An output current integration detection system for medium-frequency DC resistance welding

Abstract

The present invention provides an output current integration detection system for medium-frequency direct-current resistance welding, which includes a Rogowski coil current sensor and a main current detection circuit. The Rogowski coil current sensor is suspended on the secondary-side conductor of the measuring welding equipment, and the Rogowski coil current sensor is connected to the main current detection circuit. The main current detection circuit includes a current integration processing circuit, a signal shaping and filtering circuit, an MCU central control unit, and a power supply voltage conversion circuit. The current integration processing circuit, the signal shaping and filtering circuit, and the power supply voltage conversion circuit are all connected to the MCU central control unit. The output current integration detection system for medium-frequency direct-current resistance welding according to the present invention solves the problem that most of the existing detection systems only have a single detection range and cannot be adjusted according to different measurement situations, resulting in the measurement accuracy not meeting the requirements.

Description

Technical Field

[0001] The present invention belongs to the field of current detection, and particularly relates to an output current integral detection system for medium-frequency DC resistance welding. Background Art

[0002] In resistance welding, the welding current is one of the core process parameters, and its accuracy is crucial for the quality of the solder joints. In actual production, before the medium-frequency DC resistance welding machine is used, it is necessary to calibrate its welding output current through an external measuring device. Most of the existing detection systems only have a single detection range and cannot be adjusted according to different measurement situations, resulting in the measurement accuracy not meeting the requirements. Summary of the Invention

[0003] In view of this, the present invention proposes an output current integral detection system for medium-frequency DC resistance welding to solve the problem that most of the existing detection systems only have a single detection range and cannot be adjusted according to different measurement situations, resulting in the measurement accuracy not meeting the requirements.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] An output current integral detection system for medium-frequency DC resistance welding, comprising a Rogowski coil current sensor and a current detection main circuit. The Rogowski coil current sensor is suspended on the secondary side conductor of the measuring welding equipment, and the Rogowski coil current sensor is connected to the current detection main circuit;

[0006] The current detection main circuit includes a current integration processing circuit, an MCU central control unit, a current input trigger detection circuit, and a current measurement processing circuit. The current input trigger detection circuit includes a fourth operational amplifier and a dual D flip-flop. The output terminal of the fourth operational amplifier is connected to the clock pin of the dual D flip-flop. The input terminal of the dual D flip-flop is used to access the output detection signal of the Rogowski coil current sensor. The reverse input terminal of the dual D flip-flop is connected to the MCU central control unit. The current integration processing circuit includes a relay, a first operational amplifier, and an analog switch. There are two relays. The Rogowski coil current sensor is connected to the two relays. The output terminals of the two relays are both connected to the first operational amplifier, and the input terminals are connected to the MCU central control unit. The output terminal of the first operational amplifier is connected to the input terminal of the current measurement processing circuit. One output terminal of the analog switch is connected to the reverse input terminal of the first operational amplifier, and the other output terminal is connected to the output terminal of the first operational amplifier. The output terminal of the current measurement processing circuit is connected to the MCU central control unit.

[0007] Further, the two relays are RY1 and RY2 respectively. A resistor R1 and a resistor R2 are connected in series to the pin 6 of RY1 in sequence. A resistor R3 and a resistor R7 are connected in series to the pin 5 of RY1 in sequence. A resistor R5 and a resistor R9 are connected in series to the pin 5 of RY2 in sequence. R2, R7, and R9 are all connected to the positive input terminal of the first operational amplifier. The Cur1 terminals of RY1 and RY2 are both connected to the Rogowski coil current sensor. The connection relationship between the first operational amplifier and the MCU central control unit is as follows:

[0008] IC1_43 is connected to the PA11 pin, and IC1_44 is connected to the PA12 pin.

[0009] Further, the current measurement processing circuit is used to ensure that the signal collected by the MCU central control unit is positive. The current measurement processing circuit is connected to the MCU central control unit. The current measurement processing circuit includes resistors R14, R15, R16, R17, R18, R19, R20, R21, R24, R25, switching diodes D1, D2, capacitors C75, C76, C64, and operational amplifiers the fourth operational amplifier, the third operational amplifier. One end of R14 is connected to the pin 2 of the fourth operational amplifier, and the other end is connected to one end of R15. The other end of R15 is connected to one end of R17. The other end of R17 is connected to one end of R16. The other end of R16 is connected to the pin 2 of the fourth operational amplifier. R18 is connected in parallel with R17. The anode of the switching diode is connected to one end of R16, and the cathode of the switching diode is connected to the other end of R16. The switching diode is connected to the pin 1 of the operational amplifier the fourth operational amplifier. The pin 3 of the fourth operational amplifier is connected with a ground protection. One end of R17 is connected to the pin 6 of the third operational amplifier. One end of R19 is connected to the pin 6 of the third operational amplifier, and the other end is connected to one end of R20. The other end of R20 is connected to one end of R24. The other end of R24 is connected to one end of R25. The other end of R25 is connected to the U1_137 pin of the MCU central control unit. One end of C64 is connected to the other end of R25, and the other end of C64 is connected with a ground protection. One end of R21 is connected to the pin 6 of the third operational amplifier, and the other end of R21 is connected to the pin 7 of the third operational amplifier. The pin 5 of the third operational amplifier is connected with a ground protection.

[0010] Further, the current input trigger detection circuit includes a dual D flip-flop, a fourth operational amplifier, and a resistor R62. The inverting input terminal of the fourth operational amplifier 5 is connected to the MCU central control unit. The pin 1 of the fourth operational amplifier is connected to the pin 3 of the dual D flip-flop. One end of the resistor R62 is connected to the circuit between the pin 1 of the fourth operational amplifier and the pin 3 of the dual D flip-flop, and the other end of the resistor R62 is connected to the ground protection. The connection relationship between the current input trigger detection circuit, the MCU central control unit, and the current signal integration circuit is as follows:

[0011] The inverting output terminal of the fourth operational amplifier is connected to the clock pin 3 of the dual D flip-flop. The non-inverting output pin of the dual D flip-flop is connected to pin 1 of the analog switch. The reset pin of the dual D flip-flop of the current input trigger detection circuit is connected to PD10, and the clear pin is connected to PD11.

[0012] Further, a resistor R12, a potentiometer VR1, and a resistor R13 are connected in series in sequence to pin 1 of the first operational amplifier, and the resistor R13 is connected to pin 8 of the operational amplifier.

[0013] Further, the first operational amplifier is also connected with a capacitor anti-saturation unit. The capacitor anti-saturation unit includes a capacitor C1, a capacitor C2, and a resistor R11. Pin 2 of the first operational amplifier is also connected to the analog switch and the resistor R11 in sequence. Pin 2 of the analog switch is connected to the inverting input terminal of the first operational amplifier. Pin 3 of the analog switch is connected to the resistor R11. Pin 1 of the analog switch is connected with the current input trigger detection circuit. The resistor R11 is connected to the output terminal of the first operational amplifier. One end of the capacitor C1 is connected to the line between pin 2 of the first operational amplifier and pin 2 of the analog switch, and the other end is connected to the line between pin 6 of the first operational amplifier and pin 3 of the analog switch. One end of the capacitor C2 is connected to the line between pin 2 of the first operational amplifier and pin 2 of the analog switch, and the other end is connected to the line between pin 6 of the first operational amplifier and pin 3 of the analog switch.

[0014] Further, a test method for an output current integration detection system for medium-frequency DC resistance welding based on the above-mentioned system is characterized by including the following steps:

[0015] S1: The Rogowski coil current sensor collects the welding current and sends the collected signals to the current input trigger detection circuit and the current signal integration circuit respectively;

[0016] S2: The MCU central control unit processes the input electromotive force signal through the active integration circuit to obtain another alternating voltage signal;

[0017] S3: The current input trigger detection circuit detects the input signal and generates an input signal to be transmitted to the MCU central control unit;

[0018] S4: The MCU central control unit collects the average current signal through the ADC acquisition channel, and obtains the actual average welding current data and the welding time through calculation and processing;

[0019] S5: Transmit the average welding current data and the welding time to the display unit and the serial port transmission unit.

[0020] Compared with the prior art, the present invention has the following advantages:

[0021] (1) Through the circuit structure design of multiple ranges, the current signal integration circuit can effectively control the voltage output range of the integration circuit, improve the usage range of the overall circuit, and enhance the detection range and ability of the circuit. At the same time, users can also select appropriate measurement gears according to different measurement situations to improve the measurement accuracy. When the measured current value exceeds the corresponding measurement gear, the system will also output an alarm signal, which is beneficial to the monitoring of welding quality.

[0022] (2) The current input trigger detection circuit can significantly improve the processing speed of current detection, and can measure more welding currents within a certain period of time. It is especially suitable for the measurement occasions of multi-segment current welding and continuous point welding. By setting a reasonable acquisition threshold and controlling the circuit design of the D flip-flop output, the signal interference in the circuit can be reduced, the energization time of the welding machine current can be accurately collected, and further the accuracy of the measured current can also be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0024] Figure 1 is a schematic diagram of the current signal integration circuit according to an embodiment of the present invention;

[0025] Figure 2 is a schematic diagram of the current measurement processing circuit according to an embodiment of the present invention;

[0026] Figure 3 is a schematic diagram of the current input trigger detection circuit according to an embodiment of the present invention;

[0027] Figure 4 is a schematic diagram of the MCU central control unit according to an embodiment of the present invention;

[0028] Figure 5 is a schematic diagram of the structure of an output current integration detection system for medium-frequency DC resistance welding according to an embodiment of the present invention;

[0029] Figure 6 is a schematic diagram of the test method of an output current integration detection system for medium-frequency DC resistance welding according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other.

[0031] In the description of the present invention, it should be understood that the orientation or positional relationships indicated by the terms "center", "longitudinal", "transverse", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. are based on the orientation or positional relationships shown in the drawings. These are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus should not be construed as a limitation to the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise stated, the meaning of "a plurality" is two or more.

[0032] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, the terms "mounted", "connected", and "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

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

[0034] As Figure 1 , Figure 4 , Figure 5 shown, an output current integration detection system for medium-frequency direct current resistance welding includes a Rogowski coil current sensor and a current detection main circuit. The Rogowski coil current sensor is suspended on the secondary-side conductor of the measuring welding equipment, and the Rogowski coil current sensor is connected to the current detection main circuit;

[0035] The current detection main circuit includes a current integration processing circuit, a signal shaping and filtering circuit, an MCU central control unit, and a power supply voltage conversion circuit. The current integration processing circuit, the signal shaping and filtering circuit, and the power supply voltage conversion circuit are all connected to the MCU central control unit;

[0036] The current integration processing circuit includes a relay and a first operational amplifier OPA277. There are two relays. The Rogowski coil current sensor is connected to the two relays, and the two relays are both connected to the first operational amplifier OPA277. The first operational amplifier OPA277 is connected to the MCU central control unit.

[0037] AsFigure 1 , Figure 4 As shown, the two relays are RY1 and RY2 respectively. Resistors R1 and R2 are connected in series in sequence to pin 6 of RY1, resistors R3 and R7 are connected in series in sequence to pin 5 of RY1, resistors R5 and R9 are connected in series in sequence to pin 5 of RY2. R2, R7, and R9 are all connected to the positive input terminal of the first operational amplifier OPA277. The Cur1 terminals of RY1 and RY2 are both connected to the Rogowski coil current sensor. The connection relationship between the first operational amplifier OPA277 and the MCU central control unit is as follows:

[0038] IC1_43 is connected to pin PA11, and IC1_44 is connected to pin PA12.

[0039] As Figure 3 , Figure 4 shown, the main current detection circuit further includes a current measurement and processing circuit, which is connected to the MCU central control unit and is used to ensure that the signal collected by the MCU central control unit is positive.

[0040] As Figure 2 , Figure 4 shown, the MCU central control unit is also connected to a current measurement and processing circuit. The current measurement and processing circuit includes resistors R14, R15, R16, R17, R18, R19, R20, R21, R24, R25, switching diodes D1, D2, capacitors C75, C76, C64, and the second operational amplifier IC44A and the third operational amplifier IC44A. One end of R14 is connected to pin 2 of the second operational amplifier IC44A, and the other end is connected to one end of R15. The other end of R15 is connected to one end of R17. The other end of R17 is connected to one end of R16. The other end of R16 is connected to pin 2 of the second operational amplifier IC44A. R18 is in parallel with R17. The anode of the switching diode is connected to one end of R16, and the cathode is connected to the other end of R16. The switching diode is connected to pin 1 of the operational amplifier second operational amplifier IC44A. Pin 3 of the second operational amplifier IC44A is connected to a ground protection. One end of R17 is connected to pin 6 of the third operational amplifier IC44A. One end of R19 is connected to pin 6 of the third operational amplifier IC44A, and the other end is connected to one end of R20. The other end of R20 is connected to one end of R24. The other end of R24 is connected to one end of R25. The other end of R25 is connected to pin U1_137 of the MCU central control unit. One end of C64 is connected to the other end of R25, and the other end of C64 is connected to a ground protection. One end of R21 is connected to pin 6 of the third operational amplifier IC44A, and the other end is connected to pin 7 of the third operational amplifier IC44A. Pin 5 of the third operational amplifier IC44A is connected to a ground protection.

[0041] As Figure 2 、 Figure 4 shown, it further includes a current input trigger detection circuit for improving the processing speed of current detection. The current input trigger detection circuit includes a dual D flip-flop IC19, a fourth operational amplifier IC15, and a resistor R62. The inverting input terminal of the fourth operational amplifier IC15 is connected to the MCU central control unit. The pin 1 of the fourth operational amplifier IC15 is connected to the pin 3 of the dual D flip-flop IC19. One end of the resistor R62 is connected to the line between the pin 1 of the operational amplifier IC15 and the pin 3 of the dual D flip-flop IC19, and the other end of the resistor R62 is connected to the ground protection.

[0042] As Figure 1 shown, a resistor R12, a potentiometer VR1, and a resistor R13 are connected in series in sequence to the pin 1 of the operational amplifier, and the resistor R13 is connected to the pin 8 of the operational amplifier.

[0043] As Figure 2 、 Figure 4 shown, the first operational amplifier OPA277 is further connected with a capacitor anti-saturation unit. The capacitor anti-saturation unit includes a capacitor C1, a capacitor C2, a resistor R11, and an analog switch. The pin 2 of the first operational amplifier OPA277 is further connected to the analog switch and the resistor R11 in sequence. The pin 2 of the analog switch is connected to the inverting input terminal of the first operational amplifier OPA277. The pin 3 of the analog switch is connected to the resistor R11. The pin 1 of the analog switch is connected to the current input trigger detection circuit. The resistor R11 is connected to the output terminal of the first operational amplifier OPA277. One end of the capacitor C1 is connected to the line between the pin 2 of the first operational amplifier OPA277 and the pin 2 of the analog switch, and the other end is connected to the line between the pin 6 of the first operational amplifier OPA277 and the pin 3 of the analog switch. One end of the capacitor C2 is connected to the line between the pin 2 of the first operational amplifier OPA277 and the pin 2 of the analog switch, and the other end is connected to the line between the pin 6 of the first operational amplifier OPA277 and the pin 3 of the analog switch.

[0044] As Figure 3 、 Figure 4 shown, the current input trigger detection circuit includes a fourth operational amplifier IC15 and a dual D flip-flop IC19. The inverting output terminal of the fourth operational amplifier IC15 is connected to the clock pin 3 of the dual D flip-flop IC19. The non-inverting output pin of the dual D flip-flop IC19 is connected to the pin 1 of the analog switch, and the signal of the inverting input pin is connected to the PD10 pin of the MCU central control unit.

[0045] As Figure 6 shown, the entire main control system is designed based on the STM32F407 microcontroller.

[0046] After the signal generated by the Rogowski coil is input, the main control circuit first processes the input electromotive force signal through an active integration circuit to obtain another alternating voltage signal. This signal can accurately reproduce the waveform of the measured current signal.

[0047] B Then, through a series of rectification and filtering circuits, the current input detection logic circuit on the main control board will detect the input signal and generate an input signal to be transmitted to the MCU.

[0048] C The MCU collects the average current signal through the ADC acquisition channel, and obtains the actual average welding current data and the welding time through a series of software calculations and processes.

[0049] D Finally, it is transmitted to the display unit and the serial port transmission unit.

[0050] The entire main control system is designed based on the STM32F407 microcontroller. After the signal generated by the Rogowski coil is input, the main control circuit first processes the input electromotive force signal through an active integration circuit to obtain another alternating voltage signal. This signal can accurately reproduce the waveform of the measured current signal. Then, through a series of rectification and filtering circuits, the current input detection logic circuit on the main control board will detect the input signal and generate an input signal to be transmitted to the MCU. The MCU collects the average current signal through the ADC acquisition channel, and obtains the actual average welding current data and the welding time through a series of software calculations and processes. Finally, it is transmitted to the display unit and the serial port transmission unit.

[0051] As Figure 1 shown, in order to achieve accurate acquisition of the welding current, the present invention designs the core part of the hardware system, namely the integration processing circuit, as follows: as Figure 5The Curl end shown is the signal access end of the Rogowski coil. To achieve the acquisition of welding current under different ranges, the present invention designs to use two relays RY-1 and RY-2 to switch the input resistance value of the integrating circuit. The specific principle is as follows: The user selects the measurement range of the welding current through the button, which is divided into three ranges: 1.999, 19.99, and 199.9. When selecting the 1.999 range, the MCU controls IC1_43 and IC1_44 to be at high level, RY_1 and RY_2 are attracted, and R1, R2, R3, R7, R5, and R9 are all connected as input resistors to the integrating circuit; when selecting the 19.99 range, the MCU controls IC1_43 to be at high level and IC1_44 to be at low level, RY_1 is attracted and RY_2 is not attracted, and R1, R2, R3, and R7 are connected as input resistors to the integrating circuit; when selecting the 199.9 range, the MCU controls IC1_43 and IC1_44 to be at low level, RY_1 and RY_2 are not attracted, and R1 and R2 are connected as input resistors to the integrating circuit. The resistance value connected to the integrating circuit is determined by the output formula of the ideal operational amplifier integrator, that is

[0052]

[0053] The operational amplifier uses OPA277 and is powered by a ±15V dual power supply.

[0054] By connecting the resistor R13 and the potentiometer VR1 at the 1st and 8th pins as shown in the figure, the offset voltage of the operational amplifier is reduced. To prevent the operational amplifier from having a bias voltage and charging and discharging the capacitor, resulting in capacitor saturation, the present invention designs a parallel resistor R11 beside the capacitor. Whether it is connected to the circuit is controlled by the external signal IC6_1. When the hardware circuit detects the generation of the current signal, R11 is cut off. When the signal disappears, R11 is connected to the circuit to form a discharge loop with the capacitor and discharge the capacitor. The current input of the IC6_1 signal triggers the detection circuit.

[0055] Through the design of the multi-range circuit structure, the voltage output range of the integrating circuit can be effectively controlled, the usage range of the overall circuit can be improved, and the detection range and ability of the circuit can be enhanced. At the same time, the user can also select an appropriate measurement range according to different measurement situations to improve the measurement accuracy. When the measured current value exceeds the corresponding measurement range, the system will also output an alarm signal, which is beneficial to the monitoring of the welding quality.

[0056] Such as Figure 3As shown in the figure, the current input trigger detection circuit can detect the current input signal. The specified voltage input signal is connected to the inverting input terminal of IC15 through the MCU and the peripheral circuit design. The input signal generated by the Rogowski coil is conditioned and then connected to the non-inverting input terminal of IC15. IC15 is powered by ±15V bidirectionally. When there is no current signal input, the output of IC15 is at a low level.

[0057] When a current signal is input and reaches the set start acquisition threshold, the voltage at the non-inverting input terminal of IC15 is greater than that at the inverting input terminal, causing IC15 to output a high level. IC19 is a dual D flip-flop. Its reset signal CLR and control signal PR are reset and set by the MCU after each current detection. The trigger signal D pin is pulled high by the power supply D. When the output terminal of IC15 is connected to the clock pin of the D flip-flop, when an input current signal is detected, a rising-edge input signal is generated at the output terminal of IC15, and the D flip-flop works. The non-inverting output pin of IC19 generates a high-level signal and is passed into Figure 5 the integral circuit shown in the figure. The signal at the inverting input pin is passed into the MCU, and the ADC input acquisition of the current signal starts.

[0058] By the above method, the processing speed of current detection can be significantly improved, and more welding currents can be measured within a certain period of time. It is especially suitable for the measurement occasions of multi-segment current welding and continuous spot welding. By setting a reasonable acquisition threshold and controlling the circuit design of the D flip-flop output, the signal interference in the circuit can be reduced, the energization time of the welding machine current can be accurately acquired, and further the accuracy of the measured current can be improved.

[0059] As Figure 3 shown in the figure, the current measurement processing circuit is used to adjust the voltage signal after integral signal acquisition before inputting it into the AD acquisition port of the single-chip microcomputer. When the signal input by the integral circuit is negative, the left diode of the switching diode D1 conducts and the right diode turns off. The second operational amplifier IC44A does not work. The input signal is inverted and amplified by the third operational amplifier IC44A and then input into the AD acquisition pin of the MCU to obtain the average value of the welding current. When the signal of the integral circuit is positive, the left diode of the switching diode D1 turns off and the right diode conducts. The second operational amplifier IC44A inverts and amplifies the input integral signal. The resistance values of R15, R17, and R18 are the same. The third operational amplifier IC44A acts as an adder to add the original integral signal and the signal amplified in the opposite direction by the second operational amplifier IC44A, ultimately achieving the purpose of signal inversion. Ensure that the signals input into the AD acquisition are all positive. In actual use, the orientation of the Rogowski coil suspended on the welding arm may be opposite, so the generated voltage signals may also be completely opposite. Whether the signal is inverted or not, this circuit can ensure that the signals input into the AD acquisition are positive.

[0060] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. An output current integral detection system for medium-frequency direct current resistance welding, characterized in that: it includes a Rogowski coil current sensor and a main current detection circuit. The Rogowski coil current sensor is suspended on the secondary-side conductor of the measuring welding equipment, and the Rogowski coil current sensor is connected to the main current detection circuit; the main current detection circuit includes a current integral processing circuit, an MCU central control unit, a current input trigger detection circuit, and a current measurement processing circuit. The current input trigger detection circuit includes a fourth operational amplifier and a dual D flip-flop. The output terminal of the fourth operational amplifier is connected to the clock pin of the dual D flip-flop. The input terminal of the dual D flip-flop is used to access the output detection signal of the Rogowski coil current sensor. The reverse input terminal of the dual D flip-flop is connected to the MCU central control unit. The current integral processing circuit includes a relay, a first operational amplifier, and an analog switch. There are two relays. The Rogowski coil current sensor is connected to the two relays. The output terminals of the two relays are both connected to the first operational amplifier, and the input terminals are connected to the MCU central control unit. The output terminal of the first operational amplifier is connected to the input terminal of the current measurement processing circuit. One output terminal of the analog switch is connected to the reverse input terminal of the first operational amplifier, and the other output terminal is connected to the output terminal of the first operational amplifier. The output terminal of the current measurement processing circuit is connected to the MCU central control unit.

2. The output current integral detection system for medium-frequency direct current resistance welding according to claim 1, characterized in that: the two relays are RY1 and RY2 respectively. A resistor R1 and a resistor R2 are sequentially connected in series to the pin 6 of RY1. A resistor R3 and a resistor R7 are sequentially connected in series to the pin 5 of RY1. A resistor R5 and a resistor R9 are sequentially connected in series to the pin 5 of RY2. R2, R7, and R9 are all connected to the positive input terminal of the first operational amplifier. The Cur1 terminals of RY1 and RY2 are both connected to the Rogowski coil current sensor. The connection relationship between the first operational amplifier and the MCU central control unit is as follows: IC1_43 is connected to the PA11 pin, and IC1_44 is connected to the PA12 pin.

3. The output current integral detection system for medium-frequency direct current resistance welding according to claim 1, characterized in that: The current measurement processing circuit is used to ensure that the signal collected by the MCU central control unit is a positive value. The current measurement processing circuit is connected to the MCU central control unit. The current measurement processing circuit includes resistors R14, R15, R16, R17, R18, R19, R20, R21, R24, R25, switching diodes D1, D2, capacitors C75, C76, C64, and operational amplifiers, namely the fourth operational amplifier and the third operational amplifier. One end of R14 is connected to pin 2 of the fourth operational amplifier, and the other end is connected to one end of R15. The other end of R15 is connected to one end of R17. The other end of R17 is connected to one end of R16. The other end of R16 is connected to pin 2 of the fourth operational amplifier. R18 is in parallel with R17. The anode of the switching diode is connected to one end of R16, and the cathode of the switching diode is connected to the other end of R16. The switching diode is connected to pin 1 of the fourth operational amplifier. A ground protection is connected to pin 3 of the fourth operational amplifier. One end of R17 is connected to pin 6 of the third operational amplifier. One end of R19 is connected to pin 6 of the third operational amplifier, and the other end is connected to one end of R20. The other end of R20 is connected to one end of R24. The other end of R24 is connected to one end of R25. The other end of R25 is connected to pin U1_137 of the MCU central control unit. One end of C64 is connected to the other end of R25, and a ground protection is connected to the other end of C64. One end of R21 is connected to pin 6 of the third operational amplifier, and the other end is connected to pin 7 of the third operational amplifier. A ground protection is connected to pin 5 of the third operational amplifier.

4. An output current integration detection system for medium-frequency DC resistance welding according to claim 1, characterized in that: the current input trigger detection circuit includes a dual D flip-flop, a fourth operational amplifier, and a resistor R62. The inverting input terminal of the fourth operational amplifier is connected to the MCU central control unit. Pin 1 of the fourth operational amplifier is connected to pin 3 of the dual D flip-flop. One end of the resistor R62 is connected to the line between pin 1 of the fourth operational amplifier and pin 3 of the dual D flip-flop, and the other end of the resistor R62 is connected to a ground protection. The connection relationship between the current input trigger detection circuit, the MCU central control unit, and the current signal integration circuit is as follows: the inverting output terminal of the fourth operational amplifier is connected to the clock pin 3 of the dual D flip-flop. The non-inverting output pin of the dual D flip-flop is connected to pin 1 of the analog switch. The reset pin of the dual D flip-flop of the current input trigger detection circuit is connected to PD10, and the clear pin is connected to PD11.

5. An output current integration detection system for medium-frequency DC resistance welding according to claim 1, characterized in that: resistor R12, potentiometer VR1, and resistor R13 are connected in series in sequence to pin 1 of the first operational amplifier, and resistor R13 is connected to pin 8 of the operational amplifier.

6. An output current integration detection system for medium-frequency DC resistance welding according to claim 1, characterized in that: The first operational amplifier is further connected with a capacitor anti-saturation unit. The capacitor anti-saturation unit includes a capacitor C1, a capacitor C2, and a resistor R11. The pin 2 of the first operational amplifier is further connected to an analog switch and the resistor R11 in sequence. The pin 2 of the analog switch is connected to the inverting input terminal of the first operational amplifier. The pin 3 of the analog switch is connected to the resistor R11. The pin 1 of the analog switch is connected with a current input trigger detection circuit. The resistor R11 is connected to the output terminal of the first operational amplifier. One end of the capacitor C1 is connected to the line between the pin 2 of the first operational amplifier and the pin 2 of the analog switch, and the other end is connected to the line between the pin 6 of the first operational amplifier and the pin 3 of the analog switch. One end of the capacitor C2 is connected to the line between the pin 2 of the first operational amplifier and the pin 2 of the analog switch, and the other end is connected to the line between the pin 6 of the first operational amplifier and the pin 3 of the analog switch.

7. A test method for an output current integration detection system for medium-frequency DC resistance welding according to claim 1, characterized in that, it includes the following steps: S1: The Rogowski coil current sensor collects the welding current and sends the collected signals to the current input trigger detection circuit and the current signal integration circuit respectively; S2: The MCU central control unit processes the input electromotive force signal through the active integration circuit to obtain another alternating voltage signal; S3: The current input trigger detection circuit detects the input signal and generates an input signal to be transmitted to the MCU central control unit; S4: The MCU central control unit collects the average current signal through the ADC acquisition channel, and obtains the actual average welding current data and the welding time through calculation and processing; S5: Transmit the average welding current data and the welding time to the display unit and the serial port transmission unit.

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