Controllable soft start circuit of electric welding machine

Abstract

The utility model discloses a controllable soft start circuit of an electric welding machine. The controllable soft start circuit comprises a rectifier bridge, a PTC (Positive Temperature Coefficient) resistor, a filter circuit, a relay and an active control circuit, a pin 1 of the rectifier bridge is connected with an external live wire, and a pin 3 of the rectifier bridge is connected with an external zero wire; one end of the PTC resistor is connected with a pin 4 of the rectifier bridge; the filter circuit is connected with the other end of the PTC resistor and a pin 2 of the rectifier bridge and is used for filtering; the relay is connected with the PTC resistor and external 24V voltage; the active control circuit is connected with the relay and used for controlling the working state of the relay. According to the controllable soft start circuit of the electric welding machine, due to the fact that the network voltage of an alternating-current power grid is sine waves and the frequency is 50 Hz, a network voltage zero crossing point can be formed every 20 ms, on the basis of an original circuit, a relay is controlled to be opened at the zero crossing point of the alternating-current power grid, at the moment, the relay can be effectively protected, and the service life is prolonged.

Description

Technical Field

[0001] This utility model relates to the technical field of starting circuits for electric welding machines, and in particular to a controllable soft-start circuit for an electric welding machine. Background Technology

[0002] Because welding machines are high-power power supply products, a large electrolytic capacitor is required at the front end of the inverter bridge for the welding machine to function properly. The introduction of a large electrolytic capacitor can cause excessive charging current at startup, leading to fuse burnout or circuit breaker tripping. To solve this problem, the industry generally introduces a soft-start circuit. This circuit uses a PTC resistor to charge the electrolytic capacitor first, and then a relay short-circuits the PTC resistor after a period of time.

[0003] The advantage of this approach is its low cost and simple circuitry. However, for some high-end machines or applications with high lifespan requirements, since current already exists in the circuit when the relay is working, an electric arc will occur during startup. Over time, this will affect the lifespan of the relay. If the relay fails, the entire machine will become unusable, thus impacting the overall lifespan of the machine. Summary of the Invention

[0004] According to an embodiment of the present invention, a controllable soft-start circuit for an electric welding machine is provided, comprising: a rectifier bridge, a PTC resistor, a filter circuit, a relay, and an active control circuit;

[0005] Pin 1 of the rectifier bridge is connected to the external live wire, and pin 3 of the rectifier bridge is connected to the external neutral wire.

[0006] One end of the PTC resistor is connected to pin 4 of the rectifier bridge;

[0007] The filter circuit is connected to the other end of the PTC resistor and pin 2 of the rectifier bridge for filtering.

[0008] The relay is connected to a PTC resistor and an external 24V voltage.

[0009] The active control circuit is connected to the relay and is used to control the operating state of the relay.

[0010] Furthermore, the filter circuit includes: a first capacitor, a second capacitor, and a third capacitor;

[0011] One end of the first capacitor is connected to the other end of the PTC resistor, and the other end of the first capacitor is connected to pin 2 of the rectifier bridge.

[0012] The first capacitor, the second capacitor, and the third capacitor are connected in parallel.

[0013] Furthermore, the active control circuit includes: a rectifier circuit, a voltage divider circuit, a first Zener diode, a third resistor, a fourth resistor, a transistor, a first optocoupler, a second optocoupler, a second Zener diode, a fifth resistor, a sixth resistor, a fourth capacitor, a seventh resistor, and a thyristor.

[0014] The rectifier circuit is connected to the external live wire and neutral wire to rectify AC power into DC power.

[0015] The voltage divider circuit is connected to the rectifier circuit;

[0016] The cathode of the first Zener diode is connected to the voltage divider circuit, and the anode of the first Zener diode is connected to the base of the transistor.

[0017] One end of the third resistor is connected to the rectifier circuit, and the other end is connected to pin 4 of the first optocoupler and the collector of the transistor.

[0018] One end of the fourth resistor is connected between the anode of the first Zener diode and the base of the transistor, and the other end is connected to the rectifier circuit, the emitter of the transistor, and pin 2 of the second optocoupler.

[0019] Pin 1 of the first optocoupler is connected to the anode of the second Zener diode, and pin 3 of the first optocoupler is connected to pin 1 of the second optocoupler.

[0020] Pin 4 of the second optocoupler is connected to an external 24V voltage through a sixth resistor, and pin 3 of the second optocoupler is connected to the gate of the thyristor through a seventh resistor.

[0021] The cathode of the second Zener diode is connected to one end of the fifth resistor and one end of the fourth capacitor;

[0022] The other end of the fifth resistor is connected to an external 24V voltage;

[0023] The other end of the fourth capacitor, pin 2 of the first optocoupler, is grounded;

[0024] The anode of the thyristor is connected to the relay, and the cathode of the thyristor is grounded.

[0025] Furthermore, the rectifier circuit includes: a first diode, a second diode, a third diode, and a fourth diode;

[0026] After the cathodes of the first diode and the second diode are connected together, they are connected to the voltage divider circuit and one end of the third resistor;

[0027] After the anodes of the third and fourth diodes are connected, they are connected to the voltage divider circuit, the other end of the fourth resistor, the emitter of the transistor, and pin 2 of the second optocoupler.

[0028] The anode of the first diode and the cathode of the third diode are connected to the external live wire, while the anode of the second diode and the cathode of the fourth diode are connected to the external neutral wire.

[0029] Furthermore, the voltage divider circuit includes: a first resistor and a second resistor;

[0030] One end of the first resistor is connected to the rectifier circuit, and the other end of the first resistor is connected to one end of the second resistor and the cathode of the first Zener diode.

[0031] The other end of the second resistor is connected to the rectifier circuit.

[0032] Furthermore, it also includes: a fifth diode, the anode of which is connected to the active control circuit, and the cathode of which is connected to the relay and the external 24V voltage.

[0033] According to an embodiment of the present invention, a controllable soft-start circuit for a welding machine is provided. Since the AC mains voltage is a sine wave with a frequency of 50Hz, the mains voltage will cross zero once every 20ms. Based on the original circuit, we control the relay to open when the AC mains voltage crosses zero, which can effectively protect the relay and improve its service life.

[0034] It should be understood that both the foregoing general description and the following detailed description are exemplary and intended to provide further illustration of the claimed technology. Attached Figure Description

[0035] Figure 1 This is a circuit diagram of a controllable soft-start circuit for a welding machine according to an embodiment of the present invention. Detailed Implementation

[0036] The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings, further illustrating the present invention.

[0037] First, combine Figure 1 This invention describes a controllable soft-start circuit for a welding machine according to an embodiment of the present invention, which is used in welding machines and has a wide range of applications.

[0038] like Figure 1 As shown, a controllable soft-start circuit for a welding machine according to an embodiment of the present invention includes a rectifier bridge, a PTC resistor RT1, a filter circuit, a relay J1, and an active control circuit.

[0039] Specifically, such as Figure 1 As shown, pin 1 of the rectifier bridge is connected to the external live wire L, and pin 3 of the rectifier bridge is connected to the external neutral wire N. The alternating current from the live wire L and the neutral wire N is converted into direct current to provide DC power for the subsequent circuit components, enabling the circuit to work in a DC environment and meet the basic requirements of some electronic devices (such as electronic modules that require DC power).

[0040] Specifically, such as Figure 1 As shown, one end of the PTC resistor RT1 is connected to pin 4 of the rectifier bridge. When the circuit starts up, the PTC resistor can slowly increase its resistance value, so that the current in the circuit gradually increases, avoiding the impact of excessive current on the circuit components at the moment of startup, thus achieving soft start.

[0041] Specifically, such as Figure 1 As shown, the filter circuit is connected to the other end of the PTC resistor RT1 and pin 2 of the rectifier bridge for filtering. The filter circuit includes: a first capacitor C1, a second capacitor C2, and a third capacitor C3; one end of the first capacitor C1 is connected to the other end of the PTC resistor RT1, and the other end of the first capacitor C1 is connected to pin 2 of the rectifier bridge; the first capacitor C1, the second capacitor C2, and the third capacitor C3 are connected in parallel.

[0042] Specifically, such as Figure 1 As shown, relay J1 is connected to PTC resistor RT1 and external 24V voltage.

[0043] Specifically, such as Figure 1 As shown, the active control circuit is connected to relay J1 and is used to control the working state of relay J1. The active control circuit includes: a rectifier circuit, a voltage divider circuit, a first Zener diode ZD1, a third resistor R3, a fourth resistor R4, a transistor Q1, a first optocoupler U1, a second optocoupler U2, a second Zener diode ZD2, a fifth resistor R5, a sixth resistor R6, a fourth capacitor C4, a seventh resistor R7, and a thyristor Q2. The rectifier circuit is connected to the external live wire L and neutral wire N to rectify AC power into DC power; the voltage divider circuit is connected to the rectifier circuit; the cathode of the first Zener diode ZD1 is connected to the voltage divider circuit, and the anode of the first Zener diode ZD1 is connected to the base of transistor Q1; one end of the third resistor R3 is connected to the rectifier circuit, and the other end is connected to pin 4 of the first optocoupler U1 and the collector of transistor Q1; one end of the fourth resistor R4 is connected between the anode of the first Zener diode ZD1 and the base of transistor Q1, and the other end is connected to the rectifier circuit, the emitter of transistor Q1, and pin 2 of the second optocoupler U2; pin 1 of the first optocoupler U1... The anode of the second Zener diode ZD2 is connected to the anode of the first optocoupler U1, and pin 3 of the first optocoupler U1 is connected to pin 1 of the second optocoupler U2. Pin 4 of the second optocoupler U2 is connected to the external 24V voltage through the sixth resistor R6, and pin 3 of the second optocoupler U2 is connected to the gate of the thyristor Q2 through the seventh resistor R7. The cathode of the second Zener diode ZD2 is connected to one end of the fifth resistor R5 and one end of the fourth capacitor C4. The other end of the fifth resistor R5 is connected to the external 24V voltage. The other end of the fourth capacitor C4 and pin 2 of the first optocoupler U1 are grounded. The anode of the thyristor Q2 is connected to the relay J1, and the cathode of the thyristor Q2 is grounded.

[0044] Furthermore, such as Figure 1As shown, the rectifier circuit includes: a first diode D1, a second diode D2, a third diode D3, and a fourth diode D4; the cathodes of the first diode D1 and the second diode D2 are connected together and then connected to a voltage divider circuit and one end of the third resistor R3; the anodes of the third diode D3 and the fourth diode D4 are connected together and then connected to the other end of the voltage divider circuit and the fourth resistor R4, the emitter of the transistor Q1, and pin 2 of the second optocoupler U2; the anode of the first diode D1 and the cathode of the third diode D3 are connected to the external live wire L, and the anode of the second diode D2 and the cathode of the fourth diode D4 are connected to the external neutral wire N.

[0045] Furthermore, such as Figure 1 As shown, the voltage divider circuit includes: a first resistor R1 and a second resistor R2; one end of the first resistor R1 is connected to the rectifier circuit, and the other end of the first resistor R1 is connected to one end of the second resistor R2 and the cathode of the first Zener diode ZD1; the other end of the second resistor R2 is connected to the rectifier circuit.

[0046] Furthermore, the controllable soft-start circuit of a welding machine according to an embodiment of the present invention also includes: a fifth diode D5, the anode of the fifth diode D5 is connected to the active control circuit, the cathode of the fifth diode D5 is connected to the relay J1 and the external 24V voltage, and the fifth diode D5 is used for freewheeling and overvoltage protection.

[0047] L and N are the live and neutral wires L that enter the machine. When the machine is turned on, the auxiliary switching power supply works and provides 24V voltage. At this time, the fourth capacitor C4 is charged through the fifth resistor R5. When the voltage exceeds the value of the second Zener diode ZD2, the first optocoupler U1 is turned on.

[0048] After passing through the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4, L and N are rectified into DC power. After being divided by the first resistor R1 and the second resistor R2, when the first optocoupler U1 is turned on, if the mains voltage is high at this time, the voltage division value exceeds the first Zener diode ZD1, and the transistor Q1 works.

[0049] When the voltage at pin 4 of the first optocoupler U1 is pulled down to 0V, the second optocoupler U2 is turned off. When the mains voltage drops low enough to not break down the first Zener diode ZD1, the transistor Q1 is turned off, and the DC voltage passes through the first resistor R1, causing the second optocoupler U2 to conduct.

[0050] At this time, the 24V voltage passes through the sixth resistor R6, pins 3 and 4 of the second optocoupler U2, and the seventh resistor R7, causing the thyristor Q2 to conduct and the relay J1 to enter the working state.

[0051] Above, refer to Figure 1This invention describes a controllable soft-start circuit for a welding machine according to an embodiment of the present invention. Since the AC mains voltage is a sine wave with a frequency of 50Hz, the mains voltage will cross zero once every 20ms. Based on the original circuit, we control the relay J1 to open when the AC mains voltage crosses zero, which can effectively protect the relay J1 and improve its service life.

[0052] It should be noted that, in this specification, the terms "comprising," "including," or any other variations thereof are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0053] Although the present invention has been described in detail through the above preferred embodiments, it should be understood that the above description should not be considered as a limitation of the present invention. Various modifications and substitutions to the present invention will be apparent to those skilled in the art after reading the above content. Therefore, the scope of protection of the present invention should be defined by the appended claims.

Claims

1. A controllable soft-start circuit for an electric welding machine, characterized in that, Includes: rectifier bridge, PTC resistor, filter circuit, relay, and active control circuit; Pin 1 of the rectifier bridge is connected to the external live wire, and pin 3 of the rectifier bridge is connected to the external neutral wire. One end of the PTC resistor is connected to pin 4 of the rectifier bridge; The filter circuit is connected to the other end of the PTC resistor and pin 2 of the rectifier bridge for filtering. The relay is connected to the PTC resistor and an external 24V voltage; The active control circuit is connected to the relay and is used to control the operating state of the relay.

2. The controllable soft-start circuit of the welding machine as described in claim 1, characterized in that, The filter circuit includes: a first capacitor, a second capacitor, and a third capacitor; One end of the first capacitor is connected to the other end of the PTC resistor, and the other end of the first capacitor is connected to pin 2 of the rectifier bridge. The first capacitor, the second capacitor, and the third capacitor are connected in parallel.

3. The controllable soft-start circuit of the welding machine as described in claim 1, characterized in that, The active control circuit includes: a rectifier circuit, a voltage divider circuit, a first Zener diode, a third resistor, a fourth resistor, a transistor, a first optocoupler, a second optocoupler, a second Zener diode, a fifth resistor, a sixth resistor, a fourth capacitor, a seventh resistor, and a thyristor. The rectifier circuit is connected to the external live wire and neutral wire to rectify AC power into DC power. The voltage divider circuit is connected to the rectifier circuit; The cathode of the first Zener diode is connected to the voltage divider circuit, and the anode of the first Zener diode is connected to the base of the transistor. One end of the third resistor is connected to the rectifier circuit, and the other end is connected to pin 4 of the first optocoupler and the collector of the transistor. One end of the fourth resistor is connected between the anode of the first Zener diode and the base of the transistor, and the other end is connected to the rectifier circuit, the emitter of the transistor, and pin 2 of the second optocoupler. Pin 1 of the first optocoupler is connected to the anode of the second Zener diode, and pin 3 of the first optocoupler is connected to pin 1 of the second optocoupler. Pin 4 of the second optocoupler is connected to an external 24V voltage through the sixth resistor, and pin 3 of the second optocoupler is connected to the gate of the thyristor through the seventh resistor. The cathode of the second Zener diode is connected to one end of the fifth resistor and one end of the fourth capacitor; The other end of the fifth resistor is connected to an external 24V voltage; The other end of the fourth capacitor and pin 2 of the first optocoupler are grounded; The anode of the thyristor is connected to the relay, and the cathode of the thyristor is grounded.

4. The controllable soft-start circuit of the welding machine as described in claim 3, characterized in that, The rectifier circuit includes: a first diode, a second diode, a third diode, and a fourth diode; After the cathodes of the first diode and the second diode are connected together, they are connected to one end of the voltage divider circuit and the third resistor; After the anodes of the third diode and the fourth diode are connected, they are connected to the voltage divider circuit, the other end of the fourth resistor, the emitter of the transistor, and pin 2 of the second optocoupler. The anode of the first diode and the cathode of the third diode are connected to an external live wire, and the anode of the second diode and the cathode of the fourth diode are connected to an external neutral wire.

5. The controllable soft-start circuit of the welding machine as described in claim 3, characterized in that, The voltage divider circuit includes: a first resistor and a second resistor; One end of the first resistor is connected to the rectifier circuit, and the other end of the first resistor is connected to one end of the second resistor and the cathode of the first Zener diode. The other end of the second resistor is connected to the rectifier circuit.

6. The controllable soft-start circuit of the welding machine as described in claim 1, characterized in that, It also includes: a fifth diode, the anode of which is connected to the active control circuit, and the cathode of which is connected to the relay and an external 24V voltage.

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