Controllable soft start circuit of electric welding machine

Abstract

The invention 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 generated every 20 ms, on the basis of an original circuit, a relay is controlled to be opened when the alternating-current power grid crosses the zero point, at the moment, the relay can be effectively protected, and the service life is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of starting circuits of electric welders, and in particular to a controllable soft starting circuit of an electric welder. Background Art

[0002] Since the welding machine is a high-power power supply product, a large electrolytic capacitor is required at the front end of the inverter bridge so that the welding machine can work properly. The introduction of a large electrolytic capacitor will cause excessive charging current at the moment of startup, causing the fuse to burn out or the air switch to trip. In order to solve this problem, the industry generally introduces a soft start circuit, which charges the electrolytic capacitor through a PTC resistor first, and then uses a relay to short-circuit the PTC resistor after a period of time.

[0003] The advantage of this approach is that it is low cost and simple circuit. However, for some high-end machines or scenarios with high life requirements, since there is already current in the circuit when the relay is working, there will be an arc at startup, which will affect the life of the relay over a long period of time. If the relay fails, the entire machine cannot be used, which in turn affects the life of the entire machine. Summary of the invention

[0004] According to an embodiment of the present invention, a controllable soft start circuit of an electric welding machine is provided, comprising: a rectifier bridge, a PTC resistor, a filter circuit, a relay and an 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 the pin 2 of the rectifier bridge for filtering; The relay is connected to the PTC resistor and the external 24V voltage; The active control circuit is connected to the relay and is used for controlling the working state of the relay.

[0005] Further, the filter circuit comprises: 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.

[0006] Further, the active control circuit includes: a rectifier circuit, a voltage divider circuit, a first voltage regulator tube, a third resistor, a fourth resistor, a triode, a first optocoupler, a second optocoupler, a second voltage regulator tube, 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 and is used to rectify the AC power into DC power; The voltage divider circuit is connected to the rectifier circuit; The cathode of the first voltage-stabilizing tube is connected to the voltage-dividing circuit, and the anode of the first voltage-stabilizing tube is connected to the base of the triode; One end of the third resistor is connected to the rectifier circuit, and the other end is connected to the pin 4 of the first optical coupler and the collector of the transistor; One end of the fourth resistor is connected between the anode of the first voltage regulator tube and the base of the transistor, and the other end is connected to the rectifier circuit, the emitter of the transistor, and the pin 2 of the second optical coupler; Pin 1 of the first optocoupler is connected to the anode of the second voltage regulator tube, 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 a sixth resistor, and pin 3 of the second optocoupler is connected to a gate of the thyristor through a seventh resistor; The cathode of the second voltage-stabilizing tube is connected to one end of the fifth resistor and one end of the fourth capacitor; The other end of the fifth capacitor is connected to an external 24V voltage; The other end of the fourth capacitor and the pin 2 of the first optical coupler are grounded; The anode of the thyristor is connected to the relay and the cathode of the thyristor is grounded.

[0007] Further, the rectifier circuit comprises: 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, they are connected to the voltage divider circuit and one end of 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 the pin 2 of the second optical coupler; The anode of the first diode and the cathode of the third diode are connected to the external live wire, and the anode of the second diode and the cathode of the fourth diode are connected to the external neutral wire.

[0008] Furthermore, 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 voltage regulator tube; The other end of the second resistor is connected to the rectifier circuit.

[0009] Furthermore, it also includes: a fifth diode, the anode of the fifth diode is connected to the active control circuit, and the cathode of the fifth diode is connected to the relay and the external 24V voltage.

[0010] According to a controllable soft-start circuit of an electric welding machine in an embodiment of the present invention, since the AC grid voltage is a sine wave with a frequency of 50 Hz, the grid voltage will pass through zero once every 20 ms. On the basis of the original circuit, we control the relay to open when the AC grid passes through zero, which can effectively protect the relay and improve its service life.

[0011] It is to be understood that both the foregoing general description and the following detailed description are exemplary, and are intended to provide further explanation of the technology as claimed. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The figure is a circuit diagram of a controllable soft start circuit of an electric welding machine according to an embodiment of the present invention. DETAILED DESCRIPTION

[0013] The preferred embodiments of the present invention will be described in detail below in conjunction with the accompanying drawings to further illustrate the present invention.

[0014] First, combine Figure 1 A controllable soft start circuit of an electric welding machine according to an embodiment of the present invention is described. The circuit is used in the electric welding machine and has a wide range of application scenarios.

[0015] like Figure 1 As shown, a controllable soft start circuit of an electric welding machine according to an embodiment of the present invention comprises a rectifier bridge, a PTC resistor RT1, a filter circuit, a relay J1 and an active control circuit.

[0016] Specifically, 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, converting the AC power from the live wire L and the neutral wire N into DC power, providing DC power for subsequent circuit elements, so that the circuit can work in a DC environment, meeting the basic requirements of some electronic equipment (such as electronic modules that require DC power supply, etc.).

[0017] Specifically, Figure 1 As shown, one end of the PTC resistor RT1 is connected to the pin 4 of the rectifier bridge. When the circuit starts, the PTC resistor can slowly increase the resistance value, so that the current in the circuit gradually increases, avoiding the impact of excessive current on circuit components at the moment of startup, and realizing soft start.

[0018] Specifically, Figure 1As shown, the filter circuit is connected to the other end of the PTC resistor RT1 and the 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 the pin 2 of the rectifier bridge; the first capacitor C1, the second capacitor C2 and the third capacitor C3 are connected in parallel.

[0019] Specifically, Figure 1 As shown, relay J1 is connected to PTC resistor RT1 and external 24V voltage.

[0020] Specifically, Figure 1 As shown, the active control circuit is connected to the relay J1 and is used to control the working state of the relay J1. The active control circuit includes: a rectifier circuit, a voltage divider circuit, a first voltage regulator ZD1, a third resistor R3, a fourth resistor R4, a transistor Q1, a first optical coupler U1, a second optical coupler U2, a second voltage regulator 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, and is used to rectify the alternating current into direct current; the voltage divider circuit is connected to the rectifier circuit; the cathode of the first voltage regulator tube ZD1 is connected to the voltage divider circuit, and the anode of the first voltage regulator tube ZD1 is connected to the base of the transistor Q1; one end of the third resistor R3 is connected to the rectifier circuit, and the other end is connected to the pin 4 of the first optical coupler U1 and the collector of the transistor Q1; one end of the fourth resistor R4 is connected between the anode of the first voltage regulator tube ZD1 and the base of the transistor Q1, and the other end is connected to the rectifier circuit, the emitter of the transistor Q1, and the pin 2 of the second optical coupler U2; the pin of the first optical coupler U1 1 is connected to the anode of the second voltage-stabilizing tube ZD2, and the pin 3 of the first optical coupler U1 is connected to the pin 1 of the second optical coupler U2; the pin 4 of the second optical coupler U2 is connected to the external 24V voltage through the sixth resistor R6, and the pin 3 of the second optical coupler U2 is connected to the gate of the thyristor Q2 through the seventh resistor R7; the cathode of the second voltage-stabilizing tube 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 capacitor is connected to the external 24V voltage; the other end of the fourth capacitor C4 and the pin 2 of the first optical coupler U1 are grounded; the anode of the thyristor Q2 is connected to the relay J1, and the cathode of the thyristor Q2 is grounded.

[0021] Further, if Figure 1As shown, the rectifier circuit includes: a first diode D1, a second diode D2, a third diode D3 and a fourth diode D4; after the cathodes of the first diode D1 and the second diode D2 are connected, they are connected to the voltage divider circuit and one end of the third resistor R3; after the anodes of the third diode D3 and the fourth diode D4 are connected, they are connected to the voltage divider circuit, the other end of the fourth resistor R4, the emitter of the transistor Q1, and the 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.

[0022] Further, if 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 voltage regulator ZD1; the other end of the second resistor R2 is connected to the rectifier circuit.

[0023] Furthermore, a controllable soft start circuit of an electric welding machine according to an embodiment of the present invention further comprises: a fifth diode D5, an anode of the fifth diode D5 is connected to the active control circuit, a cathode of the fifth diode D5 is connected to the relay J1 and an external 24V voltage, and the fifth diode D5 is used for freewheeling and overvoltage protection.

[0024] L and N are the neutral and live wires L entering the machine. When the machine is turned on, the attached switching power supply works and provides a 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 voltage regulator tube ZD2, the first optical coupler U1 is turned on; After L and N pass through the first diode D1, the second diode D2, the third diode D3, and the fourth diode D4, they are rectified into direct current, and then divided by the first resistor R1 and the second resistor R2. When the first optical coupler U1 is turned on, if the power grid is at a high voltage at this time, the divided voltage value exceeds the first voltage regulator ZD1, and the transistor Q1 works; The voltage at the 4th pin of the first optocoupler U1 is pulled to 0V, and the second optocoupler U2 is turned off at this time; when the grid voltage drops low enough to fail to break down the first voltage regulator ZD1, the transistor Q1 is turned off, and the DC voltage passes through the first resistor R1, and the first optocoupler U1 turns on the second optocoupler U2; At this time, the 24V voltage passes through the sixth resistor R6, the 3rd and 4th pins of the second optical coupler U2, and the seventh resistor R7, so that the thyristor Q2 is turned on and the relay J1 enters the working state.

[0025] Above, refer to Figure 1A controllable soft start circuit of an electric welding machine according to an embodiment of the present invention is described. Since the AC power grid voltage is a sine wave with a frequency of 50Hz, the grid voltage will pass through zero once every 20ms. On the basis of the original circuit, we control the relay J1 to open when the AC power grid passes through zero. At this time, the relay J1 can be effectively protected and the service life can be increased.

[0026] It should be noted that, in this specification, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprises..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0027] Although the content of the present invention has been described in detail through the above preferred embodiments, it should be appreciated that the above description should not be considered as a limitation of the present invention. After reading the above content, it will be apparent to those skilled in the art that various modifications and substitutions of the present invention will occur. Therefore, the protection scope of the present invention should be limited by the appended claims.

Claims

1. A controllable soft start circuit for an electric welding machine, characterized in that: Contains: rectifier bridge, PTC resistor, filter circuit, relay and active control circuit; Pin 1 of the rectifier bridge is connected to an external live wire, and pin 3 of the rectifier bridge is connected to an external neutral wire; One end of the PTC resistor is connected to pin 4 of the rectifier bridge; The filtering circuit is connected to the other end of the PTC resistor and the 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 working state of the relay; The active control circuit comprises: a rectifier circuit, a voltage divider circuit, a first voltage regulator tube, a third resistor, a fourth resistor, a triode, a first optocoupler, a second optocoupler, a second voltage regulator tube, a fifth resistor, a sixth resistor, a fourth capacitor, a seventh resistor and a thyristor; The rectifier circuit is connected to an external live wire and a neutral wire, and is used to rectify the alternating current into direct current; The voltage divider circuit is connected to the rectifier circuit; The cathode of the first voltage regulator tube is connected to the voltage divider circuit, and the anode of the first voltage regulator tube is connected to the base of the triode; One end of the third resistor is connected to the rectifier circuit, and the other end is connected to the pin 4 of the first optical coupler and the collector of the transistor; One end of the fourth resistor is connected between the anode of the first voltage regulator and the base of the transistor, and the other end is connected to the rectifier circuit, the emitter of the transistor, and the pin 2 of the second optical coupler; Pin 1 of the first optocoupler is connected to the anode of the second voltage regulator tube, and pin 3 of the first optocoupler is connected to pin 1 of the second optocoupler; The pin 4 of the second optical coupler is connected to the external 24V voltage through the sixth resistor, and the pin 3 of the second optical coupler is connected to the gate of the thyristor through the seventh resistor; The cathode of the second voltage regulator is connected to one end of the fifth resistor and one end of the fourth capacitor; The other end of the fifth capacitor is connected to an external 24V voltage; The other end of the fourth capacitor and the pin 2 of the first optical coupler are grounded; The anode of the thyristor is connected to the relay, and the cathode of the thyristor is grounded; The filter circuit comprises: 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.

2. The controllable soft start circuit of the electric welding machine as claimed in claim 1, characterized in that: The rectifier circuit comprises: 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, they are connected to a voltage divider circuit and one end of a 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 the pin 2 of the second optical coupler; 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.

3. The controllable soft start circuit of the electric welding machine as claimed in claim 1, characterized in that: The voltage divider circuit comprises: 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 voltage regulator tube; The other end of the second resistor is connected to the rectifier circuit.

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

Images