CN111431432A - A Micro EDM Pulse Power Supply Based on Boost and RC Circuit - Google Patents

Abstract

The invention discloses a fine electric spark pulse power supply based on Boost and RC circuits, which is characterized in that it includes a main power circuit, a drive circuit, an auxiliary DC voltage source, and an FPGA controller, and the main power circuit includes a boost charging circuit and an FPGA controller. A discharge circuit, in which the boost charging circuit adopts a Boost circuit, which is used to adjust the voltage provided by the auxiliary DC voltage source and charge the discharge circuit; the discharge circuit adopts an RC circuit to provide a breakdown voltage for the gap and discharge after the breakdown energy; the auxiliary DC voltage source is used to supply power to the main power loop and the drive circuit; the FPGA controller is used to output the PWM control signal to the drive circuit according to the given target parameters; the drive circuit digitally isolates and amplifies the PWM control signal to generate the drive The signal drives the switch on and off in the main power loop. The invention improves the controllability of the charging voltage and the energy regulation precision, and improves the processing precision and processing quality.

Description

A Micro EDM Pulse Power Supply Based on Boost and RC Circuit

technical field

The invention relates to a high-frequency pulse power supply, in particular to a fine electric spark pulse power supply based on Boost and RC circuits.

Background technique

Pulse power supply is a core part of EDM machine tools. The design of pulse power supply has an important influence on the roughness of the machined surface, the degree of damage to the tool electrode, the machining accuracy, the machining efficiency and the power utilization rate. The high requirements for machining accuracy mean that the energy of a single discharge of the pulse power supply should be small enough, and the energy can be fine-tuned. At present, the micro-EDM pulse power supply on the market mostly adopts a relaxation topology, and its single discharge energy is small, suitable for It is suitable for micromachining, but the energy is uncontrollable and the processing efficiency is low.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a fine electric spark pulse power supply based on Boost and RC circuit.

The technical solution to achieve the purpose of the present invention is: a micro-electric spark pulse power supply based on Boost and RC circuits, including a main power loop, a drive circuit, an auxiliary DC voltage source, and an FPGA controller, and the main power loop includes boost charging. Circuit and discharge circuit, wherein the boost charging circuit adopts the Boost circuit to adjust the voltage provided by the auxiliary DC voltage source and charge the discharge circuit; the discharge circuit adopts the RC circuit to provide the breakdown voltage for the gap and after the breakdown The auxiliary DC voltage source is used to supply power to the main power loop and the drive circuit; the FPGA controller is used to output the PWM control signal to the drive circuit according to the given target parameters; the drive circuit digitally isolates and amplifies the PWM control signal, A drive signal is generated to drive the switch on and off in the main power loop.

The boost charging circuit includes a first switch transistor Q ₁ , a second switch transistor Q ₂ , a first inductor L ₁ , an input capacitor C _in , a first diode D ₁ , an output capacitor C _out , and the input capacitor C _{in in} parallel At the positive and negative ends of the auxiliary DC voltage source, one section of the auxiliary DC voltage source is grounded, the other end is connected to the _first inductor L1, the other end of the _first inductor L1 is connected to the _first switch tube Q1, and the first anti-backflow diode _The anode of D1 is connected to the connection point between the _first inductor L1 and the _first switch Q1, the cathode is connected to the _second switch _Q2 , and the other end of the second switch Q2 is connected to the output capacitor _Cout , The other end of the capacitor C _out is grounded.

The discharge loop includes a third switch tube Q ₃ , a fourth switch tube Q ₄ , a deionization switch tube Q ₅ , a charging resistor R _ch , a charging capacitor C _ch , a second diode D ₂ , the charging resistor R _ch and Boost The output end of the circuit is connected, the other end is connected to the third switch tube _Q3 , the other end of the third switch tube _Q3 is connected to the charging capacitor _Cch , the other end of the charging capacitor _Cch is grounded, the fourth switch tube _Q4 and The third switch tube _Q3 is connected to the connection point of the charging capacitor _Cch , the other end is connected to the anode of the _second anti-backflow diode D2, the cathode of the diode is connected to the gap, and the deionization switch tube _Q5 is connected in parallel to both ends of the gap.

The first switch tube Q ₁ and the second switch tube Q ₂ are N-channel MOSFETs with the model IPP60R74C6 from infineon company.

The third switch tube Q ₃ , the fourth switch tube Q ₄ , and the deionization switch tube Q ₅ are selected from ON Semiconductor's N-channel MOSFET with the model FCP165N65S3.

The _first inductance L1 is selected from Sunlord's model MPH201206S1R0MT.

The diode selected is FFP30S60S.

The selected model of the FPGA is EP4CE15F23C8.

A gap machining method for a micro-EDM pulse power supply based on Boost and RC circuits, the specific steps are as follows:

Step 1: The FPGA controller generates multiple PWM signals. After amplification by the drive circuit, the first switch of the main power loop is turned on, the fourth switch is turned on, the second switch is turned off, and the third switch is turned off. Turn off, the fifth switch tube is turned off. At this time, in the Boost circuit, the DC voltage charges the first inductor, the Boost circuit boosts the voltage, and the RC circuit discharges at the same time. When the gap voltage reaches the gap breakdown voltage, the gap breaks down and discharges;

Step 2: When the output voltage of the boost circuit reaches the set threshold, it switches to the RC charging mode, and the controller FPGA generates the corresponding multi-channel PWM signals. After amplification by the driving circuit, the first switch tube of the main power loop is driven to turn off. off, the fourth switch tube is turned off, the second switch tube is turned on, the third switch tube is turned on, and the fifth switch tube is turned off. At this time, the RC charging circuit is turned on, and the output voltage of the Boost circuit is used to charge the RC circuit. Capacitor charging, when RC charging is completed, switch to Boost circuit boost and RC circuit discharge mode;

Step 3: After the RC discharge is completed, the gap is deionized before entering the next discharge cycle. The controller FPGA generates the corresponding PWM signal, which is amplified by the driving circuit to drive the first switch tube and the second switch of the main power loop. The tube, the third switch tube and the fourth switch tube are turned off, and the fifth switch tube is turned on, so that the voltage across the gap is zero, and it enters the deionization stage to prepare for the next cycle of discharge;

Step 4: Repeat the above three steps to realize the cycle of the processing cycle.

Compared with the prior art, the present invention has the following significant advantages: 1) the discharge energy of the micro-electric spark pulse power supply of the present invention is very small, and the energy can be fine-tuned, and the controllability is strong; 2) the Boost circuit combination RC proposed by the present invention In the circuit topology of the pulse power supply, the RC charging circuit and the discharging circuit are placed in each of the switch tubes to achieve energy controllability. The circuit structure is simple. Compared with the traditional topology, it is easier to achieve high-frequency discharge and improve the energy efficiency of the system; 3) This The invention of the micro-electric spark pulse power supply adds a boost circuit part between the auxiliary DC voltage source and the RC, which can not only fine-tune the energy by controlling the output voltage, but also reduce the performance requirements of the DC voltage source to a certain extent.

Description of drawings

FIG. 1 is a structural block diagram of a micro-EDM pulse power supply based on Boost and RC circuits of the present invention.

FIG. 2 is a topology diagram of the Boost circuit of the present invention.

FIG. 3 is a topology diagram of the RC circuit of the present invention.

FIG. 4 is a schematic diagram of the driving circuit of the present invention.

5 is a schematic diagram of the discharge waveform of the micro-EDM finishing pulse power supply of the present invention.

Detailed ways

The solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

As shown in Figure 1, a micro-EDM pulse power supply based on Boost and RC circuits includes a main power circuit, a drive circuit, an auxiliary DC voltage source, and an FPGA controller, and the main power circuit includes a boost charging circuit and a discharging circuit, The boost charging circuit adopts the Boost circuit, which is used to adjust the voltage provided by the auxiliary DC voltage source and charge the discharge circuit; the discharge circuit adopts the RC circuit to provide the breakdown voltage and the discharge energy after the breakdown to the gap; the auxiliary The DC voltage source is used to supply power to the main power circuit and the drive circuit; the FPGA controller is used to output the PWM control signal to the drive circuit according to the given target parameters; the drive circuit digitally isolates and amplifies the PWM control signal to generate a drive signal to drive the main circuit. The turn-on and turn-off of switches in the power loop.

As shown in FIG. 2 , the boost charging circuit adopts a Boost circuit, which includes a first switch tube Q ₁ , a second switch tube Q ₂ , a main power inductor, a first inductor L ₁ , and an input voltage regulator capacitor and an input capacitor C _in , 1 anti-backflow diode, the first diode D ₁ , and an output voltage regulator capacitor C _out . Through the adjustment of the duty cycle, the output voltage adjustment accuracy can reach 1V. The input capacitor C _in is connected in parallel with the positive and negative ends of the auxiliary DC voltage source, a section of the auxiliary DC voltage source is grounded, the other end is connected to the first inductor L ₁ , and the other end of the first inductor L ₁ is connected to the first switch tube Q ₁ , The anode of the _first anti-backflow diode D1 is connected to the connection point of the _first inductor L1 and the _first switch tube Q1, the cathode is connected to the _second switch tube _Q2 , and the other end of the second switch tube Q2 is connected to the output The capacitor C _out is connected, the other end of the capacitor C _out is grounded, the output capacitor C _out of the Boost circuit is connected with the input end of the RC circuit, and the voltage provided by the auxiliary DC voltage source is further adjusted by controlling the Boost circuit, and the capacitor in the discharge loop is charged. . By changing the output voltage value of the Boost circuit, the energy released in the RC circuit during the breakdown of the gap is adjusted, and because the Boost circuit can make small adjustments to the voltage across the charging capacitor, it can meet the requirements of fine-tuning the gap energy level and improve the system. controllability.

As shown in FIG. 3 , the discharge circuit adopts an RC circuit, which includes a third switch tube Q ₃ , a fourth switch tube Q ₄ , a charging resistor R _ch , a charging capacitor C _ch , an anti-backflow diode, a second diode D _2. Deionization switch tube _Q5 . The charging resistor _Rch is connected to the output end of the Boost circuit, the other end is connected to the third switch tube _Q3 , the other end of the third switch tube _Q3 is connected to the charging capacitor _Cch , the other end of the charging capacitor _Cch is grounded, and the first The four switch tubes _Q4 and the third switch tube _Q3 are connected to the connection point of the charging capacitor _Cch , the other end is connected to the anode of the _second anti-backflow diode D2, the cathode of the diode is connected to the gap, and the deionization switch tube _Q5 is connected in parallel with the gap both ends. By turning on the third switch tube _Q3 on the RC charging circuit, the charging capacitor _Cch is charged. After the charging is completed, the third switch tube _Q3 is turned off, and the _fourth switch tube Q4 is turned on. When the gap voltage reaches the breakdown voltage, the gap breaks down and discharges to achieve the ablation of the workpiece; the deionization switch Q ₅ is connected in parallel at both ends of the gap. After the discharge, the gap voltage is pulled to 0V to provide the gap current. Fast deionization path.

In the main power loop, the switches Q ₁ and Q ₂ are N-channel MOSFETs of infineon's model IPP60R74C6, the drain-source withstand voltage V _DS is as high as 600V, the rated current I _D is 57.7A, and the operating frequency is as high as 1MHz. It can be used in micro EDM with high frequency, high voltage and small current. The switches Q ₃ , Q ₄ , and Q ₅ are N-channel MOSFETs of ON Semiconductor's model _FCP165N65S3 , whose drain-source withstand voltage V _DS is as high as 650V, and the rated current ID is 19A. The first inductor is MPH201206S1R0MT from Sunlord, with an inductance value of 1μH, the diode is FFP30S60S, the reverse withstand voltage is 600V, and the forward continuous conduction current is 30A.

The signals that control the on-off of the MOS tube in the power loop are all generated by the FPGA controller. In the present invention, the model of FPGA is EP4CE15F23C8, which is a high-speed processor of CycloneIV series of Altera Corporation, its clock frequency is as high as 472MHz, and it is equipped with two high-speed, high-precision AD conversion chips for sampling signal input.

As shown in Figure 4, for the drive circuit, the present invention adopts a high- and low-end drive chip with its own isolation. Here, a gate drive IC chip with the model UCC21521 introduced by Texas Instruments is used, which accepts the PWM output signal of the FPGA, and is amplified by the drive chip. , and then drive the switch in the power loop. It is a dual-channel, high-speed, internally isolated, gate driver chip with enable pins, bandwidth up to 5MHz, isolation voltage up to 5.7kV, and surge anti-interference voltage of 12.8kV. This driver chip can generate high-end and low-end drives at the same time, and the primary and secondary sides are isolated, which reduces the interference between the main circuit and the control circuit.

The present invention is based on the Boost and RC circuit of the micro-electric spark pulse power supply, and the Boost circuit is used to fine-tune the charging voltage, so as to realize the micro-control of the energy level, and improve the controllability and precision of the processing; the Boost circuit can increase the charging voltage, so it is not necessary to The auxiliary DC voltage source provides high voltage, which has loose voltage requirements and flexible and reliable control. A diode is connected in series on the output side of the RC type circuit to prevent the gap voltage from oscillating and current reverse occurs. The RC circuit has a simple structure, capacitor energy storage, and no resistance. ,Energy efficient.

Figure 5 is a schematic diagram of the gap voltage and current waveforms of a machining cycle. In a switching cycle, the arc initiation stage starts at the beginning. After the charging capacitor is charged, when the voltage across the gap reaches the breakdown voltage, the gap breakdown occurs, and the gap voltage It rapidly drops to the maintenance voltage, and the gap current also rises rapidly at this time. This process is the gap breakdown discharge. When the gap current returns to 0, the gap discharge process ends, and the gap enters the deionization stage. The working process of the micro-EDM pulse power supply based on Boost and RC circuit, the specific steps are as follows:

Step 1: The corresponding multi-channel PWM signal is generated by the controller FPGA. After amplification by the driving circuit, the first switch of the main power loop is turned on, the fourth switch is turned on, the second switch is turned off, and the third switch is turned off. The switch tube is turned off, and the fifth switch tube is turned off. At this time, in the Boost circuit, the DC voltage charges the first inductor, and the Boost circuit boosts the voltage. In the boost stage, the third switch of the RC circuit is turned off, the fourth switch is turned on, the charging loop is turned off, the discharge loop is turned on, and the charging capacitor is discharged. The discharge process in the RC circuit is carried out at the same time. When the gap voltage When the gap breakdown voltage is reached, the gap breakdown discharge. The charging time can be determined by calculating the output voltage value required by the actual production. When the charging time of the first inductor is over, the first switch is turned off, the second switch is turned on, and the Boost circuit provides the RC circuit with a forward input voltage that can be precisely adjusted.

Step 2: When the output voltage of the boost circuit reaches the set threshold, it switches to the RC charging mode. The corresponding multi-channel PWM signal is generated by the controller FPGA. After amplification by the driving circuit, the first switch of the main power circuit is turned off, the fourth switch is turned off, the second switch is turned on, and the third switch is turned on. On, the fifth switch is turned off. The RC charging loop is turned on, and the charging capacitor in the RC circuit is charged by the output voltage of the Boost circuit. By controlling the amount of charging energy in the RC circuit, the energy released at the gap and the roughness of the workpiece surface can be adjusted. When the RC charging is completed, switch to the boost circuit boost and RC circuit discharge mode;

Step 3: After the RC discharge is completed, the gap needs to be deionized before entering the next discharge cycle. The controller FPGA generates the corresponding PWM signal, which is amplified by the drive circuit to drive the first switch tube and the second switch of the main power loop. The switch tube, the third switch tube, and the fourth switch tube are turned off, and the fifth switch tube is turned on, so that the voltage across the gap is zero, and the deionization stage is entered to prepare for the next cycle of discharge.

Step 4: Repeat the above three steps to realize the cycle of the processing cycle.

Claims (9)

1. A micro electric spark pulse power supply based on a Boost circuit and an RC circuit is characterized by comprising a main power loop, a driving circuit, an auxiliary direct current voltage source and an FPGA controller, wherein the main power loop comprises a Boost charging circuit and a discharging loop, and the Boost charging circuit adopts the Boost circuit and is used for adjusting the voltage provided by the auxiliary direct current voltage source and charging the discharging loop; the discharge loop adopts an RC circuit to provide breakdown voltage and discharge energy after breakdown for the gap; the auxiliary direct-current voltage source is used for supplying power to the main power loop and the driving circuit; the FPGA controller is used for outputting a PWM control signal to the drive circuit according to a given target parameter; the driving circuit carries out digital isolation and amplification on the PWM control signal to generate a driving signal to drive the switch tube in the main power loop to be switched on and switched off.

2. The Boost and RC circuit based fine spark-erosion pulse power supply of claim 1, wherein the Boost charging circuit comprises a first switching tube (Q)₁) A second switch tube (Q)₂) A first inductor (L)₁) Input capacitance (C)_in) A first diode (D)₁) Output capacitance (C)_out) Input capacitance (C)_in) Connected in parallel to the positive and negative ends of the auxiliary DC voltage source, the auxiliary DC voltage source has a first end grounded and the other end connected to the first inductor (L)₁) Connected to each other, a first inductance (L)₁) The other end is connected with a first switch tube (Q)₁) Connected, a first anti-reflux diode (D)₁) And a first inductor (L)₁) And a first switch tube (Q)₁) Is connected with the cathode of the second switch tube (Q)₂) Connected to a second switching tube (Q)₂) Another terminal of (C) and an output capacitor (C)_out) Connection, capacitance (C)_out) The other end is grounded.

3. Fine spark-pulse power supply based on Boost and RC circuit according to claim 1 characterized in that the discharge loop comprises a third switching tube (Q)₃) And a fourth switching tube (Q)₄) Deionization switch tube (Q)₅) Charging resistor (R)_ch) And a charging capacitor (C)_ch) A second diode (D)₂) Charging resistance (R)_ch) Connected with the output end of the Boost circuit, and the other end is connected with a third switching tube (Q)₃) Connected, a third switching tube (Q)₃) Another terminal of (C) and a charging capacitor (C)_ch) Connected to charge a capacitor (C)_ch) Is grounded, a fourth switching tube (Q)₄) And a third switching tube (Q)₃) And a charging capacitor (C)_ch) Is connected with the other end of the first reverse current prevention diode (D)₂) Anode of (2), cathode connection gap of diode, deionization switch tube (Q)₅) Connected in parallel at both ends of the gap.

4. According to claim 2The micro electric spark pulse power supply based on the Boost circuit and the RC circuit is characterized in that the first switching tube (Q)₁) A second switch tube (Q)₂) An N-channel MOSFET model IPP60R74C6 from infineon was chosen.

5. Fine spark-pulse power supply based on Boost and RC circuit according to claim 3 characterized by the third switching tube (Q)₃) And a fourth switching tube (Q)₄) Deionization switch tube (Q)₅) An N-channel MOSFET from ON Semiconductor, model FCP165N65S3, was selected.

6. The Boost and RC circuit based fine spark-pulse power supply according to claim 2, characterized in that the first inductance (L)₁) The model number of Sunlord company is MPH201206S1R0 MT.

7. The Boost and RC circuit based fine spark pulse power supply of claim 2 or 3, wherein the diode is selected as FFP30S 60S.

8. The Boost and RC circuit based fine electric spark pulse power supply of claim 1, wherein the FPGA is selected to be EP4CE15F23C8.

9. A gap machining method of a micro electric spark pulse power supply based on a Boost circuit and an RC circuit is characterized by comprising the following specific steps:

the method comprises the following steps: the FPGA controller generates multiple paths of PWM signals, and the signals are amplified by the driving circuit to drive a first switching tube (Q) of the main power loop₁) Conducting, fourth switching tube (Q)₄) Conducting, second switch tube (Q)₂) Off, third switching tube (Q)₃) Off, fifth switching tube (Q)₅) And turning off the direct current voltage to the first inductor (L) in the Boost circuit₁) Charging, namely boosting the voltage of a Boost circuit, discharging the RC circuit at the same time, and when the gap voltage reaches the gap breakdown voltage, performing gap breakdown discharging;

step two: when the output voltage of the Boost circuit reaches a set threshold value, the Boost circuit is switched to an RC (resistor-capacitor) charging mode, a controller FPGA (field programmable gate array) generates corresponding multi-path PWM (pulse width modulation) signals, and the multi-path PWM signals are amplified by a driving circuit to drive a first switching tube (Q) of a main power loop₁) Off, fourth switching tube (Q)₄) Off, second switching tube (Q)₂) Conducting, third switching tube (Q)₃) Conducting, fifth switching tube (Q)₅) Turn off, at which time the RC charging circuit is turned on and the output voltage (V) of the Boost circuit is used_out) Charging a capacitor (C) in an RC circuit_ch) Charging, namely switching to Boost modes of a Boost circuit and discharging modes of an RC circuit after RC charging is finished;

step three: after RC discharge is finished, the gap is deionized before entering the next discharge period, the controller FPGA generates a corresponding PWM signal, and the PWM signal is amplified by the driving circuit to drive a first switching tube (Q) of the main power loop₁) A second switch tube (Q)₂) And a third switching tube (Q)₃) And a fourth switching tube (Q)₄) Off, fifth switching tube (Q)₅) Conducting to enable the voltage at the two ends of the gap to be zero, entering a deionization stage and preparing for discharging in the next period;

step four: and repeating the three steps to realize the cycle of the processing period.

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