CN111431431A - Anti-electrolysis high-low voltage composite micro pulse power supply - Google Patents
Anti-electrolysis high-low voltage composite micro pulse power supply Download PDFInfo
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M11/00—Power conversion systems not covered by the preceding groups
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
- H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/53—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback
- H03K3/57—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback the switching device being a semiconductor device
Abstract
The invention discloses an electrolysis-preventing high-low voltage composite micro pulse power supply and a control method thereof, wherein the power supply comprises a direct current power supply, a pulse power supply main circuit, an FPGA control circuit, a driving circuit and a current-voltage detection circuit, wherein the pulse power supply main circuit consists of a primary circuit, a flyback high-voltage breakdown circuit, a micro pulse power supply main discharge circuit and a negative-voltage electrolysis-preventing circuit; the gap voltage and the gap current are sampled respectively during processing and are used as feedback quantities to be input to the FPGA control module, corresponding PWM signals are generated by calculation according to processing requirements, the PWM signals are filtered and amplified by the driving circuit and then respectively drive the switching tubes in the pulse power supply main circuit to be switched on and off, high-voltage breakdown is firstly realized, then the main discharging circuit carries out discharge processing on the gap, and finally the electrolytic-proof working state is realized, so that the function of the electrolytic-proof high-low voltage composite micro pulse power supply is realized. The invention reduces the volume of the power supply and improves the utilization rate of the power supply, the processing precision and the surface quality.
Description
Technical Field
The invention relates to a micro-machining pulse power supply, in particular to an electrolysis-preventing high-low voltage composite micro-pulse power supply.
Background
Micro electric discharge machining inherits the characteristics of small macroscopic acting force, non-contact machining and the like of common electric discharge machining, simultaneously has the advantages of low stress, no burr, capability of machining high-hardness materials and the like, is suitable for machining difficult-to-cut materials and complex shapes or special parts, becomes an important precise machining method in the micro manufacturing field, and plays an increasingly important role in the industries of aerospace, automobiles, biomedical instruments and the like.
With the increasing requirements of the machining size and precision of the micro machine, higher requirements are put forward on micro machining. The micro pulse power supply is a key device of a micro electric discharge machining system, and the performance of the micro pulse power supply determines the machining efficiency, precision, cutting stability, surface roughness and the like. The traditional micro pulse power supply is mostly an RC type pulse power supply, generally, a charging resistor is used for charging a capacitor, meanwhile, the capacitor is connected into a gap through a current-limiting resistor, the capacitor discharges in the gap, and very small processing energy is obtained by adjusting the capacitance value and the open-circuit voltage of the capacitor. Therefore, the design and research of new micro-pulse power sources are urgent.
Disclosure of Invention
The invention aims to provide an electrolysis-preventing high-low voltage composite micro pulse power supply.
The technical solution for realizing the purpose of the invention is as follows: an electrolysis-preventing high-low voltage composite micro pulse power supply comprises a direct current power supply, a pulse power supply main circuit, an FPGA control circuit, a driving circuit and a current and voltage detection circuit, wherein the pulse power supply main circuit consists of a primary side circuit, a flyback high-voltage breakdown circuit, a micro pulse power supply main discharge circuit and a negative voltage electrolysis-preventing circuit; the output of the pulse power supply main discharge circuit, the high-voltage breakdown circuit and the anti-electrolytic circuit is connected to the gap load to process the workpiece; the current and voltage detection circuit respectively samples the voltage at two ends of the gap and the gap current in real time during processing, and the sampled voltages and the gap current are used as feedback signals to be input to the FPGA control module; the FPGA module generates a plurality of paths of PWM signals, and the signals are filtered and amplified by the driving circuit and then drive the on-off of a main circuit switching tube of the pulse power supply.
The pulse power supply main circuit comprises a primary side switch tube, a high-voltage breakdown switch tube, a negative-voltage anti-electrolysis switch tube, a micro-discharge switch tube, a primary side first inductor, a first resistor, a first capacitor, a first diode, a secondary side second inductor, a second capacitor, a second resistor, a second diode, a third resistor, a third diode, a third inductor, a third capacitor, a fourth diode, a fourth resistor, a fifth diode, a fourth inductor, a fourth capacitor, a fifth resistor, a sixth diode and a seventh diode, wherein the primary side first inductor, the secondary side second inductor, the third inductor and the fourth inductor form a flyback transformer; one end of the primary side first inductor is connected with the positive electrode of a power supply, and the other end of the primary side first inductor is connected with the negative electrode of the power supply; the high-voltage breakdown switch tube, the secondary side second inductor, the second capacitor, the second resistor, the second diode, the third resistor and the third diode form a high-voltage breakdown circuit, at the moment, one end of the secondary side second inductor is connected with the anode of the second diode, the other end of the secondary side second inductor is connected with the cathode of the second capacitor, the cathode of the second diode is connected with the anode of the second capacitor, and the second resistor is connected with the second capacitor in parallel; the drain electrode of the high-voltage breakdown switch tube is connected with the cathode of the second diode, the source electrode of the high-voltage breakdown switch tube is connected with the anode of the third diode, and the cathode of the third diode is connected with a processing workpiece; one end of the third resistor is connected with the negative electrode of the second capacitor, and the other end of the third resistor is connected with the tool electrode; the negative voltage anti-electrolysis circuit is composed of a negative voltage anti-electrolysis switching tube, a secondary side third inductor, a third capacitor, a fourth diode, a fourth resistor and a fifth diode, wherein one end of the secondary side third inductor is connected with the anode of the fourth diode, the other end of the secondary side third inductor is connected with the cathode of the third capacitor, the cathode of the fourth diode is connected with the anode of the third capacitor, and the fourth resistor is connected with the third capacitor in parallel; the drain electrode of the negative-pressure anti-electrolysis switching tube is connected with the cathode of the fourth diode, the source electrode of the negative-pressure anti-electrolysis switching tube is connected with the anode of the fifth diode, and the cathode of the fifth diode is connected with the tool electrode; the processing workpiece is connected with the negative electrode of the third capacitor; the micro discharge switch tube, a secondary side fourth inductor, a fourth capacitor, a fifth resistor, a sixth diode and a seventh diode form a pulse power supply main discharge circuit, at the moment, one end of the secondary side fourth inductor is connected with the anode of the sixth diode, the other end of the secondary side fourth inductor is connected with the cathode of the fourth capacitor, the cathode of the sixth diode is connected with the anode of the fourth capacitor, and the fifth resistor is connected with the fourth capacitor in parallel; the drain electrode of the micro discharge switching tube is connected with the anode of the fourth capacitor, the source electrode of the micro discharge switching tube is connected with the anode of the seventh diode, and the cathode of the seventh diode is connected with a processing workpiece; the tool electrode is connected with the negative electrode of the fourth capacitor.
The primary side switch tube, the high-voltage breakdown switch tube, the negative-voltage anti-electrolysis switch tube and the micro-discharge switch tube are made of metal-oxide semiconductor field effect transistors, and the materials of the metal-oxide semiconductor field effect transistors are Si, SiC or GaN.
The magnetic core of the flyback transformer is made of a material PC40 by selecting sintered magnetic metal oxide.
The current and voltage detection circuit comprises a voltage sampling circuit and a current sampling circuit, wherein the voltage sampling circuit adopts a resistance voltage division circuit, and the current sampling circuit adopts a Hall sensor.
The drive circuit adopts a grid drive chip with isolated high-low side dual-channel output.
A control method for an electrolysis-preventing high-low voltage composite micro pulse power supply comprises the following steps:
the method comprises the following steps: in the gap open circuit stage, the FPGA generates corresponding multi-path PWM signals, after the signals are amplified by the driving circuit, the primary side switch tube is firstly controlled to be conducted, and the high-voltage breakdown switch tube, the negative-voltage anti-electrolysis switch tube and the micro-fine discharge switch tube are simultaneously controlled to be turned off, at the moment, the primary side inductor starts to store energy, and after the energy storage time reaches a set value, the FPGA controls to be turned off and starts to charge each circuit on the secondary side;
step two: when the charging time reaches a set value, the FPGA controls the high-voltage breakdown switch tube to be conducted, the primary side switch tube, the negative-voltage anti-electrolysis switch tube and the micro-fine discharge switch tube are turned off, and at the moment, a proper open-circuit voltage is provided for the gap, so that breakdown occurs when the gap distance is smaller, and a discharge channel is formed;
step three: when the gap breakdown is detected, the gap discharge machining stage is started, the FPGA generates a signal to cut off the high-voltage breakdown switch tube at once, the primary side switch tube and the negative-voltage electrolysis-proof switch tube are still in a turn-off state, the micro-discharge switch tube is controlled to be switched on, the third resistor is a current-limiting resistor, the energy is limited to flow into the gap from a high-voltage breakdown loop, and the discharge capacitor provides machining energy for the gap;
step four: when the discharge time reaches the FPGA preset value, controlling the micro-fine discharge switch tube to be turned off to finish one-time discharge machining, wherein the primary side switch tube, the high-voltage breakdown switch tube and the negative-voltage anti-electrolysis switch tube are in a turned-off state;
step five: after the discharge is finished, the FPGA generates a signal to control the negative voltage to prevent the conduction of the electric disconnecting switch tube, the primary side switch tube, the high-voltage breakdown switch tube and the micro-discharge switch tube are switched off, and a reverse voltage is provided for the gap, so that the deionization process is accelerated, the insulation strength of the interelectrode working solution is restored, the generation of arc discharge is avoided, and the next discharge is ensured to be stable and reliable;
step six: and repeating the five steps to realize the cycle of the processing period.
Compared with the prior art, the invention has the following remarkable advantages: 1) the flyback circuit is adopted to charge the discharge capacitor, and under the condition that the main discharge circuit and the input voltage are not changed, multi-level energy processing within a certain range can be realized by changing the duty ratio of the primary side switching tube, so that the flexibility of the pulse power supply is improved; 2) the secondary windings of the flyback converter are all independently output, have independent breakdown voltage, negative-pressure anti-electrolysis and micro-electro-discharge machining functions, and the input and the output of the original secondary windings are mutually isolated, so that the reliability of micro-electro-discharge machining is greatly increased; 3) the pulse power supply integrally uses a flyback circuit to simultaneously realize the functions of high-voltage breakdown, negative-voltage electrolysis prevention and fine stable processing, greatly reduces the volume of the pulse power supply and improves the utilization rate of the power supply; 4) the FPGA is adopted for control, the control precision is high, the breakdown voltage, the negative pressure adding gap time and the discharge energy are flexible and adjustable, timely modification can be made without changing the hardware of the pulse power supply in the future, the service cycle of the pulse power supply is ensured, and the pulse power supply is not eliminated for a long time.
Drawings
FIG. 1 is a frame diagram of an anti-electrolysis high-low voltage composite micro pulse power supply according to the present invention.
Fig. 2 is a topology diagram of the main circuit of the pulse power supply of the present invention.
Fig. 3 is a schematic diagram of a micro electric spark pulse power source discharge machining waveform according to the present invention.
Fig. 4 is a schematic diagram of a typical application of a hall sensor used in the detection circuit of the present invention.
Fig. 5 is a schematic diagram of a typical application of the double-ended isolated gate driver chip used in the driving circuit of the present invention.
Detailed Description
The invention will be further described with reference to the accompanying drawings and examples.
As shown in fig. 1-2, the anti-electrolysis high-low voltage composite micro pulse power supply of the invention comprises a direct current power supply, a pulse power supply main circuit consisting of a primary circuit, a flyback high-voltage breakdown circuit, a micro pulse power supply main discharge circuit and a negative voltage anti-electrolysis circuit, an FPGA control circuit, a drive circuit and a current and voltage detection circuit, wherein the direct current power supply supplies power to the primary circuit of the pulse power supply main circuit, the micro pulse power supply main discharge circuit and the negative voltage anti-electrolysis circuit; the output of the pulse power supply main discharge circuit, the high-voltage breakdown circuit and the anti-electrolytic circuit is connected to the gap load for workpiece processing, wherein the positive electrodes of the output of the micro pulse power supply main discharge circuit and the output of the high-voltage breakdown circuit are connected with a processing workpiece, the negative electrodes of the output of the micro pulse power supply main discharge circuit and the output of the high-voltage breakdown circuit are connected with a tool electrode, the positive electrodes of the output of the anti-electrolytic circuit are connected with the tool electrode; the current and voltage detection circuit respectively samples the voltage at two ends of the gap and the gap current in real time during processing, and the sampled voltages and the gap current are used as feedback signals to be input to the FPGA control module; the multi-path PWM signals generated by the FPGA module are filtered and amplified by the driving circuit and then drive a switch tube in the pulse power supply main circuit, so that high-voltage breakdown is realized firstly, then the micro pulse power supply main discharge circuit performs discharge machining on the gap, and finally the stable and reliable working state and the corresponding function of next discharge are ensured in an anti-electrolysis manner.
The main circuit of the pulse power supply comprises a primary side switching tube Q1High-voltage breakdown switch tube Q2Negative voltage anti-electrolysis switch tube Q3Fine discharge switching tube Q4Primary side first inductor L1A first resistor R1A first capacitor C1A first diode D1Secondary side second inductor L2A second capacitor C2A second resistor R2A second diode D2A third resistor R3A third diode D3A third inductor L3A third capacitor C3A fourth diode D4A fourth resistor R4A fifth diode D5And a fourth inductor L4A fourth capacitor C4A fifth resistor R5A sixth diode D6The seventh diode D7. Wherein the first resistor R1And a first capacitor C1Connected in parallel, one end is connected with the positive electrode of the power supply, and the other end is connected with the first diode D1Is connected to the cathode of a first diode D1Anode of the primary side switching tube Q1Forming an RCD clamp circuit, a primary side first inductor L1One end of the power supply is connected with the positive electrode of the power supply, and the other end of the power supply is connected with the negative electrode of the power supply; high-voltage breakdown switch tube Q2Secondary side second inductor L2A second capacitor C2A second resistor R2A second diode D2A third resistor R3A third diode D3Form a high-voltage breakdown circuit, and the secondary side second inductor L2One end is connected with a second diode D2The other end of the anode is connected with a second capacitor C2Negative pole of (2), a second diode D2Is connected to the cathodeSecond capacitor C2Positive electrode of (2), second resistor R2And a second capacitor C2Parallel connection; high-voltage breakdown switch tube Q2Drain electrode of the first diode D is connected with the second diode D2The cathode and the source of the second diode are connected with a third diode D3Anode of (2), third diode D3The cathode of the device is connected with a processing workpiece; third resistor R3One end of the second capacitor C is connected with2The other end of the negative electrode is connected with the tool electrode; negative-pressure anti-electrolysis switch tube Q3Secondary side third inductor L3A third capacitor C3A fourth diode D4A fourth resistor R4A fifth diode D5Form a negative-pressure anti-electrolysis circuit, and the secondary side third inductor L3One end is connected with a fourth diode D4The other end of the anode is connected with a third capacitor C3Negative electrode of (1), fourth diode D4Cathode of the first capacitor is connected with a third capacitor C3Positive electrode of (2), fourth resistor R4And a third capacitor C3Parallel connection; negative-pressure anti-electrolysis switch tube Q3Drain electrode of the first diode is connected with a fourth diode D4The source of the cathode is connected with a fifth diode D5Anode of (2), fifth diode D5The cathode of (2) is connected with the tool electrode; the processed workpiece is connected with a third capacitor C3The negative electrode of (1); micro discharge switch tube Q4Secondary side fourth inductor L4A fourth capacitor C4A fifth resistor R5A sixth diode D6The seventh diode D7Form a main discharge circuit of the pulse power supply, and the secondary side fourth inductor L4One end is connected with a sixth diode D6The other end of the anode is connected with a fourth capacitor C4Negative electrode of (1), sixth diode D6Cathode of the first capacitor is connected with a fourth capacitor C4Positive electrode of (2), fifth resistor R5And a fourth capacitor C4Parallel connection; micro discharge switch tube Q4Drain electrode of the first capacitor is connected with a fourth capacitor C4Anode, source connected to seventh diode D7Anode of (2), a seventh diode D7The cathode of the device is connected with a processing workpiece; the tool electrode is connected with a fourth capacitor C4The negative electrode of (1).
Primary side first inductor L in present topology1Secondary side second inductor L2A third inductor L3And a fourth inductor L4Form a flyback transformerA sintered magnetic metal oxide consisting of a mixture of various iron oxides, whose material is PC40, is selected, consisting essentially of iron (Fe), manganese (Mn), and zinc (Zn). The primary and secondary side switch tubes are metal-oxide semiconductor field effect transistors (MOSFET). The primary side switching tube Q is required according to the actual demand of the anti-electrolysis high-low voltage composite micro pulse power supply1High-voltage breakdown switch tube Q2Negative voltage anti-electrolysis switch tube Q3Fine discharge switching tube Q4The N-channel MOSFET with the model number of FCP20N60N and the drain-source voltage resistance V can be selected from ONSemiconductor/Fairchild companyDSUp to 600V, rated current IDThe maximum pulse current is 20A, the allowable maximum pulse current is 20A, the working frequency is up to 5MHz, and the anti-electrolysis high-low voltage composite micro pulse power supply can be used for a high-frequency, medium-low current and low-power anti-electrolysis high-low voltage composite micro pulse power supply. First diode D1A second diode D2A third diode D3A fourth diode D4A fifth diode D5A sixth diode D6And a seventh diode D7The fast recovery diode of ONSemiconductor with the model number MUR1560G is selected and used, and the peak voltage V of the reverse repetition isRRMUp to 600V, average forward current IF(AV)15A, the conduction voltage is reduced to 1.2V, the working frequency can reach 5MHz, and the circuit topology is suitable for high-frequency and medium-low current circuit topologies.
In order to better realize the function of the electrolysis-preventing high-low voltage composite micro pulse power supply designed based on the topology, a proper current and voltage detection circuit, a control module and a driving circuit are also needed. In order to meet the requirements of industry on the stability and reliability of a pulse power supply, voltage sampling adopts resistor voltage division, and a measuring resistor is selected according to actual requirements; the current sampling can be realized by adopting the existing mature Hall sensor, for example, the current Hall sensor which is provided by ACEINNA company and has the model of MCA1101-20-3 can be selected, the detected current range can reach plus or minus 50A to the maximum extent, the bandwidth is 1.5MHz, the sensitivity of the detected current is 60mV/A, the linearity is very good, and the detection precision is very high. FIG. 4 is a schematic diagram of a typical application of MCA1101-20-3, VoutFor the output analog signal, VrefWhen the current is zero, the reference value is output.Through VocThe pin selects a threshold value of current detection, when the threshold value exceeds a detection range, the output of the FAU L TB pin is low level, a low level effective overcurrent signal is provided for the drive circuit, and a hardware-level rapid protection function is realized by matching with the drive circuit.
The FPGA control circuit adopts FPGA (Field-programmable Gate array) control, namely Field-programmable Gate array control, which is a product further developed on the basis of programmable devices such as PA L, GA L, CP L D and the like, and the FPGA control circuit is used as a semi-custom circuit in the Field of Application Specific Integrated Circuits (ASICs), thereby not only solving the defects of the custom circuit, but also overcoming the defect that the number of gate circuits of the original programmable devices is limited1High-voltage breakdown switch tube Q2Negative voltage anti-electrolysis switch tube Q3Fine discharge switching tube Q4Therefore, each working state and corresponding function of the micro pulse power supply are realized.
For the driving circuit, since the secondary side is a multi-output structure, the driving circuit is constructed by using a gate driving chip UCC21521 with isolated high-side and low-side dual-channel outputs from texas instruments, which has a separate dual-channel gate driver with a frequency up to 5Hz, and can simultaneously configure two high-side drivers, which are specially used for driving power MOSFETs, IGBTs, SiC, and the like. A typical application schematic is shown in fig. 5 to drive a primary side switching tube Q1And high-voltage breakdown switch tube Q2For example, the drive signals PWMA and PWMB generated by the FPGA pass through RaAnd CaFiltering, respectively inputting to INA and INB pins of drive chip UCC21521 to generate two independent high-end drive signals, respectively adding to switch tube Q1And Q2G, S end, realize MOSFET's drive, this driver chip can produce the high-end drive of two ways independence simultaneously and control former secondary limit switch tube respectively to primary side and secondary are kept apart, have reduced the interference between main circuit and the control circuit, are fit for very much this design.
The invention relates to an anti-electrolysis high-low voltage composite micro pulse power supply which adopts a flyback circuit topological structure and simultaneously realizes three paths of output, and comprises a high-voltage breakdown circuit, a pulse power supply main discharge circuit and a negative-voltage anti-electrolysis circuit, wherein the output is connected to a gap load, gap voltage and gap current are respectively sampled during processing and are used as feedback quantities to be input to an FPGA control module, corresponding PWM signals are generated according to processing requirements, and switching tubes in each circuit of the pulse power supply are respectively driven to be switched on and off through filtering and amplification of a driving circuit, so that the high-voltage breakdown is firstly realized, then the main discharge circuit carries out discharge processing on a gap, and finally the anti-electrolysis working state is realized, the anti-electrolysis high-low voltage composite micro pulse power supply function is realized, the typical processing waveform is shown in figure 3, and the specific process is as follows:
the method comprises the following steps: in the gap open circuit stage, the FPGA generates a plurality of paths of PWM signals, and the signals are amplified by the driving circuit to control the primary side switching tube Q1Conducting and simultaneously controlling high-voltage breakdown switch tube Q2Negative voltage anti-electrolysis switch tube Q3And a micro discharge switching tube Q4And (3) switching off, wherein the primary inductor starts to store energy at the moment, and the FPGA controls the Q after the energy storage time reaches a set value1And turning off the circuit and starting to charge the circuits on the secondary side.
Step two: when the charging time reaches a set value, the FPGA controls the high-voltage breakdown switch tube Q2Conducting primary side switch tube Q1Negative voltage anti-electrolysis switch tube Q3And a micro discharge switching tube Q4And turning off, wherein a proper open-circuit voltage is provided to the gap, so that breakdown occurs when the gap distance is smaller, and a discharge channel is formed.
Step three: when the gap breakdown is detected, the gap discharge machining stage is started, and the FPGA generates a signal to immediately cut off the high-voltage breakdown switch tube Q2Primary side switch tube Q1Negative voltage anti-electrolysis switch tube Q3Still in the off state, and simultaneously controls the micro-discharge switch tube Q4On, the third resistor R3In order to limit the current of the resistor, the limiting energy flows from the high-voltage breakdown circuit into the gap, and then flows from the discharge capacitor C4Machining energy is supplied to the gap.
Step four: when the discharge time reaches the FPGA preset value, controlling a micro discharge switch tube Q4Turning off to complete one-time discharge machining, wherein the primary side switching tube Q1High-voltage breakdown switch tube Q2And negative-pressure anti-electrolysis switch tube Q3In an off state.
Step five: after the discharge is finished, the FPGA generates a signal to control the negative-pressure anti-electrolysis switch tube Q3Conducting primary side switch tube Q1High-voltage breakdown switch tube Q2And a micro discharge switching tube Q4And (3) switching off, namely, providing a reverse voltage for the gap at the moment, accelerating the deionization process, recovering the insulation strength of the interelectrode working solution, avoiding the generation of arc discharge and ensuring the next discharge to be stable and reliable.
Step six: and repeating the five steps to realize the cycle of the processing period.
In conclusion, the electrolysis-preventing high-low voltage composite micro pulse power supply based on flyback adopts a flyback converter structure to simultaneously realize high-voltage breakdown and electrolysis prevention and micro discharge machining functions on gaps, greatly reduces the size of the power supply and improves the utilization rate of the power supply. One path of flyback output of the secondary side provides enough high open-circuit voltage for the gap, and the open-circuit voltage is used for penetrating the gap before discharging, so that the discharging reliability is ensured; the other path of flyback output is used as a main discharge loop of a micro pulse power supply to provide small and controllable single pulse discharge energy and pulse width, so that the machining precision and the surface quality are ensured; and the last path of flyback output is a negative voltage anti-electrolysis loop, and a negative voltage is connected between the gaps after single pulse discharge, so that the interelectrode working fluid medium can be fully deion, the consistency of next discharge is ensured, and efficient and uniform micro electric discharge machining is realized.
Claims (7)
1. An electrolysis-preventing high-low voltage composite micro pulse power supply is characterized by comprising a direct current power supply, a pulse power supply main circuit, an FPGA control circuit, a driving circuit and a current and voltage detection circuit, wherein the pulse power supply main circuit consists of a primary side circuit, a flyback high-voltage breakdown circuit, a micro pulse power supply main discharge circuit and a negative voltage electrolysis-preventing circuit; the output of the pulse power supply main discharge circuit, the high-voltage breakdown circuit and the anti-electrolytic circuit is connected to the gap load to process the workpiece; the current and voltage detection circuit respectively samples the voltage at two ends of the gap and the gap current in real time during processing, and the sampled voltages and the gap current are used as feedback signals to be input to the FPGA control module; the FPGA module generates a plurality of paths of PWM signals, and the signals are filtered and amplified by the driving circuit and then drive the on-off of a main circuit switching tube of the pulse power supply.
2. The electrolysis-preventing high-low voltage composite micro fine pulse power supply as claimed in claim 1, wherein the pulse power supply main circuit comprises a primary side switching tube (Q)1) High voltage breakdown switch tube (Q)2) Negative voltage anti-electrolysis switch tube (Q)3) The micro discharge switch tube (Q)4) A primary side first inductance (L)1) A first resistor (R)1) A first capacitor (C)1) A first diode (D)1) Secondary side second inductance (L)2) A second capacitor (C)2) A second resistor (R)2) A second diode (D)2) A third resistor (R)3) A third diode (D)3) A third inductor (L)3) A third capacitor (C)3) A fourth diode (D)4) A fourth resistor (R)4) A fifth diode (D)5) And a fourth inductance (L)4) A fourth capacitor (C)4) A fifth resistor (R)5) And a sixth diode (D)6) A seventh diode (D)7) First inductance (L) of primary side1) A secondary side second inductor (L)2) A third inductor (L)3) And a fourth inductance (L)4) Forming a flyback transformer, a first resistor (R)1) And a first capacitance (C)1) Connected in parallel, one end is connected with the positive electrode of the power supply, and the other end is connected with a first diode (D)1) Is connected to the cathode of a first diode (D)1) Anode of the primary side switching tube (Q)1) Forming an RCD clamp, a primary side first inductor (L)1) One end of the power supply is connected with the positive electrode of the power supply, and the other end of the power supply is connected with the negative electrode of the power supply; high-voltage breakdown switch tube (Q)2) A secondary side second inductor (L)2) A second capacitor (C)2) A second resistor (R)2) A second diode (D)2) A third resistor(R3) A third diode (D)3) Forming a high voltage breakdown circuit with a secondary side secondary inductor (L)2) One end is connected with a second diode (D)2) The other end of the anode is connected with a second capacitor (C)2) Negative pole of (D), a second diode (D)2) Cathode of the first capacitor is connected with a second capacitor (C)2) Positive electrode of (2), second resistance (R)2) And a second capacitance (C)2) Parallel connection; high-voltage breakdown switch tube (Q)2) Is connected to the second diode (D)2) The cathode and the source of the second diode (D) are connected with a third diode (D)3) Anode of (D), third diode (D)3) The cathode of the device is connected with a processing workpiece; third resistance (R)3) One terminal is connected with the second capacitor (C)2) The other end of the negative electrode is connected with the tool electrode; negative voltage anti-electrolysis switch tube (Q)3) A secondary side third inductor (L)3) A third capacitor (C)3) A fourth diode (D)4) A fourth resistor (R)4) A fifth diode (D)5) Form a negative-pressure anti-electrolysis circuit, and the secondary side third inductor (L)3) One end is connected with a fourth diode (D)4) The other end of the anode is connected with a third capacitor (C)3) Negative pole of (D), fourth diode (D)4) Is connected with a third capacitor (C)3) Positive electrode of (2), fourth resistor (R)4) And a third capacitance (C)3) Parallel connection; negative voltage anti-electrolysis switch tube (Q)3) Is connected to the fourth diode (D)4) With its cathode and source connected to a fifth diode (D)5) Anode of (D), fifth diode (D)5) The cathode of (2) is connected with the tool electrode; the processed workpiece is connected with a third capacitor (C)3) The negative electrode of (1); micro discharge switch tube (Q)4) A secondary side fourth inductor (L)4) A fourth capacitor (C)4) A fifth resistor (R)5) And a sixth diode (D)6) A seventh diode (D)7) Form a pulse power supply main discharge circuit, and a secondary side fourth inductor (L)4) One end is connected with a sixth diode (D)6) The other end of the anode is connected with a fourth capacitor (C)4) Negative pole of (D), sixth diode (D)6) Cathode of (C) is connected with a fourth capacitor (C)4) Positive electrode of (2), fifth resistor (R)5) And a fourth capacitance (C)4) Parallel connection; micro discharge switch tube (Q)4) Is connected to the fourth capacitor (C)4) Positive electrode, source ofIs connected with a seventh diode (D)7) Anode of (2), a seventh diode (D)7) The cathode of the device is connected with a processing workpiece; the tool electrode is connected with a fourth capacitor (C)4) The negative electrode of (1).
3. The electrolysis-preventing high-low voltage composite micro-pulse power supply as claimed in claim 2, wherein the primary side switching tube (Q)1) High voltage breakdown switch tube (Q)2) Negative voltage anti-electrolysis switch tube (Q)3) The micro discharge switch tube (Q)4) And the metal-oxide semiconductor field effect transistor is adopted, and the material of the metal-oxide semiconductor field effect transistor is Si, SiC or GaN.
4. The anti-electrolysis high-low voltage composite micro-pulse power supply according to claim 2, wherein the magnetic core of the flyback transformer is made of a material selected from a sintered magnetic metal oxide, which is PC 40.
5. The electrolysis-preventing high-low voltage composite micro fine pulse power supply as claimed in claim 2, wherein the current-voltage detection circuit comprises a voltage sampling circuit and a current sampling circuit, wherein the voltage sampling circuit adopts a resistance voltage division circuit, and the current sampling circuit adopts a hall sensor.
6. The electrolysis-preventing high-low voltage composite micro fine pulse power supply as claimed in claim 1, wherein the driving circuit adopts a gate driving chip with isolated high-low side dual channel output.
7. The control and operation principle of the power supply according to any one of claims 1 to 6, wherein the high voltage breakdown circuit and the negative voltage electrolysis-proof circuit with independent outputs cooperate with the micro main discharge circuit to perform pulse discharge, comprising the following steps:
the method comprises the following steps: in the gap open circuit stage, the FPGA generates corresponding multi-path PWM signals, and after the signals are amplified by the driving circuit, the primary side switching tube (Q) is firstly controlled1) Conducting and simultaneously controlling a high-voltage breakdown switch tube (Q)2) Negative voltage anti-electrolysis switch tube (Q)3) And fine dischargeElectric switch tube (Q)4) And (3) turning off, wherein the primary inductor starts to store energy at the moment, and the FPGA controls (Q) after the energy storage time reaches a set value1) Turning off and starting to charge each circuit on the secondary side;
step two: when the charging time reaches a set value, the FPGA controls a high-voltage breakdown switch tube (Q)2) Conducting, primary side switch tube (Q)1) Negative voltage anti-electrolysis switch tube (Q)3) And a micro discharge switching tube (Q)4) Turning off, and providing proper open-circuit voltage to the gap to break down when the gap distance is smaller to form a discharge channel;
step three: when the gap breakdown is detected, the gap discharge machining stage is started, and the FPGA generates a signal to cut off a high-voltage breakdown switch tube (Q)2) Primary side switch tube (Q)1) Negative voltage anti-electrolysis switch tube (Q)3) Still in the off state, and simultaneously controls the micro discharge switch tube (Q)4) On, the third resistance (R)3) In order to limit the current of the resistor, the limiting energy flows from the high-voltage breakdown circuit into the gap, and then from the discharge capacitor (C)4) Providing machining energy to the gap;
step four: when the discharge time reaches the FPGA preset value, controlling a micro discharge switch tube (Q)4) Turning off to complete one-time discharge machining, wherein the primary side switch tube (Q) is1) High voltage breakdown switch tube (Q)2) And negative-pressure anti-electrolysis switch tube (Q)3) In an off state;
step five: after the discharge is finished, the FPGA generates a signal to control a negative-pressure anti-electrolysis switch tube (Q)3) Conducting, primary side switch tube (Q)1) High voltage breakdown switch tube (Q)2) And a micro discharge switching tube (Q)4) Turning off, namely providing a reverse voltage for the gap, accelerating the deionization process, recovering the insulation strength of the interelectrode working solution, avoiding the generation of arc discharge and ensuring the next discharge to be stable and reliable;
step six: and repeating the five steps to realize the cycle of the processing period.
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Application publication date: 20200717 |