Pressure detection circuit of semiconductor process gas path and gas flow measurement system

Abstract

Embodiments of the present application disclose a pressure detection circuit of a semiconductor process gas path and a gas flow measurement system. The pressure detection circuit comprises a signal inversion circuit, a controller, a digital-to-analog conversion circuit, an amplitude clipping circuit and an analog-to-digital conversion circuit. The signal inversion circuit is configured to invert a pressure detection signal to obtain an inverted detection signal. The digital-to-analog conversion circuit is configured to output a target direct current bias signal based on a direct current bias value. The amplitude clipping circuit is configured to perform an amplitude clipping operation on the inverted detection signal according to the target direct current bias signal to obtain a pressure characteristic signal. The analog-to-digital conversion circuit is configured to transmit the characteristic digital signal to the controller, so that the controller restores the pressure detection signal based on the characteristic digital signal and a digital signal corresponding to the target direct current bias signal. Embodiments of the present application do not need to attenuate the original pressure detection signal as a whole to avoid being overwhelmed by noise, still obtain an accurate and reliable pressure detection signal, and completely retain the high resolution of the pressure sensor.

Description

Technical Field

[0001] This application relates to the field of gas flow measurement technology, specifically to a pressure detection circuit and a gas flow measurement system for a semiconductor process gas path. Background Technology

[0002] In semiconductor fields such as chip manufacturing, high-precision gas mass flow rate measurement based on the pressure rise method requires high-resolution, large dynamic range pressure sensors. These sensors can achieve a full-scale output of up to 10V and can resolve minute pressure changes as low as 1 mTorr. To ensure the pressure sensor's output signal is compatible with the input range of a small-range analog-to-digital converter (ADC), related technologies employ a fixed attenuation scheme, proportionally attenuating the pressure detection signal before sampling. While this achieves range matching, it attenuates the minute effective signal below the ADC's noise floor, resulting in a severely degraded signal-to-noise ratio. The effective signal is overwhelmed by noise, leading to low measurement accuracy. Summary of the Invention

[0003] To address the aforementioned technical problems, embodiments of this application provide a pressure detection circuit and a gas flow measurement system for a semiconductor process gas path, thereby improving the low measurement accuracy of related technologies.

[0004] In a first aspect, embodiments of this application provide a pressure detection circuit for a semiconductor process gas path, comprising: a signal inversion circuit, a controller, a digital-to-analog converter circuit, an amplitude clipping circuit, and an analog-to-digital converter circuit. The signal inversion circuit is configured to acquire a pressure detection signal transmitted by a pressure sensor, and invert the pressure detection signal to obtain an inverted detection signal. The controller is configured to output a DC bias command, the DC bias command including a DC bias value. The digital-to-analog converter circuit is electrically connected to the controller and configured to output a target DC bias signal based on the DC bias value in response to the DC bias command. The amplitude clipping circuit is electrically connected to both the signal inversion circuit and the digital-to-analog converter circuit and configured to perform an amplitude clipping operation on the inverted detection signal according to the target DC bias signal to obtain a pressure characteristic signal. The analog-to-digital converter circuit is electrically connected to both the amplitude clipping circuit and the controller and configured to perform analog-to-digital conversion processing on the pressure characteristic signal to obtain a characteristic digital signal, and transmit the characteristic digital signal to the controller so that the controller can restore the pressure detection signal in digital form based on the characteristic digital signal and the digital signal corresponding to the target DC bias signal to obtain a digital detection signal.

[0005] Optionally, the analog-to-digital conversion circuit is configured with an analog input range, and the controller is configured to output a DC bias command, including: acquiring a target digital signal, wherein the target digital signal is used to limit the amplitude of any pressure characteristic signal to always remain within the analog input range; determining the target error at the current sampling time based on the target digital signal and the characteristic digital signal; performing PID adjustment operation on the target error at the current sampling time based on a preset PID algorithm to obtain a DC bias value; and generating a DC bias command based on the DC bias value.

[0006] Optionally, the target digital signal is the digital signal corresponding to the midpoint voltage of the analog input range; and / or, based on the target digital signal and the characteristic digital signal, the target error at the current sampling time is determined, including: subtracting the target digital signal from the characteristic digital signal to obtain the target error at the current sampling time.

[0007] Optionally, the digital-to-analog conversion circuit includes: a digital-to-analog conversion chip and a gain amplifier circuit. The digital-to-analog conversion chip is configured to output an analog bias signal based on a DC bias value in response to a DC bias command. The gain amplifier circuit is electrically connected to the digital-to-analog conversion chip and is configured to amplify the analog bias signal based on a preset gain amplification factor to obtain a target DC bias signal.

[0008] Optionally, the digital-to-analog converter chip is configured to output an analog bias signal based on a DC bias value in response to a DC bias command, including: parsing a DC bias value from the DC bias command in response to the DC bias command; acquiring historical bias values, where the historical bias value is the digital signal corresponding to the DC bias signal at the previous sampling time, and the sampling time of the DC bias signal at the previous sampling time is arranged in the time sequence before and adjacent to the sampling time of the target DC bias signal; determining the target signal amplitude based on the DC bias value and the historical bias value; and outputting an analog bias signal according to the target signal amplitude.

[0009] Optionally, the pressure sensor is configured with a voltage sampling range, the product of the gain amplification factor and the voltage amplitude of the maximum analog bias signal is greater than or equal to the maximum value of the voltage sampling range; and / or, the signal inversion circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a first operational amplifier, a pressure detection signal is applied to the first terminal of the first resistor, the second terminal of the first resistor is electrically connected to the first terminal of the second resistor and the inverting input terminal of the first operational amplifier, the second terminal of the second resistor is electrically connected to the output terminal of the first operational amplifier, the first terminal of the third resistor is grounded, the second terminal of the third resistor is electrically connected to the first terminal of the fourth resistor and the non-inverting input terminal of the first operational amplifier, and a pressure detection signal is applied to the second terminal of the fourth resistor; the gain amplification circuit includes a fifth resistor, a sixth resistor, and a second operational amplifier, a first terminal of the fifth resistor is grounded, the second terminal of the fifth resistor is electrically connected to the first terminal of the sixth resistor and the inverting input terminal of the second operational amplifier, the second terminal of the sixth resistor is electrically connected to the output terminal of the second operational amplifier, and the non-inverting input terminal of the second operational amplifier is electrically connected to the output terminal of the digital-to-analog converter chip.

[0010] Optionally, the amplitude clipping circuit includes a comparator circuit and a bias circuit. The comparator circuit is electrically connected to the signal inversion circuit and the digital-to-analog converter circuit, respectively, and is configured to add the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result. The amplitude clipping result is then inverted and scaled according to a preset first scaling factor to obtain an initial scaled signal. The bias circuit is electrically connected to the comparator circuit and the analog-to-digital converter circuit, respectively, and is configured to receive a reference voltage. The initial scaled signal is then scaled according to a preset second scaling factor to obtain a secondary scaled signal. Under the action of the reference voltage, the secondary scaled signal is shifted upward according to a preset voltage amplitude to obtain a pressure characteristic signal. The preset voltage amplitude is used to raise the secondary scaled signal when it is less than a minimum voltage threshold to ensure that the pressure characteristic signal falls within the analog input range of the analog-to-digital converter circuit.

[0011] Optionally, the comparator circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a third operational amplifier. The first terminal of the seventh resistor is grounded, and the second terminal of the seventh resistor is electrically connected to the non-inverting input terminal of the third operational amplifier. The inverting input terminal of the third operational amplifier is electrically connected to the first terminals of the eighth, ninth, and tenth resistors, respectively. The second terminal of the eighth resistor is electrically connected to the output terminal of the signal inverting circuit. The second terminal of the tenth resistor is electrically connected to the digital-to-analog converter circuit, and the second terminal of the ninth resistor is electrically connected to the output terminal of the third operational amplifier. The bias circuit includes an eleventh resistor and a twelfth resistor. The first terminal of the eleventh resistor is electrically connected to the output terminal of the third operational amplifier, and the second terminal of the eleventh resistor is electrically connected to the first terminal of the twelfth resistor and the analog-to-digital converter circuit, respectively. A reference voltage is applied to the second terminal of the twelfth resistor.

[0012] Optionally, the amplitude clipping circuit is configured with an overall scaling factor. The controller, based on the characteristic digital signal and the digital signal corresponding to the target DC bias signal, restores the pressure detection signal in digital form to obtain a digital detection signal. This includes: performing a downward level shift on the characteristic digital signal according to a preset voltage amplitude to obtain a level shift result; dividing the level shift result by the overall scaling factor to obtain an initial result; adding the target DC bias signal to the initial result to obtain a digital voltage amplitude; and restoring the pressure detection signal in digital form based on the digital voltage amplitude to obtain a digital detection signal.

[0013] In a second aspect, embodiments of this application provide a gas flow measurement system, including the pressure detection circuit described above.

[0014] The beneficial effects of the pressure detection circuit provided in this application embodiment are as follows: The pressure detection circuit provided in this application embodiment cancels and clips the amplitude of the inverted detection signal using a dynamic target DC bias signal to obtain the pressure characteristic signal of interest. This eliminates the need for overall attenuation of the original pressure detection signal, and the pressure characteristic signal is not compressed due to overall attenuation, thus avoiding the pressure characteristic signal being easily overwhelmed by the local noise of the analog-to-digital conversion circuit. Simultaneously, the pressure characteristic signal has a small amplitude but can completely reflect the characteristics of the pressure detection signal changing over time. Based on the pressure characteristic signal, the analog-to-digital conversion circuit reliably and accurately outputs a digital characteristic signal reflecting the changes in the pressure detection signal. Then, the controller accurately and reliably reconstructs the pressure detection signal in digital form using the characteristic digital signal and the digital signal corresponding to the target DC bias signal. Therefore, this application embodiment does not require overall attenuation of the original pressure detection signal to avoid being overwhelmed by noise, and can still obtain an accurate and reliable pressure detection signal, avoiding the signal-to-noise ratio degradation caused by fixed attenuation, and fully preserving the high resolution and large dynamic range advantages of the pressure sensor. Attached Figure Description

[0015] One or more embodiments are illustrated by way of example with reference numerals in the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements with the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0016] Figure 1 This is a schematic diagram of the structure of a butterfly valve provided in an embodiment of this application; Figure 2 A schematic diagram of the circuit structure of a pressure detection circuit provided in an embodiment of this application; Figure 3 Control loop diagram of the pressure detection circuit provided in the embodiments of this application; Figure 4 for Figure 2 The circuit diagram shown is of the signal inversion circuit. Figure 5 Control loop diagram of a pressure detection circuit provided in another embodiment of this application; Figure 6 for Figure 5 The circuit structure diagram of the gain amplifier circuit shown is shown. Figure 7 A control loop diagram of a pressure detection circuit provided in another embodiment of this application; Figure 8 for Figure 7 The circuit structure diagram of the comparator circuit shown is as follows; Figure 9 A schematic diagram of the circuit structure of a pressure detection circuit provided in another embodiment of this application; Figure 10 A waveform diagram of the original pressure detection signal output by the pressure sensor provided in the embodiments of this application; Figure 11 A waveform diagram of the target DC bias signal output by the digital-to-analog converter circuit provided in the embodiments of this application; Figure 12 The waveform of the pressure characteristic signal fed into the digital-to-analog converter circuit provided in the embodiment of this application. Detailed Implementation

[0017] To facilitate understanding of this application, a more detailed description is provided below with reference to the accompanying drawings and specific embodiments. It should be noted that when an element is described as being "fixed to" another element, it can be directly on the other element, or one or more intermediate elements may exist between them. When an element is described as being "electrically connected" to another element, it can be directly connected to the other element, or one or more intermediate elements may exist between them. The terms "upper," "lower," "inner," "outer," "bottom," etc., used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Furthermore, the terms "first," "second," "third," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the scope of the application. The term "and / or" as used in this specification includes any and all combinations of one or more of the associated listed items. Furthermore, technical features involved in the different embodiments of this application described below may be combined with each other as long as they do not conflict with each other.

[0019] In fields such as chip manufacturing, vacuum equipment, and precision gas flow control, gas flow measurement systems are commonly used to measure gas flow. A gas flow measurement system includes valves and pressure sensors. Valves control the flow of gas, while pressure sensors detect the pressure generated by the gas within a closed cavity. These components, combined with gas flow measurement methods, control the valve's closed and open states, and then measure the pressure using the pressure signal sampled by the pressure sensor.

[0020] Butterfly valves are typically chosen as the type of valve. Due to their compact structure, fast opening and closing speed, and high conductivity (low obstruction to gas flow), butterfly valves are widely used for isolating atmospheric and ultra-high vacuum environments, isolating the load locking chamber from the main vacuum system, isolating the chamber from the pump, or switching between roughing / high vacuum pumps. The sealing performance and reliability of the butterfly valve are crucial, ensuring the stability of the main system's vacuum level and preventing frequent exposure to the atmosphere.

[0021] Butterfly valves feature a robust design that reduces maintenance and makes up for it more convenient. The butterfly principle combined with a compact actuator design allows for successful installation even in spaces with limited capacity. The valve body and internal mechanisms utilize special coatings and materials (such as nickel alloys and special stainless steel), and even offer perfluoroelastomer rubber seals. Butterfly valves possess excellent corrosion resistance and extremely high sealing performance, capable of withstanding plasma and strong fluorine / chlorine-based chemicals for extended periods, resulting in an exceptionally long service life and reduced downtime for maintenance. Furthermore, they ensure that corrosive gases never leak and prevent external air infiltration, a vital safeguard for process purity.

[0022] Please see Figure 1 The stepper motor 11 can change the opening of the butterfly valve 12, so that the opening of the butterfly valve 12 can be precisely stopped at the corresponding angle, and the flow rate of special process gas can be precisely controlled, thereby precisely controlling the pressure in the chamber. This is crucial for the uniformity of thin film deposition and the consistency of etching rate.

[0023] Gas flow rate is typically measured using the pressure rise method (RoR method). The pressure rise method involves filling a sealed cavity of known volume with the gas to be measured, monitoring the rate of pressure rise within the cavity in real time, and calculating the mass flow rate using the gas state equation. It is a high-precision, traceable absolute measurement method with stringent requirements for the accuracy of pressure signal acquisition, dynamic range, and response speed.

[0024] To meet the measurement requirements of the pressure rise method, the system typically employs a high-resolution, large dynamic range pressure sensor. A typical pressure sensor has a resolution of 0.001% FS, a dynamic range of up to 100 dB, and a full-scale output voltage of 10 V, enabling the detection of minute pressure changes as low as 1 mTorr. The output of this type of pressure sensor includes a large DC baseline component and a minute pressure change component at the μV level. The minute pressure change component directly determines the measurement accuracy of the mass flow rate and is the core effective signal of the system.

[0025] To convert the pressure sensor's output pressure detection signal into a digital signal for processing, the system needs to be equipped with a high-resolution Σ-Δ analog-to-digital converter (ADC). These ADCs are 24-bit, typically with a range of ±1V or 0-1.25V, and a peak-to-peak noise floor of approximately 100μV. The pressure sensor's range is 0V-10V; therefore, the pressure sensor's range is much wider than the ADC's. Common technologies employ a front-end fixed-resistor voltage divider network to attenuate the pressure detection signal by a fixed attenuation factor, such as 10. This compresses the pressure sensor's full-scale 10V to 1V, thus adapting it to the 0-1.25V range of the ADC without clipping.

[0026] However, this related technology has inherent technical defects: the minimum resolvable pressure of the pressure sensor is 1 mTorr, and the output voltage corresponding to the minimum resolvable pressure is about 100 μV. After a fixed attenuation of 10 times, it is only 10 μV. This amplitude is far lower than the background peak-to-peak noise of the analog-to-digital converter of 100 μV, which causes the effective signal to be completely submerged by noise and the signal-to-noise ratio of the system to be severely degraded.

[0027] In low-flow-rate measurements using the pressure rise method, the pressure rise rate is slow, and the effective signal is weak. To obtain a usable differential pressure signal, the inflation time must be significantly extended, and a large amount of data must be averaged, resulting in extremely low measurement efficiency and severely insufficient response speed. The core of the pressure rise method is to inversely calculate the flow rate through the pressure rise rate. However, the essence of low-flow-rate measurement is to capture small, slow pressure changes. For example, at low flow rates, the pressure rise rate is extremely slow. After the small pressure rise signal (such as 1 mTorr or 10 mTorr) is submerged by noise, to obtain a usable pressure rise rate, the inflation time needs to be extended so that the pressure accumulates to an order of magnitude that can be covered by the noise. What could have been a measurement in a few seconds now takes several minutes or tens of minutes, and then dozens or even hundreds of measurements need to be averaged. This increases the pressure measurement time and reduces measurement efficiency.

[0028] Meanwhile, the controlled flow rate fluctuates in real time under actual working conditions, requiring the detection system to have a rapid capture capability. However, the fixed attenuation scheme cannot meet the rapid detection requirements due to the deterioration of the signal-to-noise ratio, and the performance advantages of the high-precision pressure sensor cannot be fully utilized. Ultimately, this limits the measurement accuracy and stability of the pressure rise method measurement system in scenarios with small flow, high dynamics, and fast response.

[0029] The pressure detection circuit for the semiconductor process gas path provided in this application embodiment is applied to a gas flow measurement system to acquire pressure detection signals. During the gas flow measurement process, the pipeline volume of the gas flow measurement system itself needs to be calibrated first. This application embodiment utilizes the gas flow measurement system, combined with the pressure detection signal acquired by the pressure sensor, and employs a pressure rise method to calibrate the pipeline volume of the gas flow measurement system itself.

[0030] Please see Figure 2 The pressure detection circuit 200 of the semiconductor process gas path includes a signal inversion circuit 21, a controller 22, a digital-to-analog converter (DAC) 23, an amplitude clipping circuit 24, and an analog-to-digital converter 25.

[0031] The signal inverting circuit 21 is used to acquire the pressure detection signal transmitted by the pressure sensor 26, and invert the pressure detection signal to obtain an inverted detection signal. For example, the pressure sensor 26 collects the pressure in the pipeline space of the gas flow measurement system to obtain an analog pressure detection signal. Pressure detection signal The voltage amplitude is 5V, and the pressure sensor 26 will transmit the pressure detection signal. Input signal inverting circuit 21, signal inverting circuit 21 for pressure detection signal Inverting the signal yields a -5V inverted detection signal. .

[0032] Controller 22 outputs a DC bias command, which includes a DC bias value. The DC bias command instructs the digital-to-analog converter (DAC) 23 to adjust its output according to the DC bias value. The DC bias value is... The DC bias value can be dynamically generated by the controller 22 according to a preset PID algorithm. Then, controller 22 based on DC bias value A DC bias command is generated and sent to the digital-to-analog converter circuit 23. The DC bias value is specified in the provided text. The value is dynamically changing. At certain times, the controller 22 outputs the DC bias value based on the PID algorithm. It equals 0. At certain times, the DC bias value output by controller 22 according to the PID algorithm is... Greater than 0. At certain times, the controller 22 outputs the DC bias value based on the PID algorithm. Less than 0.

[0033] The digital-to-analog converter circuit 23 is electrically connected to the controller 22 and is used to output a target DC bias signal based on the DC bias value in response to a DC bias command. The target DC bias signal is a signal that cancels out the large DC component contained in the inverting detection signal in order to retain a smaller effective change component.

[0034] When the digital-to-analog converter 23 receives the DC bias command sent by the controller 22, the digital-to-analog converter 23 parses the DC bias command and obtains the DC bias value. Based on DC bias value The voltage amplitude of the target DC bias signal is obtained, and the digital-to-analog converter 23 outputs the target DC bias signal in analog form according to the voltage amplitude.

[0035] In some embodiments, provided that the pressure sampling range of the pressure sensor 26 is consistent with the range of the digital-to-analog converter 23, or provided that the pressure sampling range of the pressure sensor 26 is smaller than the range of the digital-to-analog converter 23, the digital-to-analog converter 23 can convert the DC bias value... Compared with historical bias By adding them together, we obtain the target signal amplitude in digital form. ,Right now: Among them, historical bias value The sampling time of the DC bias signal at the previous sampling time (k-1) is arranged in the time series before and adjacent to the sampling time (k) of the target DC bias signal. The digital-to-analog converter 23 calculates the target signal amplitude... Output target DC bias signal in analog form .

[0036] Understandably, the target DC bias signal is in analog form. In this context, "t" represents continuous time; therefore, the target DC bias signal in analog form... The signal is continuous. The target signal amplitude is in digital form. In this context, "k" represents the sequence number of the discrete sequence; therefore, the target signal amplitude in digital form... It is a discrete signal.

[0037] In other embodiments, provided that the pressure sampling range of the pressure sensor 26 is greater than the range of the digital-to-analog converter 23, the digital-to-analog converter 23 can convert the DC bias value... Compared with historical bias By adding them together, we obtain the target signal amplitude in digital form. Then, the target signal amplitude The target DC bias signal is obtained by amplifying the signal with a gain amplification factor of 'a'. .

[0038] The amplitude clipping circuit 24 is electrically connected to the signal inversion circuit 21 and the digital-to-analog converter circuit 23, respectively. It is used to perform an amplitude clipping operation on the inverted detection signal according to the voltage amplitude of the target DC bias signal to obtain the pressure characteristic signal. The pressure characteristic signal is the effective change component remaining after the target DC bias signal cancels out the large DC component contained in the inverted detection signal. It is used to represent the characteristic change of the pressure detection signal over time.

[0039] In some embodiments, provided that the voltage amplitude of the maximum pressure characteristic signal is less than or equal to the maximum value of the analog input range of the analog-to-digital converter circuit 25, the amplitude clipping circuit 24 adds the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result, and then inverts the amplitude clipping result to obtain the pressure characteristic signal. It is understood that the pressure characteristic signal is an analog signal, representing a value over continuous time; therefore, the embodiments of this application employ... This represents the pressure characteristic signal.

[0040] For example, pressure characteristic signal .in, This is a pressure characteristic signal. The target DC bias signal, This is a pressure detection signal. This is an inverted detection signal. This is the amplitude clipping result. For example, according to engineering experience, the voltage amplitude of the maximum pressure characteristic signal is 1V. When the analog input range of the analog-to-digital converter circuit 25 is [0, 1.25], the maximum value of the analog input range is 1.25, which is greater than the maximum pressure characteristic signal.

[0041] In this embodiment of the application, the pressure sensor can collect pressure detection signals of any value in any working environment. There is no need to scale the pressure characteristic signal output by the amplitude clipping circuit 24. The pressure characteristic signal output by the amplitude clipping circuit 24 can be mapped to the analog-to-digital sampling space of the analog-to-digital conversion circuit 25. That is, since the voltage amplitude of the maximum pressure characteristic signal is less than or equal to the maximum value of the analog input range of the analog-to-digital conversion circuit 25, the analog-to-digital conversion circuit 25 can sample the corresponding analog signal for any output of the pressure sensor and convert the analog signal into a digital signal. There will be no situation where the output of the pressure sensor exceeds the upper limit condition and the analog-to-digital conversion circuit 25 fails to sample the output.

[0042] In other embodiments, when the voltage amplitude of the maximum pressure characteristic signal is greater than the maximum value of the analog input range of the analog-to-digital converter circuit 25, the amplitude clipping circuit 24 is configured with an overall scaling factor. The amplitude clipping circuit 24 adds the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result, and then performs inverted scaling on the amplitude clipping result according to the overall scaling factor to obtain the pressure characteristic signal. For example, the pressure characteristic signal... .in, This is the overall scaling factor. This is the result of amplitude clipping.

[0043] For example, the voltage amplitude of the maximum pressure characteristic signal is 5. When the analog input range of the analog-to-digital converter 25 is [0, 1.25], the maximum value of the analog input range is 1.25, which is less than the maximum pressure characteristic signal. If the pressure characteristic signal output by the amplitude clipping circuit 24 is not scaled, the pressure characteristic signal output by the amplitude clipping circuit 24 may exceed the analog input range of the analog-to-digital converter 25, resulting in amplitude clipping and distortion of the sampled values ​​of the analog-to-digital converter 25.

[0044] For example, after amplitude clipping, the pressure characteristic signal obtained without scaling is 1.5. The amplitude clipping circuit 24 calculates the overall scaling factor. After scaling the pressure characteristic signal, the scaled pressure characteristic signal is 0.375. As another example, after amplitude clipping, the unscaled pressure characteristic signal is 4.0. The amplitude clipping circuit 24 calculates the overall scaling factor. After scaling the pressure characteristic signal, the scaled pressure characteristic signal is 1.0.

[0045] When a pressure sensor is subjected to any working environment and collects a pressure detection signal of any value, this embodiment of the application performs scaling processing on the pressure feature signal output by the amplitude clipping circuit 24, so that the scaled pressure feature signal can be mapped to the analog-to-digital sampling space of the analog-to-digital conversion circuit 25. This can improve the environmental compatibility of the pressure sensor and ensure that the analog-to-digital conversion circuit 25 can sample reliable and accurate sampling values ​​in any working environment.

[0046] In other embodiments, the amplitude clipping circuit 24, after obtaining the amplitude clipping result, can further perform an upward level shift on the amplitude clipping result to obtain a pressure characteristic signal. For example, the amplitude clipping circuit 24 adds the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result, and then performs an inverted scaling process on the amplitude clipping result according to the overall scaling factor to obtain a secondary scaled signal. Under the action of the reference voltage, the secondary scaled signal is shifted upward according to a preset voltage amplitude to obtain the pressure characteristic signal. The upward level shift process refers to shifting the secondary scaled signal according to a preset voltage amplitude, such that the voltage difference between the shifted secondary scaled signal and the original secondary scaled signal is equal to the preset voltage amplitude.

[0047] For example, a double-scaled signal .in, This is the overall scaling factor. For the amplitude clipping result, This is a double-scaled signal. Under the influence of the reference voltage, it scales according to a preset voltage amplitude. The pressure characteristic signal is obtained by performing an up-level shift on the quadratic scaling signal, for example... , This is the preset voltage amplitude.

[0048] The analog-to-digital converter circuit 25 is electrically connected to the amplitude clipping circuit 24 and the controller 22, respectively. It performs analog-to-digital conversion on the pressure characteristic signal to obtain a characteristic digital signal. This characteristic digital signal is then transmitted to the controller 22, which, based on the characteristic digital signal and the digital signal corresponding to the target DC bias signal, digitally reconstructs the pressure detection signal to obtain a digital detection signal. The digital detection signal is the digital signal corresponding to the analog pressure detection signal.

[0049] It is understood that the characteristic digital signal is the digital signal sampled by the analog-to-digital converter 25, representing a value in discrete space. Therefore, the embodiments of this application adopt... It represents a characteristic digital signal.

[0050] The digital-to-analog converter (DAC) 23 and analog-to-digital converter (ADC) 25 are single-supply devices, supporting only unipolar voltage input and unable to withstand negative voltage. The pressure detection circuit 200 provided in this embodiment inverts the signal using a signal inversion circuit 21 and superimposes the voltage bias using an amplitude clipping circuit 24. This converts the potentially negative bipolar calculation result into a unipolar pressure characteristic signal, ensuring that the conditioned pressure characteristic signal perfectly matches the single-supply input range of the DAC 23 and ADC 25. This prevents damage to the DAC 23 and ADC 25 from negative voltage input, while simultaneously guaranteeing signal sampling linearity and system reliability.

[0051] In some embodiments, provided that the voltage amplitude of the maximum pressure characteristic signal is less than or equal to the maximum value of the analog input range of the analog-to-digital converter circuit 25, the controller 22 adds the target DC bias signal to the characteristic digital signal to obtain the addition result. Based on the addition result, the pressure detection signal is restored in digital form to obtain the digital detection signal. For example, the characteristic digital signal in digital form... Digital detection signal ,in, The digital signal corresponding to the target DC bias signal. For digital detection signals.

[0052] In other embodiments, provided that the voltage amplitude of the maximum pressure characteristic signal is greater than the maximum value of the analog input range of the analog-to-digital converter circuit 25, the amplitude clipping circuit 24 is configured with an overall scaling factor. The controller 22 divides the characteristic digital signal with the overall scaling factor to obtain the division result. The digital signal corresponding to the target DC bias signal is added to the division result to obtain the signal addition result. Based on the signal addition result, the pressure detection signal is restored in digital form to obtain the digital detection signal.

[0053] For example, the division result ,in, For the result of the division, For characteristic digital signals, This is the overall scaling factor. Digital detection signal. ,in, The digital signal corresponding to the target DC bias signal. For digital detection signals, This is the result of adding the signals.

[0054] In other embodiments, when the voltage amplitude of the maximum pressure characteristic signal is greater than the maximum value of the analog input range of the analog-to-digital converter circuit 25, the controller 22 performs a downward level shift on the characteristic digital signal according to a preset voltage amplitude to obtain a level shift result. The level shift result is divided by the overall scaling factor to obtain an initial result. The digital signal corresponding to the target DC bias signal is added to the initial result to obtain a digital voltage amplitude. Based on the digital voltage amplitude, the pressure detection signal is restored in digital form to obtain a digital detection signal. The downward level shift refers to shifting the characteristic digital signal according to a preset voltage amplitude, such that the voltage difference between the characteristic digital signal before and after the shift is equal to the preset voltage amplitude.

[0055] For example, , , , ,in, The digital signal corresponding to the target DC bias signal. This is the result of level shifting. As the initial result, For characteristic digital signals, This is the overall scaling factor. The signal is a digital detection signal, and w is the preset voltage amplitude.

[0056] The pressure detection circuit 200 provided in this embodiment cancels and clips the amplitude of the inverted detection signal using a dynamic target DC bias signal to obtain the pressure characteristic signal of interest. This eliminates the need for overall attenuation of the original pressure detection signal, and the pressure characteristic signal is not compressed due to overall attenuation, thus avoiding the pressure characteristic signal being easily overwhelmed by the local noise of the analog-to-digital converter circuit 25. Simultaneously, the pressure characteristic signal, though small in amplitude, fully reflects the characteristics of the pressure detection signal changing over time. Based on the pressure characteristic signal, the analog-to-digital converter circuit 25 reliably and accurately outputs a digital characteristic signal reflecting the changes in the pressure detection signal. Then, the controller 22 accurately and reliably reconstructs the pressure detection signal in digital form using the characteristic digital signal and the digital signal corresponding to the target DC bias signal. Therefore, this embodiment does not require overall attenuation of the original pressure detection signal to avoid being overwhelmed by noise, yet still obtains an accurate and reliable pressure detection signal, avoiding the signal-to-noise ratio degradation caused by fixed attenuation, and fully preserving the high resolution and large dynamic range advantages of the pressure sensor.

[0057] The pressure detection circuit 200 provided in this application embodiment can produce significant effects in gas flow measurement systems. For example, based on the pressure detection circuit 200 provided in this application embodiment, the pressure rise method does not need to extend the sampling time or increase the signal-to-noise ratio through multiple averaging, and can quickly capture transient pressure changes and flow rate fluctuations, meeting the real-time and speed requirements of high-precision gas flow measurement systems.

[0058] In high-precision gas flow measurement based on the pressure rise method, the pressure sensor output features a large dynamic range, a large DC baseline, and small effective variations. To achieve analog-to-digital conversion, related technologies typically attenuate the pressure detection signal directly before inputting it into the analog-to-digital converter circuit 25. This results in the pressure detection signal being randomly distributed within the range of the analog-to-digital converter circuit 25, frequently approaching the upper and lower limits of the range. Furthermore, the analog-to-digital converter circuit 25 is susceptible to nonlinearity, saturation distortion, and background noise in the upper and lower limit regions of the range, significantly reducing the usable effective resolution, especially making it unable to reliably identify minute pressure changes at the 1 mTorr level. Simultaneously, the anti-interference margin is insufficient when the pressure detection signal approaches the range boundary, and noise easily leads to clipping or quantization errors in the pressure detection signal, further degrading the system's measurement accuracy and response speed, failing to meet the requirements for low-flow-rate, high-dynamic-range measurements.

[0059] In some embodiments, the analog-to-digital converter circuit 25 is configured with an analog input range, and the controller 22 includes the following steps in the process of outputting a DC bias command: acquiring a target digital signal, determining the target error at the current sampling time based on the target digital signal and the characteristic digital signal, performing PID adjustment operation on the target error at the current sampling time based on a preset PID algorithm to obtain a DC bias value, and generating a DC bias command based on the DC bias value.

[0060] The target digital signal is used to limit the amplitude of any pressure characteristic signal to always remain within the analog input range. In some embodiments, the target digital signal is the digital signal corresponding to the midpoint voltage of the analog input range, where the resolution of the midpoint voltage within the analog input range is the vertical resolution. For example, the resolution of the analog-to-digital converter 25 is N, the analog input range is 0-Vref, the midpoint voltage is 0.5Vref, and the vertical resolution is... That is, the digital signal corresponding to the midpoint voltage is For example, when N is 24 and the analog input range is 0-1.25V, the midpoint voltage is 0.625V, and the corresponding digital signal is... .

[0061] In some embodiments, the target digital signal can be a digital signal corresponding to the value around the midpoint voltage or a signal customized by the designer based on engineering experience, as long as the amplitude of any pressure characteristic signal is always kept within the analog input range.

[0062] The controller 22 subtracts the target digital signal from the characteristic digital signal to obtain the target error at the current sampling time. For example, ,in, The target error at the current sampling time. For the target digital signal, It is a characteristic digital signal.

[0063] when This indicates that the current characteristic digital signal is less than the target digital signal, and the output of the digital-to-analog converter 23 needs to be adjusted to change the characteristic digital signal at the next sampling time, ensuring that the characteristic digital signal at any given time fluctuates slightly around the periphery of the target digital signal. This indicates that the current characteristic digital signal is greater than the target digital signal, and the output of the digital-to-analog converter 23 needs to be adjusted to change the characteristic digital signal at the next sampling time, so as to ensure that the characteristic digital signal at any time fluctuates slightly around the periphery of the target digital signal.

[0064] The controller 22 performs PID adjustment on the target error at the current sampling time based on a preset PID algorithm to obtain a DC bias value. Specifically, the controller 22 generates a proportional term based on a preset proportional coefficient and the target error at the current sampling time, integrates the target error from the initial sampling time to the current sampling time to obtain an integral value, generates an integral term based on a preset integral coefficient and the integral value, obtains the target error at the previous sampling time, calculates the error change rate based on the target error at the current sampling time, the target error at the previous sampling time, and a preset sampling interval, generates a differential term based on a preset differential coefficient and the error change rate, and generates a DC bias value based on the proportional term, integral term, and differential term.

[0065] Please see Figure 3 For example, the PID control loop is shown below:

[0066] in, This is the DC bias value. For the proportion term, For integration, For differential terms, This is the proportionality coefficient. The integral coefficient is... For error rate, The sampling interval is... The differential coefficients are... Let be the target error at the i-th sampling time, and k be the index of the current sampling time.

[0067] The proportional term is used to quickly adjust the output of the digital-to-analog converter circuit 23 according to the magnitude and direction of the target error at the current sampling time. The larger the target error, the larger the adjustment range. The integral term is used to eliminate steady-state error and ensure that the pressure characteristic signal is stable near the target digital signal. The derivative term is used to predict the error change trend, suppress fluctuations in the pressure characteristic signal, and avoid overshoot or oscillation during the adjustment process.

[0068] The pressure detection circuit 200 provided in this application embodiment stabilizes the pressure characteristic signal at the midpoint of the range of the analog-to-digital conversion circuit 25, so that the pressure characteristic signal is always in the working range with the highest vertical resolution, optimal linearity, and strongest anti-interference capability. This avoids resolution loss, noise overload, and quantization distortion caused by the pressure characteristic signal approaching the upper and lower limits of the range. Without attenuating the original pressure detection signal, it maximizes the detection accuracy and response speed of minute pressure changes.

[0069] Please see Figure 4 The signal inverting circuit 21 includes a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a first operational amplifier U1. A pressure detection signal is applied to the first terminal of the first resistor R1. The second terminal of the first resistor R1 is electrically connected to the first terminal of the second resistor R2 and the inverting input terminal of the first operational amplifier U1. The second terminal of the second resistor R2 is electrically connected to the output terminal of the first operational amplifier U1. The first terminal of the third resistor R3 is grounded. The second terminal of the third resistor R3 is electrically connected to the first terminal of the fourth resistor R4 and the non-inverting input terminal of the first operational amplifier U1. A pressure detection signal is applied to the second terminal of the fourth resistor R4. When the pressure detection signal is input to the signal inverting circuit 21 in differential form through the first resistor R1, the third resistor R3, and the fourth resistor R4, the signal inverting circuit 21 inverts the pressure detection signal to obtain an inverted detection signal.

[0070] Please see Figure 5 The digital-to-analog converter circuit 23 includes a digital-to-analog converter chip 231 and a gain amplifier circuit 232. The gain amplifier circuit 232 is electrically connected to the digital-to-analog converter chip 231.

[0071] The digital-to-analog converter chip 231 is used to output an analog bias signal based on a DC bias value in response to a DC bias command. The process of the digital-to-analog converter chip 231 outputting an analog bias signal based on a DC bias value in response to a DC bias command includes the following steps: in response to the DC bias command, parsing the DC bias value from the DC bias command, obtaining historical bias values, where the historical bias value is the digital signal corresponding to the DC bias signal at the previous sampling time, and the sampling time of the DC bias signal at the previous sampling time is arranged before and adjacent to the sampling time of the target DC bias signal in the time sequence; determining the target signal amplitude based on the DC bias value and the historical bias value; and outputting an analog bias signal according to the target signal amplitude.

[0072] For example, when the pressure sampling range of the pressure sensor 26 is greater than the range of the digital-to-analog converter circuit 23, the digital-to-analog converter chip 231 parses the DC bias value from the DC bias command. DC bias value Compared with historical bias Add them together to obtain the target signal amplitude. According to the target signal amplitude Output analog bias signal in analog form .

[0073] For example, suppose The target error at the current sampling time (Digital quantity), then the contribution of the proportional term is 0.1 × 100 = 10; if the integral and differential terms are temporarily ignored, the DC bias value Then the output of the digital-to-analog converter chip 231 is updated to This adjusts the amplitude clipping circuit 24, causing the pressure characteristic signal output by the amplitude clipping circuit 24 to shift towards the target digital signal.

[0074] The analog-to-digital converter chip 231 provided in this application uses incremental superposition of output DC bias values, enabling the analog bias voltage to be continuous, stable, and without abrupt changes, avoiding disturbances to the pressure detection signal and ensuring stable, glitch-free pressure characteristic signals. Simultaneously, this application embodiment uses historical bias values ​​for gradual correction, resulting in gentler bias adjustment without overshoot or oscillation, which helps improve the output stability of the target DC bias signal.

[0075] The gain amplifier circuit 232 amplifies the analog bias signal based on a preset gain amplification factor to obtain the target DC bias signal. For example, the gain amplifier circuit 232 amplifies the analog bias signal in analog form. The target DC bias signal is obtained by amplifying the signal with a gain amplification factor of 'a'. .

[0076] The pressure sensor is configured with a voltage sampling range, and the product of the gain amplification factor and the voltage amplitude of the maximum analog bias signal is greater than or equal to the maximum value of the voltage sampling range. ,in, For the maximum analog bias signal, The maximum value of the voltage sampling range is defined as the maximum analog bias signal, which is the full-scale analog bias signal output by the digital-to-analog converter chip 231. Thus, this embodiment ensures that within the full range of the pressure sensor (0V-10V), the target DC bias signal can effectively cancel and clip the amplitude of the pressure detection signal. Therefore, by amplifying the analog bias signal, this embodiment ensures that the target DC bias signal at any sampling time covers the full range of the pressure sensor, preventing the maximum target DC bias signal from being less than the maximum pressure detection signal. This helps ensure that the dynamic target DC bias signal has sufficient amplitude to completely cancel the static DC component of the pressure sensor within the full range, avoiding the inability to stabilize the pressure characteristic signal at the midpoint of the range of the analog-to-digital converter circuit 25 due to insufficient bias amplitude.

[0077] Finally, this embodiment of the application achieves incremental dynamic bias output by setting up a digital-to-analog converter chip 231 and a gain amplifier circuit 232, and amplifies the voltage amplitude of the target DC bias signal through the gain amplification factor. The amplification result can cover the full range of the pressure sensor, so that no matter what value of pressure detection signal is sampled, there is a corresponding target DC bias signal to provide sufficient amplitude, completely canceling the static DC component of the pressure sensor in the full range. In this way, the pressure characteristic signal can be reliably stabilized at the midpoint of the range of the analog-to-digital converter circuit 25, maximizing the use of the ADC vertical resolution, while ensuring smooth bias adjustment without overshoot or disturbance, and improving the accuracy, stability and anti-interference ability of pressure detection.

[0078] Please see Figure 6 The gain amplifier circuit 232 includes a fifth resistor R5, a sixth resistor R6, and a second operational amplifier U2. The first end of the fifth resistor R5 is grounded, the second end of the fifth resistor R5 is electrically connected to the first end of the sixth resistor R6 and the inverting input of the second operational amplifier U2, the second end of the sixth resistor R6 is electrically connected to the output of the second operational amplifier U2, and the non-inverting input of the second operational amplifier U2 is electrically connected to the output of the digital-to-analog converter chip 231.

[0079] The controller 22 sends a DC bias command to the digital-to-analog converter chip 231. The digital-to-analog converter chip 231 parses the DC bias value from the DC bias command, obtains historical bias values, determines the target signal amplitude based on the DC bias value and historical bias values, and outputs an analog bias signal to the gain amplifier circuit 232 according to the target signal amplitude. The gain amplifier circuit 232 amplifies the analog bias signal based on the gain amplification factor 'a' to obtain the target DC bias signal.

[0080] Please see Figure 7 The amplitude clipping circuit 24 includes a comparator circuit 241 and a bias circuit 242.

[0081] The comparator circuit 241 is electrically connected to the signal inversion circuit 21 and the digital-to-analog converter circuit 23, respectively. It is used to add and invert the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result. The amplitude clipping result is then inverted and scaled according to the preset first scaling factor to obtain the initial scaled signal.

[0082] For example, amplitude clipping results , This is the amplitude clipping result. Initial scaling signal. , The first scaling factor is... This is the initial scaling signal. Comparator circuit 241 uses the target DC bias signal. With inverted detection signal The signal is subjected to addition and inversion processing to cancel out the large DC component in the inverted detection signal, retaining only the amplitude clipping result of the minute changes. and according to the first scaling factor Amplitude clipping results Perform inverse scaling to obtain the initial scaling signal. .

[0083] The bias circuit 242 is electrically connected to the comparator circuit 241 and the analog-to-digital converter circuit 25, respectively. It receives a reference voltage and scales the initial scaled signal according to a preset second scaling factor to obtain a secondary scaled signal. Under the influence of the reference voltage, the secondary scaled signal is shifted upwards by a preset voltage amplitude to obtain a pressure characteristic signal. The preset voltage amplitude is used to raise the secondary scaled signal when it is below a minimum voltage threshold, ensuring that the pressure characteristic signal falls within the analog input range of the analog-to-digital converter circuit. The overall scaling factor is the product of the first scaling factor and the second scaling factor.

[0084] For example, bias circuit 242 and comparator circuit 241 together provide the overall scaling factor. The comparator circuit 241 provides the first scaling factor. The bias circuit 242 provides a second scaling factor. First scaling factor With the second scaling factor Multiply to obtain the overall scaling factor. The bias circuit 242 operates according to a preset second scaling factor. For the initial scaling signal Scaling is performed to obtain a secondary scaled signal. Secondary scaling signal Under the influence of the reference voltage, according to the preset voltage amplitude An upward level shift is performed to obtain the pressure characteristic signal, for example:

[0085] In this embodiment, the large DC component is dynamically canceled by the comparison circuit 241, and only the initial scaled signal of the small pressure change is retained. The signal is safely matched to the range of the digital-to-analog converter circuit 23 by the bias circuit 242 to avoid over-range. No lossy compression is performed on the pressure detection signal throughout the process, and the initial scaled signal of the small pressure change is not compressed, thus preserving the original resolution of the pressure sensor.

[0086] For another example, the pressure characteristic signal input to the analog-to-digital converter (ADC) chip is a unipolar signal, and the target DC bias signal output by the ADC chip is also a unipolar signal. The pressure characteristic signal obtained by superimposing the inverting detection signal and the target DC bias signal can be either positive or negative. According to the expression for the pressure characteristic signal: It can be seen that: in the target DC bias signal Under the premise of no change, the pressure detection signal Increased pressure characteristic signal Increase; in the pressure detection signal Under the premise of remaining unchanged, the target DC bias signal Increased pressure characteristic signal It gets smaller.

[0087] The significance of setting a reference voltage is that, assuming there is no bias circuit, when the pressure detection signal... When the voltage is 0V, amplitude clipping is no longer necessary. However, to meet the requirement of c(k) tracking r(k), and because the output signal of the digital-to-analog converter (DAC) is a unipolar signal, and the input signal of the DAC is also a unipolar signal, the target DC bias signal output by the DAC is... It will not be a negative signal. This is necessary to still be able to sample and obtain a 0V pressure detection signal. Furthermore, considering that r(k) is the digital signal corresponding to the midpoint voltage, and given the offset voltage (typically in the mV range) of the third operational amplifier, the signal output by the third operational amplifier in the comparator circuit is near zero voltage—for example, above, below, or equal to zero voltage. Analog-to-digital converters (ADCs) that only support unipolar inputs cannot acquire signals below zero voltage. Therefore, when the pressure detection signal is less than the minimum voltage threshold (e.g., the minimum voltage threshold is 0), without clipping, the output of the ADC is 0. Due to the offset voltage of the third operational amplifier, the input signal to the ADC may be less than 0. Since the ADC only supports acquiring positive inputs, it will not acquire the pressure detection signal 0 in this case, leading to signal sampling distortion.

[0088] This embodiment of the application provides a bias circuit that, under the influence of a reference voltage, offers a preset voltage amplitude. This preset voltage amplitude can be used to scale the signal in a secondary manner. When the voltage is less than zero, raise the second scaling signal. To ensure pressure characteristic signal The signal must fall within the analog input range of the analog-to-digital converter circuit. This helps suppress interference from offset voltage and ensures that the analog-to-digital converter chip can sample pressure detection signals of any amplitude. This improves sampling accuracy.

[0089] In some embodiments, the analog-to-digital conversion circuit 25 is configured with an analog input range. The sum of any target product result and a preset voltage amplitude is less than the maximum boundary value of the analog input range. The arbitrary target product result is the product of the overall scaling factor and the arbitrary amplitude clipping result after inversion processing. That is, the maximum pressure detection signal minus the product of the minimum analog bias signal and the gain amplification factor is used to obtain the maximum difference. The maximum difference is multiplied by the overall scaling factor to obtain the multiplication result. The multiplication result is added to the preset voltage amplitude to obtain the maximum voltage value. This maximum voltage value is less than the maximum boundary value of the analog input range. The mathematical expression of the above process is:

[0090] in, For the minimum analog bias signal, This is the gain amplification factor. This is the maximum pressure detection signal. For the maximum difference, To simulate the maximum boundary value of the input range, This is the overall scaling factor.

[0091] This application embodiment achieves this by reasonably setting the overall scaling factor. This ensures that the voltage amplitude of the pressure characteristic signal after dynamic biasing and amplitude clipping is strictly limited within the analog input range of the analog-to-digital converter circuit 25, thereby achieving lossless matching between the pressure characteristic signal and the analog input range.

[0092] Understandably, the overall scaling factor can be customized and assigned by the designer based on engineering experience, including both the first and second scaling factors. However, the overall scaling factor must be greater than or equal to the smaller of the voltage resolutions of the analog-to-digital converter chip and the pressure sensor. For example, if the voltage resolution of the analog-to-digital converter chip is 100µV (i.e., 0.1mV) and the voltage resolution of the pressure sensor is 1mV, then the overall scaling factor is 0.1.

[0093] Please see Figure 8 The comparator circuit 241 includes a seventh resistor R7, an eighth resistor R8, a ninth resistor R9, a tenth resistor R10, and a third operational amplifier U3. The first terminal of the seventh resistor R7 is grounded, and the second terminal of the seventh resistor R7 is electrically connected to the non-inverting input terminal of the third operational amplifier U3. The inverting input terminal of the third operational amplifier U3 is electrically connected to the first terminals of the eighth resistor R8, the ninth resistor R9, and the tenth resistor R10, respectively. The second terminal of the eighth resistor R8 is electrically connected to the output terminal of the signal inverting circuit 21 (i.e., the first operational amplifier U1). The second terminal of the tenth resistor R10 is electrically connected to the digital-to-analog converter circuit (i.e., the output terminal of the second operational amplifier U2). The second terminal of the ninth resistor R9 is electrically connected to the output terminal of the third operational amplifier U3.

[0094] Please continue reading. Figure 8 The bias circuit 242 includes an eleventh resistor R11 and a twelfth resistor R12. The first end of the eleventh resistor R11 is electrically connected to the output of the third operational amplifier U3. The second end of the eleventh resistor R11 is electrically connected to the first end of the twelfth resistor R12 and the analog-to-digital converter circuit 25, respectively. A reference voltage of 2.5V is applied to the second end of the twelfth resistor R12.

[0095] Wherein, the first scaling factor is The second scaling factor is The preset voltage amplitude is .in, This is the reference voltage.

[0096] Inverted detection signal The target DC bias signal is input to the third operational amplifier U3 through the seventh resistor R7, and the target DC bias signal is input to the third operational amplifier U3 through the tenth resistor R10. The third operational amplifier U3 converts the target DC bias signal into a signal that is directly input to the third operational amplifier U3. With inverted detection signal The signals are added together, and then scaled inversely using resistors R8 and R9 according to the first scaling factor to obtain the initial scaled signal. The bias circuit 242 further modulates the initial scaled signal through the eleventh resistor R11 and the twelfth resistor R12. Enter After scaling, a secondary scaling signal is obtained. Secondary scaling signal Under the influence of a reference voltage, the voltage is shifted upwards according to a preset voltage amplitude to obtain a pressure characteristic signal. The preset voltage amplitude... ,in, The reference voltage, This is the second scaling factor. This is the preset voltage amplitude.

[0097] The gain amplification factor 'a' is determined by hardware constraints, signal range, and accuracy requirements to accurately match the detection range of the pressure sensor. The gain amplification factor 'a' is subject to the following constraints: 1) Coverage of the pressure detection signal range: Assuming the pressure sensor's detection range is 0-10V, i.e., the pressure detection signal... The value range is 0-10V, and the range of the digital-to-analog converter chip 231 is 0-2.5V, that is, the full-scale output of the digital-to-analog converter circuit 23 is 2.5V.

[0098] To ensure that the target DC bias signal cancels out the large DC component in the inverted detection signal, this embodiment requires setting the gain amplification factor to 4. This ensures that the final output value of the target DC bias signal from the gain amplifier circuit 232 is within the range of 0-10V (i.e., 2.5*4=10). The range of the target DC bias signal is consistent with that of the pressure detection signal. The value range is completely compatible and consistent; therefore, pressure detection signals of any amplitude are perfectly matched. All can be biased by the target DC signal Effectively offset.

[0099] 2) Balance between accuracy and dynamic range: The value of the gain amplification factor 'a' should not be too large, otherwise it will easily amplify the quantization noise of the digital-to-analog converter chip 231; the value of the gain amplification factor 'a' should not be too small either, otherwise it will not be able to cover the value range of the pressure detection signal.

[0100] The overall scaling factor b is determined by hardware constraints, signal range, and accuracy requirements to accurately adapt to the range of the analog-to-digital converter circuit 25. The overall scaling factor b is subject to the following constraints: 1) Range of the analog-to-digital converter circuit 25: Assuming the range of the analog-to-digital converter circuit 25 is 0-1.25V, and the target DC bias signal... With pressure detection signal The difference range (i.e., the value range of the initial scaling signal) can reach 0-10V. The bias circuit 242 compresses the initial scaling signal based on the overall scaling factor b, so that the 10V difference range is compressed to 10 / 8=1.25V. That is, the value range of the pressure characteristic signal is 0-1.25V, and the value range of the pressure characteristic signal matches the range of the analog-to-digital converter circuit 25.

[0101] 2) Ensure unipolar safety: The attenuated pressure characteristic signal is always positive to avoid damage to the single-power-supply analog-to-digital conversion circuit 25 by negative voltage.

[0102] In real circuit devices, operational amplifiers, resistors, DACs, and ADCs are not ideal devices; they all exhibit discreteness, easily producing gain errors and DC offsets, causing deviations between the theoretical gain amplification factor 'a' and the overall scaling factor 'b'. For example, the resistance value may have an error of ±1%, and the operational amplifier may have an offset voltage, resulting in a mismatch between the actual gain and the theoretical bias value.

[0103] In the pressure detection circuit provided in this application embodiment, the digital-to-analog converter chip 231, gain amplifier circuit 232, comparator circuit 241, pressure sensor, and analog-to-digital converter circuit 25 all exhibit gain error and DC offset error. Specifically, in this application embodiment, the actual output gain of the digital-to-analog converter chip 231 is set to... The actual DC offset error is In this embodiment, the actual output gain of the operational amplifier in the gain amplifier circuit 232 or the comparator circuit 241 is set to... The actual DC offset error is In this embodiment, the actual output gain of the pressure sensor is set to... In this embodiment, the actual output gain of the analog-to-digital converter circuit 25 is set to... The actual DC offset error is .

[0104] This embodiment of the application combines all actual output gains between the digital-to-analog converter chip 231 and the analog-to-digital converter circuit 25, resulting in: .

[0105] This embodiment of the application combines all actual output gains between the pressure sensor and the analog-to-digital converter circuit 25, resulting in: .

[0106] The embodiments of this application incorporate all actual DC offset errors, resulting in: .

[0107] Considering the discrete nature of circuit components, in order to obtain accurate gain amplification factor 'a' and overall scaling factor 'b', this application embodiment, in conjunction with the circuit topology of the voltage detection circuit, derives calibration formulas for gain amplification factor 'a' and overall scaling factor 'b', as shown below:

[0108] Simplifying the above formulas, we get:

[0109] in, , , ,in, ,Right now This is the gain amplification factor. ,Right now This is the overall scaling factor.

[0110] This application is based on the formula " Perform the following calibration operations, as follows: 1) First calibration operation: Input the known first pressure detection signal Record the first analog bias signal output by the digital-to-analog converter chip 231 and the first pressure characteristic signal of the input analog-to-digital converter circuit 25 Substituting into the formula, we obtain Equation 1, as shown below:

[0111] 2) Second calibration operation: Input the known second pressure detection signal Record the second analog bias signal output by the digital-to-analog converter chip 231 and the second pressure characteristic signal of the input analog-to-digital converter circuit 25 Substituting into the formula, we get Equation 2, as shown below:

[0112] 3) Third calibration operation: Input the known third pressure detection signal Record the third analog bias signal output by the digital-to-analog converter chip 231. and the third pressure characteristic signal of the input analog-to-digital converter circuit 25 Substituting into the formula, we get equation 3, as shown below:

[0113] By solving equations 1 to 3 simultaneously, we can derive... , And B, thus deriving a and b.

[0114] To illustrate the working principle of the pressure detection circuit provided in the embodiments of this application, the embodiments of this application are combined with... Figures 9 to 12 A detailed explanation is provided below: Figure 9 A complete circuit diagram of the pressure detection circuit provided in an embodiment of this application is shown.

[0115] Figure 10 The waveform of the raw pressure detection signal output by the pressure sensor is shown, reflecting changes in vacuum pressure. For example... Figure 10 As shown, the pressure detection signal The waveform characteristics are: an overall periodic pattern of "slow rise → rapid fall". The pressure detection signal includes the absolute pressure level (e.g., 0-10V) and details of the change (Δs).

[0116] Figure 11 The target DC bias signal output by the digital-to-analog converter circuit 23 is shown. The waveform diagram. Target DC bias signal. The waveform characteristics are: stepped, and because the digital-to-analog converter circuit 23 uses digital control, the level is updated once after each PID adjustment. The target DC bias signal output by the digital-to-analog converter circuit 23... Follow pressure detection signal The absolute level is used to cancel the pressure detection signal. The large DC component.

[0117] Figure 12 This shows the pressure characteristic signal sent to the digital-to-analog converter circuit 23. Waveform diagram. Pressure characteristic signal. The waveform characteristics are: compressed to an extremely small range (e.g., 0-0.2V), fluctuating around the midpoint voltage (e.g., 0.5V). Pressure characteristic signal. reflect and The difference (i.e., the signal change Δs) is the high-precision signal actually acquired by the digital-to-analog converter 23.

[0118] Combination Figures 9 to 12 Further explanation of the working principle of the pressure detection circuit: (a) Rising phase: slow change → stable small sawtooth pattern Waveform representation: It rises slowly and linearly from a low level. Synchronous step-by-step lifting, Maintain stable, small sawtooth-like fluctuations.

[0119] Control logic: The DC bias increases slowly, and the controller calculates the DC bias value in each cycle based on a PID algorithm. , The rise was almost synchronous, offsetting The absolute level of the rise. Pressure characteristic signal. Stabilized within a very small range, retaining only The rising slope and slight offset.

[0120] Accuracy significance: The full resolution of the ADC is used to measure minute differences, and rising details are precisely quantized (stabilizing small jagged edges).

[0121] (II) Descent Phase: Rapid Jump → Deep Sawtooth Waveform representation: A rapid and steep decline from the peak, Because the stepped output cannot keep up instantly, Two deep serrations appeared.

[0122] Control logic: The signal drops rapidly, and the update speed of the DAC's stepped output cannot keep up with the rate of signal change. Temporarily remaining at a higher level, compared to a rapid decline. This results in a significant difference. (Pressure characteristic signal) It was instantly stretched, forming deep serrations, and retaining... Details of the rapid descent.

[0123] Accuracy significance: Deep sawtooth patterns are a high-precision mapping of rapidly changing signals, and the full resolution of the ADC is used to capture this critical detail of change.

[0124] Real-time offset The absolute level (static component); the pressure characteristic signal fed into the ADC. It only reflects the difference between the two (change Δs), including the entire process of rise and fall; therefore, the entire effective resolution of the ADC is used to measure the details of the change in the signal, rather than wasted on the absolute level, thus achieving high-precision, lossless acquisition.

[0125] In summary, the role of dynamic bias is as follows: the DAC follows the pressure detection signal from the pressure sensor in real time, canceling out the absolute level of the large dynamic range; regardless of whether the signal rises slowly or falls rapidly, the input of the ADC is always compressed into a very small range, maximizing accuracy; the details of signal fluctuations (including the rise slope and fall rate) are completely preserved without losing any information.

[0126] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of this application as described above, which are not provided in detail for the sake of brevity; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A pressure detection circuit for a semiconductor process gas path, characterized in that, include: The signal inversion circuit is configured to acquire the pressure detection signal transmitted by the pressure sensor, invert the pressure detection signal, and obtain an inverted detection signal. The controller is configured to output a DC bias command, the DC bias command including a DC bias value; A digital-to-analog converter circuit, electrically connected to the controller, is configured to output a target DC bias signal based on the DC bias value in response to the DC bias command; An amplitude clipping circuit is electrically connected to the signal inversion circuit and the digital-to-analog converter circuit, respectively, and is configured to perform an amplitude clipping operation on the inverted detection signal according to the target DC bias signal to obtain a pressure characteristic signal. An analog-to-digital conversion circuit, electrically connected to the amplitude clipping circuit and the controller, is configured to perform analog-to-digital conversion processing on the pressure characteristic signal to obtain a characteristic digital signal, and transmit the characteristic digital signal to the controller so that the controller can restore the pressure detection signal in digital form based on the characteristic digital signal and the digital signal corresponding to the target DC bias signal to obtain a digital detection signal.

2. The pressure detection circuit according to claim 1, characterized in that, The analog-to-digital conversion circuit is configured with an analog input range, and the controller is configured to output a DC bias command, including: Acquire a target digital signal, wherein the target digital signal is used to limit the amplitude of any of the pressure characteristic signals to always remain within the analog input range; Based on the target digital signal and the characteristic digital signal, determine the target error at the current sampling time; The target error at the current sampling time is adjusted using a preset PID algorithm to obtain the DC bias value. A DC bias command is generated based on the DC bias value.

3. The pressure detection circuit according to claim 2, characterized in that, The target digital signal is the digital signal corresponding to the midpoint voltage of the analog input range; And / or, Determining the target error at the current sampling time based on the target digital signal and the feature digital signal includes: subtracting the target digital signal from the feature digital signal to obtain the target error at the current sampling time.

4. The pressure detection circuit according to claim 1, characterized in that, The digital-to-analog converter circuit includes: The digital-to-analog converter chip is configured to output an analog bias signal based on the DC bias value in response to the DC bias command; The gain amplifier circuit, electrically connected to the digital-to-analog converter chip, is configured to amplify the analog bias signal based on a preset gain amplification factor to obtain the target DC bias signal.

5. The pressure detection circuit according to claim 4, characterized in that, The digital-to-analog converter chip is configured to output an analog bias signal based on the DC bias value in response to the DC bias command, including: In response to the DC bias command, the DC bias value is parsed from the DC bias command; Obtain historical bias values, wherein the historical bias values ​​are digital signals corresponding to the DC bias signals at the previous sampling time, and the sampling times of the DC bias signals at the previous sampling time are arranged in the time series before and adjacent to the sampling times of the target DC bias signals. The target signal amplitude is determined based on the DC bias value and the historical bias value; Output an analog bias signal according to the target signal amplitude.

6. The pressure detection circuit according to claim 4, characterized in that, The pressure sensor is configured with a voltage sampling range, and the product of the gain amplification factor and the voltage amplitude of the maximum analog bias signal is greater than or equal to the maximum value of the voltage sampling range; and / or, The signal inverting circuit includes a first resistor, a second resistor, a third resistor, a fourth resistor, and a first operational amplifier. The pressure detection signal is applied to the first terminal of the first resistor. The second terminal of the first resistor is electrically connected to the first terminal of the second resistor and the inverting input terminal of the first operational amplifier. The second terminal of the second resistor is electrically connected to the output terminal of the first operational amplifier. The first terminal of the third resistor is grounded. The second terminal of the third resistor is electrically connected to the first terminal of the fourth resistor and the non-inverting input terminal of the first operational amplifier. The pressure detection signal is applied to the second terminal of the fourth resistor. The gain amplifier circuit includes a fifth resistor, a sixth resistor, and a second operational amplifier. The first end of the fifth resistor is grounded, and the second end of the fifth resistor is electrically connected to the first end of the sixth resistor and the inverting input of the second operational amplifier, respectively. The second end of the sixth resistor is electrically connected to the output of the second operational amplifier, and the non-inverting input of the second operational amplifier is electrically connected to the output of the digital-to-analog converter chip.

7. The pressure detection circuit according to claim 1, characterized in that, The amplitude clipping circuit includes: The comparator circuit is electrically connected to the signal inversion circuit and the digital-to-analog converter circuit, respectively. It is configured to add the target DC bias signal and the inverted detection signal to obtain the amplitude clipping result, and then perform inverted scaling on the amplitude clipping result according to a preset first scaling factor to obtain the initial scaled signal. A bias circuit, electrically connected to both the comparator circuit and the analog-to-digital converter circuit, is configured to receive a reference voltage and scale the initial scaled signal according to a preset second scaling factor to obtain a secondary scaled signal. The secondary scaled signal, under the influence of the reference voltage, undergoes an upward level shift according to a preset voltage amplitude to obtain a pressure characteristic signal. The preset voltage amplitude is used to raise the secondary scaled signal when it is less than a minimum voltage threshold, ensuring that the pressure characteristic signal falls within the analog input range of the analog-to-digital converter circuit.

8. The pressure detection circuit according to claim 7, characterized in that, The comparator circuit includes a seventh resistor, an eighth resistor, a ninth resistor, a tenth resistor, and a third operational amplifier. The first terminal of the seventh resistor is grounded, and the second terminal of the seventh resistor is electrically connected to the non-inverting input terminal of the third operational amplifier. The inverting input terminal of the third operational amplifier is electrically connected to the first terminals of the eighth, ninth, and tenth resistors, respectively. The second terminal of the eighth resistor is electrically connected to the output terminal of the signal inverting circuit. The second terminal of the tenth resistor is electrically connected to the digital-to-analog converter circuit, and the second terminal of the ninth resistor is electrically connected to the output terminal of the third operational amplifier. The bias circuit includes an eleventh resistor and a twelfth resistor. The first end of the eleventh resistor is electrically connected to the output of the third operational amplifier. The second end of the eleventh resistor is electrically connected to the first end of the twelfth resistor and the analog-to-digital conversion circuit, respectively. The reference voltage is applied to the second end of the twelfth resistor.

9. The pressure detection circuit according to any one of claims 1 to 8, characterized in that, The amplitude clipping circuit is configured with an overall scaling factor. The controller, based on the characteristic digital signal and the digital signal corresponding to the target DC bias signal, digitally reconstructs the pressure detection signal to obtain a digital detection signal, including: The characteristic digital signal is subjected to a downward level shifting process according to a preset voltage amplitude to obtain a level shifting result; Divide the level shift result by the overall scaling factor to obtain the initial result; The digital signal corresponding to the target DC bias signal is added to the initial result to obtain the digital voltage amplitude; The pressure detection signal is restored in digital form based on the digital voltage amplitude to obtain a digital detection signal.

10. A gas flow measurement system, characterized in that, Includes the pressure detection circuit as described in any one of claims 1 to 9.

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