Constant controllable heating method for hot cathode

Abstract

The invention discloses a steady controllable heating method for a thermionic cathode, and relates to the technical field of thermionic cathode electron emission, and the method comprises the following steps: S1, signal acquisition and processing; s2, signal conversion; s3, negative feedback of the workflow; s4, collecting electric data at two ends of the hot cathode load; s5, adjusting a constant-temperature mode; and S6, constant current mode adjustment. Based on a negative feedback circuit composed of a triode, an amplifier and a feedback resistor, stable and accurate control over cathode heating current and heating temperature is achieved, the heating power supply can keep high precision and stability under different load resistance values, the precision and real-time control problems existing in traditional design are solved, and in addition, the heating power supply can be applied to a high-voltage power supply. The method also has the advantage of easy realization of computer end control, provides greater operation flexibility for the user, and improves the working efficiency and the operation convenience.

Description

Technical Field

[0001] The invention relates to the technical field of hot cathode electron emission, in particular to a stable and controllable heating method for a hot cathode. Background Art

[0002] As an important electron source, hot cathode is commonly used in various electron source devices and systems such as electron guns, vacuum electron tubes, X-ray tubes and emission probes. Among all hot cathode materials, refractory metal wires such as tungsten wire and rhenium wire are the most common and widely used materials. A very important problem in the practical application of this pure metal hot cathode is that it is usually accompanied by high thermal evaporation loss during operation, which leads to changes in hot cathode parameters such as hot cathode resistance, heating temperature and electron emission current. In almost all electronic source components with hot cathode as the core, there are usually very high requirements for the stability of electron emission. According to Rich From the Ardson-Dushman formula, it can be seen that the main factor affecting the hot cathode electron emission current is the heating temperature of the hot cathode. Therefore, it is of great significance to achieve stable control of the hot cathode heating temperature. In addition, in the use of emission probes made of ultra-fine hot cathode filaments (diameter is usually in the micron level), special attention is paid to the stable control of the heating current and heating temperature of the hot cathode. Different emission probe measurement methods almost all require that the heating current or heating temperature of the filament is maintained unchanged. Therefore, in the use of the emission probe device, the research and development of a power supply that can achieve stable and controllable heating current output is an indispensable link.

[0003] There have been many studies on controlling the heating current of the hot cathode by adopting different negative feedback principles. A traditional method is to use analog technology to drive the hot cathode controller, but this has many limitations. It is not accurate enough, difficult to adjust and calibrate, and does not support computer interface. Another solution is to use a personal computer, commercial digital-to-analog converter, analog-to-digital converter and programmable power supply, but this method is costly, bulky and slow to respond. Summary of the invention

[0004] The object of the present invention is to provide a stable and controllable heating method for a hot cathode to solve the problems raised in the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: a method for stable and controllable heating of a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module, the method comprising the following steps:

[0006] S1, signal acquisition and processing: The core controller module receives the control command and transmits the command to the DAC module, and collects the hot cathode load R 1The voltage signal and heating current signal on the sensor are transmitted to the ADC module, which converts the analog signal into a digital signal and displays it in real time on the LCD screen. At the same time, the core controller module processes the collected voltage signal and heating current signal.

[0007] S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal;

[0008] S3, negative feedback workflow: signal input terminal U of negative feedback current control module i Connected to the output of the DAC module, the output signal of the DAC module is converted into a hot cathode load R 1 The heating current, the signal output end of the negative feedback current control module is used to monitor the hot cathode load R 1 Signal collection point of working status;

[0009] S4. Collect the electrical data at both ends of the hot cathode load: The voltage / current acquisition module uses a common-phase proportional operation circuit to read the hot cathode load R 1 The voltage at both ends and the heating current of the hot cathode are collected;

[0010] S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode to ensure that the hot cathode operates stably at the set temperature;

[0011] S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

[0012] Preferably, in step S1, the core controller module communicates with the external device via a USB interface;

[0013] In the step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal.

[0014] Preferably, in step S3, the negative feedback current control module is composed of an amplifier, a triode and a feedback resistor R 2 The signal processed by the amplifier is input to the base of the transistor, and the collector of the transistor is connected to the hot cathode load R 1 , the emitter of the transistor is connected to a feedback resistor R 2, the signal input terminal U in the negative feedback current control module i Connected to the output of the DAC module, the data output by the DAC module is converted into a hot cathode load R 1 The heating current is located at the collector and emitter of the transistor, and the two signal output terminals are the first output terminal U o1 and the second output terminal U o2 , as monitoring hot cathode load R 1 The signal collection point of the working state, the two input terminals of the amplifier include the input terminal U i and the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is from the input terminal U i With the feedback resistor R 2 The ratio is determined by changing the input terminal U i Change the current flowing through the feedback resistor R 2 The current, hot cathode load R 1 The heating current changes accordingly.

[0015] Preferably, in step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal at the signal input terminal U i With the first output terminal U o1 Connect to read the hot cathode load R 1 The voltage at both ends of the signal input terminal U i With the second output terminal U o2 connected to collect the heating current of the hot cathode. At this time, the core controller module reads the feedback resistor R 2 The voltage across the hot cathode load R is calculated. 1 of heating current.

[0016] Preferably, step S5 comprises the following steps:

[0017] S501, input the set hot cathode heating temperature;

[0018] S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and the heating voltage;

[0019] S503. Check the changing relationship between the emissivity and the heating temperature of the hot cathode material, obtain the corresponding emissivity according to the set cathode heating temperature, calculate the real-time temperature of the hot cathode by using the collected heating current, heating voltage and emissivity through the Stefan-Boltzmann law, then compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the status of the hot cathode and adjust the output voltage of the DAC module.

[0020] Preferably, the step S5 further comprises the following steps:

[0021] S504, if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increasing the output voltage to heat the hot cathode;

[0022] S505, if the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reducing the output voltage to lower the temperature;

[0023] S506: If the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, the current output voltage is maintained.

[0024] Preferably, step S6 comprises the following steps:

[0025] S601, input the set hot cathode heating current;

[0026] S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current;

[0027] S603 , the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module.

[0028] Preferably, the step S6 further comprises the following steps:

[0029] S604, if the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current;

[0030] S605, if the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to reduce the current;

[0031] S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, the current output voltage is maintained.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] 1. The negative feedback circuit composed of a triode, an amplifier and a feedback resistor is based on the present invention, which realizes the steady and precise control of the hot cathode heating current and the heating temperature. The heating power supply can maintain high precision and stability under different load resistance values. The fluctuation value of the heating temperature is less than 0.1% of the set value, and the fluctuation value of the heating current is less than 0.2% of the set value, which solves the accuracy and real-time control problems existing in the traditional design. In addition, the design of the present invention also has the advantage of easy computer-side control, which provides users with greater operating flexibility and improves work efficiency and convenience of operation.

[0034] 2. The present invention automatically realizes stable control of hot cathode heating current and heating temperature through a software program on an external computer, and the entire control process and user experience are convenient and efficient;

[0035] 3. The present invention is not only applicable to filament-shaped hot cathodes and pure metal hot cathodes, but also to hot cathodes of other shapes and materials, and has wide applicability;

[0036] 4. The present invention can automatically calculate the hot cathode heating temperature based on the hot cathode heating current and heating voltage collected in real time. Therefore, the present invention is not only suitable for places where the hot cathode heating temperature can be directly measured, but also suitable for many places where direct measurement of the hot cathode heating temperature cannot be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A schematic diagram of the overall method flow provided by an embodiment of the present invention;

[0038] Figure 2 A schematic flow chart of a method for adjusting a constant temperature mode provided by an embodiment of the present invention;

[0039] Figure 3 A schematic flow chart of a method for regulating a constant current mode provided by an embodiment of the present invention;

[0040] Figure 4 A software program flowchart of a constant temperature mode provided by an embodiment of the present invention;

[0041] Figure 5 A constant current mode software program flowchart provided by an embodiment of the present invention;

[0042] Figure 6 A schematic diagram of the hardware structure of a steady heating power supply provided in an embodiment of the present invention;

[0043] Figure 7 A schematic diagram of a negative feedback output circuit in a constant heating power supply provided by an embodiment of the present invention;

[0044] Figure 8 A schematic diagram of a same-direction proportional operation circuit in a constant heating power supply provided by an embodiment of the present invention;

[0045] Fig. 9 A schematic diagram of the test results of the heating temperature output of the heating power supply provided by the embodiment of the present invention under different load resistances;

[0046] Fig.10 A schematic diagram of the test results of the heating current output of the heating power supply provided by an embodiment of the present invention under different load resistances. DETAILED DESCRIPTION

[0047] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0048] See also Figures 1 to 10 The present invention provides a technical solution: a method for a stable and controllable heating of a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module, the method comprising the following steps:

[0049] S1, signal acquisition and processing: The core controller module receives the control command and transmits the command to the DAC module, and collects the hot cathode load R 1 The voltage signal and heating current signal on the sensor are transmitted to the ADC module, which converts the analog signal into a digital signal and displays it in real time on the LCD screen. At the same time, the core controller module processes the collected voltage signal and heating current signal.

[0050] S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal;

[0051] S3, negative feedback workflow: signal input terminal U of negative feedback current control module i Connected to the output of the DAC module, the output signal of the DAC module is converted into a hot cathode load R 1 The heating current, the signal output end of the negative feedback current control module is used to monitor the hot cathode load R 1 Signal collection point of working status;

[0052] S4. Collect the electrical data at both ends of the hot cathode load: The voltage / current acquisition module uses a common-phase proportional operation circuit to read the hot cathode load R 1 The voltage at both ends and the heating current of the hot cathode are collected;

[0053] S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode to ensure that the hot cathode operates stably at the set temperature;

[0054] S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

[0055] In step S1, the core controller module communicates with the external device via the USB interface;

[0056] In step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal;

[0057] In step S3, the negative feedback current control module is composed of an amplifier, a transistor and a feedback resistor R 2 The signal processed by the amplifier is input to the base of the transistor, and the collector of the transistor is connected to the hot cathode load R 1 , the emitter of the transistor is connected to a feedback resistor R 2 , the signal input terminal U in the negative feedback current control module i Connected to the output of the DAC module, the data output by the DAC module is converted into a hot cathode load R 1 The heating current is located at the collector and emitter of the transistor, and the two signal output terminals are the first output terminal U o1 and the second output terminal U o2 , as monitoring hot cathode load R 1 The signal collection point of the working state, the two input terminals of the amplifier include the input terminal U i and the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is from the input terminal U i With the feedback resistor R 2 The ratio is determined by changing the input terminal U i Change the current flowing through the feedback resistor R 2 The current, hot cathode load R 1 The heating current changes accordingly;

[0058] In step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal to the signal input terminal U i With the first output terminal U o1 Connect to read the hot cathode load R 1 The voltage at both ends of the signal input terminal U i With the second output terminal U o2 connected to collect the heating current of the hot cathode. At this time, the core controller module reads the feedback resistor R 2 The voltage across the hot cathode load R is calculated. 1 Heating current;

[0059] Step S5 includes the following steps:

[0060] S501, input the set hot cathode heating temperature;

[0061] S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and the heating voltage;

[0062] S503, according to the material of the hot cathode, the relationship between the radiation coefficient and the heating temperature is checked, and the corresponding radiation coefficient is obtained according to the set cathode heating temperature. The real-time temperature of the hot cathode is calculated by using the collected heating current, heating voltage and radiation coefficient through the Stefan-Boltzmann law, and then the set hot cathode heating temperature and the real-time temperature of the hot cathode are compared, and the state of the hot cathode is continuously monitored and the output voltage of the DAC module is adjusted;

[0063] The calculation formula using the Stefan-Boltzmann law is:

[0064] U ht I ht =SξσT 4

[0065] Where U ht is the heating voltage of the hot cathode, I ht is the heating current of the hot cathode, S is the entire surface area of ​​the hot cathode, ξ is the radiation coefficient, and σ is the Stefan-Boltzmann constant, which is equal to 5.67*10 -8 Wm -2 K -4 , T is the operating temperature of the hot cathode;

[0066] Step S5 also includes the following steps:

[0067] S504, if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increasing the output voltage to heat the hot cathode;

[0068] S505, if the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reducing the output voltage to lower the temperature;

[0069] S506, if the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, maintain the current output voltage;

[0070] The constant temperature mode adjustment is applicable to the electron source equipment whose relationship with the hot cathode is known and the heating temperature cannot be directly measured. When the heating temperature of the hot cathode can be directly measured, the set temperature can be directly compared with the real-time temperature to control the heating current of the hot cathode;

[0071] As the resistance of the filament load increases successively, the filament load resistance shows a good step-like increasing trend. The temperature will also jump after the resistance jumps, but it will quickly return to the set value. The circuit has a fast response and small delay. When the circuit is working stably, the filament working temperature hardly changes with time. In the test, the temperature fluctuation is less than 0.1% of the temperature setting value, which shows the high precision and reliability of the output temperature of the stable and controllable heating power supply.

[0072] Step S6 includes the following steps:

[0073] S601, input the set hot cathode heating current;

[0074] S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current;

[0075] S603, the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module;

[0076] Step S6 also includes the following steps:

[0077] S604, if the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current;

[0078] S605, if the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to reduce the current;

[0079] S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, maintain the current output voltage;

[0080] As the resistance of the filament load increases successively, the voltage across the filament load shows a good step-like increasing trend. The circuit responds quickly and has a small delay. When the circuit is working stably, the filament voltage hardly changes over time. In addition, changes in the resistance of the filament load do not change the measured heating current of the filament. In the test, the current fluctuation is less than 0.2% of the current setting value, which shows the high precision and reliability of the output current of the stable and controllable heating power supply.

[0081] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0082] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A stable and controllable heating method for a hot cathode, comprising a core controller module, a DAC module, a negative feedback current control module, and a voltage / current acquisition module, characterized in that: The method comprises the following steps: S1, signal acquisition and processing: the core controller module receives the control instruction and transmits the instruction to the DAC module, and transmits the voltage signal and heating current signal collected on the hot cathode load R1 to the ADC module. The ADC module converts the analog signal into a digital signal and displays it in real time on the LCD display. At the same time, the core controller module performs data processing on the collected voltage signal and heating current signal; S2, signal conversion: The DAC module converts the digital signal processed and output by the core controller module into a continuous analog voltage or analog current signal; S3, negative feedback workflow: signal input terminal U of negative feedback current control module i Connected to the output end of the DAC module, the signal output by the DAC module is converted into the heating current of the hot cathode load R1. The signal output end of the negative feedback current control module is the signal collection point for monitoring the working state of the hot cathode load R1. S4, collecting electrical data at both ends of the hot cathode load: the voltage / current acquisition module adopts a common-phase proportional operation circuit to read the voltage at both ends of the hot cathode load R1 and collect the heating current of the hot cathode; S5, constant temperature mode adjustment: compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the state of the hot cathode and adjust the output voltage until the real-time temperature of the hot cathode is the same as the set hot cathode heating temperature, and finally output the hot cathode heating temperature. This value is used to monitor the working state of the hot cathode to ensure that the hot cathode operates stably at the set temperature; S6. Constant current mode adjustment: The core controller module monitors and collects the hot cathode heating current in real time through the voltage / current acquisition module, and compares it with the set hot cathode heating current. By adjusting the voltage, the real-time hot cathode heating current and the set hot cathode heating current are kept at the same value, and finally the hot cathode is maintained in the set working state.

2. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: In the step S1, the core controller module communicates with the external device via the USB interface; In the step S2, the DAC module converts the digital signal into a continuous analog voltage or analog current signal.

3. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: In step S3, the negative feedback current control module is composed of an amplifier, a transistor and a feedback resistor R2. The signal processed by the amplifier is input to the base of the transistor. The collector of the transistor is connected to the hot cathode load R1, and the emitter of the transistor is connected to the feedback resistor R2. The signal input terminal U i Connected to the output end of the DAC module, the data output by the DAC module is converted into the heating current of the hot cathode load R1. The two signal output ends located at the collector and emitter of the triode are respectively the first output end U o1 and the second output terminal U o2 , as a signal collection point for monitoring the working state of the hot cathode load R1, the two input terminals of the amplifier include the input terminal U i and the second output terminal U connected to the emitter of the transistor o2 When the transistor is in the on state, the emitter current of the transistor is from the input terminal U i The ratio of the feedback resistor R2 is determined by changing the input terminal U i By changing the current flowing through the feedback resistor R2, the heating current of the hot cathode load R1 changes accordingly.

4. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: In step S4, the voltage / current acquisition module uses an in-phase proportional operation circuit to input the signal at the signal input terminal U i With the first output terminal U o1 Connect to read the voltage across the hot cathode load R1 and input the signal to the U i With the second output terminal U o2 The core controller module reads the voltage across the feedback resistor R2 to calculate the heating current flowing through the hot cathode load R1.

5. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: The step S5 comprises the following steps: S501, input the set hot cathode heating temperature; S502, then outputting a voltage signal through the DAC module to heat the hot cathode, and monitoring the current state of the hot cathode by collecting the heating current and the heating voltage; S503. Check the changing relationship between the emissivity and the heating temperature of the hot cathode material, obtain the corresponding emissivity according to the set cathode heating temperature, calculate the real-time temperature of the hot cathode by using the collected heating current, heating voltage and emissivity through the Stefan-Boltzmann law, then compare the set hot cathode heating temperature and the real-time temperature of the hot cathode, and continuously monitor the status of the hot cathode and adjust the output voltage of the DAC module.

6. A method for controlling the heating of a hot cathode according to claim 5, characterized in that: The step S5 further comprises the following steps: S504, if the set hot cathode heating temperature is lower than the real-time temperature of the hot cathode, increasing the output voltage to heat the hot cathode; S505, if the set hot cathode heating temperature is greater than the real-time temperature of the hot cathode, reducing the output voltage to lower the temperature; S506: If the set hot cathode heating temperature is equal to the real-time temperature of the hot cathode, the current output voltage is maintained.

7. A method for controlling the heating of a hot cathode according to claim 1, characterized in that: The step S6 comprises the following steps: S601, input the set hot cathode heating current; S602, the core controller module controls the DAC module to output an initial voltage signal to obtain a real-time hot cathode heating current; S603 , the core controller module compares the real-time hot cathode heating current with the set hot cathode heating current, and dynamically adjusts the output voltage of the DAC module.

8. A method for controlling the heating of a hot cathode according to claim 7, characterized in that: The step S6 further comprises the following steps: S604, if the real-time hot cathode heating current is less than the set hot cathode heating current, the output voltage is automatically increased to increase the current; S605, if the real-time hot cathode heating current is greater than the set hot cathode heating current, the output voltage is automatically reduced to reduce the current; S606: If the real-time hot cathode heating current is equal to the set hot cathode heating current, the current output voltage is maintained.

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