Hot cathode ionization gauge filament driving circuit and driving method

Abstract

The invention discloses a hot cathode ionization gauge filament driving circuit and a driving method, and relates to the technical field of vacuum measurement. The driving circuit comprises a vacuum gauge MCU, a DA chip, a power amplifier, a filament transformer and a filament voltage feedback circuit. The vacuum gauge MCU outputs a digital signal, the digital signal is converted into an analog voltage signal through the DA chip, and the analog voltage signal is amplified by the power amplifier and converted by the filament transformer to supply power to the filament; meanwhile, the filament voltage feedback circuit samples filament emission current and converts the filament emission current into a voltage feedback signal, the vacuum gauge MCU adjusts the effective time of the SW signal according to the voltage feedback signal, the on-off state of the power amplifier is controlled, and closed-loop control is achieved. The scheme does not need a large AC transformer, is high in integration level, retains AC driving, prolongs the service life of the filament, can accurately adjust the heating efficiency, and is suitable for various high-precision thermionic cathode ionization vacuum gauges.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of vacuum measurement, in particular to a hot cathode ionization gauge filament driving circuit and a driving method. BACKGROUND

[0002] The hot cathode ionization vacuum gauge is a core sensor for realizing high-precision vacuum degree measurement in a vacuum gauge. Its working principle is that electrons are emitted by heating a cathode (filament), the electrons collide with gas molecules in the gauge tube under the acceleration of an electric field and ionize the gas molecules, and the gas pressure is inversely deduced by measuring the ion current generated by ionization. Therefore, the stability and service life of the filament directly determine the measurement accuracy and reliability of the vacuum gauge.

[0003] At present, the filament driving circuits widely used in ZJ-10, ZJ-12, ZJ-27 and other types of hot cathode ionization vacuum gauges are mainly divided into direct current driving and traditional alternating current driving. The direct current driving usually adopts a switching power supply scheme, which has the advantages of high circuit integration and no need for an alternating current transformer, so that the overall size and weight of the machine are small. However, since the direction of direct current is constant, long-term operation will cause the filament material to be locally thinned, aged or even broken due to the electric migration effect, which seriously affects the measurement accuracy, and its service life is significantly shorter than that of the alternating current driving mode.

[0004] The traditional alternating current driving utilizes the periodic change of the current direction, which can effectively suppress the electric migration of the filament material, thereby greatly prolonging the service life of the filament and reducing the maintenance cost. However, its disadvantage is also obvious: the driving circuit needs to rely on a transformer with a large size and weight, resulting in low overall integration and large space occupation of the vacuum gauge, which is not conducive to the miniaturization and portability design of the equipment. SUMMARY

[0005] The present application provides a hot cathode ionization gauge filament driving circuit and a driving method to solve the technical problems of short service life of the existing direct current driven filament, low integration and large size of the traditional alternating current driven filament.

[0006] The present application is achieved by the following technical solutions:

[0007] In a first aspect of the present application, a filament driving circuit of a hot cathode ionization gauge is provided, comprising:

[0008] a vacuum gauge MCU for outputting a digital signal;

[0009] a DA chip for converting the digital signal output by the vacuum gauge MCU into an analog voltage signal;

[0010] a power amplifier for amplifying the analog voltage signal;

[0011] a filament transformer, a primary winding of which is connected to an output terminal of the power amplifier, and a secondary winding of which is connected to a filament of the hot cathode ionization gauge, for converting the amplified analog voltage signal and supplying power to the filament;

[0012] a filament voltage feedback circuit, for sampling an emission current of the filament and converting the emission current into a voltage feedback signal input to the vacuum gauge MCU;

[0013] the vacuum gauge MCU is further configured to output a SW signal to a switch pin of the power amplifier according to the voltage feedback signal, so as to control a switching state of the power amplifier and realize closed-loop control of filament heating efficiency.

[0014] Further, the vacuum gauge MCU is further configured to compare the voltage feedback signal with a preset value, and adjust an effective time of the SW signal in each control period according to a comparison result, so as to control a conduction time of the power amplifier in the control period.

[0015] The control period is consistent with a half-wave period of the analog voltage signal.

[0016] Further, the vacuum gauge MCU outputs the SW signal to the switch pin of the power amplifier through an IO port.

[0017] When the output SW signal is high, the power amplifier is turned on to amplify the analog voltage signal.

[0018] When the output SW signal is low, the power amplifier is turned off to stop outputting.

[0019] Further, the vacuum gauge MCU includes a first timer and a pre-stored digital sequence array.

[0020] The first timer interrupts at a first fixed period.

[0021] The vacuum gauge MCU is configured to read a value in the digital sequence array and output the value to the DA chip at each interruption of the first timer.

[0022] Further, the digital sequence array includes 50 values, which correspond to values of respective points of each segment of a complete sine wave divided by time.

[0023] The first fixed period is 400us, so that the DA chip outputs a 50Hz sine wave analog voltage signal.

[0024] Further, the vacuum gauge MCU further includes a second timer and a third timer.

[0025] The second timer interrupts at a second fixed period, and each interruption marks the beginning of a control period;

[0026] The third timer starts when the second timer interrupts, and its timing interval is adjustable in the range of 0 to the length of each control period.

[0027] The vacuum gauge MCU is configured to control the SW signal to be high during the timing interval of the third timer and to be low when the timing interval ends, so as to control the on-time of the power amplifier in each control period.

[0028] Further, the timing interval is determined according to the difference between the voltage feedback signal and the preset value.

[0029] Further, the filament voltage feedback circuit comprises a current sampling circuit and a optocoupler.

[0030] The current sampling circuit is connected to the filament for sampling the emission current of the filament and converting it into a voltage feedback signal input to the optocoupler.

[0031] The optocoupler inputs the voltage feedback signal after isolation and buffering to the vacuum gauge MCU.

[0032] Further, the output end of the optocoupler is connected to the built-in or externally connected ADC module of the vacuum gauge MCU, so as to convert the voltage feedback signal into a digital signal through the ADC module.

[0033] In the second aspect of the present application, a driving method of a hot cathode ionization gauge filament is provided, comprising:

[0034] The DA chip outputs an analog voltage signal controlled by the vacuum gauge MCU.

[0035] The power amplifier amplifies the analog voltage signal and drives the filament through the filament transformer.

[0036] The filament voltage feedback circuit samples the emission current of the filament and converts it into a voltage feedback signal input to the vacuum gauge MCU.

[0037] The vacuum gauge MCU compares the voltage feedback signal with a preset value, adjusts the effective time of the SW signal input to the switch pin of the power amplifier, controls the switching state of the power amplifier, and realizes closed-loop adjustment of the heating efficiency of the filament.

[0038] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0039] The driving scheme of the present application synthesizes an alternating excitation signal through digital control technology and introduces a closed-loop feedback regulation mechanism, thereby realizing accurate and stable control of the filament heating efficiency without an alternating transformer, ensuring long service life of the filament and significantly improving the integration and reliability of the driving circuit. BRIEF DESCRIPTION OF DRAWINGS

[0040] In order to more clearly illustrate the technical solutions of the exemplary embodiments of the present application, the drawings used in the embodiments will be briefly introduced as follows, and it should be understood that the following drawings only show some embodiments of the present application and therefore should not be considered as a limitation on the scope, and other related drawings can also be obtained by those skilled in the art without creative effort. In the drawings:

[0041] Figure 1 is a whole structure diagram of a hot cathode ionization gauge filament driving circuit according to an embodiment of the present application;

[0042] Figure 2 is a DA chip circuit principle diagram of a driving circuit according to an embodiment of the present application;

[0043] Figure 3 is a sine wave diagram output by a DA chip according to an embodiment of the present application;

[0044] Figure 4 is a power amplifier circuit principle diagram of a driving circuit according to an embodiment of the present application;

[0045] Figure 5 is a circuit principle diagram of a filament transformer of a driving circuit according to an embodiment of the present application;

[0046] Figure 6 is a circuit principle diagram of a filament voltage feedback circuit according to an embodiment of the present application;

[0047] Figure 7A is a comparison diagram of a SW signal and an output voltage waveform according to an embodiment of the present application;

[0048] Figure 7B is another comparison diagram of a SW signal and an output voltage waveform according to an embodiment of the present application. DETAILED DESCRIPTION

[0049] In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application will be further described in detail below with reference to the embodiments and drawings, and the exemplary embodiments of the present application and the description thereof are only used to explain the present application and should not be considered as a limitation on the present application.

[0050] It should be noted that the terms "include" and "have" and any variations thereof in the specification and in the claims of the present application and the above-mentioned drawings are intended to cover the non-exclusive inclusion, for example, a process, method, system, product or device including a series of steps or units does not have to be limited to or inherent to other steps or units.

[0051] The terms used in various embodiments of the present application are only for the purpose of describing specific embodiments and are not intended to limit various embodiments of the present application. As used herein, the singular form is intended to include the plural form, unless the context clearly indicates otherwise. Unless otherwise defined, all terms used herein, including technical terms and scientific terms, have the same meaning as commonly understood by those of ordinary skill in the art to which various embodiments of the present application belong. The terms (such as those defined in a commonly used dictionary) will be interpreted to have the same meaning as the contextual meaning in the relevant technical field and will not be interpreted to have an idealized meaning or an overly formal meaning, unless clearly defined in various embodiments of the present application.

[0052] The present application aims to solve the technical problems of short DC driving life in existing hot cathode ionization gauge filament driving, low integration and large volume in traditional AC driving, and proposes a digital AC driving circuit and method. It generates a sine wave through a vacuum gauge MCU controlling a DA chip, amplifies it through a power amplifier, converts it to power the filament after a filament transformer, and realizes closed-loop regulation with a feedback circuit, suitable for ZJ-10, ZJ-12, ZJ-27 and other models of hot cathode ionization vacuum gauges, which is conducive to improving the integration, stability and service life of vacuum measurement equipment, and is suitable for small, high-precision vacuum measurement scenarios.

[0053] Please refer to Figure 1 The hot cathode ionization gauge filament driving circuit proposed by the present application comprises: a vacuum gauge MCU, a DA chip, a power amplifier, a filament transformer and a filament voltage feedback circuit, and the connection relationship and functions of each component are as follows.

[0054] The vacuum gauge MCU is the control core of the driving circuit, which communicates with the DA chip through the SPI interface, outputs digital signals to the DA chip, connects the general IO port with the switch pin of the power amplifier, outputs the SW signal to control the working state of the power amplifier, and connects the built-in or external ADC module with the output end of the filament voltage feedback circuit to receive the voltage feedback signal.

[0055] Please refer to Figure 2 , Figure 2It is a circuit schematic of a DA chip. The DA chip U1 adopts internal reference voltage design, and its signal input end (pins 1, 2, and 3) is connected with the SPI signal lines (CLK, DIN, and CSDA) of the vacuum gauge MCU respectively, receives digital signals, and the signal output end Out (pin 7) is connected with the signal input end of the power amplifier, so as to convert the digital signal output by the vacuum gauge MCU into an analog voltage signal.

[0056] The DA chip U1 adopts a high-precision chip, such as Figure 2 As shown in the figure, the DA chip U1 is externally connected with a +5V working power supply, so as to provide stable power supply for the chip. The capacitor C1 (0.1uF) and the capacitor C2 (10uF) are power filter capacitors, C1 is used for filtering high-frequency interference, C2 is used for filtering low-frequency ripple, and they are used together to guarantee the stability of the working voltage of the DA chip and improve the output precision of the analog signal. Pin 6 is connected with an internal 2.048V reference voltage, and the DAout is the voltage value range of pin 7, which is 0~4095, and the output value is (DAout / 4096) x 2 x 4.096V. The vacuum gauge MCU generates a 50Hz sine wave through its own timer and the DA chip U1, and the amplitude is 4.096V, and the output formula is , wherein, y represents the amplitude, t represents the time.

[0057] Further, the vacuum gauge MCU includes a first timer time0 and a digital sequence array Cvalues.

[0058] In order to generate a sine wave, the vacuum gauge MCU internally pre-stores a digital sequence array Cvalues, which stores the digital amplitude code (range 0-1023, corresponding to 10-bit resolution) of 64 equal points in a period of the sine wave. The vacuum gauge MCU outputs the value in the array Cvalues to the DA chip in sequence according to the interrupt period of the first timer Timer0.

[0059] The first timer time0 interrupts at a first fixed period, and the vacuum gauge MCU reads a value (digital amplitude code) in the array Cvalues in sequence at each interruption, and sends it to the DA chip through the SPI bus. In this way, the output end of the DA chip generates a continuous and smooth sine wave voltage, and the waveform is as shown in the figure. Figure 3 .

[0060] Preferably, the Cvalues is set to include 50 values, each value is the amplitude value of each point after a complete sine wave is divided into 50 parts by time; and the first fixed period is set to 400 microseconds, so that the DA chip outputs a 50Hz sine wave analog voltage signal.

[0061] The first timer time0 is configured to generate an interrupt once every 400 microseconds. In the interrupt service program of the timer time0, the vacuum gauge MCU sequentially takes a value from the array Cvalues, sends it to the DA chip through the SPI bus, and after all the values in the array Cvalues are read out, a continuous and smooth 50Hz sine wave voltage is generated at the output end of the DA chip.

[0062] The power amplifier in the driving circuit adopts a high-precision high-voltage large-current power amplifier, which is used for high-precision, high-voltage and large-current amplification processing of the analog voltage signal, and controls the output state according to the SW signal.

[0063] Figure 4 The circuit schematic of a power amplifier U2 is shown, the signal input end (pin 1) is connected to the output end Out of the DA chip, the power supply end (pin 5) is connected to the adaptive working voltage, the switch pin (pin 7) is connected to the general IO port of the vacuum gauge MCU to receive the SW signal, and the output end (pin 6) is connected to one end of the primary winding of the filament transformer (the other end of the primary winding is grounded), so that the analog voltage signal is amplified and applied to the primary winding of the filament transformer.

[0064] The pins 2 and 3 of the power amplifier U2 are bias adjustment pins, which are connected to the ground through external resistors to set the static working point and avoid signal distortion; the capacitor C3 is an input coupling capacitor, which is used to isolate the direct current component and only transmit the alternating sine wave signal output by the DA chip U1; the clamping diodes D1 and D2 are arranged at the output end to prevent the output end voltage from damaging the chip; and the output filter capacitor C7 is arranged at the output end to smooth the amplified signal waveform, reduce the interference of spurious waves, and ensure the stability of the signal output to the filament transformer.

[0065] Figure 5 The circuit schematic of the filament transformer B1 is shown, one end of the primary winding of the filament transformer B1 is connected to the output end of the power amplifier, and the other end is grounded, and the two ends of the secondary winding are connected to the two ends of the filament of the hot cathode ion gauge, realizing voltage conversion and electrical isolation. It is used to convert the amplified analog voltage signal output by the power amplifier into a voltage suitable for the operation of the filament, and to supply power to the filament. The HV end is connected to the amplified high-voltage signal output by the power amplifier, which provides heating voltage for the filament.

[0066] One end of the filament voltage feedback circuit in the driving circuit is connected to the output end of the filament, and the signal output end is connected to the ADC input end of the vacuum gauge MCU, which is used to sample the emission current of the filament in real time and convert it into a voltage feedback signal, and input the voltage feedback signal into the vacuum gauge MCU. The vacuum gauge MCU controls the effective duration of the SW signal according to the voltage feedback signal, outputs the SW signal to the switch pin of the power amplifier, controls the switch state of the power amplifier, and realizes closed-loop control of the heating efficiency of the filament.

[0067] Figure 6 The circuit diagram of a filament voltage feedback circuit is shown, which includes a current sampling circuit and a Schmitt trigger U3. The current sampling circuit is composed of resistors R1, R2, RD and RC, R1 and R2 are connected to both ends of the filament, and the emission current of the filament flows through RD and RC to the ground through R1 and R2. By connecting a precise sampling resistor RC in series on the current return path of the filament, the emission current generates a voltage drop Vsample on RC, which converts the collection of emission current into a sampling voltage signal Vsample. Vsample is sent into the vacuum gauge MCU through the isolation and buffering effect of Schmitt trigger U3, and the voltage feedback signal ADin is sent into the vacuum gauge MCU.

[0068] The vacuum gauge MCU converts the analog voltage feedback signal into a digital quantity through the built-in or externally connected ADC module, and compares it with the preset value.

[0069] Further, the vacuum gauge MCU compares the digital quantity of the voltage feedback signal with the preset value, and adjusts the effective time of the SW signal in each control period according to the comparison result, so as to control the on-off time of the power amplifier in the control period through the SW signal.

[0070] The input end of the power amplifier receives a sine wave signal from the DA chip, which is controlled by the switch of the SW signal. When the SW signal is effective, the power amplifier is turned on, and when the SW signal is ineffective, the power amplifier is turned off. By adjusting the effective time of the SW signal, the conduction angle of the sine wave is adjusted, the driving voltage output to the filament is changed, the heating efficiency of the hot cathode ionization vacuum gauge is adjusted, and finally the emission current reaches the target value, realizing closed-loop control.

[0071] Specifically, the control period of the SW signal is set to be consistent with the half-wave period of the analog voltage signal. According to the difference between the voltage feedback signal and the preset value, the effective time of the SW signal is adjusted in each control period. For example, when the voltage feedback signal is less than the preset value Vset, it indicates that the filament emission current is too small, and the timing duration can be extended to prolong the effective time of the SW signal and increase the on-off time of the power amplifier, so as to improve the heating efficiency of the filament; when the voltage feedback signal is greater than the preset value Vset, it indicates that the emission current is too large, and the timing duration can be shortened to reduce the heating efficiency, so that the voltage feedback signal is finally stabilized around Vset, and the emission current reaches stability.

[0072] Further, the vacuum gauge MCU further includes a second timer Time1 and a third timer Time2. The second timer Time1 interrupts at a second fixed period, and each interruption marks the beginning of a control period; the third timer Time2 is started when the second timer interrupts, and its timing interval is adjustable in the range of 0 to the length of each control period.

[0073] To achieve power control synchronized with the sine wave, the vacuum gauge MCU enables a second timer (Timer1) and a third timer (Timer2). The second timer (Timer1) interrupts with a second fixed period, each interrupt marking the start of a control cycle. This second fixed period can be set to half the sine wave period; for example, if the sine wave frequency is 50Hz, the second fixed period would be set to 10ms. The third timer (Timer2) starts when the second timer (Timer1) is interrupted, and its timing interval is adjustable from 0 to the duration of each control cycle, i.e., adjustable from 0 to the half-wave period.

[0074] During the timing interval of the third timer (Timer2), the vacuum gauge MCU outputs a high-level SW signal, which then goes low at the end of the timing interval. When the SW signal is high, the power amplifier is turned on, amplifying the sinusoidal analog voltage signal output by the DA chip; when the SW signal is low, the power amplifier is turned off.

[0075] In this way, the voltage waveform actually applied to the filament transformer within each half-wave cycle is a segment of the original complete sine wave that has been truncated. For example... Figure 7A , 7B The figures show the voltage signals output by the power amplifier under the control of SW signals of different effective durations. The shaded area corresponds to the power amplifier being turned off, at which time the output voltage is 0.

[0076] When full-power heating is required, the timing duration of the third timer, Timer2, is set to 10ms, with the SW signal high throughout, and the power amplifier outputs a complete sine wave. When 50% power is required, the timing duration is set to 5ms, with the SW signal high for the first 5ms and low for the last 5ms, the power amplifier outputs the first half of a sine wave, and the output voltage is 0 for the last 5ms. The timing duration is adjustable within the range of 0 to half-wave period, enabling continuous and precise adjustment of the heating power from 0% to 100%.

[0077] The second timer, Timer1, is set to interrupt once every half-wave cycle, with the interrupt time synchronized with the zero-crossing point of the sine wave voltage, marking the start of the next power control cycle. Within the interrupt service routine of the second timer, Timer1, the vacuum gauge MCU starts the third timer, Timer2, to implement switching control for each control cycle.

[0078] Preferably, the timing interval of the third timer, Timer2, is determined based on the difference between the voltage feedback signal and a preset value. That is, during the entire closed-loop control process, before the filament's emission current stabilizes at the target value, the effective duration of the SW signal in each control cycle is determined based on this difference, allowing the emission current to stabilize more quickly.

[0079] Further, a proportional integral (PI) regulation algorithm can be used to optimize the regulation accuracy. For example, when the difference between the voltage feedback signal and the preset value is 80% of the maximum difference, the timing duration is set to 8 ms, i.e., the timing interval is 0-8 ms from the time when the second timer Timer1 interrupts; when the difference is 30% of the maximum difference, the timing duration is set to 3 ms, ensuring that the regulation process is fast and without overshoot.

[0080] Based on the same inventive concept, the application further provides a driving method for the hot cathode ionization gauge filament, which is applied to the driving circuit of any embodiment of the application.

[0081] S1, the vacuum gauge MCU controls the DA chip to output an analog voltage signal.

[0082] The vacuum gauge MCU controls the DA chip to continuously output a sine wave analog voltage signal with a fixed frequency and amplitude through its internal timer and pre-stored waveform array.

[0083] S2, the power amplifier amplifies the analog voltage signal, and drives the filament through the filament transformer.

[0084] The output of the DA chip is amplified in voltage / current by the power amplifier, and is output to the primary winding of the filament transformer, is coupled through the secondary winding of the filament transformer, is converted into a driving voltage, and drives the filament of the hot cathode ionization gauge to heat.

[0085] S3, the filament voltage feedback circuit samples the emission current of the filament and converts it into a voltage feedback signal input to the vacuum gauge MCU.

[0086] The current sampling circuit of the filament voltage feedback circuit samples the current flowing through the filament in real time, and converts it into a voltage feedback signal sent to the vacuum gauge MCU through a voltage follower.

[0087] S4, the vacuum gauge MCU compares the voltage feedback signal with a preset value, and adjusts the effective time of the SW signal input to the switch pin of the power amplifier.

[0088] The vacuum gauge MCU compares the digital value of the received voltage feedback signal with the internal preset value, and calculates the deviation. According to the deviation, the MCU dynamically adjusts the effective time (high-level pulse width) of the SW signal output by it in each control period.

[0089] The SW signal controls the switching state of the power amplifier. When SW is high, the power amplifier works, and the complete or partial sine wave is amplified and sent to the filament; when SW is low, the power amplifier is turned off and stops outputting. By cyclically executing S1-S4, accurate and stable closed-loop regulation of the heating efficiency of the filament is realized, and the emission current is ensured to be constant.

[0090] The above embodiments are only the preferred embodiments of the present application, but the protection scope of the present application is not limited thereto, any person skilled in the art can easily think of the changes or replacements within the technical range disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the appended claims.

Claims

1. A driving circuit for a hot cathode ionization gauge filament, characterized in that, include: The vacuum gauge MCU is used to output digital signals. The DA chip is used to convert the digital signal output by the vacuum gauge MCU into an analog voltage signal; A power amplifier is used to amplify the analog voltage signal; The filament transformer has its primary winding connected to the output terminal of the power amplifier and its secondary winding connected to the filament of the hot cathode ionizer. It is used to convert the amplified analog voltage signal to power the filament. The filament voltage feedback circuit is used to sample the emission current of the filament and convert the emission current into a voltage feedback signal, which is then input to the vacuum gauge MCU. The vacuum gauge MCU is also used to output a SW signal to the switching pin of the power amplifier according to the voltage feedback signal, so as to control the switching state of the power amplifier and realize closed-loop control of the filament heating efficiency.

2. The hot cathode ionization gauge filament driving circuit according to claim 1, characterized in that, The vacuum gauge MCU is also used to compare the voltage feedback signal with a preset value, and adjust the effective time of the SW signal in each control cycle according to the comparison result, so as to control the conduction time of the power amplifier in the control cycle. The control period is consistent with the half-wave period of the analog voltage signal.

3. The hot cathode ionization gauge filament driving circuit according to claim 2, characterized in that, The vacuum gauge MCU outputs the SW signal to the switch pin of the power amplifier through the IO port; When the output SW signal is high, the power amplifier is turned on to amplify the analog voltage signal. When the output SW signal is low, the power amplifier turns off its output.

4. The hot cathode ionization gauge filament driving circuit according to claim 2, characterized in that, The vacuum gauge MCU includes a first timer and a pre-stored array of digital sequences; The first timer interrupts at a first fixed period; The vacuum gauge MCU is configured to read a value from the digital sequence array sequentially and output it to the DA chip during each interruption of the first timer.

5. The hot cathode ionization gauge filament driving circuit according to claim 4, characterized in that, The digital sequence array includes 50 values, each value corresponding to the amplitude value of a complete sine wave divided into equal parts over time. The first fixed period is 400µs, so that the DA chip outputs a 50Hz sinusoidal analog voltage signal.

6. The hot cathode ionization gauge filament driving circuit according to claim 2, characterized in that, The vacuum gauge MCU also includes a second timer and a third timer; The second timer interrupts at a second fixed period, with each interrupt marking the start of a control cycle; The third timer starts when the second timer is interrupted, and its timing interval is adjustable from 0 to the duration of each control cycle; The vacuum gauge MCU is configured to control the SW signal to be high during the timing interval of the third timer and low at the end of the timing interval, so as to control the conduction time of the power amplifier in each control cycle.

7. The hot cathode ionization gauge filament driving circuit according to claim 6, characterized in that, The timing interval is determined based on the difference between the voltage feedback signal and the preset value.

8. The hot cathode ionization gauge filament driving circuit according to claim 1, characterized in that, The filament voltage feedback circuit includes a current sampling circuit and an emitter follower; The current sampling circuit is connected to the filament and is used to sample the emission current of the filament and convert it into a voltage feedback signal for input to the emitter follower. The emitter follower isolates and buffers the voltage feedback signal before inputting it to the vacuum gauge MCU.

9. The hot cathode ionization gauge filament driving circuit according to claim 8, characterized in that, The output of the emitter follower is connected to the built-in or external ADC module of the vacuum gauge MCU to convert the voltage feedback signal into a digital signal through the ADC module.

10. A method for driving the filament of a hot cathode ionization gauge, characterized in that, The method, applied to the hot cathode ionization gauge filament driving circuit according to any one of claims 1-9, comprises: The DA chip outputs an analog voltage signal via the vacuum gauge MCU; The analog voltage signal is amplified by a power amplifier and then used to drive the filament via a filament transformer. The filament's emission current is sampled by the filament voltage feedback circuit and converted into a voltage feedback signal, which is then input to the vacuum gauge MCU. The vacuum gauge MCU compares the voltage feedback signal with a preset value and adjusts the effective time of the SW signal input to the switching pin of the power amplifier to control the switching state of the power amplifier and realize closed-loop regulation of the filament heating efficiency.

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