Arc voltage sampling circuit suitable for welding power supply

Abstract

The utility model provides an arc voltage sampling circuit suitable for a welding power supply. The arc voltage sampling circuit comprises an interference absorption unit, a sampling conditioning unit and an isolation conversion unit. The anti-interference absorption unit is electrically connected to the output end of the welding power source so as to collect arc voltage signals. The anti-interference absorption unit comprises two common-mode absorption capacitor banks connected between a positive bus and a negative bus in series, and the middle point of the two common-mode absorption capacitor banks is electrically connected to the ground. The sampling conditioning unit comprises a sampling network and a filter capacitor, the sampling network comprises a plurality of divider resistors connected in series between positive and negative buses, the filter capacitor is connected in parallel with the output of the sampling network, and at least one stage of RC filter is formed between the filter capacitor and the divider resistors in the sampling network. The isolation conversion unit comprises an optical coupling isolator and a conversion circuit. The optical coupling isolator isolates the arc voltage sampling signal and converts the arc voltage sampling signal into a switching value signal or an analog quantity signal with various output amplitudes based on the conversion circuit.

Description

TECHNICAL FIELD

[0001] The utility model relates to the field of welding, and especially relates to an arc voltage sampling circuit suitable for welding power supply. BACKGROUND

[0002] The welding power supply usually needs to use the thrust function in the welding process. The thrust function refers to the specific function that the welding power supply can automatically increase the output current when the arc short-circuit or the droplet transition to the workpiece. This function is mainly realized by increasing the current of the arc during the droplet transition and accelerating the short-circuit time of the arc, thereby improving the weld forming effect and reducing the possibility of electrode adhesion. The arc state recognition is the basis for realizing this thrust function, and the arc state can be judged by collecting the arc voltage of the welding output loop.

[0003] There are mainly three kinds of traditional arc voltage collection methods: the first kind is to directly collect the welding loop voltage, and the collected signal is directly given to the control chip for short-circuit judgment. This collection method has simple circuit and high collection signal precision, but since the signal ground and the welding loop share the ground, the signal is easily disturbed, which is not conducive to the stability of the system. The second kind is also directly collecting the welding loop voltage, but the collected signal is first linearly isolated and then given to the control chip for short-circuit judgment. The signal obtained by this collection method is not easily disturbed, the collection signal precision is high and stable, but the linear isolation circuit is complex, and an additional auxiliary power supply is needed for isolation, which not only has high design cost but also has large circuit volume. The third kind is based on the PWM square wave analog output voltage output by the pulse width control chip. This collection method has simple circuit and strong anti-interference; but the collected signal cannot accurately feedback the actual arc voltage state and has poor precision, and the analog collected signal value has large distortion with the fluctuation of the power grid voltage.

[0004] Further, the current arc voltage sampling can only simply recognize and judge the short-circuit and droplet separation states, and cannot recognize and judge the droplet transition process, so there are problems of extensive control and low control precision. SUMMARY

[0005] The utility model discloses in order to overcome the insufficient of prior art, provide a kind of signal collection precision high and simple circuit structure's arc voltage sampling circuit suitable for welding power supply.

[0006] In order to achieve the above object, the utility model provides an arc voltage sampling circuit, it includes anti -interference absorption unit, sampling conditioning unit and isolation conversion unit. Anti -interference absorption unit electric connection in the output of welding power supply to gather arc voltage signal, and anti -interference absorption unit includes two common mode absorption capacitors groups in series between the positive bus and the negative bus and the midpoint of two common mode absorption capacitors groups electric connection to the ground. Sampling conditioning unit sets up in the output of anti -interference absorption unit and includes sampling network and filter capacitor, and sampling network includes multiple voltage dividing resistors in series between the positive bus and the negative bus, and filter capacitor is connected in parallel to the output of sampling network, and filter capacitor and voltage dividing resistor in sampling network constitute at least one RC filter between them. Isolation conversion unit includes opto -coupler isolator and conversion circuit electric connection in the output of sampling network, and opto -coupler isolator carries out the isolation to arc voltage sampling signal and converts arc voltage sampling signal into a switching quantity signal or analog quantity signal with multiple output amplitudes based on conversion circuit.

[0007] According to an embodiment of the utility model, anti -interference absorption unit still includes impedance load and back -feed absorption element connected between the positive bus and the negative bus and parallel to each other, and impedance load provides impedance for welding power supply on the input side, and back -feed absorption element absorbs impact signal of back -feed on the output side of arc voltage sampling circuit.

[0008] According to an embodiment of the utility model, sampling network includes voltage dividing resistor R1, R2 and voltage dividing resistor R3 connected between the positive bus and the negative bus in turn in series on the positive bus, and filter capacitor C2 is connected to the output side of voltage dividing resistor R1 and constitutes one RC filter with voltage dividing resistor R1, and filter capacitor C3 is connected to the output side of voltage dividing resistor R2 and constitutes two RC filters with voltage dividing resistor R2, R3.

[0009] According to an embodiment of the utility model, sampling conditioning unit still includes zener diode ZD1 set up in the output side of voltage dividing resistor R1 and reversely connected between the positive bus and the negative bus, and when zener diode ZD1 is broken down, the potential of voltage dividing resistor R1 output side is stabilized.

[0010] According to an embodiment of the utility model, sampling conditioning unit still includes zener diode ZD2 reversely connected between the output of sampling network and opto -coupler isolator, and the arc voltage signal of sampling network output drives the opto -coupler isolator of rear end after breaking down zener diode ZD2.

[0011] According to an embodiment of the utility model, conversion circuit includes pull -up resistance R4, current -limiting resistance R5 and ground filter capacitor C1, pull -up resistance R4 electric nature connects between the collector of photoelectric coupler and power voltage, the input end of current -limiting resistance R5 is connected to the common terminal of pull -up resistance R4 and photoelectric coupler collector, and its output end is as the output of conversion circuit and is connected to ground potential via ground filter capacitor C1, and current -limiting resistance R5 and ground filter capacitor C1 form a low pass filter between.

[0012] According to an embodiment of the utility model, based on arc voltage sampling signal output by sampling conditioning unit, photoelectric coupler isolator has three working states of saturation conduction, saturation cut-off and impedance,

[0013] When photoelectric coupler isolator is in impedance state, the voltage dividing network is formed between photoelectric coupler isolator and conversion circuit to make the output of conversion circuit linearly change with arc voltage sampling signal line, and conversion circuit output corresponds to the analog signal with multiple output amplitudes of arc state.

[0014] According to an embodiment of the utility model, the arc voltage sampling circuit suitable for welding power supply further includes an analog quantity identification unit, the analog quantity identification unit includes an amplifier U2, an output resistor R6 and an output filter capacitor C1, the noninverting input terminal of the amplifier U2 is connected to the conversion circuit to receive the output signal of the conversion unit, the output terminal of the amplifier U2 is connected to its inverting input terminal to form a signal follower, one end of the output resistor R6 is connected to the output of the amplifier U2, and the other end thereof is as the output of the analog quantity identification unit and is connected to the ground potential via the output filter capacitor C7.

[0015] According to an embodiment of the utility model, the arc voltage sampling circuit suitable for welding power supply further includes a high-low level identification interface, the high-low level identification interface outputs the on-off quantity signal formed under the saturation conduction and saturation cut-off of the photoelectric coupler isolator to the on-off quantity input receiving end of the welding power supply controller.

[0016] In summary, the arc voltage sampling circuit suitable for the welding power supply provided by the utility model has the advantages that the anti-interference absorption unit utilizes two common-mode capacitors connected to the midpoint of the ground potential to absorb and release the common-mode noise from the output loop of the welding power supply, the anti-interference capability of the sampling circuit is improved, and the collection accuracy of the arc voltage signal is further improved.

[0017] Further, while the front-end and rear-end isolation is performed by the optoelectronic coupler, the optoelectronic coupler is provided with three working states of saturation conduction, saturation shutdown and impedance.

[0018] In order to make the above and other objects, features and advantages of the utility model more obvious and easy to understand, the following preferred embodiments are described in detail below, and the accompanying drawings are described as follows. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 Fig. 1 shows the principle diagram of the arc voltage sampling circuit suitable for the welding power supply provided by an embodiment of the utility model.

[0020] Figure 2 Fig. 2 shows the working state diagram of the arc voltage sampling circuit. Figure 1 Fig. 3 shows the timing diagram of the arc voltage sampling circuit in working state. DETAILED DESCRIPTION

[0021] The arc state recognition based on the arc voltage sampling is the basis for the welding power supply to realize the thrust function, and the three commonly used arc voltage samplings are difficult to be compatible in the circuit volume, cost and sampling accuracy, and the existing sampling circuits can only recognize the two states of arc short circuit and arc open and have the problem of low thrust control accuracy.

[0022] Therefore, the utility model provides an arc voltage sampling circuit suitable for the welding power supply, which has strong anti-interference capability and simple circuit structure. Figure 1As shown, the arc voltage sampling circuit suitable for the welding power supply provided by the embodiment includes an anti-interference absorption unit 10, a sampling conditioning unit 20 and an isolation conversion unit 30. The anti-interference absorption unit 10 is electrically connected to the output end of the welding power supply to collect the arc voltage signal. The anti-interference absorption unit 10 includes two common-mode absorption capacitor groups connected in series between the positive and negative bus lines, and the midpoint K of the two common-mode absorption capacitor groups is electrically connected to the ground. The sampling conditioning unit 20 is arranged at the output end of the anti-interference absorption unit 10 and includes a sampling network 21 and a filter capacitor. The sampling network 21 includes a plurality of voltage dividing resistors connected in series between the positive and negative bus lines. The filter capacitor is connected in parallel to the output of the sampling network. The filter capacitor and the voltage dividing resistors in the sampling network 21 form at least one RC filter. The isolation conversion unit 30 includes an opto-isolator U1 electrically connected to the output end of the sampling network and a conversion circuit 31. The opto-isolator U1 isolates the arc voltage sampling signal and converts the arc voltage sampling signal into a switching quantity signal or an analog quantity signal with multiple output amplitudes based on the conversion circuit 31.

[0023] As shown in the figure, Figure 1 The positive bus end OUT+ and the negative bus end OUT- of the arc voltage sampling circuit suitable for the welding power supply are respectively connected to the output end of the welding power supply to collect the arc voltage signal in real time. In the embodiment, the capacitor C4 and the capacitor C6 are respectively used as the two common-mode absorption capacitor groups in the anti-interference absorption unit 10. The capacitor C4 and the capacitor C6 are connected in series between the positive bus end OUT+ and the negative bus end OUT- and the midpoint K of the two capacitors is connected to the ground. The common-mode noise input by the front-end welding power supply is released to improve the anti-interference capability of the arc voltage sampling circuit. Although the embodiment is described by taking one capacitor in each common-mode absorption capacitor group as an example. However, the utility model is not limited in this regard. In other embodiments, each common-mode absorption capacitor group can include a plurality of capacitors connected in series, but the capacitances of the capacitors in the two common-mode absorption capacitor groups are substantially the same to achieve the absorption and release of the common-mode noise.

[0024] Further, as shown in the figure, Figure 1 The anti-interference absorption unit 10 further includes an impedance load and a back-feeding absorption element connected in parallel to each other between the positive and negative bus lines. The impedance load provides high impedance for the input side of the welding power supply to reduce the influence of the arc voltage sampling circuit on the front-end welding power supply, ensure the control accuracy of the front-end welding power supply and maintain the stable output of the arc voltage in each stage. The back-feeding absorption element can absorb and release a small amount of high-frequency and high-voltage impact signals back-fed from the output side of the arc voltage sampling circuit to improve the stability and sampling accuracy of the sampling circuit. Specifically, in the embodiment, the impedance load is a resistor R7, and the back-feeding absorption element is a capacitor C5. However, the utility model is not limited in this regard. In other embodiments, the impedance load can also be an impedance unit including a resistor and a capacitor, and the back-feeding absorption element can also be an inductor.

[0025] The arc voltage signal collected from the output end of the welding power source is inputted into the sampling network 21 composed of a sampling resistor after the anti-interference absorption unit 1 absorbs the common mode noise at the input end and absorbs the reverse-impulse signal at the output end. In this embodiment, the sampling network 21 includes the sampling resistors R1 and R2 connected in series to the positive bus and the sampling resistor R3 connected between the positive and negative buses. Different arc voltage signals loaded into the sampling network 21 will generate corresponding loop currents to drive the optocoupler U1 in the rear-end isolation conversion unit 3, so that the optocoupler U1 is in different working states. In the sampling network 21, the two ends of the sampling resistor R3 serve as the output of the sampling network 21, and the sampling conditioning unit 2 includes two filter capacitors C2 and C3 connected in parallel to the two ends of the sampling resistor R3. Among them, the sampling resistor R1 and the filter capacitor C2 constitute a first-order RC filter, and the sampling resistors R2 and R3 and the filter capacitor C3 jointly form a second-order RC filter.

[0026] In the sampling conditioning unit 2 provided in this embodiment, the sampling resistors R1, R2 and R3 divide the collected arc voltage signal in voltage and power at the same time, and also jointly form a multi-stage RC filter with the two filter capacitors C2 and C3 to make the sampled arc voltage signal more stable. Since the filtering coefficient of the RC filter will affect the response speed of signal transmission, the resistance value of the sampling resistor and the capacitance value of the filter capacitor need to be adjusted according to the use environment and the welding process requirements during design. Preferably, the sampling resistors R1 and R2 are variable resistors with adjustable resistance values, and the filter capacitors C2 and C3 can also be variable capacitors.

[0027] In this embodiment, as shown in Figure 1 , the sampling conditioning unit 2 further includes a voltage stabilizing diode ZD1 arranged at the output side of the sampling resistor R1 and reversely connected between the positive and negative buses. When the collected arc voltage signal is very high and still greater than the breakdown voltage Vzd1 of the voltage stabilizing diode ZD1 after being divided by the sampling resistor R1, the voltage stabilizing diode ZD1 is broken down to stabilize the V1 point potential at the output side of the sampling resistor R1 at Vzd1. When the arc voltage signal divided by the sampling resistor R1 is less than Vzd1, the voltage stabilizing diode ZD1 does not work. The arrangement of the voltage stabilizing diode ZD1 can on the one hand protect the rear-end arc voltage sampling circuit to avoid damage to the rear-end arc voltage sampling circuit due to the impact of excessively high arc voltage signal; on the other hand, the high arc voltage signal clamping based on Vzd1 also makes the maximum driving current of the rear-end optocoupler U1 a stable value (i.e. Vzd1 / (R2+R3), thereby greatly reducing the influence of unstable arc voltage signal on the optocoupler U1 and improving the anti-interference ability of the arc voltage sampling circuit.

[0028] Further, as shown in Figure 1As shown, the sampling conditioning unit 2 further comprises a Zener diode ZD2 connected reversely between the output of the sampling network 21 and the optocoupler U1, and the arc voltage signal output by the sampling network 21 drives the optocoupler U1 at the rear end after breaking through the Zener diode ZD2, and the Zener diode ZD2 mainly realizes the functions of breaking through and shutting off in this circuit. Specifically, when the arc voltage signal is relatively high, the arc voltage sampling signal transmitted to the Zener diode ZD2 is still greater than the breakdown voltage Vzd2 of the Zener diode ZD2; the Zener diode ZD2 is turned on, and the arc voltage sampling signal transmitted to the Zener diode ZD2 continues to drive the optocoupler U1 at the rear end after being consumed by Vzd2. Conversely, if the arc voltage sampling signal transmitted to the Zener diode ZD2 is less than the breakdown voltage Vzd2 of the Zener diode ZD2, the Zener diode ZD2 remains in the off state, and the optocoupler U1 cannot receive the driving signal so that the conversion circuit 31 outputs a high level.

[0029] The Zener diodes ZD1 and ZD2 respectively clamp the upper and lower limits of the arc voltage signal responded by the optocoupler U1, avoid over-low arc voltage signals or over-high arc voltage interference, and also improve the output accuracy of the analog or switching quantity at the rear end. At the same time, the stable breakdown voltages Vzd1 and Vzd2 also facilitate the design of resistance values and capacitance values when the sampling network 21 performs voltage division and power division. However, the present application does not make any limitation in this regard. In other embodiments, the Zener diodes ZD1 and ZD2 can also not be provided.

[0030] In the arc voltage sampling circuit suitable for a welding power source provided in the present example, the optocoupler U1 realizes the isolation of signals between the front and rear stages. The conversion circuit 31 comprises a pull-up resistor R4, a current-limiting resistor R5, and a ground filter capacitor C1, the pull-up resistor R4 is electrically connected between the collector of the optocoupler U1 and the power supply voltage VCC, the input end of the current-limiting resistor R5 is connected to the common end of the pull-up resistor R4 and the collector of the optocoupler U1, the output end of the current-limiting resistor R5 serves as the output Vin of the conversion circuit 31 and is connected to the ground potential GND through the ground filter capacitor C1, and a low-pass filter is formed between the current-limiting resistor R5 and the ground filter capacitor C1.

[0031] In the present embodiment, based on the arc voltage sampling signal output by the sampling conditioning unit 2, the optocoupler U1 has three working states of saturated conduction, saturated shutdown, and impedance. As shown in FIG. 2, when the arc voltage sampling signal is relatively high, the optocoupler U1 is in the saturated conduction state, and the arc voltage sampling signal is transmitted to the rear end through the optocoupler U1. Figure 2As shown, when the welding wire is in short-circuit state or just separates from the base material to enter the arc starting state, the arc voltage signal output by the welding power supply is zero or very low. The ZD2 zener diode keeps off state, and the arc voltage sampling signal cannot drive the rear-end optocoupler U1, so the optocoupler U1 is in saturated cut-off state. The output Vin of the conversion circuit 31 (i.e. the input of the next stage circuit) is connected to the power supply voltage VCC through the pull-up resistor R4, i.e. Vin=VCC. The rear-end analog quantity identification unit or high-low level identification unit can determine that the current arc is in short-circuit state or arc starting state based on this.

[0032] With the continuous separation of the welding wire from the base material, the arc voltage signal gradually increases, and the arc voltage signal sampled by the sampling network 21 breaks through the ZD2 zener diode and drives the optocoupler U1 to enter the impedance state. As shown, Figure 2 In the impedance state, the pull-up resistor R4 in the conversion circuit 31 and the output end of the optocoupler U1 are connected in series to form a voltage division network, and the output Vin of the conversion circuit 31 is between VCC and GND and linearly changes with the arc voltage sampling signal. At this time, the analog quantity signal output by the conversion circuit 31 in this state can be obtained. Based on the preset at least one standard arc voltage signal representing the droplet transfer state, the obtained analog quantity signal is judged to identify the transfer state of the droplet.

[0033] With the continuous increase of the arc length, the arc voltage also continuously increases, and the rear-end optocoupler U1 enters the saturated conduction state. The output end of the optocoupler U1 is completely conductive, and the output Vin of the conversion circuit 31 is connected to GND through the current limiting resistor R5, i.e. Vin=GND. The rear-end analog quantity identification unit or high-low level identification unit can determine that the current arc gradually enters the necking state before the arc is disconnected based on this. Further, during the continuous increase of the arc voltage signal, if the V1 point potential on the output side of the voltage division resistor R1 is greater than the breakdown voltage Vzd1 of the ZD1 zener diode, the ZD1 zener diode is broken down, and the V1 point potential is stabilized at Vzd1, so that the rear-end optocoupler U1 is in saturated conduction state. In this embodiment, the V1 point potential at which the optocoupler U1 initially enters the saturated conduction state will be less than Vzd1, i.e. the optocoupler U1 has entered the saturated conduction state when the ZD1 zener diode is not broken down. This setting makes the optocoupler U1 can isolate and convert the arc voltage signal in the entire impedance range to increase the identification range of the arc voltage state. However, the present application does not make any limitation on this.

[0034] In the embodiment, the output Vin of the conversion circuit 31 is directly transmitted as an analog quantity, which can be directly connected to the high-low level identification interface 4 (such as the GPIO interface of the controller MCU) at the rear end to identify the high-low level. Specifically, the high-low level identification interface 4 identifies the switching quantity signal (i.e. GND and VCC) formed under the saturation conduction and saturation shutdown of the optocoupler isolator U1, thereby realizing the judgment of the two states of the arc short circuit and the arc disconnection.

[0035] Further, the arc voltage sampling circuit suitable for the welding power source provided by the embodiment further comprises an analog quantity identification unit 5, which comprises an amplifier U2, an output resistor R6 and an output filter capacitor C7. The non-inverting input terminal of the amplifier U2 is connected to the conversion circuit 31 to receive the output signal Vin of the conversion unit 31, and the output terminal of the amplifier U2 is connected to its inverting input terminal to form a signal follower. One end of the output resistor R6 is connected to the output of the amplifier U2, and the other end thereof is connected to the ground potential through the output filter capacitor C7 as the output of the analog quantity identification unit 5. In the analog quantity identification unit 5 provided by the embodiment, the amplifier U2 is used for signal following and front-back signal blocking, and the output resistor R6 and the output filter capacitor C7 realize low-pass filtering. The filtered signal is directly transmitted to the ADC sampling pin of the rear-end controller (such as the MCU or DSP) for real-time data acquisition. The controller judges the signal input by the ADC sampling pin based on one or more standard arc voltage signals representing the molten droplet transfer state, and then accurately identifies the multiple states of the arc during the molten droplet transfer. Specifically, when the signal input by the ADC sampling pin of the controller is close to the standard arc voltage signal during the molten droplet transfer, it indicates that the current arc voltage is in the molten droplet transfer state; and when the signal input by the ADC sampling pin is close to the standard arc voltage signal during the molten droplet ejection, it indicates that the current arc voltage is in the ejection transfer state. If the input of the ACD sampling pin is VCC, it indicates that the current arc voltage is in the short circuit or arc starting state. If the input of the ACD sampling pin is GND, it indicates that the current arc voltage is in the necking before disconnection or the disconnection state.

[0036] However, the present application does not make any limitation in this regard. In other embodiments, an analog quantity sampling circuit and a comparator can be used instead of the analog quantity identification unit provided by the embodiment to realize the judgment of the arc state. Specifically, the analog quantity sampling circuit can periodically collect the output signal Vin of the conversion circuit 31, and compare the collected output signal Vin with at least one preset standard arc voltage signal, thereby realizing the identification of each stage of the molten droplet in the non-short circuit state.

[0037] In summary, the arc voltage sampling circuit suitable for the welding power supply provided by the utility model, the anti-interference absorption unit utilizes two common-mode capacitors connected with the midpoint of the ground potential to absorb and release the common-mode noise from the output loop of the welding power supply, the anti-interference ability of the sampling circuit is improved, and the collection precision of the arc voltage signal is further improved. The sampling conditioning circuit collects the arc voltage signal through the sampling network composed of the voltage dividing resistor; at the same time, the filter capacitor is arranged in parallel with the output of the sampling network, the voltage dividing resistor and the filter capacitor in the sampling network are utilized to form at least one RC filter, the collected signal is filtered and conditioned at the same time of sampling the arc voltage signal, and therefore the precision of the arc voltage signal after sampling is further improved. The arc voltage signal after sampling is sent into the optoelectronic coupler in the isolation conversion unit, the front-end sampling and the rear-end control signal (on-off signal or analog signal) are isolated based on the optoelectronic coupler, and the anti-interference strength of the rear-end control signal is greatly improved.

[0038] Further, while the front-end and rear-end isolation is performed by the optoelectronic coupler, the optoelectronic isolator has three working states of saturation conduction, saturation shutdown and impedance. In the impedance state, the voltage dividing network is formed between the optoelectronic isolator and the conversion circuit to make the output of the conversion circuit linearly change with the arc voltage sampling signal. Based on the output of the conversion circuit in the impedance state, the fine identification of the droplet transfer state in the welding process can be accurately judged, and the accurate control of the thrust function in the welding process is realized.

[0039] Although the utility model has disclosed as above by the preferred embodiment, however, is not used to limit the utility model, any skilled person, without departing from the spirit and scope of the utility model, can make some changes and adornments, therefore the protection scope of the utility model is accurate when the range required to be protected by the claim book.

Claims

1. An arc voltage sampling circuit suitable for welding power sources, characterized in that, The application relates to a welding arc voltage sampling circuit. The welding arc voltage sampling circuit comprises an anti-interference absorption unit electrically connected to the output end of a welding power source to collect an arc voltage signal, wherein the anti-interference absorption unit comprises two common-mode absorption capacitor groups connected in series between positive and negative bus lines and the midpoints of the two common-mode absorption capacitor groups are electrically connected to the ground; a sampling conditioning unit arranged at the output end of the anti-interference absorption unit and comprising a sampling network and a filter capacitor, wherein the sampling network comprises a plurality of voltage dividing resistors connected in series between the positive and negative bus lines, the filter capacitor is connected in parallel to the output of the sampling network, and at least one RC filter is formed between the filter capacitor and the voltage dividing resistors in the sampling network; an isolation conversion unit comprising an optical coupling isolator electrically connected to the output end of the sampling network and a conversion circuit, wherein the optical coupling isolator isolates the arc voltage sampling signal and converts the arc voltage sampling signal into a switching quantity signal or an analog quantity signal with multiple output amplitudes based on the conversion circuit.

2. The arc voltage sampling circuit adapted for use with a welding power source of claim 1, wherein, The anti-interference absorption unit further comprises an impedance load and a back-feeding absorption element connected in parallel between the positive and negative bus lines, the impedance load provides impedance for the welding power source at the input side, and the back-feeding absorption element absorbs the impact signal back-fed at the output side of the arc voltage sampling circuit.

3. The arc voltage sampling circuit for a welding power source of claim 1, wherein, The sampling network comprises voltage dividing resistors R1 and R2 connected in series on the positive bus line and a voltage dividing resistor R3 connected between the positive and negative bus lines, the filter capacitor C2 is connected to the output side of the voltage dividing resistor R1 and forms a first-order RC filter with the voltage dividing resistor R1, and the filter capacitor C3 is connected to the output side of the voltage dividing resistor R2 and forms a second-order RC filter with the voltage dividing resistors R2 and R3.

4. The arc voltage sampling circuit adapted for use with a welding power source of claim 3, wherein, The sampling conditioning unit further comprises a voltage stabilizing diode ZD1 arranged at the output side of the voltage dividing resistor R1 and reversely connected between the positive and negative bus lines, and the voltage stabilizing diode ZD1 stabilizes the potential at the output side of the voltage dividing resistor R1 when broken.

5. The arc voltage sampling circuit suitable for use in a welding power source of claim 1 or 4, wherein, The sampling conditioning unit further comprises a voltage stabilizing diode ZD2 reversely connected between the output end of the sampling network and the optical coupling isolator, and the arc voltage signal output by the sampling network drives the optical coupling isolator at the rear end after breaking the voltage stabilizing diode ZD2.

6. The arc voltage sampling circuit adapted for use in a welding power supply of claim 1, wherein, The conversion circuit comprises a pull-up resistor R4, a current limiting resistor R5 and a ground filter capacitor C1, the pull-up resistor R4 is electrically connected between the collector of the photoelectric coupler and the power supply voltage, the input end of the current limiting resistor R5 is connected to the common end of the pull-up resistor R4 and the collector of the photoelectric coupler, the output end of the current limiting resistor R5 is the output of the conversion circuit and is connected to the ground potential through the ground filter capacitor C1, and a low-pass filter is formed between the current limiting resistor R5 and the ground filter capacitor C1.

7. The arc voltage sampling circuit adapted for use in a welding power supply of claim 1, wherein, Based on the arc voltage sampling signal output by the sampling conditioning unit, the optical coupling isolator has three working states of saturated conduction, saturated shutdown and impedance; when the optical coupling isolator is in the impedance state, a voltage dividing network is formed between the optical coupling isolator and the conversion circuit to make the output of the conversion circuit linearly change with the arc voltage sampling signal, and the conversion circuit outputs an analog quantity signal with multiple output amplitudes corresponding to the state of the electric arc.

8. The arc voltage sampling circuit adapted for use in a welding power supply of claim 6, wherein, The arc voltage sampling circuit suitable for the welding power source further comprises an analog quantity identification unit, the analog quantity identification unit comprises an amplifier U2, an output resistor R6 and an output filter capacitor C1, the non-inverting input end of the amplifier U2 is connected to the conversion circuit to receive the output signal of the conversion unit, the output end of the amplifier U2 is connected to the inverting input end to form a signal follower, one end of the output resistor R6 is connected to the output of the amplifier U2, the other end of the output resistor R6 is connected to the ground potential as the output of the analog quantity identification unit and through the output filter capacitor C7.

9. The arc voltage sampling circuit adapted for use in a welding power supply of claim 1 or 7, wherein, The arc voltage sampling circuit suitable for the welding power source further comprises a high-low level identification interface, the high-low level identification interface outputs the switching quantity signal formed under the saturation conduction and the saturation cut-off of the optocoupler isolator to the switching quantity input receiving end of the welding power source controller.

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