Inverter welding machine protection circuit and electric welding machine

Abstract

An inverter welding machine protection circuit and an electric welding machine, wherein an input voltage detection circuit detects an input voltage signal to generate an input voltage detection signal; a control circuit generates a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal; an overvoltage protection circuit generates a first protection signal to disconnect a first direct current according to the input voltage signal being greater than a first voltage threshold, and controls the on-off state of the first direct current according to the switch control signal; a current regulating circuit regulates a rectified voltage signal output by a rectifier circuit according to the disconnection of the first direct current; a power correction circuit performs power correction on the rectified voltage signal according to the correction enable signal and the second direct current to generate a correction voltage signal; an inverter rectifier circuit performs inversion rectification on the correction voltage signal according to the inverter control signal to generate a drive voltage signal; startup surge protection is realized, and hardware and software dual overvoltage protection is realized, thereby improving the stability and reliability of overvoltage protection.

Description

Technical Field

[0001] The present application belongs to the technical field of circuit protection, and in particular relates to an inverter welding machine protection circuit and an electric welding machine. Background Art

[0002] An inverter welding machine refers to an arc welding power supply that uses inverter technology. Its working principle is that the AC voltage of the mains is rectified by a rectifier module, power corrected by a PFC (Power Factor Correction) circuit, and energy stored by capacitor filtering to become high-voltage DC power. The DC power is converted into a high-frequency AC square wave through an inverter unit. After the AC square wave is stepped down by a main transformer, it is converted into a low-voltage, high-current DC output again through diode rectification and inductor filtering.

[0003] At present, the traditional inverter welding machine with PFC circuit generally has a complicated timing. Improper power-on timing or untimely control can easily lead to circuit damage. To this end, a PFC inductor is usually connected in series with a boost diode and then in parallel with a protection diode to protect the circuit. However, since the boost diode is a fast recovery diode, its ability to withstand surge current is weak. In addition, at the moment of startup, the voltage of the filter capacitor has not yet been established. Due to the charging of the large capacitor, the current passing through the PFC inductor is large, and it is possible that it is the maximum value of the sine wave at the moment of connection. Due to the large current, the PFC inductor is easily magnetically saturated at this time. Once magnetically saturated and the PFC circuit is working, the current of the PFC switch tube will lose its limit, causing the PFC switch tube to burn out.

[0004] Therefore, the traditional technical solution has the problem that a protection diode needs to be designed to protect the boost diode, and the protection stability is poor, the power safety is low, and the protection function is single. Summary of the invention

[0005] The purpose of the present application is to provide an inverter welding machine protection circuit and an electric welding machine, aiming to solve the problems existing in the traditional technical solution of an inverter welding machine with a PFC circuit, that a protection diode needs to be designed to protect the boost diode, and the protection stability is poor, the power safety is low, and the protection function is single.

[0006] A first aspect of an embodiment of the present application provides an inverter welding machine protection circuit connected to an input power supply, the inverter welding machine protection circuit comprising:

[0007] an AC rectifier circuit, connected to the input power supply and configured to rectify an input voltage signal provided by the input power supply to generate a rectified voltage signal;

[0008] an input voltage detection circuit, connected to the input power supply and configured to detect the input voltage signal to generate an input voltage detection signal;

[0009] a control circuit connected to the input voltage detection circuit and configured to generate a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal;

[0010] an overvoltage protection circuit, connected to the input power supply, the control circuit and the AC rectifier circuit, configured to detect the input voltage signal, and generate a first protection signal to disconnect the first DC power when the input voltage signal is greater than a first voltage threshold, and control the on / off state of the first DC power according to the switch control signal;

[0011] a current regulating circuit connected to the input power supply, the overvoltage protection circuit and the AC rectifying circuit, and configured to regulate a current corresponding to the rectified voltage signal according to a disconnection state of the first direct current;

[0012] a power correction circuit connected to the AC rectification circuit and the control circuit, and configured to perform power factor correction on the rectified voltage signal according to the correction enable signal and the second DC power to generate a correction voltage signal;

[0013] The inverter rectifier circuit is connected to the control circuit and the power correction circuit, and is configured to perform inversion and rectification processing on the correction voltage signal according to the inverter control signal to generate a driving voltage signal.

[0014] In one embodiment, the control circuit is further configured to generate an alarm prompt signal according to the input voltage detection signal, and the inverter welding machine protection circuit further includes:

[0015] The display alarm circuit is connected to the control circuit and is configured to display an alarm prompt according to the alarm prompt signal.

[0016] In one embodiment, the inverter welding machine protection circuit further includes:

[0017] An auxiliary power supply circuit is connected to the input power supply, the input voltage detection circuit, the overvoltage protection circuit and the power correction circuit, and is configured to generate a feedback voltage signal, the first direct current and the second direct current according to the input voltage signal; the input voltage detection circuit is also configured to detect the feedback voltage signal to generate the input voltage detection signal.

[0018] In one embodiment, the overvoltage protection circuit includes:

[0019] an anti-reverse connection unit, connected to the input power supply and the AC rectifier circuit, and configured to prevent the input voltage signal from being reversely connected;

[0020] an overvoltage detection unit, connected to the anti-reverse connection unit, configured to detect the input voltage signal and conduct the input voltage signal when the input voltage signal is greater than the first voltage threshold;

[0021] The isolating switch unit is connected to the overvoltage detection unit, the input power supply, the current regulating circuit, the control circuit and the AC rectifying circuit, and is configured to generate the first protection signal according to the input voltage signal to disconnect the first DC power.

[0022] In one embodiment, the power correction circuit includes:

[0023] a driving switch unit, connected to the control circuit, and configured to control the on and off state of the second direct current according to the correction enable signal;

[0024] a correction control unit, connected to the driving switch unit and configured to generate a correction control signal according to the second direct current;

[0025] The power correction unit is connected to the AC rectifier circuit, the correction control unit and the inverter rectifier circuit, and is configured to perform power factor correction on the rectified voltage signal according to the correction control signal to generate a correction voltage signal.

[0026] In one embodiment, the current regulating circuit includes: a thermistor; wherein a first end of the thermistor is connected to the overvoltage protection circuit and the input power supply, and a second end of the thermistor is connected to the overvoltage protection circuit and the AC rectifier circuit.

[0027] In one embodiment, the isolation switch unit includes: a first photoelectric coupler, a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first diode, a second diode, a first transistor, a second transistor and a first relay; wherein the first end of the first capacitor, the cathode of the first diode and the anode end of the first photoelectric coupler are connected to the overvoltage detection unit, the second end of the first capacitor, the anode of the first diode and the cathode end of the first photoelectric coupler are connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to the current regulation circuit, the emitter end of the first photoelectric coupler is connected to the power supply ground, and the collector end of the first photoelectric coupler is connected to the third resistor. The first end of the first transistor is connected to the base of the first transistor, the second end of the third resistor, the first end of the fourth resistor and the first end of the second capacitor are commonly connected to the power correction circuit, the second end of the fourth resistor and the second end of the second capacitor are connected to the power ground, the emitter of the first transistor is connected to the base of the second transistor, the collector of the first transistor is connected to the first end of the relay coil of the first relay, the anode of the second diode and the collector of the second transistor, the emitter of the second transistor is connected to the power ground, the second end of the relay coil and the cathode of the second diode are commonly connected to the first DC terminal, the first end of the relay normally-open switch of the first relay is connected to the second end of the second resistor, and the second end of the relay normally-open switch is connected to the AC rectifier circuit.

[0028] In one embodiment, the driving switch unit includes: a fifth resistor, a sixth resistor, a seventh resistor, a third diode, a first field effect transistor, a third triode and a second photoelectric coupler; wherein, the anode of the third diode is connected to the second DC terminal, the cathode of the third diode is connected to the drain of the first field effect transistor, the source of the first field effect transistor and the first end of the fifth resistor are commonly connected to the power correction circuit, the gate of the first field effect transistor is connected to the first end of the seventh resistor, the second end of the seventh resistor and the second end of the fifth resistor are connected to the collector end of the second photoelectric coupler, the emitter end of the second photoelectric coupler is connected to the power ground, the anode end of the second photoelectric coupler is connected to the second end of the sixth resistor, the first end of the sixth resistor is connected to the first DC terminal, the cathode end of the second photoelectric coupler is connected to the collector of the third triode, the emitter of the third triode is connected to the power ground, and the base of the third triode is connected to the control circuit.

[0029] In one embodiment, the input voltage detection circuit includes: a fourth diode, a fifth diode, an eighth resistor and a ninth resistor; wherein, the anode of the fourth diode and the cathode of the fifth diode are commonly connected to the auxiliary power supply circuit, the cathode of the fourth diode is connected to the first end of the eighth resistor, the second end of the eighth resistor and the first end of the ninth resistor are commonly connected to the control circuit, and the second end of the ninth resistor is connected to the power ground.

[0030] A second aspect of the embodiments of the present application provides an electric welder, the electric welder comprising the inverter welding machine protection circuit as described in any one of the above items.

[0031] Compared with the prior art, the embodiments of the present invention have the following beneficial effects: the above-mentioned inverter welding machine protection circuit rectifies the input voltage signal provided by the input power supply through the AC rectifier circuit to generate a rectified voltage signal; the input voltage detection circuit detects the input voltage signal to generate an input voltage detection signal; the control circuit generates a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal; the overvoltage protection circuit detects the input voltage signal, and generates a first protection signal to disconnect the first direct current when the input voltage signal is greater than the first voltage threshold, and controls the on-off state of the first direct current according to the switch control signal; the current regulation The circuit adjusts the current corresponding to the rectified voltage signal according to the disconnection state of the first direct current; the power correction circuit performs power factor correction on the rectified voltage signal according to the correction enable signal and the second direct current to generate a correction voltage signal; the inverter rectifier circuit performs inversion and rectification processing on the correction voltage signal according to the inverter control signal to generate a drive voltage signal; protection is achieved against startup surges to prevent the huge surge current that will be generated by the sudden change in voltage of the large electrolytic capacitor in the inverter rectifier circuit at the beginning of the inverter welding machine starting up from damaging circuit components, and hardware and software dual overvoltage protection can be achieved without the use of protection diodes, thereby improving the stability and safety reliability of overvoltage protection. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 A structural schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application;

[0033] Figure 2 Another structural schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application;

[0034] Figure 3 Another structural schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application;

[0035] Figure 4 Another structural schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application;

[0036] Figure 5 Another structural schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application;

[0037] Figure 6 An exemplary circuit schematic diagram of an inverter welding machine protection circuit provided in one embodiment of the present application. DETAILED DESCRIPTION

[0038] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0039] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it can be directly on the other element or indirectly on the other element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or indirectly connected to the other element.

[0040] It should be understood that the orientation or position relationship indicated by terms such as "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside" and "outside" are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0041] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0042] Figure 1 The structure diagram of the inverter welding machine protection circuit provided by the first embodiment of the present application is shown. For the convenience of explanation, only the part related to the present embodiment is shown, which is described in detail as follows:

[0043] See also Figure 1 An inverter welding machine protection circuit is connected to an input power supply 01. The inverter welding machine protection circuit includes: an input voltage detection circuit 11, a control circuit 12, an overvoltage protection circuit 13, a current regulation circuit 14, an AC rectification circuit 15, a power correction circuit 16 and an inverter rectification circuit 17.

[0044] The AC rectifier circuit 15 is connected to the input power supply 01 and configured to rectify the input voltage signal provided by the input power supply 01 to generate a rectified voltage signal; the input voltage detection circuit 11 is connected to the input power supply 01 and configured to detect the input voltage signal to generate an input voltage detection signal; the control circuit 12 is connected to the input voltage detection circuit 11 and configured to generate a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal; the overvoltage protection circuit 13 is connected to the input power supply 01, the control circuit 12 and the AC rectifier circuit 15, and configured to detect the input voltage signal and generate a first protection signal when the input voltage signal is greater than a first voltage threshold. The first direct current is disconnected, and the on / off state of the first direct current is controlled according to the switch control signal; the current regulating circuit 14 is connected to the input power supply 01, the overvoltage protection circuit 13 and the AC rectifier circuit 15, and is configured to regulate the current corresponding to the rectified voltage signal according to the disconnected state of the first direct current; the power correction circuit 16 is connected to the AC rectifier circuit 15 and the control circuit 12, and is configured to perform power factor correction on the rectified voltage signal according to the correction enable signal and the second direct current to generate a correction voltage signal; the inverter rectifier circuit 17 is connected to the control circuit 12 and the power correction circuit 16, and is configured to perform inversion and rectification processing on the correction voltage signal according to the inverter control signal to generate a drive voltage signal.

[0045] In a specific implementation, optionally, the input power supply 01 is an alternating current, and the alternating current is rectified by the AC rectifier circuit 15 to generate a rectified voltage signal, and the rectified voltage signal is processed by the power correction circuit 16 to perform power factor correction and other processing to generate a correction voltage signal, and the inverter rectifier circuit 17 performs inversion and rectification and other processing on the correction voltage signal to generate a drive voltage signal, and the drive voltage signal is a low-voltage and high-current direct current to drive the load. The current regulating circuit 14 is specifically connected to the negative output terminal of the input power supply 01, the second terminal and the third terminal of the overvoltage protection circuit 13, and the negative input terminal of the AC rectifier circuit 15. The first terminal of the overvoltage protection circuit 13 is connected to the positive output terminal of the input power supply 01 and the positive input terminal of the AC rectifier circuit 15. When the inverter welding machine is started, the overvoltage protection circuit 13 disconnects the first DC power according to the fact that the switch control signal is not received and the first protection signal is not generated. That is, at startup, the overvoltage protection circuit 13 maintains the state of disconnecting the first DC power by default, and absorbs the startup surge current through the current regulating circuit 14 connected in series between the negative input end of the AC rectifier circuit 15 and the negative output end of the input power supply 01, thereby adjusting the input current, and then adjusting the current corresponding to the rectified voltage signal, thereby realizing startup surge protection for the components in the circuit. The startup process is completed, and the control circuit 12 generates and outputs a first switch control signal, a first correction enable signal and a first inverter enable signal according to the input voltage detection signal being less than the second voltage threshold. The overvoltage protection circuit 13 controls the conduction of the first direct current according to the first switch control signal, so that the overvoltage protection circuit 13 short-circuits the current regulation circuit 14 and disconnects the regulation of the rectified voltage signal by the current regulation circuit 14; at the same time, the power correction circuit 16 connects the second direct current according to the first correction enable signal, and performs power factor correction on the rectified voltage signal according to the second direct current to generate a correction voltage signal, and the inverter rectifier circuit 17 performs inversion and rectification on the correction voltage signal according to the first inverter control signal to generate a drive voltage signal, thereby achieving normal operation when the input voltage signal is not over-voltage.During normal operation, on the one hand, the overvoltage protection circuit 13 detects the size of the input voltage signal, and generates a first protection signal to disconnect the first DC power when the input voltage signal is greater than the first voltage threshold (i.e., overvoltage). The overvoltage protection circuit 13 does not short-circuit the current regulating circuit 14, and absorbs the current corresponding to the input voltage signal through the current regulating circuit 14, thereby regulating the rectified voltage signal. When the rectified voltage signal is adjusted to a very small value (close to zero), the AC rectifier circuit 15 can be regarded as an open circuit. At this time, the subsequent power correction circuit 16 and the inverter rectifier circuit 17 will not be damaged by the overvoltage of the input voltage signal, thereby realizing hardware overvoltage protection. At this time, on the other hand, the control circuit 12 determines that the input voltage signal is too large (i.e., the input voltage detection signal generated by the input voltage detection circuit 11 is greater than or equal to the second voltage threshold. When the input voltage is greater than or equal to the second voltage threshold, the control circuit 12 generates and outputs a second switch control signal, a second correction enable signal and a second inverter control signal according to the input voltage detection signal being greater than or equal to the second voltage threshold. The overvoltage protection circuit 13 disconnects the first DC power according to the second switch control signal, so that the current regulation circuit 14 absorbs the current corresponding to the input voltage signal, thereby achieving the purpose of regulating the rectified voltage signal. At the same time, the power correction circuit 16 disconnects from the second DC power according to the second correction enable signal, that is, disconnects the second DC power supply to the power correction circuit 16, stops performing power factor correction processing on the rectified voltage signal, and stops generating the correction voltage signal. The inverter rectifier circuit 17 stops performing inversion processing on the correction voltage signal according to the second inverter control signal, and stops generating the drive voltage signal, thereby realizing software-controlled overvoltage protection.

[0046] Optionally, the switch control signal includes a first switch control signal and a second switch control signal, the correction enable signal includes a first correction enable signal and a second correction enable signal, and the inversion control signal includes a first inversion control signal and a second inversion control signal. The first switch control signal and the second switch control signal may be switch control signals of different levels, for example, the first switch control signal is a high-level switch control signal, and the second switch control signal is a low-level switch control signal. Optionally, the first voltage threshold and the second voltage threshold may be the same or different.

[0047] The embodiment of the present application utilizes an overvoltage protection circuit and a current regulation circuit in combination with an input voltage detection circuit and a control circuit to achieve protection against startup surges, so as to prevent the huge surge current that will be generated by the sudden change in voltage of the large electrolytic capacitor in the inverter rectifier circuit when the inverter welding machine is started up from damaging circuit components. It can also achieve dual overvoltage protection of hardware and software without the need for a protection diode, thereby improving the stability and safety reliability of the overvoltage protection.

[0048] See also Figure 2In one embodiment, the control circuit 12 is further configured to generate an alarm prompt signal according to the input voltage detection signal, and the inverter welding machine protection circuit also includes: a display alarm circuit 18.

[0049] The display alarm circuit 18 is connected to the control circuit 12 and is configured to display an alarm prompt according to the alarm prompt signal.

[0050] In a specific implementation, the display alarm circuit 18 includes a display screen, which can display alarm prompt information through the display screen, such as alarm prompt characters, alarm prompt flashing pages, and alarm prompt lights, etc., to remind users that abnormal conditions such as overvoltage have occurred, making it easier for users to take safety measures, reduce safety hazards in electricity use, and improve the reliability and practicality of the inverter welding machine protection circuit.

[0051] See also Figure 3 In one embodiment, the inverter welding machine protection circuit further includes: an auxiliary power supply circuit 19.

[0052] The auxiliary power supply circuit 19 is connected to the input power supply 01, the input voltage detection circuit 11, the overvoltage protection circuit 13 and the power correction circuit 16, and is configured to generate a feedback voltage signal, a first direct current and a second direct current according to the input voltage signal; the input voltage detection circuit 11 is also configured to detect the feedback voltage signal to generate an input voltage detection signal.

[0053] In a specific implementation, the auxiliary power supply circuit 19 performs rectification and voltage transformation on the input voltage signal to generate a feedback voltage signal, a first direct current, and a second direct current. The first direct current is used to power the overvoltage protection circuit 13, etc.; the second direct current is used to power the power correction circuit 16. In this embodiment, the input voltage detection circuit 11 detects the feedback voltage signal output by the auxiliary power supply circuit 19 to generate an input voltage detection signal and output it to the control circuit 12, so as to achieve the purpose of detecting and monitoring the input voltage. The feedback voltage signal generated after the input voltage signal is rectified and transformed is a direct current signal, and the voltage value is less than the voltage value corresponding to the input voltage signal. Therefore, the feedback voltage signal is detected to realize the detection of the input voltage signal, thereby improving the accuracy and safety of the input voltage detection.

[0054] In one embodiment, the first direct current and the second direct current may also be provided by other voltage conversion circuits or a power adapter.

[0055] See also Figure 4 In one embodiment, the overvoltage protection circuit 13 includes: an anti-reverse connection unit 131, an overvoltage detection unit 132, an isolation switch unit 133 and a surge suppression unit 134.

[0056] The anti-reverse connection unit 131 is connected to the input power supply 01 and the AC rectifier circuit 15, and is configured to prevent the input voltage signal from being reversed; the overvoltage detection unit 132 is connected to the anti-reverse connection unit 131, and is configured to detect the input voltage signal and turn on the input voltage signal when the input voltage signal is greater than a first voltage threshold; the isolating switch unit 133 is connected to the overvoltage detection unit 132, the input power supply 01, the current regulating circuit 14, the control circuit 12 and the AC rectifier circuit 15, and is configured to generate a first protection signal according to the input voltage signal to disconnect the first direct current.

[0057] In a specific implementation, the anti-reverse connection unit 131 has unidirectional conductivity, and can prevent the input voltage signal from being reversely connected, thereby performing reverse connection protection on the inverter welding machine protection circuit and the input power supply 01. When the inverter welding machine is started, there is no overvoltage, the overvoltage detection unit 132 does not conduct the input voltage signal, the isolation switch unit 133 is in a state of disconnecting the first direct current, and the startup surge current is absorbed by the current regulating circuit 14, thereby realizing startup surge protection for the components in the circuit. During normal operation after the startup is completed, when the overvoltage detection unit 132 detects the input voltage signal and conducts the input voltage signal to the isolation switch unit 133 when the input voltage signal is greater than the first voltage threshold, the isolation switch unit 133 generates a first protection signal according to the input voltage signal to disconnect the first DC power, so that the switch in the isolation switch unit 133 is in an off state, thereby not short-circuiting the current regulation circuit, and absorbing the current corresponding to the input voltage signal through the current regulation circuit 14, thereby regulating the rectified voltage signal; at this time, the control circuit 12 generates a low-level first switch control signal or does not generate a switch control signal according to the input voltage detection signal, so that the first DC power remains in a disconnected state; when the current regulation circuit 14 adjusts the rectified voltage signal to a very small value (close to zero), the AC rectifier circuit 15 can be regarded as an open circuit, and at this time, the subsequent power correction circuit 16 and the inverter rectifier circuit 17 will not be damaged by the overvoltage of the input voltage signal, thereby achieving hardware overvoltage protection.

[0058] In one embodiment, see Figure 6 The reverse connection prevention unit 131 includes a diode D7, wherein the anode of the diode D7 is connected to the positive output terminal of the input power supply 01, and the cathode of the diode D7 is connected to the overvoltage detection unit 132. The diode D7 has the characteristics of forward conduction and reverse cutoff, which can ensure the single-phase conduction of the input current and prevent the current backflow and the reverse connection of the input power supply 01 from damaging the components in the circuit.

[0059] In one embodiment, see Figure 6The overvoltage detection unit 132 includes: a varistor RV1; wherein the first end of the varistor RV1 is connected to the anti-reverse connection unit 131, specifically: the first end of the varistor RV1 is connected to the cathode of the diode D7, and the second end of the varistor RV1 is connected to the isolation switch unit 133. The varistor RV1 has a nonlinear volt-ampere characteristic, and the voltage threshold of the varistor RV1 is a first voltage threshold. When the voltage applied to the varistor RV1 is lower than its voltage threshold, the varistor RV1 is equivalent to a switch in an open state. When the input voltage signal exceeds its voltage threshold (i.e., overvoltage), it is equivalent to a switch in a closed state, thereby conducting the input voltage signal to the isolation switch unit 133.

[0060] In one embodiment, see Figure 6 The isolation switch unit 133 includes: a first photocoupler U1, a first capacitor C3, a second capacitor C4, a first resistor R3, a second resistor R4, a third resistor R5, a fourth resistor R6, a first diode D6, a second diode D8, a first transistor Q1, a second transistor Q2 and a first relay RLY1; wherein, a first end of the first capacitor C3, a cathode of the first diode D6 and an anode end of the first photocoupler U1 are connected to the overvoltage detection unit 132, a second end of the first capacitor C3, an anode of the first diode D6 and a cathode end of the first photocoupler U1 are connected to a first end of the first resistor R3, a second end of the first resistor R3 is connected to a first end of the second resistor R4, a second end of the second resistor R4 is connected to a current regulating circuit 14, an emitter end of the first photocoupler U1 is connected to a power supply ground, and a collector end of the first photocoupler U1 is connected to a collector end of the third resistor R5. The first end is connected to the base of the first transistor Q1, the second end of the third resistor R5, the first end of the fourth resistor R6 and the first end of the second capacitor C4 are commonly connected to the power correction circuit 16, the second end of the fourth resistor R6 and the second end of the second capacitor C4 are connected to the power ground, the emitter of the first transistor Q1 is connected to the base of the second transistor Q2, the collector of the first transistor Q1 is connected to the first end of the relay coil RLY1A of the first relay RLY1, the anode of the second diode D8 and the collector of the second transistor Q2, the emitter of the second transistor Q2 is connected to the power ground, the second end of the relay coil RLY1A and the cathode of the second diode D8 are commonly connected to the first DC terminal, the first end of the relay normally-open switch RLY1B of the first relay RLY1 is connected to the second end of the second resistor R4, and the second end of the relay normally-open switch RLY1B is connected to the AC rectifier circuit 15.

[0061] In a specific implementation, the first DC terminal outputs a first DC power, and the voltage of the first DC power can be +24V. The first end of the first capacitor C3, the cathode of the first diode D6, and the anode end of the first photoelectric coupler U1 are connected to the second end of the varistor RV1. Among them, the first diode D6 and the second diode D8 can perform reverse connection protection on the first photoelectric coupler U1, the first resistor R3 and the second resistor R4 are current limiting resistors, which can perform current limiting protection on the first photoelectric coupler U1 and the current regulating circuit 14, etc., and the first capacitor C3 performs filtering and noise reduction processing on the input voltage signal to improve the stability of the circuit. The first relay RLY1 is a medium for controlling slow start, and the first transistor Q1 and the second transistor Q2 constitute a Darlington transistor to enhance the switch control signal to enhance the driving ability of the first relay RLY1. The third resistor R5, as a resistor for driving the first transistor Q1 and the second transistor Q2, also has a voltage-dividing current-limiting protection function. The fourth resistor R6 and the second capacitor C4 together form an RC filter circuit, which performs filtering and noise reduction processing on the switch control signal to prevent the transistors (i.e., the first transistor Q1 and the second transistor Q2) from malfunctioning, so as to improve the control accuracy of the overvoltage protection. The first photocoupler U1 and the first relay RLY1 play the role of photoelectric isolation as well as the role of hardware overvoltage control and overvoltage protection.

[0062] In one embodiment, see Figure 6 The AC rectifier circuit 15 includes a rectifier bridge BR1 and a rectifier bridge BR2 to rectify the input voltage signal to generate a rectified voltage signal.

[0063] In one embodiment, the current regulating circuit 14 includes: at least one thermistor; wherein a first end of the at least one thermistor is connected to the overvoltage protection circuit 13 and the input power supply 01, and a second end of the at least one thermistor is connected to the overvoltage protection circuit 13 and the AC rectification circuit 13.

[0064] For example, see Figure 6 The current regulating circuit 14 includes three parallel thermistors, namely thermistor RT1, thermistor RT2 and thermistor RT3. The first end of thermistor RT1, the first end of thermistor RT2 and the first end of thermistor RT3 are connected to the second end of the second resistor R4, the first end of the relay normally open switch RLY1B and the negative output end of the input power supply 01. The second end of thermistor RT1, the second end of thermistor RT2 and the second end of thermistor RT3 are connected to the second end of the relay normally open switch RLY1B and the negative input end of the AC rectifier circuit 15. The three parallel thermistors can reduce the heat generated by the circuit and limit the surge current, thereby adjusting the current corresponding to the input voltage signal and adjusting the current corresponding to the rectified voltage signal.

[0065] See also Figure 5 In one embodiment, the power correction circuit includes: a driving switch unit 161, a correction control unit 162 and a power correction unit 163.

[0066] The driving switch unit 161 is connected to the control circuit 12 and is configured to control the on and off states of the second direct current according to the correction enable signal; the correction control unit 162 is connected to the driving switch unit 161 and is configured to generate a correction control signal according to the second direct current; the power correction unit 163 is connected to the AC rectifier circuit 15, the correction control unit 162 and the inverter rectifier circuit 17, and is configured to perform power factor correction on the rectified voltage signal according to the correction control signal to generate a correction voltage signal.

[0067] In a specific implementation, the control circuit 12 generates and outputs a first switch control signal, a first correction enable signal, and a first inverter enable signal based on the input voltage detection signal being less than the second voltage threshold; the control circuit 12 generates and outputs a second switch control signal, a second correction enable signal, and a second inverter control signal based on the input voltage detection signal being greater than or equal to the second voltage threshold (i.e., overvoltage). The driving switch unit 161 controls the power supply of the correction control unit 162 connected to the second DC power according to the first correction enable signal, so that the correction control unit 162 generates a correction control signal according to the connected second DC power to control the power correction unit 163 to perform power factor correction and other processing on the rectified voltage signal to generate a correction voltage signal and output it to the inverter rectifier circuit 17. The inverter rectifier circuit 17 inverts and rectifies the correction voltage signal according to the first inverter enable signal to generate a driving voltage signal; the driving switch unit 161 disconnects the power supply of the second DC power to the correction control unit 162 according to the second correction enable signal, so that the correction control unit 162 does not generate a correction control signal, the power correction unit 163 does not perform power factor correction and other processing on the rectified voltage signal, stops generating the correction voltage signal, and the inverter rectifier circuit 17 stops outputting the driving voltage signal according to the second inverter enable signal.

[0068] In a specific implementation, the control circuit 12 can also stop generating the second inverter control signal according to the input voltage detection signal being greater than or equal to the second voltage threshold, thereby controlling the inverter rectifier circuit 17 to stop inverting and rectifying the correction voltage signal, and stop generating and outputting the drive voltage signal.

[0069] See also Figure 6In one embodiment, the driving switch unit 161 includes: a fifth resistor R7, a sixth resistor R8, a seventh resistor R9, a third diode D9, a first field effect transistor VT1, a third triode Q3 and a second photocoupler U2; wherein the anode of the third diode D9 is connected to the second DC terminal, the cathode of the third diode D9 is connected to the drain of the first field effect transistor VT1, the source of the first field effect transistor VT1 and the first end of the fifth resistor R7 are connected to the power correction circuit 16, and the gate of the first field effect transistor VT1 is connected to the seventh resistor The first end of R9 is connected, the second end of the seventh resistor R9 and the second end of the fifth resistor R7 are connected to the collector end of the second photocoupler U2, the emitter end of the second photocoupler U2 is connected to the power ground, the anode end of the second photocoupler U2 is connected to the second end of the sixth resistor R8, the first end of the sixth resistor R8 is connected to the first DC power end, the cathode end of the second photocoupler U2 is connected to the collector of the third transistor Q3, the emitter of the third transistor Q3 is connected to the power ground, and the base of the third transistor Q3 is connected to the control circuit 12.

[0070] In a specific implementation, the second DC terminal outputs the second DC, and the voltage of the second DC is +15V. The anode of the third diode D9 is connected to the second DC, and can rectify the second DC and output it. The source of the first field effect transistor VT1 and the first end of the fifth resistor R7 are connected to the correction control unit 162, and the rectified second DC is output from the source of the first field effect transistor VT1 to power the correction control unit 162. The base of the third transistor Q3 is connected in series with the resistor R01 and then connected to the control circuit 12, and the base of the third transistor Q3 is connected to the first end of the resistor R01 and the first end of the resistor R02, the second end of the resistor R01 is connected to the control circuit 12, and the second end of the resistor R02 is connected to the power supply ground. The third transistor Q3 can be protected by voltage division and current limiting through the resistor R01 and the resistor R02.

[0071] In one embodiment, the correction control unit 162 includes a PFC control chip, such as ICE3PCS03G, which can generate a correction control signal under the power supply of the second direct current, and control the power correction unit 163 to perform power factor correction and other processing on the rectified voltage signal through the correction control signal to generate a correction voltage signal.

[0072] In one embodiment, see Figure 6The power correction unit 163 includes: a first inductor L1, a boost diode D2, a resistor R1, a resistor R2, and a first IGBT tube G3 and a second IGBT tube G4; wherein the first IGBT tube G3 and the second IGBT tube G4 serve as power correction switch tubes, and the control end of the first IGBT tube G3 and the control end of the second IGBT tube G4 are connected to the power correction control unit 162, and the rectified voltage signal after passing through the first inductor L1 is subjected to power factor correction and other processing according to the correction control signal to generate an original correction voltage signal, and the original correction voltage signal is boosted by the boost diode D2 to generate a correction voltage signal and output to the inverter rectifier circuit 17.

[0073] Optionally, the boost diode D2 may be replaced by a boost diode group formed by connecting a plurality of diodes in parallel.

[0074] See also Figure 6 In one embodiment, the input voltage detection circuit 11 includes: a fourth diode D10, a fifth diode D11, an eighth resistor R10 and a ninth resistor R11; wherein, the anode of the fourth diode D10 and the cathode of the fifth diode D11 are commonly connected to the auxiliary power supply circuit 19, the cathode of the fourth diode D10 is connected to the first end of the eighth resistor R10, the second end of the eighth resistor R10 and the first end of the ninth resistor R11 are commonly connected to the control circuit 12, and the second end of the ninth resistor R11 is connected to the power ground.

[0075] In a specific implementation, the anode of the fourth diode D10 and the cathode of the fifth diode D11 together constitute the feedback voltage signal input terminal of the input voltage detection circuit 11, the fourth diode D10 and the fifth diode D11 rectify the feedback voltage signal to generate rectified positive and negative voltages, the eighth resistor R10 and the ninth resistor R11 limit the current and divide the voltage of the rectified positive voltage to generate an input voltage detection signal, and ensure that the input voltage detection signal is within the allowable voltage range of the control circuit 12.

[0076] See also Figure 6 In one embodiment, the inverter rectifier circuit 17 includes a filter energy storage capacitor C1, an inverter IGBT tube (such as IGBT tube G1, IGBT tube G2, IGBT tube G5 and IGBT tube G6), a transformer T1 and a rectifier diode D4 and a rectifier diode D6. The connection relationship between the components can be seen in Figure 6 ; The filter energy storage capacitor C1 is an electrolytic capacitor with a large capacitance. In a specific implementation, the control circuit 12 can send the inverter control signal to the control end of each inverter IGBT tube through a bus communication method, such as an I2C bus, so as to control the inverter IGBT tube to perform inversion processing on the correction voltage signal.

[0077] In one embodiment, the control circuit 12 may be a single-chip microcomputer or a PLC programmable controller, etc., which can calculate, analyze, compare and judge the input voltage detection signal, and generate a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal and other control signals, so as to perform relevant control on the normal working state, overvoltage abnormal state, etc., and at the same time display control of abnormal states such as overvoltage to give an alarm prompt.

[0078] The following will be combined Figure 6 A brief description of the working principle of the inverter welding machine protection circuit:

[0079] During startup, since the relay coil RLY1A of the first relay RLY1 is not energized, the normally open switch RLY1B of the relay is in the off state, so that the current corresponding to the input voltage signal first flows through the thermistors (RT1, RT2, RT3) in the current regulation circuit 14, and the input current is limited by the thermistors to suppress surge current, thereby reducing the current flowing through the rectifier bridges BR1 and BR2, and correspondingly reducing the current flowing through the first inductor L1, the boost diode D1, and the power correction switch tube (i.e., the first IGBT tube G3 and the second IGBT tube G4), thereby protecting the components in the AC rectifier circuit 15, the power correction unit 163, and the inverter rectifier circuit 17 from being damaged by overcurrent or surge current.

[0080] When the startup process is completed, the single-chip microcomputer outputs a first switch control signal to control the first transistor Q1 and the second transistor Q2 to be turned on, and the relay coil RLY1A of the first relay RLY1 conducts the first direct current, so that the relay normally open switch RLY1B is closed, thereby short-circuiting the thermistors (RT1, RT2, RT3) and entering a normal working state. During the normal working process after startup, the single-chip microcomputer generates a first switch control signal, a first correction enable signal, and a first inverter enable signal according to the input voltage detection signal being less than the second voltage threshold (that is, not over-voltage); the first switch control signal is used to control the relay coil RLY1A to be energized (that is, conduct the first direct current) so that the relay normally open switch RLY1B is closed, thereby short-circuiting the thermistors (RT1, RT2, RT3); the first correction enable signal enables the third transistor Q3 to be turned on, thereby driving the first field effect transistor VT1 to conduct the second direct current (+15V) to the correction control unit 162 through the second photocoupler U2, so as to power the correction control unit 162 (such as the PFC control chip), and the correction control unit 162 generates a first correction enable signal according to the first correction enable signal. The power supply of the second direct current generates a power correction control signal to control the power correction switch tube (i.e., the first IGBT tube G3 and the second IGBT tube G4) to perform power factor correction and other processing on the rectified voltage signal after passing through the first inductor L1 to generate an original correction voltage signal, and the original correction voltage signal is boosted by the boost diode D2 to generate a correction voltage signal; the first inverter enable signal is used to control the inverter IGBT tube (i.e., IGBT tube G1, IGBT tube G2, IGBT tube G5 and IGBT tube G6) to invert the correction voltage signal to generate an inverter voltage signal, and the inverter voltage signal is transformed by the transformer T1, and then rectified by the rectifier diode D4 and the rectifier diode D6 to output a drive voltage signal.

[0081] During normal operation after startup, when the input voltage signal is greater than the first voltage threshold, that is, overvoltage, the varistor RV1 is turned on, and at this time, the primary light emitting diode of the first photocoupler U1 is turned on, and the first protection signal is output from the collector end of the first photocoupler U1. The first protection signal quickly pulls down the base level of the first transistor Q1, so that the first transistor Q1 and the second transistor Q2 are turned off, thereby quickly disconnecting the connection between the first direct current and the power ground, so that the relay coil RLY1A of the first relay RLY1 is powered off, the relay normally open switch RLY1B is disconnected, and the input voltage is The current corresponding to the voltage signal flows through the thermistor (RT1, RT2, RT3). Since the resistance of the thermistor increases with the temperature, the charging speed will be greatly slowed down by the thermistor. When the resistance of the thermistor reaches the 100M level, the transformer rectifier circuit 15 can be regarded as an open circuit. At this time, the subsequent circuits (such as the power correction circuit 16 and the inverter rectifier circuit 17, etc.) will not be damaged, and hardware overvoltage protection is achieved; at the same time, the control circuit 12 generates and outputs a second switch control when the input voltage detection signal is greater than or equal to the second voltage threshold and determines that the input voltage signal is too large (i.e., overvoltage). signal, a second correction enable signal and a second inversion control signal; the second switch control signal pulls down the base level of the first transistor Q1, controls the relay coil RLY1A to lose power so that the relay normally open switch RLY1B is disconnected, so that the current corresponding to the input voltage signal flows through the thermistor (RT1, RT2, RT3), and the current is limited by the thermistor, thereby adjusting the current corresponding to the rectified voltage signal; the second correction enable signal enables the third transistor Q3 to be turned off, thereby turning off the first field effect transistor VT1 through the second photocoupler U2, disconnecting the third transistor Q3. The second direct current (+15V) supplies power to the correction control unit 162 (such as a PFC control chip). After power failure, the correction control unit 162 stops generating power correction control signals and stops performing power factor correction and other processing on the rectified voltage signal after passing through the first inductor L1, thereby stopping generating correction voltage signals; the second inverter control signal controls the inverter IGBT tubes (i.e., IGBT tubes G1, G2, G5, and G6) to stop inverting the correction voltage signal and stop outputting the drive voltage signal, thereby realizing software-controlled overvoltage protection.

[0082] A second aspect of the present application provides an electric welder, the electric welder comprising the inverter welding machine protection circuit as described in any one of the above items.

[0083] In a specific implementation, the electric welder may be an inverter electric welder, which can process the input mains electricity to generate low-voltage, high-current direct current, and then load it onto the welded equipment for welding.

[0084] The embodiments of the present application can protect against power-on surges to prevent damage to circuit components due to power-on surges, effectively avoiding circuit damage caused by improper power-on timing or untimely control, and can also achieve dual overvoltage protection in hardware and software without the need for protection diodes, thereby improving the stability and safety reliability of overvoltage protection.

[0085] Those skilled in the art can clearly understand that for the convenience and simplicity of description, only the division of the above-mentioned functional units, modules, and circuits is used as an example. In actual applications, the above-mentioned function distribution can be completed by different functional units, modules, and circuits as needed, that is, the internal structure of the device can be divided into different functional units or modules or circuits to complete all or part of the functions described above. The functional units, modules, and circuits in the embodiments can be integrated into a processing unit, or each unit can exist physically alone, or two or more units can be integrated into one unit. The above-mentioned integrated unit can be implemented in the form of hardware or in the form of software functional units. In addition, the specific names of the functional units, modules, and circuits are only for the convenience of distinguishing from each other, and are not used to limit the scope of protection of this application. In the above embodiments, the description of each embodiment has its own emphasis. For the part that is not described or recorded in detail in a certain embodiment, refer to the relevant description of other embodiments. Another point is that the coupling or direct coupling or communication connection between each other shown or discussed can be through some interfaces, indirect coupling or communication connection of devices or units, which can be electrical, mechanical or other forms.

[0086] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. An inverter welding machine protection circuit, connected to an input power supply, characterized in that: The inverter welding machine protection circuit comprises: an AC rectifier circuit, connected to the input power supply and configured to rectify an input voltage signal provided by the input power supply to generate a rectified voltage signal; an input voltage detection circuit, connected to the input power supply and configured to detect the input voltage signal to generate an input voltage detection signal; a control circuit connected to the input voltage detection circuit and configured to generate a switch control signal, a correction enable signal and an inverter control signal according to the input voltage detection signal; an overvoltage protection circuit, connected to the input power supply, the control circuit and the AC rectifier circuit, configured to detect the input voltage signal, and generate a first protection signal to disconnect the first DC power when the input voltage signal is greater than a first voltage threshold, and control the on / off state of the first DC power according to the switch control signal; a current regulating circuit connected to the input power supply, the overvoltage protection circuit and the AC rectifying circuit, and configured to regulate a current corresponding to the rectified voltage signal according to a disconnection state of the first direct current; a power correction circuit connected to the AC rectification circuit and the control circuit, and configured to perform power factor correction on the rectified voltage signal according to the correction enable signal and the second DC power to generate a correction voltage signal; an inverter rectifier circuit connected to the control circuit and the power correction circuit, and configured to perform inversion and rectification processing on the correction voltage signal according to the inverter control signal to generate a drive voltage signal; an auxiliary power supply circuit, connected to the input power supply, the input voltage detection circuit, the overvoltage protection circuit and the power correction circuit, and configured to generate a feedback voltage signal, the first direct current and the second direct current according to the input voltage signal; the input voltage detection circuit is further configured to detect the feedback voltage signal to generate the input voltage detection signal; The overvoltage protection circuit comprises: an anti-reverse connection unit, connected to the input power supply and the AC rectifier circuit, and configured to prevent the input voltage signal from being reversely connected; an overvoltage detection unit, connected to the anti-reverse connection unit, configured to detect the input voltage signal and conduct the input voltage signal when the input voltage signal is greater than the first voltage threshold; The isolating switch unit is connected to the overvoltage detection unit, the input power supply, the current regulating circuit, the control circuit and the AC rectifying circuit, and is configured to generate the first protection signal according to the input voltage signal to disconnect the first DC power.

2. The inverter welding machine protection circuit according to claim 1, characterized in that: The control circuit is further configured to generate an alarm prompt signal according to the input voltage detection signal, and the inverter welding machine protection circuit also includes: The display alarm circuit is connected to the control circuit and is configured to display an alarm prompt according to the alarm prompt signal.

3. The inverter welding machine protection circuit according to claim 1, characterized in that: The power correction circuit comprises: a driving switch unit, connected to the control circuit, and configured to control the on and off state of the second direct current according to the correction enable signal; a correction control unit, connected to the driving switch unit and configured to generate a correction control signal according to the second direct current; The power correction unit is connected to the AC rectifier circuit, the correction control unit and the inverter rectifier circuit, and is configured to perform power factor correction on the rectified voltage signal according to the correction control signal to generate a correction voltage signal.

4. The inverter welding machine protection circuit according to claim 1, characterized in that: The current regulating circuit includes: at least one thermistor; wherein a first end of the at least one thermistor is connected to the overvoltage protection circuit and the input power supply, and a second end of the at least one thermistor is connected to the overvoltage protection circuit and the AC rectifier circuit.

5. The inverter welding machine protection circuit according to claim 1, characterized in that: The isolation switch unit includes: a first photoelectric coupler, a first capacitor, a second capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a first diode, a second diode, a first transistor, a second transistor and a first relay; wherein the first end of the first capacitor, the cathode of the first diode and the anode end of the first photoelectric coupler are connected to the overvoltage detection unit, the second end of the first capacitor, the anode of the first diode and the cathode end of the first photoelectric coupler are connected to the first end of the first resistor, the second end of the first resistor is connected to the first end of the second resistor, the second end of the second resistor is connected to the current regulating circuit, the emitter end of the first photoelectric coupler is connected to the power supply ground, and the collector end of the first photoelectric coupler is connected to the first end and The base of the first transistor is connected, the second end of the third resistor, the first end of the fourth resistor and the first end of the second capacitor are commonly connected to the power correction circuit, the second end of the fourth resistor and the second end of the second capacitor are connected to the power ground, the emitter of the first transistor is connected to the base of the second transistor, the collector of the first transistor is connected to the first end of the relay coil of the first relay, the anode of the second diode and the collector of the second transistor, the emitter of the second transistor is connected to the power ground, the second end of the relay coil and the cathode of the second diode are commonly connected to the first DC terminal, the first end of the relay normally-open switch of the first relay is connected to the second end of the second resistor, and the second end of the relay normally-open switch is connected to the AC rectifier circuit.

6. The inverter welding machine protection circuit according to claim 3, characterized in that: The driving switch unit includes: a fifth resistor, a sixth resistor, a seventh resistor, a third diode, a first field effect transistor, a third triode and a second photoelectric coupler; wherein, the anode of the third diode is connected to the second DC terminal, the cathode of the third diode is connected to the drain of the first field effect transistor, the source of the first field effect transistor and the first end of the fifth resistor are commonly connected to the power correction circuit, the gate of the first field effect transistor is connected to the first end of the seventh resistor, the second end of the seventh resistor and the second end of the fifth resistor are connected to the collector end of the second photoelectric coupler, the emitter end of the second photoelectric coupler is connected to the power ground, the anode end of the second photoelectric coupler is connected to the second end of the sixth resistor, the first end of the sixth resistor is connected to the first DC terminal, the cathode end of the second photoelectric coupler is connected to the collector of the third triode, the emitter of the third triode is connected to the power ground, and the base of the third triode is connected to the control circuit.

7. The inverter welding machine protection circuit according to claim 1, characterized in that: The input voltage detection circuit includes: a fourth diode, a fifth diode, an eighth resistor and a ninth resistor; wherein, the anode of the fourth diode and the cathode of the fifth diode are commonly connected to the auxiliary power supply circuit, the cathode of the fourth diode is connected to the first end of the eighth resistor, the second end of the eighth resistor and the first end of the ninth resistor are commonly connected to the control circuit, and the second end of the ninth resistor is connected to the power ground.

8. An electric welding machine, characterized in that: The electric welding machine comprises the inverter welding machine protection circuit as claimed in any one of claims 1 to 7.

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