CN117713746B - A piezoelectric signal conditioning circuit - Google Patents

Abstract

The invention provides a piezoelectric signal conditioning circuit, which belongs to the field of piezoelectric sensors, and comprises a high-frequency signal attenuation circuit module, a frequency-selecting filter and a power supply module, wherein the high-frequency signal attenuation circuit module is used for acquiring an equivalent voltage signal output by a piezoelectric sensor and performing frequency-selecting filter processing on the equivalent voltage signal and an electromagnetic pulse signal coupled with the equivalent voltage signal; the impedance transformation and IEPE interface circuit module is used for performing impedance transformation, signal amplification and gain adjustment on the equivalent voltage signal subjected to frequency selection filtering treatment, and outputting the treated equivalent voltage signal in an IEPE interface form; and the anti-electromagnetic pulse interference circuit module is used for carrying out filtering processing on the received voltage signal. The invention realizes the multi-slave functions of impedance transformation, signal amplification and gain adjustment, high-frequency signal attenuation, electromagnetic pulse interference resistance, IEPE interface provision and the like of the electric charge output by the piezoelectric sensor, and solves the problems that the signal amplification circuit of the traditional piezoelectric sensor has a complex structure and cannot perform frequency adjustment.

Description

A piezoelectric signal conditioning circuit

Technical Field

The invention belongs to the field of piezoelectric sensors, and in particular relates to a piezoelectric signal conditioning circuit.

Background technique

The output of a piezoelectric sensor is a charge signal with extremely high impedance, and the output impedance is generally above 10 ⁹ Ω. For example, the output signal of a piezoelectric accelerometer is a charge signal, and the amplitude of the charge signal is usually proportional to the vibration acceleration value of the object being measured, and the frequency and phase of the two are consistent. Since the output impedance of the piezoelectric sensor is extremely high and the output signal is a charge signal, the signal cannot be directly collected by the signal acquisition device, and impedance transformation and signal amplification are required before collection. If the vibration acceleration of the object being measured is to be obtained through this vibration acceleration sensor, it is necessary to convert the acceleration charge signal into an acceleration voltage signal, that is, to achieve pC-mV conversion, but this involves the functions of impedance transformation, gain adjustment, and high-frequency signal attenuation.

Summary of the invention

In view of the above-mentioned deficiencies in the prior art, the present invention provides a piezoelectric signal conditioning circuit. The piezoelectric signal conditioning circuit of the present invention is composed of two field effect transistors and a small number of peripheral resistors and capacitors, which realizes the impedance transformation, gain adjustment, high-frequency signal attenuation, anti-electromagnetic pulse interference and IEPE standard interface functions of the piezoelectric sensor output signal, and solves the problem that the traditional piezoelectric sensor signal amplification circuit has a complex structure and cannot perform frequency adjustment.

The technical solution of the present invention is: a piezoelectric signal conditioning circuit, comprising:

A high-frequency signal attenuation circuit module is used to obtain the equivalent voltage signal output by the piezoelectric sensor and perform frequency selection filtering on the equivalent voltage signal and its coupled electromagnetic pulse signal;

The impedance conversion and IEPE interface circuit module is used to perform impedance conversion, signal amplification and gain adjustment on the equivalent voltage signal after the frequency selection and filtering processing, and output the processed equivalent voltage signal to the anti-electromagnetic pulse interference circuit module through the IEPE interface;

The anti-electromagnetic pulse interference circuit module is used to filter the received voltage signal.

The beneficial effects of the present invention are as follows: the present invention utilizes an amplifier circuit composed of a field effect tube and a relatively small number of peripheral resistors and capacitors to realize impedance transformation, gain adjustment, high-frequency signal attenuation, anti-electromagnetic pulse interference and IEPE standard interface functions of the output signal of the piezoelectric sensor, solves the problem that the piezoelectric sensor signal amplifier circuit has a complex structure and cannot perform frequency adjustment, and firstly solves the problem that the existing circuit cannot correct and adjust the frequency response of the piezoelectric sensor. At the same time, the present invention has an electromagnetic pulse signal suppression circuit, which can meet the use requirements in a complex electromagnetic environment, and the output adopts the IEPE output mode, and its implementation can reduce the output interface of the amplifier circuit.

Furthermore, the high-frequency signal attenuation circuit module includes a resistor R1 and a capacitor C2;

One end of the resistor R1 is connected to the external piezoelectric sensor through the coupling capacitor C1 and serves as the input terminal Vin of the piezoelectric signal conditioning circuit. The other end of the resistor R1 is respectively connected to one end of the capacitor C2 and the impedance transformation and IEPE interface circuit module; the other end of the capacitor C2 is connected to the impedance transformation and IEPE interface circuit module. The resistor R1 and the capacitor C2 form a resistor-capacitor network RC of the high-frequency signal attenuation circuit.

The beneficial effect of the above further scheme is: the equivalent voltage output by the piezoelectric sensor in the present invention is coupled input through the coupling capacitor C1, and then frequency-selectively filtered by a first-order low-pass filter composed of a resistor R1 and a capacitor C2, thereby achieving attenuation of the high-frequency signal of the piezoelectric sensor and increasing the frequency response range of the piezoelectric sensor.

Further, the impedance conversion and IEPE interface circuit module includes a junction field effect transistor Q1, a junction gate field effect transistor Q2, a bootstrap resistor R2, a resistor R3, a resistor R4 and a resistor R5;

One end of the bootstrap resistor R2 is respectively connected to the other end of the resistor R1 and the gate of the junction field effect transistor Q1, the source of the junction field effect transistor Q1 is connected to one end of the resistor R3, the drain of the junction field effect transistor Q1 is respectively connected to one end of the resistor R4 and the gate of the junction gate field effect transistor Q2, the source of the junction gate field effect transistor Q2 is connected to one end of the resistor R5, the drain of the junction gate field effect transistor Q2 is respectively connected to the other end of the resistor R4 and the anti-electromagnetic pulse interference circuit module, and the other end of the bootstrap resistor R2 is respectively connected to the other end of the capacitor C2, the other end of the resistor R3 and the other end of the resistor R5, and is grounded.

The beneficial effect of the above further scheme is that the present invention sends the equivalent voltage signal filtered by the high-frequency signal attenuation circuit module to a signal amplification circuit with an IEPE interface composed of a junction field effect transistor Q1 (JFET), a junction gate field effect transistor Q2 (MOS tube) and four peripheral resistors to achieve gain adjustment and impedance conversion functions.

Further, the anti-electromagnetic pulse interference circuit module includes a capacitor C3, a resistor R6 and a transient suppression diode D1;

One end of the resistor R6 is respectively connected to the drain of the junction gate field effect transistor Q2 and one end of the capacitor C3, the other end of the resistor R6 is respectively connected to the constant current source power supply terminal lin and the cathode of the transient suppression diode D1, and serves as the output terminal Vout of the piezoelectric conditioning circuit, the anode of the transient suppression diode D1 is respectively connected to the other end of the capacitor C3, the other end of the resistor R5, the other end of the resistor R3, the other end of the bootstrap resistor R2 and the other end of the capacitor C2, and is grounded.

The beneficial effect of the above further scheme is that the present invention utilizes the signal output end composed of the resistor R6, the capacitor C3 and the transient suppression diode D1 at the signal output end, that is, the electromagnetic pulse interference signal suppression circuit, to realize the IEPE circuit anti-electromagnetic pulse interference function.

Furthermore, the relationship between the RC network of the high-frequency signal attenuation circuit module and the frequency characteristic of the high-frequency signal attenuation circuit is as follows:

in, Indicates the cutoff frequency of the high-frequency signal attenuation circuit module at -3dB attenuation.

The beneficial effect of the above further scheme is: the equivalent voltage output by the piezoelectric sensor in the present invention is frequency-selectively filtered through an RC network, and the frequency signal in a specific frequency band is attenuated by adjusting the time constant of RC , thereby achieving attenuation of the high-frequency signal of the piezoelectric sensor and increasing the frequency response range of the piezoelectric sensor.

Furthermore, the expression of the gain of the junction field effect transistor Q1 is as follows:

in, Indicates the gain of the junction field effect transistor Q1, /> Represents the transconductance of the junction field effect transistor Q1.

The beneficial effect of the above further scheme is that the primary voltage signal amplification circuit composed of resistor R3, resistor R4 and junction field effect transistor Q1 in the present invention realizes primary amplification of the equivalent voltage signal output by the piezoelectric sensor output by the high-frequency signal attenuation circuit module.

Furthermore, the expression of the gain of the junction gate field effect transistor Q2 is as follows:

in, Indicates the gain of the junction gate field effect transistor Q2, /> Represents the transconductance of the junction gate field effect transistor Q2.

The beneficial effect of the above further scheme is: in the secondary voltage signal amplifying circuit composed of resistor R5 and junction gate field effect transistor Q2 in the present invention, the primary voltage signal amplifying circuit and the secondary voltage signal amplifying circuit are connected by direct coupling to achieve further amplification of the equivalent voltage signal output by the piezoelectric sensor.

Furthermore, the total gain of the piezoelectric signal conditioning circuit is expressed as follows:

in, Indicates the total amplification factor of the piezoelectric signal conditioning circuit.

The beneficial effect of the above further scheme is: in the present invention, the primary voltage signal amplifying circuit composed of resistor R3, resistor R4 and junction field effect transistor Q1, the secondary voltage signal amplifying circuit composed of resistor R5 and junction gate field effect transistor Q2, the primary voltage signal amplifying circuit and the secondary voltage signal amplifying circuit are connected by direct coupling to realize the amplification function of the equivalent voltage signal output by the piezoelectric sensor.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a circuit diagram of the present invention.

FIG. 2 is a schematic diagram of a signal processing circuit built into a certain IEPE piezoelectric vibration acceleration sensor in this embodiment.

Detailed ways

The specific implementation modes of the present invention are described below so that those skilled in the art can understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific implementation modes. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention as defined and determined by the attached claims, these changes are obvious, and all inventions and creations utilizing the concept of the present invention are protected.

Example 1

As shown in FIG1 , the present invention provides a piezoelectric signal conditioning circuit, comprising:

A high-frequency signal attenuation circuit module is used to obtain the equivalent voltage signal output by the piezoelectric sensor and perform frequency selection filtering on the equivalent voltage signal and its coupled electromagnetic pulse signal;

The impedance conversion and IEPE interface circuit module is used to perform impedance conversion, signal amplification and gain adjustment on the equivalent voltage signal after the frequency selection and filtering processing, and output the processed equivalent voltage signal to the anti-electromagnetic pulse interference circuit module through the IEPE interface;

The anti-electromagnetic pulse interference circuit module is used to filter the received voltage signal.

The high-frequency signal attenuation circuit module includes a resistor R1 and a capacitor C2;

One end of the resistor R1 is connected to the external piezoelectric sensor through the coupling capacitor C1 and serves as the input terminal Vin of the piezoelectric signal conditioning circuit. The other end of the resistor R1 is respectively connected to one end of the capacitor C2 and the impedance transformation and IEPE interface circuit module; the other end of the capacitor C2 is connected to the impedance transformation and IEPE interface circuit module. The resistor R1 and the capacitor C2 form a resistor-capacitor network RC of the high-frequency signal attenuation circuit.

The impedance conversion and IEPE interface circuit module includes a junction field effect transistor Q1, a junction gate field effect transistor Q2, a bootstrap resistor R2, a resistor R3, a resistor R4 and a resistor R5;

One end of the bootstrap resistor R2 is respectively connected to the other end of the resistor R1 and the gate of the junction field effect transistor Q1, the source of the junction field effect transistor Q1 is connected to one end of the resistor R3, the drain of the junction field effect transistor Q1 is respectively connected to one end of the resistor R4 and the gate of the junction gate field effect transistor Q2, the source of the junction gate field effect transistor Q2 is connected to one end of the resistor R5, the drain of the junction gate field effect transistor Q2 is respectively connected to the other end of the resistor R4 and the anti-electromagnetic pulse interference circuit module, and the other end of the bootstrap resistor R2 is respectively connected to the other end of the capacitor C2, the other end of the resistor R3 and the other end of the resistor R5, and is grounded.

The anti-electromagnetic pulse interference circuit module includes a capacitor C3, a resistor R6 and a transient suppression diode D1;

One end of the resistor R6 is respectively connected to the drain of the junction gate field effect transistor Q2 and one end of the capacitor C3, the other end of the resistor R6 is respectively connected to the constant current source power supply terminal lin and the cathode of the transient suppression diode D1, and serves as the output terminal Vout of the piezoelectric conditioning circuit, the anode of the transient suppression diode D1 is respectively connected to the other end of the capacitor C3, the other end of the resistor R5, the other end of the resistor R3, the other end of the bootstrap resistor R2 and the other end of the capacitor C2, and is grounded.

In this embodiment, as shown in FIG1 , under a vibration environment, the output of the piezoelectric sensor is equivalent to a charge generating device. Due to the existence of the internal piezoelectric sensor capacitance and the distributed capacitance of the connecting cable, the output of the piezoelectric sensor can also be equivalent to a voltage generating device, and its output equivalent voltage is / > :/> , where /> represents the internal capacitance of the piezoelectric sensor, /> Represents the distributed capacitance of the connecting cable. The voltage signal has an extremely high output impedance, usually above 109 Ω. The piezoelectric signal conditioning circuit includes three functional circuit modules, namely, the high-frequency signal attenuation circuit module, the impedance transformation and IEPE interface circuit module, and the anti-electromagnetic pulse interference circuit module. The high-frequency signal attenuation circuit module is used to obtain the equivalent voltage signal output by the piezoelectric sensor and filter the signal and its coupled electromagnetic pulse signal; the impedance transformation and IEPE interface circuit module is used to perform impedance transformation, signal amplification and gain adjustment on the equivalent voltage signal output by the piezoelectric sensor, and output the amplified signal through the IEPE interface; the anti-electromagnetic pulse interference circuit module is used to filter the amplified signal to reduce the impact of external electromagnetic pulse interference signals on the circuit.

In this embodiment, the working principle of the piezoelectric signal conditioning circuit is as follows: the piezoelectric signal conditioning circuit is powered by a constant current source, the equivalent voltage output by the piezoelectric sensor is coupled and input through the capacitor C1, and then the first-order low-pass filter composed of the resistor R1 and the capacitor C2 is used for frequency selection filtering, so as to achieve the attenuation of the high-frequency signal of the piezoelectric sensor and increase the frequency response range of the piezoelectric sensor. The filtered voltage signal is then sent to the signal amplification circuit with an IEPE interface composed of four peripheral resistors, namely, the junction field effect transistor Q1 (JFET), the junction gate field effect transistor Q2 (MOS tube) and the resistors R2-R5, to achieve the gain adjustment and impedance conversion functions. At the signal output end, the electromagnetic pulse interference signal suppression circuit at the signal output end is composed of the resistor R6, the capacitor C3 and the transient suppression diode D1, so as to realize the anti-electromagnetic pulse interference function of the IEPE circuit.

In this embodiment, in Figure 1, Qa is the charge output of the piezoelectric sensor; Ra is the internal resistance of the piezoelectric sensor; Ca is the internal capacitance of the piezoelectric sensor; Cc is the distributed capacitance of the connecting cable; Va is the equivalent voltage output of the piezoelectric sensor; C1 is the coupling capacitor of the signal input; R1 and C2 are the RC network of the high-frequency signal attenuation circuit; R2 is the bootstrap resistor of the field effect transistor Q1; Vout is the voltage signal output by the piezoelectric signal conditioning circuit; Vout1 is the voltage signal output by the junction field effect transistor Q1.

In this embodiment, according to the schematic diagram of the piezoelectric signal conditioning circuit in FIG1 , the relationship between the frequency characteristic of the high-frequency signal attenuation circuit and RC is shown in (1), that is:

(1)

in, Indicates the cutoff frequency of the high-frequency signal attenuation circuit module at -3dB attenuation.

It can be seen from formula (1) that by adjusting the time constant of R 1 C 2, the high-frequency signal can be attenuated and the frequency response capability of the piezoelectric sensor can be expanded.

In this embodiment, according to the schematic diagram of the piezoelectric signal conditioning circuit in FIG1, combined with the small signal model of the junction field effect transistor amplifier circuit, the transconductance of the field effect transistor Q1 and the input voltage can be expressed according to the relationship (2), that is:

(2)

in, Represents the equivalent voltage output by the piezoelectric sensor, /> represents the transconductance of the field effect transistor Q1, /> Represents the static operating point voltage of field effect transistor Q1.

The relationship between the transconductance of the field effect transistor Q1 and the output voltage is shown in (3), that is:

(3)

in, Represents the voltage signal output by the junction field effect transistor Q1.

The amplification factor of the field effect tube Q1 The calculation is shown in formula (4), namely:

(4)

Substituting equations (2) and (3) into equation (4), we can simplify equation (5), which is:

(5)

Similarly, the amplification factor of the field effect tube Q2 can be calculated , see formula (6), that is:

in, Indicates the gain of the junction gate field effect transistor Q2, /> Represents the transconductance of the junction gate field effect transistor Q2.

Therefore, the total amplification factor of the piezoelectric signal conditioning circuit is See formula (7), that is:

(7)

in, Indicates the total amplification factor of the piezoelectric signal conditioning circuit.

In this embodiment, the piezoelectric signal conditioning circuit input is a sensor based on the piezoelectric principle, or the input signal is an input device represented by an electric charge, and is used for signal conditioning of this type of sensor.

In this embodiment, the method for attenuating high-frequency signals in a piezoelectric signal conditioning circuit is as follows: attenuating the amplitude of the high-frequency signal by a high-frequency signal attenuation circuit module.

In this embodiment, the piezoelectric signal conditioning circuit is composed of a signal amplifying circuit composed of field effect transistors. Resistors R2-R5, junction field effect transistor Q1 and junction gate field effect transistor Q2 form a signal amplifying circuit and an IEPE interface conversion circuit.

In this embodiment, in the piezoelectric signal conditioning circuit, the resistors R1 and R3 to R5 have a value range of 10 kΩ to 100 kΩ, the resistor R2 has a value range of 10 MΩ to 10 GΩ, and the electrical capacitor C2 has a value range of 10 pF to 1000 pF.

In this embodiment, the present invention has two major breakthroughs: First, it solves the problem that the existing circuit cannot correct and adjust the frequency response of the piezoelectric sensor. In the present invention, a high-frequency signal attenuation circuit module is built into the piezoelectric signal conditioning circuit. By adjusting the time constant of the high-frequency signal attenuation circuit RC, the high-frequency response amplitude of the piezoelectric sensor is attenuated, which can greatly increase the operating frequency range of the sensor and reduce the design difficulty of the piezoelectric sensor. Second, the existing circuit structure is complex and the reliability is not high. In the present invention, the core component of the piezoelectric signal conditioning circuit is a signal amplification circuit composed of two field effect transistors, the junction field effect transistor Q1/junction gate field effect transistor Q2, which realizes the impedance transformation, gain adjustment, IEPE output and other functions of the piezoelectric sensor output signal. The circuit structure is simple and the reliability is high.

In this embodiment, as shown in Figure 2, in Figure 2, coupling capacitor C1: 200nF, capacitor C2: 200pF, capacitor C3: 1nF, resistor R1: 47kΩ, bootstrap resistor R2: 1GΩ, resistor R3: 5.1kΩ, resistor R4: 47kΩ, resistor R5: 240Ω, resistor R6: 10Ω, junction field effect transistor Q1: CS4392, junction gate field effect transistor Q2: ZVN3310F, transient suppression diode D1: SY5643. In this scheme, the frequency response range of the piezoelectric sensor is required to be 5Hz~12.8kHz, because the frequency response range of the piezoelectric sensor is 5Hz~10kHz. If the frequency range exceeds 10kHz, the output sensitivity of the piezoelectric sensor will increase and exceed the sensor index requirement. According to the requirements of the present invention, the high-frequency signal attenuation -3dB turning frequency point is 16.93kHz. After the piezoelectric sensor output signal is attenuated at 10kHz, the frequency response of the piezoelectric sensor meets the 5Hz~12.8kHz index requirement. The original charge sensitivity Sa of the piezoelectric sensor is 4pC/g (pk-pk), and the capacitance Ca of the piezoelectric sensor is about 300pF. According to the requirements of the present invention, when the field effect tube is selected, the output sensitivity Sv (pk-pk) of the piezoelectric sensor after signal conditioning can be calculated according to formula (7) and will be equal to: mV/g, which can basically be applied to the testing needs of vibration intensity in industry.

Those skilled in the art will appreciate that the embodiments described herein are intended to help readers understand the principles of the present invention, and should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those skilled in the art can make various other specific variations and combinations that do not deviate from the essence of the present invention based on the technical revelations disclosed by the present invention, and these variations and combinations are still within the protection scope of the present invention.

Claims (5)

1. A piezoelectric signal conditioning circuit, comprising: A high-frequency signal attenuation circuit module is used to obtain the equivalent voltage signal output by the piezoelectric sensor and perform frequency selection filtering on the equivalent voltage signal and its coupled electromagnetic pulse signal; The impedance conversion and IEPE interface circuit module is used to perform impedance conversion, signal amplification and gain adjustment on the equivalent voltage signal after the frequency selection and filtering processing, and output the processed equivalent voltage signal to the anti-electromagnetic pulse interference circuit module through the IEPE interface; An anti-electromagnetic pulse interference circuit module is used to filter the received voltage signal; The high-frequency signal attenuation circuit module includes a resistor R1 and a capacitor C2; One end of the resistor R1 is connected to the external piezoelectric sensor through the coupling capacitor C1 and serves as the input terminal Vin of the piezoelectric signal conditioning circuit. The other end of the resistor R1 is respectively connected to one end of the capacitor C2 and the impedance conversion and IEPE interface circuit module; the other end of the capacitor C2 is connected to the impedance conversion and IEPE interface circuit module. The resistor R1 and the capacitor C2 form a resistor-capacitor network RC of the high-frequency signal attenuation circuit. The impedance conversion and IEPE interface circuit module includes a junction field effect transistor Q1, a junction gate field effect transistor Q2, a bootstrap resistor R2, a resistor R3, a resistor R4 and a resistor R5; One end of the bootstrap resistor R2 is respectively connected to the other end of the resistor R1 and the gate of the junction field effect transistor Q1, the source of the junction field effect transistor Q1 is connected to one end of the resistor R3, the drain of the junction field effect transistor Q1 is respectively connected to one end of the resistor R4 and the gate of the junction gate field effect transistor Q2, the source of the junction gate field effect transistor Q2 is connected to one end of the resistor R5, the drain of the junction gate field effect transistor Q2 is respectively connected to the other end of the resistor R4 and the anti-electromagnetic pulse interference circuit module, and the other end of the bootstrap resistor R2 is respectively connected to the other end of the capacitor C2, the other end of the resistor R3 and the other end of the resistor R5, and is grounded; The anti-electromagnetic pulse interference circuit module includes a capacitor C3, a resistor R6 and a transient suppression diode D1; One end of the resistor R6 is respectively connected to the drain of the junction gate field effect transistor Q2 and one end of the capacitor C3, the other end of the resistor R6 is respectively connected to the constant current source power supply terminal lin and the cathode of the transient suppression diode D1, and serves as the output terminal Vout of the piezoelectric conditioning circuit, the anode of the transient suppression diode D1 is respectively connected to the other end of the capacitor C3, the other end of the resistor R5, the other end of the resistor R3, the other end of the bootstrap resistor R2 and the other end of the capacitor C2, and is grounded. 2. The piezoelectric signal conditioning circuit according to claim 1, characterized in that the relationship between the RC network of the high-frequency signal attenuation circuit module and the frequency characteristics of the high-frequency signal attenuation circuit is as follows: in, Indicates the cutoff frequency of the high-frequency signal attenuation circuit module at -3dB attenuation. 3. The piezoelectric signal conditioning circuit according to claim 2, characterized in that the expression of the gain of the junction field effect transistor Q1 is as follows: in, Indicates the gain of the junction field effect transistor Q1, /> Represents the transconductance of the junction field effect transistor Q1. 4. The piezoelectric signal conditioning circuit according to claim 3, characterized in that the expression of the gain of the junction gate field effect transistor Q2 is as follows: in, Indicates the gain of the junction gate field effect transistor Q2, /> Represents the transconductance of the junction gate field effect transistor Q2. 5. The piezoelectric signal conditioning circuit according to claim 4, characterized in that the total amplification factor of the piezoelectric signal conditioning circuit is expressed as follows: in, Indicates the total amplification factor of the piezoelectric signal conditioning circuit.