A low-level high-precision detection device based on gated high voltage of field effect tube

Abstract

The present invention belongs to the field of space plasma environment detection technology, and relates to a low-level high-precision detection device of gated high voltage based on field effect tube, including a level processing circuit, which is implemented based on field effect tube, and is used to filter the high-voltage part of the input gated high voltage and only output low voltage; an ADC conversion circuit, which is used to periodically output the gated high voltage level data after analog-to-digital conversion at a set frequency under the control of a data processing unit; a data processing unit, which is implemented based on FPGA, is used to control the ADC conversion circuit, collect the level data output by the ADC conversion circuit, and package and output it to the PC end through an RS422 interface. By adopting the device of the present invention, the measurement range of the oscilloscope is reduced from 300V to 3V, and the measurement accuracy is improved from 50V / div to 0.5V / div, which overcomes the problem of low measurement accuracy of high-low level switching of gated high voltage, and avoids the risk of high voltage discharge caused by direct measurement of high voltage by the oscilloscope probe.

Description

Technical Field

[0001] The invention belongs to the technical field of space plasma environment detection, and in particular relates to a low-level high-precision detection device based on gated high voltage of a field effect tube. Background Art

[0002] In the detection of space plasma environment, ion energy, direction, flux and mass spectrometry are important detection elements. Among them, there is a wide application demand for gated high voltage in plasma flux measurement and ion mass spectrometry analysis. The level stability of gated high voltage after high and low level switching is an important parameter for evaluating the performance of gated high voltage.

[0003] First, gated high voltage is mainly used for flux control of ion imaging detection in the ion sphere. The typical ionospheric detection satellite has an orbit of 340~450km, and the total variation range of ion differential flux reaches about 8 orders of magnitude (5×10 6 cm-2s-1sr-1eV-1~5×10 14 The dynamic range is very short (cm-2s-1sr-1eV-1), and the absolute value is relatively large, which is a typical area where large flux ions exist. The basic working principle of ion imaging detection is to use a microchannel plate (MCP) and a fluorescent screen to amplify and image the charge signal of a single ion, and then finely analyze the density, temperature, drift velocity and spatial distribution of ion components, which has the advantage of high spatiotemporal analysis. However, when this type of ion imaging detection instrument is measured in an environment with extremely large ion flux in the ionosphere, if flux control is not performed, it will be saturated and cannot work normally. Figure 1 The figure shows a cross-sectional view of the ion imager design. A gate electrode is set at the ion entrance to limit the incident ion beam by applying a gate high voltage. When the gate high voltage output is high, the gate is closed to prevent ions from entering; when the output is low, the gate is opened to allow ions to enter, thereby ensuring that the microchannel plate (MCP) and the fluorescent screen operate within an appropriate dynamic range.

[0004] Secondly, gated high voltage is the key technology for mass spectrometry based on time-of-flight measurement system. The basic principle of mass spectrometer based on time-of-flight measurement system is: . Where m is the ion mass (unit: kg), v is the ion velocity (unit: m / s). The flight velocity v can be calculated based on the ion flight time T, and the ion energy E can be calculated based on the high voltage amplitude of the electrostatic analyzer; combined with The ion composition information can be calculated.

[0005] like Figure 2The figure shows the application of gated high voltage in the time-of-flight measurement system. TDC-GPX is a time-of-flight measurement chip that times the time interval between the start signal START and the stop signal STOP. The gated high voltage output by the gated high voltage module is used to control the gated electrode to "open the door": that is, to allow the incident ions to enter, and at the same time, it serves as the start signal START of the TDC-GPX time-of-flight measurement. After the incident ions pass through the free flight zone with a distance of L and reach the detector, a digital pulse is output as the stop signal STOP of the TDC-GPX time-of-flight measurement. TDC-GPX finally gives the flight time of the incident ions.

[0006] like Figure 3 As shown, the characteristic of gated high voltage is that the output voltage switches periodically between high level and low level at a fixed frequency, and the high level and low level pulse width are fixed. In the application of plasma detectors, there are index requirements for the high and low level amplitudes, high level and low level switching time, minimum pulse width, and level stability after switching of gated high voltage. The gated high voltage used for ion flux control requires a high level of +300V (closed gate), a low level of 0V (open gate), an adjustable pulse width, a minimum width of 10us, and a high level and low level switching time of 100ns. It is required that the low level 0V output and the level effective holding time need to be accurate, otherwise the flux control accuracy will be affected. The gated high voltage used for mass spectrometers requires a high level of +300V (closed gate), a low level of 0V (open gate), an adjustable pulse width, a minimum width of 30ns, and a high level and low level switching time should be less than 20ns. It is required that the low level 0V output and the level effective holding time need to be accurate, otherwise the mass spectrometry resolution will be affected.

[0007] Due to the charging and discharging of parasitic capacitance in the gate-controlled high-voltage circuit, the gate-controlled high voltage will overshoot at the moment of opening the gate, which will damage the components in the gate-controlled high-voltage circuit and affect the service life of the components. This overshoot phenomenon can be eliminated by debugging the resistance and capacitance matching in the circuit, but it is necessary to be able to measure the level stabilization process after the high and low level switching with high precision.

[0008] In different application scenarios, the level stability state after the high and low level switching of the gated high voltage is an important parameter for evaluating the performance of the gated high voltage. On the one hand, the level state directly affects the detection index of the detector, and on the other hand, it affects the reliability of the gated high voltage. However, during the debugging of the gated high voltage circuit, due to the limitations of measurement technology, the measurement accuracy of the stable state of the level after the high and low level switching of the gated high voltage is low.

[0009] Since the high level of the gated high voltage output is +300V, the voltage amplitude is high, the amplitude difference between the high level and the low level is 300V, the amplitude difference is large, the high and low level switching frequency is greater than 10kHz, and the low level holding time is less than 10us.

[0010] At present, the high and low level switching process of gated high voltage output is measured by an oscilloscope. The oscilloscope needs to cover the range of +300V, and its measurement resolution can only reach 50V / div, which has low accuracy and cannot accurately measure the stable state of the level after switching. In addition, the high level of gated high voltage output is high voltage +300V. If the oscilloscope probe is used to measure directly, there is a risk of high voltage discharge, which poses a safety hazard to testers. Summary of the invention

[0011] The purpose of the present invention is to overcome the defects of the prior art and propose a low-level high-precision detection device based on gated high voltage of a field effect tube.

[0012] In view of this, the present invention discloses a low-level high-precision detection device based on gated high voltage of field effect tube, comprising: a level processing circuit, an ADC conversion circuit and a data processing unit, wherein:

[0013] The level processing circuit is implemented based on a field effect transistor and is used to filter the high voltage part of the input gated high voltage and output only a low voltage;

[0014] The ADC conversion circuit is used to periodically output the gated high voltage level data after analog-to-digital conversion at a set frequency under the control of the data processing unit;

[0015] The data processing unit is implemented based on FPGA, and is used to control the ADC conversion circuit, collect the level data output by the ADC conversion circuit, and package and output it to the PC end through the RS422 drive circuit.

[0016] Preferably, the high level value of the input gated high voltage is +300V, and the low level value is 0V.

[0017] Preferably, in the level processing circuit, the breakdown voltage V DS is 500V, the gate-source turn-on threshold voltage V GS Greater than 2V, the gate-source can withstand a rated voltage range of ±20V, the gate voltage V G Fixed at 5V, source voltage V S In the range of 0V~3V, the drain source DS is turned on, and the source voltage V S When the voltage is greater than 3V, the drain-source DS of the field effect tube is cut off.

[0018] Preferably, the ADC conversion circuit adopts a 16-bit high-precision ADC converter.

[0019] Preferably, the data processing unit includes FPGA and RSS422 driving circuit, wherein:

[0020] The FPGA controls the ADC conversion circuit to periodically collect the level data output by the level processing circuit at a frequency of 100kHz and transmit it to the RS422 drive circuit;

[0021] The RS422 driving circuit converts the level data from a single-ended signal to a differential signal and outputs it to the PC end.

[0022] Preferably, the interface signals between the ADC conversion circuit and the FPGA include: an ADC data bus, an ADC chip select signal, an ADC conversion enable flag signal, and an ADC conversion completion flag signal.

[0023] Preferably, the PC terminal stores the data of the high-low level switching process of the gated high voltage and the low-level stable state for later data analysis and comparison.

[0024] Compared with the prior art, the advantages of the present invention are:

[0025] 1. The present invention utilizes the on-off characteristics of the field effect tube to design a gated high voltage level processing circuit, filters the high voltage part of the gated high voltage, and outputs only a low voltage. After using the invention, the oscilloscope measurement range is reduced by 3V from 300V, and the measurement accuracy is improved from 50V / div to 0.5V / div, thereby overcoming the problem of low measurement accuracy of high and low level switching of the gated high voltage and avoiding the risk of high voltage discharge caused by the oscilloscope probe directly measuring the high voltage.

[0026] 2. The output of the present invention integrates the analog output interface after level processing and the RS422 digital output interface. The detection level can be viewed in real time through an oscilloscope, and the data can also be stored in the PC to achieve data analysis, comparison and research. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a cross-sectional diagram of the ion imager design;

[0028] Figure 2 This is a schematic diagram of the flight time measurement principle based on gated high voltage;

[0029] Figure 3 It is a schematic diagram of the gated power supply operation;

[0030] Figure 4 It is a schematic block diagram of a low-level high-precision detection device based on gated high voltage of a field effect tube of the present invention;

[0031] Figure 5 yes Figure 4 Schematic diagram of level processing circuit;

[0032] Figure 6 yes Figure 4 ADC conversion circuit schematic diagram;

[0033] Figure 7 yes Figure 4 The circuit schematic diagram of the data processing unit;

[0034] Figure 8 It is an input and output waveform diagram of the low-level high-precision detection device based on the gated high voltage of the field effect tube of the present invention. DETAILED DESCRIPTION

[0035] The present invention discloses a low-level high-precision detection device based on gated high voltage of field effect tube, comprising: a level processing circuit, an ADC conversion circuit and a data processing unit, wherein:

[0036] The level processing circuit is implemented based on field effect transistors and is used to filter the high voltage part of the input gated high voltage and output only low voltage;

[0037] The ADC conversion circuit is used to periodically output the gated high voltage level data after analog-to-digital conversion at a set frequency under the control of the data processing unit;

[0038] The data processing unit is implemented based on FPGA (Field-Programmable Gate Array), which is used to control the ADC (Analog to Digital Converter) conversion circuit, collect the level data output by the ADC conversion circuit, and package it and output it to the PC through the RS422 driver circuit.

[0039] The technical solution of the present invention is described in detail below with reference to the accompanying drawings and embodiments.

[0040] Example

[0041] The embodiment of the present invention provides a low-level high-precision detection device based on gated high voltage of a field effect tube. Figure 4 This is a schematic block diagram of a low-level high-precision detection device for gated high voltage based on field effect transistors. The detection device includes a level processing circuit, an ADC conversion circuit, and a data processing unit. Its analog input is the gated high voltage, and its output is the low-voltage part of the processed gated high voltage. An oscilloscope can be used for measurement, and it has an RS422 interface to package and output the collected data.

[0042] like Figure 5 The figure shows the principle diagram of the level processing circuit of the low-level high-precision detection device based on the gated high voltage of the field effect tube. In the present invention, the high-level value of the input gated high voltage is +300V, and the low-level value is 0V. GND represents grounding. In one embodiment, the specification model of the key component field effect tube is RCS7464ET2, and the breakdown voltage of the field effect tube is V DSThe gate voltage is 500V. Due to the charging and discharging of parasitic capacitance in the gate-controlled high-voltage circuit, the gate-controlled high voltage will overshoot at the moment of opening the gate, which will damage the components in the gate-controlled high-voltage circuit and affect the service life of the components. This overshoot phenomenon can be eliminated by debugging the resistance and capacitance matching in the circuit, but it is necessary to be able to measure the level stabilization process after the high and low level switching with high precision.

[0043] like Figure 6 , Figure 7 The figure shows the ADC conversion circuit schematic diagram and the data processing unit circuit schematic diagram of the low-level high-precision detection device based on the gated high voltage of the field effect tube. In one embodiment, the ADC converter adopts AD976, a 16-bit high-precision ADC converter, and the interface signals between the ADC converter and the data processing unit FPGA include: ADC data bus, ADC chip selection signal, ADC conversion enable flag signal, and ADC conversion completion flag signal. In one embodiment, the data processing unit FPGA in the device controls the ADC to periodically collect the analog level curve output by the level processing circuit at a frequency of 100kHz, and packages the collected data to the PC end through the RS422 interface, and stores the gated high voltage high-low level switching process and the low-level stable state data on the PC end, which can be used for later data analysis and comparison.

[0044] like Figure 8 As shown in the figure, the input-output voltage waveform of the level processing circuit has an input voltage range of 0~+300V and an output voltage range of 0~+3V. The maximum output voltage is +3V. The output end is connected to the ADC conversion circuit in the device, and the external analog output is also led out. An oscilloscope can be used for high-precision measurement. The output voltage of this device is 0~+3V, which is within the safe voltage range for the human body, and there is no safety problem for the tester.

[0045] By using the device of the present invention to detect the output of the gated high voltage, the low-level stabilization process, low-level amplitude, and low-level holding time after the high-low level switching can be measured with high precision, and the overshoot phenomenon can be effectively avoided by adjusting the relevant resistance-capacitance matching state in the gated high voltage circuit. The accurate measurement of the low-level amplitude and low-level holding time can effectively ensure the high-precision measurement of flux control and mass spectrometry instruments.

[0046] The present invention overcomes the problem of low measurement accuracy of high-low level switching of gated high voltage, avoids the direct measurement of high voltage by oscilloscope test leads, and can effectively prevent the risk of high voltage discharge. The present invention utilizes the on-off characteristics of field effect tubes to design a gated high voltage level measurement circuit, filters the high voltage part of the gated high voltage, and outputs only low voltage. After using the invention, the oscilloscope measurement range is reduced from 300V to 3V, and the measurement accuracy is increased from 50V / div to 0.5V / div. The specific performance indicators are shown in Table 1:

[0047] Table 1

[0048]

[0049] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the embodiments, it should be understood by those skilled in the art that any modification or equivalent replacement of the technical solutions of the present invention does not depart from the spirit and scope of the technical solutions of the present invention and should be included in the scope of the claims of the present invention.

Claims

1. A low-level high-precision detection device based on gated high voltage of field effect tube, characterized in that: include: Level processing circuit, ADC conversion circuit and data processing unit, wherein, The level processing circuit is implemented based on a field effect transistor and is used to filter the high voltage part of the input gated high voltage and output only a low voltage; The ADC conversion circuit is used to periodically output the gated high voltage level data after analog-to-digital conversion at a set frequency under the control of the data processing unit; The data processing unit is implemented based on FPGA, and is used to control the ADC conversion circuit, collect the level data output by the ADC conversion circuit, and package and output it to the PC end through the RS422 interface.

2. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 1 is characterized in that: The high level value of the input gated high voltage is +300V, and the low level value is 0V.

3. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 1, characterized in that: In the level processing circuit, the breakdown voltage V DS is 500V, the gate-source turn-on threshold voltage V GS Greater than 2V, the gate-source can withstand a rated voltage range of ±20V, the gate voltage V G Fixed at 5V, source voltage V S In the range of 0V~3V, the drain source DS is turned on, and the source voltage V S When the voltage is greater than 3V, the drain-source DS of the field effect tube is cut off.

4. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 1, characterized in that: The ADC conversion circuit adopts a 16-bit high-precision ADC converter.

5. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 1, characterized in that: The data processing unit includes FPGA and RSS422 driving circuit, wherein: The FPGA controls the ADC conversion circuit to periodically collect the level data output by the level processing circuit at a frequency of 100kHz and transmit it to the RS422 drive circuit; The RS422 driving circuit converts the level data from a single-ended signal to a differential signal and outputs it to the PC end.

6. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 5, characterized in that: The interface signals between the ADC conversion circuit and the FPGA include: an ADC data bus, an ADC chip selection signal, an ADC conversion enable flag signal, and an ADC conversion completion flag signal.

7. The low-level high-precision detection device based on gated high voltage of field effect tube according to claim 5, characterized in that: The PC end stores the high-low level switching process of the gated high voltage and the data of the low-level stable state for later data analysis and comparison.

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