CN210037723U - CMUT signal conversion circuit - Google Patents

Abstract

The utility model provides a CMUT signal conversion circuit, which comprises a transmitting sub-circuit, a high-speed protection sub-circuit, an impedance conversion amplifying sub-circuit and a power supply sub-circuit; the output end of the transmitting sub-circuit is electrically connected with the CMUT; the synchronous signal output end of the transmitting sub-circuit is in signal connection with the synchronous signal input end of the high-speed protection sub-circuit; the input end of the high-speed protection sub-circuit is electrically connected with the CMUT; the output end of the high-speed protection sub-circuit is electrically connected with the input end of the impedance conversion amplification sub-circuit; the output end of the impedance conversion amplifying sub-circuit is electrically connected with an external ultrasonic instrument; the power supply sub-circuit supplies power to the high-speed protection sub-circuit and the impedance conversion amplification sub-circuit. The utility model provides a pair of CMUT signal conversion circuit, the current electronic components of make full use of to the design of retrenching has realized being connected of CMUT and current supersound instrument, through simple duplication combination, alright realize being connected of multichannel CMUT and supersound instrument.

Description

CMUT signal conversion circuit

Technical Field

The utility model relates to an ultrasonic detection detects technical field, and is more specific relates to a CMUT signal conversion circuit.

Background

Ultrasonic wave is a mechanical vibration wave, can be transmitted in air, liquid, solid and biological tissues, and is widely applied to the fields of biomedical imaging, industrial nondestructive testing and the like. In medical imaging, the ultrasonic wave can realize real-time imaging of biological tissue structures, has higher image resolution, and has no ionizing radiation compared with X-ray, CT and nuclear magnetic resonance detection technologies. Therefore, in medical clinical examinations, an ultrasonic imaging apparatus is one of the most common apparatuses. In the industry, ultrasound is often used for the detection of pipe welds, pressure vessel welds, forgings, castings, extruded bars, and sheet material internal conditions.

The ultrasonic transducer is a key component of the ultrasonic detection technology, and realizes mutual conversion between electric energy and ultrasonic energy. At present, ultrasonic transducers based on the piezoelectric principle are widely used, and common piezoelectric materials are generally piezoelectric ceramics. The piezoelectric ultrasonic transducer has high acoustic impedance, so that a plurality of acoustic impedance matching layers are required to be added when the ultrasonic probe is manufactured, the bandwidth of the probe is reduced, and the difficulty of the manufacturing process is increased. The processing technology of the piezoelectric material is different from the manufacturing technology of the integrated circuit, so the piezoelectric material is not suitable for manufacturing the ultrasonic probe with high integration level and high density. With the development of micro-machining technology, Capacitive Micromachined Ultrasonic Transducers (CMUTs) fabricated using micro-electro-mechanical systems (MEMS) technology were introduced in the last 90 th century. Compared with a piezoelectric ultrasonic transducer, the acoustic impedance of the CMUT is lower and can be adjusted, so that an impedance matching layer is not required to be added in the process of processing the ultrasonic probe, the difficulty in manufacturing the probe is reduced, and the bandwidth is also improved. The fabrication process of the CMUT is compatible with the process of an integrated circuit and commonly uses photolithography technology, so the CMUT is easy to manufacture a high-density, large-scale ultrasonic probe, and will be an alternative to the piezoelectric type ultrasonic transducer.

CMUT is a device based on the principle of electrostatic force, and its working principle is that under the action of ultrasonic wave, the vibrating membrane vibrates, thereby changing the capacitance value of the device. Under the action of the DC bias voltage, the charge between the CMUT electrodes changes periodically. However, the operating principle of the CMUT is different from that of the piezoelectric ultrasonic transducer, and the CMUT cannot be directly used in the existing ultrasonic instrument, and is not convenient for practical application.

SUMMERY OF THE UTILITY MODEL

The utility model discloses an overcome current CMUT in the application, have the technical defect that can't directly use on current ultrasonic instrument, provide a CMUT signal conversion circuit.

In order to solve the technical problem, the technical scheme of the utility model as follows:

a CMUT signal conversion circuit comprises a transmitting sub-circuit, a high-speed protection sub-circuit, an impedance conversion amplification sub-circuit and a power supply sub-circuit; wherein:

the output end of the transmitting sub-circuit is electrically connected with the CMUT;

the synchronous signal output end of the transmitting sub-circuit is in signal connection with the synchronous signal input end of the high-speed protection sub-circuit;

the input end of the high-speed protection sub-circuit is electrically connected with the CMUT;

the output end of the high-speed protection sub-circuit is electrically connected with the input end of the impedance conversion amplification sub-circuit;

the output end of the impedance conversion amplifying sub-circuit is electrically connected with an external ultrasonic instrument;

the power supply sub-circuit supplies power to the high-speed protection sub-circuit and the impedance conversion amplification sub-circuit.

In the above scheme, during the operation of the CMUT, a dc bias voltage is always applied to the device, and after the pulse emitted by the emission sub-circuit excites the CMUT to vibrate and generate ultrasonic waves, the CMUT is converted into a reception mode; the incident ultrasonic wave vibrates the membrane of the CMUT, so that the capacitance of the device is changed, the charge changed between the CMUT electrodes is converted into a current signal under the drive of a direct current bias voltage, and the current signal passes through the high-speed protection sub-circuit and then is subjected to impedance conversion and amplification through the impedance conversion amplification sub-circuit, so that the current signal can be connected to an external ultrasonic instrument.

The high-speed protection sub-circuit comprises a coupling capacitor C1, an integrated circuit chip U1 and a pull-down resistor R1; wherein:

the coupling capacitor C1 is connected in series with an SA pin of the integrated circuit chip U1 to serve as an INPUT end;

the pull-down resistor R1 is connected in series with the SB pin of the integrated circuit chip U1 and serves as a grounding end;

the integrated circuit chip U1 further comprises a GND pin, a VDD pin, a D pin, a VSS pin, an IN pin and an NC pin; wherein:

the GND pin and the VSS pin are both directly grounded;

the VDD pin is electrically connected with a 36V direct-current voltage source and serves as a V _ SW end;

the D pin is used as an ECHO end and is electrically connected with the input end of the impedance conversion amplification sub-circuit;

the synchronous signal TRIG of the transmitting sub-circuit is sent into the high-speed protection sub-circuit through the IN pin;

and the NC pin is empty.

IN the scheme, a CMUT INPUT signal enters an integrated circuit chip U1 from an INPUT end through a coupling capacitor C1, a synchronous signal of a high-voltage pulse of a transmitting sub-circuit is sent into the integrated circuit chip U1 through an IN pin, and a V _ SW end is connected to a 36V direct-current voltage source; the synchronization signal TRIG controls the integrated circuit chip U1 to be turned off when the CMUT is transmitting and to be turned on during CMUT reception; the ECHO signal conducted through the integrated circuit chip U1 is output from the ECHO terminal of the integrated circuit chip U1 to the impedance conversion and amplification sub-circuit of the next stage.

In the scheme, the high-speed protection sub-circuit realizes communication and isolation between the transmitting circuit and the receiving circuit. When the CMUT works, the CMUT needs to be continuously switched between a transmitting mode and a receiving mode; when the CMUT operates in a transmission mode, a high-voltage pulse signal is loaded on the CMUT electrode, and in order to prevent the high-voltage signal from damaging the low-voltage powered receiving circuit, a protection circuit capable of withstanding high voltage needs to be used for isolation. The high-speed protection sub-circuit can bear the high voltage of 36V, and the isolation of the CMUT transmitting and receiving signals is realized. The sub-circuit is opened before the transmission of the high voltage pulse and closed after the end of the transmission pulse to prevent the transmission pulse of the high voltage from entering the impedance transformation amplification sub-circuit and causing possible damage. The switch is opened and closed for less than 315ns, can bear high voltage up to 36V, and has the on-resistance of 14.5 omega.

The integrated circuit chip U1 is an ADG5419 circuit chip.

The impedance conversion amplification sub-circuit comprises an integrated circuit chip U2, a feedback resistor R2, a feedback capacitor C4, an output signal matching resistor R3, a power supply filter capacitor C2, a power supply filter capacitor C3, a power supply filter capacitor C5 and a power supply filter capacitor C6;

the integrated circuit chip U2 comprises three NC pins, a Vin-pin, a Vin + pin, a-Vs pin, a + Vs pin and a Vout pin; wherein:

the three NC pins are all empty;

the Vin-pin is used as an ECHO terminal and is electrically connected with the D pin;

the Vin + pin is directly grounded;

the-Vs pin is used as a VEE _ -5V end and is electrically connected with the power supply sub-circuit;

the + Vs pin is used as a VCC _5V end and is electrically connected with the power supply sub-circuit;

the Vout pin is connected in series with the OUTPUT signal matching resistor R3 to serve as an OUTPUT end and is electrically connected with an external ultrasonic instrument;

the feedback resistor R2 and the feedback capacitor C4 are connected in parallel, after the parallel connection, one end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the ECHO terminal, and the other end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the Vout pin;

the power supply filter capacitor C2 and the power supply filter capacitor C3 are connected in parallel, after the parallel connection, one end of the parallel connection is electrically connected with the VEE < -5 > V, and the other end of the parallel connection is directly grounded;

the power supply filter capacitor C5 and the power supply filter capacitor C6 are connected in parallel, one end of the parallel connection is electrically connected with VCC _5V, and the other end of the parallel connection is directly grounded.

In the above-described configuration, the CMUT membrane in the reception mode vibrates under the excitation of the incident ultrasonic wave, and the dc bias outputs the changed charge generation current to the impedance conversion amplification sub-circuit through the high-speed protection sub-circuit. The impedance conversion amplifying sub-circuit converts weak current into voltage and performs an amplified band-pass filter function.

Wherein the integrated circuit chip U2 is an OPA657 circuit chip.

The power supply sub-circuit comprises two parts of circuits, wherein the first part of circuit converts +12V direct current voltage into +5V direct current voltage and is electrically connected with the VCC _5V end; the second part circuit converts the +5V direct-current voltage obtained by the first part circuit into a-5V direct-current voltage, and is electrically connected with the VEE _ -5V end.

The first part circuit comprises an integrated circuit chip U3, a power supply filter capacitor C7 and a power supply filter capacitor C8;

the integrated circuit chip U3 is an LM1117 circuit chip and comprises an IN pin, an OUT pin and a GND pin; wherein:

the IN pin is electrically connected with a +12V direct-current voltage to serve as a VCC _12V end;

the OUT pin serves as a VCC _5V end, outputs +5V direct-current voltage for the second part of circuits, and is electrically connected with the + Vs pin;

the GND pin is directly grounded;

one end of the power supply filter capacitor C7 is electrically connected with the VCC _12V end, and the other end is directly grounded;

one end of the power supply filter capacitor C8 is electrically connected with the VCC _5V end, and the other end of the power supply filter capacitor C8 is directly grounded.

The second part circuit comprises an integrated circuit chip U4, a coupling capacitor C9, a power supply filter capacitor C10, a power supply filter capacitor C11 and a power supply filter capacitor C12;

the integrated circuit chip U4 is a MAX861 circuit chip and comprises an FC pin, a C + pin, a GND pin, a C-pin, a VDD pin, a/SHDN pin, a LV pin and an OUT pin; wherein:

the FC pin, the GND pin and the LV pin are all directly grounded;

one end of the coupling capacitor C9 is electrically connected with the C + pin, and the other end of the coupling capacitor C9 is electrically connected with the C-pin;

the VDD pin is connected with the/SHDN pin and is used as a VCC _5V end to be electrically connected with the first partial circuit;

the OUT pin serves as a VEE _ -5V end and is electrically connected with the-Vs pin.

In the scheme, the power supply sub-circuit generates +5V and-5V direct-current voltages which are used by the high-speed protection sub-circuit and the impedance conversion amplifying sub-circuit.

Compared with the prior art, the utility model discloses technical scheme's beneficial effect is:

the utility model provides a CMUT signal conversion circuit, make full use of current electronic components, realized the CMUT with the connection of current ultrasonic instrument with the simplified design, through simple combination of duplicating, alright realize the multichannel CMUT with the connection of ultrasonic instrument; the high-speed protection sub-circuit ensures that the high-voltage transmitting pulse signal cannot enter the impedance conversion amplification sub-circuit, and reduces the blind area of ultrasonic echo detection; the impedance conversion amplifying sub-circuit not only realizes the conversion from current to voltage, but also has the function of band-pass filtering, and can effectively filter high-frequency noise and low-frequency interference outside the interested ultrasonic range.

Drawings

Fig. 1 is a schematic diagram of the connection of the circuit module of the present invention;

FIG. 2 is a schematic diagram of the high speed protection sub-circuit connection;

FIG. 3 is a schematic diagram of the impedance transformation amplifying sub-circuit;

FIG. 4 is a schematic diagram of the first part of the power supply sub-circuit;

FIG. 5 is a schematic diagram of the second part of the power supply sub-circuit;

FIG. 6 is a graph of voltage gain measured by the circuit;

FIG. 7 is a graph of the measured phase of the circuit;

wherein: 1. a transmitting sub-circuit; 2. a high-speed protection sub-circuit; 3. an impedance conversion amplification sub-circuit; 4. a power supply sub-circuit.

Detailed Description

The drawings are for illustrative purposes only and are not to be construed as limiting the patent;

for better illustration of the present embodiment, the parameter changes of some parts in the drawings are omitted, enlarged or reduced, and do not represent the size of the actual product;

it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted.

The technical solution of the present invention will be further explained with reference to the accompanying drawings and examples.

Example 1

As shown in fig. 1, a CMUT signal converting circuit includes a transmitting sub-circuit 1, a high-speed protection sub-circuit 2, an impedance conversion amplification sub-circuit 3, and a power supply sub-circuit 4; wherein:

the output end of the transmitting sub-circuit 1 is electrically connected with the CMUT;

the synchronous signal output end of the transmitting sub-circuit 1 is in signal connection with the synchronous signal input end of the high-speed protection sub-circuit 2;

the input end of the high-speed protection sub-circuit 2 is electrically connected with the CMUT;

the output end of the high-speed protection sub-circuit 2 is electrically connected with the input end of the impedance conversion amplification sub-circuit 3;

the output end of the impedance conversion amplifying sub-circuit 3 is electrically connected with an external ultrasonic instrument;

the power supply sub-circuit 4 supplies power to the high-speed protection sub-circuit 2 and the impedance conversion amplifying sub-circuit 3.

In a specific implementation process, during the operation of the CMUT, a direct-current bias voltage is always applied to the device, and after the pulse transmitted by the transmitting sub-circuit 1 excites the CMUT to vibrate and generate ultrasonic waves, the CMUT is converted into a receiving mode; the incident ultrasonic wave vibrates the membrane of the CMUT, so that the capacitance of the device is changed, the charge changed between the CMUT electrodes is converted into a current signal under the drive of a direct current bias voltage, and the current signal passes through the high-speed protection sub-circuit 2 and then is subjected to impedance conversion and amplification by the impedance conversion amplification sub-circuit 3, so that the current signal can be connected to an external ultrasonic instrument.

Example 2

More specifically, as shown in fig. 2, on the basis of embodiment 1, the high-speed protection sub-circuit 2 includes a coupling capacitor C1, an integrated circuit chip U1, and a pull-down resistor R1; wherein:

the coupling capacitor C1 is connected in series with an SA pin of the integrated circuit chip U1 to serve as an INPUT end;

the pull-down resistor R1 is connected in series with the SB pin of the integrated circuit chip U1 and serves as a grounding end;

the integrated circuit chip U1 further comprises a GND pin, a VDD pin, a D pin, a VSS pin, an IN pin and an NC pin; wherein:

the GND pin and the VSS pin are both directly grounded;

the VDD pin is electrically connected with a 36V direct-current voltage source and serves as a V _ SW end;

the D pin is used as an ECHO end and is electrically connected with the input end of the impedance conversion amplification sub-circuit 3;

the synchronous signal TRIG of the transmitting sub-circuit 1 is sent into the high-speed protection sub-circuit 2 through the IN pin;

and the NC pin is empty.

IN the specific implementation process, a CMUT INPUT signal enters an integrated circuit chip U1 from an INPUT end through a coupling capacitor C1, a synchronous signal of high-voltage pulses of a transmitting sub-circuit 1 is sent into the integrated circuit chip U1 through an IN pin, and a V _ SW end is connected to a 36V direct-current voltage source; the synchronization signal TRIG controls the integrated circuit chip U1 to be turned off when the CMUT is transmitting and to be turned on during CMUT reception; the ECHO signal conducted through the integrated circuit chip U1 is output from the ECHO terminal of the integrated circuit chip U1 to the impedance conversion amplifier sub-circuit 2 of the next stage.

In the specific implementation process, the high-speed protection sub-circuit 2 realizes communication and isolation between the transmitting circuit and the receiving circuit. When the CMUT works, the CMUT needs to be continuously switched between a transmitting mode and a receiving mode; when the CMUT operates in a transmission mode, a high-voltage pulse signal is loaded on the CMUT electrode, and in order to prevent the high-voltage signal from damaging the low-voltage powered receiving circuit, a protection circuit capable of withstanding high voltage needs to be used for isolation. The high-speed protection sub-circuit 2 can bear the high voltage of 36V, and the isolation of the CMUT transmitting and receiving signals is realized. The high-speed protection sub-circuit 2 is opened before the transmission of the high-voltage pulse and closed after the transmission of the high-voltage pulse is finished, so that the high-voltage transmission pulse is prevented from entering the impedance conversion amplification sub-circuit 3 and causing possible damage. The switch is opened and closed for less than 315ns, can bear high voltage up to 36V, and has the on-resistance of 14.5 omega.

More specifically, the integrated circuit chip U1 is an ADG5419 circuit chip.

More specifically, as shown in fig. 3, the impedance conversion amplifying sub-circuit 3 includes an integrated circuit chip U2, a feedback resistor R2, a feedback capacitor C4, an output signal matching resistor R3, a power filter capacitor C2, a power filter capacitor C3, a power filter capacitor C5 and a power filter capacitor C6;

the integrated circuit chip U2 comprises three NC pins, a Vin-pin, a Vin + pin, a-Vs pin, a + Vs pin and a Vout pin; wherein:

the three NC pins are all empty;

the Vin-pin is used as an ECHO terminal and is electrically connected with the D pin;

the Vin + pin is directly grounded;

the-Vs pin is used as a VEE _ -5V end and is electrically connected with the power supply sub-circuit 4;

the + Vs pin is used as a VCC _5V end and is electrically connected with the power supply sub-circuit 4;

the Vout pin is connected in series with the OUTPUT signal matching resistor R3 to serve as an OUTPUT end and is electrically connected with an external ultrasonic instrument;

the feedback resistor R2 and the feedback capacitor C4 are connected in parallel, after the parallel connection, one end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the ECHO terminal, and the other end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the Vout pin;

the power supply filter capacitor C2 and the power supply filter capacitor C3 are connected in parallel, after the parallel connection, one end of the parallel connection is electrically connected with the VEE < -5 > V, and the other end of the parallel connection is directly grounded;

the power supply filter capacitor C5 and the power supply filter capacitor C6 are connected in parallel, one end of the parallel connection is electrically connected with VCC _5V, and the other end of the parallel connection is directly grounded.

In the specific implementation process, the CMUT membrane in the receiving mode vibrates under the excitation of incident ultrasonic waves, and the dc bias outputs the changed charge generation current to the impedance conversion amplification sub-circuit 3 through the high-speed protection sub-circuit 2. The impedance conversion amplification sub-circuit 3 converts a weak current into a voltage, and performs an amplified band-pass filter function. Under the device parameter configuration shown in FIG. 3, the maximum gain of the circuit is 39dB, and the 3-dB bandwidth ranges from 100kHz to 23 MHz.

More specifically, the integrated circuit chip U2 is an OPA657 circuit chip.

More specifically, the power supply sub-circuit 4 includes two parts of circuits, the first part of circuits converts the +12V dc voltage into +5V dc voltage, and is electrically connected to the VCC _5V terminal; the second part circuit converts the +5V direct-current voltage obtained by the first part circuit into a-5V direct-current voltage, and is electrically connected with the VEE _ -5V end.

More specifically, as shown in fig. 4, the first sub-circuit includes an integrated circuit chip U3, a power filter capacitor C7, and a power filter capacitor C8;

the integrated circuit chip U3 is an LM1117 circuit chip and comprises an IN pin, an OUT pin and a GND pin; wherein:

the IN pin is electrically connected with a +12V direct-current voltage to serve as a VCC _12V end;

the OUT pin serves as a VCC _5V end, outputs +5V direct-current voltage for the second part of circuits, and is electrically connected with the + Vs pin;

the GND pin is directly grounded;

one end of the power supply filter capacitor C7 is electrically connected with the VCC _12V end, and the other end is directly grounded;

one end of the power supply filter capacitor C8 is electrically connected with the VCC _5V end, and the other end of the power supply filter capacitor C8 is directly grounded.

More specifically, as shown in fig. 5, the second sub-circuit includes an integrated circuit chip U4, a coupling capacitor C9, a power filter capacitor C10, a power filter capacitor C11, and a power filter capacitor C12;

the integrated circuit chip U4 is a MAX861 circuit chip and comprises an FC pin, a C + pin, a GND pin, a C-pin, a VDD pin, a/SHDN pin, a LV pin and an OUT pin; wherein:

the FC pin, the GND pin and the LV pin are all directly grounded;

one end of the coupling capacitor C9 is electrically connected with the C + pin, and the other end of the coupling capacitor C9 is electrically connected with the C-pin;

the VDD pin is connected with the/SHDN pin and is used as a VCC _5V end to be electrically connected with the first partial circuit;

the OUT pin serves as a VEE _ -5V end and is electrically connected with the-Vs pin.

In the specific implementation process, the power supply sub-circuit 4 generates +5V and-5V direct-current voltages for use by the high-speed protection sub-circuit 2 and the impedance conversion amplification sub-circuit 3.

In the specific implementation process, as shown in fig. 6 and 7, a voltage gain graph and a phase graph measured by the circuit are obtained, and the connection between the CMUT and the existing ultrasonic instrument is realized. The connection of the multichannel CMUT and the ultrasonic instrument can be realized through simple copy combination; the high-speed protection sub-circuit 2 ensures that the high-voltage transmission pulse signal cannot enter the impedance conversion amplifying sub-circuit 3, and meanwhile, the blind area of ultrasonic echo detection is reduced; the impedance conversion amplifying sub-circuit 3 not only realizes the conversion from current to voltage, but also has the function of band-pass filtering, and can effectively filter high-frequency noise and low-frequency interference outside the interested ultrasonic range.

It is obvious that the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not limitations to the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.

Claims (8)

1. A CMUT signal conversion circuit characterized by: the high-speed protection circuit comprises a transmitting sub-circuit (1), a high-speed protection sub-circuit (2), an impedance conversion amplifying sub-circuit (3) and a power supply sub-circuit (4); wherein:

the output end of the transmitter sub-circuit (1) is electrically connected with the CMUT;

the synchronous signal output end of the transmitting sub-circuit (1) is in signal connection with the synchronous signal input end of the high-speed protection sub-circuit (2);

the input end of the high-speed protection sub-circuit (2) is electrically connected with the CMUT;

the output end of the high-speed protection sub-circuit (2) is electrically connected with the input end of the impedance conversion amplification sub-circuit (3);

the output end of the impedance conversion amplifying sub-circuit (3) is electrically connected with an external ultrasonic instrument;

and the power supply sub-circuit (4) supplies power to the high-speed protection sub-circuit (2) and the impedance conversion amplification sub-circuit (3).

2. The CMUT signal converting circuit of claim 1, wherein: the high-speed protection sub-circuit (2) comprises a coupling capacitor C1, an integrated circuit chip U1 and a pull-down resistor R1; wherein:

the coupling capacitor C1 is connected in series with an SA pin of the integrated circuit chip U1 to serve as an INPUT end;

the pull-down resistor R1 is connected in series with the SB pin of the integrated circuit chip U1 and serves as a grounding end;

the integrated circuit chip U1 further comprises a GND pin, a VDD pin, a D pin, a VSS pin, an IN pin and an NC pin; wherein:

the GND pin and the VSS pin are both directly grounded;

the VDD pin is electrically connected with a 36V direct-current voltage source and serves as a V _ SW end;

the D pin is used as an ECHO end and is electrically connected with the input end of the impedance conversion amplifier sub-circuit (3);

the synchronous signal TRIG of the transmitting sub-circuit (1) is sent into the high-speed protection sub-circuit (2) through the IN pin;

and the NC pin is empty.

3. The CMUT signal converting circuit of claim 2, wherein: the integrated circuit chip U1 is an ADG5419 circuit chip.

4. The CMUT signal converting circuit of claim 2, wherein: the impedance conversion amplifying sub-circuit (3) comprises an integrated circuit chip U2, a feedback resistor R2, a feedback capacitor C4, an output signal matching resistor R3, a power supply filter capacitor C2, a power supply filter capacitor C3, a power supply filter capacitor C5 and a power supply filter capacitor C6;

the integrated circuit chip U2 comprises three NC pins, a Vin-pin, a Vin + pin, a-Vs pin, a + Vs pin and a Vout pin; wherein:

the three NC pins are all empty;

the Vin-pin is used as an ECHO terminal and is electrically connected with the D pin;

the Vin + pin is directly grounded;

the-Vs pin is used as a VEE _ -5V end and is electrically connected with the power supply sub-circuit (4);

the + Vs pin is used as a VCC _5V end and is electrically connected with the power supply sub-circuit (4);

the Vout pin is connected in series with the OUTPUT signal matching resistor R3 to serve as an OUTPUT end and is electrically connected with an external ultrasonic instrument;

the feedback resistor R2 and the feedback capacitor C4 are connected in parallel, after the parallel connection, one end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the ECHO terminal, and the other end of the feedback resistor R2 and the feedback capacitor C4 are electrically connected with the Vout pin;

the power supply filter capacitor C2 and the power supply filter capacitor C3 are connected in parallel, after the parallel connection, one end of the parallel connection is electrically connected with the VEE < -5 > V, and the other end of the parallel connection is directly grounded;

the power supply filter capacitor C5 and the power supply filter capacitor C6 are connected in parallel, one end of the parallel connection is electrically connected with VCC _5V, and the other end of the parallel connection is directly grounded.

5. The CMUT signal conversion circuit according to claim 4, wherein: the integrated circuit chip U2 is an OPA657 circuit chip.

6. The CMUT signal conversion circuit according to claim 4, wherein: the power supply sub-circuit (4) comprises two parts of circuits, wherein the first part of circuits converts +12V direct current voltage into +5V direct current voltage and is electrically connected with the VCC _5V end; the second part circuit converts the +5V direct-current voltage obtained by the first part circuit into a-5V direct-current voltage, and is electrically connected with the VEE _ -5V end.

7. The CMUT signal conversion circuit according to claim 6, wherein: the first part circuit comprises an integrated circuit chip U3, a power supply filter capacitor C7 and a power supply filter capacitor C8;

the integrated circuit chip U3 is an LM1117 circuit chip and comprises an IN pin, an OUT pin and a GND pin; wherein:

the IN pin is electrically connected with a +12V direct-current voltage to serve as a VCC _12V end;

the OUT pin serves as a VCC _5V end, outputs +5V direct-current voltage for the second part of circuits, and is electrically connected with the + Vs pin;

the GND pin is directly grounded;

one end of the power supply filter capacitor C7 is electrically connected with the VCC _12V end, and the other end is directly grounded;

one end of the power supply filter capacitor C8 is electrically connected with the VCC _5V end, and the other end of the power supply filter capacitor C8 is directly grounded.

8. The CMUT signal converting circuit of claim 7, wherein: the second part circuit comprises an integrated circuit chip U4, a coupling capacitor C9, a power supply filter capacitor C10, a power supply filter capacitor C11 and a power supply filter capacitor C12;

the integrated circuit chip U4 is a MAX861 circuit chip and comprises an FC pin, a C + pin, a GND pin, a C-pin, a VDD pin, a/SHDN pin, a LV pin and an OUT pin; wherein:

the FC pin, the GND pin and the LV pin are all directly grounded;

one end of the coupling capacitor C9 is electrically connected with the C + pin, and the other end of the coupling capacitor C9 is electrically connected with the C-pin;

the VDD pin is connected with the/SHDN pin and is used as a VCC _5V end to be electrically connected with the first partial circuit;

the OUT pin serves as a VEE _ -5V end and is electrically connected with the-Vs pin.

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