CN-121596288-B - Piezoelectric MEMS ultrasonic sensor ranging circuit and ranging method

CN121596288BCN 121596288 BCN121596288 BCN 121596288BCN-121596288-B

Abstract

The invention belongs to the field of piezoelectric MEMS sensors, and relates to a piezoelectric MEMS ultrasonic sensor ranging circuit and a ranging method, wherein the ranging circuit comprises an MCU, a high-voltage pulse driving circuit, a self-adaptive impedance matching network, a piezoelectric MEMS ultrasonic transducer, an active damping network, a preamplifier, a band-pass filter and a time gain controller; the high-voltage pulse driving circuit can greatly improve the emission sound pressure of the transducer and the measurement range, one end of the damping resistor is provided with a controllable switch, the emission efficiency can be improved, residual vibration is reduced, and therefore the measurement blind area is reduced.

Inventors

WANG FEI
YANG JING
ZHANG WEN
LIU MIN
Xiang Xingxu
WANG LU
WANG DENGPAN
LIAO SONGLIN
TIAN YUAN
HUANG JING

Assignees

中国电子科技集团公司第二十六研究所

Dates

Publication Date: 20260512
Application Date: 20260129

Claims (7)

1. The piezoelectric MEMS ultrasonic sensor ranging circuit is characterized by comprising an MCU, a high-voltage pulse driving circuit, a self-adaptive impedance matching network, a piezoelectric MEMS ultrasonic transducer, an active damping network, a preamplifier, a band-pass filter and a time gain controller; The MCU is respectively connected with the high-voltage pulse driving circuit, the active damping network and the self-adaptive impedance matching network, and the active damping network is connected with the piezoelectric MEMS ultrasonic transducer in parallel; the output end of the high-voltage pulse driving circuit is connected with the input end of the self-adaptive impedance matching network and the input end of the preamplifier, the output end of the self-adaptive impedance matching network is connected with the input end of the piezoelectric MEMS ultrasonic transducer, the output end of the piezoelectric MEMS ultrasonic transducer is connected with the input end of the preamplifier, the output end of the preamplifier is connected with the input end of the band-pass filter, the output end of the band-pass filter is connected with the input end of the time gain controller, and the output end of the time gain controller is connected with the MCU; The active damping network comprises an active damping switch and a damping resistor, wherein one end of the active damping switch is connected with one end of the damping resistor, the other end of the active damping switch is connected with the input end of the piezoelectric MEMS ultrasonic transducer, and the other end of the damping resistor is connected with the output end of the piezoelectric MEMS ultrasonic transducer; the MCU comprises a pulse emission controller, a damping controller and an impedance controller; The pulse emission controller is connected with the damping controller and used for controlling the damping controller to output high level or low level; the damping controller is connected with the active damping network and used for controlling the opening or closing of the active damping network; the impedance controller is connected with the self-adaptive impedance matching network and used for controlling the impedance of the self-adaptive impedance matching network; The high-voltage pulse driving circuit comprises resistors R1-R5, MOSFET tubes M1-M2, a capacitor C1, a direct current power supply DC and a pulse transformer T1, wherein the input end of the pulse transformer T1 sequentially comprises 1 pin, 2 pin and 3 pin, and the output end sequentially comprises 5 pin and 4 pin; One end of the resistor R4 is connected with positive pulse, the other end of the resistor R4 is connected with the grid electrode of the MOSFET M1, the source electrode of the MOSFET M1 is connected with one end of the resistor R5, the other end of the resistor R5 is grounded, and the drain electrode of the MOSFET M1 is connected with the 1 pin of the pulse transformer T1; One end of the resistor R2 is connected with the negative pulse, the other end of the resistor R2 is connected with the grid electrode of the MOSFET tube M2, the source electrode of the MOSFET tube M2 is connected with one end of the resistor R3, the other end of the resistor R3 is grounded, and the drain electrode of the MOSFET tube M2 is connected with the 3 pin of the pulse transformer T1; one end of the resistor R1 is connected with the direct current power supply DC, the other end of the resistor R1 is respectively connected with the 2 pin of the pulse transformer T1 and one end of the capacitor C1, and the other end of the capacitor C1 is grounded; The active damping switch comprises resistors R1-R9, transistors Q1-Q4, a power supply VCC, a power supply VSS and a power supply VDD; The damping controller is respectively connected with one end of a resistor R1, one end of a resistor R4 and a source electrode of a transistor Q1, the other end of the resistor R4 and a grid electrode of the transistor Q1 are connected with a power supply VCC, a drain electrode of the transistor Q1 is respectively connected with one end of a resistor R5 and one end of a resistor R8, the other end of the resistor R5 is connected with a power supply VDD, the other end of the resistor R8 is respectively connected with one end of a resistor R9 and the grid electrode of the transistor Q3, and the other end of the resistor R9 and the source electrode of the transistor Q3 are grounded and the input end of the piezoelectric MEMS ultrasonic transducer; The other end of the resistor R1 is respectively connected with one ends of the resistor R2 and the resistor R3, the other end of the resistor R2 is connected with a power supply VSS, the other end of the resistor R3 is connected with a grid electrode of the transistor Q2, a source electrode of the transistor Q2 is connected with the power supply VSS, a drain electrode of the transistor Q2 is respectively connected with one ends of the resistor R6 and the resistor R7, the other end of the resistor R6 is grounded, the other end of the resistor R7 is connected with a grid electrode of the transistor Q4, a drain electrode of the transistor Q4 is connected with one end of a damping resistor, a source electrode of the transistor Q4 is connected with a drain electrode of the transistor Q3, and the other end of the damping resistor is connected with an output end of the piezoelectric MEMS ultrasonic transducer.
2. The piezoelectric MEMS ultrasonic sensor ranging circuit according to claim 1, wherein the MCU further comprises an ADC, a residual vibration detector and a ranging module, wherein the input end of the ADC is connected with the output end of the time gain controller, the output end of the ADC is respectively connected with the input ends of the residual vibration detector and the ranging module, and the ADC is an analog-to-digital converter.
3. The piezoelectric MEMS ultrasonic sensor ranging circuit of claim 1, wherein the pulse emission controller of the MCU generates two pulses, one of which is a positive pulse and the other of which is a negative pulse, the two pulses being equal in number, equal in frequency and opposite in phase.
4. The piezoelectric MEMS ultrasonic sensor ranging circuit according to claim 1, wherein the self-adaptive impedance matching network comprises a programmable capacitor and an inductor, one end of the programmable capacitor is connected with one end of the inductor, the other end of the programmable capacitor is connected with the input end of the piezoelectric MEMS ultrasonic transducer, the other end of the inductor is connected with the output end of the high-voltage pulse driving circuit, and the programmable capacitor is connected with the impedance controller.
5. The piezoelectric MEMS ultrasonic transducer ranging circuit of claim 1 wherein the active damping switch is connected to the damping controller.
6. A distance measuring method based on the piezoelectric MEMS ultrasonic sensor distance measuring circuit according to any one of claims 1 to 5, comprising: S1, setting a capacitor of a self-adaptive impedance matching network according to a piezoelectric MEMS ultrasonic sensor ranging circuit; S2, the pulse emission controller emits N emission pulses, and meanwhile, the damping controller turns off an active damping switch of the active damping network for low level; s3, after the emission of N emission pulses is completed, the damping controller closes the active damping switch of the active damping network to a high level, and the pulse emission controller delays the emission of N/5 active damping pulses for half a period; S4, transmitting the pulse and the active damping pulse to the piezoelectric MEMS ultrasonic transducer through the high-voltage pulse driving circuit and the self-adaptive impedance matching network, wherein the piezoelectric MEMS ultrasonic transducer generates ultrasonic waves, and the ultrasonic waves are transmitted to the tested metal plate through air and then reflected back; S5, the ultrasonic echo signals are transmitted to the ADC through the preamplifier, the band-pass filter and the time gain controller to be digitized, and the distance measuring module calculates the distance according to the digitized ultrasonic echo signals.
7. The ranging method as defined in claim 6, wherein setting the capacitance of the adaptive impedance matching network comprises: s11, fixing the distance between the piezoelectric MEMS ultrasonic transducer and the metal plate to be tested, using an impedance controller to set the capacitance of the self-adaptive impedance matching network as an initial capacitance, and using a damping controller to disconnect an active damping switch of an active damping network; s12, transmitting short pulses by using a pulse transmitting controller, wherein the short pulses are transmitted to the piezoelectric MEMS ultrasonic transducer through a high-voltage pulse driving circuit and a self-adaptive impedance matching network; S13, generating ultrasonic waves by the piezoelectric MEMS ultrasonic transducer, transmitting the ultrasonic waves to the tested metal plate through air, then reflecting the echo, receiving the reflected echo by the piezoelectric MEMS ultrasonic transducer, and converting the echo into an electric signal, namely an ultrasonic echo signal; s14, the ultrasonic echo signals are transmitted to a residual vibration detector through a pre-amplifier, a band-pass filter, a time gain controller and an ADC, and the residual vibration detector extracts the amplitude of the received signals; And S15, judging whether all the capacitors of the self-adaptive impedance matching network are traversed, if so, setting the capacitor of the self-adaptive impedance matching network as the capacitor corresponding to the highest amplitude by using the impedance controller, otherwise, setting the capacitor of the self-adaptive impedance matching network as the next capacitor by using the impedance controller, and returning to the step S12.

Description

Piezoelectric MEMS ultrasonic sensor ranging circuit and ranging method Technical Field The invention belongs to the field of piezoelectric MEMS sensors, and relates to a piezoelectric MEMS ultrasonic sensor ranging circuit and a ranging method. Background The piezoelectric MEMS transducer is a lead zirconate titanate (PZT) or aluminum nitride (AlN) film and the like film generates mechanical vibration under the action of an electric field, the process is that the piezoelectric MEMS transducer emits ultrasonic waves by the inverse piezoelectric effect, when receiving the acoustic waves, the piezoelectric film vibrates to generate charges at two ends of an electrode, and the process is that the positive piezoelectric effect receives ultrasonic echoes. The piezoelectric MEMS transducer can be applied to the fields of medical imaging, consumer electronics, automobile electronics and the like, and is used for measuring the flight time and echo amplitude between transmitting and receiving echoes in the application directions of distance sensing, fingerprint imaging, medical imaging and the like, and different imaging algorithms are used according to practical application requirements so as to measure the distance between a sensor and a measured object or image a measured area. The conventional piezoelectric MEMS ultrasonic sensor ranging circuit consists of a transmitting circuit, a piezoelectric MEMS transducer, a receiving circuit and a controller, wherein the working flow is that the transmitting circuit transmits pulses with specified number to the piezoelectric MEMS transducer to generate ultrasonic waves, the ultrasonic waves are reflected by a measured object after being transmitted, the piezoelectric MEMS transducer converts the reflected ultrasonic waves into electric signals, the receiving circuit amplifies and filters echo signals, the flight time between the transmitting and receiving echoes is calculated by the controller, and the distance between the piezoelectric MEMS transducer and the measured object can be calculated by combining the sound velocity of a propagation medium. The existing ranging circuit has the following problems: 1. The measurement blind area and the measurement distance cannot be combined, the common measurement distance with small measurement blind area is also small, and the common measurement blind area with large measurement distance is larger; 2. the ringing effect is not enough to inhibit, after the emission, residual vibration exists in the piezoelectric MEMS transducer, so that the absolute value of the dead zone of the sensor is larger even if the measuring dead zone is small, the residual vibration time after the emission is over 1ms (200 kHz PMUT), and the minimum detection distance is limited to be over 10cm; 3. The lack of dynamic impedance matching, the fixed LC matching network only adapts the nominal impedance, resulting in an impedance shift of + -15% when the ambient temperature changes by 20 ℃, resulting in a drop in energy transfer efficiency of more than 40%. In conclusion, the piezoelectric MEMS ultrasonic system is interfered by residual vibration during short-distance measurement, the measurement distance is short, and the emission efficiency is low. Disclosure of Invention In order to solve the problems in the prior art, the invention adopts a piezoelectric MEMS ultrasonic sensor ranging circuit, which comprises an MCU, a high-voltage pulse driving circuit, a self-adaptive impedance matching network, a piezoelectric MEMS ultrasonic transducer, an active damping network, a preamplifier, a band-pass filter and a time gain controller; The MCU is respectively connected with the high-voltage pulse driving circuit, the active damping network and the self-adaptive impedance matching network, the active damping network is connected with the piezoelectric MEMS ultrasonic transducer in parallel, the output end of the high-voltage pulse driving circuit is connected with the input end of the self-adaptive impedance matching network and the input end of the preamplifier, the output end of the self-adaptive impedance matching network is connected with the input end of the piezoelectric MEMS ultrasonic transducer, the output end of the piezoelectric MEMS ultrasonic transducer is connected with the input end of the preamplifier, the output end of the preamplifier is connected with the input end of the band-pass filter, the output end of the band-pass filter is connected with the input end of the time gain controller, and the output end of the time gain controller is connected with the MCU. On the other hand, the invention adopts a distance measuring method based on the piezoelectric MEMS ultrasonic sensor distance measuring circuit, which comprises the following steps: S1, setting a capacitor of a self-adaptive impedance matching network according to a piezoelectric MEMS ultrasonic sensor ranging circuit; S2, the pulse emission controller emits N emission pulses, and m