A multi-level bias power supply for precise electron beam control

Abstract

The present invention discloses a multi-stage bias power supply for precise electron beam control, wherein: a beam current feedback circuit collects electron beam current feedback values ​​and transmits them to a single-chip microcomputer control circuit; the single-chip microcomputer control circuit calculates a voltage setting value based on the electron beam current set value and the electron beam current feedback value and transmits it to a bias regulation low-voltage circuit; the bias regulation low-voltage circuit is connected to a bias regulation high-voltage circuit; the positive output end of the bias regulation high-voltage circuit is connected to the electron gun cathode filament; and the negative output end of the bias regulation high-voltage circuit is connected to the electron gun grid. The bias regulation low-voltage circuit includes a coarse bias adjustment power supply circuit, a fine bias adjustment power supply circuit, and a beam confinement power supply circuit. The present invention significantly improves the reliability of beam confinement, the dynamic response speed of electron beam current regulation, and the adjustment precision of the bias power supply and electron beam current, thereby achieving high-precision control of small and large beam current outputs.

Description

Technical Field

[0001] The present invention belongs to the technical field of electron beam processing, and in particular relates to a multi-stage bias power supply for precise control of electron beams. Background Art

[0002] Electron beam machining technology uses a high-voltage electrostatic field to accelerate electrons, generating a high-speed electron beam. When the electron beam strikes a workpiece, its kinetic energy is converted into heat, enabling heating, cutting, and welding. Electron beam welding, with its advantages of high energy density, fast welding speed, large weld depth-to-width ratio, minimal weld deformation zone, and the ability to weld refractory and dissimilar metals, plays an irreplaceable role in the aerospace industry and has also been widely used in the automotive, high-speed rail, nuclear energy, and electronics industries.

[0003] In a hot cathode triode electron gun, the magnitude of the electron beam current is controlled by adjusting the bias voltage applied to the gate. Adjusting the bias voltage causes the electron beam current to vary accordingly, with the two varying in a roughly inversely proportional relationship. In existing technology, the gate bias power supply typically uses a single inverter. Adjusting the pulse width of the power switching tube adjusts the bias supply's output voltage, thereby controlling the electron beam current. Therefore, the bias voltage's adjustment range directly impacts the accuracy of beam control. Figure 1 is the electron beam grid bias voltage U p With electron beam current I b The relationship diagram between pTH is the grid bias value at the critical beam-emission point. At the critical beam-emission point, the electron beam current I b The bias voltage is essentially zero. When the electron beam current is zero (i.e., completely confined), a very small number of electrons still escape due to the inherent characteristics of stray electrons. To completely confine these electrons, a bias voltage significantly higher than the critical beam current point is required. For example, the critical beam current point bias voltage for a certain electron gun is −600V. To completely confine electrons, the actual bias voltage when no beam current is emitted is generally no less than −1500V. The term "less than" here refers to the comparison between the absolute values ​​of the bias voltages. Therefore, a large portion of the output voltage of the gate bias power supply is used to completely confine electrons, while the remaining voltage is used to control the electron beam current. This reduces the bias voltage adjustment range for electron beam current regulation, resulting in low beam current regulation accuracy, which often fails to meet actual processing requirements. For example, when welding thin plates with a small electron beam, the existing bias voltage adjustment range is very small, making it difficult to achieve accurate and stable output of the electron beam. Fluctuations caused by imprecise bias voltage adjustment can easily cause fluctuations in the electron beam current, making it easy for thin plate welding to have defects such as incomplete welding or melt-through. In large electron beam welding, the bias voltage adjustment range is also very small, even close to 0. Imprecise bias voltage adjustment can easily lead to inaccurate and fluctuating electron beam control, causing large spatter and unstable welding quality. Summary of the Invention

[0004] Purpose of the invention: In response to the problems existing in the prior art, the present invention discloses a multi-stage bias power supply for precise control of electron beams, which realizes dynamic adjustment of the bias power supply output voltage, improves the adjustment accuracy of the electron beam current, and thus realizes high-precision control of the electron beam current.

[0005] Technical solution: To achieve the above-mentioned purpose, the present invention adopts the following technical solution:

[0006] A multi-stage bias power supply for precise electron beam control, comprising a bias regulation low-voltage circuit, a bias regulation high-voltage circuit, a beam current feedback circuit, and a single-chip microcomputer control circuit;

[0007] The output end of the beam current feedback circuit is connected to the input end of the single chip control circuit, the beam current feedback circuit collects the electron beam current feedback value, and sends the electron beam current feedback value to the single chip control circuit;

[0008] The output end of the single-chip microcomputer control circuit is connected to the input end of the bias voltage regulating low-voltage circuit. The single-chip microcomputer control circuit calculates a voltage setting value according to the electron beam current set value and the electron beam current feedback value, and sends the voltage setting value to the bias voltage regulating low-voltage circuit.

[0009] The output end of the bias regulating low voltage circuit is connected to the input end of the bias regulating high voltage circuit, the positive output end of the bias regulating high voltage circuit is connected to the cathode filament of the electron gun, and the negative output end of the bias regulating high voltage circuit is connected to the grid of the electron gun;

[0010] The bias regulation low-voltage circuit includes a coarse bias adjustment power supply circuit, a fine bias adjustment power supply circuit, and a beam containment power supply circuit. The input end of the coarse bias adjustment power supply circuit, the input end of the fine bias adjustment power supply circuit, and the input end of the beam containment power supply circuit are all connected to the output end of the single-chip microcomputer control circuit. The negative output end of the coarse bias adjustment power supply circuit is connected to the positive output end of the fine bias adjustment power supply circuit. The negative output end of the fine bias adjustment power supply circuit is connected to the positive output end of the beam containment power supply circuit. The positive output end of the coarse bias adjustment power supply circuit and the negative output end of the beam containment power supply circuit serve as the output end of the bias regulation low-voltage circuit.

[0011] The bias regulation high-voltage circuit includes a half-bridge inverter circuit, a high-voltage isolation transformer and a high-voltage rectifier and filter circuit. The output end of the bias regulation low-voltage circuit is connected to the input end of the half-bridge inverter circuit, the output end of the half-bridge inverter circuit is connected to the input end of the high-voltage isolation transformer, the output end of the high-voltage isolation transformer is connected to the input end of the high-voltage rectifier and filter circuit, and the output end of the high-voltage rectifier and filter circuit serves as the output end of the bias regulation high-voltage circuit.

[0012] Preferably, the voltage setting value calculated by the single chip control circuit according to the electron beam current set value and the electron beam current feedback value includes the voltage setting value of the bias coarse adjustment power supply circuit, the voltage setting value of the bias fine adjustment power supply circuit and the voltage setting value of the beam closing power supply circuit;

[0013] When the electron beam current setting value is 0 or the electron beam current output is not started:

[0014] The voltage setting value of the coarse bias power supply circuit is the maximum output voltage of the coarse bias power supply circuit, the voltage setting value of the fine bias power supply circuit is the maximum output voltage of the fine bias power supply circuit, and the voltage setting value of the beam containment power supply circuit is the maximum output voltage of the beam containment power supply circuit;

[0015] When the electron beam current set value is greater than 0 and the electron beam current output is enabled:

[0016] The voltage setting value of the bias coarse adjustment power supply circuit is 95%U pg , the voltage setting value of the bias fine-tuning power supply circuit is 5%U pg +ΔU pg , the voltage setting value of the beam closed power supply circuit is 0, where U pg The output voltage of the bias regulating low-voltage circuit corresponding to the electron beam current is the given value of the electron beam current, ΔU pg It is the difference between the output voltage value of the bias regulation low voltage circuit corresponding to when the electron beam current size is the electron beam current given value and the output voltage value of the bias regulation low voltage circuit corresponding to when the electron beam current size is the electron beam current feedback value.

[0017] Preferably, the maximum output voltage of the bias fine adjustment power supply circuit is 10% of the maximum output voltage of the bias coarse adjustment power supply circuit.

[0018] Preferably, the bias coarse adjustment power supply circuit, the bias fine adjustment power supply circuit, and the beam enclosed power supply circuit have the same circuit structure, and all include an AC / DC rectifier power supply unit, an input filter capacitor C1, a power switch tube T1, a freewheeling diode D1, a filter inductor L1, an output filter capacitor C2, a voltage sampling circuit, a PI adjustment circuit, a PWM generation circuit, and an isolation drive circuit. Their positional relationship is:

[0019] AC380V AC power is input to the AC / DC rectifier power supply unit. The positive output end of the AC / DC rectifier power supply unit is connected to the first end of the input filter capacitor C1 and the collector of the power switch tube T1. The negative output end of the AC / DC rectifier power supply unit is connected to the second end of the input filter capacitor C1, the positive electrode of the freewheeling diode D1, and the second end of the output filter capacitor C2. The emitter of the power switch tube T1 is connected to the negative electrode of the freewheeling diode D1 and the first end of the filter inductor L1. The second end of the filter inductor L1 is connected to the first end of the output filter capacitor C2. The two ends of the output filter capacitor C2 serve as the output ends of the bias coarse adjustment power supply circuit.

[0020] The output end of the voltage sampling circuit is connected to the input end of the PI regulation circuit. The voltage sampling circuit samples the output end voltage of the bias coarse adjustment power supply circuit and sends the sampled voltage to the PI regulation circuit.

[0021] The output end of the PI regulation circuit is connected to the PWM generation circuit. The PI regulation circuit obtains a regulation voltage according to the sampled voltage and the voltage setting value, and sends the regulation voltage to the PWM generation circuit.

[0022] The output end of the PWM generating circuit is connected to the input end of the isolation driving circuit, the PWM generating circuit generates a PWM waveform according to the adjustment voltage, and sends the PWM waveform to the isolation driving circuit;

[0023] The output end of the isolation drive circuit is connected to the base of the power switch tube T1, and the isolation drive circuit controls the power switch tube T1 to be turned on and off according to the PWM waveform.

[0024] Beneficial effects: Compared with the prior art, the present invention has the following significant beneficial effects:

[0025] The multi-stage bias power supply system of the present invention uses a bias coarse adjustment power supply, a bias fine adjustment power supply, and a beam containment power supply connected in series and performs multi-stage regulation, as follows:

[0026] By setting up a dedicated beam containment power supply, when the electron beam output needs to be zero, the beam containment power supply is connected in series with the bias coarse adjustment power supply and the bias fine adjustment power supply to provide a sufficiently high beam containment voltage, which greatly improves the reliability of the beam containment.

[0027] When the electron beam output is required to be non-zero, the beam closing power supply output is immediately set to 0, and the bias coarse adjustment power supply output is set to 95% of the required set beam bias value, which can greatly improve the dynamic response speed of electron beam adjustment;

[0028] When the beam closure power supply output is 0 and the bias coarse adjustment power supply outputs 95% of the required bias voltage, the remaining 5% bias value is provided by the bias fine adjustment power supply. The grid bias and electron beam current are dynamically adjusted in a small range through 100% pulse width adjustment of the bias fine adjustment power supply, which can greatly improve the adjustment accuracy of the bias power supply and electron beam current, thereby achieving high-precision control of small beam and large beam output. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a relationship curve between the gate bias voltage and the electron beam current;

[0030] Figure 2 The schematic diagram of the structure of the multi-stage bias power supply and its peripheral circuits of the present invention is shown;

[0031] Figure 3 This is a schematic diagram of the working process of the beam feedback closed loop regulating bias voltage and electron beam current according to the present invention;

[0032] Figure 4 Schematic diagram of the circuit structure of the bias coarse adjustment power supply of the present invention;

[0033] Figure 5 Schematic diagram of the circuit structure of the half-bridge inverter circuit of the present invention;

[0034] Among them: 101, high-voltage acceleration power supply circuit; 102, bias coarse adjustment power supply circuit; 103, bias fine adjustment power supply circuit; 104, beam closing power supply circuit; 105, single-chip microcomputer control circuit; 106, half-bridge inverter circuit; 107, high-voltage isolation transformer; 108, high-voltage rectifier and filter circuit; 109, host computer; 110, filament heating power supply circuit; 111, electron gun; 112, electron gun grid; 113, electron gun cathode filament; 114, electron gun anode; 115, electron beam; 201, AC / DC rectifier power supply unit; 207, voltage sampling circuit; 208, PI regulation circuit; 209, PWM generation circuit; 210, isolation drive circuit; 601, digital PID regulator; 602, bias regulation low-voltage circuit; 603, bias regulation high-voltage circuit; 604, beam feedback circuit. DETAILED DESCRIPTION

[0035] The present invention will be further described below with reference to the accompanying drawings.

[0036] The present invention discloses a multi-stage bias power supply for precise electron beam control. To address the shortcomings of conventional electron beam bias power supplies in terms of low beam current control accuracy, the present invention connects a bias coarse adjustment power supply circuit 102, a bias fine adjustment power supply circuit 103, and a beam sealing power supply circuit 104 in series on the low-voltage side, and then connects the series connection to the high-voltage side to form a multi-stage bias DC power supply. The bias adjustment low-voltage circuit 602 of the multi-stage bias power supply of the present invention is composed of three inverter power supply circuits, namely, a bias coarse adjustment power supply circuit 102, a bias fine adjustment power supply circuit 103, and a beam sealing power supply circuit 104, connected in series. The electron beam current is controlled by multi-stage regulation of the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam sealing power supply circuit 104. At the same time, the multi-stage bias power supply of the present invention can also adjust the output voltage of the bias fine-tuning power supply circuit 103 in a closed-loop manner through the electron beam current feedback value, thereby realizing dynamic adjustment of the multi-stage bias power supply output voltage and achieving high-precision control of the electron beam current.

[0037] The multi-stage bias power supply for precise electron beam control described in the present invention has an input end for inputting an electron beam current set value and an electron beam current feedback value, a negative output end of its output voltage connected to the electron gun grid 112, and a positive output end of its output voltage connected to the positive output end of the filament heating power supply circuit 110, the negative output end of the filament heating power supply circuit 110 and the negative output end of the high-voltage acceleration power supply circuit 101 through resistors, respectively. The positive output end of the filament heating power supply circuit 110 and the negative output end of the filament heating power supply circuit 110 are connected to the two ends of the electron gun cathode filament 113.

[0038] like Figure 2 As shown, in one embodiment of the present invention: the positive output terminal of the high-voltage acceleration power supply circuit 101 is connected to the ground line, the negative output terminal of the high-voltage acceleration power supply circuit 101 is connected to the positive output terminal of the filament heating power supply circuit 110 through resistors R1 and R2, the negative output terminal of the high-voltage acceleration power supply circuit 101 is connected to the negative output terminal of the filament heating power supply circuit 110 through resistors R1 and R3, the electron gun cathode filament 113 is connected between the positive output terminal and the negative output terminal of the filament heating power supply circuit 110, and the electron gun anode 114 is also connected to the ground line. Therefore, a high-voltage acceleration electrostatic field of -60 kV or higher can be formed between the electron gun cathode filament 113 and the electron gun anode 114 to achieve high-voltage acceleration of electrons;

[0039] The host computer 109 or other input device sets the electron beam current given value I bgThe voltage is transmitted to a multi-stage bias power supply. The positive output terminal of the multi-stage bias power supply is connected to the positive output terminal of the filament heating power supply circuit 110 through a resistor R2. The positive output terminal of the multi-stage bias power supply is connected to the negative output terminal of the filament heating power supply circuit 110 through a resistor R3. The negative output terminal of the multi-stage bias power supply is connected to the electron gun grid 112. Thus, an electric field can be formed in the space between the electron gun grid 112 and the electron gun cathode filament 113. By adjusting the output voltage of the multi-stage bias power supply, the electron beam current size can be controlled. At the same time, the multi-stage bias power supply collects the actual electron beam current feedback value I bf , the output voltage between its positive output terminal and negative output terminal is adjusted in a closed loop, thereby realizing the control of the electron beam current.

[0040] The multi-stage bias power supply of the present invention includes a bias regulation low-voltage circuit 602, a bias regulation high-voltage circuit 603, a beam feedback circuit 604 and a single-chip microcomputer control circuit 105, wherein: the bias regulation low-voltage circuit 602 includes a bias coarse adjustment power supply circuit 102, a bias fine adjustment power supply circuit 103 and a beam closing power supply circuit 104, and the bias regulation high-voltage circuit 603 includes a half-bridge inverter circuit 106, a high-voltage isolation transformer 107 and a high-voltage rectifier filter circuit 108. Figure 2 As shown, the positional relationship between them is:

[0041] The three inverter power supply units, namely the coarse bias adjustment power supply circuit 102, the fine bias adjustment power supply circuit 103 and the beam containment power supply circuit 104, are connected in series to form the bias adjustment low-voltage circuit 602. Specifically, the negative output terminal of the coarse bias adjustment power supply circuit 102 is connected to the positive output terminal of the fine bias adjustment power supply circuit 103, the negative output terminal of the fine bias adjustment power supply circuit 103 is connected to the positive output terminal of the beam containment power supply circuit 104, the positive output terminal of the coarse bias adjustment power supply circuit 102 serves as the positive output terminal of the bias adjustment low-voltage circuit 602, and the negative output terminal of the beam containment power supply circuit 104 serves as the negative output terminal of the bias adjustment low-voltage circuit 602.

[0042] The output of the beam feedback circuit 604 is connected to the input of the single-chip control circuit 105. The output of the single-chip control circuit 105 is connected to the input of the bias coarse adjustment power supply circuit 102, the input of the bias fine adjustment power supply circuit 103 and the input of the beam closing power supply circuit 104. The single-chip control circuit 105 receives the set electron beam current given value I bg , and then output the voltage setting value U pgc 、U pgx 、U pgf The bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103 and the beam closing power supply circuit 104, and the single chip control circuit 105 receive the actual electron beam current feedback value I collected and fed back by the beam feedback circuit 604. bf , closed-loop regulation of the output voltage of the bias fine-tuning power supply circuit 103;

[0043] The output end of the bias regulation low-voltage circuit 602 is connected to the input end of the half-bridge inverter circuit 106, and is further converted into a 40kHz high-frequency AC square wave by the half-bridge inverter circuit 106; the output end of the half-bridge inverter circuit 106 is connected to the input end of the high-voltage isolation transformer 107, that is, the above-mentioned high-frequency AC square wave is further transmitted to the high-voltage isolation transformer 107 for boosting; the output end of the high-voltage isolation transformer 107 is connected to the input end of the high-voltage rectifier and filter circuit 108, that is, the above-mentioned boosted high-frequency AC square wave is further converted into a gate bias voltage of approximately 2000V after passing through the high-voltage rectifier and filter circuit 108. This gate bias voltage is the output voltage of the multi-stage bias power supply described in the present invention. The output positive electrode of the gate bias voltage is connected to the electron gun cathode filament 113 through a resistor, and the output negative electrode of the gate bias voltage is connected to the electron gun grid 112. As a result, a -2000V electric field can be formed in the space between the electron gun grid 112 and the electron gun cathode filament 113. By adjusting the output voltage of the gate bias voltage, the electron beam current size can be controlled.

[0044] In the bias regulation low-voltage circuit 602, the beam containment power supply circuit 104 is primarily used to provide the containment voltage, the bias coarse adjustment power supply circuit 102 is primarily used to provide 95% of the bias voltage for beam control, and the bias fine adjustment power supply circuit 103 is used to provide the remaining 5% of the bias voltage for beam control. The maximum bias voltage generated by the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam containment power supply circuit 104 connected in series via the bias regulation high-voltage circuit 603 can completely contain electron escape. However, the maximum bias voltage generated by the bias coarse adjustment power supply circuit 102 and the bias fine adjustment power supply circuit 103 connected in series via the bias regulation high-voltage circuit 603 is slightly higher than the bias voltage U at the critical beam exit point. pTH , to ensure that the output beam current can still be 0 after the beam blocking power supply circuit 104 is turned off. The maximum output voltage of the bias fine adjustment power supply circuit 103 is 10% of the maximum output voltage of the bias coarse adjustment power supply circuit 102.

[0045] The single chip control circuit 105 of the present invention is composed of a PIC18F2423 single chip microcomputer and its peripheral circuits, and its function is to receive the given value I of the electron beam current. bg , and then output the voltage setting value U according to the control algorithm pgc 、U pgx 、U pgf To the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam closing power supply circuit 104; at the same time, the single chip control circuit 105 receives the electron beam current feedback value I of the beam feedback circuit 604 bf , further close-loop adjustment is performed on the output voltage of the bias fine-tuning power supply circuit 103, and finally dynamic small-range adjustment of the output voltage of the multi-level bias power supply is achieved.

[0046] In the present invention, the single chip control circuit 105 outputs the voltage setting value U of the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam closing power supply circuit 104 according to the control algorithm. pgc 、U pgx 、U pgf The algorithm is as follows:

[0047]

[0048] Among them, U pg The output electron beam current is just equal to the given value of electron beam current I bg The corresponding bias voltage regulation low voltage circuit 602 output voltage, U pgcmax is the maximum output voltage of the bias coarse adjustment power supply circuit 102, U pgxmax is the maximum output voltage of the bias fine-tuning power supply circuit 103, U pgfmax It is the maximum output voltage of the beam confinement power supply circuit 104.

[0049] The single chip control circuit 105 receives the given value of electron beam current I bg Then, the single chip control circuit 105 searches the corresponding table of the calibrated electron beam current and the output voltage of the bias regulating low voltage circuit 602 to obtain the current electron beam current given value I bg The corresponding bias voltage regulates the output voltage U of the low voltage circuit 602 pg The corresponding table is obtained as follows: first, a plurality of sets of electron beam current sizes and the corresponding output voltage values ​​of the bias regulating low-voltage circuit 602 are obtained by experimental methods, then the most appropriate relationship function is obtained by curve fitting the aforementioned plurality of sets of electron beam current sizes and output voltage values, and finally, the output voltage value of the bias regulating low-voltage circuit 602 corresponding to each electron beam current size is obtained according to the aforementioned relationship function, and the corresponding values ​​are compiled into a corresponding table. When the electron beam current is given a value I bg When the voltage is 0 or the electron beam is not started, the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam closing power supply circuit 104 all output the maximum voltage, that is, the voltage setting value U of the bias coarse adjustment power supply circuit 102. pgc is the maximum output voltage U of the bias coarse adjustment power supply circuit 102 pgcmax , the voltage setting value U of the bias fine adjustment power supply circuit 103 pgx is the maximum output voltage U of the bias fine-tuning power supply circuit 103 pgxmax , the voltage setting value U of the beam enclosing power supply circuit 104 pgf is the maximum output voltage U of the beam enclosing power supply circuit 104 pgfmax, the three power supplies are connected in series to provide the maximum voltage output, provide a sufficiently high beam closing voltage, and greatly improve the reliability of the beam closing; when the electron beam current is given value I bg When it is not 0 and the electron beam output is enabled, the beam closing power supply circuit 104 outputs 0V, and the bias coarse adjustment power supply circuit 102 outputs U pg 95% of the bias voltage, the fine-tuning power supply circuit 103 outputs U in advance. pg 5%, that is, the voltage setting value U of the bias coarse adjustment power supply circuit 102 pgc 95% of the output voltage U pg , the voltage setting value U of the bias fine adjustment power supply circuit 103 pgx 5% of the output voltage U pg , the voltage setting value U of the beam enclosing power supply circuit 104 pgf When the beam output is started, the output of the beam closing power supply circuit 104 is immediately set to 0, and the output of the bias coarse adjustment power supply circuit 102 is set to U pg 95% of the original value, which can greatly improve the dynamic response speed of electron beam current regulation.

[0050] Figure 3 The present invention is based on the electron beam current feedback value I bf The working principle diagram of electron beam closed-loop control, where:

[0051] The single chip control circuit 105 receives the electron beam current feedback value I from the beam current feedback circuit 604. bf , and the given value of electron beam current I bg The closed-loop regulation of the output voltage of the bias fine-tuning power supply circuit 103 is an outer-loop regulation. The output U pgx +ΔU pg As the voltage given value of the bias fine-tuning power supply circuit 103 output voltage inner loop regulation.

[0052] Electron beam current set value I bg and electron beam current feedback value I bf Input to the single chip control circuit 105, the bias voltage adjustment output variation ΔU is obtained by the digital PID regulator 601 inside the single chip control circuit 105. pg , bias regulation output change ΔU pg The electron beam current size is the given value of the electron beam current I bg The output voltage value of the bias regulating low voltage circuit 602 and the electron beam current are the electron beam current feedback value I bf The difference between the output voltage values ​​of the bias regulation low voltage circuit 602 corresponding to the time, the bias regulation output variation ΔU pg The voltage setting value U of the bias fine adjustment power supply circuit 103 at the previous moment pgxThe sum is used as the current voltage setting value of the bias fine adjustment power supply circuit 103. At this time, the output voltage of the bias coarse adjustment power supply circuit 102 is U pc , the output voltage of the bias fine-tuning power supply circuit 103 is U px , the output voltage of the bias regulation low voltage circuit 602 is U p =U pc +U px Then, the output of the bias regulation low voltage circuit 602 is connected to the bias regulation high voltage circuit 603, and finally the gate bias and the electron beam 115 are controlled. The beam current feedback circuit 604 samples the electron beam 115 and feeds the current electron beam current feedback value I bf Feedback to the single chip control circuit 105. During the beam current adjustment process, the output voltage of the bias coarse adjustment power supply circuit 102 remains stable, and the electron beam current feedback value I bf Only the output voltage of the bias fine-tuning power supply circuit 103 is closed-loop adjusted, that is, the output of the gate bias power supply is adjusted in a small range by using 100% pulse width variation of the bias fine-tuning power supply circuit 103. This can greatly improve the adjustment accuracy of the bias voltage, thereby achieving high-precision control of the beam, and effectively solving problems such as processing defects caused by low control accuracy of small and large beams.

[0053] The bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103, and the beam closing power supply circuit 104 described in the present invention have the same circuit structure. Taking the bias coarse adjustment power supply circuit 102 as an example: the bias coarse adjustment power supply circuit 102 includes an AC / DC rectifier power supply unit 201, an input filter capacitor C1, a power switch tube T1, a freewheeling diode D1, a filter inductor L1, an output filter capacitor C2, a voltage sampling circuit 207, a PI adjustment circuit 208, a PWM generation circuit 209, and an isolation drive circuit 210. Figure 4 As shown, their positional relationship is:

[0054] The positive output end of the AC / DC rectifier power supply unit 201 is connected to the first end of the input filter capacitor C1 and the collector of the power switch tube T1. The negative output end of the AC / DC rectifier power supply unit 201 is connected to the second end of the input filter capacitor C1, the positive electrode of the freewheeling diode D1, and the second end of the output filter capacitor C2. The emitter of the power switch tube T1 is connected to the negative electrode of the freewheeling diode D1 and the first end of the filter inductor L1. The second end of the filter inductor L1 is connected to the first end of the output filter capacitor C2. After the AC380V AC power is connected to the AC / DC rectifier power supply unit 201, it is converted into a stable DC voltage output, and then connected to the BUCK chopper circuit composed of the input filter capacitor C1, the power switch tube T1, the freewheeling diode D1, the filter inductor L1, and the output filter capacitor C2 for output voltage regulation. The voltage across the output filter capacitor C2 is the output voltage U of the bias coarse adjustment power supply circuit 102. fin, where the first end of the output filter capacitor C2 is the positive output end, and the voltage is U OUT+ , the second end of the output filter capacitor C2 is the negative output end, and the voltage is U OUT- ;

[0055] The voltage sampling circuit 207 senses the output voltage U of the bias coarse adjustment power supply circuit 102. fin Sampling voltage U f , voltage U f The voltage setting value U of the bias coarse adjustment power supply circuit 102 pgc The PI regulation circuit 208 is input together for voltage regulation. The output of the PI regulation circuit 208 is then connected to the PWM generation circuit 209 to adjust the pulse width of the PWM waveform. The PWM waveform output by the PWM generation circuit 209 is then connected to the base of the power switch tube T1 after passing through the isolation drive circuit 210 to control the power switch tube T1 to be turned on and off, thereby achieving the adjustment and stable output of the output voltage of the bias coarse adjustment power supply circuit 102.

[0056] The bias fine adjustment power supply circuit 103 and the beam closing power supply circuit 104 are similar. The PI adjustment circuit input U pgx +ΔU pg , the PI regulation circuit input U in the beam closed power supply circuit 104 pgf .

[0057] The half-bridge inverter circuit 106 of the present invention includes a filter capacitor C3, a half-bridge capacitor C4, a half-bridge capacitor C5, a power switch tube T2 and a power switch tube T3. Figure 5 As shown, their positional relationship is:

[0058] A first end of the filter capacitor C3 is connected to a first end of the half-bridge capacitor C4 and the collector of the power switch tube T2. A second end of the filter capacitor C3 is connected to a second end of the half-bridge capacitor C5 and the emitter of the power switch tube T3. The second end of the half-bridge capacitor C4 is connected to the first end of the half-bridge capacitor C5. The emitter of the power switch tube T2 is connected to the collector of the power switch tube T3. The bases of the power switch tubes T2 and T3 are both connected to a universal drive and control circuit. The emitter of the power switch tube T2 and the second end of the half-bridge capacitor C4 serve as output ends of the half-bridge inverter circuit 106.

[0059] The output voltage of the bias regulation low voltage circuit 602 composed of the bias coarse adjustment power supply circuit 102, the bias fine adjustment power supply circuit 103 and the beam closing power supply circuit 104 is input to the half-bridge inverter circuit 106 and then converted into a 40kHz high-frequency AC square wave, which is then input to the high-voltage isolation transformer 107 for isolation and boosting.

[0060] The high-voltage isolation transformer 107 of the present invention is used to achieve voltage conversion and isolation between the primary voltage and the secondary voltage. The framework is made of Teflon material and is wound with a nanocrystalline iron core and enameled wire.

[0061] The high-voltage rectifier filter circuit 108 of the present invention adopts a filter circuit composed of a high-voltage fast recovery diode silicon stack and a high-voltage thin film capacitor, and its function is to rectify and filter the high-frequency AC square wave output by the high-voltage isolation transformer 107 into a stable DC bias output.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A multi-stage bias power supply for precise electron beam control, characterized in that: It includes a bias voltage regulating low voltage circuit (602), a bias voltage regulating high voltage circuit (603), a beam feedback circuit (604) and a single chip microcomputer control circuit (105); The output end of the beam feedback circuit (604) is connected to the input end of the single-chip microcomputer control circuit (105), and the beam feedback circuit (604) collects the electron beam feedback value and sends the electron beam feedback value to the single-chip microcomputer control circuit (105); The output end of the single-chip microcomputer control circuit (105) is connected to the input end of the bias voltage regulating low-voltage circuit (602), and the single-chip microcomputer control circuit (105) calculates a voltage setting value according to the electron beam current set value and the electron beam current feedback value, and sends the voltage setting value to the bias voltage regulating low-voltage circuit (602); The output end of the bias regulating low voltage circuit (602) is connected to the input end of the bias regulating high voltage circuit (603), the positive output end of the bias regulating high voltage circuit (603) is connected to the electron gun cathode filament (113), and the negative output end of the bias regulating high voltage circuit (603) is connected to the electron gun grid (112); The bias regulation low voltage circuit (602) comprises a bias coarse adjustment power supply circuit (102), a bias fine adjustment power supply circuit (103) and a beam closing power supply circuit (104); the input end of the bias coarse adjustment power supply circuit (102), the input end of the bias fine adjustment power supply circuit (103) and the input end of the beam closing power supply circuit (104) are all connected to the output end of the single chip control circuit (105); the negative output end of the bias coarse adjustment power supply circuit (102) is connected to the positive output end of the bias fine adjustment power supply circuit (103); the negative output end of the bias fine adjustment power supply circuit (103) is connected to the positive output end of the beam closing power supply circuit (104); the positive output end of the bias coarse adjustment power supply circuit (102) and the negative output end of the beam closing power supply circuit (104) serve as the output end of the bias regulation low voltage circuit (602); The bias regulation high voltage circuit (603) comprises a half-bridge inverter circuit (106), a high voltage isolation transformer (107) and a high voltage rectifier filter circuit (108); the output end of the bias regulation low voltage circuit (602) is connected to the input end of the half-bridge inverter circuit (106); the output end of the half-bridge inverter circuit (106) is connected to the input end of the high voltage isolation transformer (107); the output end of the high voltage isolation transformer (107) is connected to the input end of the high voltage rectifier filter circuit (108); and the output end of the high voltage rectifier filter circuit (108) serves as the output end of the bias regulation high voltage circuit (603).

2. A multi-stage bias power supply for precise electron beam control according to claim 1, characterized in that: The voltage setting value calculated by the single chip control circuit (105) according to the electron beam current given value and the electron beam current feedback value includes the voltage setting value of the bias coarse adjustment power supply circuit (102), the voltage setting value of the bias fine adjustment power supply circuit (103) and the voltage setting value of the beam closing power supply circuit (104); When the electron beam current setting value is 0 or the electron beam current output is not started: The voltage setting value of the bias coarse adjustment power supply circuit (102) is the maximum output voltage of the bias coarse adjustment power supply circuit (102), the voltage setting value of the bias fine adjustment power supply circuit (103) is the maximum output voltage of the bias fine adjustment power supply circuit (103), and the voltage setting value of the beam closing power supply circuit (104) is the maximum output voltage of the beam closing power supply circuit (104); When the electron beam current set value is greater than 0 and the electron beam current output is enabled: The voltage setting value of the bias coarse adjustment power supply circuit (102) is 95% U pg , the voltage setting value of the bias fine-tuning power supply circuit (103) is 5%U pg +ΔU pg , the voltage setting value of the beam closing power supply circuit (104) is 0, where U pg is the output voltage of the bias regulating low voltage circuit (602) corresponding to the electron beam current size being a given electron beam current value, ΔU pg It is the difference between the output voltage value of the bias regulating low voltage circuit (602) corresponding to when the electron beam current size is the electron beam current given value and the output voltage value of the bias regulating low voltage circuit (602) corresponding to when the electron beam current size is the electron beam current feedback value.

3. The multi-stage bias power supply for precise electron beam control according to claim 2, characterized in that: The maximum output voltage of the bias fine adjustment power supply circuit (103) is 10% of the maximum output voltage of the bias coarse adjustment power supply circuit (102).

4. The multi-stage bias power supply for precise electron beam control according to claim 1, characterized in that: The bias coarse adjustment power supply circuit (102), the bias fine adjustment power supply circuit (103), and the beam closing power supply circuit (104) have the same circuit structure, and all include an AC / DC rectifier power supply unit (201), an input filter capacitor C1, a power switch tube T1, a freewheeling diode D1, a filter inductor L1, an output filter capacitor C2, a voltage sampling circuit (207), a PI adjustment circuit (208), a PWM generation circuit (209), and an isolation drive circuit (210). Their positional relationship is: AC380V alternating current is input to an AC / DC rectifier power supply unit (201), a positive output end of the AC / DC rectifier power supply unit (201) is connected to a first end of an input filter capacitor C1 and a collector of a power switch tube T1, a negative output end of the AC / DC rectifier power supply unit (201) is connected to a second end of the input filter capacitor C1, a positive electrode of a freewheeling diode D1, and a second end of an output filter capacitor C2, an emitter of the power switch tube T1 is connected to a negative electrode of the freewheeling diode D1 and a first end of a filter inductor L1, a second end of the filter inductor L1 is connected to a first end of an output filter capacitor C2, and both ends of the output filter capacitor C2 serve as output ends of a bias coarse adjustment power supply circuit (102); The output end of the voltage sampling circuit (207) is connected to the input end of the PI regulation circuit (208), and the voltage sampling circuit (207) samples the output end voltage of the bias coarse adjustment power supply circuit (102) and sends the sampled voltage to the PI regulation circuit (208); The output end of the PI regulating circuit (208) is connected to the PWM generating circuit (209), and the PI regulating circuit (208) obtains a regulating voltage according to the sampled voltage and the voltage setting value, and sends the regulating voltage to the PWM generating circuit (209); The output end of the PWM generating circuit (209) is connected to the input end of the isolation driving circuit (210), and the PWM generating circuit (209) generates a PWM waveform according to the adjustment voltage and sends the PWM waveform to the isolation driving circuit (210); The output end of the isolation drive circuit (210) is connected to the base of the power switch tube T1, and the isolation drive circuit (210) controls the power switch tube T1 to be turned on and off according to the PWM waveform.

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