Electron beam high-speed deflection scanning driving circuit

Abstract

The invention provides an electron beam high-speed deflection scanning drive circuit which is composed of an industrial personal computer, a DSP control circuit, a photoelectric isolation circuit, a PID closed-loop adjusting circuit, a power amplifier, a power MOSFET and a deflection coil. A parallel output structure of a plurality of power MOSFETs and a power amplifier is adopted, and the total power consumption of the high-voltage large-current driving circuit is shared to each power MOSFET and the power amplifier, so that the problem that thermal failure of a device is easily caused by overlarge consumed power of a single power amplifier is solved, and the working reliability of the high-voltage large-current high-speed driving circuit is improved; the power consumption of a single power device is reduced, the voltage of the power supply of the driving circuit can be further improved, the change speed of the driving current is improved again, and higher electron beam deflection scanning speed is realized; and the output current of the power amplifier is reduced, so that the current value of closed-loop PID adjustment of the current of the driving circuit is reduced, and high-precision, large-range and high-speed deflection scanning of the electron beam is realized.

Description

TECHNICAL FIELD

[0001] The application provides an electron beam deflection scanning driving circuit, in particular a high-speed electron beam deflection scanning driving circuit, which is used for driving a deflection scanning coil and controlling high-speed electron beam deflection scanning and belongs to the technical field of electron beam current processing. BACKGROUND

[0002] The electron beam selective melting additive manufacturing technology uses high-speed electron beam deflection scanning to realize substrate and powder preheating and finally melt the powder to form a part, has the advantages of high forming precision, small thermal stress and the like, is suitable for near-net forming manufacturing of refractory and high-performance metal materials such as titanium alloy and titanium aluminum base alloy, and has a wide application in manufacturing of aerospace high-performance complex parts and manufacturing of porous structure medical implants. In the electron beam selective melting additive manufacturing technology, the high-speed deflection scanning system is an important core component of the electron beam selective melting additive equipment, mainly including a deflection scanning coil and a deflection scanning driving circuit; in the case of the determined deflection scanning coil, the current change speed of the deflection scanning driving circuit driving the coil determines the electron beam deflection scanning speed, and further determines the forming efficiency of the part. In theory, the faster the current speed change of the deflection scanning driving circuit, the more conducive to improving the forming efficiency of the part, and the more flexible the electron beam deflection scanning preheating and part forming control, and the control strategy for improving the part forming quality can be more flexibly implemented.

[0003] In the prior art, low-voltage power amplifiers are mostly used to drive deflection scanning coils, the driving voltage is low, the driving current is small, and the change speed of the driving current is slow, so that the scanning speed of the electron beam is also slow, and scanning traces are easily left in the scanning process, which is not conducive to the machining of precision parts. In order to improve the deflection scanning speed of the electron beam, the patent ZL201611048932.9 uses a high-voltage and high-current power amplifier PA93 and a ±160V DC power supply to drive the deflection scanning coil, and uses high voltage to excite the deflection scanning coil to improve the change speed of the driving current, and then realizes high-speed deflection scanning of the electron beam. However, since the number of turns of the deflection scanning coil is not many, the AC inductance is large, and the DC resistance is generally less than 2Ω, so in actual work, when the scanning speed of the electron beam is slow or the constant current is maintained at a certain deflection angle, most of the power is dissipated on the power amplifier, which is easy to exceed the maximum dissipation power of PA93 and cause PA93 to overheat and burn out. Taking a 2A scanning current as an example, the coil resistance is 2Ω, at this time the voltage drop on the coil is only 4V, and when the ±160V power supply is used, the output voltage of the power amplifier PA93 is only 4V, and most of the voltage drop is in the power amplifier. At this time, the dissipation power of PA93 will exceed 300W, and the maximum dissipation power of the actual PA93 is only 125W, so PA93 is easy to burn out in short-time work. Therefore, it is difficult to realize both rapid change of current and large current output by using a high-voltage and high-current power amplifier. In essence, in order to ensure the reliable work of PA93, the output current cannot be too large when working at high voltage, and must work in the safe working area to ensure that the loss power is lower than the maximum dissipation power of PA93. Furthermore, the PID regulation circuit is used for closed-loop control of the driving current, and the overshoot of the current is generally related to the amplitude of the current. When the output current is large, it is difficult to control the overshoot to be small, which directly affects the control accuracy of the output current. In addition, the price of the high-voltage and high-current power amplifier is generally high and not easy to purchase, which is not conducive to cost reduction and shortening of the development cycle.

[0004] The present application designs an electron beam high-speed deflection scanning driving circuit, which can realize high-precision, large-range and high-speed deflection scanning of the electron beam. SUMMARY

[0005] 1. Object: The object of the present application is to provide an electron beam high-speed deflection scanning driving circuit. It uses power MOSFET constant current control technology, multiple power MOSFETs and high-voltage power amplifiers in parallel output structure, and PID closed-loop control technology, which can realize high-speed and large-current driving of the deflection scanning coil, and thus realize high-precision, large-range and high-speed deflection scanning of the electron beam.

[0006] The "MOSFET" refers to a metal-oxide semiconductor field effect transistor, abbreviated as metal oxide semiconductor field effect transistor (MOSFET);

[0007] The "PID" refers to proportional-integral-derivative control, abbreviated as PID control.

[0008] 2. Technical scheme: The purpose of the application is realized by the following technical scheme.

[0009] Based on the above purpose, the application provides an electron beam high-speed deflection scanning driving circuit, comprising: an industrial computer (101), a serial communication circuit (102), a DSP control circuit (103), an optical signal isolation circuit I (104), an optical signal isolation circuit II (113), a constant current control circuit I (105), a constant current control circuit II (114), a power MOSFET-I (106), a power MOSFET-II (115), a high-speed high-precision DA conversion circuit I (107), a high-speed high-precision DA conversion circuit II (116), a PID regulating circuit I (108), a PID regulating circuit II (117), a power amplifier OPA548-I (109), a power amplifier OPA548-II (118), an X-direction output current sensor (111), a Y-direction output current sensor (120), an X-direction commutation circuit and deflection coil (110), a Y-direction commutation circuit and deflection coil (119), a power supply +VCC1 (112), a power supply +VCC2 (121); the positional connection relationship between them is: the industrial computer (101) is connected to the DSP control circuit (103) through the serial communication circuit (102), realizing the transmission of deflection scanning data; the DSP control circuit (103) processes the received digital signal and converts it into SPI signal and I / O signal; wherein the SPI signal 1 is transmitted to the high-speed high-precision DA conversion circuit I (107) after passing through the optical signal isolation circuit I (104) and converted into an analog voltage signal output, the signal is transmitted to the PID regulating circuit I (109) and used as the scanning current waveform input of the X-direction deflection coil (205) given I Xg The output U XgThe in-phase input end connected to the power amplifier OPA548-I (109) is connected in parallel with the constant current output circuit of the power MOSFET-I (106) after power amplification; meanwhile, the I / O signal 1 is transmitted to the constant current control circuit I (105) after passing through the photoelectric signal isolation circuit I (104) and controls the constant current output of the power MOSFET-I (106); the output current of the power MOSFET-I (106) is connected in parallel with the output current of the power amplifier OPA548-I (109) and then connected to the X-direction commutation circuit and deflection coil (110) through the X-direction output current sensor (111), so as to realize the high-speed current drive of the X-direction deflection coil (205); the commutation control signals PWM11 and PWM12 are connected to the X-direction commutation circuit and deflection coil (110) to control the on and off of the power switch tube and realize the forward and reverse flow control of the deflection coil current. Similarly, the SPI signal 2 is converted into an analog voltage signal output after passing through the photoelectric signal isolation circuit II (113) and being transmitted to the high-speed high-precision DA conversion circuit II (116); the signal is transmitted to the PID regulation circuit II (117) as the scanning current waveform input of the Y-direction deflection coil Yg The output U Yg The in-phase input end connected to the power amplifier OPA548-II (118) is connected in parallel with the constant current output circuit of the power MOSFET-II (115) after power amplification; meanwhile, the I / O signal 2 is transmitted to the constant current control circuit II (114) after passing through the photoelectric signal isolation circuit II (113) and controls the constant current output of the power MOSFET-II (115); the output current of the power MOSFET-II (115) is connected in parallel with the output current of the power amplifier OPA548-II (118) and then connected to the Y-direction commutation circuit and deflection coil (119) through the Y-direction output current sensor (120), so as to realize the high-speed current drive of the Y-direction deflection coil; the commutation control signals PWM21 and PWM22 are connected to the Y-direction commutation circuit and deflection coil (119) to control the on and off of the power switch tube and realize the forward and reverse flow control of the deflection coil current.

[0010] The "DSP" refers to: digital signal processing, which is the abbreviation of English Digital Signal Processing;

[0011] The "SPI" refers to: serial peripheral interface (Serial Peripheral Interface), which is a full-duplex synchronous serial bus developed by Motorola (Motorola) company;

[0012] The "I / O" refers to: input (Input) / output (Output), abbreviated as "I / O".

[0013] The "DA" refers to: digital signal (Digital) into analog signal (Analog), abbreviated as DA;

[0014] The industrial computer (101) uses Advantech IPC-610L industrial computer;

[0015] The serial communication circuit (102) uses the 485 serial bus (RS-485) interface on the industrial computer, which transmits the deflection scanning data of the industrial computer to the DSP control circuit through the serial interface;

[0016] The DSP control circuit (103) uses the STM32G474VET6 chip of ARM Company as the main control circuit, which mainly receives the deflection scanning data transmitted by the industrial computer, then processes the data, converts it into the corresponding deflection scanning coil driving current given value and I / O control signal, and then transmits it to the high-speed high-precision DA conversion circuit, constant current control circuit and commutation control circuit through the SPI communication interface and I / O interface respectively;

[0017] The "ARM" company refers to: Arm Limited (or its affiliates), namely ARM Limited or its affiliates, is a chip architecture design company under the Software Bank Group.

[0018] The "STM32G474VET6" refers to a 32-bit micro control processor produced by ARM Company with model number STM32G474VET6.

[0019] The photoelectric signal isolation circuit I (104) and the photoelectric signal isolation circuit II (113) have the same structure, both of which are composed of three groups of SPI communication isolation circuits and two groups of constant current control isolation circuits with the same structure, which realize the photoelectric isolation of SPI serial communication and constant current control I / O signal; each group of photoelectric isolation circuit includes photoelectric isolation integrated circuit 6N137 (401), input current limiting resistor R5 (402), output pull-up resistor R6 (403), transistor pull-up resistor R7 (404), output transistor Q9 (405), which functions to isolate the digital signals of SPI serial communication and constant current control I / O through photoelectric coupling, realize the isolated transmission of SPI communication signal, and realize the constant current driving of high-voltage MOSFET power tube T1 and T2;

[0020] The "6N137" refers to: a type of photoelectric isolation integrated circuit produced by On-Semiconductor Company;

[0021] The high-speed high-precision DA conversion circuit I (107) and the high-speed high-precision DA conversion circuit II (116) are the same structure, both of which adopt the DAC8560 conversion circuit, the DAC8560 is a low-power, voltage output, single-channel, 16-bit, 3-wire SPI serial DA conversion circuit, the serial communication rate is 30MHz, the DA output voltage can be quickly set, and the main function is to convert the SPI serial communication signal transmitted from the photoelectric signal isolation circuit I (104) and the photoelectric signal isolation circuit II (113) into an analog voltage signal I Xg and I Yg output;

[0022] The "DAC8560" refers to: a model of SPI serial communication integrated circuit, the DAC8560 is a low-power, voltage output, single-channel, 16-bit, 3-wire serial DA conversion circuit, and the serial communication rate is 30MHz integrated circuit;

[0023] The PID adjustment circuit I (108) and the PID adjustment circuit II (117) are composed of an operational amplifier, a proportional amplification resistor, an integral capacitor and a differential capacitor, which are used to adjust the drive current on the X-direction and Y-direction deflection coils, and the output U Xg and U Yg is connected to the power amplifier OPA548-I (109) and the power amplifier OPA548-II (118), and is amplified again as the input of the power amplifier;

[0024] The power amplifier OPA548-I (109) and the power amplifier OPA548-II (118) are the same structure, including the integrated power amplifier OPA548 (209), the output diode D1 (210), the proportional amplification resistors R1 (211), R2 (212), R3 (213) and R4 (214), and the main function is to form a power amplification circuit to amplify the input U Xg and U Yg again, realize the amplification of voltage and drive current, and the output is in parallel with the MOSFET power tube T1 (201) and the MOSFET power tube T2 (202) output current, so that the total output current I X =I1+I2+I3;

[0025] The constant current control circuit I (105) and the constant current control circuit II (114) are the same structure, which is composed of two groups of the same constant current control circuit I-1 and the constant current control circuit I-2, and controls the MOSFET power tube T1 (201) and the MOSFET power tube T2 (202) respectively; each group of the constant current control circuit includes an adjustable three-terminal voltage regulator LM317 (501), an output voltage setting resistor R8 (502), a driving resistor R10 (503), an output voltage setting resistor R9 (504), an output filter capacitor C1 (505), a current limiting resistor R11 (506), a MOSFET power tube gate-source resistor R12 (507), a driving signal off transistor Q10 (508), a transistor driving resistor R13 (509), and the main function is to set the output voltage setting resistor R8 (502) and the resistor R9 (504) to the adjustable three-terminal voltage regulator LM317 (501) as a constant voltage output; the output filter capacitor C1 (505) filters the output voltage to make it more stable; then the driving resistor R10 (503) is connected to the MOSFET power tube T1 (201), according to the transfer characteristic curve of the MOSFET power tube T1 (201), a constant voltage is loaded between the gate and the source of the MOSFET power tube to drive, then the MOSFET power tube will output a constant current, so as to realize the constant current output of the MOSFET power tube T1 (201); if the current output of the road is not needed, the constant current control signal I / OOUT1 is set to high level, then the driving signal off transistor Q10 (508) is turned on, then the driving voltage between the gate and the source of the MOSFET power tube T1 (201) is lower than the threshold opening voltage, then the output current is 0;

[0026] The power MOSFET-I (106) and the power MOSFET-II (115) have the same structure, which is composed of MOSFET power tube T1 (201) and MOSFET power tube T2 (202), and adopts FQA40N25 N-channel MOSFET of FAIRCHILD company, the maximum withstand voltage is 250V, and the maximum output current is 40A; in actual work, MOSFET power tube T1 (201) and MOSFET power tube T2 (202) can be respectively set to constant current I1 and I2 output through constant current control circuit I (105); for example, when the output driving current is 2A, MOSFET power tube T1 (201) is set to 1A output, MOSFET power tube T2 (202) is set to 0.5A, and the remaining 0.5A is output by power amplifier OPA548-I (109) through current closed-loop PID adjustment to realize high-precision output, that is, 0-2A continuous output is realized by parallel connection of multiple power MOSFETs and power amplifiers; according to the actual output current control precision requirement, the number of MOSFET power tubes can be further increased, so that the output current of each power MOSFET can be further subdivided.

[0027] The "FAIRCHILD company" refers to Fairchild Semiconductor of the United States;

[0028] The X-direction commutation circuit and deflection coil (110) and the Y-direction commutation circuit and deflection coil (119) have the same structure, wherein the X-direction commutation circuit and deflection coil (110) includes power switch tube Q1 (203), power switch tube Q3 (204), X-direction deflection coil (205), power switch tube Q2 (206), and power switch tube Q4 (207). Their positional relationship is that power switch tube Q1 (203), power switch tube Q3 (204), power switch tube Q2 (206), and power switch tube Q4 (207) are connected to form a full-bridge circuit, and the X-direction deflection coil (205) is connected to the midpoint of the full-bridge circuit.

[0029] The power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) in the commutation circuit are all controlled by the same isolation drive circuit, including an opto-isolation drive circuit FOD3182 (601), an input current limiting resistor R17 (602), an input current drive transistor Q12 (603), a transistor drive resistor R18 (604), and power switch drive resistors R19 (605) and R20 (606). When the commutation control signal (PWM11 is high and PWM12 is low) controls power switches Q1 (203) and Q4 (207) to turn on and controls power switches Q3 (204) and Q2 (206) to turn off, the drive current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正 When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 ;

[0030] The "FOD3182" mentioned refers to a model number of a logic output optocoupler isolation integrated circuit chip manufactured by ON Semiconductor Corporation of the United States.

[0031] The deflection coils are self-developed coils, including an X-direction deflection coil (205) and a Y-direction deflection coil. These are two coils with the same structure, wound together on a circular coil frame. Their main function is to generate a deflection magnetic field in the X direction when a driving current flows through the X-direction deflection coil, causing the electron beam to deflect along the X-axis; and to generate a deflection magnetic field in the Y direction when a driving current flows through the Y-direction deflection coil, causing the electron beam to deflect along the Y-axis.

[0032] The X-direction output current sensor (111) and Y-direction output current sensor (120) are LEM LA25-NP Hall current sensors, which are used to collect the current signal flowing through the deflection scanning coil and transmit it to the PID control circuit to adjust the drive current in the deflection scanning coil.

[0033] The "LEM company" mentioned refers to a model of a closed-loop current Hall sensor integrated circuit used to achieve isolated current sampling;

[0034] The "LA25-NP" mentioned above refers to the model number of a closed-loop current Hall sensor integrated circuit used to achieve isolated current sampling.

[0035] The “+VCC1” (112) and “+VCC2” (121) mentioned above refer to power supplies with positive output voltage.

[0036] 3. Advantages and effects:

[0037] 1) By adopting a parallel output structure of multiple power MOSFETs and power amplifiers, the total power consumption of the high voltage and high current drive circuit is distributed to each power MOSFET and power amplifier, which solves the problem that excessive power dissipation of a single power amplifier can easily lead to thermal failure of the device, and improves the working reliability of the high voltage and high current high speed drive circuit.

[0038] 2) By adopting a parallel output structure of multiple power MOSFETs and power amplifiers, the power consumption of a single power device is reduced. Therefore, the voltage of the power supply for the drive circuit can be further increased, which in turn increases the rate of change of the drive current, thereby achieving a higher electron beam deflection scanning speed.

[0039] 3) By adopting a parallel output structure of multiple power MOSFETs and power amplifier, the output current of the power amplifier is greatly reduced, which in turn reduces the current value of the current closed-loop PID regulation of the drive circuit. This helps to reduce current overshoot and oscillation, and can improve the accuracy and response speed of current control.

[0040] 4) The output current of the power amplifier is reduced, which means there are more models, manufacturers and channels of high voltage and low current power amplifiers to choose from, and the cost of components is lower, which helps to reduce the cost of the drive circuit and shorten the development cycle.

[0041] 5) The electron beam high-speed deflection scanning drive circuit and deflection coil described above have a scientific structure and reliable operation, realizing high-speed, high-precision, and large-range deflection scanning of the electron beam. The maximum scanning area can reach 410mm×410mm, the resolution can reach 0.1mm, and the scanning frequency between points (1mm spacing) can reach 200kHz. Attached Figure Description

[0042] Figure 1 This is a system configuration diagram of the electron beam high-speed deflection scanning drive circuit of the present invention.

[0043] Figure 2 This is a block diagram illustrating the working principle of the main circuit of the high-speed deflection scanning drive circuit in this invention.

[0044] Figure 3 This is a schematic diagram of the MOSFET transfer operation characteristic curve in this invention.

[0045] Figure 4 This is a schematic diagram illustrating the working principle of the signal isolation circuit in this invention.

[0046] Figure 5This is a schematic diagram of the working principle of the constant current control circuit in this invention.

[0047] Figure 6 This is a schematic diagram of the working principle of the commutation control circuit in this invention.

[0048] The symbols and codes in the diagram are explained as follows:

[0049] 101 is an industrial control computer;

[0050] 102 is a serial communication circuit;

[0051] 103 is the DSP control circuit;

[0052] 104 is signal isolation circuit I;

[0053] 105 is the constant current control circuit I;

[0054] 106 is a power MOSFET I;

[0055] 107 is a high-speed, high-precision D / A circuit I;

[0056] 108 is a PID control circuit I;

[0057] 109 is a power amplifier-I;

[0058] 110 is the X-direction commutation circuit and deflection coil;

[0059] 111 is an X-direction output current sensor;

[0060] 112 is a high-voltage power supply;

[0061] 113 is signal isolation circuit II;

[0062] 114 is the constant current control circuit II;

[0063] 115 is a power MOSFET II;

[0064] 116 is a high-speed, high-precision D / A circuit II;

[0065] 117 is the PID control circuit II;

[0066] 118 is a power amplifier-II;

[0067] 119 is the Y-direction commutation circuit and deflection coil;

[0068] 120 is a current sensor that outputs current in the Y direction;

[0069] 121 is a high-voltage power supply;

[0070] 201 is the power MOSFET T1;

[0071] 202 is the power MOSFET T2;

[0072] 203 is the power switch Q1 for the X-direction commutation circuit;

[0073] 204 is the power switch Q2 for the X-direction commutation circuit;

[0074] 205 is the X-direction deflection coil;

[0075] 206 is the power switch Q3 for the X-direction commutation circuit;

[0076] 207 is the power switch Q4 for the X-direction commutation circuit;

[0077] 208 is the freewheeling diode D2;

[0078] 209 is the power amplifier OPA548;

[0079] 210 is the output diode D1 of the power amplifier;

[0080] 211 is the proportional amplifier resistor R1 in the power amplifier;

[0081] 212 is the proportional amplifier resistor R2 in the power amplifier;

[0082] 213 is the proportional amplifier resistor R3 in the power amplifier;

[0083] 214 is the proportional amplifier resistor R4 in the power amplifier;

[0084] 401 is the opto-isolation circuit 6N137;

[0085] 402 is the input current limiting resistor R5;

[0086] 403 is the output pull-up resistor R6;

[0087] 404 is the pull-up resistor R7 for the transistor;

[0088] 405 is the output transistor Q9;

[0089] 501 is an adjustable three-stage voltage regulator LM317;

[0090] 502 is the resistor R8 for setting the output voltage;

[0091] 503 is the driving resistor R10;

[0092] 504 is the output voltage setting resistor R9;

[0093] 505 is the output filter capacitor C1;

[0094] 506 is the current-limiting resistor R11;

[0095] 507 is the gate-source resistor R12 for the power MOSFET;

[0096] 508 is used to turn off transistor Q10 for drive signals;

[0097] 509 is the transistor drive resistor R13;

[0098] 601 is the opto-isolated driver circuit FOD3182;

[0099] 602 is the input current-limiting resistor R17;

[0100] 603 is the input current drive transistor Q12;

[0101] 604 is the transistor drive resistor R18;

[0102] 605 is the drive resistor R19 for the power switch transistor;

[0103] 606 is the driving resistor R20 for the power switch transistor. Detailed Implementation

[0104] This invention provides a high-speed electron beam deflection scanning drive circuit, the specific implementation of which is as follows:

[0105] The electron beam high-speed deflection scanning drive circuit includes:

[0106] See Figure 1As shown, the system includes an industrial computer (101), a serial communication circuit (102), a DSP control circuit (103), an opto-signal isolation circuit I (104), an opto-signal isolation circuit II (113), a constant current control circuit I (105), a constant current control circuit II (114), a power MOSFET-I (106), a power MOSFET-II (115), a high-speed high-precision DA conversion circuit I (107), a high-speed high-precision DA conversion circuit II (116), a PID adjustment circuit I (108), a PID adjustment circuit II (117), a power amplifier OPA548-I (109), a power amplifier OPA548-II (118), an X-direction output current sensor (111), a Y-direction output current sensor (120), and an X-direction commutation circuit. The circuit includes a deflection coil (110), a Y-direction commutation circuit and a deflection coil (119), a power supply +VCC1 (112), and a power supply +VCC2 (121). The connection between them is as follows: the industrial computer (101) is connected to the DSP control circuit (103) through a serial communication circuit (102) to realize the transmission of deflection scanning data; the DSP control circuit (103) processes the received digital signal and converts it into an SPI signal and an I / O signal; among them, the SPI signal 1 is transmitted to the high-speed high-precision DA conversion circuit (107) after passing through the opto-signal isolation circuit I (104) to be converted into an analog voltage signal output, and the signal is transmitted to the PID adjustment circuit I (109) as the input given I of the scanning current waveform of the X-direction deflection coil (205). Xg The output U of the PID control circuit I (108) Xg The signal is connected to the non-inverting input of the power amplifier OPA548-Ⅰ (109), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅰ (106). Simultaneously, I / O signal 1 is transmitted to the constant current control circuit Ⅰ (105) via the opto-signal isolation circuit Ⅰ (104) to control the power MOSFET-Ⅰ (106) to output a constant current. The output current of the power MOSFET-Ⅰ (106) is connected in parallel with the output current of the power amplifier OPA548-Ⅰ (109), and then connected to the X-direction commutation circuit and deflection coil (110) via the X-direction output current sensor (111) to achieve high-speed current drive of the X-direction deflection coil (205). Similarly, SPI signal 2 is transmitted to the high-speed, high-precision DA conversion circuit Ⅱ (116) via the opto-signal isolation circuit Ⅱ (113) to be converted into an analog voltage signal output. This signal is transmitted to the PID adjustment circuit Ⅱ (117) as the input given I for the scanning current waveform of the Y-direction deflection coil. Yg The output U of the PID control circuit II (117) YgThe signal is connected to the non-inverting input of the power amplifier OPA548-Ⅱ (118), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅱ (115). At the same time, the I / O signal 2 is transmitted to the constant current control circuit Ⅱ (114) after passing through the opto-signal isolation circuit Ⅱ (113), which controls the power MOSFET-Ⅱ (115) to output a constant current. The output current of the power MOSFET-Ⅱ (115) is connected in parallel with the output current of the power amplifier OPA548-Ⅱ (118), and then connected to the Y-direction commutation circuit and deflection coil (119) through the Y-direction output current sensor (120) to realize the high-speed current drive of the Y-direction deflection coil.

[0107] See Figure 2 As shown, the power MOSFET-Ⅰ (106) consists of MOSFET power transistors T1 (201) and T2 (202), each outputting constant currents I1 and I2; the power amplifier OPA548-Ⅰ (109) consists of an integrated power amplifier OPA548 (209), an output diode D1 (210), and proportional amplifier resistors R1 (211), R2 (212), R3 (213), and R4 (214). The PID control circuit Ⅰ (108) outputs U... Xg The voltage and drive current are amplified by connecting the proportional amplifier resistor R1 (211) to the non-inverting input of the OPA548. Then, the output of the OPA548 is connected in parallel with the output of MOSFET power transistors T1 (201) and T2 (202) through the output diode D1 (210). The total output current I X =I1+I2+I3, output current I X The current is transmitted to the X-direction commutation circuit and deflection coil (110) via the current sensor (111); the current sensor (111) detects the total output current I. X and the current feedback signal I XfThe high-precision current output is achieved by connecting to the PID control circuit I (108) for closed-loop regulation; the X-direction commutation circuit and deflection coil (110) include power switch Q1 (203), power switch Q3 (204), X-direction deflection coil (205), power switch Q2 (206), and power switch Q4 (207). Their positional relationship is as follows: power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) are connected to form a full-bridge circuit, and the X-direction deflection coil (205) is connected at the midpoint of the full-bridge circuit; when the commutation control signal (PWM11 is high level, PWM12 is low level) controls power switches Q1 (203) and Q4 (207) to conduct and controls power switches Q3 (204) and Q2 (206) to turn off, the drive current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正 When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 .

[0108] See Figure 3 The diagram shows the transfer characteristic curves of the MOSFET power transistors used in the power MOSFET-Ⅰ (106) and power MOSFET-Ⅱ (115) circuits described in this invention. Both MOSFET power transistors T1 (201) and T2 (202) are N-channel MOSFETs FQA40N25. The threshold voltage of the FQA40N25 power transistor is approximately +4.5V, and the gate drive voltage U GS When the voltage varies from +4.5V to +5.5V, the drain output current I of the MOSFET power transistor... D A varies approximately linearly from 0 to 2.0A, and V GS with I D There is a one-to-one correspondence; therefore, by controlling the gate drive voltages of MOSFET power transistors T1 (201) and T2 (202), their output current can be adjusted. If the gate drive voltage V GS If a constant voltage between +4.5V and +5.5V is set, the output current will be constant.

[0109] See Figure 4As shown, opto-signal isolation circuit I (104) and opto-signal isolation circuit II (113) have the same structure. They are composed of three sets of SPI communication isolation circuits and two sets of constant current control isolation circuits with the same structure, which together realize the opto-isolation of SPI serial communication and constant current control I / O signals. Each set of opto-isolation circuits includes opto-isolation integrated circuit 6N137 (401), input current limiting resistor R5 (402), output pull-up resistor R6 (403), transistor pull-up resistor R7 (404), and output transistor Q9 (405). Its function is to isolate the digital signals of SPI serial communication and constant current control I / O through opto-coupling, realize the isolated transmission of SPI communication signals, and realize the constant current drive of high-voltage MOSFET power transistors T1 and T2.

[0110] See Figure 5 As shown, constant current control circuit I (105) and constant current control circuit II (114) have the same structure, consisting of two identical constant current control circuits I-1 and I-2, which control MOSFET power transistors T1 (201) and T2 (202) respectively. Each constant current control circuit includes an adjustable three-terminal voltage regulator LM317 (501), output voltage setting resistors R8 (502) and R9 (504), drive resistor R10 (503), output filter capacitor C1 (505), current limiting resistor R11 (506), MOSFET power transistor gate-source resistor R12 (507), drive signal turn-off transistor Q10 (508), and transistor drive resistor R13 (509). Its main function is to adjust the voltage of the adjustable three-terminal voltage regulator LM317 by setting the resistance values ​​of output voltage setting resistors R8 (502) and R9 (504). The output of the LM317 (501) voltage regulator is set to a constant voltage output; the output filter capacitor C1 (505) filters the output voltage to make it more stable; then it is connected to the MOSFET power transistor T1 (201) through the drive resistor R10 (503). According to the transfer characteristic curve of the MOSFET power transistor T1 (201), when a constant voltage is applied between the gate and source of the MOSFET power transistor for driving, the MOSFET power transistor will output a constant current, thereby realizing the constant current output of the MOSFET power transistor T1 (201); if the current output is not needed, the constant current control signal I / OOUT1 is set to a high level, then the drive signal turn-off transistor Q10 (508) is turned on, and the drive voltage between the gate and source of the MOSFET power transistor T1 (201) is lower than the threshold turn-on voltage, so its output current is 0.

[0111] See Figure 6As shown, the X-direction commutation circuit and deflection coil (110) and the Y-direction commutation circuit and deflection coil (119) have the same structure. The X-direction commutation circuit and deflection coil (110) includes power switch Q1 (203), power switch Q3 (204), X-direction deflection coil (205), power switch Q2 (206), and power switch Q4 (207). Their positional relationship is as follows: power switch Q1 (203), power switch Q3 (204), power switch Q2 (206), and power switch Q4 (207) are connected to form a full-bridge circuit, and the X-direction deflection coil (205) is connected at the midpoint of the full-bridge circuit. The power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) of the commutation circuit are all controlled by the same isolation drive circuit, including the opto-isolation drive circuit FOD3182 (601) and the input limit. The current driving resistors are R17 (602), Q12 (603), R18 (604), R19 (605), and R20 (606). When the commutation control signal (PWM11 is high and PWM12 is low) controls the power switches Q1 (203) and Q4 (207) to turn on and control the switches Q3 (204) and Q2 (206) to turn off, the driving current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正 When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 ;

[0112] The high-speed electron beam deflection scanning drive circuit described above can achieve high-precision, wide-range, and high-speed deflection scanning of the electron beam.

[0113] The scanning area of ​​the high-speed deflection scanning drive circuit of the electron beam can reach up to 410mm×410mm;

[0114] The deflection scanning resolution of the high-speed electron beam deflection scanning drive circuit can reach 0.1 mm;

[0115] The point-to-point (1mm spacing) scanning frequency of the electron beam high-speed deflection scanning drive circuit reaches 200kHz.

[0116] This invention addresses the need for high-precision, wide-range, and high-speed deflection scanning in electron beam selective melting additive manufacturing technology by providing a high-speed electron beam deflection scanning drive circuit. By employing a parallel output structure of multiple power MOSFETs and power amplifiers, the total power consumption of the high-voltage, high-current drive circuit is distributed among the individual power MOSFETs and power amplifiers. This solves the problem of excessive power dissipation in a single power amplifier leading to thermal failure, thus improving the reliability of the high-voltage, high-current, high-speed drive circuit. Reducing the power consumption of individual power devices allows for a further increase in the voltage of the drive circuit's power supply, further increasing the rate of change of the drive current and achieving a higher electron beam deflection scanning speed. The reduced output current of the power amplifier further reduces the current value of the drive circuit's closed-loop PID control, which helps reduce current overshoot and oscillation, improving the accuracy and response speed of current control. The reduced output current of the power amplifier allows for a wider selection of high-voltage, low-current power amplifier models, manufacturers, and channels, with lower component costs, thus reducing drive circuit costs and shortening the development cycle. The provided high-speed electron beam deflection scanning drive circuit can achieve high-speed, high-precision, and large-range electron beam deflection scanning, with a maximum scanning area of ​​410mm × 410mm, a resolution of 0.1mm, and a point-to-point (1mm spacing) scanning frequency of up to 200kHz.

[0117] The present invention includes an industrial computer (101), a serial communication circuit (102), a DSP control circuit (103), an opto-signal isolation circuit I (104), an opto-signal isolation circuit II (113), a constant current control circuit I (105), a constant current control circuit II (114), a power MOSFET-I (106), a power MOSFET-II (115), a high-speed high-precision DA conversion circuit I (107), a high-speed high-precision DA conversion circuit II (116), a PID adjustment circuit I (108), a PID adjustment circuit II (117), a power amplifier OPA548-I (109), a power amplifier OPA548-II (118), an X-direction output current sensor (111), a Y-direction output current sensor (120), an X-direction commutation circuit and deflection coil (110), a Y-direction commutation circuit and deflection coil (119), a power supply +VCC1 (112), and a power supply +VCC2 (121).

[0118] After receiving the part slice and path planning data, the industrial control computer (101) parses the data to obtain the data packet that the lower-level DSP control circuit (103) can recognize. Then, it transmits the data to the DSP control circuit (103) through the serial communication circuit (102). The DSP control circuit (103) processes the received data and converts it into SPI signals and I / O signals. The SPI signals are used to transmit the output current setpoint data, including SPI signal 1 and SPI signal 2, which control the X-direction deflection coil and the Y-direction deflection coil, respectively. The I / O signals are used to transmit the power MOSFET constant current control signal and commutation control signal, including I / O signal 1 and SPI signal 2, PWM11, PWM12, PWM21, and PWM22. SPI signal 1 is transmitted to the high-speed high-precision DA conversion circuit (107) through the opto-signal isolation circuit (104) and converted into an analog voltage signal output. This signal is transmitted to the PID adjustment circuit (109) as the scanning current waveform input setpoint I of the X-direction deflection coil (205). Xg The output U of the PID control circuit I (108) Xg The signal is connected to the non-inverting input of the power amplifier OPA548-Ⅰ (109), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅰ (106). At the same time, the I / O signal 1 is transmitted to the constant current control circuit Ⅰ (105) through the opto-signal isolation circuit Ⅰ (104) to control the power MOSFET-Ⅰ (106) to output a constant current. The output current of the power MOSFET-Ⅰ (106) is connected in parallel with the output current of the power amplifier OPA548-Ⅰ (109), and then connected to the X-direction commutation circuit and deflection coil (110) through the X-direction output current sensor (111) to realize the high-speed current drive of the X-direction deflection coil (205). The commutation control signals PWM11 and PWM12 are connected to the X-direction commutation circuit and deflection coil (110) to control the power switch to turn on and off, and realize the forward and directional flow control of the deflection coil current. Similarly, SPI signal 2 is transmitted through opto-signal isolation circuit II (113) to high-speed, high-precision DA conversion circuit II (116) and converted into an analog voltage signal output. This signal is then transmitted to PID control circuit II (117) as the input given I for the scanning current waveform of the Y-direction deflection coil. Yg The output U of the PID control circuit II (117) YgThe signal is connected to the non-inverting input of the power amplifier OPA548-Ⅱ (118), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅱ (115). At the same time, the I / O signal 2 is transmitted to the constant current control circuit Ⅱ (114) through the opto-signal isolation circuit Ⅱ (113) to control the power MOSFET-Ⅱ (115) to output a constant current. The output current of the power MOSFET-Ⅱ (115) is connected in parallel with the output current of the power amplifier OPA548-Ⅱ (118), and then connected to the Y-direction commutation circuit and deflection coil (119) through the Y-direction output current sensor (120) to realize the high-speed current drive of the Y-direction deflection coil. The commutation control signals PWM21 and PWM22 are connected to the Y-direction commutation circuit and deflection coil (119) to control the power switch to turn on and off, and realize the forward and reverse flow control of the deflection coil current.

[0119] The industrial computer (101) is an Advantech IPC-610L industrial computer.

[0120] The serial communication circuit (102) uses the 485 serial bus (i.e. RS-485) interface on the industrial control computer to transmit the deflection scanning data of the industrial control computer to the DSP control circuit through this serial interface.

[0121] The DSP control circuit (103) uses the STM32G474VET6 chip from ARM as the main control circuit. Its main function is to receive the deflection scanning data transmitted by the industrial control computer, process the data, convert it into the corresponding deflection scanning coil drive current setpoint and I / O control signal, and then transmit it to the high-speed high-precision DA conversion circuit, constant current control circuit and commutation control circuit through the SPI communication interface and I / O interface respectively.

[0122] The opto-signal isolation circuit I (104) and opto-signal isolation circuit II (113) consist of three sets of SPI communication isolation circuits and two sets of constant current control isolation circuits with the same structure, which together realize the opto-isolation of SPI serial communication and constant current control I / O signals. Each opto-isolation circuit includes opto-isolation integrated circuit 6N137 (401), input current limiting resistor R5 (402), output pull-up resistor R6 (403), transistor pull-up resistor R7 (404), and output transistor Q9 (405). Its function is to isolate the digital signals of SPI serial communication and constant current control I / O through opto-coupling, realize the isolated transmission of SPI communication signals, and realize the constant current drive of high-voltage MOSFET power transistors T1 and T2.

[0123] The high-speed, high-precision DA conversion circuit I (107) and the high-speed, high-precision DA conversion circuit II (116) both use the DAC8560 conversion circuit. The DAC8560 is a low-power, voltage-output, single-channel, 16-bit, 3-wire SPI serial DA conversion circuit with a serial communication rate of 30MHz. It can quickly set the DA output voltage. Its main function is to convert the SPI serial communication signal transmitted from the opto-signal isolation circuit I (104) and the opto-signal isolation circuit II (113) into an analog voltage signal I. Xg and I Yg Output.

[0124] PID control circuit I (108) and PID control circuit II (117) are used to adjust the drive current on the deflection coils in the X and Y directions, and their output U Xg and U Yg Connected to power amplifiers OPA548-Ⅰ(109) and OPA548-Ⅱ(118), it is amplified again as the input of the power amplifier.

[0125] The power amplifier OPA548-Ⅰ(109) (power amplifier OPA548-Ⅱ(118)) includes an integrated power amplifier OPA548(209), an output diode D1(210), and proportional amplifier resistors R1(211), R2(212), R3(213), and R4(214). Its main function is to form a power amplifier circuit to convert the input U Xg and U Yg The voltage and drive current are amplified again, and the output is then connected in parallel with the output current of MOSFET power transistors T1 (201) and T2 (202). The total output current Io is thus calculated. X =I1+I2+I3;

[0126] The constant current control circuit I (105) and constant current control circuit II (114) consist of two identical constant current control circuits I-1 and I-2, which control MOSFET power transistors T1 (201) and T2 (202) respectively. Each constant current control circuit includes an adjustable three-terminal voltage regulator LM317 (501), an output voltage setting resistor R8 (502), a drive resistor R10 (503), an output voltage setting resistor R9 (504), an output filter capacitor C1 (505), a current limiting resistor R11 (506), a MOSFET power transistor gate-source resistor R12 (507), a drive signal turn-off transistor Q10 (508), and a transistor drive resistor R13 (509). By setting the resistance values ​​of the output voltage setting resistors R8 (502) and R9 (504), the adjustable three-terminal voltage regulator is... The output of the voltage source LM317 (501) is set to a constant voltage output; the output filter capacitor C1 (505) filters the output voltage to make it more stable; then it is connected to the MOSFET power transistor T1 (201) through the drive resistor R10 (503). According to the transfer characteristic curve of the MOSFET power transistor T1 (201), when a constant voltage is applied between the gate and source of the MOSFET power transistor for driving, the MOSFET power transistor will output a constant current, thereby realizing the constant current output of the MOSFET power transistor T1 (201); if this current output is not needed, the constant current control signal I / OOUT1 is set to a high level, then the drive signal turn-off transistor Q10 (508) is turned on, and the drive voltage between the gate and source of the MOSFET power transistor T1 (201) is lower than the threshold turn-on voltage, so its output current is 0.

[0127] The power MOSFET-Ⅰ (106) and power MOSFET-Ⅱ (115) are composed of MOSFET power transistor T1 (201) and MOSFET power transistor T2 (202). They adopt FAIRCHILD's FQA40N25 N-channel MOSFET with a maximum withstand voltage of 250V and a maximum output current of 40A. The constant current control circuit Ⅰ (105) can set the MOSFET power transistor T1 (201) and MOSFET power transistor T2 (202) to constant current I1 and I2 respectively. For example, when outputting a 2A drive current, the MOSFET power transistor T1 (201) can be set to 1A output and the MOSFET power transistor T2 (202) can be set to 0.5A. The remaining 0.5A is achieved by the power amplifier OPA548-Ⅰ (109) through current closed-loop PID regulation to achieve high-precision output. That is, the 0-2A continuous output is achieved by connecting multiple power MOSFETs in parallel with the power amplifier output.

[0128] The X-direction commutation circuit and deflection coil (110) (Y-direction commutation circuit and deflection coil (119)) include power switches Q1 (203), Q3 (204), X-direction deflection coil (205), Q2 (206), and Q4 (207). Power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) are connected to form a full-bridge circuit, and the X-direction deflection coil (205) is connected at the midpoint of the full-bridge circuit. The power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) in the commutation circuit are all controlled by the same isolation drive circuit, including an opto-isolation drive circuit FOD3182 (601) and an input current-limiting resistor. R17 (602), input current driving transistor Q12 (603), transistor driving resistor R18 (604), power switch driving resistors R19 (605) and R20 (606); when the commutation control signal (PWM11 is high level, PWM12 is low level) controls power switch Q1 (203) and power switch Q4 (207) to turn on, and controls power switch Q3 (204) and power switch Q2 (206) to turn off, the driving current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正 When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 .

[0129] The deflection coils are self-developed coils, including an X-direction deflection coil (205) and a Y-direction deflection coil. These are two coils with the same structure, wound together on a circular coil frame. Their main function is to generate a deflection magnetic field in the X direction when a driving current flows through the X-direction deflection coil, causing the electron beam to deflect along the X-axis; and to generate a deflection magnetic field in the Y direction when a driving current flows through the Y-direction deflection coil, causing the electron beam to deflect along the Y-axis.

[0130] The X-direction output current sensor (111) and the Y-direction output current sensor (120) are LEM LA25-NP Hall current sensors, which are used to collect the current signal flowing through the deflection coil and transmit it to the PID control circuit to adjust the drive current in the deflection scanning coil.

[0131] +VCC1” (112) and +VCC2” (121) refer to a power supply with a positive output voltage.

[0132] The invention will now be further described with reference to the accompanying drawings.

[0133] Figure 1 This is a system configuration diagram of the high-speed deflection scanning drive circuit for the electron beam, including an industrial computer (101), a serial communication circuit (102), a DSP control circuit (103), an optoelectronic signal isolation circuit I (104), an optoelectronic signal isolation circuit II (113), a constant current control circuit I (105), a constant current control circuit II (114), a power MOSFET-I (106), a power MOSFET-II (115), a high-speed high-precision DA conversion circuit I (107), a high-speed high-precision DA conversion circuit II (116), a PID adjustment circuit I (108), a PID adjustment circuit II (117), a power amplifier OPA548-I (109), a power amplifier OPA548-II (118), an X-direction output current sensor (111), a Y-direction output current sensor (120), an X-direction commutation circuit and deflection coil (110), a Y-direction commutation circuit and deflection coil (119), a power supply +VCC1 (112), and a power supply +VCC2 (121).

[0134] refer to Figure 1 The industrial computer (101) is connected to the DSP control circuit (103) via a serial communication circuit (102) to realize the transmission of deflection scanning data; the DSP control circuit (103) processes the received digital signal and converts it into an SPI signal and an I / O signal; among them, the SPI signal 1 is transmitted to the high-speed high-precision DA conversion circuit (107) after passing through the opto-signal isolation circuit I (104) to be converted into an analog voltage signal output, and this signal is transmitted to the PID adjustment circuit I (109) as the input given I of the scanning current waveform of the X-direction deflection coil (205). Xg The output U of the PID control circuit I (108) XgThe signal is connected to the non-inverting input of the power amplifier OPA548-Ⅰ (109), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅰ (106). Simultaneously, I / O signal 1 is transmitted to the constant current control circuit Ⅰ (105) via the opto-signal isolation circuit Ⅰ (104) to control the power MOSFET-Ⅰ (106) to output a constant current. The output current of the power MOSFET-Ⅰ (106) is connected in parallel with the output current of the power amplifier OPA548-Ⅰ (109), and then connected to the X-direction commutation circuit and deflection coil (110) via the X-direction output current sensor (111) to achieve high-speed current drive of the X-direction deflection coil (205). Similarly, SPI signal 2 is transmitted to the high-speed, high-precision DA conversion circuit Ⅱ (116) via the opto-signal isolation circuit Ⅱ (113) to be converted into an analog voltage signal output. This signal is transmitted to the PID adjustment circuit Ⅱ (117) as the input given I for the scanning current waveform of the Y-direction deflection coil. Yg The output U of the PID control circuit II (117) Yg The signal is connected to the non-inverting input of the power amplifier OPA548-Ⅱ (118), amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅱ (115). At the same time, the I / O signal 2 is transmitted to the constant current control circuit Ⅱ (114) after passing through the opto-signal isolation circuit Ⅱ (113), which controls the power MOSFET-Ⅱ (115) to output a constant current. The output current of the power MOSFET-Ⅱ (115) is connected in parallel with the output current of the power amplifier OPA548-Ⅱ (118), and then connected to the Y-direction commutation circuit and deflection coil (119) through the Y-direction output current sensor (120) to realize the high-speed current drive of the Y-direction deflection coil.

[0135] Figure 2 This is a block diagram of the main circuit working principle of the high-speed deflection scanning drive circuit. The power MOSFET-Ⅰ (106) is composed of MOSFET power transistor T1 (201) and MOSFET power transistor T2 (202); the power amplifier OPA548-Ⅰ (109) is composed of integrated power amplifier OPA548 (209), output diode D1 (210), proportional amplifier resistors R1 (211), R2 (212), R3 (213) and R4 (214); the X-direction commutation circuit and deflection coil (110) includes power switch transistor Q1 (203), power switch transistor Q3 (204), X-direction deflection coil (205), power switch transistor Q2 (206), and power switch transistor Q4 (207).

[0136] refer to Figure 2The power MOSFET-Ⅰ (106) consists of MOSFET power transistors T1 (201) and T2 (202), each outputting constant currents I1 and I2; the PID regulation circuit Ⅰ (108) outputs U Xg The voltage and drive current are amplified by connecting the proportional amplifier resistor R1 (211) to the non-inverting input of the OPA548 (209). Then, the output of the OPA548 (209) is connected in parallel with the outputs of MOSFET power transistors T1 (201) and T2 (202) through the output diode D1 (210). The total output current I X =I1+I2+I3, output current I X The current is transmitted to the X-direction commutation circuit and deflection coil (110) via the current sensor (111); the current sensor (111) detects the total output current I. X and the current feedback signal I Xf A high-precision current output is achieved by connecting to the PID control circuit I (108) for closed-loop regulation; power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) are connected to form a full-bridge circuit, and the X-direction deflection coil (205) is connected at the midpoint of the full-bridge circuit; when the commutation control signal (PWM11 is high level, PWM12 is low level) controls power switches Q1 (203) and Q4 (207) to conduct and controls power switches Q3 (204) and Q2 (206) to turn off, the drive current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正 When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 .

[0137] Figure 3 This is a schematic diagram of the MOSFET's switching operating characteristic curve.

[0138] refer to Figure 3 Both MOSFET power transistors T1 (201) and T2 (202) are N-channel MOSFETs FQA40N25; the threshold voltage of the FQA40N25 power transistor is approximately +4.5V, and the gate drive voltage U GS When the voltage varies from +4.5V to +5.5V, the drain output current I of the MOSFET power transistor... D A varies approximately linearly from 0 to 2.0A, and VGS with I D There is a one-to-one correspondence; therefore, by controlling the gate drive voltages of MOSFET power transistors T1 (201) and T2 (202), their output current can be adjusted. If the gate drive voltage V GS If a constant voltage between +4.5V and +5.5V is set, the output current will be constant.

[0139] Figure 4 This is a schematic diagram of the signal isolation circuit. It consists of three sets of SPI communication isolation circuits and two sets of constant current control isolation circuits with the same structure, which together realize the opto-isolation of SPI serial communication and constant current control I / O signals. Each opto-isolation circuit includes opto-isolation integrated circuit 6N137 (401), input current limiting resistor R5 (402), output pull-up resistor R6 (403), transistor pull-up resistor R7 (404), and output transistor Q9 (405).

[0140] refer to Figure 4 The digital signals of SPI serial communication and constant current control I / O are isolated by opto-isolation integrated circuit 6N137 (401) to realize the isolated transmission of SPI communication signals and the constant current drive of high-voltage MOSFET power transistors T1 and T2.

[0141] Figure 5 This is a schematic diagram of the constant current control circuit, which consists of two identical constant current control circuits I-1 and I-2, which control MOSFET power transistors T1 (201) and T2 (202) respectively. Each constant current control circuit includes an adjustable three-terminal voltage regulator LM317 (501), output voltage setting resistors R8 (502) and R9 (504), drive resistor R10 (503), output filter capacitor C1 (505), current limiting resistor R11 (506), MOSFET power transistor gate-source resistor R12 (507), drive signal turn-off transistor Q10 (508), and transistor drive resistor R13 (509).

[0142] refer to Figure 5By setting the output voltage of resistors R8 (502) and R9 (504), the output of the adjustable three-terminal voltage regulator LM317 (501) is set to a constant voltage output. The output filter capacitor C1 (505) filters the output voltage to make it more stable. Then, the drive resistor R10 (503) is connected to the MOSFET power transistor T1 (201). According to the transfer characteristic curve of the MOSFET power transistor T1 (201), when a constant voltage is applied between the gate and source terminals of the MOSFET power transistor for driving, the MOSFET power transistor will output a constant current, thereby realizing the constant current output of the MOSFET power transistor T1 (201). If this current output is not needed, the constant current control signal I / OOUT1 is set to a high level, and the drive signal turn-off transistor Q10 (508) is turned on. Then, the drive voltage between the gate and source terminals of the MOSFET power transistor T1 (201) is lower than the threshold turn-on voltage, and its output current is 0.

[0143] Figure 6 This is a schematic diagram of the commutation control circuit. The power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) in the commutation circuit are all controlled by the same isolation drive circuit, which includes the opto-isolation drive circuit FOD3182 (601), the input current limiting resistor R17 (602), the input current drive transistor Q12 (603), the transistor drive resistor R18 (604), and the power switch drive resistors R19 (605) and R20 (606).

[0144] refer to Figure 6 Power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) are connected to form a full-bridge circuit. The X-direction deflection coil (205) is connected at the midpoint of the full-bridge circuit. The power switches Q1 (203), Q3 (204), Q2 (206), and Q4 (207) in the commutation circuit are all driven and controlled by the same opto-logic isolation driver circuit FOD3182 and its peripheral circuit. When the commutation control signal (PWM11 is high and PWM12 is low) controls power switches Q1 (203) and Q4 (207) to turn on and controls power switches Q3 (204) and Q2 (206) to turn off, the driving current flows from left to right through the X-direction deflection coil (205), which is a positive current I. 正When the commutation control signal (PWM11 is low and PWM12 is high) controls power switches Q3 (204) and Q2 (206) to turn on and power switches Q1 (203) and Q4 (207) to turn off, the drive current flows from right to left through the X-direction deflection coil (205), which is the reverse current I. 反 .

[0145] The high-speed deflection scanning drive circuit of the electron beam described in this invention consists of an industrial control computer, a DSP control circuit, an opto-isolation circuit, a PID closed-loop regulation circuit, a power amplifier, a power MOSFET, and a deflection coil. By employing a parallel output structure of multiple power MOSFETs and power amplifiers, the total power consumption of the high-voltage, high-current drive circuit is distributed among the individual power MOSFETs and power amplifiers. This solves the problem of excessive power dissipation in a single power amplifier leading to thermal failure, thus improving the reliability of the high-voltage, high-current, high-speed drive circuit. Reducing the power consumption of individual power devices allows for a further increase in the voltage of the drive circuit's power supply, further increasing the rate of change of the drive current and achieving a higher electron beam deflection scanning speed. The reduced output current of the power amplifier further reduces the current value of the drive circuit's closed-loop PID control, which helps reduce current overshoot and oscillation, improving the accuracy and response speed of current control. The reduced output current of the power amplifier allows for a wider selection of high-voltage, low-current power amplifier models, manufacturers, and channels, with lower component costs, thus reducing drive circuit costs and shortening the development cycle. The provided high-speed electron beam deflection scanning drive circuit can achieve high-speed, high-precision, and large-range electron beam deflection scanning, with a maximum scanning area of ​​410mm × 410mm, a resolution of 0.1mm, and a point-to-point (1mm spacing) scanning frequency of up to 200kHz.

[0146] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-speed electron beam deflection scanning drive circuit, characterized in that: include: Industrial control computer, serial communication circuit, DSP control circuit, opto-signal isolation circuit I, opto-signal isolation circuit II, constant current control circuit I, constant current control circuit II, power MOSFET-I, power MOSFET-II, high-speed high-precision DA conversion circuit I, high-speed high-precision DA conversion circuit II, PID adjustment circuit I, PID adjustment circuit II, power amplifier OPA548-I, power amplifier OPA548-II, X-direction output current sensor, Y-direction output current sensor, X-direction commutation circuit and deflection coil, Y-direction commutation circuit and deflection coil, power supply +VCC1 and power supply +VCC2; The connection between them is as follows: the industrial computer is connected to the DSP control circuit via a serial communication circuit to transmit deflection scanning data; the DSP control circuit processes the received digital signal and converts it into SPI signal and I / O signal; among them, SPI signal 1 is transmitted to the high-speed, high-precision DA conversion circuit 1 after passing through the opto-signal isolation circuit Ⅰ, and is converted into an analog voltage signal output. The analog voltage signal is transmitted to the PID adjustment circuit Ⅰ as the input given I for the scanning current waveform of the X-direction deflection coil. Xg The output U of PID control circuit I Xg The signal is connected to the non-inverting input of the power amplifier OPA548-Ⅰ, amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅰ. Simultaneously, I / O signal 1 is transmitted to the constant current control circuit Ⅰ after passing through the opto-signal isolation circuit Ⅰ, controlling the power MOSFET-Ⅰ to output a constant current. The output current of the power MOSFET-Ⅰ is connected in parallel with the output current of the power amplifier OPA548-Ⅰ, and then connected to the X-direction commutation circuit and deflection coil via the X-direction output current sensor, realizing high-speed current drive of the X-direction deflection coil. Commutation control signals PWM11 and PWM12 are connected to the X-direction commutation circuit and deflection coil, controlling the power switch to turn on and off, realizing forward and reverse current flow control of the deflection coil. SPI signal 2 is transmitted to the high-speed, high-precision DA conversion circuit Ⅱ after passing through the opto-signal isolation circuit Ⅱ, converting it into an analog voltage signal output. The analog voltage signal is transmitted to the PID adjustment circuit Ⅱ, serving as the input setpoint I for the scanning current waveform of the Y-direction deflection coil. Yg The output U of PID control circuit II Yg The signal is connected to the non-inverting input of the power amplifier OPA548-Ⅱ, amplified, and then connected in parallel with the constant current output circuit of the power MOSFET-Ⅱ. At the same time, I / O signal 2 is transmitted to the constant current control circuit Ⅱ through the opto-signal isolation circuit Ⅱ to control the power MOSFET-Ⅱ to output a constant current. The output current of the power MOSFET-Ⅱ is connected in parallel with the output current of the power amplifier OPA548-Ⅱ, and then connected to the Y-direction commutation circuit and deflection coil through the Y-direction output current sensor to realize the high-speed current drive of the Y-direction deflection coil. The commutation control signals PWM21 and PWM22 are connected to the Y-direction commutation circuit and deflection coil to control the power switch to turn on and off, thereby realizing the forward and reverse flow control of the deflection coil current.

2. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The DSP control circuit receives the deflection scanning data transmitted from the industrial computer, processes the data, and converts it into the corresponding deflection scanning coil drive current setpoint and I / O control signal. Then, it transmits the data to the high-speed high-precision DA conversion circuit, constant current control circuit, and commutation control circuit through the SPI communication interface and I / O interface, respectively.

3. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The opto-signal isolation circuit I and opto-signal isolation circuit II have the same structure. They are both composed of three sets of SPI communication isolation circuits and two sets of constant current control isolation circuits with the same structure, which together realize the opto-isolation of SPI serial communication and constant current control I / O signals. Each opto-isolation circuit includes an opto-isolation integrated circuit 6N137, an input current limiting resistor R5, an output pull-up resistor R6, a transistor pull-up resistor R7, and an output transistor Q9. The digital signals of SPI serial communication and constant current control I / O are isolated by opto-coupling, realizing the isolated transmission of SPI communication signals and the constant current drive of high-voltage MOSFET power transistors T1 and T2.

4. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The high-speed, high-precision DA conversion circuit I and high-speed, high-precision DA conversion circuit II have the same structure, both using the DAC8560 conversion circuit to convert the SPI serial communication signal transmitted from the opto-signal isolation circuit I and opto-signal isolation circuit II into an analog voltage signal I. Xg and I Yg Output.

5. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The PID control circuits I and II consist of operational amplifiers, proportional amplifier resistors, integrating capacitors, and differentiating capacitors, used to adjust the drive current on the deflection coils in the X and Y directions, and output U. Xg and U Yg Connected to power amplifiers OPA548-Ⅰ and OPA548-Ⅱ, it serves as the input of the power amplifier for further amplification; the power amplifiers OPA548-Ⅰ and OPA548-Ⅱ have the same structure, including an integrated power amplifier OPA548, output diode D1, and proportional amplification resistors R1, R2, R3, and R4. The power amplifier circuit converts the input U... Xg and U Yg The voltage and drive current are amplified again, and the output is then connected in parallel with the output currents of MOSFET power transistors T1 and T2, resulting in a total output current I. X =I1+I2+I3.

6. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The constant current control circuit I and constant current control circuit II have the same structure, consisting of two identical sets of constant current control circuits I-1 and I-2, which control MOSFET power transistors T1 and T2 respectively. Each set of constant current control circuits includes an adjustable three-terminal voltage regulator LM317, an output voltage setting resistor R8, a drive resistor R10, an output voltage setting resistor R9, an output filter capacitor C1, a current limiting resistor R11, a MOSFET power transistor gate-source resistor R12, a drive signal turn-off transistor Q10, and a transistor drive resistor R13. By setting the resistance values ​​of the output voltage setting resistors R8 and R9, the output of the adjustable three-terminal voltage regulator LM317 is set to a constant voltage output. The output filter capacitor C1 filters the output voltage; then it is connected to the MOSFET power transistor T1 through the drive resistor R10. A constant voltage is applied between the gate and source of the MOSFET power transistor for driving, and the MOSFET power transistor will output a constant current, thereby realizing the constant current output of the MOSFET power transistor T1; if this current output is not needed, the constant current control signal I / OOUT1 is set to a high level, and the drive signal turns off the transistor Q10, and the drive voltage between the gate and source of the MOSFET power transistor T1 is lower than the threshold turn-on voltage, so its output current is 0.

7. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The power MOSFET-I and power MOSFET-II have the same structure, consisting of MOSFET power transistor T1 and MOSFET power transistor T2. The constant current control circuit I sets MOSFET power transistor T1 and MOSFET power transistor T2 to output constant currents I1 and I2 respectively. According to the actual output current control accuracy requirements, the number of MOSFET power transistors is further increased to subdivide the output current of each power MOSFET.

8. The electron beam high-speed deflection scanning drive circuit according to claim 1 or 5, characterized in that: The X-direction commutation circuit and deflection coil have the same structure as the Y-direction commutation circuit and deflection coil. The X-direction commutation circuit and deflection coil include power switch Q1, power switch Q3, X-direction deflection coil, power switch Q2, and power switch Q4. Their positional relationship is as follows: power switch Q1, power switch Q3, power switch Q2, and power switch Q4 are connected to form a full-bridge circuit, and the X-direction deflection coil is connected at the midpoint of the full-bridge circuit.

9. The electron beam high-speed deflection scanning drive circuit according to claim 1 or 8, characterized in that: The commutation circuit power switches Q1, Q3, Q2, and Q4 are all controlled by the same isolation drive circuit, including the opto-isolation drive circuit FOD3182, input current limiting resistor R17, input current drive transistor Q12, transistor drive resistor R18, and power switch drive resistors R19 and R20. When the commutation control signal turns on power switches Q1 and Q4 and turns off power switches Q3 and Q2, the drive current flows from left to right through the X-direction deflection coil, which is a positive current I. 正 When the commutation control signal turns on power switches Q3 and Q2 and turns off power switches Q1 and Q4, the drive current flows from right to left through the X-direction deflection coil, which is the reverse current I. 反 .

10. The electron beam high-speed deflection scanning drive circuit according to claim 1, characterized in that: The deflection coils include an X-direction deflection coil and a Y-direction deflection coil, which are two coils with the same structure, wound together on a circular coil frame. When a driving current flows through the X-direction deflection coil, a deflection magnetic field is generated in the X direction, causing the electron beam to deflect along the X-axis. When a driving current flows through the Y-direction deflection coil, a deflection magnetic field is generated in the Y direction, causing the electron beam to deflect along the Y-axis.

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