Two-wire system low bias voltage temperature drift amplification circuit and detection system

Abstract

The invention provides a two-wire system low bias voltage temperature drift amplification circuit and a detection system, and the circuit comprises an impedance conversion module which achieves the conversion from a high internal resistance alternating charge signal to a low internal resistance voltage signal through a field effect transistor; the constant current bias-voltage clamping module forms a voltage clamp through a Darlington tube and a Zener diode, and establishes stable direct current bias by means of a resistor, so that the circuit can stably work in a relatively wide driving current and working temperature range; and the gain adjustment-high-frequency signal suppression module adopts an RC first-order low-pass filter, realizes adjustment of voltage gain through an adjusting resistor, and combines an output signal with a constant current source to form two-wire system signal output, thereby realizing composite superposition of signal voltage and direct-current bias voltage. A two-wire system working mode is adopted, the structure is simple, the number of needed components is small, miniaturization integration is easy, and long-distance stable work can be achieved in the 175 DEG C high-temperature environment.

Description

Technical Field

[0001] This invention relates to the field of piezoelectric sensor conditioning circuit technology, and in particular to a two-wire low bias voltage temperature drift amplifier circuit and detection system. Background Technology

[0002] Vibration measurement is a crucial technology in applications such as aero-engines and deep-earth oil exploration equipment. Currently, piezoelectric accelerometers, which output electric charge signals, are commonly used for vibration measurement in high-temperature environments, offering excellent performance. Additionally, IEPE (Integrated Electronics Piezo-Electric) sensors are widely used, featuring built-in integrated amplifier circuits that directly convert electric charge signals into low-impedance voltage signals. However, this technology has the following main drawbacks:

[0003] 1. As a high-impedance signal, charge signals are easily affected by external environmental interference; IEPE type sensors are mainly limited by the circuit operating temperature, and the length of the signal transmission cable is restricted, making it difficult to achieve long-distance transmission.

[0004] 2. In traditional IEPE voltage amplification or charge amplification circuit structures, the constant current source input makes it difficult to determine the circuit's operating voltage, and the bias voltage is prone to drift with temperature, making it impossible to ensure that the sensor's range meets actual requirements. When the input equivalent charge far exceeds the preset measurement range of the charge amplifier, it can easily lead to clipping distortion in the charge amplifier, or even deep saturation.

[0005] 3. When using integrated operational amplifiers and other amplifier circuit structures, the design and implementation of operational amplifiers in high-temperature environments is more difficult, and the overall circuit structure is complex, which is not conducive to system miniaturization.

[0006] Of course, the same problems exist when amplifying signals from other devices that output charge signals; therefore, improving accuracy, increasing the dynamic range of amplifier circuits, and miniaturizing them have become some of the problems that need to be solved by those skilled in the art.

[0007] It should be noted that the above description of the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of the present invention and facilitating understanding by those skilled in the art. It should not be assumed that the above technical solutions are known to those skilled in the art simply because they have been described in the background section of this invention. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a two-wire low bias voltage temperature drift amplifier circuit and detection system to solve the problems of high noise, small dynamic range and complex structure in the prior art.

[0009] To achieve the above and other related objectives, the present invention provides a two-wire low-bias voltage temperature drift amplifier circuit, wherein the two-wire low-bias voltage temperature drift amplifier circuit comprises at least:

[0010] Impedance conversion module, gain adjustment-high frequency signal suppression module, and constant current bias-voltage clamping module;

[0011] The impedance conversion module acquires the high-impedance charge signal provided by the input module and converts the charge signal into a low-impedance signal; wherein, the input module generates the charge signal based on the change in capacitance;

[0012] The gain adjustment-high frequency signal suppression module is connected to the impedance conversion module, which adjusts the gain of the impedance-converted signal and suppresses the signal influence of the input module at the resonant frequency to broaden the bandwidth.

[0013] The constant current bias-voltage clamping module converts the constant current source into a stable DC operating point and provides it to the impedance conversion module and the gain adjustment-high frequency signal suppression module, so as to achieve a constant bias voltage of the built-in circuit and output the amplified low impedance signal through the IEPE interface.

[0014] Optionally, the impedance conversion module includes a first resistor, a second resistor, and a junction field-effect transistor;

[0015] The first end of the first resistor serves as the input terminal of the impedance conversion module, and the second end is grounded.

[0016] The gate of the junction field-effect transistor is connected to the first terminal of the first resistor, the source is grounded via the second resistor, and the drain serves as the output terminal of the impedance conversion module.

[0017] Alternatively, the frequency characteristics of the first-order RC network formed by the impedance transformation module and the input module satisfy the following relationship:

[0018] ;

[0019] in, R is the cutoff frequency of the input module and the impedance transformation module at -3dB attenuation. pe C is the equivalent resistance of the input module. pe R1 is the equivalent capacitance of the input module, and R2 is the resistance value of the first resistor.

[0020] Alternatively, the gain adjustment-high frequency signal suppression module includes a third resistor and a first capacitor;

[0021] The first end of the third resistor serves as the input of the gain adjustment-high frequency signal suppression module and is connected to the output of the impedance conversion module. The second end of the third resistor serves as the output of the gain adjustment-high frequency signal suppression module and is connected to the output of the two-wire low bias voltage temperature drift amplifier circuit.

[0022] The first capacitor is connected in parallel across the third resistor.

[0023] Alternatively, the frequency characteristics of the first-order RC network of the gain adjustment-high-frequency signal suppression module satisfy the following relationship:

[0024] ;

[0025] in, R3 is the cutoff frequency of the gain adjustment-high frequency signal suppression module at 3dB attenuation, C1 is the resistance value of the third resistor, and C1 is the capacitance value of the first capacitor.

[0026] Alternatively, the constant current bias-voltage clamping module includes an NPN Darlington transistor and a Zener diode;

[0027] The cathode of the Zener diode is connected to the emitter of the NPN Darlington transistor, and the anode is grounded.

[0028] The base of the NPN Darlington transistor is connected to the output of the impedance conversion module, and the collector is connected to the output of the two-wire low-bias temperature drift amplifier circuit.

[0029] Alternatively, the bias voltage V output by the constant current bias-voltage clamping module bias The following relationship must be satisfied:

[0030] ;

[0031] Among them, V be V is the base-emitter turn-on voltage of the NPN Darlington transistor. DZ I is the reverse conduction voltage of the Zener diode. D R1 is the drain current of the junction field-effect transistor, and R2 is the resistance value of the third resistor.

[0032] Alternatively, the NPN Darlington transistor can be replaced with a high-current-gain NPN transistor, wherein the current gain is not less than 10. 3 .

[0033] Alternatively, the junction field-effect transistor, the NPN Darlington transistor, and the Zener diode may all be chip-scale packages or surface-mount packages suitable for high-temperature environments.

[0034] Alternatively, the junction field-effect transistor, the NPN Darlington transistor, and the Zener diode are made of silicon-based, SOI, or wide-bandgap semiconductor materials.

[0035] To achieve the above and other related objectives, the present invention also provides a detection system, the detection system comprising at least:

[0036] Input module, constant current source and the above two-wire low bias voltage temperature drift amplifier circuit;

[0037] The input module outputs a corresponding charge signal based on the capacitance change caused by an external signal.

[0038] The constant current source is connected to the output terminal of the two-wire low bias voltage temperature drift amplifier circuit, so that the two-wire low bias voltage temperature drift amplifier circuit can achieve a constant bias voltage of the built-in circuit based on the constant current source.

[0039] The two-wire low-bias voltage temperature drift amplifier circuit is connected to the output of the input module to amplify the charge signal.

[0040] Optionally, the input module is a piezoelectric vibration sensor.

[0041] Alternatively, the input module is a sensor made of one of the piezoelectric materials selected from aluminum nitride, scandium-doped aluminum nitride, lithium niobate, lead zirconate titanate, and lithium tantalate.

[0042] As described above, the two-wire low-bias voltage temperature drift amplifier circuit and vibration detection system of the present invention have the following beneficial effects:

[0043] 1. The two-wire low bias voltage temperature drift amplifier circuit and detection system of the present invention have a large dynamic response range, and can still maintain a frequency response range of 5Hz to 10kHz in an environment of 175℃.

[0044] 2. The two-wire low bias voltage temperature drift amplifier circuit and detection system of the present invention have a small number of components, good stability, can be integrated and miniaturized, and have extremely low noise.

[0045] 3. The two-wire low-bias voltage temperature drift amplifier circuit and detection system of the present invention have high input impedance, reaching 10. 8 Ω~10 10 Ω.

[0046] 4. The two-wire low bias voltage temperature drift amplifier circuit and detection system of the present invention have a wide constant current excitation current range, generally operating in the range of +2mA to +20mA, and the bias voltage remains basically unchanged.

[0047] 5. The two-wire low bias voltage temperature drift amplifier circuit and detection system of the present invention can operate at a temperature of up to 175°C. The circuit components can be selected to withstand 175°C, and the bias voltage remains basically unchanged within the temperature range.

[0048] 6. The bias voltage of the two-wire low bias voltage temperature drift amplifier circuit and detection system of the present invention is independently controllable. Setting a low bias voltage can be applied to low bias voltage and low power consumption scenarios, while setting a high bias voltage can also be applied to high range and other shock-resistant scenarios.

[0049] 7. The first-order low-pass filter cutoff frequency of the two-wire low-bias voltage temperature drift amplifier circuit and detection system of the present invention is adjustable, which can suppress the influence of the piezoelectric sensor resonant frequency and broaden the bandwidth. Attached Figure Description

[0050] Figure 1 The diagram shown is a schematic of the two-wire low-bias voltage temperature drift amplifier circuit of the present invention.

[0051] Figure 2 The diagram shown is an equivalent circuit diagram of the input module of this invention.

[0052] Figure 3 The diagram shown is a structural schematic of the detection system of the present invention.

[0053] Figure 4 The diagram shows the gain curve of the present invention in the operating current range of 2mA-20mA.

[0054] Figure 5 The diagram shows the gain curve of the present invention within the operating temperature range of room temperature to 175°C.

[0055] Figure 6 The diagram shows a schematic representation of the detection system with a built-in charge amplifier circuit.

[0056] Figure 7 The diagram shows a comparison of the gain curves of the present invention and the comparative example at an operating temperature of 175°C.

[0057] Figure 8 The diagram shows a comparison of the effect of temperature on the bias voltage of the present invention and the comparative example.

[0058] Component designation explanation

[0059] 1-Two-wire low bias voltage temperature drift amplifier circuit; 11-Impedance conversion module; 12-Gain adjustment-high frequency signal suppression module; 13-Constant current bias-voltage clamping module; 2-Input module; 3-Constant current source; 4-Charge amplifier circuit. Detailed Implementation

[0060] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0061] Please see Figures 1-8 It should be noted that the illustrations provided in this embodiment are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0062] like Figure 1 As shown, the present invention provides a two-wire low-bias voltage temperature drift amplifier circuit 1, which includes:

[0063] Impedance conversion module 11, gain adjustment-high frequency signal suppression module 12 and constant current bias-voltage clamping module 13.

[0064] like Figure 1 As shown, the impedance conversion module 11 acquires the high-impedance charge signal provided by the input module 2 and converts the charge signal into a low-impedance signal.

[0065] Specifically, input module 2 generates and outputs the charge signal based on changes in capacitance, including but not limited to piezoelectric sensors, which will not be elaborated here. For example... Figure 2 As shown, input module 2 is a charge generator Q. pe Due to the internal equivalent capacitance C pe Due to the presence of distributed capacitance in the external connecting cable, its output can be equivalent to a voltage generator U. pe It also includes an equivalent resistance R. pe In the built-in circuit of input module 2, the distributed capacitance of the connecting cable is a constant. Therefore, the equivalent output voltage of input module 2 can be obtained as follows: , where C pe C represents the internal capacitance of input module 2. c This indicates the distributed capacitance of the connecting cable; the output signal of input module 2 has extremely high output impedance, typically around 10 for example. 9 Ω or above; the value should be determined based on the actual operating conditions.

[0066] Specifically, as an example, the impedance conversion module 11 includes a first resistor R1, a second resistor R2, and a junction field-effect transistor (JFET) J1. The first terminal of the first resistor R1 serves as the input terminal IN of the impedance conversion module 11, and the second terminal is grounded. The gate of the JFET J1 is connected to the first terminal of the first resistor R1 (i.e., the input terminal IN), the source is grounded via the second resistor R2, and the drain serves as the output terminal of the impedance conversion module 11. The first resistor R1 provides a DC voltage to the gate of the JFET J1; the second resistor R2 provides negative feedback to the JFET J1, enabling the source voltage of the JFET J1 to form a stable self-biased voltage. In practical applications, other circuit structures capable of converting high-impedance charge signals into low-impedance signals are also applicable to this invention and are not limited to this example.

[0067] Specifically, in this example, the first resistor R1 in the impedance conversion module 11 and the equivalent resistor R in the input module 2 are... pe and equivalent capacitance C pe A first-order RC network with low-frequency signal attenuation function is constructed, and its frequency characteristics satisfy the following relationship:

[0068] (1);

[0069] in, R is the cutoff frequency of input module 2 and impedance conversion module 11 at -3dB attenuation. pe C is the equivalent resistance of input module 2. pe R1 is the equivalent capacitance of input module 2, and R1 is the resistance value of the first resistor.

[0070] like Figure 1 As shown, the gain adjustment-high frequency signal suppression module 12 is connected to the impedance conversion module 11 to adjust the gain of the impedance-converted signal and suppress the signal influence of the input module 2 at the resonant frequency, so as to broaden the bandwidth.

[0071] Specifically, in this example, the gain adjustment-high frequency signal suppression module 12 includes a third resistor R3 and a first capacitor C1. The first end of the third resistor R3 serves as the input terminal of the gain adjustment-high frequency signal suppression module 12 and is connected to the output terminal (drain of the junction field-effect transistor J1) of the impedance conversion module 11. The second end of the third resistor R3 serves as the output terminal of the gain adjustment-high frequency signal suppression module 12 and is connected to the output terminal OUT of the two-wire low-bias voltage temperature drift amplifier circuit 1. The first capacitor C1 is connected in parallel across the third resistor R3. The third resistor R3 is used to adjust the voltage amplification capability; the third resistor R3 and the first capacitor C1 together form a first-order low-pass filter to suppress the excessive high-frequency gain caused by the resonant frequency of the input module 2, thereby widening the normal operating bandwidth of the input module 2. In practical applications, the specific structure of the gain adjustment-high frequency signal suppression module 12 can be adjusted according to the structure of the impedance conversion module 11, and is not limited to this example.

[0072] Specifically, in this example, the third resistor R3 and the first capacitor C1 in the gain adjustment-high frequency signal suppression module 12 form a first-order RC network with high frequency signal attenuation function, and its frequency characteristics satisfy the following relationship:

[0073] (2);

[0074] in, R3 is the cutoff frequency of the gain adjustment-high frequency signal suppression module 12 at 3dB attenuation, C1 is the resistance value of the third resistor, and C1 is the capacitance value of the first capacitor.

[0075] like Figure 1 As shown, the constant current bias-voltage clamping module 13 converts the external constant current source into a stable DC operating point and provides it to the impedance conversion module 11 and the gain adjustment-high frequency signal suppression module 12 to achieve a constant bias voltage for the built-in circuit and outputs the amplified low impedance signal through the IEPE interface.

[0076] Specifically, in this example, the constant current bias-voltage clamping module 13 includes an NPN Darlington transistor T1 and a Zener diode D1. The cathode of the Zener diode D1 is connected to the emitter of the NPN Darlington transistor T1, and the anode is grounded. The base of the NPN Darlington transistor T1 is connected to the output terminal of the impedance conversion module 11 (i.e., the connection node between the junction field-effect transistor J1 and the third resistor R3), and the collector is connected to the output terminal OUT of the two-wire low-bias temperature drift amplifier circuit 1. In practical applications, any circuit structure that can provide a constant bias voltage to the internal circuitry of the two-wire low-bias temperature drift amplifier circuit 1 is applicable to this invention and is not limited to this example.

[0077] More specifically, in this example, the bias voltage V output by the constant current bias-voltage clamping module 13bias (The circuit operates between the output terminal OUT of the two-wire low-bias temperature drift amplifier circuit 1 and the reference ground) and satisfies the following relationship:

[0078] (3);

[0079] Among them, V be V is the base-emitter turn-on voltage of the NPN Darlington transistor T1. DZ I is the reverse conduction voltage of Zener diode D1. D R1 is the drain current of junction field-effect transistor J1, and R3 is the resistance value of the third resistor.

[0080] In another implementation of the present invention, the NPN Darlington transistor T1 can be replaced with a high-current-gain NPN transistor. For example, the current gain of this high-current-gain NPN transistor is not less than 10. 3 , including but not limited to 10 4 2×10 4 5×10 4 8×10 4 10 5 5×10 4 I will not go into detail here.

[0081] As an example, preferably, the junction field-effect transistor J1, the NPN Darlington transistor T1, and the Zener diode D1 are all chip-level packages or surface-mount packages suitable for high-temperature environments; in actual use, the corresponding packaging method can be set as needed, and different packaging methods can be used for each device.

[0082] As an example, preferably, the junction field-effect transistor J1, the NPN Darlington transistor T1, and the Zener diode D1 are semiconductor materials suitable for high-temperature scenarios, such as silicon-based, SOI, or wide-bandgap semiconductor materials; in actual use, the appropriate materials can be set as needed, and each device can also be made of different materials.

[0083] In this embodiment, the value of the first resistor R1 ranges from 10 MΩ to 10 GΩ; the values ​​of the second resistor R2 and the third resistor R3 both range from 10 kΩ to 1000 kΩ; and the value of the first capacitor C1 ranges from 10 pF to 1000 pF. In actual use, the resistance values ​​of each resistor can be set as needed, and are not limited to this embodiment.

[0084] like Figure 3 As shown, the present invention also provides a detection system, which includes:

[0085] Input module 2, constant current source 3, and the two-wire low bias voltage temperature drift amplifier circuit 1 of the present invention.

[0086] like Figure 3 As shown, input module 2 outputs a corresponding charge signal based on the capacitance change caused by the external signal.

[0087] Specifically, in this embodiment, the input module 2 is configured as a piezoelectric vibration sensor for vibration measurement. In practical use, the input module 2 can be a piezoelectric sensor or any device that can cause a change in capacitance based on external signals (including but not limited to vibration, pressure, displacement, and humidity, which will not be elaborated here).

[0088] Specifically, the input module 2 includes, but is not limited to, a sensor made of one of the following piezoelectric materials: aluminum nitride, scandium-doped aluminum nitride, lithium niobate, lead zirconate titanate, and lithium tantalate.

[0089] like Figure 3 As shown, the constant current source 3 is connected to the output terminal OUT of the two-wire low bias voltage temperature drift amplifier circuit 1, so that the two-wire low bias voltage temperature drift amplifier circuit 1 can achieve a constant bias voltage of the built-in circuit based on the constant current source 3.

[0090] Specifically, in this embodiment, the constant current source 3 is an IEPE constant current source; one end of the constant current source 3 is connected to the output terminal OUT of the two-wire low bias voltage temperature drift amplifier circuit 1, and the other end is grounded.

[0091] like Figure 3 As shown, a two-wire low-bias voltage temperature drift amplifier circuit 1 is connected to the output terminal of the input module 2 to amplify the charge signal output by the input module 2. It includes an impedance conversion module 11, a gain adjustment-high-frequency signal suppression module 12, and a constant current bias-voltage clamping module 13. The impedance conversion module 11 performs impedance transformation on the charge signal; the gain adjustment-high-frequency signal suppression module 12 adjusts the voltage gain to regulate the sensitivity of the input module 2 and suppresses interference at the resonant frequency of the input module 2, thereby widening the operating bandwidth; the constant current bias-voltage clamping module 13 converts the constant current source 3 drive into a constant DC voltage bias, enabling the circuit to maintain stable operation over a wide driving current range; see the above for the specific structure.

[0092] The working principle of the two-wire low-bias voltage temperature drift amplifier circuit 1 (two-wire built-in voltage amplifier circuit) of the present invention is as follows:

[0093] The two-wire low-bias voltage temperature drift amplifier circuit uses a constant current source for two-wire power supply. First, the input current (e.g., 2mA-20mA) of the constant current source 3 is fed into the constant current bias-voltage clamping module 13 to achieve stable DC bias for the two-wire low-bias voltage temperature drift amplifier circuit. The charge signal is fed into the impedance conversion module 11 to achieve impedance conversion; then it is fed into the first-order low-pass filter inside the gain adjustment-high-frequency signal suppression module 12 for filtering, achieving input module resonant frequency suppression and bandwidth widening functions.

[0094] The two-wire low-bias-voltage temperature drift amplifier circuit of this invention solves two problems: First, it addresses the difficulty in accurately designing and stably controlling the operating bias voltage in IEPE two-wire circuits, thus ensuring that the sensor range meets actual requirements. Precise design and stable control of the bias voltage are achieved by selecting matched Darlington transistors and Zener diodes. Second, it overcomes the technical challenges of complex structures and miniaturization of integrated operational amplifiers and other amplifier circuits in high-temperature environments. In this invention, a junction field-effect transistor J1, an NPN Darlington transistor T1, and a Zener diode D1 jointly perform signal amplification, realizing impedance transformation, gain adjustment, and IEPE standard output of the output signal from input module 2. The two-wire low-bias-voltage temperature drift amplifier circuit 1 of this invention has a simple structure, high reliability, and facilitates the selection and integration of high-temperature components, providing a feasible technical path for realizing miniaturized high-temperature detection systems (such as piezoelectric sensors).

[0095] The performance of the two-wire low-bias-voltage temperature drift amplifier circuit 1 of the present invention will be described below with a specific example; in this example, the parameters of each component are as follows:

[0096] The equivalent capacitance C of input module 2 pe The static capacitance is 0.6nF; the equivalent resistance R of input module 2 is... peThe static resistance decreases with increasing temperature, and is set to 72MΩ-5000MΩ; the first resistor R1 is set to 500MΩ; the second resistor R2 is set to 30kΩ; the third resistor R3 is set to 800kΩ; the first capacitor C1 is set to 20pF; the junction field-effect transistor J1 is a 2N4117A; the NPN Darlington transistor T1 is a ZTX614; and the Zener diode D1 is a 1N4614. In this scheme, the input module 2 uses a piezoelectric vibration sensor with a resonant frequency of 14kHz, a charge sensitivity of 0.6pC / g, a static capacitance of 0.6nF, and a static resistance of 5000MΩ. The two-wire piezoelectric sensor requires a working temperature range of room temperature to 175°C, a working current range of 2mA-20mA, a power supply voltage of 24V to 30V, a full-temperature frequency response range of 5Hz to 10kHz (3dB), a voltage sensitivity of 10mV / g, and a measurement range of 500g. According to the requirements of this invention, the high-frequency signal attenuation 3dB has a cutoff frequency of 10kHz, ensuring the highest frequency response of the piezoelectric vibration sensor meets the 10kHz requirement. According to the requirements of this invention, the low-frequency signal attenuation 3dB has a maximum cutoff frequency of 4.2Hz, ensuring the lowest frequency response of the piezoelectric vibration sensor meets the 5Hz requirement. According to the requirements of this invention, with a measurement range of 500g and a sensitivity of 10mV / g, the voltage range is determined to be ±5V. According to equation (3), the output voltage is:

[0097] ;

[0098] Among them, V D I is the drain voltage value of junction field-effect transistor J1. D This is the drain current value of junction field-effect transistor J1.

[0099] Selecting high-temperature junction field-effect transistors, Darlington transistors, and Zener diodes, the original voltage sensitivity U of the piezoelectric vibration sensor... pe The equivalent voltage (i.e., 1mV / g) is 1mV / g; therefore, according to the requirements of the present invention, given the selection of a high-temperature junction field-effect transistor, a Darlington transistor, and a Zener diode, the value of the third resistor R3 is adjusted. Figure 4 As can be seen, within the operating current range of 2mA-20mA, the gain remains essentially constant at 24.94dB, while the bias voltage is approximately 15V; Figure 5 As can be seen, within the operating temperature range of room temperature to 175℃, the gain changes from 24.94dB to 23.48dB, while the bias voltage remains essentially unchanged. Therefore, the full-temperature range sensitivity of the piezoelectric vibration sensor after amplification is greater than or equal to 15mV / g, which is sufficient for testing vibration intensity in high-temperature industrial environments such as aero-engines or deep-earth oil exploration equipment.

[0100] As a comparative example, such as Figure 6 As shown, a charge amplifier circuit 4 (including resistors R4, R5, R6, R7, R8, junction transistor J2, and PNP transistor T2) amplifies the charge signal output from input module 2. The equivalent capacitance C of input module 2... pe The static capacitance is 0.6nF; the equivalent resistance R of input module 2 is... pe The static resistance decreases with increasing temperature, and is set to 72MΩ-5000MΩ; the fourth resistor R4 is set to 500MΩ; the fifth resistor R5 is set to 4.99kΩ; the sixth resistor R6 is set to 8.06kΩ; the seventh resistor R7 is set to 8.06kΩ; the eighth resistor R8 is set to 499Ω; the second capacitor C2 is set to 60pF; the junction field-effect transistor J2 is selected as 2N4117A; the PNP transistor T2 is selected as BC557B. In this scheme, the working principle of the charge amplifier circuit 4 is as follows: Junction field-effect transistor J2, fifth resistor R5, and sixth resistor R6 form the input stage of the two-wire built-in charge amplifier circuit 4, collecting the high-impedance charge signal from input module 2 and realizing impedance conversion; PNP transistor T2 serves as the output stage of the two-wire built-in charge amplifier circuit 4, improving the driving capability of the amplifier circuit; fourth resistor R4, seventh resistor R7, eighth resistor R8, and second capacitor C2 form the feedback loop of the two-wire built-in charge amplifier circuit 4, connected to the IEPE output interface, converting the charge signal into a voltage signal and providing DC bias and DC feedback path to avoid saturation. Due to its 3dB low-frequency signal attenuation, the corner frequency is... The second capacitor C2 is set to 60pF, so that its frequency response is basically consistent with that of the two-wire low-bias voltage temperature drift amplifier circuit 1 of this invention, which facilitates comparison of amplitude-frequency characteristic curves. The comparison results are as follows: Figure 7 As shown, at an operating temperature of 175°C, the gain of charge amplifier circuit 4 is 15.73 dB, which is much smaller than the gain of the two-wire low bias voltage temperature drift amplifier circuit 1 of this invention, which is 23.48 dB. Comparing the degree to which the bias voltage of the two circuits is affected by temperature, the results are as follows... Figure 8 As shown, since the voltage divider circuit in charge amplifier circuit 4 uses a resistor divider, the magnitude of the current flowing into the voltage divider circuit cannot be determined. The bias voltage of charge amplifier circuit 4 fluctuates significantly, ranging from 11.03V to 15.98V. In contrast, the bias voltage in the two-wire low-bias-voltage temperature drift amplifier circuit 1 of this invention remains essentially constant, fluctuating between 14.99V and 15.42V. Therefore, the two-wire low-bias-voltage temperature drift amplifier circuit 1 of this invention exhibits higher gain and a more stable operating voltage over a wider temperature range.

[0101] In summary, this invention provides a two-wire low-bias-voltage temperature drift amplifier circuit and detection system, comprising: an impedance conversion module, a constant current bias-voltage clamping module, and a gain adjustment-high-frequency signal suppression module. The impedance conversion module utilizes a field-effect transistor (FET) to convert a high-internal-resistance alternating charge signal to a low-internal-resistance voltage signal. The constant current bias-voltage clamping module uses a Darlington transistor and a Zener diode to form a voltage clamp, and establishes a stable DC bias with the aid of a resistor, enabling the circuit to operate stably over a wide range of drive currents and operating temperatures. The gain adjustment-high-frequency signal suppression module employs an RC first-order low-pass filter, adjusting the voltage gain by regulating the resistor, and combining the output signal with a constant current source to form a two-wire signal output, achieving the superposition of the signal voltage and the DC bias voltage. Since the drain potential of the FET remains essentially constant, the bias voltage remains essentially unchanged under different drive currents and temperatures, effectively reducing the impact of bias voltage drift on the sensor's range. This invention adopts a two-wire operating mode, has a simple structure, requires fewer components, is easy to miniaturize and integrate, and is suitable for long-distance stable operation in high-temperature environments up to 175℃. Therefore, this invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0102] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A two-wire low-bias voltage temperature drift amplifier circuit, characterized in that, The two-wire low-bias voltage temperature drift amplifier circuit includes at least: Impedance conversion module, gain adjustment-high frequency signal suppression module, and constant current bias-voltage clamping module; The impedance conversion module acquires the high-impedance charge signal provided by the input module and converts the charge signal into a low-impedance signal; wherein, the input module generates the charge signal based on the change in capacitance; The gain adjustment-high frequency signal suppression module is connected to the impedance conversion module, which adjusts the gain of the impedance-converted signal and suppresses the signal influence of the input module at the resonant frequency to broaden the bandwidth. The constant current bias-voltage clamping module converts the constant current source into a stable DC operating point and provides it to the impedance conversion module and the gain adjustment-high frequency signal suppression module, so as to achieve a constant bias voltage of the built-in circuit and output the amplified low impedance signal through the IEPE interface.

2. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 1, characterized in that: The impedance conversion module includes a first resistor, a second resistor, and a junction field-effect transistor; The first end of the first resistor serves as the input terminal of the impedance conversion module, and the second end is grounded. The gate of the junction field-effect transistor is connected to the first terminal of the first resistor, the source is grounded via the second resistor, and the drain serves as the output terminal of the impedance conversion module.

3. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 2, characterized in that: The frequency characteristics of the first-order RC network formed by the impedance transformation module and the input module satisfy the following relationship: ； in, R is the cutoff frequency of the input module and the impedance transformation module at -3dB attenuation. pe C is the equivalent resistance of the input module. pe R1 is the equivalent capacitance of the input module, and R2 is the resistance value of the first resistor.

4. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 2, characterized in that: The gain adjustment-high frequency signal suppression module includes a third resistor and a first capacitor; The first end of the third resistor serves as the input of the gain adjustment-high frequency signal suppression module and is connected to the output of the impedance conversion module. The second end of the third resistor serves as the output of the gain adjustment-high frequency signal suppression module and is connected to the output of the two-wire low bias voltage temperature drift amplifier circuit. The first capacitor is connected in parallel across the third resistor.

5. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 4, characterized in that: The frequency characteristics of the first-order RC network of the gain adjustment-high-frequency signal suppression module satisfy the following relationship: ； in, R3 is the cutoff frequency of the gain adjustment-high frequency signal suppression module at 3dB attenuation, C1 is the resistance value of the third resistor, and C1 is the capacitance value of the first capacitor.

6. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 4, characterized in that: The constant current bias-voltage clamping module includes an NPN Darlington transistor and a Zener diode; The cathode of the Zener diode is connected to the emitter of the NPN Darlington transistor, and the anode is grounded. The base of the NPN Darlington transistor is connected to the output of the impedance conversion module, and the collector is connected to the output of the two-wire low-bias temperature drift amplifier circuit.

7. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 6, characterized in that, The bias voltage V output by the constant current bias-voltage clamping module bias The following relationship must be satisfied: ； Among them, V be V is the base-emitter turn-on voltage of the NPN Darlington transistor. DZ I is the reverse conduction voltage of the Zener diode. D R1 is the drain current of the junction field-effect transistor, and R2 is the resistance value of the third resistor.

8. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 6 or 7, characterized in that: The NPN Darlington transistor is replaced with a high-current-gain NPN transistor, wherein the current gain is not less than 10. 3 .

9. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 6, characterized in that: The junction field-effect transistor, the NPN Darlington transistor, and the Zener diode are all packaged in chip-level or surface-mount packages suitable for high-temperature environments.

10. The two-wire low-bias voltage temperature drift amplifier circuit according to claim 6, characterized in that: The junction field-effect transistor, the NPN Darlington transistor, and the Zener diode are made of silicon-based, SOI, or wide-bandgap semiconductor materials.

11. A detection system, characterized in that, The detection system includes at least: Input module, constant current source and two-wire low bias voltage temperature drift amplifier circuit as described in any one of claims 1-10; The input module outputs a corresponding charge signal based on the capacitance change caused by an external signal. The constant current source is connected to the output terminal of the two-wire low bias voltage temperature drift amplifier circuit, so that the two-wire low bias voltage temperature drift amplifier circuit can achieve a constant bias voltage of the built-in circuit based on the constant current source. The two-wire low-bias voltage temperature drift amplifier circuit is connected to the output of the input module to amplify the charge signal.

12. The vibration detection system according to claim 11, characterized in that: The input module is a piezoelectric vibration sensor.

13. The vibration detection system according to claim 11 or 12, characterized in that: The input module is a sensor made of one of the following piezoelectric materials: aluminum nitride, scandium-doped aluminum nitride, lithium niobate, lead zirconate titanate, and lithium tantalate.

Images