Current acceleration type high-low voltage composite pulse power supply for electrical discharge machining

Abstract

The invention discloses a current acceleration type high-low voltage composite pulse power supply for electric spark machining, which belongs to the field of pulse power supplies for electric spark machining, and comprises a direct current source, an FPGA control circuit, a driving loop, an SEPIC main power circuit and a Buck main power circuit, the DC source is used for outputting an AC voltage as an adjustable DC voltage to supply power to the SEPIC main power circuit and the Buck main power circuit, the FPGA control circuit is used for outputting a PWM control signal, and the driving loop is used for amplifying the PWM control signal and then generating a driving signal to control the on-off of a switching tube in the SEPIC main power circuit and the on-off of a switching tube in the Buck main power circuit. The SEPIC main power circuit is used for being connected with a machine tool gap to achieve gap breakdown and current pumping, and the Buck main power circuit is used for being connected with the machine tool gap to achieve electric discharge machining. The SEPIC main power topology still participates in machining after gap breakdown, rapid pumping of machining current is achieved, the dynamic characteristic of a pulse power supply is greatly improved, and the electric spark machining quality is improved.

Description

Technical Field

[0001] The invention relates to the field of pulse power supplies for electric spark machining, in particular to a current acceleration type high-low voltage composite pulse power supply for electric spark machining. Background Art

[0002] In the field of EDM, pulse power supply is one of the core components, and its performance directly affects the processing efficiency and quality. EDM technology connects the positive and negative poles of the pulse power supply to the electrode and the workpiece respectively. The pulse power supply applies a certain voltage to break through the insulating working fluid, forming a discharge channel between the two poles. Relying on the local and instantaneous high temperature generated by the discharge to erode the workpiece material, it can process complex surfaces, narrow gaps and fine structures of special metals and semiconductor materials, and can ensure good processing surface quality and processing accuracy. It is widely used in the field of high-end manufacturing. In the EDM stage, the existing high-low voltage composite pulse power supply cannot achieve a rapid increase in the processing current due to the filter inductance limiting the rapid change of the current. The rapid increase in processing current is crucial to improving the material removal efficiency, especially in high-demand occasions such as fine processing or processing of refractory metals. The hysteresis of the current will directly affect the processing speed, accuracy and surface quality. In the processing process, the ideal current characteristic should be that the required current value is quickly reached after the discharge channel is established to ensure effective material removal and reduce the processing heat affected zone. However, the current response characteristics of existing power supplies are insufficient, which prolongs the processing time, especially when processing complex geometries or ultra-hard materials, and the processing efficiency is significantly reduced. Summary of the invention

[0003] The technical problem to be solved by the present invention is to address the defects of the background technology, and to achieve rapid rise of machining current and improve the quality of electrospark machining through a current-accelerating high-low voltage composite pulse power supply for electrospark machining.

[0004] The present invention adopts the following technical solutions to solve the above technical problems:

[0005] A current-accelerating high-low voltage composite pulse power supply for electric spark machining comprises a DC source, an FPGA control circuit, a drive circuit, a SEPIC main power circuit, and a Buck main power circuit. The DC source is used to output an AC voltage as an adjustable DC voltage to power the SEPIC main power circuit and the Buck main power circuit. The FPGA control circuit is used to output a PWM control signal. The drive circuit is used to amplify the PWM control signal to generate a drive signal to control the on and off of a switch tube in the SEPIC main power circuit and the on and off of a switch tube in the Buck main power circuit. The SEPIC main power circuit is used to connect a machine tool gap to realize a breakdown gap and current pumping. The Buck main power circuit is used to connect a machine tool gap to realize electric discharge machining.

[0006] Preferably, the main component of the SEPIC main power circuit is the input filter capacitor C 1 , switch tube (Q 1 , Q 2 , Q 3 , Q 4 ), freewheeling diode D, intermediate capacitor C 2 、Filter inductance (L 1 , L 2 ), output filter capacitor C 3 , output resistance R, the input filter capacitor C 1 The anode and DC source V in The positive connection of the input filter capacitor C 1 The cathode and DC source V in The negative pole of the filter inductor L 1 One end of the input filter capacitor C 1 The anode and DC source V in The positive connection point is connected to the filter inductor L 1 The other end of the middle capacitor C 2 The anode of the switch tube Q 1 The drain and filter inductor L 1 and the intermediate capacitor C 2 The connection point of the anode is connected, and the switch tube Q 1 The source of the DC source V in The negative electrode is connected to the middle capacitor C 2 The cathode is connected to the anode of the freewheeling diode D, and the filter inductor L 2 One end and the middle capacitor C 2 The cathode of the freewheeling diode D is connected to the connection point of the anode, and the filter inductor L 2 The other end is connected to the DC source V in The negative pole of the switch tube Q 2 The drain and switch tube Q 4 The drain of the freewheeling diode D is connected to the cathode of the switch tube Q 2 Drain and switch Q 4 The connection point of the drain is connected, and the switch tube Q 2 The source and output filter capacitor C 3 The anode of the switch tube Q 3 The drain and output filter capacitor C 3 The cathode of the switch tube Q 4 The source is connected to the workpiece, and the tool is connected to the switch tube Q 3 The source of the output resistor R is connected to the switch tube Q 2 Source and output filter capacitor C 3 The connection point of the anode is connected, and the other end of the output resistor R is connected to the switch tube Q3 Drain and output filter capacitor C 3 The cathode connection points are connected.

[0007] Preferably, the main component of the Buck main power circuit is the input filter capacitor C 4 , switch tube (Q 5 , Q 6 ), filter inductor L 3 , the input filter capacitor C 4 The anode and DC source V in The positive connection of the input filter capacitor C 4 The cathode and current source V in The cathode connection of the switch tube Q 5 The drain and input filter capacitor C 4 The anode and DC source V in The positive connection point is connected to the switch tube Q 6 The drain and filter inductor L 3 One end is connected, the switch tube Q 5 The source and switch tube Q 6 Drain and filter inductor L 3 The connection point at one end is connected to the filter inductor L 3 The other end is connected to the workpiece, and the switch tube Q 6 The source of is connected to the tool.

[0008] Preferably, the switch tube is a metal-oxide semiconductor field effect transistor made of silicon carbide material, or a metal-oxide semiconductor field effect transistor made of silicon and gallium nitride materials.

[0009] Preferably, a single cycle of electrical discharge machining comprises the following steps:

[0010] Step S1: In the arc-starting stage, the gap is not broken down, the SEPIC main power circuit in the current-accelerating high-low voltage composite pulse power supply works in the boost mode, and the Buck main power circuit does not participate in the work. The SEPIC main power circuit works in the boost mode and has two working states. In the first working state, the FPGA control circuit generates a control signal, and after passing through the drive circuit, the switch tube Q is controlled. 1 , Q 2 , Q 3 The filter inductor L 1 , L 2 Energy storage, filter capacitor C 3 The voltage drops. In the second working state, the FPGA control circuit generates a control signal, which passes through the drive circuit and controls the switch tube Q. 1 Shutdown, filter inductor L 1 , L 2 To the filter capacitor C3 Charging, filter capacitor C 3 The voltage rises, repeating the above two working modes, the filter capacitor C 3 The voltage is maintained at a relatively high forward voltage in order to wait for the gap to break down;

[0011] Step S2: When the gap is turned on and enters the gap discharge period, the FPGA control circuit generates a control signal, which controls the switch tube Q after passing through the drive circuit. 5 Turn on, switch tube Q 1 , Q 2 , Q 3 Turn off, at this time the filter inductor L 3 The current rises, the current of the freewheeling diode D decreases, and the filter capacitor C 3 Discharge to the output resistor R, the gap current rises rapidly and remains at the preset value;

[0012] Step S3: After that, the FPGA control circuit generates a control signal, which passes through the drive circuit to control the switch tube Q 5 Turn off, switch tube Q 6 The gap current passes through the switch tube Q 6 Continue current;

[0013] Step S4: Then, the FPGA control circuit generates a control signal, which passes through the drive circuit to control the switch tube Q 5 Turn on, switch tube Q 6 Turn off, the gap current rises;

[0014] Step S5: Repeat steps S3 to S4 until the discharge duration reaches the preset value in the FPGA. The FPGA control circuit generates a control signal, which passes through the drive circuit to control the switch tube Q. 5 And the switch tube Q 6 At the same time, the deionization stage is carried out to make the voltage across the gap zero;

[0015] Step S6: Repeat steps S1 to S5 to enter the next processing cycle.

[0016] Compared with the prior art, the present invention adopts the above technical solution and has the following beneficial effects:

[0017] 1. The current-accelerating high-low voltage composite pulse power supply for EDM proposed by the present invention enables the machining current to rise rapidly when the gap is broken down, greatly improving the dynamic characteristics of the pulse power supply, thereby improving the quality of EDM.

[0018] 2. The current-accelerated high- and low-voltage composite pulse power supply for EDM uses FPGA programming to control the timing of high and low voltage power supplies, and can provide a variety of electrical parameters to meet the needs of different processing scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0020] Figure 1 It is the electric spark current accelerated high and low voltage composite pulse power supply framework proposed by the present invention;

[0021] Figure 2 The spark current accelerated high and low voltage composite pulse power supply topology proposed by the present invention;

[0022] Figure 3 This is the application principle diagram of the driver chip used in the present invention;

[0023] Figure 4 It is a schematic diagram of the waveform of the electric spark current accelerated high and low voltage composite pulse power supply electric discharge machining proposed by the present invention. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] The present invention is a current acceleration type high and low voltage composite pulse power supply for electric spark machining, such as Figure 1 As shown, it includes a DC source, an FPGA control circuit, a drive circuit, a SEPIC main power circuit, and a Buck main power circuit. The DC source is used to output an AC voltage as an adjustable DC voltage to power the SEPIC main power circuit and the Buck main power circuit. The FPGA control circuit is used to output a PWM control signal. The drive circuit is used to amplify the PWM control signal to generate a drive signal to control the on and off of the switch tube in the SEPIC main power circuit and the on and off of the switch tube in the Buck main power circuit. The SEPIC main power circuit is used to connect the machine tool gap to achieve a breakdown gap and current pumping. The Buck main power circuit is used to connect the machine tool gap to achieve discharge machining.

[0026] Preferably, as a specific example, the FPGA control circuit is mainly controlled by FPGA (field programmable gate array). Since the corresponding control circuit structure is integrated internally, the driving signal of the corresponding switch tube can be automatically obtained through program operation. At the same time, program control can be used to meet the needs of different processing stages. The present invention selects ALTERA's Cyclone IV series chip EP4CE6F17C8.

[0027] Preferably, as a specific example, the driving circuit can select a driving chip with high-end and low-end dual-channel driving and isolation characteristics. The present invention selects a driving chip model UCC21521 of Texas Instruments. Figure 3 As shown, the chip has smaller propagation delay and pulse width distortion. The driver of the chip can be configured as two low-side drivers, two high-side drivers or one single-zone driver, and is an isolated dual-channel gate driver chip. It can be suitable for switching tubes with a frequency of up to 5MHz, and can meet the requirements of the pulse power supply of the present invention for high efficiency, high power density and robustness.

[0028] Preferably, Figure 4 As shown, a single cycle of the electrical discharge machining comprises the following steps:

[0029] Step S1: In the arc ignition stage, the gap is not broken down, and the FPGA generates corresponding multi-channel PWM signals, which are amplified by the drive circuit to control the switch tube Q 1 And the switch tube Q 2 At the same time, the DC source V in , switch tube Q 1 , switch tube Q 2 The power loop formed with the load provides a relatively high forward voltage to the load gap in order to provide a voltage that can break down when the gap is relatively small.

[0030] Step S2: When the gap is turned on and enters the gap discharge period, the FPGA generates corresponding multi-channel PWM signals, which are amplified by the drive circuit to control the switch tube Q 1 Turn on, switch tube Q 2 Turn off, at this time, the voltage divider capacitor C 1 , switch tube Q 1 The power loop formed with the load realizes a single-channel BUCK circuit and provides a forward voltage to the load gap.

[0031] Step S3: Generate corresponding multi-channel PWM signals again to control the switch tube Q 2 Turn on, switch tube Q 1 Turn off, at this time, the voltage divider capacitor C2 , switch tube Q 2 The power loop formed with the load realizes a single-channel BUCK circuit and provides a forward voltage to the load gap.

[0032] Step S4: Repeat the above steps S2 and S3 until the discharge duration reaches the preset value in the FPGA, and then control the switch tube Q 1 And the switch tube Q 2 At the same time, it is turned off and the deionization stage is carried out so that the voltage across the gap is zero.

[0033] Step S5: Repeat steps S1 to S4 to enter the next processing cycle.

[0034] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A current acceleration type high and low voltage composite pulse power supply for electrospark machining, characterized in that: The invention comprises a direct current source, an FPGA control circuit, a drive circuit, a SEPIC main power circuit and a Buck main power circuit. The direct current source is used to output an alternating current voltage as an adjustable direct current voltage to supply power to the SEPIC main power circuit and the Buck main power circuit. The FPGA control circuit is used to output a PWM control signal. The drive circuit is used to amplify the PWM control signal to generate a drive signal to control the on and off of a switch tube in the SEPIC main power circuit and the on and off of a switch tube in the Buck main power circuit. The SEPIC main power circuit is used to connect a machine tool gap to realize a breakdown gap and current pumping. The Buck main power circuit is used to connect a machine tool gap to realize electric discharge machining.

2. The current-accelerating high-low voltage composite pulse power supply for electrospark machining according to claim 1, characterized in that: The main components of the SEPIC main power circuit are input filter capacitor C1, switch tubes Q1, Q2, Q3, Q4, freewheeling diode D, intermediate capacitor C2, filter inductors L1, L2, output filter capacitor C3, and output resistor R; the anode of the input filter capacitor C1 and the DC source V in The positive electrode of the input filter capacitor C1 is connected to the cathode and the DC source V in The negative electrode of the filter inductor L1 is connected to the anode of the input filter capacitor C1 and the DC source V in The other end of the filter inductor L1 is connected to the anode of the intermediate capacitor C2, the drain of the switch tube Q1 is connected to the connection point of the filter inductor L1 and the anode of the intermediate capacitor C2, and the source of the switch tube Q1 is connected to the DC source V in The cathode of the intermediate capacitor C2 is connected to the anode of the freewheeling diode D, one end of the filter inductor L2 is connected to the connection point of the cathode of the intermediate capacitor C2 and the anode of the freewheeling diode D, and the other end of the filter inductor L2 is connected to the DC source V in The negative electrode of the switch tube Q2 is connected to the drain of the switch tube Q4, the cathode of the freewheeling diode D is connected to the connection point of the drain of the switch tube Q2 and the drain of the switch tube Q4, the source of the switch tube Q2 is connected to the anode of the output filter capacitor C3, the drain of the switch tube Q3 is connected to the cathode of the output filter capacitor C3, the source of the switch tube Q4 is connected to the workpiece, the tool is connected to the source of the switch tube Q3, one end of the output resistor R is connected to the connection point of the source of the switch tube Q2 and the anode of the output filter capacitor C3, and the other end of the output resistor R is connected to the connection point of the drain of the switch tube Q3 and the cathode of the output filter capacitor C3.

3. The current-accelerating high-low voltage composite pulse power supply for electrospark machining according to claim 1, characterized in that: The main components of the Buck main power circuit are input filter capacitor C4, switch tubes Q5, Q6, and filter inductor L3; the anode of the input filter capacitor C4 and the DC source V in The positive connection of the input filter capacitor C4 and the cathode and current source V in The cathode of the switch tube Q5 is connected to the anode of the input filter capacitor C4 and the DC source V in The drain of the switch tube Q6 is connected to one end of the filter inductor L3, the source of the switch tube Q5 is connected to the connection point of the drain of the switch tube Q6 and one end of the filter inductor L3, the other end of the filter inductor L3 is connected to the workpiece, and the source of the switch tube Q6 is connected to the tool.

4. The current-accelerating high-low voltage composite pulse power supply for electrospark machining according to claim 1, characterized in that: A single cycle of EDM includes the following steps: Step S1: In the arc-starting stage of the gap, the gap is not broken down, the SEPIC main power circuit in the current-accelerating high-low voltage composite pulse power supply works in the boost mode, and the Buck main power circuit does not participate in the work. The SEPIC main power circuit works in the boost mode and has two working states: in the first working state, the FPGA control circuit generates a control signal, and after passing through the drive circuit, the switch tubes Q1, Q2, and Q3 are controlled to be turned on. At this time, the filter inductors L1 and L2 store energy, and the voltage of the filter capacitor C3 decreases; in the second working state, the FPGA control circuit generates a control signal, and after passing through the drive circuit, the switch tube Q1 is controlled to be turned off, and the filter inductors L1 and L2 charge the filter capacitor C3, and the voltage of the filter capacitor C3 increases; repeat the above two working modes, and the voltage of the filter capacitor C3 is maintained at a relatively high forward voltage to facilitate waiting for the gap to be broken down; Step S2: When the gap is turned on, it enters the gap discharge period, and the FPGA control circuit generates a control signal. After passing through the drive circuit, the switch tube Q5 is controlled to be turned on, and the switch tubes Q1, Q2, and Q3 are turned off. At this time, the current of the filter inductor L3 increases, the current of the freewheeling diode D decreases, and the filter capacitor C3 discharges to the output resistor R. The gap current rises rapidly and is maintained at the actual preset value; Step S3: The FPGA control circuit generates a control signal, which, after passing through the drive circuit, controls the switch tube Q5 to be turned off and the switch tube Q6 to be turned on, so that the gap current continues to flow through the switch tube Q6; Step S4: The FPGA control circuit generates a control signal, which, after passing through the drive circuit, controls the switch tube Q5 to be turned on, the switch tube Q6 to be turned off, and the gap current increases; Step S5: Repeat steps S3 to S4 until the discharge duration reaches a preset value in the FPGA, and the FPGA control circuit generates a control signal, which, after passing through the drive circuit, controls the switch tubes Q5 and Q6 to be turned off at the same time, and performs the deionization stage so that the voltage across the gap is zero; Step S6: Repeat steps S1 to S5 to enter the next processing cycle.

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