An ICP sensor circuit with high efficiency, wide frequency response and high dynamic range

Abstract

The present invention discloses an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range. The circuit includes a piezoelectric signal input terminal, a piezoelectric signal output terminal and a signal amplification circuit. The piezoelectric signal input terminal is connected to the signal amplification circuit input terminal after passing through a low-frequency compensation circuit and a high-frequency compensation circuit in sequence. The signal amplification circuit output terminal is connected to the piezoelectric signal output terminal and is connected to the piezoelectric signal input terminal through a high dynamic loop. The circuit also includes a power distribution circuit for supplying power to each circuit. The present invention can achieve the effects of wider acceleration measurement range, wider frequency response and higher acceleration measurement accuracy, being applicable to different materials or different structures of piezoelectrics to produce different frequency responses, low production cost and significant economic efficiency.

Description

Technical Field

[0001] The invention relates to the technical field of ICP sensor circuits, and in particular to an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range. Background Art

[0002] ICP (integrated circuits piezoelectric) sensor refers to a built-in piezoelectric sensor. It uses modern integrated circuit technology to place the traditional charge amplifier in the sensor. All high-impedance circuits are sealed in the sensor and output in the form of low-impedance voltage. The output voltage amplitude is proportional to the acceleration. It is a new type of acceleration sensor. The output signal of the ICP sensor cannot be directly acquired by the AD acquisition circuit. It must be powered by a constant current source circuit and its signal must be conditioned into a standard signal (such as ±5v).

[0003] The ICP sensor is composed of a piezoelectric accelerometer and a miniature IC amplifier. It integrates the traditional piezoelectric accelerometer and the charge amplifier. The output of the sensor has a two-wire connection feature; that is, the signal output of the sensor and the constant current power input required by the built-in IC amplifier are on the same wire, and the other wire is the ground wire. It can be directly connected to the recording, display and acquisition equipment, which simplifies the test system and improves the test accuracy and reliability.

[0004] Acceleration sensors that measure vibrations generally use a common material, namely piezoelectric ceramics, as a piezoelectric effect. They generate electric charges under the action of force, and after circuit processing, they output a voltage signal that is proportional to the vibration acceleration. The magnitude of the output voltage reflects the strength of the vibration acceleration. In a certain frequency band, the charge signal generated by piezoelectric ceramics has a good frequency response relationship with the vibration acceleration. Under a certain acceleration, the change in frequency has little effect on the acceleration. However, actual applications often require a wide frequency response range for the sensor, and the actual charge signal generated by piezoelectric ceramics cannot correctly reflect the actual acceleration value in the low and high frequency bands. Figure 1 The actual frequency response curve of the piezoelectric ceramic signal is shown, and it can be seen that the low-frequency and high-frequency bands of the curve are obviously upturned.

[0005] The low frequency band is the adjustment of the lower frequency limit in circuit design. Figure 2 The figure shows the frequency response curve of the uncompensated low-frequency piezoelectric signal, which is generally between 0.1Hz and less than 3Hz. In this frequency response range, the curve is not linear, and the rate of change in a certain section varies with different frequency bands. The circuit of the existing product has only one rate of change compensation adjustment, which has poor tracking performance and low measurement accuracy. The lower cutoff frequency of the signal amplifier circuit can be known from the following formula (1);

[0006]

[0007] When the capacitance in the circuit remains unchanged, the change of the input resistance in the circuit can change the lower cutoff frequency. The input resistance of the amplifier is calculated by adding the input resistance of the amplifier chip in parallel with the bias resistance of the amplifier. Since the input resistance of the amplifier chip is very high, its input resistance is basically determined by the bias resistance. By adjusting the resistance value of the amplifier chip resistor, the slope of the lower frequency change can be adjusted. This can meet the partial compensation of the low frequency band. When the slope of the piezoelectric frequency response curve changes in the lower frequency band, adjusting the slope of a curve obviously has a poor tracking compensation effect.

[0008] The high frequency response of piezoelectric ceramics is due to factors such as different materials and manufacturing processes. Its frequency response curve is not fixed at a certain frequency and changes at 20dB / dec or 40dB / oct after 3dB. Figure 3 The figure shows the frequency response curve of the uncompensated piezoelectric high-frequency signal; the figure shows a slope change from above 1KHz to about 8KHz, and another slope change above 8KHz. The active filters commonly used in existing circuits can use first-order active filters and second-order active filters, or higher-order active filters. No matter which filter concept is used to track the frequency response of piezoelectric ceramics, it is difficult to achieve good compensation. The first-order active filter can meet the requirements above 8KHz, but not below 8KHz, while the second-order active filter can meet the requirements of the frequency band with a high rate of change, but not the frequency band with a low rate of change. The typical structure of the second-order active filter is as follows. Figure 4 The typical structure diagram of the second-order active filter is shown in Figure 1. Among them, Y1~Y5 are admittances. Considering UP=UN, it can be obtained according to KCL;

[0009]

[0010] Formula (2) is the general expression of the transfer function of the second-order voltage-controlled voltage source filter, where Auf = 1 + Rf / R6. As long as Yi is properly selected, 1 ≤ i ≤ 5, low-pass, high-pass, band-pass and other active filters can be constructed. Let Y1 = 1 / R1, Y2 = sC1, Y3 = O, Y4 = 1 / R2, Y5 = sC2, and substitute them into formula (2), the transfer function of the voltage-controlled voltage source type second-order active low-pass filter is obtained as follows:

[0011]

[0012] in,

[0013]

[0014] Equation (3) is a typical expression of the transfer function of a second-order low-pass filter. Where ωn is the characteristic angular frequency and Q is called the equivalent quality factor.

[0015] For domestic sensors of the same type, the effective value of its output voltage signal is around 3.5V, and the peak value is around 5V. The size of the measured acceleration value is determined by the sensitivity of the sensor. If the sensitivity of the sensor is 100mv / g, the measured acceleration is 50g; if the sensitivity of the sensor is 50mv / g, the measured acceleration is 100g; if the sensitivity of the sensor is 100mv / g, the measured acceleration is 90g, its sensor cannot reach this value. Of course, some sensors can reach this value, but the frequency response characteristics of such sensors are far inferior to those of products that reach 50g. This is determined by the circuit design.

[0016] The typical existing sensor circuit is powered by a 24V and 4mA constant current source. The DC bias voltage in the circuit is about 12V, so that the dynamic peak value of the AC signal can reach close to 20V without distortion. Since the sensor improves its frequency response and gain control, an operational amplifier is needed in the circuit to process the gain and frequency response of the pre-signal, such as Figure 5 The figure shows the circuit diagram of the existing sensor pre-bias. Vc is the bias voltage in the circuit. Since it is a single power supply, the chip TLC2262 is a dual operational amplifier, which consists of Ua and Ub. The resistor R2 and the voltage regulator D constitute half of the power supply voltage Vc / 2 provided to the chips Ua and Ub to meet the normal operation of the positive and negative half cycles of the AC signal. In this way, the peak-to-peak value of the circuit AC signal is limited to not exceed 12V. Generally, the peak-to-peak value of the normal signal is 10V, the peak value is 5V, the circuit output voltage peak is 5V, the sensor sensitivity is 100mv / g, and the peak value of the acceleration is 50g. Obviously, the efficiency of this circuit is not high, and the dynamic range of the voltage signal is reduced.

[0017] The existing domestic ICP sensor circuit uses piezoelectricity to generate charge signals and outputs voltage signals through a built-in amplifier. The compensation of frequency response in circuit design cannot achieve good results. The upper frequency limit of the piezoelectric signal is not suppressed, and the frequency response effect is poor. The corresponding ICP sensor circuit mainly includes a preamplifier circuit and a signal amplifier circuit. Its principle is to output a voltage signal after the input pressure point signal passes through the preamplifier circuit and the signal amplifier circuit in sequence. The voltage signal output line is also the constant current input end of the ICP sensor circuit. Its functional block diagram is as follows: Figure 6 As shown. There is another circuit design that compensates the piezoelectric signal, which improves the frequency response effect to a certain extent, but under the same power supply voltage and current supply, the dynamic range of the output signal is suppressed, and the range of the sensor is limited. In addition, although the frequency response is compensated, the frequency response compensation for the piezoelectric signal is still lacking in adaptability and followability, which also restricts the frequency response.

[0018] In the field of practical application, different frequency response sensors should be selected for different application occasions. Civil engineering is generally low-frequency vibration, and the frequency response range of the acceleration sensor is 0.2Hz~1kHz. Machinery and equipment are generally in the medium frequency band. The vibration frequency can be comprehensively estimated based on factors such as equipment speed and equipment stiffness. The frequency range of the acceleration sensor is 0.5Hz~5Hz. For example, when the generator speed is 3000rms, divided by 60s, its main frequency is 50Hz. Collision and impact measurements are mostly high-frequency. At the same time, attention should also be paid to the range of vibration acceleration. Generally, the dynamic peak value of the same type is ±50g, and the dynamic range of vibration acceleration is limited. When an abnormal situation occurs in the measured mechanical equipment, the amplitude of the vibration acceleration will increase beyond the dynamic range of the sensor, so that the output signal of the sensor is distorted and cannot be measured correctly. Under abnormal conditions, the vibration condition of the equipment or higher acceleration measurement may require the configuration of a larger sensor, which increases the complexity of equipment testing. Summary of the invention

[0019] In view of the above-mentioned deficiencies in the current ICP sensor circuit, the present invention provides an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range, which can achieve the effects of wider acceleration measurement range, wider frequency response and higher acceleration measurement accuracy, applicable to piezoelectrics of different materials or different structures to produce different frequency responses, low production cost and significant economic efficiency.

[0020] In order to achieve the above object, the present invention adopts the following technical scheme:

[0021] An ICP sensor circuit with high efficiency, wide frequency response and high dynamic range, comprising a piezoelectric signal input terminal, a piezoelectric signal output terminal and a signal amplification circuit, characterized in that: the piezoelectric signal input terminal is connected to the input terminal of the signal amplification circuit after passing through a low-frequency compensation circuit and a high-frequency compensation circuit in sequence, the output terminal of the signal amplification circuit is connected to the piezoelectric signal output terminal and is connected to the piezoelectric signal input terminal through a high dynamic loop, wherein:

[0022] A low-frequency compensation circuit is used to track and compensate the low-frequency signal input from the piezoelectric signal input terminal, and output the compensated low-frequency signal;

[0023] A high-frequency compensation circuit is used to track and compensate the high-frequency signal inputted from the piezoelectric signal input terminal, and output the compensated high-frequency signal;

[0024] The high dynamic loop is used to effectively amplify the dynamic range of the output signal of the signal amplification circuit, and input the effectively amplified signal into the piezoelectric signal input end to balance the piezoelectric input signal of the piezoelectric signal input end.

[0025] According to one aspect of the present invention, the low-frequency compensation circuit adopts two-level segmented compensation, and the low-frequency compensation circuit includes capacitor C1, capacitor C5, resistor R1 and resistor R6; the capacitor C1 and resistor R1 form a loop; the capacitor C5 and resistor R6 form a loop; the capacitor C1 and capacitor C5 are adjusted respectively according to the gain of the circuit.

[0026] According to one aspect of the present invention, the high-frequency compensation circuit adopts segmented tracking, and the high-frequency compensation circuit includes a chip U1, a capacitor C2, a capacitor C3, a resistor R2 and a resistor R3; the capacitor C2, the capacitor C3, the resistor R2 and the resistor R3 form a loop, and the parameters of the resistor R2 and the capacitor C2 adjust the high-frequency front section; the parameters of the capacitor C3 and the resistor R3 adjust the high-frequency back section.

[0027] According to one aspect of the present invention, the high dynamic loop includes a MOS tube Q1, a transistor Q2, a voltage regulator D2, a capacitor C1 and a capacitor C6; the voltage regulator D2 is connected in series to the source S of the MOS tube Q1; the capacitor C6 is connected in parallel to both ends of the voltage regulator D2; the drain D of the MOS tube Q1 is connected to the base B of the transistor Q2; the emitter E of the transistor Q2 is connected to the piezoelectric signal output end; the capacitor C1 is connected in series between the piezoelectric signal input end and the piezoelectric signal output end; the voltage signal gain is effectively amplified by adjusting the capacitance of the capacitor C1 to achieve the dynamic range of the output signal of the front circuit.

[0028] According to one aspect of the present invention, the signal amplifying circuit includes a MOS transistor Q1, a triode Q2, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C5 and a capacitor C6.

[0029] According to one aspect of the present invention, the piezoelectric signal output terminal is also the constant current source input terminal of the high-efficiency, wide-band response, and high-dynamic range ICP sensor circuit. The high-efficiency, wide-band response, and high-dynamic range ICP sensor circuit also includes a power distribution circuit for supplying power to each circuit.

[0030] According to one aspect of the present invention, the power distribution circuit includes a MOS transistor Q1, a triode Q2, a voltage regulator D1, a voltage regulator D2, a resistor R4 and a capacitor C6.

[0031] According to one aspect of the present invention, the ICP sensor circuit with high efficiency, wide frequency response and high dynamic range specifically includes resistors R1-R8, capacitors C1-C6, chip U1, voltage regulator tubes D1-D3, MOS tube Q1 and transistor Q2. The pins of the chip U1 include an operational amplifier output terminal OUT, a negative power input terminal V-, an operational same-direction input terminal IN+, an operational reverse input terminal IN- and a positive power input terminal V+. The piezoelectric signal input terminal is divided into three paths, which are respectively connected to one end of the capacitor C1, one end of the resistor R2 and the resistor R1. The other end of the capacitor C1 is connected to the piezoelectric signal output end, the other end of the resistor R2 is divided into two paths and connected to one end of the capacitor C3 and one end of the resistor R3 respectively, the other end of the resistor R1 is divided into two paths and connected to the positive electrode of the voltage regulator tube D1 and one end of the resistor R4 respectively, the other end of the capacitor C3 is divided into three paths and connected to the operational amplifier output end OUT, the operational reverse input end IN- and one end of the capacitor C4 of the chip U1 respectively, the other end of the resistor R3 is divided into two paths and connected to one end of the capacitor C2 and the operational same-direction input end of the chip U1 respectively IN+, the negative electrode of the voltage regulator D1 is divided into three paths and respectively connected to the other end of the capacitor C2, the negative power input terminal V- and the ground GND, the other end of the resistor R4 is divided into four paths and respectively connected to the positive power input terminal V+ of the chip U1, one end of the capacitor C6, the negative electrode of the voltage regulator D2 and the source S of the MOS tube Q1, the other end of the capacitor C4 is divided into three paths and respectively connected to one end of the resistor R6, one end of the capacitor C5 and the gate G of the MOS tube Q1, the other end of the resistor R6 is divided into two paths and respectively connected to one end of the resistor R5 and one end of the resistor R7 The positive electrode of the voltage regulator D2 is grounded to GND, the drain D of the MOS tube Q1 is divided into two paths and respectively connected to one end of the resistor R8 and the base B of the transistor Q2, the collector C of the transistor Q2 is grounded, the positive electrode of the voltage regulator D3 is grounded to GND, the negative electrode of the voltage regulator D3 is connected to the piezoelectric signal output end, the emitter E of the transistor Q2 is connected to the piezoelectric signal output end, and the other ends of the resistor R8, the resistor R5 and the capacitor C5 are all connected to the piezoelectric signal output end.

[0032] According to one aspect of the present invention, the resistance of the resistor R2 is ten times greater than the resistance of the resistor R3, and the capacity of the capacitor C2 is twice greater than that of the capacitor C3.

[0033] According to one aspect of the present invention, the MOS transistor Q1 is an N-channel MOS transistor.

[0034] The present invention has the following advantages over the prior art:

[0035] 1) The present invention can increase the acceleration measurement range by more than 1.8 times compared with similar products, and the product has a wider range of application occasions.

[0036] 2) The frequency response of the present invention is superior to similar products, with a wider frequency response, especially in very low frequency bands and high frequency bands, and a good response is obtained, and the acceleration test accuracy is greatly improved.

[0037] 3) The present invention can adapt to different frequency responses of piezoelectrics made of different materials or structures, and the frequency response tracking compensation parameters can be easily adjusted. For products with different technical indicators, the functions and performance qualities of the products can be consistent, thus ensuring product quality.

[0038] 4) The present invention adopts a tracking compensation method, which effectively improves the qualified rate of product functions and performances, reduces production costs, and has significant economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0040] Figure 1 It is the frequency response curve of the actual piezoelectric ceramic signal;

[0041] Figure 2 This is the frequency response curve of the uncompensated piezoelectric low-frequency signal;

[0042] Figure 3 This is the frequency response curve of the uncompensated piezoelectric high-frequency signal;

[0043] Figure 4 It is a typical structural diagram of a second-order active filter;

[0044] Figure 5 This is a circuit diagram of the existing sensor pre-bias;

[0045] Figure 6 It is a principle block diagram of an existing ICP sensor circuit;

[0046] Figure 7 It is a principle block diagram of an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to the present invention;

[0047] Figure 8 A connection diagram of the instrumentation used to perform verification testing on the circuit of the present invention;

[0048] Fig. 9 This is the frequency response curve obtained after the high frequency band of the piezoelectric signal passes through this circuit;

[0049] Fig.10 The peak value diagram of the undistorted signal designed for the circuit test of the present invention;

[0050] Fig.11 The present invention is a circuit diagram of an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range. DETAILED DESCRIPTION

[0051] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0052] like Figure 7 The schematic diagram of the ICP sensor circuit with high efficiency, wide frequency response and high dynamic range of the present invention is shown. The piezoelectric signal input terminal is connected to the input terminal of the signal amplifier circuit after passing through the low-frequency compensation circuit and the high-frequency compensation circuit in sequence. The output terminal of the signal amplifier circuit is connected to the piezoelectric signal output terminal and is connected to the piezoelectric signal input terminal through the high dynamic loop. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range also includes a power distribution circuit for supplying power to each circuit, wherein the low-frequency compensation circuit is used to track and compensate the low-frequency signal input to the piezoelectric signal input terminal and output the compensated low-frequency signal; the high-frequency compensation circuit is used to track and compensate the high-frequency signal input to the piezoelectric signal input terminal and output the compensated high-frequency signal; the high-dynamic loop is used to effectively amplify the dynamic range of the output signal of the signal amplifier circuit, and input the effectively amplified signal to the piezoelectric signal input terminal to balance the piezoelectric input signal of the piezoelectric signal input terminal. "Balance" specifically means that when the piezoelectric signal at the piezoelectric signal input terminal is enhanced, the signal of the high dynamic loop is increased at the same time, offsetting the enhanced input signal to ensure that the output signal waveform is not distorted.

[0053] like Fig.11The circuit diagram of an ICP sensor circuit with high efficiency, wide frequency response and high dynamic range of the present invention is shown. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range specifically includes resistors R1 to R8, capacitors C1 to C6, chip U1, voltage regulator tubes D1 to D3, MOS tube Q1 and transistor Q2. The pins of the chip U1 include an operational amplifier output terminal OUT, a negative power input terminal V-, an operational same-direction input terminal IN+, an operational reverse input terminal IN- and a positive power input terminal V+. The piezoelectric signal input terminal is divided into three paths and connected to one end of the capacitor C1, one end of the resistor R2 and one end of the resistor R1 respectively. The capacitor The other end of C1 is connected to the piezoelectric signal output end, the other end of the resistor R2 is divided into two paths, connected to one end of the capacitor C3 and one end of the resistor R3 respectively, the other end of the resistor R1 is divided into two paths, connected to the positive electrode of the voltage regulator tube D1 and one end of the resistor R4 respectively, the other end of the capacitor C3 is divided into three paths, connected to the operational amplifier output end OUT, the operational reverse input end IN- and one end of the capacitor C4 of the chip U1 respectively, the other end of the resistor R3 is divided into two paths, connected to one end of the capacitor C2 and the operational same-direction input end IN+ of the chip U1 respectively, The negative electrode of the voltage regulator tube D1 is divided into three paths and respectively connected to the other end of the capacitor C2, the negative power input terminal V- and the ground GND. The other end of the resistor R4 is divided into four paths and respectively connected to the positive power input terminal V+ of the chip U1, one end of the capacitor C6, the negative electrode of the voltage regulator tube D2 and the source S of the MOS tube Q1. The other end of the capacitor C4 is divided into three paths and respectively connected to one end of the resistor R6, one end of the capacitor C5 and the gate G of the MOS tube Q1. The other end of the resistor R6 is divided into two paths and respectively connected to one end of the resistor R5 and one end of the resistor R7. The other ends of the resistor R7 and the capacitor C6 are both grounded GND, the positive electrode of the voltage regulator D2 is grounded GND, the drain D of the MOS tube Q1 is divided into two paths and respectively connected to one end of the resistor R8 and the base B of the transistor Q2, the collector C of the transistor Q2 is grounded, the positive electrode of the voltage regulator D3 is grounded GND, the negative electrode of the voltage regulator D3 is connected to the piezoelectric signal output end, the emitter E of the transistor Q2 is connected to the piezoelectric signal output end, and the other ends of the resistor R8, the resistor R5 and the capacitor C5 are all connected to the piezoelectric signal output end.

[0054] The low-frequency compensation circuit adopts two-stage segmented compensation, and the low-frequency compensation circuit includes capacitor C1, capacitor C5, resistor R1 and resistor R6; the high-frequency compensation circuit adopts segmented tracking, and the high-frequency compensation circuit includes chip U1, capacitor C2, capacitor C3, resistor R2 and resistor R3; the high dynamic loop includes MOS tube Q1, transistor Q2, voltage regulator tube D2, capacitor C1 and capacitor C6; the signal amplification circuit includes MOS tube Q1, transistor Q2, resistor R5, resistor R6, resistor Resistor R7, resistor R8, capacitor C5 and capacitor C6; the power distribution circuit includes MOS tube Q1, triode Q2, voltage regulator D1, voltage regulator D2, resistor R4 and capacitor C6; the resistance of the resistor R2 is greater than ten times the resistance of the resistor R3, and the capacity of the capacitor C2 is greater than twice the capacity of the capacitor C3; the MOS tube Q1 is an N-channel MOS tube; when the model of the chip U1 is OPA342NA and the model of the MOS tube Q1 is 2N7002, the technical effect of the present invention can be achieved. It should be noted that the above-mentioned models should not be used as limiting conditions of the present invention. Models with the same or similar performance as the above-mentioned models or with the development of technology, any similar devices that exceed the performance of the above-mentioned models and can achieve the technical effect of the present invention belong to the protection scope of the present invention.

[0055] (I) Wide-band response circuit

[0056] In order for the sensor to achieve a good wide-band response, the circuit must track and compensate the frequency response of the piezoelectric signal. According to the frequency response curve of the piezoelectric signal, it is divided into lower limit frequency and upper limit frequency compensation.

[0057] 1. Lower frequency limit tracking compensation

[0058] The low-frequency compensation circuit adopts two-stage segmented compensation, and the low-frequency compensation circuit is used for lower-limit frequency tracking compensation. The low-frequency compensation circuit includes capacitor C1, capacitor C5, resistor R1 and resistor R6. Capacitor C1 and resistor R1 form a loop, and by adjusting the resistance value of resistor R1, the compensation of the part with a lower rate of change of the piezoelectric frequency response curve is tracked; capacitor C5 and resistor R6 form a loop, and by adjusting the resistance value of resistor R6, the compensation of the part with a higher rate of change of the piezoelectric frequency response curve is tracked. Fig.11In the circuit shown, MOS tube Q1 and transistor Q2 are combined into a composite tube. MOS tube Q1 has the high input impedance characteristics of MOSFET, and transistor Q2 meets the output impedance. The capacitor C5 and resistor R6 in the circuit form a parameter element for adjusting a slope. The capacitor C5 is related to the circuit gain in the design. Under the condition of meeting the circuit gain, the capacity of capacitor C5 is basically determined, and the slope of the compensation curve is adjusted by resistor R6. Another parameter element of the slope is composed of chip U1, bias resistor R1 and feedback capacitor C1. Similarly, the capacity of capacitor C1 is related to the gain of the circuit design. When the circuit gain is met, the capacity of capacitor C1 is determined. Chip U1 is designed as a follower circuit, and the input impedance is also very high. The adjustment of resistor R1 can change the slope of the curve. According to the slope of the lower part of the piezoelectric frequency response curve, the inflection point frequency and output voltage value of the known curve are measured.

[0059] According to the lower rate of change of the piezoelectric frequency response curve, measure the inflection point frequency and output voltage value of the known curve. The test schematic diagram is as follows: Figure 8 As shown, use the signal generator to set the frequency to the inflection point frequency, set the output voltage to 1V, use an oscilloscope to observe the input and output waveforms, and use a digital voltmeter to measure the circuit output voltage. The gain of this circuit is 4. Adjust the resistance value of resistor R1 so that the output voltage is 4V and the error is 5%. Then gradually increase the frequency of the signal generator to 10Hz, and the output of the signal generator remains unchanged. During the frequency change process, the circuit output voltage is around 4V and the error is within 5%. The adjustment is completed to make this section of frequency response tracking good.

[0060] According to the part with higher rate of change of piezoelectric frequency response curve, the inflection point frequency and output voltage value of the known curve are also measured. The measurement diagram is as follows: Figure 8 As shown, the frequency of the signal generator is set to the inflection point frequency, the output voltage is also set to 1V, the input and output waveforms are observed with an oscilloscope, and the digital voltmeter also measures the circuit output voltage. The circuit gain is still 4, and the resistance value of resistor R6 is adjusted to make the output voltage 4V with an error of 5%. Then the frequency of the signal generator is gradually increased to 2Hz, and the output of the signal generator remains unchanged. During the frequency change process, the circuit output voltage is around 4V and the error is within 5%. The adjustment is completed so that the part with a higher rate of change of the frequency response curve can be tracked well.

[0061] 2. Upper limit frequency tracking compensation

[0062] The high-frequency compensation circuit adopts segmented tracking, and the high-frequency compensation circuit includes chip U1, capacitor C2, capacitor C3, resistor R2 and resistor R3; the upper high-frequency band of the piezoelectric frequency response signal adopts segmented tracking, and a loop is formed by C2, C3, R2, and R3. The parameters of R2 and C2 are adjusted to correspond to the high-frequency front section to track the compensation of the lower slope part of the piezoelectric frequency response curve. The parameters of C3 and R3 are adjusted to correspond to the high-frequency rear section to track the compensation of the higher slope part of the piezoelectric frequency response curve.

[0063] After improving the circuit based on the existing technology, the present invention sets Y1=1 / R2, Y2=sC3, Y3=0, Y4=1 / R3, Y5=sC2, Rf / R6=0, Auf=1, and substitutes it into formula (2) to obtain the transfer function formula (4) of the voltage-controlled voltage source type active low-pass filter.

[0064]

[0065] in,

[0066]

[0067] Utilizing the characteristics of the second-order low-pass filter, different Q values ​​produce different rates of change. By adjusting the resistor R2, resistor R3 and capacitor C3 in the circuit, different Q values ​​are obtained to correspond to the piezoelectric frequency response change rate, and the best cut-off frequency is selected according to the piezoelectric frequency response curve. When the piezoelectric frequency response curve rises to 10%, the corresponding frequency is used as the cut-off frequency of the circuit. This circuit is designed with resistor R2 and capacitor C2 as the dominant circuit cut-off frequency. When the piezoelectric frequency response curve rises to more than 10%, due to the variability of the rate of change, the resistor R3 and capacitor C3 of this circuit are used to adjust the tracking rate of change. Although adjusting resistors R2, R3, C2 and C3 will affect the cut-off frequency and Q value, when the circuit parameters are properly designed so that the value of resistor R2 is more than ten times the value of resistor R3 and the capacity of capacitor C2 is more than twice the capacity of capacitor C3, the influence of adjusting each parameter separately is small, and the effect of tracking the piezoelectric high-frequency frequency response curve is very good. Fig. 9 The figure shows the frequency response curve obtained after the high frequency band of the piezoelectric signal passes through this circuit.

[0068] from Fig. 9 It can be seen that the frequency deviation from 1KHz to 20KHz is basically controlled within 5%, which is also one of the requirements to be achieved by the circuit design of the present invention, and effectively improves the frequency response range of the sensor and the precision and accuracy of vibration acceleration measurement.

[0069] According to the slope of the lower part of the piezoelectric frequency response curve, measure the inflection point frequency and output voltage value of the known curve. The measurement diagram is as follows Figure 8As shown, use the signal generator to set the frequency to the inflection point frequency, set the output voltage to 1V, use an oscilloscope to observe the input and output waveforms, use a digital voltmeter to measure the circuit output voltage, adjust the resistance value of resistor R2 and the capacitance of capacitor C2 to make the output voltage 4V with an error of 5%, and then gradually adjust the frequency of the signal generator from high frequency to low, and the output of the signal generator remains unchanged. During the frequency change process, the circuit output voltage is around 4V with an error of 5%, indicating that this section of frequency response tracking is good.

[0070] According to the slope of the higher part of the piezoelectric frequency response curve, the frequency difference in this section is not large. According to the characteristics of the second-order active filter, it is achieved by changing the Q value. Similarly, the inflection point frequency and output voltage value of the known curve are measured. The measurement diagram is shown in the figure. Figure 8 As shown, the signal generator frequency is set to the inflection point frequency, the output voltage is also set to 1V, the oscilloscope observes the input and output waveforms, and the digital voltmeter also measures the circuit output voltage. The circuit gain is still 4, and the resistance value of resistor R3 and the capacitance value of capacitor C3 are adjusted to make the output voltage 4V with an error of 5%. Then the frequency of the signal generator is gradually adjusted down from the inflection point frequency, and the output of the signal generator remains unchanged. During the frequency change process, the circuit output voltage is around 4V with an error within 5%. The adjustment is completed so that the higher part of the frequency response curve tracks well.

[0071] 2. High dynamic range

[0072] The output signal has a high dynamic range without signal distortion and wide frequency response. The bias design of the circuit is the key, and the chip power supply point in the circuit is particularly important.

[0073] 1. Circuit bias design

[0074] In order to ensure that the power supply of the front-end circuit chip is not affected by the circuit bias voltage, the power supply is completed by the back-end circuit, such as Fig.11 As shown, MOS tube Q1, voltage regulator D2 and capacitor C6 form the chip power supply. The voltage regulator D2 is connected in series to the source S of the MOS tube Q1. The voltage regulator D2 is selected to have a voltage regulator voltage of 2.7V to meet the output high dynamic range, and the AC signal loop is not affected. The front chip U1 is supplied with a single power supply, and its DC bias midpoint voltage is designed to be 0.7V, which is composed of the resistor R4 and the voltage regulator D1 in the circuit. To debug the bias circuit, connect a 24V / 4mA constant current source, and use a multimeter to measure the DC voltage at the output end. The design voltage is 13V. Adjust the resistance values ​​of the resistors R5 and R7 in the circuit to make the DC bias voltage 13V. The voltage at the end of the voltage regulator D2 is measured to be 2.7V, the voltage at the end of the voltage regulator D1 is 0.7V, and the voltage at both ends of the resistor R8 is 0.3V, which meets the DC bias of the entire circuit.

[0075] In the sensor front-end circuit design of the present invention, the chip power supply is not supplied by the bias voltage in the circuit, but by the voltage of the voltage regulator D2, and the voltage regulator D1 is used as the circuit half voltage. Fig.11 As shown in the figure, the change of bias voltage in the circuit does not affect the operation of the front-end circuit. The voltage signal gain is adjusted by adjusting the capacitance of the feedback capacitor C1, so that the dynamic range of the signal output by the front-end circuit is effectively amplified, making full use of the 24V power supply voltage. The peak-to-peak value of the undistorted signal in the actual test can reach nearly 20V. Fig.10 The figure shows the peak value of the undistorted signal of the actual test of the circuit designed by the present invention, which shows a peak value of 23.20V, a valley value of 3.62V, and a peak-to-peak value of 23.2-3.62=19.58 (V). When the sensitivity of the piezoelectric sensor is 100mv / g, the peak value of the acceleration is close to 100g, the efficiency of the circuit is greatly improved, the dynamic range of the voltage signal is significantly enlarged, and the acceleration measurement range of the sensor is expanded.

[0076] 2. Negative feedback design

[0077] The power supply voltage of the front-end circuit chip is only 2.7V, the DC bias midpoint voltage is 0.7V, and the peak-to-peak value of the input signal is 1.4V. A negative feedback circuit is introduced at the input end of the front-end circuit. Fig.11 The capacitor C1 in the circuit. The feedback signal is introduced directly from the output end, so that when the input signal increases, the negative feedback signal increases at the same time, offsetting the increase of the input signal, so that the signal will not be distorted. To debug the feedback circuit, use a signal transmitter to set the frequency to 160Hz, and gradually adjust the output voltage from a small peak to a peak value of 1.4V. When the input voltage increases, observe the signal waveform of the oscilloscope at the connection end of the capacitor C4 and chip U1 in the measurement circuit. When it is found that the peak-to-peak value of the input voltage has not reached 1.4V, the waveform has been distorted and clipped. At this time, adjust the capacitance of the feedback capacitor C1, increase the capacitance of C1, strengthen the negative feedback strength, and repeatedly adjust until the circuit design gain point is reached and the output signal is not distorted. After reasonable debugging of the circuit bias setting and feedback circuit, this circuit design meets the high dynamic range.

[0078] The front-end circuit chip U1 of the present invention adopts the model OPA342NA micro-power consumption, low voltage, low noise, precise rail-to-rail output, single-power supply operational amplifier. Fig.11As shown, the power supply is supplied by the voltage regulator D2. D2 is the source of the N-channel MOSFET model 2N7002 in series in the MOS tube Q1. Its voltage loop is 24V→voltage drop across resistor R8→Q1 (voltage between drain D and source S)→voltage of D2 voltage regulator→GND. In order to ensure the dynamic range of the signal, the DC voltage between drain D and source S is designed to be as high as possible. Since the MOS tube Q1 (MOSFET) and the triode Q2 form a composite amplifier, the size of the bias resistor R5 of the MOS tube Q1 is adjusted to reduce the DC current between the drain D and source S of the MOS tube Q1, and the voltage drop of the resistor R8 is reduced to reach the voltage of the voltage regulator D2. The stable voltage of the voltage regulator D2 is selected at 1.8V-3V, which can achieve a high dynamic range. It can be seen that the power supply voltage of the front circuit chip U1 is controlled at 1.8V-3V, so a micro-power low-voltage, low-noise, precise rail-to-rail output, single-power op amp is selected. Whether the selection of these components is reasonable directly affects the dynamic range of the circuit. The power supply voltage of chip U1 is only 1.8V-3V, and the input signal of the front circuit is limited. The input signal of the front circuit is provided by a piezoelectric signal, so a negative feedback circuit is introduced at the input end of the piezoelectric signal. Fig.11 In this way, when the input signal increases, the negative feedback signal increases at the same time, offsetting the increase of the input signal, so that the signal will not be distorted, and the capacitance of capacitor C1 is reasonably adjusted to achieve the balance point of the circuit design gain.

[0079] Among them, piezoelectrics of different materials or structures have different frequency responses. When the frequency of the piezoelectric material is high, the piezoelectric signal directly passes through the low-frequency compensation circuit, and then passes through the high-frequency compensation circuit for high-frequency tracking compensation. When the frequency response of the piezoelectric material is low, the piezoelectric signal passes through the low-frequency compensation circuit for compensation tracking, and then directly passes through the high-frequency compensation.

[0080] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. An ICP sensor circuit with high efficiency, wide frequency response and high dynamic range, comprising a piezoelectric signal input terminal, a piezoelectric signal output terminal and a signal amplification circuit, characterized in that: The piezoelectric signal input end is connected to the input end of the signal amplifying circuit after passing through the low-frequency compensation circuit and the high-frequency compensation circuit in sequence, and the output end of the signal amplifying circuit is connected to the piezoelectric signal output end and connected to the piezoelectric signal input end through a high dynamic loop, wherein: The low-frequency compensation circuit is used to track and compensate the low-frequency signal input from the piezoelectric signal input terminal, and output the compensated low-frequency signal. The low-frequency compensation circuit adopts two-level segmented compensation. The low-frequency compensation circuit includes a capacitor C1, a capacitor C5, a resistor R1 and a resistor R6; the capacitor C1 and the resistor R1 form a loop; the capacitor C5 and the resistor R6 form a loop; the capacitor C1 and the capacitor C5 are adjusted according to the gain of the circuit respectively; The high-frequency compensation circuit is used to track and compensate the high-frequency signal input to the piezoelectric signal input terminal, and output the compensated high-frequency signal. The high-frequency compensation circuit adopts segmented tracking. The high-frequency compensation circuit includes a chip U1, a capacitor C2, a capacitor C3, a resistor R2 and a resistor R3; the capacitor C2, the capacitor C3, the resistor R2 and the resistor R3 form a loop, and the parameters of the resistor R2 and the capacitor C2 adjust the high-frequency front section; the parameters of the capacitor C3 and the resistor R3 adjust the high-frequency back section; The high dynamic loop is used to effectively amplify the dynamic range of the output signal of the signal amplification circuit, and input the effectively amplified signal into the piezoelectric signal input end to balance the piezoelectric input signal of the piezoelectric signal input end. The high dynamic loop includes a MOS tube Q1, a transistor Q2, a voltage regulator D2, a capacitor C1 and a capacitor C6; the voltage regulator D2 is connected in series to the source S of the MOS tube Q1; the capacitor C6 is connected in parallel to the two ends of the voltage regulator D2; the drain D of the MOS tube Q1 is connected to the base B of the transistor Q2; the emitter E of the transistor Q2 is connected to the piezoelectric signal output end; the capacitor C1 is connected in series between the piezoelectric signal input end and the piezoelectric signal output end; the piezoelectric signal gain is achieved by adjusting the capacitance of the capacitor C1 to achieve effective amplification of the dynamic range of the output signal of the pre-circuit.

2. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to claim 1, characterized in that: The signal amplifying circuit includes a MOS tube Q1, a triode Q2, a resistor R5, a resistor R6, a resistor R7, a resistor R8, a capacitor C5 and a capacitor C6.

3. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to claim 1, characterized in that: The piezoelectric signal output end is also the constant current source input end of the high-efficiency, wide-band response, and high-dynamic-range ICP sensor circuit. The high-efficiency, wide-band response, and high-dynamic-range ICP sensor circuit also includes a power distribution circuit for supplying power to each circuit.

4. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to claim 3, characterized in that: The power distribution circuit includes a MOS tube Q1, a triode Q2, a voltage regulator tube D1, a voltage regulator tube D2, a resistor R4 and a capacitor C6.

5. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to any one of claims 1 to 4, characterized in that: The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range specifically includes resistors R1-R8, capacitors C1-C6, chip U1, voltage regulator tubes D1-D3, MOS tube Q1 and transistor Q2. The pins of the chip U1 include an operational amplifier output terminal OUT, a negative power input terminal V-, an operational same-direction input terminal IN+, an operational reverse input terminal IN- and a positive power input terminal V+. The piezoelectric signal input terminal is divided into three paths and connected to one end of the capacitor C1, one end of the resistor R2 and one end of the resistor R1 respectively. The capacitor The other end of C1 is connected to the piezoelectric signal output end, the other end of the resistor R2 is divided into two paths, connected to one end of the capacitor C3 and one end of the resistor R3 respectively, the other end of the resistor R1 is divided into two paths, connected to the positive electrode of the voltage regulator tube D1 and one end of the resistor R4 respectively, the other end of the capacitor C3 is divided into three paths, connected to the operational amplifier output end OUT, the operational reverse input end IN- and one end of the capacitor C4 of the chip U1 respectively, the other end of the resistor R3 is divided into two paths, connected to one end of the capacitor C2 and the operational same-direction input end IN+ of the chip U1 respectively, The negative electrode of the voltage regulator tube D1 is divided into three paths and respectively connected to the other end of the capacitor C2, the negative power input terminal V- and the ground GND. The other end of the resistor R4 is divided into four paths and respectively connected to the positive power input terminal V+ of the chip U1, one end of the capacitor C6, the negative electrode of the voltage regulator tube D2 and the source S of the MOS tube Q1. The other end of the capacitor C4 is divided into three paths and respectively connected to one end of the resistor R6, one end of the capacitor C5 and the gate G of the MOS tube Q1. The other end of the resistor R6 is divided into two paths and respectively connected to one end of the resistor R5 and one end of the resistor R7. The other ends of the resistor R7 and the capacitor C6 are both grounded GND, the positive electrode of the voltage regulator D2 is grounded GND, the drain D of the MOS tube Q1 is divided into two paths and respectively connected to one end of the resistor R8 and the base B of the transistor Q2, the collector C of the transistor Q2 is grounded, the positive electrode of the voltage regulator D3 is grounded GND, the negative electrode of the voltage regulator D3 is connected to the piezoelectric signal output end, the emitter E of the transistor Q2 is connected to the piezoelectric signal output end, and the other ends of the resistor R8, the resistor R5 and the capacitor C5 are all connected to the piezoelectric signal output end.

6. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to claim 5, characterized in that: The resistance of the resistor R2 is ten times greater than the resistance of the resistor R3, and the capacity of the capacitor C2 is twice greater than that of the capacitor C3.

7. The ICP sensor circuit with high efficiency, wide frequency response and high dynamic range according to claim 5, characterized in that: The MOS transistor Q1 is an N-channel MOS transistor.

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