CN1325217C - Digital flip flop of three phase full bridge controllable silicon welding power source main loop - Google Patents

Abstract

A digital trigger circuit for the main circuit of a three-phase full-bridge thyristor welding power supply, comprising: a main circuit, a trigger drive circuit and a synchronous circuit, the common zero point of the synchronous circuit three-phase synchronous voltage and synchronous transformer passes through resistors R11, R12, R13, R14, R15, R16 and voltage regulator tubes D1, D2, D3, D4, D5, D6 form a loop and add on the AC input transistor output optocoupler U1, U2, U3, the present invention utilizes the high-speed data processing and computing power of DSP, can While realizing the trigger control of the thyristor power device, it completes the closed-loop control of the output voltage or current of the power supply, and realizes no-difference regulation. The invention has the advantages of simple hardware circuit, high real-time control precision, safe and reliable output trigger pulse, high symmetry, flexible and diverse control forms, etc., and at the same time, the stability and reliability of the system are well guaranteed.

Description

Digital trigger circuit of main circuit of three-phase full-bridge SCR welding power supply

technical field

The invention relates to a main circuit of a welding power supply, in particular to a digital trigger circuit of the main circuit of a three-phase full-bridge thyristor welding power supply, belonging to the technical field of electric welding machines.

Background technique

The large current feed system composed of thyristor rectifier bridge is widely used in industrial production. It is a very common circuit to use thyristor as the power device in the main circuit in the welding power supply. The high-power rectifier bridge has high requirements for the thyristor trigger circuit: high control precision, good real-time performance, high symmetry, strong stability, and safe and reliable triggering. At present, the thyristor trigger circuit mainly adopts two design methods of discrete components and application-specific integrated circuits. The trigger circuit designed with discrete components has a large dispersion of multi-phase circuit performance, difficult debugging, poor pulse symmetry, poor stability and reliability, etc. Disadvantages: The reliability of the trigger circuit designed by using the dedicated integrated trigger circuit chip is improved compared with the use of discrete components, but it still has the disadvantages of analog triggers.

After searching the literature of the prior art, it was found that Peng Jiayin published "a trigger circuit for a three-phase fully-controlled bridge thyristor rectifier controlled by a single-chip microcomputer" in "Electronic Technology" No. 1, 2002. This article uses an 80C196KB single-chip microcomputer combined Peripheral devices realize the trigger control of the thyristor three-phase full-controlled bridge. This design improves the anti-interference ability of the trigger and improves the symmetry of the three-phase trigger pulse. In addition, software programming can be used to obtain a trigger with adjustable trigger angle. pulse. Although this design is compared with the two design methods of discrete components and ASICs to realize the trigger control of the thyristor three-phase full-controlled bridge, it has advantages in the anti-interference of the trigger, flexibility and the symmetry of the three-phase trigger pulse. It has been greatly improved, but discrete analog devices are still used in the synchronous pulse forming circuit to realize the synchronization of the synchronous voltage signal and the power frequency signal, that is, there are still disadvantages of using an analog control circuit.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies and defects in the prior art, to provide a digital trigger circuit for the main circuit of a three-phase full-bridge thyristor welding power supply, so that it realizes the full digital trigger control of the main circuit thyristor power device . The invention adopts a digital controller composed of a digital signal processor DSP, utilizes the high-speed data processing and computing capabilities of the DSP, and can complete the closed-loop control of the output voltage or current of the power supply while realizing the trigger control of the thyristor power device, and realizes wireless poor regulation.

The present invention is achieved through the following technical solutions. The circuit of the present invention includes: a main circuit and a trigger drive circuit, wherein the composition and connection mode of the main circuit are: the primary side of the main circuit transformer is connected in a star shape, and the secondary side is a three-phase full control It consists of a bridge rectifier circuit (connected into a triangle) and a synchronous transformer. The cathodes of the thyristors S1, S2, and S3 of the full-controlled bridge rectifier circuit are connected in parallel as the positive output of the power supply; the anodes of the thyristors S4, S5, and S6 are connected in parallel to the filter inductance L of the main circuit Together, the resistor R10 is connected between the filter inductor and the positive output terminal of the power supply to play the role of freewheeling, and the other end of the filter inductor L is used as the other end of the power supply output; the anode of the thyristor S1 and the cathode of S4 are connected together ; The anode of SCR S2 and the cathode of S5 are connected together; the anode of SCR S3 and the cathode of S6 are connected together; capacitor C1 and resistor R1 are connected together and connected between the anode and cathode of SCR S1 For protection; capacitor C2 and resistor R2 are connected together and connected between the anode and cathode of SCR S2 for protection; capacitor C3 and resistor R3 are connected together and connected between the anode and cathode of SCR S3 For protection; capacitor C4 and resistor R4 are connected together and connected between the anode and cathode of SCR S4 for protection; capacitor C5 and resistor R5 are connected together and connected between the anode and cathode of SCR S5 It plays a protective role; the capacitor C6 and the resistor R6 are connected together and connected between the anode and cathode of the thyristor S6 for protection.

The composition and connection method of the trigger drive circuit are: the cathode of the main circuit power thyristor S1 is connected to R41 and C37, the control pole of S1 is connected to R41, C37 and the cathode of diode D26; the cathode of S2 is connected to R43 and C39, S2 The control pole of S3 is connected with R43, C39 and the cathode of diode D28; the cathode of S3 is connected with R45 and C41, the control pole of S3 is connected with R45, C41 and the cathode of diode D30; the cathode of S4 is connected with R42 and C38, and the control of S4 The pole is connected with R42, C38 and the cathode of diode D27; the cathode of S5 is connected with R44 and C40, the control pole of S5 is connected with R44, C40 and the cathode of diode D29; the cathode of S6 is connected with R46 and C42, and the control pole of S6 is connected with R46, C42 and the cathode of the diode D26 are connected; the anodes of the main circuit power thyristors S1, S2, S3, S4, S5, and S6 are respectively connected to the resistors R35, R37, R39, R36, R38, and R40, and the T1PWM and T2PWM of the DSP , T3PWM pins are respectively connected with pins 9, 11, and 13 of U7, pins 8, 10, and 12 of U7 are respectively connected with pins 4 of triac optocouplers U4, U5, and U6, and optocouplers U4, U5, Pin 2 of U6 is connected to pin 3, pin 1 of optocouplers U4, U5, and U6 is connected to resistors R32, R33, and R34 respectively, and resistors R32, R33, and R34 are all connected to power supply VCC, and pin 5 of optocouplers U4, U5, and U6 The pins are respectively connected to the anodes of diodes D27, D29, and D31; the 6 pins of optocouplers U4, U5, and U6 are respectively connected to R36, R38, and R40; the 7 pins of optocouplers U4, U5, and U6 are respectively connected to diodes D26, D28, and D30 The anode of the optocoupler U4, U5, and U6 are connected to R35, R37, and R39 respectively.

The present invention also includes a synchronous circuit, which is constituted and connected as follows: the common zero point of the three-phase synchronous voltage and synchronous transformer passes through resistors R11, R12, R13, R14, R15, R16 and regulator tubes D1, D2, D3, D4, D5 , D6 form a loop and add it to the AC input transistor output optocoupler U1, U2, U3, wherein, R11, C34 are connected to the cathode of the regulator D1; R12, C34 are connected to the cathode of the regulator D2; R13, C35 are connected to the regulator The cathode of the pressure tube D3 is connected to the cathode of the voltage regulator tube D4, R14, C35; the cathode connection of R15, C36 and the voltage regulator tube D5; the cathode connection of R16, C35 and the voltage regulator tube D6; the voltage regulator tube D1, D3, D5 The anodes of the AC input transistor output optocouplers U1, U2, and U3 are respectively connected to pin 1; the anodes of the voltage regulator tubes D2, D4, and D6 are respectively connected to the 2 pins of the AC input transistor output optocouplers U1, U2, and U3; the optocoupler The 4 pins of U1, U2, and U3 are respectively connected to the power supply VCC, and the 3 pins of the optocoupler U1, U2, and U3 are respectively connected to one end of R29, 1 pin of U7, one end of R30, 3 pins of U7, and one end of R31. The 5 pins of U7 are connected together, the other end of R29, the other end of R30, and the other end of R31 are respectively connected to the analog ground, and the 2 pins, 4 pins, and 6 pins of U7 are respectively connected to CAP1, CAP2, and CAP3 of the DSP. pin connection.

When the present invention works, at first, the three-phase voltage obtained by the power grid outputs the three-phase synchronous voltage through the synchronous transformer, and the common zero point of the three-phase synchronous voltage and the synchronous transformer passes through the resistors R11, R12, R13, R14, R15, R16 and voltage regulator Tubes D1, D2, D3, D4, D5, D6 form a loop and add to the AC input transistor output optocoupler U1, U2, U3. When the synchronization voltage is non-zero, the outputs of U1, U2, and U3 are turned on, and the output of pin 3 is high level, which is reversed to low level by U7. When the synchronization voltage crosses zero, U1, U2, and U3 are turned off, and pin 3 The output is low level, which is reversed by U7 to high level to obtain the synchronization signal; then, the event manager CAP1, CAP2, and CAP3 pins of the DSP controller capture the rising edge of the synchronization signal, thereby generating a corresponding interrupt request, the DSP core immediately responds to the interrupt and turns to the interrupt program.

In the interrupt program, the DSP calculates the value of the control angle of the thyristor in the next cycle calculated in the main program (the value of the control angle of the thyristor is obtained by the given amount and sampling of the welding current or voltage obtained through communication. The difference of the current or voltage feedback value is calculated by the PID algorithm) and assigned to the corresponding general-purpose timer T _x PWM and starts the timer to start counting. After clearing the corresponding interrupt flag bit, exit the interrupt subroutine and return to main program.

During the running of the main program, DSP completes the real-time detection of welding current/voltage, and DSP performs PID algorithm according to the deviation value between the given value of welding current/voltage and the real-time detected welding current/voltage feedback value, and calculates the next control cycle The control angle of the SCR. While the DSP main program is performing the above operations, the general-purpose timer Tx completes the counting function. This counting is completed in the background, that is, it does not occupy the running time of the DSP. When the counting time reaches the set time, the TxPWM pin of the DSP outputs a trigger pulse with a width of 70° through the bidirectional thyristor optocoupler U4, U5, and U6 for level isolation, and the output terminals of the bidirectional thyristor U4, U5, and U6 are Two groups of bidirectional conduction thyristors are respectively connected to the anode and control pole of the main circuit power thyristor through diodes D26, D27, D28, D29, D30 and D31 to play a switch role.

The acquisition and conversion of the above-mentioned synchronous signal, the algorithm realization of the phase-shifting trigger pulse of the digital signal processor, and then the driving link are all direct circulation and processing of digital information. The control accuracy is directly determined by the software, which reduces the environmental temperature, The influence of external factors such as power supply voltage and time on the control characteristics of the system ensures the consistency and stability of the control characteristics of the control system during long-term operation.

The present invention has substantive features and significant progress. The digital controller composed of digital signal processor DSP has the advantages of simple hardware circuit, high real-time control precision, safe and reliable output trigger pulse, high symmetry, and flexible and diverse control forms. The stability and reliability of the system are well guaranteed.

Description of drawings

Fig. 1 is the main circuit diagram of the present invention

Figure 2 is a synchronous circuit and trigger drive circuit diagram

Detailed ways

As shown in Figures 1 and 2, the present invention includes: a main circuit, a trigger drive circuit, and a synchronization circuit.

The composition and connection mode of the main circuit are: the primary side of the main circuit transformer is connected in a star shape, the secondary side is composed of a three-phase fully-controlled bridge rectifier circuit and a synchronous transformer, and the fully-controlled bridge rectifier circuit is connected in a delta, and its thyristor S1 The cathodes of , S2, and S3 are connected together as the positive output of the power supply; the anodes of SCR S4, S5, and S6 are connected in parallel with the filter inductor L of the main circuit, and the resistor R10 is connected across the filter inductor Between the positive output terminal of the power supply, the other end of the filter inductor L is used as the other end of the power output; the anode of the thyristor S1 and the cathode of S4 are connected together; the anode of the thyristor S2 and the cathode of S5 are connected together; The anode of SCR S3 and the cathode of S6 are connected together; C1 and R1, C2 and R2, C3 and R3, C4 and R4, C5 and R5, C6 and R6 are respectively connected in series and connected to SCR S1, S2, S3 , between the anodes and cathodes of S4, S5, and S6; the composition and connection of the trigger drive circuit are: the cathode of the main circuit power thyristor S1 is connected to R41 and C37, the control pole of S1 is connected to R41, C37 and diode D26 The cathode is connected; the cathode of S2 is connected with R43 and C39, the control pole of S2 is connected with R43, C39 and the cathode of diode D28; the cathode of S3 is connected with R45 and C41, and the control pole of S3 is connected with R45, C41 and the cathode of diode D30 ; The cathode of S4 is connected with R42 and C38, the control pole of S4 is connected with R42, C38 and the cathode of diode D27; the cathode of S5 is connected with R44 and C40, the control pole of S5 is connected with R44, C40 and the cathode of diode D29; S6 The cathode of S6 is connected with R46 and C42, the control pole of S6 is connected with R46, C42 and the cathode of diode D26; the anodes of main circuit power thyristors S1, S2, S3, S4, S5, S6 are respectively connected with resistors R35, R37, R39 , R36, R38, R40 connection, the T1PWM, T2PWM, T3PWM pins of the DSP are respectively connected to the 9 pins, 11 pins, and 13 pins of U7, and the 8 pins, 10 pins, and 12 pins of U7 are connected to the triac optocoupler U4, U5, The 4 pins of U6 are connected, the 2 pins of optocouplers U4, U5, and U6 are connected with their 3 pins, the 1 pins of optocouplers U4, U5, and U6 are respectively connected with resistors R32, R33, and R34, and the resistors R32, R33, and R34 are all connected to the power supply. VCC connection, the 5 pins of optocoupler U4, U5, U6 are respectively connected to the anodes of diodes D27, D29, D31, the 6 pins of optocoupler U4, U5, U6 are respectively connected to R36, R38, R40, the optocoupler U4, U5, The 7 pins of U6 are respectively connected with the anodes of diodes D26, D28 and D30, and the 8 pins of optocouplers U4, U5 and U6 are respectively connected with R35, R37 and R39.

The synchronous circuit is composed and connected as follows: the common zero point of the three-phase synchronous voltage and the synchronous transformer passes through resistors R11, R12, R13, R14, R15, R16 and regulator tubes D1, D2, D3, D4, D5, D6 constitutes a loop and is added to the AC input transistor output optocoupler U1, U2, U3, wherein, R11, C34 are connected to the cathode of the voltage regulator D1; R12, C34 are connected to the cathode of the voltage regulator D2; R13, C35 are connected to the voltage regulator The cathode connection of the tube D3; the cathode connection of R14, C35 and the voltage regulator tube D4; the cathode connection of R15, C36 and the voltage regulator tube D5; the cathode connection of R16, C35 and the voltage regulator tube D6; the voltage regulator tube D1, D3, D5 The anodes of the AC input transistor output optocouplers U1, U2, and U3 are respectively connected to pin 1; the anodes of the voltage regulator tubes D2, D4, and D6 are respectively connected to pin 2 of the AC input transistor output optocoupler U1, U2, and U3; the optocoupler The 4 pins of U1, U2, and U3 are respectively connected to the power supply VCC, and the 3 pins of the optocoupler U1, U2, and U3 are respectively connected to one end of R29, 1 pin of U7, one end of R30, 3 pins of U7, and one end of R31. The 5 pins of U7 are connected together, the other end of R29, the other end of R30, and the other end of R31 are respectively connected to the analog ground, and the 2 pins, 4 pins, and 6 pins of U7 are respectively connected to CAP1, CAP2, and CAP3 of the DSP. pin connection.

Take the system closed-loop control process to realize the digital trigger of the constant current characteristic output of the power supply as an example. The invention adopts the digital signal processor DSP as the core of the control system to realize the digital triggering of the power thyristor of the main circuit of the thyristor welding power supply.

First, the three-phase voltage obtained from the power grid outputs a three-phase synchronous voltage through a synchronous transformer, and the common zero point of the three-phase synchronous voltage and the synchronous transformer passes through resistors R11, R12, R13, R14, R15, R16 and regulator tubes D1, D2, D3, D4, D5, D6 form a loop and add to the AC input transistor output optocoupler U1, U2, U3. When the synchronization voltage is non-zero, the outputs of U1, U2, and U3 are turned on, and the output of pin 3 is high level, which is reversed to low level by U7. When the synchronization voltage crosses zero, U1, U2, and U3 are turned off, and pin 3 The output is low level, which is reversed by U7 to high level to obtain the synchronization signal; then, the event manager CAP1, CAP2, and CAP3 pins of the DSP controller capture the rising edge of the synchronization signal, thereby generating a corresponding interrupt request, the DSP core immediately responds to the interrupt and turns to the interrupt program.

In the interrupt program, the DSP first judges which CAP signal generated the interrupt. If the DSP judges that the interrupt is generated by capturing the rising edge of CAP1, it will transfer to the CAP1 interrupt processing subroutine. The following functions are completed in this subroutine : Assign the value of the control angle of the SCR in the next control cycle calculated in the main program to the general timer T1, start the T1 timer to start counting, and exit the interrupt subroutine after clearing the corresponding interrupt flag bit and return to the main program.

During the running of the main program, the DSP completes the real-time detection of the welding current, and the DSP performs the PID algorithm according to the deviation value between the given value of the welding current and the real-time detected welding current feedback value, and calculates the control of the thyristor in the next control cycle. horn. While the DSP main program is performing the above operations, the general-purpose timer T1 completes the counting function. This counting is completed in the background, that is, it does not occupy the running time of the DSP. When the counting time reaches the set time, the T1PWM pin of the DSP outputs a trigger pulse with a width of 70° through the bidirectional thyristor optocoupler U4 for level isolation. The output terminals of the bidirectional thyristor U4 are two sets of bidirectional conduction thyristors. The diodes D26 and D27 are respectively connected between the anode and the control electrode of the power thyristor of the main circuit, so as to realize conduction of the thyristor S1 or S4. If the interrupt program is generated by CAP2, the above operations are the same. The T2PWM trigger pulse output by the DSP is level-isolated through the bidirectional thyristor optocoupler U5. It is connected between the anode and the control electrode of the power thyristor of the main circuit, and then the conduction of the thyristor S2 or S5 is realized. If the interrupt program is generated by CAP3, the above operations are the same. The T3PWM trigger pulse output by the DSP is level-isolated through the bidirectional thyristor optocoupler U6, and the output terminals of the bidirectional thyristor U6 are two sets of bidirectional conduction thyristors. It is connected between the anode and the control electrode of the power thyristor of the main circuit, and then the conduction of the thyristor S3 or S6 is realized.

During the welding process, DSP generates a capture interrupt every 3.3ms, that is, repeats the above-mentioned process every 3.3ms, and then completes the digital trigger control of the thyristor power device, that is, completes the constant current control of the output of the welding power supply.

Claims (3)

1. A digital trigger circuit of a main circuit of a three-phase full-bridge thyristor welding power supply, comprising: a main circuit, a trigger drive circuit, characterized in that it also includes a synchronous circuit, and its composition and connection mode are: three-phase synchronous voltage and The common zero point of the synchronous transformer is added to the output optocoupler U1, U2, U3 of the AC input transistor through a loop formed by resistors R11, R12, R13, R14, R15, R16 and voltage regulator tubes D1, D2, D3, D4, D5, and D6. Among them, R11, C34 are connected to the cathode of the voltage regulator tube D1; R12, C34 are connected to the cathode of the voltage regulator tube D2; R13, C35 are connected to the cathode of the voltage regulator tube D3; R14, C35 are connected to the cathode of the voltage regulator tube D4; R15, C36 are connected to the cathode of the voltage regulator tube D5; R16, C35 are connected to the cathode of the voltage regulator tube D6; the anodes of the voltage regulator tubes D1, D3, and D5 are respectively connected to pin 1 of the AC input transistor output optocoupler U1, U2, and U3 Connection; the anodes of the voltage regulator tubes D2, D4, and D6 are respectively connected to the 2 pins of the AC input transistor output optocoupler U1, U2, and U3; the 4 pins of the optocoupler U1, U2, and U3 are respectively connected to the power supply VCC, and the optocoupler The 3 pins of U1, U2, and U3 are respectively connected with one end of R29, 1 pin of U7, one end of R30, 3 pins of U7, one end of R31, and 5 pins of U7, and the other end of R29 and the other end of R30 , The other end of R31 is respectively connected with the analog ground, and the 2 pins, 4 pins, and 6 pins of U7 are respectively connected with the CAP1, CAP2, and CAP3 pins of the DSP. 2. The digital trigger circuit of the main circuit of the three-phase full-bridge thyristor welding power supply according to claim 1, characterized in that, the composition and connection mode of the main circuit are: the primary side of the main circuit transformer is connected into a star The secondary side is composed of a three-phase fully-controlled bridge rectifier circuit and a synchronous transformer. The fully-controlled bridge rectifier circuit is connected in a triangle, and the cathodes of the thyristors S1, S2, and S3 are connected together as the positive output of the power supply; The anodes of thyristors S4, S5, and S6 are connected in parallel with the filter inductor L of the main circuit, and the resistor R10 is connected between the filter inductor and the positive output terminal of the power supply. The other end of the filter inductor L is used as the power supply The other end of the output; the anode of SCR S1 and the cathode of S4 are connected together; the anode of SCR S2 and the cathode of S5 are connected together; the anode of SCR S3 and the cathode of S6 are connected together; C1 and R1 , C2 and R2, C3 and R3, C4 and R4, C5 and R5, C6 and R6 are respectively connected in series and connected between the anode and cathode of thyristor S1, S2, S3, S4, S5, S6. 3. The digital trigger circuit of the main circuit of the three-phase full-bridge thyristor welding power supply according to claim 1, characterized in that, the composition and connection mode of the trigger drive circuit are: the main circuit power thyristor S1 The cathode is connected with R41 and C37, the control pole of S1 is connected with R41, C37 and the cathode of diode D26; the cathode of S2 is connected with R43 and C39, the control pole of S2 is connected with R43, C39 and the cathode of diode D28; the cathode of S3 is connected with R45 is connected to C41, the control pole of S3 is connected to R45, C41 and the cathode of diode D30; the cathode of S4 is connected to R42 and C38, the control pole of S4 is connected to R42, C38 and the cathode of diode D27; the cathode of S5 is connected to R44 and C40 is connected, the control pole of S5 is connected with R44, C40 and the cathode of diode D29; the cathode of S6 is connected with R46 and C42, the control pole of S6 is connected with R46, C42 and the cathode of diode D26; the main circuit power SCR S1, The anodes of S2, S3, S4, S5, and S6 are respectively connected to resistors R35, R37, R39, R36, R38, and R40, and the T1PWM, T2PWM, and T3PWM pins of the DSP are respectively connected to pins 9, 11, and 13 of U7. Pins 8, 10, and 12 of U7 are connected to pins 4 of the bidirectional thyristor optocouplers U4, U5, and U6, pins 2 of optocouplers U4, U5, and U6 are connected to pins 3, and pins 1 of optocouplers U4, U5, and U6 are connected. Connect with resistors R32, R33, R34 respectively. Resistors R32, R33, R34 are all connected with power supply VCC. Pin 5 of optocouplers U4, U5, U6 are respectively connected with anodes of diodes D27, D29, D31. Optocouplers U4, U5, The 6 pins of U6 are respectively connected to R36, R3, R40, the 7 pins of optocoupler U4, U5, U6 are respectively connected to the anodes of diodes D26, D28, D30, the 8 pins of optocoupler U4, U5, U6 are respectively connected to R35, R37 , R39 connection.

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