Differential amplification structure-based anti-interference pressure sensor signal conditioning circuit

Abstract

The invention provides an anti-interference pressure sensor signal conditioning circuit based on a differential amplification structure, and the circuit comprises a differential input module which is used for receiving a differential signal outputted by a pressure sensor, and carrying out the amplification and filtering of the outputted differential signal, and obtaining a first differential signal; the common-mode suppression module is electrically connected with the differential input module and is used for suppressing a common-mode signal in the first differential signal to obtain a second differential signal; the programmable gain amplification module is electrically connected with the common-mode suppression module and is used for performing programmable gain amplification on the second differential signal to obtain a third differential signal; the low-pass filtering module is electrically connected with the programmable gain amplification module and is used for filtering high-frequency noise in the third differential signal to obtain a fourth differential signal; and the output buffer module is electrically connected with the low-pass filtering module and is used for converting the fourth differential signal into a single-ended signal and outputting the single-ended signal. According to the invention, external electromagnetic interference and common-mode noise can be effectively suppressed, and the stability and accuracy of signal transmission are improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sensor detection, and particularly relates to an anti-interference type pressure sensor signal conditioning circuit based on a differential amplification structure. BACKGROUND

[0002] As a core sensing element, the pressure sensor has irreplaceable application value in key fields such as industrial automation control systems, automobile safety monitoring devices and medical diagnostic instruments. However, the weak characteristics of the output signal of the pressure sensor are the inevitable result of the joint action of physical principles and design requirements: the sensitive element causes a slight change in the resistance or capacitance parameter through a slight mechanical deformation, and the energy conversion process is inefficient, resulting in a very low original electric signal amplitude, usually in the microvolt to millivolt order. At the same time, the design constraints of product miniaturization, low power consumption and high reliability further limit the signal energy output, and the low amplitude of the original signal must be maintained to avoid synchronous amplification of noise and signal, thereby ensuring the initial signal-to-noise ratio. Because the signal is weak, it is easily disturbed by external electromagnetic interference in the transmission and processing process. In the industrial field environment, power line harmonics, motor start-stop transients and wireless communication equipment radiation can all introduce significant noise. In addition, the common-mode noise caused by the difference in the ground loop and the coupling of the environmental electromagnetic field will be superimposed on the differential signal, causing measurement distortion.

[0003] The traditional signal conditioning circuit is implemented using a pure analog architecture, completely relying on discrete devices such as resistors, capacitors and operational amplifiers to build, and lacks the support of digital programmable chips. Circuit parameters such as gain coefficient and filtering characteristics are determined by fixed physical elements, and adjustment must be performed by disassembling and welding, which cannot be dynamically optimized according to the working condition changes. The circuit design is highly adapted to a specific type of sensor, such as being customized for a certain type of strain gauge pressure sensor, resulting in a serious lack of universality and difficulty in compatibility with sensors of different brands or specifications. The debugging process highly depends on external instruments such as oscilloscopes and signal generators for manual calibration, and cannot realize automatic compensation and real-time optimization. This design logic of "simple analog module solving a single problem" forcibly optimizes the signal by hardware matching, making the anti-interference ability of the traditional scheme weak in a complex electromagnetic environment, and the signal amplification precision is difficult to guarantee. Especially in high-precision scenes such as aerospace precision measurement or medical vital sign monitoring, the measurement error problem is particularly prominent, and it cannot meet the strict requirements of modern industry on measurement accuracy and stability SUMMARY The application provides an anti-interference type pressure sensor signal conditioning circuit based on a differential amplification structure, which can effectively suppress external electromagnetic interference and common-mode noise, improve the stability and accuracy of signal transmission, realize flexible adjustment of circuit parameters through programmable gain amplification, enhance the adaptability of the circuit to different working conditions, and improve the universality of the signal conditioning circuit, which can be compatible with various types of pressure sensors.

[0004] The application provides an anti-interference pressure sensor signal conditioning circuit based on a differential amplification structure, comprising: a differential input module configured to receive a differential signal output by a pressure sensor, amplify and filter the differential signal output, and obtain a first differential signal; a common-mode rejection module electrically connected to the differential input module and configured to reject a common-mode signal in the first differential signal and obtain a second differential signal; a programmable gain amplification module electrically connected to the common-mode rejection module and configured to perform programmable gain amplification on the second differential signal and obtain a third differential signal; a low-pass filter module electrically connected to the programmable gain amplification module and configured to filter high-frequency noise in the third differential signal and obtain a fourth differential signal; an output buffer module electrically connected to the low-pass filter module and configured to convert the fourth differential signal into a single-ended signal and output the single-ended signal.

[0005] Optionally, the differential input module comprises a first capacitor C1, a second capacitor C2 and a first inductor L1. One end of the first capacitor C1 is electrically connected to a positive terminal of the differential signal output by the pressure sensor, and the other end is electrically connected to one end of a first resistor R1, one end of a third capacitor C3 and a V+IN pin of a first instrument amplifier U1; a V-IN pin of the first instrument amplifier U1 is electrically connected to an end of the third capacitor C3 away from the first capacitor C1, an end of the first resistor R1 away from the first capacitor C1 and one end of the second capacitor C2; an end of the second capacitor C2 away from the first resistor R1 is electrically connected to a negative terminal of the differential signal output by the pressure sensor and one end of a second resistor R2; and an end of the second resistor R2 away from the second capacitor C2 is grounded. A third resistor R3 is connected in series between two RG pins of the first instrument amplifier U1; a V+ pin of the first instrument amplifier U1 is externally connected to a positive direct current voltage; the V+ pin and a REF pin of the first instrument amplifier U1 are grounded; a VO pin of the first instrument amplifier U1 is electrically connected to a second inductor L2; one end of the second inductor L2 away from the first instrument amplifier U1 is electrically connected to one end of a fourth capacitor C4 and serves as a positive terminal of the first differential signal; and one end of the fourth capacitor C4 away from the second inductor L2 is grounded. One end of the first inductor L1 is grounded, and the other end is electrically connected to one end of a fifth capacitor C5 and serves as a negative terminal of the first differential signal; and one end of the fifth capacitor C5 away from the first inductor L1 is grounded.

[0006] Optionally, the differential input module further comprises a first bidirectional TVS suppression diode D1, a second bidirectional TVS suppression diode D2 and a sixth capacitor C6; One end of the first bidirectional TVS suppression diode D1 is grounded, and the other end is electrically connected to one end of the first resistor R1 close to the first capacitor C1; One end of the second bidirectional TVS suppression diode D2 is grounded, and the other end is electrically connected to one end of the first resistor R1 away from the first capacitor C1; One end of the sixth capacitor C6 is grounded, and the other end is electrically connected to the V+ pin of the first instrument amplifier U1.

[0007] Optionally, the common mode suppression module comprises a fourth resistor R4, a fifth resistor R5 and a second instrument amplifier U2; One end of the fourth resistor R4 is electrically connected to the positive end of the first differential signal, and the other end is electrically connected to the IN+ pin of the second instrument amplifier U2; one end of the fifth resistor R5 is electrically connected to the negative end of the first differential signal, and the other end is electrically connected to the IN- pin of the second instrument amplifier U2. The sixth resistor R6 is connected in series between the -RG pin and the +RG pin of the second instrument amplifier U2; the V+ pin of the second instrument amplifier U2 is externally connected to a positive DC voltage, the OUT pin serves as the output end of the second differential signal, and the REF pin is electrically connected to the seventh resistor R7 and the eighth resistor R8; One end of the seventh resistor R7 away from the second instrument amplifier U2 is externally connected to a positive DC voltage; one end of the eighth resistor R8 away from the second instrument amplifier U2 is grounded.

[0008] Optionally, the common mode suppression module further comprises a seventh capacitor C7; One end of the seventh capacitor C7 is grounded, and the other end is electrically connected to the V+ pin of the second instrument amplifier U2.

[0009] Optionally, the programmable gain amplification module comprises a third instrument amplifier U3; The +IN pin of the third instrument amplifier U3 is electrically connected to the output end of the second differential signal; the A0 pin of the third instrument amplifier U3 is connected in series with the ninth resistor R9, and the A1 pin is connected in series with the tenth resistor R10; one end of the ninth resistor R9 away from the third instrument amplifier U3 is electrically connected to one end of the tenth resistor R10 away from the third instrument amplifier U3 and externally connected to a positive DC voltage; The +VS pin of the third instrument amplifier U3 is externally connected to a positive DC voltage, and the OUT pin serves as the output end of the third differential signal; The -IN pin, DGND pin, -VS pin, REF pin and The pins are all grounded.

[0010] Optionally, the programmable gain amplification module further comprises an eighth capacitor C8 and a ninth capacitor C9; One end of the eighth capacitor C8 and one end of the ninth capacitor C9 are electrically connected to the +VS pin of the third instrument amplifier U3; the other end of the eighth capacitor C8 away from the third instrument amplifier U3 is electrically connected to the other end of the ninth capacitor C9 away from the third instrument amplifier U3 and is grounded.

[0011] Optionally, the low-pass filter module comprises a tenth capacitor C10, an eleventh resistor R11 and a first operational amplifier U4; One end of the tenth capacitor C10 is electrically connected to the output end of the third differential signal, and the other end is electrically connected to the eleventh resistor R11; one end of the eleventh resistor R11 away from the tenth capacitor C10 is electrically connected to the +IN pin of the first operational amplifier U4; the -IN pin of the first operational amplifier U4 is electrically connected to a twelfth resistor R12 and a thirteenth resistor R13; One end of the twelfth resistor R12 away from the first operational amplifier U4 is electrically connected to an eleventh capacitor C11; one end of the eleventh capacitor C11 away from the twelfth resistor R12 is grounded; the OUT pin of the first operational amplifier U4 is electrically connected to one end of the thirteenth resistor R13 away from the -IN pin of the first operational amplifier U4 and serves as the output end of the fourth differential signal; The V+ pin of the first operational amplifier U4 is externally connected to a positive direct current voltage, and the V- pin is grounded.

[0012] Optionally, the low-pass filter module further comprises a twelfth capacitor C12 and a thirteenth capacitor C13; One end of the twelfth capacitor C12 and one end of the thirteenth capacitor C13 are electrically connected to the V+ pin of the first operational amplifier U4; one end of the twelfth capacitor C12 away from the first operational amplifier U4 is electrically connected to one end of the thirteenth capacitor C13 away from the first operational amplifier U4 and is grounded.

[0013] Optionally, the output buffer module comprises a second operational amplifier U5; The +IN pin of the second operational amplifier U5 is electrically connected to the output end of the fourth differential signal, the V+ pin is externally connected to a positive direct current voltage, and the V- pin is grounded; The OUT pin and the -IN pin of the second operational amplifier U5 are connected in series with a fourteenth resistor R14; The OUT pin of the second operational amplifier U5 is further electrically connected to a fourteenth capacitor C14, a fifteenth resistor R15 and a third bidirectional TVS suppression diode D3; The one end of the fourteenth capacitor C14 away from the second operational amplifier U5 is grounded; The one end of the fifteenth resistor R15 away from the second operational amplifier U5 is used as the output end of the single-ended signal; The one end of the third bidirectional TVS suppression diode D3 away from the second operational amplifier U5 is grounded; The V+ pin of the second operational amplifier U5 is also electrically connected with the fifteenth capacitor C15 and the sixteenth capacitor C16; The one end of the fifteenth capacitor C15 away from the second operational amplifier U5 is electrically connected with the one end of the sixteenth capacitor C16 away from the second operational amplifier U5 and grounded.

[0014] The application provides an anti-interference type pressure sensor signal conditioning circuit based on a differential amplification structure, which realizes preliminary amplification and filtering of a signal through a differential input module, eliminates common-mode interference in combination with a common-mode suppression module, and dynamically adjusts signal gain by using a programmable gain amplification module, so that the weak characteristics of a pressure sensor output signal and external interference problems are effectively solved, external electromagnetic interference and common-mode noise are effectively suppressed, and the stability and accuracy of signal transmission are improved; flexible adjustment of circuit parameters is realized by using the programmable gain amplification, the adaptability of the circuit to different working conditions is enhanced, the universality of the signal conditioning circuit is improved, and multiple types of pressure sensors can be compatible. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions of the present application, the drawings needed in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0016] Figure 1 A structure schematic diagram of an anti-interference type pressure sensor signal conditioning circuit based on a differential amplification structure provided by the embodiment of the present application; Figure 2 A circuit schematic diagram of a differential input module provided by the embodiment of the present application; Figure 3 A circuit schematic diagram of a common-mode suppression module provided by the embodiment of the present application; Figure 4 A circuit schematic diagram of a programmable gain amplification module provided by the embodiment of the present application; Figure 5 A circuit schematic diagram of a low-pass filtering module provided by the embodiment of the present application; Figure 6 A circuit schematic diagram of an output buffer module provided by the embodiment of the present application. DETAILED DESCRIPTION

[0017] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0018] In the conventional existing pressure sensor signal conditioning technology, due to the physical mechanism that the sensitive element converts the micro physical change into the electrical parameter change, the output signal amplitude is limited by the low conversion efficiency of mechanical energy to electrical energy and the design requirements of miniaturization and low power consumption, and the signal is usually in the microvolt to millivolt range; at the same time, the signal is easy to couple external electromagnetic interference and common-mode noise in the transmission path, resulting in that the noise is amplified synchronously in the amplification process, and the measurement accuracy cannot meet the requirements of high-precision applications, and the contradiction between the weak signal characteristics and the noise suppression ability becomes a key bottleneck.

[0019] For example, in the tire pressure monitoring system application scenario in the automotive electronics field, the pressure sensor is installed inside the tire, and the working environment is exposed to the electromagnetic interference source generated by the engine ignition system; when the differential signal output by the sensor is transmitted through the wire, the common-mode noise is coupled to the signal line through the parasitic capacitance, and after being processed by the traditional fixed parameter analog signal conditioning circuit, the output signal appears waveform distortion, and the data acquisition system cannot accurately identify the tire pressure state, thereby triggering the wrong safety control instruction, affecting the dynamic stability of the vehicle.

[0020] If the above technical problems are not solved, the accuracy of the measurement system will continue to deteriorate, which will lead to the deviation of the physiological parameter monitoring result from the true value in the medical equipment application, and will cause the response deviation of the actuator in the industrial automation control process, which seriously restricts the reliability and application range of high-precision measurement technology.

[0021] In an embodiment, as shown in FIG. 1, the embodiment provides an anti-interference type pressure sensor signal conditioning circuit based on a differential amplification structure, which comprises: Figure 1 A differential input module 10 is used for receiving the differential signal output by the pressure sensor, and amplifying and filtering the output differential signal to obtain a first differential signal. A common-mode suppression module 20 is electrically connected to the differential input module, and is used for suppressing the common-mode signal in the first differential signal to obtain a second differential signal.

[0022] A programmable gain amplification module 30 is electrically connected to the common-mode suppression module, and is used for programmable gain amplification of the second differential signal to obtain a third differential signal.

[0023] A differential input module 10 is used for receiving the differential signal output by the pressure sensor, and amplifying and filtering the output differential signal to obtain a first differential signal.

[0024] The low-pass filter module 40 is electrically connected to the programmable gain amplifier module and is used to filter out high-frequency noise in the third differential signal to obtain the fourth differential signal.

[0025] The output buffer module 50 is electrically connected to the low-pass filter module and is used to convert the fourth differential signal into a single-ended signal before output.

[0026] In practical applications, the differential input module 10 refers to the circuit unit that receives the differential signal output by the pressure sensor and amplifies and filters it. It can be implemented by using an integrated instrumentation amplifier in conjunction with passive filtering components, such as using a general-purpose instrumentation amplifier chip combined with a resistor-capacitor network, or using a differential amplifier circuit built with an operational amplifier. Its main purpose is to achieve preliminary amplification of weak differential signals and suppression of high-frequency noise.

[0027] Furthermore, the programmable gain amplifier module 30 refers to a circuit that can adjust the amplification factor according to the control signal. It can be implemented using a digital programmable gain amplifier chip, for example, by configuring the gain parameters through a serial interface, or by using an analog switch to switch the gain resistor network to achieve gain selection. Its main purpose is to achieve dynamic gain adjustment of differential signals to adapt to input signals of different intensities.

[0028] In this embodiment, the output buffer module 50 refers to a circuit that converts differential signals into single-ended signals and provides output drive. It can be implemented using a voltage follower composed of operational amplifiers, such as a buffer circuit built with a single-channel operational amplifier, or a dedicated buffer amplifier integrated circuit. Its main purpose is to achieve signal conversion and impedance matching. The common-mode rejection module 20 eliminates common-mode components through a differential amplification structure, and the low-pass filter module 40 uses passive or active filter networks to filter out high-frequency noise, thus forming a multi-level collaborative processing mechanism. Specifically, this embodiment, through the construction of a differential signal processing link, utilizes the inherent ability of the differential structure to suppress common-mode noise, combined with programmable gain dynamic adjustment and multi-level filtering optimization, to effectively suppress electromagnetic interference and common-mode noise, improve signal accuracy, and overcome the shortcomings of traditional signal conditioning circuits in terms of anti-interference capability and signal amplification accuracy.

[0029] The differential signal output from the pressure sensor is first received by the differential input module 10. This module amplifies and filters the signal using a differential amplification structure (an RC low-pass filter is connected in parallel at the input to suppress high-frequency noise), thereby generating the first differential signal. The differential structure suppresses common-mode noise, effectively filtering out initial high-frequency interference and preventing noise from being amplified synchronously with weak signals, thus providing a stable foundation for subsequent processing. Further, the common-mode suppression module 20 processes the first differential signal, specifically eliminating the common-mode signal component (amplifying the differential signal from the pressure sensor and suppressing 50Hz power frequency interference), resulting in the second differential signal. This effectively isolates external electromagnetic interference sources, preventing common-mode noise from being converted into differential-mode noise and affecting signal accuracy. Therefore, the programmable gain amplification module 30 performs programmable gain amplification based on the second differential signal, generating the third differential signal. Its gain is dynamically adjusted via an external control signal, avoiding signal saturation or distortion problems caused by traditional fixed gain, ensuring that weak signals of different intensities can be accurately amplified to the appropriate range. The low-pass filter module 40 then filters out high-frequency noise in the third differential signal (filtering out high-frequency noise above 1kHz to satisfy the Nyquist sampling theorem), obtaining the fourth differential signal while retaining the effective signal bandwidth to prevent residual interference from contaminating the output quality. Finally, the output buffer module 50 converts the fourth differential signal into a single-ended signal output, maintaining signal integrity through buffer drive to avoid distortion introduced by output impedance mismatch and ensure signal compatibility with subsequent data acquisition equipment.

[0030] As a specific implementation, the differential input module 10 can be implemented as an integrated instrumentation amplifier circuit, for example, using a high-precision, low-noise instrumentation amplifier chip in conjunction with an external resistor and capacitor network. The input terminal is connected to the differential output terminal of the pressure sensor, and the initial gain is set via an adjustable resistor, with an integrated RC filter element to suppress high-frequency interference. The common-mode rejection module 20 can be configured as a differential amplifier, utilizing precision-matched resistors to optimize the common-mode rejection ratio. The programmable gain amplifier module 30 is implemented based on a digital programmable gain amplifier integrated circuit, allowing adjustment of the gain factor via an external digital signal. The low-pass filter module 40 is composed of a passive RC filter, designed for a specific cutoff frequency to filter out high-frequency noise. The output buffer module 50 uses a unity-gain stable operational amplifier configured as a voltage follower to achieve differential-to-single-ended conversion. Specifically, in this embodiment, the coordinated operation of each module ensures that the signal utilizes differential characteristics to suppress interference throughout the entire input-to-output process, while adapting to different application scenarios through a programmable mechanism.

[0031] Through the aforementioned multi-stage signal processing links, the problem of weak pressure sensor output signals and susceptibility to electromagnetic interference and common-mode noise, leading to insufficient measurement accuracy, is effectively solved. The initial filtering and amplification operations of the differential input module 10 ensure the purity of the signal during the enhancement process; the specialized processing of the common-mode rejection module 20 significantly improves the isolation capability against electromagnetic interference; the dynamic adjustment mechanism of the programmable gain amplifier module 30 optimizes the signal amplification process to avoid distortion; the targeted noise suppression of the low-pass filter module 40 preserves the effective signal components; and the conversion function of the output buffer module 50 ensures the stability and compatibility of the output signal. Thus, the overall circuit achieves high-precision conditioning of weak signals, providing a reliable measurement foundation for applications such as industrial control and automotive electronics, avoiding the shortcomings of traditional analog circuits in terms of weak anti-interference capability and insufficient accuracy.

[0032] In this embodiment, the differential input module 10 is used to receive the weak differential signal output by the pressure sensor and perform preliminary amplification and filtering. However, in its implementation, due to the lack of effective electromagnetic interference suppression and high-frequency noise filtering mechanism at the input end, high-frequency noise and electromagnetic interference in the external environment are easily coupled into the signal path, resulting in signal distortion and insufficient suppression of common-mode noise, which in turn affects the accuracy and stability of subsequent signal processing.

[0033] In this regard, such as Figure 2 As shown, this embodiment further proposes a differential input module 10 including a first capacitor C1, a second capacitor C2, and a first inductor L1.

[0034] One end of the first capacitor C1 is electrically connected to the positive terminal LES_P+ of the differential signal output by the pressure sensor, and the other end is electrically connected to one end of the first resistor R1, one end of the third capacitor C3, and the V+IN pin of the first instrumentation amplifier U1; the V-IN pin of the first instrumentation amplifier U1 is electrically connected to the end of the third capacitor C3 away from the first capacitor C1, the end of the first resistor R1 away from the first capacitor C1, and one end of the second capacitor C2; the end of the second capacitor C2 away from the first resistor R1 is electrically connected to the negative terminal LES_P- of the differential signal output by the pressure sensor and one end of the second resistor R2; the end of the second resistor R2 away from the second capacitor C2 is grounded.

[0035] A third resistor R3 is connected in series between the two RG pins of the first instrumentation amplifier U1; the V+ pin of the first instrumentation amplifier U1 is connected to an external positive DC voltage; the V+ pin and REF pin of the first instrumentation amplifier U1 are grounded; the VO pin of the first instrumentation amplifier U1 is electrically connected to a second inductor L2; the end of the second inductor L2 away from the first instrumentation amplifier U1 is electrically connected to one end of a fourth capacitor C4 and serves as the positive terminal LES_IN1+ of the first differential signal; the end of the fourth capacitor C4 away from the second inductor L2 is grounded.

[0036] One end of the first inductor L1 is grounded, and the other end is electrically connected to one end of the fifth capacitor C5 and serves as the negative terminal of the first differential signal LES_IN1-; the end of the fifth capacitor C5 furthest from the first inductor L1 is grounded.

[0037] Specifically, the first capacitor C1 refers to a capacitor element used for signal coupling, which can be implemented using a ceramic capacitor or a film capacitor. Its purpose is to provide an AC coupling path and attenuate high-frequency noise components. The first instrumentation amplifier U1 can be understood as a differential amplifier with a high common-mode rejection ratio (CMRR > 100dB). It can be implemented using an integrated instrumentation amplifier chip such as INA128 (the gain G1 is set by an external resistor RG, G1 = 1 + 50kΩ / RG). Its purpose is to achieve high-precision amplification of the differential signal and suppress common-mode interference. In practical applications, the first inductor L1 is specifically an inductor element used to suppress common-mode interference. It can be implemented using a wire-wound inductor or a ferrite bead. Its purpose is to block the conduction path of high-frequency electromagnetic interference.

[0038] In this embodiment, the INA128 gain setting is as follows: if a gain of G1=20 is required, then RG=50kΩ / (20-1)=2.63kΩ, and 2.61kΩ (0.1% accuracy) is selected.

[0039] The differential input module 10 has an RC low-pass filter (R1=1kΩ, C3=10nF) connected in parallel at its input. The cutoff frequency of the RC low-pass filter is: To suppress high-frequency noise; a 0.1μF ceramic capacitor is connected to the power supply pin for decoupling, reducing the impact of power supply fluctuations.

[0040] Signal purification is achieved through a multi-stage filtering design of the differential input module: the differential signal output from the pressure sensor is input through the first capacitor C1 and forms a low-pass filter network with the first resistor R1, effectively attenuating high-frequency noise and isolating DC components; the third capacitor C3 is connected between the differential signal lines, providing a bypass path for high-frequency common-mode noise and reducing interference between signal lines; the second capacitor C2 and the first capacitor C1 form a symmetrical filter structure to maintain the balance of the differential signal and suppress asymmetrical noise; the first inductor L1 and the fifth capacitor C5 form a π-type filter network at the output end, exhibiting high impedance characteristics against common-mode noise and blocking the conduction of electromagnetic interference; the first instrumentation amplifier U1 amplifies the signal at the gain set by the third resistor R3, and its output end is formed by the second inductor L2 and the fourth capacitor C4 forming an LC low-pass filter to further filter out high-frequency noise generated during amplification, thereby ensuring the purity of the first differential signal.

[0041] During the process of receiving and processing the weak differential signal output by the pressure sensor, the differential input module 10 may be directly affected by external high-voltage transient interference such as electrostatic discharge or electromagnetic pulse, which could damage sensitive components such as the instrumentation amplifier due to overvoltage. Simultaneously, power supply noise coupling can further reduce the accuracy of signal conditioning and the long-term stability of the circuit, making it difficult to guarantee measurement reliability, especially in complex electromagnetic environments such as industrial sites. Therefore, the differential input module also includes a first bidirectional TVS suppression diode D1, a second bidirectional TVS suppression diode D2, and a sixth capacitor C6.

[0042] One end of the first bidirectional TVS suppression diode D1 is grounded, and the other end is electrically connected to one end of the first resistor R1 near the first capacitor C1.

[0043] One end of the second bidirectional TVS suppression diode D2 is grounded, and the other end is electrically connected to the end of the first resistor R1 that is furthest from the first capacitor C1.

[0044] One end of the sixth capacitor C6 is grounded, and the other end is electrically connected to the V+ pin of the first instrumentation amplifier U1.

[0045] In practical applications, the first bidirectional TVS suppression diode D1 refers to a semiconductor protection device used for transient voltage suppression. It can be implemented using a silicon-based bidirectional transient voltage suppression diode array. Its purpose is to quickly clamp overvoltage at the input terminal to prevent damage to sensitive components.

[0046] Among them, the second bidirectional TVS suppression diode D2 can be understood as a symmetrically configured transient protection element. It can be implemented using the same type of TVS diode as D1. Its purpose is to synergistically suppress common-mode interference and maintain differential signal integrity.

[0047] Specifically, the sixth capacitor C6 refers to the power supply decoupling capacitor, which can be implemented using multilayer ceramic capacitors. Its purpose is to filter out high-frequency noise in the power supply line to stabilize the operating voltage.

[0048] The first bidirectional TVS diode D1 quickly clamps transient overvoltages at the positive terminal of the input signal, preventing high-voltage pulses from propagating along the signal path to the first instrumentation amplifier U1. Simultaneously, the second bidirectional TVS diode D2 provides symmetrical protection for the negative terminal of the differential signal within the resistor divider network, ensuring that common-mode interference is effectively suppressed and not converted into differential-mode noise. Furthermore, the sixth capacitor C6 is connected to the V+ pin of the first instrumentation amplifier U1, filtering out high-frequency noise on the power line and stabilizing the operating voltage, thereby reducing the impact of power supply fluctuations on the amplification of weak signals. This combined design achieves synergistic optimization of transient protection and power supply stability at the input port without altering the original signal conditioning function.

[0049] Through the above solution, this embodiment effectively prevents damage to the front-end sensitive components from external high-voltage transient interference, while suppressing the coupling of power supply noise, thereby improving the measurement reliability and long-term stability of the signal conditioning circuit in complex electromagnetic environments such as industrial sites.

[0050] In the process of suppressing common-mode noise in differential signals, the common-mode rejection ratio is insufficient due to the lack of targeted optimization in the module design. This results in the inability to effectively eliminate external electromagnetic interference and common-mode noise, which in turn leads to a decrease in signal conditioning accuracy and stability.

[0051] In this regard, such as Figure 3 As shown, this embodiment further proposes a common-mode suppression module 20 including a fourth resistor R4, a fifth resistor R5, and a second instrumentation amplifier U2.

[0052] One end of the fourth resistor R4 is electrically connected to the positive terminal LES_IN1+ of the first differential signal, and the other end is electrically connected to the IN+ pin of the second instrumentation amplifier U2; one end of the fifth resistor R5 is electrically connected to the negative terminal LES_IN1- of the first differential signal, and the other end is electrically connected to the IN- pin of the second instrumentation amplifier U2.

[0053] A sixth resistor R6 is connected in series between the -RG and +RG pins of the second instrumentation amplifier U2; the V+ pin of the second instrumentation amplifier U2 is connected to an external positive DC voltage, the OUT pin serves as the output terminal of the second differential signal LES_OUT1+, and the REF pin is electrically connected to the seventh resistor R7 and the eighth resistor R8.

[0054] The end of the seventh resistor R7 furthest from the second instrumentation amplifier U2 is connected to a positive DC voltage; the end of the eighth resistor R8 furthest from the second instrumentation amplifier U2 is grounded.

[0055] Among them, the fourth resistor R4 and the fifth resistor R5 refer to the matching resistor network used to establish the differential signal input channel. They can be implemented using high-precision thin film resistors or low-temperature drift metal film resistors. Their purpose is to maintain the impedance balance of the differential signal path and avoid introducing additional common-mode components due to impedance mismatch.

[0056] The second instrumentation amplifier U2 refers to a dedicated signal conditioning integrated circuit with high common-mode rejection capability. It can be implemented using a three-op-amp architecture or an integrated instrumentation amplifier chip. Its purpose is to effectively separate and attenuate common-mode noise through an internal differential amplification structure.

[0057] The sixth resistor R6 is an external adjustment element used to dynamically configure the gain parameters of the second instrumentation amplifier U2. It can be implemented using a fixed-value precision resistor or an adjustable potentiometer. Its purpose is to flexibly set the amplification factor according to the actual interference intensity to prevent signal overload or noise amplification.

[0058] The seventh resistor R7 and the eighth resistor R8 are resistor pairs that form the reference voltage divider circuit. They can be implemented using temperature coefficient matched precision resistor pairs or integrated resistor networks. Their purpose is to provide a stable DC bias reference for the second instrumentation amplifier U2, ensuring that the output signal operates within the linear range of subsequent circuits.

[0059] In this embodiment, the first differential signal is connected to the IN+ and IN- pins of the second instrumentation amplifier U2 via the fourth resistor R4 and the fifth resistor R5, respectively, to initially suppress common-mode noise using the inherent differential input characteristics of the instrumentation amplifier; the internal circuit of the second instrumentation amplifier U2 precisely sets the gain G2 based on the sixth resistor R6 between the -RG and +RG pins. While amplifying the differential signal, it further attenuates the common-mode component; at the same time, the voltage divider network formed by the seventh resistor R7 and the eighth resistor R8 provides a constant reference level for the REF pin, effectively suppressing common-mode voltage drift, thereby achieving deep elimination of electromagnetic interference and reliable guarantee of signal integrity.

[0060] In this embodiment, the second instrumentation amplifier U2 can specifically adopt the AD623 instrumentation amplifier integrated circuit (CMRR > 105dB at 50Hz, supports rail-to-rail input); the fourth resistor R4 and the fifth resistor R5 are precision thin-film resistors in 0603 packages; the sixth resistor R6 is a multi-turn adjustable potentiometer to achieve fine adjustment of gain; the seventh resistor R7 and the eighth resistor R8 are a matched pair thin-film resistor array, and their resistance ratio is dynamically configured according to the system power supply voltage to establish a precise reference level for the second instrumentation amplifier U2.

[0061] Common-mode rejection ratio (CMRR) verification: INA128 had a CMRR of 105 dB at G1=20, and AD623 had a CMRR of 108 dB at G2=10. 总 =105dB+108dB=213dB (theoretical value).

[0062] AD623 LC filter characteristics: A 1mH inductor and a 1μF capacitor form a second-order low-pass filter with a cutoff frequency of: Suppression capability against 50Hz power frequency interference: attenuation of approximately 30dB.

[0063] In practical applications, capacitors are added to the common-mode rejection module to stabilize the power supply voltage. However, in this process, since the V+ pin of the second instrumentation amplifier U2 is directly connected to the positive DC voltage and lacks filtering measures, power supply noise is easily coupled into the signal path, resulting in a decrease in the common-mode rejection effect and affecting the anti-interference capability and measurement accuracy of the pressure sensor signal.

[0064] In this regard, this embodiment further proposes that the common-mode suppression module 20 also includes a seventh capacitor C7.

[0065] One end of the seventh capacitor C7 is grounded, and the other end is electrically connected to the V+ pin of the second instrumentation amplifier U2.

[0066] Specifically, the seventh capacitor C7 refers to a decoupling capacitor, which can be implemented using ceramic capacitors, electrolytic capacitors, or tantalum capacitors. Its purpose is to provide a low-impedance discharge path for power supply noise, thereby stabilizing the operating voltage of the second instrumentation amplifier U2. The selection of this capacitor can be based on a generalized design based on the operating frequency range and noise characteristics. For example, in high-frequency interference scenarios, ceramic dielectric capacitors with excellent high-frequency characteristics are preferred, and their core function is to isolate interference signals introduced from the power supply.

[0067] In this embodiment, by connecting the seventh capacitor C7 in parallel between the V+ pin of the second instrumentation amplifier U2 and ground, a low-pass filter path is formed, allowing power supply noise to be discharged to ground through the capacitor, thereby preventing noise from coupling into the signal path. Since the V+ pin is the positive power input terminal of the amplifier, it is easily affected by high-frequency noise when directly connected to the power supply. This connection method can effectively suppress the interference of power supply noise on the common-mode rejection process, ensuring that weak pressure signals maintain high accuracy in the common-mode rejection stage. The technical logic lies in utilizing the impedance frequency characteristics of the capacitor to present a low-impedance path in the noise frequency band, directing interference energy to the ground plane rather than the signal processing unit.

[0068] The programmable gain amplifier module 30 is used to amplify the second differential signal with programmable gain. However, in its implementation, the adjustment of the gain parameter depends on external hardware modification and requires physical operations such as desoldering and replacing resistors. It cannot achieve dynamic and disturbance-free real-time switching, which limits the adaptability of the circuit to different sensor types or operating conditions and makes it difficult to meet the requirements of flexible gain configuration in high-precision measurement.

[0069] In this regard, such as Figure 4 As shown, this embodiment further proposes a programmable gain amplifier module 30 including a third instrumentation amplifier U3.

[0070] The +IN pin of the third instrumentation amplifier U3 is electrically connected to the output terminal LES_OUT1+ of the second differential signal; the A0 pin of the third instrumentation amplifier U3 is connected in series with the ninth resistor R9, and the A1 pin is connected in series with the tenth resistor R10 (the gain selection pins A0 / A1 are connected to VCC / GND by modifying R9 / R10 to achieve hardware programming); the end of the ninth resistor R9 away from the third instrumentation amplifier U3 is electrically connected to the end of the tenth resistor R10 away from the third instrumentation amplifier U3 and is externally connected to a positive DC voltage.

[0071] The +VS pin of the third instrumentation amplifier U3 is connected to an external positive DC voltage, and the OUT pin is used as the output terminal of the third differential signal LES_OUT2+.

[0072] The -IN pin, DGND pin, -VS pin, REF pin, and pin of the third instrumentation amplifier U3 are all grounded.

[0073] Among them, the third instrumentation amplifier U3 refers to an integrated signal amplifier device with digital gain control capability. It can be implemented using a dedicated integrated circuit with a built-in switchable feedback network. For example, different combinations of feedback resistors with different resistance values ​​can be selected through an internal switching matrix to form discrete gain levels. Its purpose is to provide the basic function of dynamically configuring gain parameters without physically replacing external components. The A0 and A1 pins can be understood as digital control input ports. They can use binary level signal combinations (such as high level / low level) to set the gain factor. Specifically, they can be configured with a variety of predefined gain value selection logic. Its purpose is to directly map the external level state to the internal circuit working mode, thereby avoiding operation interruption caused by hardware modification.

[0074] The ninth resistor R9 and the tenth resistor R10 refer to the pull-up resistor network, which can be implemented using thin-film or thick-film resistors with fixed resistance values. Their purpose is to stably clamp the A0 and A1 pins to a high level, ensuring the reliability and anti-interference capability of the digital control signal. The +VS pin is the positive power input terminal, which can be connected to a regulated DC power supply module. Its purpose is to provide a stable operating voltage for the third instrumentation amplifier U3, ensuring the linearity and noise suppression performance of the signal amplification process. Grounding the -IN, DGND, -VS, REF, and other pins establishes a unified reference potential. This can be implemented using a single-point grounding topology, aiming to eliminate the impact of ground potential drift on gain control accuracy and maintain the integrity of signal processing.

[0075] In this embodiment, the second differential signal is input to the third instrumentation amplifier U3 via the +IN pin. Simultaneously, pins A0 and A1 are fixedly connected to the positive DC voltage via resistors R9 and R10, forming a stable high-level control signal. The third instrumentation amplifier U3 automatically switches the corresponding gain configuration network based on the level combination of pins A0 and A1, precisely amplifying the input second differential signal. The positive DC voltage connected to the +VS pin provides energy support for the entire amplification process, ensuring the dynamic range and stability of the signal processing. The amplified signal is output as the third differential signal via the OUT pin, while all grounded pins together form a low-impedance reference path, effectively suppressing common-mode interference from affecting the gain setting. Therefore, signal gain adjustment depends entirely on changes in the level state, requiring no physical modification to the circuit structure, achieving rapid and disturbance-free switching of the gain parameter.

[0076] In this implementation, the third instrumentation amplifier U3 can be specifically an instrumentation amplifier chip with an integrated digital gain control interface (such as AD8250). Its A0 and A1 pins are connected to a 3.3V DC power supply through the ninth resistor R9 and the tenth resistor R10, respectively, so that both control pins are configured to a high level, thereby fixing the internal gain to 100 times. The +VS pin of the chip is connected to a regulated 5V DC power supply to ensure that the operating voltage ripple is less than 10mV. All ground pins are connected to the main ground point of the circuit board through a short path to form a low-noise reference. Under this configuration, the second differential signal is fully received and amplified, and then output in differential form to the subsequent low-pass filter module, while maintaining the electrical stability of the gain setting.

[0077] Through the above scheme, this embodiment realizes dynamic level control of the gain parameter in the pressure sensor signal conditioning circuit, effectively overcoming the problem of insufficient adaptability caused by the traditional fixed hardware adjustment method, significantly improving the circuit's flexible configuration capability under different sensor types and working conditions, and meeting the technical requirements for real-time, disturbance-free gain switching in high-precision measurement scenarios.

[0078] During the process of programmable gain amplification of differential signals by the programmable gain amplifier module 30, noise introduced by the power line may interfere with the operation of the amplifier, resulting in unstable gain and signal distortion, which in turn affects the accuracy of pressure sensor signal conditioning and anti-interference capability.

[0079] In this embodiment, the programmable gain amplifier module 30 further includes an eighth capacitor C8 and a ninth capacitor C9.

[0080] One end of the eighth capacitor C8 and one end of the ninth capacitor C9 are electrically connected to the +VS pin of the third instrumentation amplifier U3; the end of the eighth capacitor C8 away from the third instrumentation amplifier U3 is electrically connected to the end of the ninth capacitor C9 away from the third instrumentation amplifier U3 and grounded.

[0081] Among them, the eighth capacitor C8 refers to a capacitor used for power supply decoupling, which can be implemented by ceramic capacitor or tantalum capacitor, with the purpose of filtering out high-frequency noise components in the power line; the ninth capacitor C9 refers to another decoupling capacitor that works in conjunction with the eighth capacitor C8, which can be implemented by electrolytic capacitor or film capacitor, with the purpose of expanding the spectrum coverage of noise suppression to cope with power supply interference of different frequencies.

[0082] In this implementation, by connecting the eighth capacitor C8 and the ninth capacitor C9 in parallel at the power input of the third instrumentation amplifier U3, a multi-band filter network is formed, allowing power supply noise to be bypassed in real time before entering the amplifier's core circuitry. Since the ground terminals of the eighth capacitor C8 and the ninth capacitor C9 share the same connection point, a low-impedance loop is constructed, significantly enhancing the suppression of high-frequency noise. Simultaneously, the combination of capacitors with different capacitance values ​​covers a wider noise spectrum, effectively addressing transient interference on the power line, ensuring the stability of the power supply voltage during programmable gain operation, and preventing noise from coupling into the signal path and causing distortion.

[0083] For example, the eighth capacitor C8 is a ceramic capacitor with excellent high-frequency characteristics, and the ninth capacitor C9 is a large-capacity electrolytic capacitor. The two are connected in parallel to the +VS pin of the third instrumentation amplifier U3 and are reliably connected to the system ground plane through a common ground point, thereby achieving effective suppression of power supply noise during the pressure sensor signal conditioning process.

[0084] In the process of filtering out high-frequency noise in the third differential signal by the low-pass filter module 40, the traditional RC filter circuit, due to its simple structure and lack of active adjustment capability, cannot effectively suppress high-frequency interference signals. At the same time, it is easily affected by component parameter deviations, resulting in unstable filtering characteristics, causing signal distortion and decreased measurement accuracy.

[0085] In this regard, such as Figure 5 As shown, this embodiment further proposes a low-pass filter module 40 including a tenth capacitor C10, an eleventh resistor R11, and a first operational amplifier U4.

[0086] One end of the tenth capacitor C10 is electrically connected to the output terminal LES_OUT2+ of the third differential signal, and the other end is electrically connected to the eleventh resistor R11; the end of the eleventh resistor R11 away from the tenth capacitor C10 is electrically connected to the +IN pin of the first operational amplifier U4; the -IN pin of the first operational amplifier U4 is electrically connected to the twelfth resistor R12 and the thirteenth resistor R13.

[0087] The end of the twelfth resistor R12 furthest from the first operational amplifier U4 is electrically connected to the eleventh capacitor C11; the end of the eleventh capacitor C11 furthest from the twelfth resistor R12 is grounded; the OUT pin of the first operational amplifier U4 is electrically connected to the end of the thirteenth resistor R13 furthest from the -IN pin of the first operational amplifier U4 and serves as the output terminal LES_OUT3+ of the fourth differential signal.

[0088] The V+ pin of the first operational amplifier U4 is connected to an external positive DC voltage, and the V- pin is grounded.

[0089] Among them, the tenth capacitor C10 refers to the input stage coupling capacitor, which can be implemented using a ceramic capacitor or a polyester film capacitor. Its purpose is to isolate the DC component and set the input stage filter cutoff frequency. The eleventh resistor R11 can be understood as the input current limiting resistor. Specifically, a metal film resistor or a carbon film resistor can be selected. Its purpose is to form an RC filter network with the tenth capacitor C10 to attenuate high-frequency interference. The first operational amplifier U4 refers to the active filter core device. In practical applications, a general-purpose or low-noise operational amplifier chip can be used. Its purpose is to provide signal amplification and active filtering functions. The twelfth resistor R12 and the thirteenth resistor R13 refer to the feedback network resistors. Specifically, precision resistors or adjustable resistors can be used. Their purpose is to set the closed-loop gain and stabilize the filter phase response. The eleventh capacitor C11 refers to the feedback filter capacitor, which can be understood as an electrolytic capacitor or a ceramic capacitor. Its purpose is to form a second-order low-pass filter stage together with the twelfth resistor R12.

[0090] In this embodiment, the input stage RC filter network is formed by the tenth capacitor C10 and the eleventh resistor R11. The DC component is blocked by the DC blocking and AC passing characteristics of the capacitor. At the same time, the low frequency signal passband range is precisely limited according to the relationship between capacitive reactance and impedance, so as to prevent high frequency noise from directly entering the amplification stage.

[0091] The first operational amplifier U4 operates in non-inverting mode. Its high input impedance effectively reduces the signal source load effect, ensuring the complete transmission of weak differential signals. The twelfth resistor R12 and the eleventh capacitor C11 form an RC low-pass circuit in the feedback path. The capacitor's energy storage characteristics dynamically absorb high-frequency noise energy, while the optimized resistance value of the twelfth resistor R12 optimizes the filter's Q value, preventing oscillations and instability caused by high-frequency interference. The ratio of the thirteenth resistor R13 to the twelfth resistor R12 sets the closed-loop gain, providing appropriate amplification of useful low-frequency signals while exponentially attenuating high-frequency noise. The power supply configuration of the V+ and V- pins of the first operational amplifier U4 provides a stable operating point for the entire module, suppressing common-mode noise introduced by power supply fluctuations, ultimately achieving reliable high-frequency noise filtering and improved signal fidelity.

[0092] For example, the first operational amplifier U4 uses an AD8510 JFET operational amplifier, the tenth capacitor C10 is a 0805 packaged ceramic capacitor, the eleventh capacitor C11 is an X7R surface mount capacitor, and the eleventh resistor R11, twelfth resistor R12, and thirteenth resistor R13 are all 0603 packaged metal film resistors. The input network formed by the tenth capacitor C10 and the eleventh resistor R11 is located near the signal input terminal of the printed circuit board. The feedback path of the first operational amplifier U4 uses short-distance wiring to reduce the influence of parasitic inductance, and the eleventh capacitor C11 is directly connected in parallel across the twelfth resistor R12 to form a compact feedback node.

[0093] Cutoff frequency of the first operational amplifier U4: Gain: .

[0094] The above technical solution effectively overcomes the defect of easy frequency drift in traditional passive filtering, significantly improves the selectivity and stability of filtering, and enables high-frequency noise to be reliably filtered out while maintaining the integrity of low-frequency signals, thereby solving the signal distortion problem and improving the measurement accuracy of pressure sensor signal conditioning.

[0095] In traditional pressure sensor signal conditioning circuits, when filtering high-frequency noise, power supply noise may introduce interference through the power supply pins of the operational amplifier, leading to a decrease in filtering effect and measurement accuracy.

[0096] In this embodiment, the low-pass filter module 40 is further proposed to include a twelfth capacitor C12 and a thirteenth capacitor C13.

[0097] One end of the twelfth capacitor C12 and one end of the thirteenth capacitor C13 are electrically connected to the V+ pin of the first operational amplifier U4; the end of the twelfth capacitor C12 furthest from the first operational amplifier U4 is electrically connected to the end of the thirteenth capacitor C13 furthest from the first operational amplifier U4 and grounded.

[0098] Among them, the twelfth capacitor C12 and the thirteenth capacitor C13 are capacitors used for power supply decoupling. They can be implemented using different types of capacitors such as ceramic capacitors, electrolytic capacitors or tantalum capacitors. The purpose is to provide a stable power supply voltage for the operational amplifier and filter out high-frequency noise. This parallel configuration can be understood as a technical means of constructing a low-impedance bypass path. Its purpose is to cover a wider frequency range and ensure that the power supply voltage remains stable during signal processing.

[0099] In this embodiment, by connecting the twelfth capacitor C12 and the thirteenth capacitor C13 in parallel to the V+ pin of the first operational amplifier U4 and grounding them, the high-frequency noise energy on the power line is quickly guided to the ground line instead of entering the internal circuitry of the operational amplifier. Since the V+ pin of the first operational amplifier U4, as the positive input point of the power supply, is susceptible to high-frequency noise interference, this parallel capacitor structure forms a low-impedance path, effectively isolating the noise from affecting the signal processing stage, thereby preventing noise from being superimposed on the filtered signal.

[0100] For example, the twelfth capacitor C12 and the thirteenth capacitor C13 can be implemented as ceramic capacitors, with one end connected to the V+ pin of the first operational amplifier U4, and the other end grounded after being connected in parallel through a short path, so as to enhance the decoupling effect and adapt to the noise suppression requirements of different frequencies.

[0101] During the process of converting differential signals into single-ended signals by the output buffer module 50, the single-ended signal output is susceptible to external electromagnetic interference and electrostatic discharge, which can lead to signal waveform distortion, decreased accuracy, and potential circuit damage. In particular, it is difficult to maintain stable output in high-noise industrial environments.

[0102] In this regard, such as Figure 6 As shown in the figure, this embodiment further proposes that the output buffer module includes a second operational amplifier U5.

[0103] The +IN pin of the second operational amplifier U5 is electrically connected to the output terminal LES_OUT3+ of the fourth differential signal, the V+ pin is connected to an external positive DC voltage, and the V- pin is grounded.

[0104] A fourteenth resistor R14 is connected in series between the OUT pin and the -IN pin of the second operational amplifier U5.

[0105] The OUT pin of the second operational amplifier U5 is also electrically connected to the fourteenth capacitor C14, the fifteenth resistor R15, and the third bidirectional TVS suppression diode D3.

[0106] The end of the fourteenth capacitor C14 furthest from the second operational amplifier U5 is grounded.

[0107] The end of the fifteenth resistor R15 furthest from the second operational amplifier U5 serves as the output terminal LES_OUT of the single-ended signal.

[0108] The end of the third bidirectional TVS suppressor diode D3 furthest from the second operational amplifier U5 is grounded.

[0109] The V+ pin of the second operational amplifier U5 is also electrically connected to the fifteenth capacitor C15 and the sixteenth capacitor C16.

[0110] The end of the fifteenth capacitor C15 furthest from the second operational amplifier U5 is electrically connected to the end of the sixteenth capacitor C16 furthest from the second operational amplifier U5 and grounded.

[0111] Among them, the second operational amplifier U5 is the core device that realizes the conversion of differential signals to single-ended signals. It can be implemented using a general-purpose operational amplifier chip or a high-precision operational amplifier chip. Its purpose is to provide high input impedance and low output impedance to ensure the integrity of the signal conversion process. The fourteenth resistor R14 is the feedback resistor set between the output terminal and the inverting input terminal. It can be implemented using a metal film resistor or a carbon film resistor. Its purpose is to form a deep negative feedback path to suppress self-excited oscillation.

[0112] The fourteenth capacitor, C14, is a bypass capacitor connected between the output terminal and ground. It can be implemented using a ceramic capacitor or an electrolytic capacitor, and its purpose is to filter out high-frequency noise components.

[0113] The fifteenth resistor, R15, is a resistor element used for output current limiting and impedance matching. It can be implemented using a wire-wound resistor or a surface-mount resistor. Its purpose is to limit the output current intensity and match the transmission link impedance.

[0114] The third bidirectional TVS suppression diode D3 refers to a transient voltage suppression device used for overvoltage protection. It can be implemented using silicon-based TVS diodes or polymer-based protection devices, and its purpose is to absorb electrostatic discharge and transient voltage surge energy.

[0115] The fifteenth capacitor C15 and the sixteenth capacitor C16 refer to the decoupling capacitor combination connected in parallel between the power supply pin and ground. This combination can be achieved by using ceramic capacitors of different capacitance values ​​connected in parallel, with the aim of constructing a multi-stage power supply noise filtering network.

[0116] In this embodiment, the output buffer module 50 directly receives the output of the fourth differential signal through the +IN pin of the second operational amplifier U5, utilizing its high input impedance to avoid impedance mismatch during signal transmission. The power supply configuration of the V+ and V- pins together establishes a stable operating voltage environment, preventing power fluctuations from interfering with signal conversion. The fourteenth resistor R14 between the OUT and -IN pins forms precise negative feedback control, maintaining the operational amplifier in the linear region to eliminate phase distortion. The fourteenth capacitor C14 connected to the OUT pin bypasses residual high-frequency interference components to ground, preventing noise from superimposing on the output signal. The fifteenth resistor R15 acts as an output current limiting element to achieve impedance matching and ensure signal transmission integrity. The third bidirectional TVS suppression diode D3 constructs a bidirectional overvoltage protection channel between the output and ground, promptly dissipating electrostatic discharge or surge voltage energy. The fifteenth capacitor C15 and the sixteenth capacitor C16 connected to the V+ pin filter out low-frequency ripple and high-frequency noise on the power line through a parallel grounding structure, stabilizing the core power supply voltage. The above components work together through signal path optimization, noise suppression, and overvoltage protection to improve the anti-interference capability and long-term reliability of the single-ended output signal.

[0117] For example, the second operational amplifier U5 uses a general-purpose dual operational amplifier chip LM358, the fourteenth capacitor C14 uses a ceramic capacitor with good high-frequency characteristics, the third bidirectional TVS suppression diode D3 uses a standard package transient voltage suppression diode, and the fifteenth capacitor C15 and the sixteenth capacitor C16 use ceramic capacitors of different dielectric types connected in parallel to cover wideband noise suppression requirements.

[0118] In summary, the anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure provided in this embodiment achieves preliminary signal amplification and filtering through a differential input module, eliminates common-mode interference by combining a common-mode rejection module, and dynamically adjusts the signal gain using a programmable gain amplifier module. Finally, after low-pass filtering and output buffering, it effectively addresses the weak characteristics of the pressure sensor output signal and external interference problems, effectively suppresses external electromagnetic interference and common-mode noise, and improves the stability and accuracy of signal transmission. The programmable gain amplifier enables flexible adjustment of circuit parameters, enhances the circuit's adaptability to different operating conditions, improves the versatility of the signal conditioning circuit, and is compatible with various types of pressure sensors.

[0119] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A signal conditioning circuit for an anti-interference pressure sensor based on a differential amplifier structure, characterized in that, include: The differential input module is used to receive the differential signal output by the pressure sensor, and amplify and filter the output differential signal to obtain the first differential signal. A common-mode rejection module, electrically connected to the differential input module, is used to suppress the common-mode signal in the first differential signal to obtain a second differential signal; A programmable gain amplifier module, electrically connected to the common-mode rejection module, is used to amplify the second differential signal with a programmable gain to obtain a third differential signal; A low-pass filter module, electrically connected to the programmable gain amplifier module, is used to filter out high-frequency noise in the third differential signal to obtain a fourth differential signal; The output buffer module is electrically connected to the low-pass filter module and is used to convert the fourth differential signal into a single-ended signal before outputting it.

2. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 1, characterized in that, The differential input module includes a first capacitor C1, a second capacitor C2, and a first inductor L1; One end of the first capacitor C1 is electrically connected to the positive terminal of the differential signal output by the pressure sensor, and the other end is electrically connected to one end of the first resistor R1, one end of the third capacitor C3, and the V+IN pin of the first instrumentation amplifier U1; the V-IN pin of the first instrumentation amplifier U1 is electrically connected to the end of the third capacitor C3 away from the first capacitor C1, the end of the first resistor R1 away from the first capacitor C1, and one end of the second capacitor C2; the end of the second capacitor C2 away from the first resistor R1 is electrically connected to the negative terminal of the differential signal output by the pressure sensor and one end of the second resistor R2; the end of the second resistor R2 away from the second capacitor C2 is grounded; A third resistor R3 is connected in series between the two RG pins of the first instrumentation amplifier U1; the V+ pin of the first instrumentation amplifier U1 is connected to an external positive DC voltage; the V+ pin and REF pin of the first instrumentation amplifier U1 are grounded; the VO pin of the first instrumentation amplifier U1 is electrically connected to a second inductor L2; the end of the second inductor L2 away from the first instrumentation amplifier U1 is electrically connected to one end of a fourth capacitor C4 and serves as the positive terminal of the first differential signal; the end of the fourth capacitor C4 away from the second inductor L2 is grounded. One end of the first inductor L1 is grounded, and the other end is electrically connected to one end of the fifth capacitor C5 and serves as the negative terminal of the first differential signal; the end of the fifth capacitor C5 furthest from the first inductor L1 is grounded.

3. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 2, characterized in that, The differential input module also includes a first bidirectional TVS suppression diode D1, a second bidirectional TVS suppression diode D2, and a sixth capacitor C6; One end of the first bidirectional TVS suppression diode D1 is grounded, and the other end is electrically connected to one end of the first resistor R1 near the first capacitor C1. One end of the second bidirectional TVS suppression diode D2 is grounded, and the other end is electrically connected to the end of the first resistor R1 that is furthest from the first capacitor C1; One end of the sixth capacitor C6 is grounded, and the other end is electrically connected to the V+ pin of the first instrumentation amplifier U1.

4. The anti-interference pressure sensor signal conditioning circuit based on differential amplification structure according to claim 1, characterized in that, The common-mode suppression module includes a fourth resistor R4, a fifth resistor R5, and a second instrumentation amplifier U2; One end of the fourth resistor R4 is electrically connected to the positive terminal of the first differential signal, and the other end is electrically connected to the IN+ pin of the second instrumentation amplifier U2; one end of the fifth resistor R5 is electrically connected to the negative terminal of the first differential signal, and the other end is electrically connected to the IN- pin of the second instrumentation amplifier U2. A sixth resistor R6 is connected in series between the -RG pin and the +RG pin of the second instrumentation amplifier U2; the V+ pin of the second instrumentation amplifier U2 is connected to an external positive DC voltage, the OUT pin is used as the output terminal of the second differential signal, and the REF pin is electrically connected to a seventh resistor R7 and an eighth resistor R8. The end of the seventh resistor R7 furthest from the second instrumentation amplifier U2 is connected to a positive DC voltage; the end of the eighth resistor R8 furthest from the second instrumentation amplifier U2 is grounded.

5. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 4, characterized in that, The common-mode suppression module also includes a seventh capacitor C7; One end of the seventh capacitor C7 is grounded, and the other end is electrically connected to the V+ pin of the second instrumentation amplifier U2.

6. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 1, characterized in that, The programmable gain amplifier module includes a third instrumentation amplifier U3; The +IN pin of the third instrumentation amplifier U3 is electrically connected to the output terminal of the second differential signal; the A0 pin of the third instrumentation amplifier U3 is connected in series with the ninth resistor R9, and the A1 pin is connected in series with the tenth resistor R10; the end of the ninth resistor R9 away from the third instrumentation amplifier U3 is electrically connected to the end of the tenth resistor R10 away from the third instrumentation amplifier U3 and is externally connected to a positive DC voltage. The +VS pin of the third instrumentation amplifier U3 is connected to an external positive DC voltage, and the OUT pin is used as the output terminal of the third differential signal. The -IN pin, DGND pin, -VS pin, REF pin, and... of the third instrumentation amplifier U3 All pins are grounded.

7. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 6, characterized in that, The programmable gain amplifier module also includes an eighth capacitor C8 and a ninth capacitor C9; One end of the eighth capacitor C8 and one end of the ninth capacitor C9 are electrically connected to the +VS pin of the third instrumentation amplifier U3; the end of the eighth capacitor C8 away from the third instrumentation amplifier U3 is electrically connected to the end of the ninth capacitor C9 away from the third instrumentation amplifier U3 and grounded.

8. The anti-interference pressure sensor signal conditioning circuit based on differential amplification structure according to claim 1, characterized in that, The low-pass filter module includes a tenth capacitor C10, an eleventh resistor R11, and a first operational amplifier U4; One end of the tenth capacitor C10 is electrically connected to the output terminal of the third differential signal, and the other end is electrically connected to the eleventh resistor R11; the end of the eleventh resistor R11 away from the tenth capacitor C10 is electrically connected to the +IN pin of the first operational amplifier U4; the -IN pin of the first operational amplifier U4 is electrically connected to the twelfth resistor R12 and the thirteenth resistor R13. The twelfth resistor R12 is electrically connected to the eleventh capacitor C11 at the end furthest from the first operational amplifier U4; the eleventh capacitor C11 is grounded at the end furthest from the twelfth resistor R12; the OUT pin of the first operational amplifier U4 is electrically connected to the end of the thirteenth resistor R13 furthest from the -IN pin of the first operational amplifier U4 and serves as the output terminal of the fourth differential signal. The V+ pin of the first operational amplifier U4 is connected to an external positive DC voltage, and the V- pin is grounded.

9. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 8, characterized in that, The low-pass filter module also includes a twelfth capacitor C12 and a thirteenth capacitor C13; One end of the twelfth capacitor C12 and one end of the thirteenth capacitor C13 are electrically connected to the V+ pin of the first operational amplifier U4; the end of the twelfth capacitor C12 away from the first operational amplifier U4 is electrically connected to the end of the thirteenth capacitor C13 away from the first operational amplifier U4 and grounded.

10. The anti-interference pressure sensor signal conditioning circuit based on a differential amplifier structure according to claim 8, characterized in that, The output buffer module includes a second operational amplifier U5; The +IN pin of the second operational amplifier U5 is electrically connected to the output terminal of the fourth differential signal, the V+ pin is connected to an external positive DC voltage, and the V- pin is grounded; A fourteenth resistor R14 is connected in series between the OUT pin and the -IN pin of the second operational amplifier U5; The OUT pin of the second operational amplifier U5 is also electrically connected to the fourteenth capacitor C14, the fifteenth resistor R15, and the third bidirectional TVS suppression diode D3; The end of the fourteenth capacitor C14 furthest from the second operational amplifier U5 is grounded; The end of the fifteenth resistor R15 furthest from the second operational amplifier U5 serves as the output terminal of the single-ended signal. The end of the third bidirectional TVS suppression diode D3 that is furthest from the second operational amplifier U5 is grounded; The V+ pin of the second operational amplifier U5 is also electrically connected to the fifteenth capacitor C15 and the sixteenth capacitor C16; The end of the fifteenth capacitor C15 furthest from the second operational amplifier U5 is electrically connected to the end of the sixteenth capacitor C16 furthest from the second operational amplifier U5 and grounded.

Images