SiC welding power supply driving circuit

Abstract

The invention discloses a SiC welding power supply driving circuit, and belongs to the technical field of electronics and welding equipment. The circuit comprises a power supply unit, a driving optocoupler matrix unit, a positive and negative voltage generation unit and a driving signal overvoltage protection unit, a special driving integrated chip is replaced by a universal optocoupler, and a special module power supply is replaced by a push-pull transformer-full-wave rectification circuit. The conversion from a unipolar power supply to a bipolar power supply is realized by using a voltage-regulator tube-capacitor circuit, and the problems of misconduction and negative voltage over-limit caused by SiCMOSFET bridge arm crosstalk are solved through an overvoltage protection mechanism. The universality and reliability of the drive circuit are improved, the cost is reduced, the drive circuit is suitable for the inverter welding machine with a SiCMOSFET as a core power device, and efficient and stable operation of a welding power source is guaranteed.

Description

Technical Field

[0001] This invention relates to the field of electronics and welding equipment technology, specifically a SiC welding power supply drive circuit. Background Technology

[0002] In inverter welding machines, the drive circuit is the crucial bridge connecting the microcontroller (low-voltage control) and the power devices (high-voltage power circuit), and its performance directly affects the reliability of the welding machine. The new generation of inverter welding machines uses SiC MOSFETs as the core power devices, offering advantages such as fast switching speed and low losses, but also introducing the following technical challenges:

[0003] Existing drive circuits rely on dedicated integrated chips and modular power supplies, which are costly and have poor versatility.

[0004] The high switching speed of SiC MOSFETs results in a large di / dt, and crosstalk between bridge arms can easily cause false turn-on.

[0005] When turned off, a negative voltage is required for driving. The downward spikes generated by crosstalk and the superposition of the negative voltage may exceed the gate negative voltage limit, leading to device damage.

[0006] Discrete circuits that convert unipolar power to bipolar power have weak anti-interference capabilities and low reliability.

[0007] Therefore, there is an urgent need for a low-cost, highly versatile SiC welding power supply drive circuit that can solve the problems of crosstalk and negative voltage over-limit. Summary of the Invention

[0008] This invention provides a SiC welding power supply drive circuit to solve the problems mentioned in the background art.

[0009] According to an embodiment of the present invention, a SiC welding power supply drive circuit is provided, applied to an H-bridge inverter welding power supply using SiCMOSFETs as power devices, comprising the following units:

[0010] Power supply unit:

[0011] Input: Obtain DC voltage Vcc (15V) from the DC / DC conversion module of the welding power supply;

[0012] Circuit composition: A push-pull transformer and a full-wave rectifier circuit are used to convert Vcc into 4 isolated DC outputs (VccAH, VccAL, VccBH, VccBL), each with an output voltage of 24V, which power the output side of the drive optocouplers of the 4 SiC MOSFETs of the H-bridge.

[0013] Function: Replaces dedicated module power supplies, achieving electrical isolation between input and output sides and independent power supply for multiple circuits.

[0014] Drive the optical coupler matrix unit:

[0015] Input: Receives 4 PWM control signals (PWMAH, PWMAL, PWMBH, PWMBL) sent by the controller, which control the SiCMOSFETs of the upper bridge arm A, lower bridge arm A, upper bridge arm B, and lower bridge arm B of the H-bridge.

[0016] Core component: A general-purpose optocoupler (replacing the dedicated driver integrated chip) is used to achieve isolated transmission of low-voltage control signals and high-voltage drive circuits;

[0017] Function: Shapes and isolates the PWM signal and outputs it to the positive and negative voltage generation unit.

[0018] Positive and negative pressure generating unit:

[0019] Circuit composition: It consists of a Zener diode (such as a 6.8V Zener diode) and a capacitor (such as a 10μF electrolytic capacitor);

[0020] Working principle: The 24V unipolar positive voltage output from the power supply unit is converted into a bipolar driving voltage, where the positive voltage is 18.9V (turn-on voltage) and the negative voltage is -5.1V (turn-off voltage).

[0021] Function: To meet the requirements of SiCMOSFET for positive voltage turn-on and negative voltage turn-off, and to suppress crosstalk voltage.

[0022] Drive signal overvoltage protection unit:

[0023] Circuit composition: Zener diodes connected in reverse series (such as a 24V positive Zener diode and a 6.8V negative Zener diode);

[0024] Function: Limits the positive voltage of the drive signal to no more than 24V and the negative voltage to no less than -6.8V to prevent overvoltage damage to devices caused by the superposition of crosstalk spikes and drive voltage.

[0025] The connection relationship of the above units is as follows: the power supply unit supplies power to the drive optocoupler matrix unit, the PWM signal output by the drive optocoupler matrix unit is converted into a bipolar signal by the positive and negative voltage generation unit, and then connected to the gate of the SiCMOSFET through the drive signal overvoltage protection unit to realize the driving and protection of the H-bridge inverter circuit.

[0026] The power supply unit includes a self-resonant controller, switching transistors U89 and U90, capacitors C50 and C51, transformers T7 and T8, and four rectifier and filter modules. The four rectifier and filter modules have identical structures, with one module including diodes D61, D62, D63, D64, and capacitor C53. The drive optocoupler matrix unit contains four drive optocoupler modules, all with identical structures, connected to the four rectifier and filter modules. One drive optocoupler module includes an optocoupler chip U98, resistor R82, and capacitor C51. The positive and negative voltage generation unit includes four positive and negative voltage generation circuits, all with identical structures, and is connected to four driving optocoupler modules. One of the positive and negative voltage generation circuits includes resistors R68 and R66, capacitors C58 and C59, and diode DZ15. The drive signal overvoltage protection unit includes four drive signal overvoltage protection circuits, all with identical structures, and is connected to four positive and negative voltage generation circuits. One of the drive signal overvoltage protection circuits includes diodes DZ13 and DZ14, resistor R67, and capacitor C57.

[0027] A SiC welding power supply system includes an input switch, a rectifier circuit, a DC support and filter capacitor, an H-bridge inverter circuit, an isolation transformer, an output rectifier and filter circuit, and the aforementioned drive circuit, connected in sequence. The drive circuit connects the controller and the SiC MOSFET of the H-bridge inverter circuit to achieve driving and protection.

[0028] The rectifier circuit is a three-phase rectifier circuit, including diodes D55, D56, D57, D58, D59, and D60. The H-bridge inverter circuit includes MOSFETs U76, U77, U78, and U79. The DC support and filter capacitor is capacitor C36. The output rectifier and filter circuit includes diodes D21 and D22. The anode of diode D55 is connected to the cathode of diode D59 and the input switch. The anode of diode D58 is connected to the cathode of diode D57 and the input switch. The anode of diode D56 is connected to the cathode of diode D55 and the input switch. The cathode of diode D60 is connected to the cathodes of diodes D58 and D56, capacitor C36, and the drain of MOSFET U77. The anode of diode D59 is connected to the anodes of diodes D57 and D55, the other end of capacitor C36, and the source of MOSFET U78 and U77. The source of U77 is connected to the drain of MOSFET U76, the drive circuit, and the primary winding of the isolation transformer. The source of MOSFET U78 is connected to the drain of MOSFET U79, the drive circuit, and the other end of the primary winding of the isolation transformer. The secondary winding of the isolation transformer is connected to diodes D21 and D22 respectively.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. Cost reduction: The use of general-purpose optocouplers and push-pull transformer-full-wave rectifier circuits to replace dedicated chips and module power supplies improves versatility and reduces costs by more than 30%;

[0031] 2. Enhanced anti-crosstalk capability: Through negative voltage turn-off design and overvoltage protection unit, it effectively suppresses false turn-on caused by bridge arm crosstalk, and the peak crosstalk voltage is reduced by 40%.

[0032] 3. Improved reliability: The bipolar power conversion circuit has strong anti-interference capability, and the overvoltage protection mechanism avoids negative voltage exceeding the limit, reducing the component failure rate by 90%.

[0033] 4. Good compatibility: It is suitable for various inverter welding machines based on SiCMOSFET, without the need to redesign the drive circuit for different models of devices. Attached Figure Description

[0034] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a schematic diagram of the welding power supply system of the present invention.

[0036] Figure 2 This is a schematic diagram of the driving circuit of the present invention. Detailed Implementation

[0037] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] In one embodiment, see Figure 1 and Figure 2 A SiC welding power supply drive circuit includes a power supply unit, a drive optocoupler matrix unit, a positive and negative voltage generation unit, and a drive signal overvoltage protection unit. The input terminal of the power supply unit is connected to a DC / DC converter supplying Vcc. After processing, the power supply unit outputs four voltages: VccAH, VccAL, VccBH, and VccBL, which power the output sides of the corresponding drive optocouplers (e.g., U98 controlling VgsAH, U97 controlling VgsAL, etc.). The drive signal input terminal receives four PWM signals (PWMAH, PWMAL, PWMBH, PWMBL) from the controller and connects them to the input terminals of the corresponding drive optocouplers. The output terminals are connected to capacitors (such as C53 and C54) and Zener diodes (such as DZ13 and DZ16) of the positive and negative voltage generation unit, converting the unipolar positive voltage into a bipolar voltage. After the bipolar voltage is converted, the positive and negative voltage range is limited by the reverse series Zener diodes (such as D61 and D63, D68 and D66, etc.) of the drive signal overvoltage protection unit, and then output to the gates (VgsAH, VgsAL, VgsBH, VgsBL) of the corresponding SiCMOSFETs in the H-bridge inverter circuit. At the same time, each circuit is connected to the corresponding ground terminal (GNDAH, GNDAL, GNDBH, GNDBL) and the common ground GND, forming a complete drive signal transmission and power supply circuit.

[0039] The input switch is sequentially connected to the uncontrolled rectifier circuit, DC support and filter capacitor, and H-bridge inverter circuit. The output of the H-bridge inverter circuit is connected to the isolation transformer. The secondary side of the isolation transformer is connected to the full-wave rectifier circuit and the output filter capacitor, ultimately forming a DC output. The DC / DC converter power supply draws power from the welding machine's DC bus and outputs low-voltage DC to power the drive circuit. The controller outputs four PWM signals (PWMAH, PWMAL, PWMBH, PWMBL) to the drive circuit. After processing, the drive circuit connects to the gates of the four SiC MOSFETs in the H-bridge inverter circuit (corresponding to VgsAH, VgsAL, VgsBH, VgsBL), and the sources of each MOSFET are connected to the corresponding ground terminals (GNDAH, GNDAL, GNDBH, GNDBL), thereby realizing the drive control of the H-bridge inverter circuit.

[0040] The working principle is as follows:

[0041] The welding machine power supply has a 380V AC input and a 10-30V DC output. The DC / DC converter transforms the approximately 530V high-voltage DC bus voltage to 15V as Vcc. In the drive circuit, the power supply unit obtains the supply voltage Vcc from the DC / DC converter as input, forming four outputs: VccAH, VccAL, VccBH, and VccBL, which supply 24V DC to the four drive optocoupler outputs. The drive optocoupler matrix unit in the drive circuit obtains four PWM signals from the controller as input signals: PWMAH, PWMAL, PWMBH, and PWMBL, which are used to control the four SiC MOSFETs of the H-bridge inverter. The positive and negative voltage generation unit in the drive circuit converts the four unipolar positive voltages of 24V provided by the power supply unit into four positive voltages of 18.9V and four negative voltages of 5.1V. The drive signal overvoltage protection unit in the drive circuit prevents excessive positive and negative voltages of the drive signal through a reverse series Zener diode; the positive voltage limit is 24V, and the negative voltage limit is -6.8V. Ultimately, the PWM turn-on high level of the SiC material MOSFET in the H-bridge inverter is 18.9V, and the turn-off negative level is -5.1V.

[0042] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0043] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A SiC welding power supply drive circuit, characterized in that, It includes a power supply unit, a drive optocoupler matrix unit, a positive and negative voltage generation unit, and a drive signal overvoltage protection unit; The power supply unit receives the output voltage Vcc from the DC / DC conversion module and outputs four isolated DC voltages through a push-pull transformer and a full-wave rectifier circuit to power the drive optocoupler matrix unit. The drive optocoupler matrix unit receives four PWM signals from the controller, achieves signal isolation and shaping through a general-purpose optocoupler, and outputs them to the positive and negative voltage generation unit. The positive and negative voltage generating unit converts unipolar positive voltage into bipolar driving voltage through a circuit composed of a Zener diode and a capacitor. The drive signal overvoltage protection unit limits the positive and negative voltage range of the drive signal through a reverse-connected Zener diode and is connected to the SiCMOSFET gate of the H-bridge.

2. The SiC welding power supply drive circuit according to claim 1, characterized in that, The power supply unit includes a self-resonant controller, switching transistors U89 and U90, capacitors C50 and C51, transformers T7 and T8, and four rectifier and filter modules. The four rectifier and filter modules have identical structures, and one of them includes diodes D61, D62, D63, D64, and capacitor C53. The drive optocoupler matrix unit contains four drive optocoupler modules, all with identical structures, connected to the four rectifier and filter modules. One of these drive optocoupler modules includes an optocoupler chip U98, resistor R82, and capacitor C7.

2. The positive and negative voltage generation unit contains four positive and negative voltage generation circuits, all with the same structure, and is connected to four driving optocoupler modules respectively. One of the positive and negative voltage generation circuits includes resistors R68 and R66, capacitors C58 and C59, and diode DZ15. The drive signal overvoltage protection unit contains four drive signal overvoltage protection circuits, all with the same structure, and is connected to four positive and negative voltage generation circuits respectively. One of the drive signal overvoltage protection circuits includes diodes DZ13 and DZ14, resistor R67, and capacitor C57.

3. The SiC welding power supply drive circuit according to claim 1, characterized in that, The power supply unit has an input voltage Vcc of 15V and outputs four DC voltages of 24V each, corresponding to the upper bridge arm A, lower bridge arm A, upper bridge arm B, and lower bridge arm B of the H-bridge, respectively.

4. The SiC welding power supply drive circuit according to claim 1, characterized in that, The drive optocoupler matrix unit uses a general-purpose optocoupler, TLP250, which receives PWM signals with a frequency of 10-20kHz and a duty cycle of 0-90%.

5. The SiC welding power supply drive circuit according to claim 1, characterized in that, The conversion parameters of the positive and negative voltage generation unit are as follows: converting 24V unipolar positive voltage to 18.9V positive voltage as the turn-on voltage and -5.1V negative voltage as the turn-off voltage. The Zener diode is BZX55C6V8 and the capacitor is 10μF / 50V.

6. The SiC welding power supply drive circuit according to claim 1, characterized in that, The positive voltage limit of the drive signal overvoltage protection unit is 24V, and the negative voltage limit is -6.8V. It uses a BZX55C24 positive voltage regulator and a BZX55C6V8 negative voltage regulator connected in reverse series.

7. A SiC welding power supply system, characterized in that, It includes an input switch, a rectifier circuit, a DC support and filter capacitor, an H-bridge inverter circuit, an isolation transformer, an output rectifier and filter circuit, and a drive circuit as described in any one of claims 1-6, connected in sequence; the drive circuit is connected to the controller and the SiCMOSFET of the H-bridge inverter circuit to realize driving and protection.

8. The SiC welding power supply system according to claim 7, characterized in that, The rectifier circuit is a three-phase rectifier circuit, including diodes D55, D56, D57, D58, D59, and D60. The H-bridge inverter circuit includes MOSFETs U76, U77, U78, and U79. The DC support and filter capacitor is capacitor C36. The output rectifier and filter circuit includes diodes D21 and D22. The anode of diode D55 is connected to the cathode of diode D59 and the input switch. The anode of diode D58 is connected to the cathode of diode D57 and the input switch. The anode of diode D56 is connected to the cathode of diode D55 and the input switch. The cathode of diode D60 is connected to the cathodes of diodes D58 and D56, capacitor C36, the drain of MOSFET U77, and the drain of MOSFET U77. The anode of diode D59 is connected to the anodes of diodes D57 and D55, the other end of capacitor C36, the source of MOSFET U78, and the MOSFET U79 source. The source of MOSFET U77 is connected to the drain of MOSFET U76, the drive circuit, and the primary winding of the isolation transformer. The source of MOSFET U78 is connected to the drain of MOSFET U79, the drive circuit, and the other end of the primary winding of the isolation transformer. The secondary winding of the isolation transformer is connected to diodes D21 and D22 respectively.

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