CN106735800B

CN106735800B - Plasma cutting machine pilot arc electron current-limiting resistance circuit

Info

Publication number: CN106735800B
Application number: CN201710159101.7A
Authority: CN
Inventors: 周江业; 崔东
Original assignee: ZHEJIANG SAFUN INDUSTRIAL CO LTD
Current assignee: ZHEJIANG SAFUN INDUSTRIAL CO LTD
Priority date: 2017-03-17
Filing date: 2017-03-17
Publication date: 2022-04-01
Anticipated expiration: 2037-03-17
Also published as: CN106735800A

Abstract

The invention discloses a pilot arc electronic current-limiting resistance circuit of a plasma cutting machine, which comprises a rectifying filter circuit, a filter output circuit, an auxiliary power circuit, a frequency configuration circuit, a current-limiting circuit, a field-effect tube Q1, an integrated chip U2, a first current sampling circuit, a first filter circuit and a follow current circuit. The invention can well replace the relay and the low-efficiency current-limiting resistor in the prior art, so that the replaced circuit is more stable and reliable, the loss in the circuit operation process is reduced, and the working efficiency of maintaining the arc is improved.

Description

Plasma cutting machine pilot arc electron current-limiting resistance circuit

Technical Field

The invention relates to a circuit topology structure of a power electronic technology and a welding and cutting power supply, in particular to a pilot arc electronic current-limiting resistance circuit of a plasma cutting machine.

Background

A plasma arc cutting machine is a machine for processing a metal material by means of a plasma cutting technique. The pilot arc device in the plasma cutting machine can ensure that the energy consumption of the plasma cutting machine is reduced under the non-cutting work, the electrode burning loss is reduced, and the service life of the plasma cutting machine is prolonged. During the arc maintenance period, the arc maintenance device of the plasma cutting machine can adjust the small air flow passing through the second electromagnetic valve, so that the arc maintenance period is more continuous, the noise is low, and the reliability is better. However, since the arc maintaining function is usually realized by connecting a high-power fixed-resistance power resistor and a relay switch to the nozzle in parallel at the positive end of the power supply, the power resistor has large voltage and current during arc maintaining, so that the power resistor generates heat seriously and is easy to damage due to overheating. Therefore, in order to lower the operating temperature of the power resistor to improve the reliability thereof, the power level of the power resistor must be increased and a stronger heat dissipation and cooling system must be designed, which increases the arc maintenance cost. Secondly, the resistance value of the power resistor is fixed and unchanged during arc maintenance, and the power loss is also fixed and unchanged, so that the working efficiency of the arc maintenance only reaches fifty percent, and the serious waste of resources is caused.

Disclosure of Invention

Aiming at the defects of high pilot arc cost, low working efficiency, easy overheat and damage of a power resistor and the like in the prior art, the invention provides a novel pilot arc electronic current-limiting resistor circuit of a plasma cutting machine.

In order to solve the technical problems, the invention is realized by the following technical scheme:

the plasma cutting machine pilot arc electronic current-limiting resistance circuit comprises a rectifying filter circuit and a filter output circuit, wherein two ends of the rectifying filter circuit are respectively connected with an OUT + end and an OUT-end, two ends of the filter output circuit are respectively connected with a QDH end and an OUT-end, the plasma cutting machine pilot arc electronic current-limiting resistance circuit further comprises an auxiliary power supply circuit, a frequency configuration circuit, a current-limiting circuit, a field-effect tube Q1, an integrated chip U2, a first current sampling circuit, a first filter circuit and a follow current circuit, the field-effect tube Q1 comprises three paths, the OUT end of the integrated chip U2 is connected with a first path of the field-effect tube Q1 through the current-limiting circuit, the rectifying filter circuit is connected with a second path of the field-effect tube Q1, a SEN end of the integrated chip U2 is connected with a third path of the integrated chip U2 through the first filter circuit, and the other path is connected with the first current sampling circuit, the OUT + end and the OUT end of the follow current circuit, The follow current circuit is connected with the QDH end, the frequency configuration circuit is respectively connected with the RT/CT end, the GND end and the VREF end of the integrated chip U2, and the auxiliary power supply circuit is connected with the VCC end of the integrated chip U2.

The OUT + end and the OUT-end are respectively and correspondingly connected to the output positive electrode and the output negative electrode of the plasma cutting machine, and the QDH end and the OUT-end are the positive electrode and the negative electrode output by the pilot arc electronic current-limiting resistor circuit. The rectifying and filtering circuit can rectify and filter input voltage and then use the rectified and filtered voltage as a direct current bus power supply of the pilot arc electronic current-limiting resistor circuit, the auxiliary power supply circuit can provide power for the integrated chip U2, so that the integrated chip U2 is electrified to work, the integrated chip U2 is a fixed-frequency current mode controller, the frequency configuration circuit is used for configuring the fixed frequency of the integrated chip U2, the OUT end of the integrated chip U2 is a control signal output end, and the output current is limited by the current-limiting circuit and then used for controlling the on and off of the field effect transistor Q1. When the field effect transistor Q1 is switched on, the input voltage is output to the QDH end through field effect transistor Q1 behind the rectification filter circuit, first current sampling circuit, the afterflow circuit, first current sampling circuit samples the electric current and send to the SEN end of integrated chip U2 after filtering through first current sampling circuit, after the electric current surpassed the threshold value of the SEN end of integrated chip U2, thereby the OUT end of integrated chip U2 closes output current and makes field effect transistor Q1 turn-off, and the afterflow circuit can carry OUT the afterflow to the output after field effect transistor Q1 is shut off, guarantee the stability of output. Through above structure, can enough guarantee the stability when maintaining the arc, can reduce the power loss when maintaining the arc again, promote the work efficiency of maintaining the arc, and need not to be equipped with extra heat dissipation cooling system, reduced manufacturing cost.

Preferably, the rectifier filter circuit includes a power diode D3, a capacitor C1, a capacitor C9, a capacitor C10, and a capacitor C6, after the capacitor C1, the capacitor C9, the capacitor C10, and the capacitor C6 form a parallel circuit, one end of the parallel circuit is connected to the output end of the power diode D3, the other end of the parallel circuit is connected to the OUT-terminal, the input end of the power diode D3 is connected to the OUT + terminal, and the output end of the power diode D3 is further connected to the second circuit of the field-effect transistor Q1.

The rectifying and filtering circuit formed by the elements can play a better filtering role, so that the circuit is more stable.

Preferably, the filter output circuit comprises resistors R19, R20, R21 and a capacitor C7, the resistor R19, the resistor R20 and the resistor R21 form a series circuit and then are connected in parallel with the capacitor C7, one end of the capacitor C7 is connected with the QDH end, and the other end of the capacitor C7 is connected with the OUT-end.

The filter output circuit formed by the elements can play a better filtering role, so that the output current is more stable, and the circuit is more stable.

Preferably, the auxiliary power circuit comprises an auxiliary power supply terminal YH1, a diode D1, a capacitor C3 and a capacitor C4, wherein an input terminal of the diode D1 is connected to an anode of the auxiliary power supply terminal YH1, an output terminal of the diode D1 is connected to a VCC terminal of an integrated chip U2, and after the capacitor C3 and the capacitor C4 form a parallel circuit, one end of the parallel circuit is connected to the VCC terminal of the integrated chip U2, and the other end of the parallel circuit is connected to a GNDB terminal.

The auxiliary power supply terminal YH1 is used for providing an auxiliary voltage, and is rectified and filtered by the diode D1, the capacitor C3, and the capacitor C4, and then is input to the VCC terminal of the integrated chip U2, so that the provided auxiliary voltage is more stable.

Preferably, the frequency configuration circuit comprises a capacitor C2, a resistor R3 and a capacitor C8, one end of the capacitor C2 is connected with the GNDB end, the other end of the capacitor C2 is connected with the VREF end of the integrated chip U2, one end of the resistor R3 is connected with the VREF end of the integrated chip U2, the other end of the resistor R3 is connected with the RT/CT end of the integrated chip U2, one end of the capacitor C8 is connected with the RT/CT end of the integrated chip U2, and the other end of the capacitor C8 is connected with the GND end of the integrated chip U2.

The resistor R3 and the capacitor C8 are used for setting the working frequency of the integrated chip U2, and the capacitor C2 filters VREF of the integrated chip U2, so that the working frequency of the U2 is more stable.

Preferably, the current limiting circuit of the pilot arc electronic current limiting resistor circuit of the plasma cutting machine comprises a resistor R8, and the first path of the field effect transistor Q1 is connected with the OUT terminal of the integrated chip U2 through a resistor R8.

The resistor R8 can prevent the current in the circuit from being too large, thereby better protecting the stability of the circuit.

Preferably, in the above plasma cutting machine pilot arc electronic current-limiting resistor circuit, the first current sampling circuit includes a resistor R9 and a resistor R11, the resistor R9 and the resistor R11 form a parallel circuit, and then one end of the parallel circuit is connected to the third path of the fet Q1, and the other end of the parallel circuit is connected to the freewheeling circuit.

Can have certain cushioning effect to the electric current through above structure, guarantee that current change is little in a certain time, guarantee promptly that the electric current is more stable often in the sampling.

Preferably, the first filter circuit comprises a resistor R4 and a capacitor C5, one end of the resistor R4 is connected to the SEN end of the integrated chip U2, the other end of the resistor R4 is connected to the third path of the fet Q1, one end of the capacitor C5 is connected to the SEN end of the integrated chip U2, and the other end of the capacitor C5 is connected to the GNDB end.

Through the structure, a better filtering effect can be achieved, and the circuit is more stable.

Preferably, the freewheeling circuit of the plasma cutting machine pilot arc electronic current-limiting resistor circuit comprises a power inductor L1 and a power diode D2, wherein an input end of the power diode D2 is connected with an OUT-end, and an output end of the power diode D2 is connected with a QDH end through the power inductor L1.

When current passes through the power inductor L1, induced electromotive force is generated at two ends of the power inductor L1, when the current disappears, the induced electromotive force generates reverse voltage to elements in the circuit, because the power diode D2 is connected in parallel with two ends of the power inductor L1, when the current passing through the power inductor L1 disappears, the induced electromotive force generated by the power inductor L1 is consumed by acting through a loop formed by the power diode D2 and the power inductor L1, so that the normal operation of follow current can be ensured, and the safety of other elements in the circuit can be protected.

Preferably, the plasma cutting machine pilot arc electronic current-limiting resistor circuit further comprises a second current sampling circuit, the second current sampling circuit comprises a resistor R12 and a resistor R13, after the resistor R12 and the resistor R13 form a parallel circuit, one end of the parallel circuit is connected with the power inductor L1, and the other end of the parallel circuit is connected with the output end of the power diode D2.

The current can be better sampled through the structure.

Preferably, the plasma cutting machine pilot arc electronic current limiting resistor circuit further comprises a first RC absorption circuit, the first RC absorption circuit comprises a resistor R17 and a capacitor C11, and the resistor R17 and the capacitor C11 are connected in series and then connected in parallel with the power diode D2.

The first RC absorption circuit can absorb the peak voltage at two ends of the power diode D2, so that the phenomenon that the voltage rising rate of the circuit is too large is avoided, and the safety of the circuit is ensured. The capacitor C11 and the series resistor R17 can play a damping role, and can prevent the power diode D2 from being damaged by overvoltage generated at two ends of the capacitor due to oscillation in the transition process of a circuit, and simultaneously can prevent the power diode D2 from being damaged by overcurrent due to overlarge discharge current of the capacitor through the power diode D2.

Preferably, the plasma cutting machine pilot arc electronic current-limiting resistor circuit further comprises a slope compensation circuit, the slope compensation circuit comprises a triode Q3, a resistor R5 and a resistor R10, a collector c of the triode Q3 is connected with a VREF end of the integrated chip U2, a base b of the triode Q3 is connected with an RT/CT end of the integrated chip U2, one path of an emitter e of the triode Q3 is connected with the first filter circuit through the resistor R5, and the other path of the emitter e is connected with a third path of the field-effect transistor Q1 through the resistor R10.

The slope compensation circuit effectively avoids disturbance current generated by the circuit in the circulating operation, avoids feedback oscillation and enables the circuit to be more stable.

Preferably, the plasma cutting machine pilot arc electronic current-limiting resistor circuit further comprises a second RC absorption circuit, the second RC absorption circuit comprises a resistor R14 and a capacitor C15, after the resistor R14 and the capacitor C15 form a series circuit, one end of the series circuit is connected with the second path of the fet Q1, and the other end of the series circuit is connected with the third path of the fet Q1.

The second RC absorption circuit can absorb the peak voltage generated by the field effect transistor Q1, so that the phenomenon that the voltage rising rate of the circuit is too large is avoided, and the safety of the circuit is ensured.

Preferably, the plasma cutting machine pilot arc electronic current-limiting resistor circuit further comprises a closed-loop current feedback loop, the closed-loop current feedback loop comprises an integrated chip U1, a capacitor C12, a capacitor C13, a resistor R2, a resistor R15, a resistor R16 and an adjustable resistor RT1, a non-inverting input end of the integrated chip U1 is connected with a third path of the field effect transistor Q1, an inverting input end of the integrated chip U1 is connected with the GNDB end through the resistor R16, an output end of the integrated chip U1 is connected with the VFB end of the integrated chip U2 through the resistor R15, one end of the capacitor C12 is connected with the adjustable resistor RT1 in parallel and is connected with the inverting input end of the integrated chip U1, the other end of the capacitor C12 is connected with the output end of the integrated chip U1, one end of the capacitor C13 is connected with the resistor R2 in parallel and is connected with the COMP end of the integrated chip U2, and the other end of the integrated chip U2 is connected with the VFB end.

The closed-loop current feedback loop can stably output the current between the QDH end and the OUT-end, and the current is not changed by the voltage input to the two ends of the OUT + end and the OUT-end or the change of the load between the output QDH end and the OUT-end, so that the pilot arc is more stable.

Preferably, the plasma cutting machine pilot arc electronic current-limiting resistor circuit further comprises a second filter circuit, the second filter circuit comprises a resistor R6, a resistor R7 and a capacitor C14, one end of the resistor R6 is connected with the third path of the field-effect transistor Q1, the other end of the resistor R6 is connected with the non-inverting input end of the integrated chip U1, one end of the resistor R7 is connected with the non-inverting input end of the integrated chip U1, the other end of the resistor R7 is connected with the freewheeling circuit, one end of the capacitor C14 is connected with the non-inverting input end of the integrated chip U1, and the other end of the capacitor C14 is connected with the GNDB end.

Better filtering effect can be achieved, and the circuit is more stable.

The invention has the following beneficial effects:

1. the invention can well replace the relay and the low-efficiency current-limiting resistor in the prior art, so that the replaced circuit is more stable and reliable, the loss in the circuit operation process is reduced, and the working efficiency of the pilot arc is improved.

2. The invention has simple and firm structure, low component cost and convenient maintenance and overhaul.

Drawings

Fig. 1 is a schematic circuit structure diagram of a pilot arc electronic current-limiting resistance circuit of a plasma cutting machine according to the present invention.

Detailed Description

The invention will be described in further detail below with reference to the accompanying figure 1 and the detailed description, but they are not intended to limit the invention:

example 1

As shown in fig. 1, a pilot arc electronic current-limiting resistor circuit of a plasma cutting machine includes a rectifying filter circuit 1 and a filter output circuit 9, both ends of the rectifying filter circuit 1 are respectively connected with an OUT + end and an OUT-end, both ends of the filter output circuit 9 are respectively connected with a QDH end and an OUT-end, the plasma cutting machine further includes an auxiliary power circuit 2, a frequency configuration circuit 14, a current-limiting circuit 3, a field-effect tube Q1, an integrated chip U2, a first current sampling circuit 6, a first filter circuit 4 and a freewheeling circuit 8, the field-effect tube Q1 includes three paths, the OUT end of the integrated chip U2 is connected with a first path of the field-effect tube Q1 through the current-limiting circuit 3, the rectifying filter circuit 1 is connected with a second path of the field-effect tube Q1, a SEN end of the integrated chip U2 is connected with a third path of the integrated chip U2 through the first path of the filter circuit 4, the other path is connected with a QDH end through a first current sampling circuit 6 and a follow current circuit 8, the frequency configuration circuit 14 is respectively connected with an RT/CT end, a GND end and a VREF end of an integrated chip U2, and the auxiliary power supply circuit 2 is connected with a VCC end of the integrated chip U2.

Preferably, the rectifying and filtering circuit 1 includes a power diode D3, a capacitor C1, a capacitor C9, a capacitor C10, and a capacitor C6, after the capacitor C1, the capacitor C9, the capacitor C10, and the capacitor C6 form a parallel circuit, one end of the parallel circuit is connected to the output end of the power diode D3, the other end of the parallel circuit is connected to the OUT-end, the input end of the power diode D3 is connected to the OUT + end, and the output end of the power diode D3 is further connected to the second path of the field effect transistor Q1.

Preferably, the filter output circuit 9 includes resistors R19, R20, R21 and a capacitor C7, the resistor R19, the resistor R20 and the resistor R21 form a series circuit and then are connected in parallel with the capacitor C7, one end of the capacitor C7 is connected with the QDH terminal, and the other end is connected with the OUT-terminal.

Preferably, the auxiliary power circuit 2 includes an auxiliary power supply terminal YH1, a diode D1, a capacitor C3 and a capacitor C4, an input terminal of the diode D1 is connected to an anode of the auxiliary power supply terminal YH1, an output terminal of the diode D1 is connected to a VCC terminal of the ic U2, the capacitor C3 and the capacitor C4 form a parallel circuit, and then one end of the parallel circuit is connected to the VCC terminal of the ic U2, and the other end of the parallel circuit is connected to the GNDB terminal.

Preferably, the frequency configuration circuit 14 includes a capacitor C2, a resistor R3, and a capacitor C8, one end of the capacitor C2 is connected to the GNDB terminal, the other end is connected to the VREF terminal of the integrated chip U2, one end of the resistor R3 is connected to the VREF terminal of the integrated chip U2, the other end is connected to the RT/CT terminal of the integrated chip U2, one end of the capacitor C8 is connected to the RT/CT terminal of the integrated chip U2, and the other end is connected to the GND terminal of the integrated chip U2.

Preferably, the current limiting circuit 3 includes a resistor R8, and the first path of the fet Q1 is connected to the OUT terminal of the ic U2 through a resistor R8.

Preferably, the first current sampling circuit 6 comprises a resistor R9 and a resistor R11, wherein the resistor R9 and the resistor R11 form a parallel circuit, and then one end of the parallel circuit is connected with the third path of the field effect transistor Q1, and the other end of the parallel circuit is connected with the free-wheeling circuit 8.

Preferably, the first filter circuit 4 includes a resistor R4 and a capacitor C5, one end of the resistor R4 is connected to the SEN end of the integrated chip U2, the other end of the resistor R4 is connected to the third path of the fet Q1, one end of the capacitor C5 is connected to the SEN end of the integrated chip U2, and the other end of the capacitor C5 is connected to the GNDB end.

Preferably, the freewheel circuit 8 includes a power inductor L1 and a power diode D2, an input terminal of the power diode D2 is connected to the OUT-terminal, and an output terminal of the power diode D2 is connected to the QDH terminal through the power inductor L1.

Preferably, the power supply further comprises a second current sampling circuit 7, the second current sampling circuit 7 comprises a resistor R12 and a resistor R13, the resistor R12 and the resistor R13 form a parallel circuit, and then one end of the parallel circuit is connected with the power inductor L1, and the other end of the parallel circuit is connected with the output end of the power diode D2.

Preferably, the power circuit further comprises a first RC absorption circuit 10, wherein the first RC absorption circuit 10 comprises a resistor R17 and a capacitor C11, and the resistor R17 and the capacitor C11 are connected in series and then connected in parallel with the power diode D2.

Preferably, the slope compensation circuit 13 further comprises a triode Q3, a resistor R5 and a resistor R10, wherein a collector c of the triode Q3 is connected with a VREF end of the integrated chip U2, a base b of the triode Q3 is connected with an RT/CT end of the integrated chip U2, one path of an emitter e of the triode Q3 is connected with the first filter circuit 4 through the resistor R5, and the other path of the emitter e is connected with a third path of the field effect transistor Q1 through the resistor R10.

Preferably, the second RC absorption circuit 5 is further included, the second RC absorption circuit 5 includes a resistor R14 and a capacitor C15, after the resistor R14 and the capacitor C15 form a series circuit, one end of the series circuit is connected to the second path of the fet Q1, and the other end of the series circuit is connected to the third path of the fet Q1.

Preferably, the feedback circuit further comprises a closed-loop current feedback circuit 12, wherein the closed-loop current feedback circuit 12 comprises an integrated chip U1, a capacitor C12, a capacitor C13, a resistor R2, a resistor R15, a resistor R16 and an adjustable resistor RT1, a non-inverting input terminal of the integrated chip U1 is connected with the third path of the field effect transistor Q1, an inverting input terminal of the integrated chip U1 is connected with the GNDB terminal through a resistor R16, an output terminal of the integrated chip U1 is connected with the VFB terminal of the integrated chip U2 through a resistor R15, one end of the capacitor C12 is connected with the adjustable resistor RT1 in parallel, the other end of the capacitor C12 is connected with the inverting input terminal of the integrated chip U1, the other end of the capacitor C1 is connected with the output terminal of the integrated chip U13, one end of the capacitor C13 is connected with the COMP terminal of the integrated chip U2 in parallel with the resistor R2, and the other end of the integrated chip U2 is connected with the VFB terminal of the integrated chip U2.

Preferably, the filter further comprises a second filter circuit 11, the second filter circuit 11 comprises a resistor R6, a resistor R7 and a capacitor C14, one end of the resistor R6 is connected with the third path of the fet Q1, the other end of the resistor R6 is connected with the non-inverting input terminal of the ic U1, one end of the resistor R7 is connected with the non-inverting input terminal of the ic U1, the other end of the resistor R7 is connected with the freewheeling circuit 8, one end of the capacitor C14 is connected with the non-inverting input terminal of the ic U1, and the other end of the capacitor C14 is connected with the GNDB terminal.

Example 2

As shown in fig. 1, when the plasma cutting machine is powered on, the input voltage is rectified by the power diode D3, and is filtered by the capacitor C1, the capacitor C6, the capacitor C9 and the capacitor C10 to be used as a dc bus power supply of the pilot arc electronic current-limiting resistor circuit. The current provided by the auxiliary power supply terminal YH1 is rectified by the diode D1, filtered by the capacitor C3 and the capacitor C4, and then input to the VCC terminal of the integrated chip U2 as an auxiliary power supply, so that the integrated chip U2 is powered on and starts to operate.

The OUT terminal of the integrated chip U2 outputs the PWM on signal to turn on the fet Q1, so that the dc bus power is output to the QDH terminal via the fet Q1, the resistor R9, the resistor R11, and the power inductor L1, and the current in the fet Q1 and the voltage and current flowing through the resistor R9 and the resistor R11 rise linearly due to the action of the power inductor L1.

One path of voltage on the resistor R9 and the resistor R11 is sent to a non-inverting input end of the integrated chip U1 through the resistor R6 and the capacitor C14, the integrated chip U1 amplifies a voltage signal by a certain multiple and then sends the amplified voltage signal to a VFB end of the integrated chip U2, the VFB end of the integrated chip U2 functions as an error amplifier, and the integrated chip U2 refers to a voltage value of the VFB end and adjusts the pulse width of PWM to achieve the purpose of limiting output current.

After the other path of the voltage on the resistor R9 and the resistor R11 is sent to the SEN end of the integrated chip U2 and exceeds a threshold value, the OUT end of the integrated chip U2 closes a PWM (pulse width modulation) on-signal, so that the field effect transistor Q1 is protected from being damaged due to overcurrent, and the field effect transistor Q1 is closed and cut off. When the field effect transistor Q1 is turned off, a peak voltage may be generated between the second path and the third path of the field effect transistor Q1 due to stray inductance of the dc bus circuit, so that the field effect transistor Q1 may be damaged, and the second RC absorption circuit composed of the resistor R14 and the capacitor C15 can reduce the amplitude of the peak, thereby ensuring the stability of the circuit.

After the field effect transistor Q1 is turned off, magnetic energy is still stored in the power inductor L1, and the magnetic energy starts to be output to the QDH end through the power diode D2, at this time, the current and the voltage flowing through the resistor R12 and the resistor R13 are sent to the non-inverting input end of the integrated chip U1 through the resistor R7 and the capacitor C14, the integrated chip U1 amplifies the voltage signal by a certain multiple and then sends the amplified voltage signal to the VFB end of the integrated chip U2, the integrated chip U2 refers to the voltage value of the VFB end and adjusts the pulse width of PWM to limit the output current until the working period of the integrated chip U2 is ended and the second working period is started, and the process is repeated.

When the first working cycle of the integrated chip U2 is finished and the second working cycle is started, the fet Q1 is driven to turn on again, and at this time, the dc bus voltage will pass through the fet Q1, the resistor R9, the resistor R11, the resistor R12, and the resistor R13 to turn the power diode D2 into a reverse turn-off state, and because the dc bus loop has stray inductance and will generate peak voltage at both ends of the power diode D2, the first RC absorption circuit composed of the resistor R17 and the capacitor C11 will slow down the amplitude of the peak, thereby ensuring the stability of the circuit.

The process is circulated, so that the loss in the arc maintenance process is reduced, and the arc maintenance work efficiency is improved.

In summary, the above-mentioned embodiments are only preferred embodiments of the present invention, and all equivalent changes and modifications made within the scope of the claims of the present invention should be covered by the present invention.

Claims

1. The utility model provides a plasma cutting machine pilot arc electron current-limiting resistance circuit, includes rectifier filter circuit (1), filtering output circuit (9), rectifier filter circuit's (1) both ends respectively with OUT + end, OUT-end connection, filtering output circuit's (9) both ends respectively with QDH end, OUT-end connection, its characterized in that: also comprises an auxiliary power supply circuit (2), a frequency configuration circuit (14), a current limiting circuit (3), a field effect transistor Q1, an integrated chip U2, a first current sampling circuit (6), a first filter circuit (4) and a follow current circuit (8), the field effect transistor Q1 comprises three paths, the OUT end of the integrated chip U2 is connected with the first path of the field effect transistor Q1 through a current limiting circuit (3), the rectification filter circuit (1) is connected with a second path of a field effect transistor Q1, the SEN end of the integrated chip U2 is connected with a third path of the integrated chip U2 through one path of the first filter circuit (4), the other path of the integrated chip U2 is connected with a QDH end through a first current sampling circuit (6) and a follow current circuit (8), the frequency configuration circuit (14) is respectively connected with an RT/CT end, a GND end and a VREF end of the integrated chip U2, and the auxiliary power supply circuit (2) is connected with a VCC end of the integrated chip U2.

2. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the rectifying and filtering circuit (1) comprises a power diode D3, a capacitor C1, a capacitor C9, a capacitor C10 and a capacitor C6, wherein after the capacitor C1, the capacitor C9, the capacitor C10 and the capacitor C6 form a parallel circuit, one end of the parallel circuit is connected with the output end of the power diode D3, the other end of the parallel circuit is connected with an OUT-end, the input end of the power diode D3 is connected with an OUT + end, and the output end of the power diode D3 is further connected with the second path of the field-effect tube Q1.

3. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the filter output circuit (9) comprises resistors R19, R20, R21 and a capacitor C7, wherein the resistor R19, the resistor R20 and the resistor R21 form a series circuit and then are connected with the capacitor C7 in parallel, one end of the capacitor C7 is connected with the QDH end, and the other end of the capacitor C7 is connected with the OUT-end.

4. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: auxiliary power supply circuit (2) including auxiliary power supply end YH1, diode D1, electric capacity C3, electric capacity C4, diode D1's input and auxiliary power supply end YH1 anodal be connected, diode D1's output and integrated chip U2's VCC end are connected, electric capacity C3, electric capacity C4 constitute behind the parallel circuit one end and integrated chip U2's VCC end be connected, the other end is connected with the GNDB end.

5. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: frequency configuration circuit (14) include electric capacity C2, resistance R3, electric capacity C8, electric capacity C2 one end be connected with GNDB end, the other end is connected with integrated chip U2's VREF end, resistance R3 one end be connected with integrated chip U2's VREF end, the other end is connected with integrated chip U2's RT/CT end, electric capacity C8 one end be connected with integrated chip U2's RT/CT end, the other end is connected with integrated chip U2's GND end.

6. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the current limiting circuit (3) comprises a resistor R8, and the first path of the field effect transistor Q1 is connected with the OUT end of the integrated chip U2 through a resistor R8.

7. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the first current sampling circuit (6) comprises a resistor R9 and a resistor R11, wherein one end of the resistor R9 and the resistor R11 form a parallel circuit, the third path of the field effect transistor Q1 is connected, and the other end of the resistor R9 and the third path of the field effect transistor Q1 are connected with the follow current circuit (8).

8. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the first filter circuit (4) comprises a resistor R4 and a capacitor C5, one end of the resistor R4 is connected with the SEN end of an integrated chip U2, the other end of the resistor R4 is connected with the third path of the field effect transistor Q1, one end of the capacitor C5 is connected with the SEN end of the integrated chip U2, and the other end of the capacitor C5 is connected with the GNDB end.

9. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the follow current circuit (8) comprises a power inductor L1 and a power diode D2, wherein the input end of the power diode D2 is connected with the OUT-end, and the output end of the power diode D2 is connected with the QDH end through the power inductor L1.

10. The plasma cutting machine pilot arc electronic current limiting resistor circuit according to claim 9, characterized in that: still include second current sampling circuit (7), second current sampling circuit (7) include resistance R12, resistance R13, resistance R12 and resistance R13 constitute the parallel circuit after one end be connected with power inductance L1, the other end is connected with power diode D2's output.

11. The plasma cutting machine pilot arc electronic current limiting resistor circuit according to claim 9, characterized in that: the power diode also comprises a first RC absorption circuit (10), wherein the first RC absorption circuit (10) comprises a resistor R17 and a capacitor C11, and the resistor R17 and the capacitor C11 are connected in series and then connected in parallel with the power diode D2.

12. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: still include slope compensation circuit (13), slope compensation circuit (13) include triode Q3, resistance R5, resistance R10, triode Q3's collecting electrode c with integrated chip U2's VREF end connect, triode Q3's base b with integrated chip U2's RT/CT end is connected, triode Q3's emitting electrode e is connected with first filter circuit (4) through resistance R5 all the way, and another way is connected through resistance R10 and field effect transistor Q1's third route.

13. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the circuit further comprises a second RC absorption circuit (5), wherein the second RC absorption circuit (5) comprises a resistor R14 and a capacitor C15, one end of the resistor R14 and the capacitor C15 form a series circuit, and then are connected with the second path of the field-effect tube Q1, and the other end of the resistor R14 and the third path of the field-effect tube Q1.

14. The plasma cutting machine pilot arc electronic current-limiting resistance circuit according to claim 1, characterized in that: the feedback circuit further comprises a closed-loop current feedback loop (12), the closed-loop current feedback loop (12) comprises an integrated chip U1, a capacitor C12, a capacitor C13, a resistor R2, a resistor R15, a resistor R16 and an adjustable resistor RT1, the non-inverting input end of the integrated chip U1 is connected with the third path of the field effect transistor Q1, the inverting input end of the integrated chip U1 is connected with the GNDB end through the resistor R16, the output end of the integrated chip U1 is connected with the VFB end of the integrated chip U2 through the resistor R15, one end of the capacitor C12 is connected with the inverting input end of the integrated chip U1 after being connected in parallel with the adjustable resistor RT1, the other end of the capacitor C13 is connected with the output end of the integrated chip U1, one end of the capacitor C13 is connected with the COMP end of the integrated chip U2 after being connected with the resistor R2 in parallel with the VFB end of the integrated chip U2.

15. The plasma cutting machine pilot arc electronic current limiting resistor circuit according to claim 14, characterized in that: still include second filter circuit (11), second filter circuit (11) include resistance R6, resistance R7, electric capacity C14, resistance R6's one end and field effect transistor Q1's third three way connection, the other end is connected with integrated chip U1's homophase input, resistance R7's one end be connected with integrated chip U1's homophase input, the other end is connected with freewheel circuit (8), electric capacity C14's one end with integrated chip U1's homophase input is connected, the other end is connected with the GNDB end.