CN106247915B - A kind of PLCD sensor signal conditioning circuits followed based on peak value and its method - Google Patents

Abstract

The invention discloses a peak-following-based PLCD sensor signal conditioning circuit and a method thereof, comprising a sine wave generator circuit, a PLCD sensor, a pre-processing circuit, a phase detection circuit, a peak-following circuit, and an output processing circuit. The sine wave generator circuit drives the excitation coil of the PLCD sensor. After the output signal of the induction coil of the PLCD sensor passes through the pre-processing circuit, on the one hand, it is input to the phase detection circuit together with the output signal of the sine wave generator circuit to judge whether the displacement of the sensor is positive or negative. ; On the other hand, the input peak follower circuit detects the peak voltage of the output signal, and finally through the output processing circuit, a voltage signal representing the magnitude and direction of displacement is obtained. Compared with the conventional rectification filter conditioning circuit, the invention quickly obtains the displacement by peak following, and has good dynamic characteristics. In addition, it solves the problems that the PLCD sensor is difficult to capture small signals near the zero position, and the positive and negative values are difficult to judge.

Description

A PLCD sensor signal conditioning circuit and method based on peak follower

technical field

The invention relates to a peak-following-based PLCD sensor signal conditioning circuit and a method thereof, belonging to the technical field of sensor signal processing.

Background technique

Compared with the mainstream non-contact displacement sensor LVDT sensor and magnetostrictive displacement sensor on the market, PLCD sensor has better reliability and adaptability, more compact structure, lower production cost, especially easy to install and use.

At present, foreign countries are vigorously developing PLCD sensor technology and have always been at the forefront of the world. The domestic research and development of permanent magnet linear non-contact displacement sensors is still in a blank stage, and the main difficulty in the production of PLCD sensors lies in the conditioning circuit of its output signal. Therefore, It is urgent to design a high-performance and reliable PLCD sensor signal conditioning circuit.

The key to the design of the PLCD sensor signal conditioning circuit is to obtain the amplitude of the sensing signal quickly and accurately, and to judge the phase of the signal. For the detection of the amplitude of the electromagnetic induction signal, the method of precision rectification is generally adopted, but there are problems of slow response and poor real-time performance. The invention proposes a PLCD sensor signal conditioning method based on peak following, which can quickly obtain a voltage signal representing the magnitude and direction of displacement.

The Chinese patent with the publication number CN 103297005A discloses a peak detection circuit. The patent states that it can detect peaks in a linear and fast manner, with a wide operating frequency band and low power consumption, but it is only suitable for high-frequency linear systems and cannot be applied to PLCD sensors. low frequency signal peak detection.

The Chinese patent with the publication number CN 201748940U discloses a peak detection circuit controlled by a single-chip microcomputer. The patent simply uses a capacitor to maintain the voltage and cannot maintain high precision, and although the discharge of the capacitor by a single-chip microcomputer can achieve real-time performance, it is too complicated and cumbersome. This patent cannot detect low-amplitude signals due to the forward conduction voltage drop of the diode.

The Chinese patent with the publication number CN 202133712U discloses an integrated packaged peak detection circuit. This patent uses logic circuits to achieve good real-time performance, but the circuit is still relatively cumbersome, and it is easy to cause internal triggers when the input signal has noise. false triggers, and low-amplitude signals cannot be detected.

Contents of the invention

Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a PLCD sensor signal conditioning circuit and method based on peak follower, which can quickly obtain the displacement size through peak follower, and has good dynamic characteristics. It is difficult to capture small signals near the bit, and it is difficult to judge the positive and negative values.

Technical scheme: in order to achieve the above object, the technical scheme adopted in the present invention is:

A PLCD sensor signal conditioning circuit based on peak follower, comprising a sine wave generator circuit, a PLCD sensor, a preprocessing circuit, a phase detection circuit, a peak follower circuit, and an output processing circuit; wherein,

The signal output end of the sine wave generator is respectively connected with the signal input end of the PLCD sensor and the first input end of the phase detection circuit;

The signal output end of the PLCD sensor is connected with the signal input end of the pre-processing circuit;

The two signal output terminals of the pre-processing circuit are respectively connected to the second signal input terminal of the phase detector circuit and the first signal input terminal of the peak follower circuit;

The first signal output end of the phase detection circuit is connected to the second signal input end of the peak follower circuit; the second signal output end of the phase detection circuit and the signal output end of the peak follower circuit are respectively connected to the The two signal input terminals of the output processing circuit are connected.

Further, the PLCD sensor is composed of a magnetic core, excitation coils wound symmetrically at both ends of the magnetic core, and an induction coil evenly wound in the middle of the magnetic core; the output signal of the generator circuit of the sine wave is input Into the excitation coil, an alternating magnetic field is generated to excite the induction coil, and the output signal of the induction coil is connected to the pre-processing circuit for conditioning.

Further, the pre-processing circuit is composed of a low-pass filter circuit, a voltage amplification circuit, and a voltage bias circuit, and the signal output terminals of the low-pass filter circuit are respectively connected to the signal inputs of the voltage amplification circuit and the voltage bias circuit. terminal connection;

The signal output terminal of the voltage amplification circuit is connected to the hysteresis comparator in the phase detection circuit; the signal output terminal of the voltage bias circuit is connected to the input terminal of the dual-channel detection circuit in the peak follower circuit.

Further, the phase detection circuit is composed of two hysteresis comparators and a D flip-flop, wherein the two hysteresis comparators are No. 1 hysteresis comparator and No. 2 hysteresis comparator respectively; The D flip-flop includes two input terminals, which are respectively a D input terminal and a clock input terminal, and also includes a Q output terminal, and the Q output terminal is the second signal output terminal of the phase detection circuit, which is connected to the output terminal The signal input end connection of the processing circuit;

The output signal of the sine wave generator circuit is input into the No. 1 hysteresis comparator, converted into an excitation coil square wave signal, and then input into the D input terminal of the D flip-flop;

The output signal of the voltage amplifying circuit of one of the output terminals in the pre-processing circuit is input to the No. 2 hysteresis comparator, converted into a square wave signal of the induction coil, and input to the clock input terminal of the D flip-flop on the one hand , on the other hand input to the logic gating circuit in the peak follower circuit.

Further, the peak follower circuit is composed of a dual-channel detection circuit, a logic gating circuit, an electromagnetic switch and a diode;

Wherein, the signal output ends of the dual-channel detection circuit and the logic gating circuit are connected to the signal input end of the electromagnetic switch, and the signal output end of the electromagnetic switch is connected to one of the signal input ends of the output processing circuit ; The dual-channel detection circuits are respectively connected to the logic gating circuit through the diodes;

The output signal of the voltage bias circuit of one of the output terminals in the pre-processing circuit is input to the signal input terminal of the dual-channel detection circuit, which is the first signal input terminal of the peak follower circuit; The first signal output terminal of the channel detection circuit is a peak voltage output terminal, which is connected to the electromagnetic switch, and the second signal output terminal is a charging and discharging terminal of the holding capacitor, which is connected to the logic gating circuit;

Described logic gating circuit is made of monostable flip-flop, bistable flip-flop and two AND gate circuits; The signal input end of the logic gating circuit is the signal input end of the monostable flip-flop and the bistable flip-flop, that is, the second signal input end of the peak follower circuit, and the Q output end of the monostable flip-flop The Q output terminal of the bistable flip-flop is connected with the signal input terminal of the AND gate circuit, and the Q output terminal of the monostable flip-flop is connected with the Q output terminal of the bistable flip-flop. The output end is connected to the signal input end of the AND gate circuit, and the output end of the AND gate circuit is the A and B output ends of the logic gating circuit.

Further, the output processing circuit is composed of a No. 2 voltage bias circuit, an inverse proportional operation circuit and an electromagnetic switch connected in sequence, and the output signals of the No. 2 voltage bias circuit are respectively input to the inverse proportional operation circuit and electromagnetic switches;

The output signal end of the peak follower circuit is connected to the No. 2 voltage bias circuit, and the second signal output end of the phase detection circuit is input to the No. 2 electromagnetic switch.

A method based on a peak-following PLCD sensor signal conditioning circuit, comprising the following steps:

1) The output signal of the sine wave generator is respectively sent to the phase detector circuit and the PLCD sensor;

2) The output signal of the induction coil of the PLCD sensor is conditioned by the pre-processing circuit, specifically two types, one is the hysteresis that the output signal after the pre-processing circuit performs low-pass filtering and signal amplification conditioning is input to the phase detection circuit The comparator, the other is a low-pass filter and a positive bias voltage added to the pre-processing circuit, which is input to the peak follower circuit to obtain a peak voltage with a bias value added;

3) The phase detection circuit judges the positive or negative of the displacement of the PLCD sensor according to the received output signal of the sine wave generator and the pre-processing circuit; outputs the square wave signal of the induction coil to the peak follower circuit, and outputs the positive and negative voltage logic gate signal to the In the output processing circuit;

4) The peak follower circuit detects the peak voltage of the received signal, and outputs the result to the output processing circuit;

5) Obtain a voltage signal representing the magnitude and direction of the displacement through the output processing circuit.

Further, the specific method for judging the positive and negative of the displacement of the PLCD sensor by the phase detection circuit in the step 3) is: when the square wave signal phase of the excitation coil of the PLCD sensor is ahead of the square wave signal of the induction coil of the PLCD sensor, the The Q output terminal of the D flip-flop of the PLCD sensor outputs a high level, and the control output processing circuit gates a positive voltage; when the square wave signal phase of the excitation coil lags behind the square wave signal of the induction coil, the The Q output terminal outputs a low level, and controls the output processing circuit to strobe the negative voltage.

Further, in the step 4), the specific method for the peak follower circuit to detect the peak voltage of the received signal is:

4-1) In the first cycle of the two input signals of the peak follower circuit, the dual-channel detection circuit follows the peak voltage, wherein,

The A output terminal of the logic gating circuit outputs a high level, and the No. 1 diode is not conducting, blocking the discharge of the capacitor of the corresponding No. 2 detection circuit;

The B output terminal of the logic gating circuit outputs a low level, and the No. 2 diode is turned on, so that the capacitor of the corresponding No. 1 detection circuit is quickly discharged and reset, and the new peak voltage is re-detected;

The C output terminal of the logic gating circuit outputs a high level to control the electromagnetic switch to gating the output voltage of the second detection circuit;

4-2) During the next cycle of the two input signals, the dual-channel detection circuit follows the peak voltage, where,

The A output terminal of the logic gating circuit outputs a high level, and the first diode is turned on, so that the capacitor of the corresponding second detection circuit is quickly discharged and reset, and the new peak voltage is re-detected;

The B output terminal of the logic gating circuit outputs a low level, and the No. 2 diode is not conducting, blocking the discharge of the capacitor of the corresponding No. 1 detection circuit;

The C output terminal of the logic gating circuit outputs a high level to control the electromagnetic switch to gating the output voltage of the second detection circuit;

In this way, the peak voltage is repeatedly detected to achieve fast follow-up.

Further, the specific method that the output processing circuit obtains the voltage signal representing the displacement magnitude and direction in the step 5) is:

The signal input terminal of the output processing circuit is provided with a No. 2 voltage bias circuit, and the No. 2 voltage bias circuit adds a negative bias voltage of the same size to the forward biased peak voltage to restore the true peak voltage value, Then through the inverse proportional operation circuit, it is converted into peak negative voltage with equal size and opposite sign, and the two are input into the electromagnetic switch, and the logic gating of the positive and negative voltage is realized by the phase detection circuit (4), and the output represents the displacement size and direction of the PLCD sensor. voltage signal;

The No. 2 voltage bias circuit and the peak voltage with bias value obtained in the step 2), that is, the bias voltage value is lower than the forward conduction voltage drop of the diode, which ensures that the diode is in the micro conduction voltage when it is working. pass status.

Beneficial effects: the peak-following-based PLCD sensor signal conditioning circuit and its method provided by the present invention, compared with the prior art, compared with the conventional rectification and filtering conditioning circuit, the present invention quickly obtains displacement and dynamic characteristics through peak-following Well, in addition, it solves the problem that the small signal of the PLCD sensor is difficult to capture near the zero position, and the positive and negative values are difficult to judge.

Description of drawings

Fig. 1 is a flow chart of PLCD sensor conditioning circuit;

Fig. 2 is a preprocessing circuit diagram;

Fig. 3 is a phase detector circuit diagram;

Fig. 4 is a peak follower circuit diagram;

Fig. 5 is an output processing circuit diagram;

Figure 6 is a logic gating circuit diagram

Figure 7 is a simulation diagram of the Multisim circuit.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings.

The invention is a PLCD sensor signal conditioning circuit and method based on peak following, which can obtain the effective value of the output signal of the PLCD sensor at the fastest speed, can judge the displacement direction, and can detect the small signal of the zero attachment. The invention includes a sine wave generator circuit, a PLCD sensor, a preprocessing circuit, a phase detection circuit, a peak follower circuit and an output processing circuit. The sine wave generator circuit drives the excitation coil of the PLCD sensor. After the output signal of the induction coil of the PLCD sensor passes through the pre-processing circuit, on the one hand, it is input to the phase detection circuit together with the output signal of the sine wave generator circuit to judge whether the displacement of the sensor is positive or negative. ; On the other hand, the input peak follower circuit detects the peak voltage of the output signal, and finally through the output processing circuit, a voltage signal representing the magnitude and direction of displacement is obtained. Compared with the conventional rectification filter conditioning circuit, the invention quickly obtains the displacement by peak following, and has good dynamic characteristics. In addition, it solves the problems that the PLCD sensor is difficult to capture small signals near the zero position, and the positive and negative values are difficult to judge.

The specific content is as follows:

As shown in Figure 1, the PLCD sensor signal conditioning circuit based on peak follower, its structure includes sine wave generator circuit 1, PLCD sensor 2, pre-processing circuit 3, phase detection circuit 4, peak follower circuit 5, output processing circuit 6 , wherein the signal output end of the sine wave generator 1 is connected with the signal input end of the PLCD sensor 2 and the first input end of the phase detection circuit 4, and the signal output end of the PLCD sensor 2 is connected with the signal input end of the preprocessing circuit 3, Two signal output terminals of the pre-processing circuit 3 are respectively connected with the second signal input terminal of the phase detection circuit 4 and the first signal input terminal of the peak follower circuit 5, and the first signal output terminal of the phase detection circuit 4 is connected with the peak follower circuit 5 is connected to the second signal input end, and the second signal output end of the phase detection circuit 4 and the signal output end of the peak follower circuit 5 are respectively connected to the two signal input ends of the output processing circuit 6 .

The PLCD sensor 2 is composed of a magnetic core, an excitation coil symmetrically wound at both ends of the magnetic core and an induction coil evenly wound in the middle of the magnetic core. The output signal of the sine wave generator circuit 1 is input into the excitation coil to generate an alternating magnetic field The induction coil is excited, and the output signal of the induction coil is connected to the pre-processing circuit 3 for conditioning.

The sine wave generator circuit 1 is composed of an RC sine wave oscillator circuit, an in-phase follower circuit, and an OCL circuit that eliminates step distortion, and can output a stable sine wave signal to the PLCD sensor 2 to drive the excitation coil of the PLCD sensor 2, and the induction coil Excited to generate corresponding induced electromotive force.

As shown in FIG. 2 , the pre-processing circuit 3 is composed of a low-pass filter circuit 7 , a voltage amplification circuit 8 , and a voltage bias circuit 9 . The output signal of the induction coil of the PLCD sensor 2 is input to the pre-processing circuit 3. First, the output signal of the induction coil is low-pass filtered by the low-pass filter circuit 7 to filter out high-frequency noise, and the voltage amplifier circuit 8 appropriately amplifies the filtered signal. After multiple times, it is input to the hysteresis comparator in the phase detection circuit 4, which ensures that the small-amplitude signal can also be converted into a stable square wave. The voltage bias circuit 9 adds a positive bias voltage to the filtered signal and inputs it to the The peak voltage with added offset value is obtained in the peak follower circuit 5, which ensures that the peak voltage value can also be collected for small-amplitude signals.

As shown in Figure 3, the phase detection circuit 4 is composed of two hysteresis comparators 10, 11 and a D flip-flop 12, the output signal of the sine wave generator circuit 1 is input into the hysteresis comparator 10, and converted into an excitation coil The square wave signal is input to the D input terminal of the D flip-flop 12; the output signal of the voltage amplifying circuit 8 is input to the hysteresis comparator 11, and converted into an induction coil square wave signal, which is input to the clock input CP of the D flip-flop 12 on the one hand. On the other hand, it is input to the logic gating circuit 15 in the peak follower circuit 5. When the square wave signal of the excitation coil is ahead of the square wave signal of the induction coil, the Q output terminal of the D flip-flop 12 outputs a high level, and the control output The processing circuit 6 gates the positive voltage; when the square wave signal of the exciting coil lags behind the square wave signal of the induction coil, the Q output terminal of the D flip-flop 12 outputs a low level, and the output processing circuit 6 is controlled to gate the negative voltage.

As shown in Figure 4, the peak follower circuit 5 is composed of dual-channel detection circuits 13, 14, logic gating circuit 15, electromagnetic switch 16 and diodes 17, 18, wherein the first signal output terminals of the detection circuits 13, 14 are peak voltage The output terminal, the second signal output terminal is the charge and discharge terminal of the holding capacitor, the output signal of the voltage bias circuit 9 is input to the signal input terminals of the detection circuits 13 and 14, and the output signal of the hysteresis comparator 11 is input to the logic gating circuit 15 In the first cycle of the two input signals, the detection circuits 13 and 14 follow the peak voltage, the A output terminal outputs a high level, the diode 17 blocks the capacitor discharge of the detection circuit 13, and the B output terminal outputs a low voltage. level, the conduction of diode 18 makes the capacitance of detection circuit 14 quickly discharge and reset, and detects the new peak voltage again, and the C output terminal outputs a high level to control electromagnetic switch 16 to strobe the output voltage of detection circuit 13; During the cycle, the detection circuits 13 and 14 follow the peak voltage, the A output terminal outputs a low level, the diode 17 is turned on to reset the capacitance of the detection circuit 13, and the new peak voltage is re-detected, the B output terminal outputs a high level, and the diode 18 blocks the capacitor discharge of the detection circuit 14, the C output terminal outputs a low level to control the electromagnetic switch 16 to gate the output voltage of the detection circuit 14, and in this way repeatedly detects the peak voltage and realizes fast following.

As shown in Figure 6, logic gating circuit 15 is made up of monostable flip-flop 22, bistable flip-flop 23 and two AND gate circuits 24,25; The output signal of the number hysteresis comparator 11 is input to the signal input end of the logic gating circuit 15, which is the signal input end of the monostable flip-flop 22 and the bistable flip-flop 23, which is the peak follower circuit The second signal input end of 5; the Q output end of the monostable flip-flop 22 and the Q output end of the bistable flip-flop 23 are connected with the signal input end of the gate circuit 24, and the Q output end of the monostable flip-flop 22 is connected with the Q output end of the bistable flip-flop 23 flip-flop 23's The output terminal is connected to the signal input terminal of the AND gate circuit 25, and the output terminals of the AND gate circuits 24 and 25 are the A and B output terminals of the logic gating circuit.

As shown in Figure 5, the output processing circuit 6 is composed of No. 2 voltage bias circuit 19, an inverse proportional operation circuit 20 and an electromagnetic switch 21. The peak voltage of the forward bias of No. 2 voltage bias circuit 19 is added Negative bias voltages of the same size restore the real peak voltage value, and then convert it into a peak negative voltage of equal size and opposite sign through the inverse proportional operation circuit 20, and input the two into the electromagnetic switch 21, and the positive and negative voltages are realized by the phase detector circuit 4 The logic strobe of the PLCD outputs a voltage signal representing the magnitude and direction of the displacement of the PLCD sensor.

Considering that the capacitance in the peak follower circuit 5 is discharged through the diode, and the forward conduction voltage drop of the diode causes the voltage of the small signal to fail to generate electricity, the bias voltage obtained by the voltage bias circuit 9 and the second voltage bias circuit 19 is The value should be appropriate, too large bias voltage will lead to excessive discharge of the capacitor, and in the subsequent charging process, the input signal and bias voltage will be charged at the same time to cause the holding voltage of the capacitor to be too high; too small bias voltage will cause when the input When the signal is less than the forward conduction voltage of the diode, the diode will not conduct. Since the input signal is a low frequency signal, the capacitor discharge time will be too long, which will affect the real-time followability; the ideal bias voltage should be slightly lower than the forward conduction voltage drop of the diode , the diode is slightly turned on while maintaining discharge, so that small-amplitude input signals can be detected.

Example

Using Multisim software to simulate the PLCD sensor signal conditioning circuit based on peak following, as shown in Figure 7. The thin gray line is the input signal of the excitation coil, the thin black line is the output signal of the induction coil, and the thick black line is the output signal of the output processing circuit 6 . The output signal can quickly and accurately follow the peak voltage of the induction coil, and when the input signal of the excitation coil is ahead of the output signal of the induction coil, the final output signal is positive; when the input signal of the excitation coil lags behind the output signal of the induction coil, the final output signal is negative. It shows that the PLCD sensor signal conditioning circuit based on peak following can accurately detect and output the voltage signal representing the displacement and direction of the PLCD sensor, while maintaining a good dynamic tracking effect.

The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements and modifications can also be made, and these improvements and modifications are also possible. It should be regarded as the protection scope of the present invention.

Claims (6)

1. A PLCD sensor signal conditioning circuit based on peak follower, characterized in that it includes a sine wave generator circuit (1), a PLCD sensor (2), a preprocessing circuit (3), a phase detection circuit (4), a peak value Follower circuit (5), output processing circuit (6); wherein, The signal output end of the sine wave generator (1) is respectively connected to the signal input end of the PLCD sensor (2) and the first input end of the phase detection circuit (4); The signal output end of the PLCD sensor (2) is connected to the signal input end of the pre-processing circuit (3); The two signal output terminals of the pre-processing circuit (3) are respectively connected to the second signal input terminal of the phase detection circuit (4) and the first signal input terminal of the peak follower circuit (5); The first signal output end of the phase detection circuit (4) is connected to the second signal input end of the peak follower circuit (5); the second signal output end of the phase detection circuit (4) is connected to the peak follower The signal output terminals of the circuit (5) are respectively connected to the two signal input terminals of the output processing circuit (6); The pre-processing circuit (3) is composed of a low-pass filter circuit (7), a voltage amplifier circuit (8), and a voltage bias circuit (9), and the signal output terminals of the low-pass filter circuit (7) are respectively connected to the The signal input terminals of the voltage amplifying circuit (8) and the voltage bias circuit (9) are connected; The signal output terminal of the voltage amplification circuit (8) is connected to the hysteresis comparator in the phase detection circuit (4); the signal output terminal of the voltage bias circuit (9) is connected to the peak follower circuit (5) The input end of the dual-channel detection circuit (13, 14) in; The phase detection circuit (4) is composed of two hysteresis comparators (10, 11) and a D flip-flop (12), wherein the two hysteresis comparators (10, 11) are number one A hysteresis comparator (10), a No. 2 hysteresis comparator (11); the D flip-flop (12) includes two input terminals, respectively a D input terminal and a clock input terminal, and also includes a Q output terminal, so The Q output terminal is the second signal output terminal of the phase detector circuit (4), connected to the signal input terminal of the output processing circuit (6); The output signal of the sine wave generator circuit (1) is input to the No. 1 hysteresis comparator (10), converted into a square wave signal for exciting the coil, and then input to the D input of the D flip-flop (12) end; The output signal of the voltage amplifying circuit (8) at one of the output terminals of the pre-processing circuit (3) is input to the No. 2 hysteresis comparator (11), and converted into a square wave signal of the induction coil, which is input to the The clock input terminal of the D flip-flop (12), on the other hand, is input to the logic gating circuit (15) in the peak follower circuit (5); The peak follower circuit (5) is composed of a dual-channel detection circuit (13, 14), a logic gating circuit (15), an electromagnetic switch (16) and diodes (17, 18); Wherein, the signal output terminals of the dual-channel detection circuit (13, 14) and the logic gating circuit (15) are connected to the signal input terminal of the electromagnetic switch (16), and the signal output terminal of the electromagnetic switch (16) The terminal is connected to one of the signal input terminals of the output processing circuit (6); the dual-channel detection circuits (13, 14) are respectively connected to the logic gating circuit (15) through the diodes (17, 18); The output signal of the voltage bias circuit (9) of one of the output terminals of the pre-processing circuit (3) is input to the signal input terminal of the dual-channel detection circuit (13, 14), that is, the peak following The first signal input terminal of the circuit (5); the first signal output terminal of the dual-channel detection circuit (13, 14) is the peak voltage output terminal, connected to the electromagnetic switch (16), and the second signal output terminal is The charging and discharging terminal of the holding capacitor is connected to the logic gating circuit (15); The logic gating circuit (15) is composed of a monostable flip-flop (22), a bistable flip-flop (23) and two AND gate circuits (24, 25); The output signal of the No. 2 hysteresis comparator (11) at one of the input terminals is input to the signal input terminal of the logic gating circuit (15), which is a monostable flip-flop (22) and a bistable flip-flop ( The signal input terminal of 23) is the second signal input terminal of the peak follower circuit (5); the Q output terminal of the monostable flip-flop (22) is connected with the Q output terminal of the bistable flip-flop (23) The signal input end of the AND gate circuit (24), the Q output end of the monostable flip-flop (22) and the Q output end of the bistable flip-flop (23) The output terminal is connected to the signal input terminal of the AND gate circuit (25), and the output terminals of the AND gate circuit (24, 25) are the A and B output terminals of the logic gating circuit; The output processing circuit (6) is composed of a No. 2 voltage bias circuit (19), an inverse proportional operation circuit (20) and a No. 2 electromagnetic switch (21) connected in sequence, and the No. 2 voltage bias circuit (19 ) output signals are respectively input to the inverse proportional operation circuit (20) and the second electromagnetic switch (21); The output signal terminal of the peak follower circuit (5) is connected to the No. 2 voltage bias circuit (19), and the second signal output terminal of the phase detection circuit (4) is input to the No. 2 electromagnetic switch (21 ). 2. The peak-following-based PLCD sensor signal conditioning circuit according to claim 1, characterized in that: the PLCD sensor (2) consists of a magnetic core, an excitation coil symmetrically wound at both ends of the magnetic core, and a uniform winding The induction coil in the middle of the magnetic core is composed; the output signal of the sine wave generator circuit (1) is input into the excitation coil to generate an alternating magnetic field to excite the induction coil, and the induction coil The output signal is connected to the pre-processing circuit (3) for conditioning. 3. a kind of method based on the PLCD sensor signal conditioning circuit of peak following according to claim 1, it is characterized in that: comprise the following steps: 1) The output signal of the sine wave generator (1) is respectively sent to the phase detector circuit (4) and the PLCD sensor (2); 2) The output signal of the induction coil of the PLCD sensor (2) is conditioned by the pre-processing circuit (3), specifically two types, one is the output signal after low-pass filtering and signal amplification conditioning by the pre-processing circuit (3) Input to the hysteresis comparator in the phase detection circuit (4), the other is low-pass filtered by the pre-processing circuit (3) and plus a positive bias voltage, input to the peak follower circuit (5) to obtain The peak voltage with the offset value added; 3) The phase detection circuit (4) judges the positive or negative of the displacement of the PLCD sensor according to the received output signal of the sine wave generator (1) and the pre-processing circuit (3); outputs the square wave signal of the induction coil to the peak follower circuit ( 5), outputting positive and negative voltage logic gate signals to the output processing circuit (6); 4) The peak follower circuit (5) detects the peak voltage of the received signal, and outputs the result to the output processing circuit (6); 5) Obtain a voltage signal representing the magnitude and direction of displacement through the output processing circuit (6). 4. The method of peak-following-based PLCD sensor signal conditioning circuit according to claim 3, characterized in that: the specific method for judging the positive and negative of the displacement of the PLCD sensor by the phase detection circuit (4) in the step 3) is: when When the square wave signal of the exciting coil of the PLCD sensor (2) is ahead of the square wave signal of the induction coil of the PLCD sensor (2), the Q output terminal of the D flip-flop (12) of the PLCD sensor (2) outputs high level, to control the output processing circuit (6) to select a positive voltage; when the phase of the excitation coil square wave signal lags behind the induction coil square wave signal, the Q output terminal of the D flip-flop (12) outputs a low level , to control the output processing circuit (6) to strobe the negative voltage. 5. The method of peak-following-based PLCD sensor signal conditioning circuit according to claim 3, characterized in that: in the step 4), the peak-following circuit (5) detects the specific method of the peak voltage of the received signal for: 4-1) In the first cycle of the two input signals of the peak follower circuit (5), the dual-channel detection circuit (13, 14) follows the peak voltage, wherein, The A output terminal of the logic gating circuit (15) outputs a high level, and the No. 1 diode (17) is not conducting, blocking the discharge of the capacitor of the corresponding No. 2 detection circuit (14); The B output terminal of the logic gating circuit (15) outputs a low level, and the second diode (18) is turned on, so that the capacitor of the corresponding first detection circuit (13) is quickly discharged and reset, and a new peak voltage is re-detected; The C output terminal of the logic gating circuit (15) outputs a high level to control the electromagnetic switch (16) to gating the output voltage of the No. 1 detection circuit (13); 4-2) During the next period of the two input signals, the dual-channel detection circuit (13, 14) follows the peak voltage, where, The A output terminal of the logic gating circuit (15) outputs a high level, and the No. 1 diode (17) is turned on, so that the capacitor of the corresponding No. 2 detection circuit (14) is quickly discharged and reset, and a new peak voltage is re-detected; The B output terminal of the logic gating circuit (15) outputs a low level, and the second diode (18) is not conducting, blocking the corresponding capacitor discharge of the first detection circuit (13); The C output terminal of the logic gating circuit (15) outputs a high level to control the electromagnetic switch (16) to gating the output voltage of the second detection circuit (14); In this way, the peak voltage is repeatedly detected to achieve fast follow-up. 6. The method of peak-following-based PLCD sensor signal conditioning circuit according to claim 3, characterized in that: the output processing circuit (6) in the step 5) obtains the voltage signal representing the magnitude and direction of the displacement in a specific way as follows: : The signal input terminal of the output processing circuit (6) is provided with a No. 2 voltage bias circuit (19), and the No. 2 voltage bias circuit (19) adds a negative bias of the same magnitude to the forward biased peak voltage Set the voltage to restore the real peak voltage value, and then convert it into a peak negative voltage with equal size and opposite sign through the inverse proportional operation circuit (20). The two are input to the No. 2 electromagnetic switch (21), and are realized by the phase detection circuit (4). Logic gating of positive and negative voltages, outputting voltage signals representing the magnitude and direction of PLCD sensor displacement; The No. 2 voltage bias circuit (19) and the peak voltage with bias value obtained in the step 2), that is, the bias voltage value is lower than the forward conduction voltage drop of the diodes (17, 18), ensuring When the diodes (17, 18) work, they are in a slightly conducting state.