Pulse interface circuit and control method thereof

Abstract

The invention belongs to the technical field of interface control between a PLC (Programmable Logic Controller) and a welding power supply, and particularly discloses a pulse interface circuit between the PLC and a TIG (Tungsten Inert Gas) welding power supply and a control method thereof, and the pulse interface circuit comprises an analog quantity switch integrated circuit, a logic judgment circuit and a protection circuit. The pulse interface circuit is used between a PLC and a TIG welding power source and converts a pulse width modulation (PWM) signal and an analog quantity signal from the PLC into a pulse signal of the TIG welding power source so as to generate a pulse welding current with adjustable frequency, duty ratio, basic value point flow and peak current.

Description

Technical Field

[0001] The present invention relates to the technical field of interface control between a PLC controller and a welding power source, and in particular to a pulse interface circuit between a PLC and a TIG welding power source and a control method thereof. Background Art

[0002] In the automatic welding machine control system, PLC is generally used as the main controller, and the TIG welding power source receives the analog signal from the PLC as the current setting signal. For the convenience of control and the needs of the welding procedure, the parameter adjustment function of the welding power source itself is generally not used. In order to improve the welding quality, pulse current is required for welding in the welding process.

[0003] At present, in the above automatic welding machine control system, either the pulse current welding function is not provided, or the pulse function is realized by using analog conversion software. The first processing method makes the welding machine lack the pulse welding function, which affects the welding quality; while the second processing method has problems such as poor frequency accuracy, poor duty cycle accuracy, insufficiently steep pulse rise and fall edges, and complex programming. Summary of the invention

[0004] The purpose of the present invention is to solve the technical problems existing in the background technology. To this end, a pulse interface circuit between a PLC and a TIG welding power source and a control method thereof are provided.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] A pulse interface circuit includes an analog switch chip and a connection terminal;

[0007] Pin 1 of the analog switch chip is electrically connected to terminal 3 of the wiring terminal, and terminal 3 of the wiring terminal is connected to the peak welding current input signal;

[0008] Pin 5 of the analog switch chip is electrically connected to terminal 4 of the wiring terminal, and terminal 4 of the wiring terminal is connected to the base value welding current input signal;

[0009] The pin 10 of the analog switch chip is electrically connected to the terminal 1 of the wiring terminal, and the terminal 1 of the wiring terminal is connected to the pulse width modulation signal;

[0010] Pin 3 of the analog switch chip is electrically connected to one end of the voltage regulator tube D4, and the other end of the voltage regulator tube D4 is connected to the negative electrode of the power supply.

[0011] The following is a technical solution further defined by the circuit in the present invention, wherein the pin 3 of the analog switch chip is electrically connected to the terminal 2 of the wiring terminal, and the terminal 2 of the wiring terminal is electrically connected to the input end of the TIG welding power source as an output port.

[0012] The following is a technical solution further defined by the circuit in the present invention, wherein terminal 7, pin 6, and pin 5 of the wiring terminal are all connected to the negative pole of the power supply, and terminal 8 of the wiring terminal is connected to the positive pole of the power supply; a diode and a voltage regulator D1 are connected between terminal 7 and pin 8 of the wiring terminal, and the diode is connected in parallel with the voltage regulator D1.

[0013] The following is a technical solution further defined by the circuit in the present invention: the pin 10 of the analog switch chip is electrically connected to one end of the resistor, and the other end of the resistor is electrically connected to the positive electrode of the power supply.

[0014] The following is a technical solution further defined by the circuit in the present invention, wherein the pin 1 of the analog switch chip is electrically connected to one end of the voltage regulator tube D3, and the other end of the voltage regulator tube D3 is connected to the negative electrode of the power supply;

[0015] Pin 5 of the analog switch chip is electrically connected to one end of the voltage regulator tube D2, and the other end of the voltage regulator tube D2 is connected to the negative electrode of the power supply;

[0016] The pin 10 of the analog switch chip is electrically connected to one end of the voltage regulator tube D5, and the other end of the voltage regulator tube D5 is connected to the negative electrode of the power supply.

[0017] The following is a technical solution further limited by the circuit in the present invention, wherein pin 6, pin 9 and pin 7 of the analog switch chip are all connected to the negative pole of the power supply.

[0018] A control method based on the pulse interface circuit of the above item includes: a base welding current given value and a peak welding current given value output by a PLC controller through a D / A conversion module are input into the pulse interface circuit;

[0019] The pulse width modulation signal output by the PLC controller is input into the pulse interface circuit, which controls the pulse interface circuit to output a base welding current given value or a peak welding current given value, thereby providing the TIG welding power supply with a welding current pulse signal with adjustable frequency, duty cycle, base welding current and peak welding current, so that the TIG welding power supply generates a pulse welding current with adjustable frequency, duty cycle, base welding current and peak welding current.

[0020] The following is a technical solution further defined by the method of the present invention, wherein the pulse interface circuit selects to output a base welding current given value and a peak welding current given value during a high level period and a low level period of a pulse width modulation signal, respectively.

[0021] The following is a technical solution further defined by the method in the present invention, which uses a pulse width modulation signal to switch between a base welding current given value and a peak welding current given value, and has a steep rising edge and a falling edge; the pulse welding current output by the TIG welding power supply has a steep rising edge and a falling edge.

[0022] The following is a technical solution further defined by the method of the present invention: the pulse width modulation period of the PLC controller is 1-32767 milliseconds, the frequency of the pulse welding current is 0.03HZ-160HZ, and the duty cycle of the pulse welding current is 0-100%.

[0023] Compared with the prior art, the present invention has the following technical effects:

[0024] The pulse interface circuit of the present invention is used between PLC and TIG welding power supply to convert the pulse width modulation signal PWM and analog signal from the PLC controller into the pulse signal of the TIG welding power supply to generate a pulse welding current with adjustable frequency, duty cycle, base current and peak current.

[0025] The present invention is further described below in conjunction with the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 is a system block diagram of the present invention;

[0028] Figure 2 It is a circuit diagram of the present invention;

[0029] Figure 3 It is a circuit component connection diagram of the present invention;

[0030] Figure 4 It is a printed circuit board diagram of the present invention. DETAILED DESCRIPTION

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present invention, so the present invention is not limited by the specific embodiments disclosed below.

[0032] like Figure 1-4As shown, this embodiment provides a pulse interface circuit and a control method thereof, which are used for communication connection between a PLC controller and a TIG welding power source. It should be noted that the pulse interface circuit and the control method thereof of this embodiment can be used for communication connection between a programmable controller and a TIG welding power source.

[0033] like Figure 1 As shown, the PLC controller or other programmable controller sends three signals to the pulse interface circuit: base welding current set value, peak welding current set value, and pulse width modulation signal PWM. Among them, the base welding current set value and the peak welding current set value can be set according to the process requirements, and the pulse width modulation signal PWM can set its frequency and duty cycle. Under the control of the pulse width modulation signal, the base welding current set value and the peak welding current set value are sent to the output end of the pulse interface circuit during the high level and low level of the PWM signal respectively. The output at this output end is the modulated welding current pulse set value, which is sent to the current input end of the TIG welding power supply. The TIG welding power supply will output the corresponding pulse welding current.

[0034] like Figure 2 As shown, the pulse interface circuit of this embodiment is mainly composed of an analog switch integrated circuit, a logic judgment circuit and a protection circuit. Among them, Ib is the base welding current given value (0-10V), Ip is the peak welding current given value (0-10V), PWM is a pulse width modulation signal, and Iw is the current given value output to the TIG welding power supply.

[0035] The analog switch is an integrated circuit. The analog switch chip model UTC4052 is selected. The output can be determined to connect to which input quantity according to the selection signals S0 and S1, that is, the input and output have the following relationship:

[0036]

[0037]

[0038] When S1=S0=0, Y=Y0=Ib;

[0039] When S1=0 and S0=1, Y=Y1=Ip.

[0040] The logic judgment circuit is used to convert the high and low levels of the PWM pulse width modulation signal into the selection signals S1 and S0. The circuit is composed of logic gate circuits, and its logic function is: S1 = 0, S0 = PWM.

[0041] The protection circuit is used to protect the circuit from damage caused by over-power supply. The pulse interface circuit of this embodiment is used in TIG welding. When TIG welding is started, its high-frequency and high-voltage arc ignition signal will generate a large interference signal and over-voltage. The over-voltage will damage the various electronic components of the pulse interface circuit, so a reliable protection circuit must be added. The protection circuit is mainly composed of a voltage suppressor.

[0042] like Figure 3 As shown, a pulse interface circuit between a PLC and a TIG welding power source is mainly composed of an analog switch chip of model UTC4052, five voltage regulator tubes, a resistor, a capacitor and an 8-pin terminal JP1. Figure 4 for Figure 3 The corresponding printed circuit board diagram.

[0043] The terminal definitions of terminal block JP1 are shown in the following table:

[0044]

[0045] The pin definitions of the UTC4052 analog switch chip are shown in the following table:

[0046] Pin number Code Name and function 13，3 X,Y Input / output common terminal 6 INH Prohibited input 7 <![CDATA[V EE ]]> Supply voltage 8 <![CDATA[V SS ]]> Chip power supply negative voltage 10，9 A,B Switch control input 12，14，15，11 X0~X3 X channel input / output 1，5，2，4 Y0~Y3 Y channel input / output 16 <![CDATA[V DD ]]> Chip power supply positive voltage

[0047] The base welding current given value and the peak welding current given value output by the PLC controller through the D / A conversion module are used as the peak welding current input signal and the base welding current input signal respectively. The pulse width modulation signal is output by the PLC controller.

[0048] Pin 1 of the analog switch chip is electrically connected to terminal 3 of the wiring terminal, and terminal 3 of the wiring terminal is connected to the peak welding current input signal. Pin 5 of the analog switch chip is electrically connected to terminal 4 of the wiring terminal, and terminal 4 of the wiring terminal is connected to the base welding current input signal. Pin 10 of the analog switch chip is electrically connected to terminal 1 of the wiring terminal, and terminal 1 of the wiring terminal is connected to the pulse width modulation signal. Pin 3 of the analog switch chip is electrically connected to one end of the voltage regulator D4, and the other end of the voltage regulator D4 is connected to the negative pole of the power supply. Pin 3 of the analog switch chip is electrically connected to terminal 2 of the wiring terminal, and terminal 2 of the wiring terminal is electrically connected to the input end of the TIG welding power supply as an output port. Terminal 7, pin 6, and pin 5 of the wiring terminal are all connected to the negative pole of the power supply, and terminal 8 of the wiring terminal is connected to the positive pole of the power supply; a diode and a voltage regulator D1 are connected between terminal 7 and pin 8 of the wiring terminal, and the diode is connected in parallel with the voltage regulator D1. Pin 10 of the analog switch chip is electrically connected to one end of the resistor, and the other end of the resistor is electrically connected to the positive pole of the power supply. Pin 1 of the analog switch chip is electrically connected to one end of the voltage regulator tube D3, and the other end of the voltage regulator tube D3 is connected to the negative electrode of the power supply. Pin 5 of the analog switch chip is electrically connected to one end of the voltage regulator tube D2, and the other end of the voltage regulator tube D2 is connected to the negative electrode of the power supply. Pin 10 of the analog switch chip is electrically connected to one end of the voltage regulator tube D5, and the other end of the voltage regulator tube D5 is connected to the negative electrode of the power supply. Pin 6, pin 9, and pin 7 of the analog switch chip are all connected to the negative electrode of the power supply.

[0049] A control method based on a pulse interface circuit comprises: a base welding current given value and a peak welding current given value output by a PLC controller through a D / A conversion module are input into a pulse interface circuit; a pulse width modulation signal output by the PLC controller is input into the pulse interface circuit to control the pulse interface circuit to output a base welding current given value or a peak welding current given value, thereby providing a welding current pulse signal with adjustable frequency, duty cycle, base welding current and peak welding current to a TIG welding power source, so that the TIG welding power source generates a pulse welding current with adjustable frequency, duty cycle, base welding current and peak welding current.

[0050] The pulse interface circuit selects to output the base welding current given value and the peak welding current given value respectively during the high level period and the low level period of the pulse width modulation signal. The pulse width modulation signal is used to switch the base welding current given value and the peak welding current given value, and has a steep rising edge and falling edge; the pulse welding current output by the TIG welding power supply has a steep rising edge and falling edge. The pulse signal output by the high-speed output port corresponding to the PWM pulse width modulation instruction of the PLC controller has a very steep rising edge and falling edge, and the switching time of each channel of the analog switch is also less than 500 nanoseconds, so the welding current pulse signal output by the pulse interface circuit of this embodiment also has a very steep rising edge and falling edge, so that the pulse welding current output by the welding power supply also has a steeper rising edge and falling edge characteristic.

[0051] The pulse width modulation period of the PLC controller is 1-32767 milliseconds, the frequency of the pulse welding current is 0.03HZ-160HZ, and the duty cycle of the pulse welding current is 0-100%.

[0052] Configure the PLC program matching the pulse interface circuit, and output three signals in the PLC controller: one is the base value welding current analog value given value ( Figure 3 One is the peak welding current analog value ( Figure 3 Terminal 3 of the middle terminal); one is the PWM pulse width modulation signal ( Figure 3 Terminal 1 of the middle wiring terminal). The PLC controller supports analog control and PWM pulse width modulation functions.

[0053] The analog output value (base welding current set value and peak welding current set value) can be changed by changing the digital value of the D / A conversion module.

[0054] For a pulse width modulation signal PWM, the frequency value and the duty cycle value of the PWM signal can be changed by changing the cycle time value and the pulse width time value.

[0055] The above is only a preferred embodiment of the present invention, and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, all equivalent changes made according to the shape, structure and principle of the present invention without departing from the content of the technical solution of the present invention should be included in the protection scope of the present invention.

Claims

1. A pulse interface circuit, characterized in that: Including analog switch chip and wiring terminals; Pin 1 of the analog switch chip is electrically connected to terminal 3 of the wiring terminal, and terminal 3 of the wiring terminal is connected to the peak welding current input signal; Pin 5 of the analog switch chip is electrically connected to terminal 4 of the wiring terminal, and terminal 4 of the wiring terminal is connected to the base value welding current input signal; The pin 10 of the analog switch chip is electrically connected to the terminal 1 of the wiring terminal, and the terminal 1 of the wiring terminal is connected to the pulse width modulation signal; Pin 3 of the analog switch chip is electrically connected to one end of the voltage regulator tube D4, and the other end of the voltage regulator tube D4 is connected to the negative electrode of the power supply.

2. A pulse interface circuit as claimed in claim 1, characterized in that: The pin 3 of the analog switch chip is electrically connected to the terminal 2 of the wiring terminal, and the terminal 2 of the wiring terminal is electrically connected to the input end of the TIG welding power source as an output port.

3. A pulse interface circuit as claimed in claim 1, characterized in that: Terminal 7, pin 6 and pin 5 of the wiring terminal are all connected to the negative pole of the power supply, and terminal 8 of the wiring terminal is connected to the positive pole of the power supply; a diode and a voltage regulator D1 are connected between terminal 7 and pin 8 of the wiring terminal, and the diode and the voltage regulator D1 are connected in parallel.

4. A pulse interface circuit as claimed in claim 1, characterized in that: The pin 10 of the analog switch chip is electrically connected to one end of the resistor, and the other end of the resistor is electrically connected to the positive electrode of the power supply.

5. A pulse interface circuit as claimed in claim 1, characterized in that: Pin 1 of the analog switch chip is electrically connected to one end of the voltage regulator tube D3, and the other end of the voltage regulator tube D3 is connected to the negative electrode of the power supply; Pin 5 of the analog switch chip is electrically connected to one end of the voltage regulator tube D2, and the other end of the voltage regulator tube D2 is connected to the negative electrode of the power supply; The pin 10 of the analog switch chip is electrically connected to one end of the voltage regulator tube D5, and the other end of the voltage regulator tube D5 is connected to the negative electrode of the power supply.

6. A pulse interface circuit as claimed in claim 1, characterized in that: Pin 6, pin 9 and pin 7 of the analog switch chip are all connected to the negative pole of the power supply.

7. A control method for a pulse interface circuit according to any one of claims 1 to 6, characterized in that: include: The base welding current given value and the peak welding current given value output by the PLC controller through the D / A conversion module are input into the pulse interface circuit; The pulse width modulation signal output by the PLC controller is input into the pulse interface circuit, which controls the pulse interface circuit to output a base welding current given value or a peak welding current given value, thereby providing the TIG welding power supply with a welding current pulse signal with adjustable frequency, duty cycle, base welding current and peak welding current, so that the TIG welding power supply generates a pulse welding current with adjustable frequency, duty cycle, base welding current and peak welding current.

8. The control method according to claim 7, characterized in that: The pulse interface circuit selects to output a base welding current given value and a peak welding current given value respectively during a high level period and a low level period of a pulse width modulation signal.

9. The control method according to claim 8, characterized in that: A pulse width modulation signal is used to switch between a base welding current given value and a peak welding current given value, and has a steep rising edge and a falling edge; the pulse welding current output by the TIG welding power source has a steep rising edge and a falling edge.

10. The control method according to claim 7, characterized in that: The pulse width modulation period of the PLC controller is 1-32767 milliseconds, the frequency of the pulse welding current is 0.03HZ-160HZ, and the duty cycle of the pulse welding current is 0-100%.

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