Plasma torch power supply module realized based on parallel connection of multiple silicon carbide devices and control method thereof

Abstract

The invention discloses a plasma torch power supply module realized based on parallel connection of multiple silicon carbide devices and a control method thereof, and belongs to the technical field of plasma torch power supplies. A plasma torch power supply module realized based on parallel connection of multiple silicon carbide devices comprises an input rectification filtering unit used for converting three-phase AC input into DC bus voltage; the chopping module is connected between the direct-current bus voltage and the output end and comprises N chopping units which are arranged in parallel; each chopping unit comprises a silicon carbide MOSFET (Metal-Oxide-Semiconductor Field Effect Transistor) as a switching tube, a silicon carbide diode as a freewheeling tube and a branch filter inductor; the N chopping units operate in a phase-shifting interleaving parallel mode; the output filtering unit is used for filtering the current converged by the N chopping units and outputting the filtered current to a load; the sampling unit is configured to collect a total output current signal of the power supply module and a branch current signal of each chopping unit; and the controller is connected with the sampling unit and the chopping module, and is used for receiving the total output current signal and the branch current signal, and outputting PWM (Pulse Width Modulation) driving signals with staggered phases to the silicon carbide MOSFETs according to a current sharing control algorithm.

Description

Technical Field

[0001] This invention relates to the field of plasma torch power supply technology, specifically to a plasma torch power supply module and its control method based on parallel connection of multiple silicon carbide devices. Background Technology

[0002] Plasma torches, as a high-energy heat source, are widely used in materials cutting, spraying, waste treatment, and metallurgical smelting. Due to the strong nonlinearity and negative resistance characteristics of plasma loads, their power supply systems need to have high voltage, high current, and fast dynamic response capabilities.

[0003] Traditional plasma torch power supplies mostly use silicon-based devices (such as silicon MOSFETs or IGBTs) as switching elements. However, due to the physical properties of silicon, the switching frequency of traditional devices is relatively low (usually within tens of kHz), resulting in large output current ripple. To meet process requirements, bulky output filter inductors and capacitors are often needed, which not only increases the size and weight of the equipment but also reduces the system's power density and dynamic response speed.

[0004] With the development of third-generation wide-bandgap semiconductor materials, silicon carbide (SiC) devices have become an ideal choice for high-power power supply designs due to their advantages such as high voltage resistance, high temperature resistance, low on-resistance, and fast switching speed. To further improve the power level of the power supply, multiple power devices are usually connected in parallel. However, in practical applications, direct parallel connection faces a serious "current sharing" problem. Due to parameter dispersion caused by device manufacturing processes (such as different on-resistance and threshold voltage), parasitic parameter differences caused by PCB traces, and delay errors in the drive circuit, the current distribution among the parallel branches is often uneven.

[0005] Uneven current distribution can cause devices carrying higher currents to overheat significantly. This temperature rise may trigger positive feedback (for some devices) or cause the device to reach its thermal limit and fail before other devices, thus limiting the overall output capability and reliability of the power module. Existing current sharing control methods either rely on complex hardware sampling circuits, which are costly, or have slow control algorithms that are difficult to adapt to extreme conditions such as plasma torch arcing and sudden load changes.

[0006] Therefore, there is an urgent need for a plasma torch power module and its control method that can fully utilize the high-frequency advantages of silicon carbide devices, effectively solve the current sharing problem of multiple tubes in parallel, and achieve high power density and low ripple output. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention proposes a plasma torch power supply module and its control method based on the parallel connection of multiple silicon carbide devices.

[0008] The objective of this invention can be achieved through the following technical solutions:

[0009] A first aspect of the present invention relates to a plasma torch power supply module based on parallel connection of multiple silicon carbide devices, comprising:

[0010] The input rectifier and filter unit is used to convert the three-phase AC input into DC bus voltage;

[0011] The chopper module, connected between the DC bus voltage and the output terminal, includes N chopper units connected in parallel; each chopper unit includes a silicon carbide MOSFET as a switching transistor, a silicon carbide diode as a freewheeling transistor, and a branch filter inductor; the N chopper units operate in a phase-shifted, interleaved parallel configuration.

[0012] An output filtering unit is used to filter the current after the N chopper units are combined and output it to the load;

[0013] The sampling unit is configured to collect the total output current signal of the power module and the branch current signal of each chopper unit;

[0014] In addition, a controller, connected to the sampling unit and the chopper module, is used to receive the total output current signal and the branch current signal, and output phase-shifted PWM drive signals to each of the silicon carbide MOSFETs according to the current sharing control algorithm.

[0015] Optionally, the chopper unit is configured as a Buck step-down topology; the drain of the silicon carbide MOSFET is connected to the positive terminal of the DC bus voltage, and the source is connected to the cathode of the silicon carbide diode and one end of the branch filter inductor; the anode of the silicon carbide diode is connected to the negative terminal of the DC bus voltage.

[0016] The input rectifier and filter unit has a varistor and a high-frequency decoupling capacitor connected in parallel between the positive and negative terminals of the DC bus voltage to absorb voltage spikes caused by line leakage inductance.

[0017] Optionally, it also includes a hardware protection circuit, the hardware protection circuit comprising:

[0018] A branch current independent sampling module is used to buffer and RC filter the current signals of each branch;

[0019] The high-voltage bus monitoring module is used to sample the DC bus voltage by voltage division and output a first hardware lockout signal when undervoltage or overvoltage is detected.

[0020] The total current simulation calculation module is configured to sum the current signals of each branch in the simulation domain to obtain a simulated total current signal, and compare the simulated total current signal with a preset overcurrent threshold. When the overcurrent threshold is exceeded, a second hardware latch signal is output.

[0021] When the controller or driver receives the first hardware latch signal or the second hardware latch signal, it directly blocks the PWM drive signal to the silicon carbide MOSFET.

[0022] Optionally, the total current simulation calculation module further includes a current loop error adjustment circuit, which is configured to receive the simulated total current signal and the external current given signal, and output the corresponding duty cycle control voltage to the controller through a hardware PI adjustment network.

[0023] Optionally, it also includes an isolated drive output module, which is connected between the controller and the silicon carbide MOSFET;

[0024] The isolated drive output module is configured to use a dual power supply to provide a positive voltage turn-on signal and a negative voltage turn-off signal to the gate of the silicon carbide MOSFET; and the isolated drive output module has a disable pin, which is connected to a hardware fault signal source to realize hardware-level drive cutoff.

[0025] A second aspect of the present invention relates to a control method for the power module described above, comprising the following steps:

[0026] S1: Real-time acquisition of the total output current of the power module and the branch currents of each of the N parallel chopper units. ;

[0027] S2: Based on the total output current With the current of each branch. The deviation is calculated using a preset current sharing algorithm to determine the duty cycle of each chopper unit. The current sharing algorithm is configured to reduce the duty cycle of a branch when the average share of the current in a branch relative to the total current is too large.

[0028] S3: Based on the calculated duty cycle N channels with the same frequency but staggered phase are generated. The PWM drive signals control the turn-on and turn-off of each of the silicon carbide MOSFETs.

[0029] Optionally, in step S2, the specific formula for the flow sharing algorithm is:

[0030]

[0031] in, Let x be the duty cycle control value for the x-th chopper unit. This is the gain coefficient. These are weighting coefficients; the controller will calculate the... Mapped to PWM pulse width.

[0032] Optionally, the gain coefficient The weighting coefficient is set to 1.25. Set to 4; and the controller has an upper limit threshold for the duty cycle control quantity, when the calculated value is... When the upper limit threshold is exceeded, the maximum duty cycle is forcibly output.

[0033] Optionally, in step S1, the branch current is... The acquisition includes continuously acquiring multiple sampling points and calculating the average value to filter out high-frequency switching noise; the total output current... The data acquisition involves redundant acquisition through multiple channels and taking the average or maximum value.

[0034] Optionally, fault protection steps may also be included:

[0035] The instantaneous values ​​of the current in all branches are monitored in real time by diode logic circuits. When the instantaneous value of the current in any branch exceeds the peak safety threshold, a hardware latching signal is triggered.

[0036] The controller counts the number of times the fault signal is triggered. When the number of triggers reaches a preset value within a preset time, it executes software locking and maintains a stopped state until a manual reset signal is received.

[0037] The beneficial effects of this invention are:

[0038] Compared with the prior art, the plasma torch power supply module and its control method based on parallel connection of multiple silicon carbide devices provided by the present invention have the following significant advantages:

[0039] 1. Excellent dynamic current sharing performance, enhancing system reliability. This invention implements a specific current sharing control algorithm through the controller, which calculates the deviation between the total output current and the current of each branch in real time, and dynamically adjusts the PWM duty cycle of each chopper unit accordingly. This algorithm constructs a negative feedback closed loop based on the average share of the total current. When the current of a branch is too large, its duty cycle is automatically reduced, and vice versa. This active control strategy effectively overcomes the problem of uneven current distribution caused by differences in device parameters and line impedance, prevents damage to individual silicon carbide devices due to overcurrent or overheating, and ensures long-term stable operation of multi-parallel modules under high temperature and high current conditions.

[0040] 2. Significantly Reduced Output Ripple, Achieving Power Supply Miniaturization. This invention employs an interleaved topology with N chopper units connected in parallel. By sequentially shifting the switching phases of each branch (e.g., 72 degrees for 5 parallel connections), ripple currents are mutually canceled at the total output, increasing the equivalent output ripple frequency to N times the single-transistor switching frequency (e.g., from 40kHz to an equivalent 200kHz). This not only significantly reduces the output current ripple amplitude and improves the process quality of plasma processing, but also significantly reduces the size and inductance requirements of the output filter inductor and capacitor, thereby achieving high power density and miniaturized design of the power module.

[0041] 3. High efficiency and low loss: Utilizing the low on-resistance of silicon carbide (SiC) MOSFETs. With its extremely short switching time, this invention achieves high-frequency chopping while significantly reducing switching and conduction losses. Combined with the aforementioned current sharing control, it prevents any single transistor from operating in an inefficient or overheated region, thereby significantly improving the overall power module's energy conversion efficiency and reducing the design burden on the cooling system.

[0042] 4. Flexible modular expansion capability: The control method of this invention is based on normalized current deviation adjustment (using coefficients). and This architecture boasts excellent portability and scalability. It is not limited to a specific number of parallel units, allowing for easy adjustment of the number of parallel chopper units based on load power requirements. This provides a universal hardware architecture and software algorithm foundation for developing a series of plasma power supply products with different power levels. Attached Figure Description

[0043] The invention will now be further described with reference to the accompanying drawings.

[0044] Figure 1 This is a schematic diagram of the main circuit of the power module in this application;

[0045] Figure 2 This is a schematic diagram of the DSP sampling and control structure of this application;

[0046] Figure 3 This is a schematic diagram of the DSP fault control structure of this application;

[0047] Figure 4 This is a schematic diagram of the silicon carbide MOSFET IV2Q12017T4Z package of this application;

[0048] Figure 5 This is a schematic diagram of the 60A / 1200V silicon carbide diode package of this application. Detailed Implementation

[0049] 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.

[0050] In some embodiments of the present invention, such as Figure 1 As shown, a power control system consisting of five chopper modules connected in parallel is disclosed. It is equipped with a high-power DC power supply main circuit, adopts a three-phase AC rectified input, and is connected to a multi-channel interleaved parallel Buck step-down chopper circuit. Five independent silicon carbide chopper units are used for phase shifting and parallel connection to achieve high-frequency, low-ripple, high-current output.

[0051] The circuit may include an input rectifier and filter stage, a chopper module, and an output filter stage.

[0052] The input rectifier and bus filter stage is responsible for converting the three-phase AC power into a stable DC bus voltage (HV+). The rectifier bridge input is connected to the three-phase AC power supply, and through a three-phase full-bridge rectifier circuit composed of six diodes, it outputs pulsating DC power.

[0053] A varistor (511KD) is connected in parallel between the positive and negative buses of the rectifier output to absorb surge voltage. A resistor (200kΩ / 10W) is connected in parallel between the positive and negative buses for capacitor voltage equalization and charge discharge after power failure. A large-capacity electrolytic capacitor (300μF / 800V) is connected in parallel between the positive and negative buses to smooth the DC voltage. A high-frequency filter capacitor and a non-inductive capacitor (25μF / 1kV) are connected next to the large capacitor to filter out high-frequency interference. The RC absorption circuit includes a resistor (10Ω / 200W) and a capacitor, connected in series across the two ends of the bus to suppress bus voltage oscillations and spikes.

[0054] The chopper module consists of five chopper units (chopper unit 1 to chopper unit 5) connected in parallel. The input terminals of all chopper units are connected in parallel to the DC bus (HV+), and the output terminals are connected to the total output filter inductor after being combined.

[0055] In a single chopper unit (taking unit 1 as an example), a high-frequency capacitor (with parameters of 5uF / 1.2kV) is placed close to the unit input terminal (i.e., between the MOSFET drain and ground) to absorb voltage overshoot during switching operation and reduce the influence of stray inductance.

[0056] The drain of the switching transistor (SiC MOSFET) is connected to the positive terminal (HV+) of the DC bus; the source serves as the chopper output node. A silicon carbide MOSFET is used. The cathode of the freewheeling diode (SiC diode) is connected to the source of the MOSFET; the anode is connected to the negative terminal (GND) of the DC bus. A silicon carbide diode with parameters of 40A / 1200V is used.

[0057] One end of the branch filter inductor (L) is connected to the common point between the MOSFET source and the diode cathode; the other end serves as the output of this unit. A branch current sensor (I1) is connected in series along the path of the branch filter inductor to acquire the real-time current (I1) of that branch. The total filter inductor is connected in series between the bus node and the load. The total current sensor is located after the total filter inductor and before the load; its range is 220A / 1kVdc, and it is used to provide feedback on the total output current. The external load is connected between the output and ground.

[0058] Three-phase AC power (such as 520V input) is rectified by a rectifier bridge and then filtered by a bus capacitor to form DC voltage. Due to the high input voltage (peak value can reach about 808V), the DC bus voltage (HV+) is high voltage DC.

[0059] Each chopper unit operates in Buck mode. During the turn-on phase, when the DSP controller sends a high-level drive signal, the SiC MOSFET turns on. Current flows from HV+ through the MOSFET and the branch inductor to the load. At this time, the inductor stores energy, and the diode is cut off. During the turn-off phase, the MOSFET turns off. Since the inductor current cannot change abruptly, the branch inductor generates an induced electromotive force, forcing the freewheeling diode (SiC Diode) to turn on. Current continues to flow from ground through the diode and the branch inductor to the load (freewheeling).

[0060] In this embodiment, although the five chopper units have the same structure, their switching drive signals are staggered in phase.

[0061] The switching frequency of each unit is 40kHz.

[0062] The phase difference of the drive signals of adjacent units is .

[0063] At the total output, the ripple currents of each branch cancel each other out. The ripple frequency of the total output current increases to... Furthermore, the ripple amplitude is significantly reduced (ripple current is less than 10A).

[0064] Thanks to the use of silicon carbide devices, the circuit can withstand higher voltages (1200V withstand voltage to cope with overshoot caused by the 808V bus and leakage inductance) and can operate at high frequencies with low losses. A 5uF local decoupling capacitor is specifically designed to address voltage spikes during high-frequency switching.

[0065] With the above structure, the circuit realizes the function of converting high-voltage AC input into high-current (200A), low-ripple DC output, and has the ability to disperse thermal stress through parallel current sharing.

[0066] In other embodiments of the present invention, a DSP control board is disclosed, which controls five silicon carbide transistors, outputting five PWM outputs plus one backup output; five fault protection outputs that promptly shut down the PWM outputs when the silicon carbide driver or silicon carbide transistors malfunction; the five silicon carbide transistors are connected in parallel to output 200A; the module operates in constant current mode; it uses Ethernet communication and supports the Siemens Profinet communication protocol (Siemens S7-1200 PLC);

[0067] Software fault diagnosis requirements:

[0068] Silicon carbide overcurrent protection: protection occurs when the output is high, and normal operation occurs when the output is low;

[0069] IPM module over-temperature protection: high level for over-temperature protection, low level for normal operation;

[0070] Hardware failure requirements:

[0071]

[0072] Analog sampling input:

[0073]

[0074] Hardware protection requirements:

[0075] All five current sampling channels require hardware overcurrent protection.

[0076] Specifically, with reference Figure 2 As shown, the DSP sampling and control module mainly includes: a branch current independent sampling module, a high-voltage bus monitoring and protection module, and a total current simulation calculation and hardware protection module.

[0077] The independent branch current sampling module is responsible for sampling the five branch current signals output by the chopper module. to The signal is buffered and conditioned before being sent to the DSP for A / D conversion.

[0078] The input stage of this module contains 5 independent input terminals, each corresponding to... to Each input signal (nominal 2V / 40A) first passes through an RC low-pass filter network. The signal is connected in series with two... A resistor is connected in parallel to ground at the junction of the two resistors. A capacitor, with another capacitor connected in parallel to ground after the second resistor. Capacitors (to form a second-order or multi-stage RC filter).

[0079] This module is equipped with a buffer stage for the filtered signal to be input to the non-inverting input (+) of the operational amplifier. The operational amplifier is configured as a voltage follower, meaning its output is directly shorted to the inverting input (-).

[0080] In the output stage of this module, signals are respectively led out from the output terminals of the operational amplifiers. to It is directly connected to the analog sampling pin of the DSP. The diagram shows that a total of 6 A / D acquisition channels are required, of which 5 channels are used for the branch current here.

[0081] The high-voltage bus monitoring and protection module is used to directly monitor the DC bus voltage ( It also outputs a hardware blocking signal (DRV-DIS) when the voltage is abnormal. This module mainly includes a voltage divider sampling network and a voltage monitoring chip (MC3425).

[0082] The voltage divider sampling network consists of a series of high-resistance resistors connected in series. The high-side includes seven resistors connected in series. Resistor, connected to ; lower side by series resistors The resistor is composed of a resistor and ground.

[0083] Sampling points at resistor chain and A sampling voltage is drawn from the connection point of the resistor and connected in parallel with a... Filter capacitors.

[0084] The voltage monitoring chip (MC3425) is used to sample the voltage connected to the detection pin of the MC3425 chip. The chip is equipped with a delay capacitor ( The chip output is connected to an optocoupler (or a similar isolated driver interface) and a reference voltage setting. The output signal is DRV-DIS.

[0085] A voltage below 550V for approximately 4ms is considered undervoltage; a voltage above 850V for approximately 2ms is considered overvoltage. When protection is triggered, the DRV-DIS signal activates, shutting down the chopper module.

[0086] The total current simulation and closed-loop control interface module performs the summation, averaging, comparison with a given value, and hardware overcurrent protection of the five current channels at the hardware level. This module includes an analog summation circuit, a 5% current limiting protection circuit, and a current loop error amplification / adjustment circuit.

[0087] The analog summing circuit inputs the current signals from the five branches ( ) respectively through one The resistors converge at a single node and are connected to the non-inverting input (+) of the operational amplifier. A resistor is connected in parallel with ground at the non-inverting input. Capacitors. The op-amp is configured as a non-inverting amplifier or adder, and the feedback loop includes... Resistor. This circuit is used to combine five separate current signals into a single voltage signal representing the total output current in the analog domain.

[0088] In the 5% current limiting protection circuit, the summed total current signal is connected to the non-inverting input (+) of the comparator operational amplifier. The inverting input (-) is connected to a... Voltage divider reference source for power supply ( Pull up, drop down, (Fine-tuning). The op-amp output is via a diode (HSMS-282x). When the total current signal exceeds the set reference threshold (corresponding to a 5% overcurrent margin), the op-amp output goes high, triggering hardware protection.

[0089] The input terminal of the current loop error amplifier / adjustment circuit can be configured with:

[0090] Inverting input (-): Receives the total current feedback signal from the summing circuit (via...) resistance).

[0091] Non-inverting input (+): Receives the external current reference signal Iref (via...) Resistance, and has (Capacitance to ground).

[0092] In the feedback network of this circuit, an RC feedback network is connected between the op-amp output and the inverting input. series resistors Capacitors, in parallel The capacitor constitutes the PI (proportional-integral) regulation characteristic.

[0093] In the output stage of this circuit, the op-amp output is divided by resistors ( Series, After connecting to ground and the limiting diode, the output signal is A / D-Io.

[0094] The signal ( This directly corresponds to the PWM duty cycle (0-1). After the DSP acquires this signal, it can be directly used to calculate the total drive pulse width.

[0095] like Figure 3 As shown, the DSP fault control mainly includes a multi-channel peak current detection and logic synthesis module, a comprehensive fault lockout control module, and an isolated drive output module. Its main function is to drive silicon carbide MOSFETs and quickly cut off the drive signal in the event of overcurrent, overvoltage, or overtemperature.

[0096] The multi-channel peak current detection and logic synthesis module is used to monitor the instantaneous values ​​of the current in the five branches in real time.

[0097] The input network is configured as follows:

[0098] It has 5 input terminals, corresponding to 5 branch current signals respectively. to The ratio is 2V to 40A.

[0099] Each input terminal is connected to the anode of a Schottky diode (model HSMS-282x).

[0100] The cathodes of all five diodes are connected together to form a common junction point, which constitutes a logic OR circuit. As long as the voltage of any one current signal increases, the potential of the common junction will also increase.

[0101] This module is equipped with a threshold comparison circuit (TL431), and the common bus point is connected via a... The resistor is connected to the cathode of the adjustable precision shunt regulator (TL431A). The reference terminal (Ref) of the TL431A is connected via a voltage divider resistor (pull-up). ,drop down in parallel Capacitor) set threshold. When any current exceeds the set threshold ( When the TL431A operates, it triggers subsequent protection logic.

[0102] The integrated fault interlocking control module is responsible for collecting data from current detection and voltage detection (…). Figure 2 It introduces fault signals for temperature detection and generates a unified disable signal (DIS).

[0103] In this module, fault signal aggregation can be based on the following inputs:

[0104] Overvoltage input: from Figure 2 The overvoltage protection DRV-DIS signal is connected via a diode.

[0105] Overcurrent input: The output from the aforementioned TL431A circuit is connected to the voltage detector (M51958B).

[0106] Over-temperature input: An over-temperature protection switch (normally open contact) is installed on the radiator. (Closed). One end of the switch is connected to... The other end is through The resistor is connected to the fault bus.

[0107] In the delay and reset control function, the M51958B chip serves as the core of the fault logic processing.

[0108] The chip is equipped with a timing capacitor ( ), used to set the delay recovery time after a fault (delay 200us recovery).

[0109] A signal is output from the chip to the DSP for fault counting. The logic is set so that the DSP detects a rising edge and counts; after accumulating 5 rising edges, the DSP software locks and issues an alarm.

[0110] The chip output is connected to the DIS pin of the driver chip via a diode.

[0111] The isolated drive output module uses an isolated gate driver to directly control the turn-on and turn-off of the silicon carbide MOSFET.

[0112] The input side of the driver chip (UCC21520) for this module is configured with:

[0113] Pin 1 (INA): Receives PWM drive signals from the DSP.

[0114] Pin 5 (DIS): Receives a combined fault latch signal from the aforementioned modules. When this pin is high, the chip immediately stops outputting.

[0115] The module's output side uses a dual power supply: VDD is +18VDC, and VSS is -3VDC. The positive and negative voltage drive (+18V / -3V) is a typical driving method for silicon carbide MOSFETs; the negative voltage is used to prevent false turn-on and accelerate turn-off. A voltage is connected in parallel between the MOSFET's gate and source. The pull-down resistor is used to prevent the gate from floating and accumulating charge.

[0116] In some embodiments of the present invention, the current reference Iref comes from the control outer loop; three channels sample A / D-Io (abbreviated as I). o Calculate the average value (taking the maximum value as 2.9V), sample A / D-Ix from five channels (X=1,2……5), and calculate the average value for each sample (the average value is called I). px (X=1,2……5). Calculate the duty cycle of the corresponding five PWM channels: 1.25*(I) o -I px / 4), its value of 0.2-3V corresponds to the duty cycle of each PWM output being 0-1, and when >2.95V, D=1 is taken.

[0117] It is important to note that with a rated three-phase input of 520V and a maximum overvoltage of 572V (10% overvoltage), the rectified voltage at 520V is 520*1.35=702V. With a rated DC output current of 200A, the minimum low-voltage distribution capacity required by the distribution network is 700*200=140kVA. If the grid line voltage is 520V with a 4% short-circuit voltage drop, the minimum short-circuit capacity of the distribution network is 3.5MVA. The maximum leakage inductance per phase of the AC input is approximately 240uH. When the MOSFET is turned off, the maximum two-phase leakage inductance of 2*240=480uH may charge the DC bus capacitor after rectification, potentially causing the voltage to exceed 1200V and damaging the 1200V-rated MOSFET.

[0118] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0119] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.

Claims

1. A plasma torch power supply module based on parallel connection of multiple silicon carbide devices, characterized in that, include: The input rectifier and filter unit is used to convert the three-phase AC input into DC bus voltage; The chopper module, connected between the DC bus voltage and the output terminal, includes N chopper units connected in parallel; each chopper unit includes a silicon carbide MOSFET as a switching transistor, a silicon carbide diode as a freewheeling transistor, and a branch filter inductor; the N chopper units operate in a phase-shifted, interleaved parallel configuration. An output filtering unit is used to filter the current after the N chopper units are combined and output it to the load; The sampling unit is configured to collect the total output current signal of the power module and the branch current signal of each chopper unit; In addition, a controller, connected to the sampling unit and the chopper module, is used to receive the total output current signal and the branch current signal, and output phase-shifted PWM drive signals to each of the silicon carbide MOSFETs according to the current sharing control algorithm.

2. The plasma torch power supply module based on parallel connection of multiple silicon carbide devices according to claim 1, characterized in that, The chopper unit is configured with a Buck step-down topology; the drain of the silicon carbide MOSFET is connected to the positive terminal of the DC bus voltage, and the source is connected to the cathode of the silicon carbide diode and one end of the branch filter inductor; the anode of the silicon carbide diode is connected to the negative terminal of the DC bus voltage. The input rectifier and filter unit has a varistor and a high-frequency decoupling capacitor connected in parallel between the positive and negative terminals of the DC bus voltage to absorb voltage spikes caused by line leakage inductance.

3. The plasma torch power supply module based on parallel connection of multiple silicon carbide devices according to claim 1, characterized in that, It also includes a hardware protection circuit, which includes: A branch current independent sampling module is used to buffer and RC filter the current signals of each branch; The high-voltage bus monitoring module is used to sample the DC bus voltage by voltage division and output a first hardware lockout signal when undervoltage or overvoltage is detected. The total current simulation calculation module is configured to sum the current signals of each branch in the simulation domain to obtain a simulated total current signal, and compare the simulated total current signal with a preset overcurrent threshold. When the overcurrent threshold is exceeded, a second hardware latch signal is output. When the controller or driver receives the first hardware latch signal or the second hardware latch signal, it directly blocks the PWM drive signal to the silicon carbide MOSFET.

4. The plasma torch power supply module based on parallel connection of multiple silicon carbide devices according to claim 3, characterized in that, The total current simulation calculation module also includes a current loop error adjustment circuit, which is configured to receive the simulated total current signal and the external current given signal, and output the corresponding duty cycle control voltage to the controller through a hardware PI adjustment network.

5. The plasma torch power supply module based on parallel connection of multiple silicon carbide devices according to claim 1, characterized in that, It also includes an isolated drive output module, which is connected between the controller and the silicon carbide MOSFET; The isolated drive output module is configured to use a dual power supply to provide a positive voltage turn-on signal and a negative voltage turn-off signal to the gate of the silicon carbide MOSFET; and the isolated drive output module has a disable pin, which is connected to a hardware fault signal source to realize hardware-level drive cutoff.

6. A control method for a power module according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Real-time acquisition of the total output current of the power module and the branch currents of each of the N parallel chopper units. ; S2: Based on the total output current With the current of each branch. The deviation is calculated using a preset current sharing algorithm to determine the duty cycle of each chopper unit. The current sharing algorithm is configured to reduce the duty cycle of a branch when the average share of the current in a branch relative to the total current is too large. S3: Based on the calculated duty cycle N channels with the same frequency but staggered phase are generated. The PWM drive signals control the turn-on and turn-off of each of the silicon carbide MOSFETs.

7. The control method according to claim 6, characterized in that, In step S2, the specific formula for the flow sharing algorithm is as follows: ； in, Let x be the duty cycle control value for the x-th chopper unit. This is the gain coefficient. These are weighting coefficients; the controller will calculate the... Mapped to PWM pulse width.

8. The control method according to claim 7, characterized in that, The gain coefficient The weighting coefficient is set to 1.

25. Set to 4; and the controller has an upper limit threshold for the duty cycle control quantity, when the calculated value is... When the upper limit threshold is exceeded, the maximum duty cycle is forcibly output.

9. The control method according to claim 6, characterized in that, In step S1, the branch current is... The acquisition includes continuously acquiring multiple sampling points and calculating the average value to filter out high-frequency switching noise; the total output current... The data acquisition involves redundant acquisition through multiple channels and taking the average or maximum value.

10. The control method according to claim 6, characterized in that, It also includes fault protection steps: The instantaneous values ​​of the current in all branches are monitored in real time by diode logic circuits. When the instantaneous value of the current in any branch exceeds the peak safety threshold, a hardware latching signal is triggered. The controller counts the number of times the fault signal is triggered. When the number of triggers reaches a preset value within a preset time, it executes software locking and maintains a stopped state until a manual reset signal is received.

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