic voltage signal is processed by operational amplification to output a voltage feedback signal, which is then superimposed on the buffer voltage signal and then amplified in reverse to output a current command signal, forming a negative feedback system. The voltage feedback signal continuously corrects the output current command signal, which can improve the control accuracy of the arc voltage output by the welding machine.

[0046] 3. The PWM chip outputs a square wave signal based on the characteristic voltage signal, thereby controlling the welding output arc voltage. The characteristic voltage is the sampled voltage value. The PWM chip realizes the electrical isolation between the welding machine control circuit and the welding circuit, and realizes isolated sampling of the welding machine output arc voltage. Attached Figure Description

[0047] Figure 1 This is a flowchart of a voltage isolation sampling method provided in an embodiment of this application.

[0048] Figure 2 This is a block diagram of a voltage isolation sampling circuit provided in an embodiment of this application.

[0049] Figure 3 This is a schematic diagram of the potentiometer circuit in an embodiment of this application.

[0050] Figure 4 This is a schematic diagram of a sampling circuit provided in an embodiment of this application.

[0051] Figure 5 This is a schematic diagram of the welding machine output control circuit in an embodiment of this application.

[0052] Figure 6 This is a schematic diagram of another sampling circuit provided in an embodiment of this application.

[0053] Figure 7 This is a block diagram of another voltage isolation sampling circuit provided in an embodiment of this application.

[0054] Figure 8 This is a schematic diagram of the signal generation circuit given in the embodiments of this application.

[0055] Figure 9 This is a schematic diagram of the welding external characteristic control circuit in the embodiments of this application.

[0056] Figure 10This is a curve showing the relationship between the current and voltage output by the welding machine in the embodiments of this application.

[0057] Explanation of reference numerals in the attached diagram: 1. Sampling circuit; 2. Voltage generation circuit; 21. Potentiometer circuit; 3. Welding machine output control circuit; 31. Control circuit; 311. IGBT drive circuit; 32. Welding machine power supply circuit; 33. Current sensor; 4. Given signal generation circuit; 41. Buffer unit; 42. Inverting amplification unit; 5. Welding external characteristic control circuit. Detailed Implementation

[0058] The following is in conjunction with the appendix Figure 1-10 This application will be described in further detail.

[0059] This application discloses a voltage isolation sampling method. (Refer to...) Figure 1 A voltage isolation sampling method mainly includes the following steps:

[0060] Step S100: Obtain the voltage input signal;

[0061] Specifically, the voltage input signal is provided by a voltage generation circuit, which can be composed of a potentiometer or a microcontroller. The output voltage value of the voltage generation circuit can be changed as needed. For example, when a potentiometer is used to output the voltage input signal, the brushes are moved along the resistive element to obtain a voltage that is related to the displacement. When a microcontroller is used to provide the voltage input signal, the output of the voltage input signal can be controlled by outputting high and low levels.

[0062] Step S200: Perform error amplification processing on the voltage input signal and output a characteristic voltage signal;

[0063] Specifically, the voltage input signal can be amplified by an error amplifier, which outputs a characteristic voltage signal. Using an error amplifier to process the voltage input signal reduces adjustment errors and produces a more accurate characteristic voltage signal.

[0064] Step S300: Control the output arc voltage of the welding machine according to the characteristic voltage signal, wherein the characteristic voltage signal is proportional to the arc voltage;

[0065] Specifically, the welding machine is controlled by PWM control. The PWM chip converts the characteristic voltage signal into a square wave signal, and adjusts the frequency of the welding machine's power supply circuit through the square wave signal, thereby controlling the output arc voltage of the welding machine.

[0066] The output voltage of the welding machine is proportional to the width of the drive pulse, while the characteristic voltage signal is proportional to the pulse width of the PWM control. Therefore, the output of the welding machine can be controlled by the characteristic voltage.

[0067] Furthermore, before step S200, the following steps are included: buffering the voltage input signal and outputting a buffered voltage signal; and inverting the buffered voltage signal to output a current command signal. Specifically, a voltage follower can be used to buffer the voltage input signal and output a buffered voltage signal.

[0068] Accordingly, step S200 is specifically executed as follows: the current given signal is subjected to error amplification processing, and a characteristic voltage signal is output.

[0069] Furthermore, after step S200, the following steps are also included: performing amplitude scaling on the characteristic voltage signal to output a voltage feedback signal; superimposing the voltage feedback signal and the buffered voltage signal to output a superimposed voltage signal.

[0070] Correspondingly, the buffered voltage signal is amplified in reverse to output the current command signal. Specifically, the superimposed voltage signal is amplified in reverse to output the current command signal.

[0071] Specifically, both the buffer voltage signal and the voltage feedback signal are used as inputs to the amplifier. The two signals are superimposed and amplified in reverse to output a negative current command signal. The voltage feedback signal serves as a negative feedback signal to correct the output current command signal.

[0072] Furthermore, the method also includes: detecting the output current of the welding machine and outputting a current feedback signal; performing calculations on the current feedback signal and the current given signal to obtain a current error signal;

[0073] Accordingly, step S200 is specifically executed as follows: the current error signal is amplified and the characteristic voltage signal is output.

[0074] Specifically, the welding machine power supply circuit is equipped with a current sensor, which is used to detect the current output by the welding machine and output a current feedback signal. The current feedback signal is fed back to the input of the error amplifier, and is processed with the current setpoint signal to correct the characteristic voltage signal and improve the control accuracy of the welding machine output arc voltage.

[0075] The current input signal and the current feedback signal are processed, and the result of the two signals is used as the input of the error amplifier. After the error amplifier performs error amplification, the characteristic voltage is output. The current feedback signal is used as a negative feedback signal to correct the output characteristic voltage, thereby improving the control accuracy of the arc voltage output by the welding machine.

[0076] This application also discloses a voltage isolation sampling circuit. (Refer to...) Figure 2 A voltage isolation sampling circuit includes a voltage generation circuit 2, a sampling circuit 1, and a welding machine output control circuit 3.

[0077] The voltage generation circuit 2 is connected to the input terminal of the sampling circuit 1 to provide a voltage input signal to the sampling circuit 1. The sampling circuit 1 performs error amplification processing on the voltage input signal and outputs a characteristic voltage signal at its output terminal. The characteristic voltage signal is the sampled voltage value. The output terminal of the sampling circuit 1 is connected to the welding machine output control circuit 3. The welding machine output control circuit 3 controls the arc voltage output by the welding machine according to the characteristic voltage signal.

[0078] In this embodiment, the voltage generation circuit 2 can be a potentiometer circuit or a microcontroller. The voltage generation circuit 2 will be described below using the potentiometer circuit 21 as an example.

[0079] Reference Figure 3 Potentiometer circuit 21 includes resistor R1 and potentiometer VR. One end of resistor R1 is connected to the power supply Vref, and the other end is connected to pin a of potentiometer VR. Pin c of potentiometer VR is grounded, and pin b is the output terminal of potentiometer circuit 21, used to output a voltage input signal. Resistor R1 and potentiometer VR divide the power supply voltage Vref. By adjusting the position of pin b of potentiometer VR, the magnitude of the voltage input signal output by potentiometer circuit 21 can be adjusted.

[0080] Reference Figure 4 The sampling circuit 1 includes a PI error amplifier U1A, with its non-inverting input terminal grounded. A resistor R24 ​​is connected to the inverting input terminal of the PI error amplifier U1A. A resistor R3 and a capacitor C1 are connected in series with the inverting input terminal before connecting to the output terminal of the PI error amplifier U1A. A capacitor C2 is also connected between the inverting input terminal and the output terminal. The capacitor C2 is connected in parallel with the series resistors R3 and C1. The voltage input signal output by the sampling circuit 1 is input to the inverting input terminal of the PI error amplifier U1A through a resistor R4. A resistor R2 is also connected to the output terminal of the PI error amplifier U1A. The end of the resistor R2 furthest from the PI error amplifier U1A serves as the voltage sampling point of the sampling circuit 1.

[0081] Reference Figure 5 The welding machine output control circuit 3 includes a control circuit 31 and a welding machine power supply circuit 32. The control circuit 31 includes a PWM chip U2 and an IGBT drive circuit 311. The COMP pin of the PWM chip U2 is connected to the output of the sampling circuit 1, i.e., it receives the characteristic voltage signal output by the sampling circuit 1. The OUTA and OUTB pins of the PWM chip U2 are both connected to the IGBT drive circuit 311, providing a square wave signal to the IGBT drive circuit 311. The square wave signal is generated from the internal processing of the PWM chip U2. The PWM chip U2 superimposes the characteristic voltage signal input from the COMP pin with the triangular wave signal and soft-start signal generated internally by the PWM chip U2 to output a square wave signal. Figure 5The peripheral circuitry related to the PWM is not shown.

[0082] Furthermore, the PWM chip can be the SG3525AP.

[0083] Reference Figure 5 The welding machine power supply circuit 32 includes a rectifier bridge BD1, a full-bridge inverter module MK1, an inverter transformer T1, and a full-wave rectifier module D1. The two input terminals of the rectifier bridge BD1 are connected to the AC power supply, and the two output terminals are respectively connected to the two input terminals of the full-bridge inverter module MK1. The control terminal of the full-bridge inverter module MK1 is connected to the IGBT drive circuit 311 in the control circuit 31, which provides drive signals to the full-bridge inverter module MK1. The two output terminals of the full-bridge inverter module MK1 are connected to the primary coil of the inverter transformer T1, and the secondary coil of the inverter transformer T1 is connected to the two input terminals of the full-wave rectifier module D1. The output terminal of the full-wave rectifier module D1 provides the arc voltage for the welding machine.

[0084] The AC power supply voltage is rectified into DC voltage by rectifier bridge BD1, and then converted back into AC voltage by full-bridge inverter module MK1. The frequency of the AC voltage output by full-bridge inverter module MK1 is affected by the IGBT drive circuit. The AC voltage is stepped down and inverted by inverter transformer T1, and then rectified by full-wave rectifier module to output the DC voltage required by the welding machine.

[0085] Reference Figure 5 and Figure 6 The output of the full-wave rectifier module D1 is also connected to a current sensor 33. The current sensor 33 detects the output current of the welding machine and outputs a current feedback signal. This current feedback signal is fed back to the input of the sampling circuit 1, where it is processed with the current setpoint signal and then subjected to error amplification to obtain the characteristic voltage signal. Therefore, the welding machine output control circuit 3 feeds back a current feedback signal to the sampling circuit 1 (refer to...). Figure 7 This constitutes a negative feedback control circuit, where the current feedback signal continuously corrects the characteristic voltage signal of the output, making the control of the welding machine output more precise.

[0086] Furthermore, the current sensor 33 can be a Hall current sensor.

[0087] Furthermore, referring to Figure 7 A given signal generation circuit 4 can be set between the voltage generation circuit 2 and the sampling circuit 1. The input terminal of the given signal generation circuit 4 is connected to the output terminal of the voltage generation circuit 2, and the output terminal of the given signal generation circuit 4 is connected to the input terminal of the sampling circuit 1. The voltage input signal provided by the voltage generation circuit 2 is buffered and inverted by the given signal generation circuit 4 to obtain the current given signal, which is then output to the input terminal of the sampling circuit 1.

[0088] Specifically, refer to Figure 8 The given signal generation circuit 4 includes a buffer unit 41 and an inverting amplifier unit 42. The buffer unit 41 includes an operational amplifier unit U3A; the inverting amplifier unit 42 includes an operational amplifier unit U3B.

[0089] The non-inverting input of operational amplifier unit U3A is connected to its output, and its output is connected to one end of resistor R32. The inverting input of operational amplifier unit U3A is connected to the output of voltage generation circuit 2. Operational amplifier unit U3A functions as a voltage follower, buffering the voltage input signal and outputting a buffered voltage signal.

[0090] The inverting input of operational amplifier unit U3B is connected to the other end of resistor R32. Resistor R34 is connected between the inverting input and the output. The output is connected to one end of resistor R35, and the other end of resistor R35 is connected to the input of sampling circuit 1. The non-inverting input of operational amplifier unit U3B is grounded. Operational amplifier U3B acts as an inverting amplifier, amplifying the voltage value output by operational amplifier unit U3A in reverse, and outputting a negative current reference signal at its output.

[0091] Furthermore, referring to Figure 7 The output of sampling circuit 1 is also connected to welding external characteristic control circuit 5. Welding external characteristic control circuit 5 converts the characteristic voltage signal output by sampling circuit 1 into an amplitude ratio and outputs a voltage feedback signal. The voltage feedback signal is fed back to the given signal generation circuit 4.

[0092] Specifically, refer to Figure 9 The welding external characteristic control circuit 5 includes an operational amplifier U4A, resistors R10, R11, R12, and R14, and diode D2. Resistor R13 connects the inverting input and output of operational amplifier U4A. One end of resistor R11 is also connected to the inverting input, and the other end of R11 is connected to the output of sampling circuit 1. One end of resistors R10 and R12 are both connected to the non-inverting input of operational amplifier U4A. The other end of resistor R10 is connected to power supply VCC, and the other end of resistor R12 is grounded. Resistors R10 and R12 form a voltage divider circuit, providing a reference voltage to the non-inverting input of operational amplifier U4A. The output of operational amplifier U4A is connected to one end of resistor R14, and the other end of resistor R14 is connected to the anode of diode D2. The cathode of diode D2 is connected to the inverting input of operational amplifier unit U3B in the given signal generation circuit 2 (see reference) through resistor R7. Figure 8 ), to provide a voltage feedback signal for the given signal generation circuit 4.

[0093] When the reference voltage at the non-inverting input of operational amplifier U4A is greater than the characteristic voltage signal, operational amplifier U4A outputs a negative voltage value, diode D2 is cut off, and the voltage feedback signal fed back to the given signal generation circuit 4 is zero. When the reference voltage at the non-inverting input of operational amplifier U4A is less than the characteristic voltage signal, operational amplifier U4A outputs a positive voltage value, diode D2 is turned on, providing a voltage feedback signal to the given signal generation circuit 4. As the characteristic voltage signal decreases, the output voltage of operational amplifier U4A increases. The voltage feedback signal is superimposed with the buffered voltage signal, and after being inverted and amplified by operational amplifier unit U3B, the output current given signal is generated.

[0094] Reference Figure 10 The voltage provided at the connection point of resistors R10 and R12 is the voltage used to determine the inflection point. Figure 10 The vertical axis represents the inflection point of 15V. Since the arc voltage output by the welding machine is controlled by the characteristic voltage signal, the characteristic voltage signal is converted into a square wave signal by the PWM chip. The characteristic voltage signal is proportional to the pulse width of the square wave signal. The square wave signal adjusts the frequency of the input power supply of the welding machine. The arc voltage output by the welding machine is proportional to the pulse width of the square wave signal. Therefore, the characteristic voltage signal is proportional to the arc voltage output by the welding machine. When the characteristic voltage increases, the output current of the welding machine increases. When the characteristic voltage is zero, the output current of the welding machine reaches its maximum value of 300A.

[0095] The implementation principle of a voltage isolation sampling circuit in this application embodiment is as follows: The voltage generation circuit 2 provides a voltage input signal to the given signal generation circuit 4. After buffering, it outputs a buffered voltage signal. The buffered voltage signal is then amplified in reverse to output a current given signal as the input of the sampling circuit 1. The sampling circuit 1 amplifies the voltage input signal by error and outputs a characteristic voltage signal. The welding machine output control circuit 3 controls the output arc voltage of the welding machine according to the characteristic voltage signal. At the same time, the current sensor 33 in the welding machine output control circuit 3 detects the current output by the welding machine and outputs a current feedback signal. The current feedback signal is fed back to the sampling circuit 1, and it is processed with the current given signal and then amplified by error. The welding external characteristic control circuit 5 performs arithmetic amplification on the characteristic voltage to provide a voltage feedback signal to the given signal generation circuit 4. The voltage feedback signal and the buffered voltage signal are superimposed and amplified in reverse to output the current given signal.

[0096] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Any feature disclosed in this specification (including the abstract and drawings) may be replaced by other equivalent or similar features unless specifically stated otherwise. That is, unless specifically stated otherwise, each feature is only one example of a series of equivalent or similar features.

Claims

1. A voltage isolation sampling method, characterized in that, include: Obtain the voltage input signal; The voltage input signal is subjected to error amplification processing to output a characteristic voltage signal; The arc voltage output by the welding machine is controlled according to the characteristic voltage signal, wherein the characteristic voltage signal is proportional to the arc voltage; After performing error amplification processing on the voltage input signal and outputting a characteristic voltage signal, the method further includes: performing amplitude scaling conversion on the characteristic voltage signal and outputting a voltage feedback signal; superimposing the voltage feedback signal and the buffer voltage signal to output a superimposed voltage signal; and performing inverse amplification processing on the buffer voltage signal to output a current command signal, specifically: performing inverse amplification processing on the superimposed voltage signal to output the current command signal. The output current of the welding machine is detected and a current feedback signal is output; the current feedback signal and the current given signal are processed to obtain a current error signal; the voltage input signal is amplified to output a characteristic voltage signal, specifically: the current error signal is amplified to output the characteristic voltage signal. The control of the arc voltage output by the welding machine based on the characteristic voltage signal specifically involves converting the characteristic voltage signal into a square wave signal, adjusting the frequency of the welding machine power supply circuit through the square wave signal, and thereby controlling the arc voltage output by the welding machine.

2. The voltage isolation sampling method according to claim 1, characterized in that, Before performing error amplification processing on the voltage input signal, the method further includes: buffering the voltage input signal and outputting a buffered voltage signal; performing inverse amplification processing on the buffered voltage signal and outputting a current command signal; specifically, performing error amplification processing on the voltage input signal and outputting a characteristic voltage signal involves: performing error amplification processing on the current command signal and outputting the characteristic voltage signal.

3. A voltage isolation sampling circuit, characterized in that, It includes a voltage generation circuit (2) for acquiring a voltage input signal, a sampling circuit (1) for amplifying the voltage input signal and outputting a characteristic voltage signal, and a welding machine output control circuit (3) for controlling the arc voltage output by the welding machine through the characteristic voltage signal, wherein the characteristic voltage signal is proportional to the arc voltage; The output of the sampling circuit (1) is connected to the welding external characteristic control circuit (5), which is connected to the given signal generation circuit (4). The welding external characteristic control circuit (5) performs amplitude proportional conversion on the characteristic voltage signal and outputs a voltage feedback signal. Then, the voltage feedback signal is superimposed on the buffer voltage signal output by the buffer unit (41) to output a superimposed voltage signal. The superimposed voltage signal is then amplified by the inverting amplification unit (42) and outputs a current given signal. The welding machine output control circuit (3) includes a current sensor (33), which detects the output current of the welding machine and outputs the current feedback signal. After the current feedback signal and the current given signal are processed, the characteristic voltage signal is output after the sampling circuit (1) performs error amplification processing. The welding machine output control circuit (3) includes a control circuit (31) and a welding machine power supply circuit (32). The control circuit (31) includes a PWM chip and an IGBT drive circuit (311). The PWM chip converts the characteristic voltage signal into a square wave signal. The square wave signal drives the IGBT drive circuit (311). The IGBT drive circuit (311) adjusts the frequency of the welding machine power supply circuit (32) and thus controls the welding machine power supply circuit (32) to output the arc voltage of the welding machine.

4. The voltage isolation sampling circuit according to claim 3, characterized in that: A given signal generation circuit (4) is provided between the voltage generation circuit (2) and the sampling circuit (1). The given signal generation circuit (4) includes a buffer unit (41) for buffering the voltage input signal and outputting a buffered voltage signal, and an inverse amplification unit (42) for inverse amplification of the buffered voltage signal and outputting a current given signal. The sampling circuit (1) performs error amplification on the current given signal output by the inverse amplification unit (42) and outputs the characteristic voltage signal.

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